Low Cell Dose Research Articles

Safety of Surgical Fertility Preservation Procedures in Children Prior to Hematopoietic Stem Cell Transplant

Long-term survival following hematopoietic stem cell transplant (HSCT) in childhood continues to improve, and patients are thus increasingly faced with the late effects of treatment. Infertility is very common for both males and females following HSCT and is one of the most distressing sequelae. Adoption and surrogate egg or sperm donation are possibilities for some patients, but post-HSCT reversal of gonadal failure is not possible. We have recently initiated an oncofertility program with a dedicated practitioner with specific expertise in this area. Our practice is for her to meet with all families and age-appropriate patients during the pre-HSCT evaluation period. This allows patients and families to be accurately informed about the expected treatment-related infertility risk and the available options for fertility preservation. Sperm banking and egg or embryo cryopreservation are established approaches but are not achievable for many children and adolescents. Recently, the harvesting and cryopreservation of ovarian and testicular tissue represents a novel surgical option that allows for the possibility of fertility preservation to be extended to children of all ages. The purpose of this investigation is to evaluate the safety of these procedures proximal to conditioning therapy and HSCT. This is a retrospective report on a consecutive cohort of all patients aged 0 to 25 years who, after discussion with our oncofertility specialist, chose to undergo surgical fertility preservation (laparoscopic unilateral oophorectomy or testicular biopsy) at our institution between March 2018 and April 2020. These procedures occurred under general anesthesia at the time of central line placement prior to the initiation of HSCT conditioning. We assess the safety of the procedures in terms of postoperative complications and impact on HSCT course. Twenty-two patients underwent fertility preservation surgical procedures. Thirteen patients (59%) were female, median age 13 years (1 to 22 years), and 9 (41%) were male, median age 8 years (5 to 12 years). Fourteen (63%) were prepubertal and 8 (36%) pubertal. HSCT indications were hematologic malignancies/solid tumor (40%) and nonmalignant diseases (60%). Most received an allogenic graft (68%) and 81% had myeloablative conditioning. All patients became neutropenic at a median of 10 days (0 to 51 days) from the surgical procedure; 1 was neutropenic at the time of testicular tissue cryopreservation (TTC). The mean duration for the procedures performed, including ovarian tissue cryopreservation (OTC) or TTC, was 98 minutes (49 to 260 minutes) and 97 minutes (56 to 178 minutes), respectively. Estimated blood loss was minimal and no postoperative site infections occurred. One postprocedure, blood culture-negative fever was reported without an identifiable source; the patient completed 48 hours of antibiotics with resolution of fever. Sixty-two percent of females and 56% of males started conditioning within 24 hours of OTC/TTC (15 hours to 113 days; median, 1 day). The median time to engraftment was 22 days (9 to 33 days) in females and 17 days (11 to 67 days) in males, consistent with our institutional benchmarks. One patient with aplastic anemia had primary graft failure, attributed to low cell dose. This patient engrafted after a second transplant from an alternative donor but ultimately died of multiorgan failure. He was neutropenic for over 60 days and never experienced surgical site infection. There were no procedure-related delays to start of conditioning or to discharge. Children of all ages can now be offered the possibility of fertility preservation following HSCT for benign and malignant conditions. Our review suggests that these procedure for both females and males can be performed close to the start of conditioning, which allows for coupling with central access placement. These procedures appear to be safe and do not add to transplant-related morbidity.

Outcomes of Adolescents and Young Adults Compared with Children with Acute Leukemia after Single-Unit Unrelated Cord Blood Transplantation Using Myeloablative Conditioning without Antithymocyte Globulin

Background: Although the use of cord blood transplantation (CBT) is becoming more frequent in acute leukemia, considering the relationship between the low stem cell dose and graft failure, whether use of CBT for adolescents and young adults (AYAs) is appropriate remains uncertain. Methods: A retrospective registry-based analysis of clinical outcomes and immune reconstitution was conducted for 105 AYAs and 187 children with acute leukemia who underwent single-unit CBT using myeloablative conditioning (MAC) without antithymocyte globulin (ATG). Results: Outcomes were similar between AYAs and children, except for nonrelapse mortality (NRM) and recovery rates of neutrophils and platelets. The 30-day cumulative incidence of neutrophil engraftment was similar between AYAs and children, but children had faster rates of neutrophil and platelet recovery than AYAs. The median time to neutrophil engraftment was earlier in children than in AYAs (AYAs, 19 days, 95% confidence interval [CI] 17.3–21.7; children, 16 days, 95% CI 13.1–19.5, p = 0.00003). The incidence of platelet recovery on day 120 was higher in children than in AYAs (AYAs, 80%, 95% CI 71–81%; children, 88%, 95% CI 82–92%, p = 0.037). CD34⁺ cell dose was the only independent factor influencing both neutrophil and platelet recovery. The cumulative incidence of NRM at 2 years was higher among AYAs than among children (AYAs, 27.5%, 95% CI 20–37%; children, 15%, 95% CI 10–21%, p = 0.008). Conditioning regimen was an independent factor influencing NRM. With respect to immune reconstitution, natural killer cell counts quickly recovered to normal levels 1-month post-CBT in both children and AYAs. CD8⁺ T-cell counts were higher in children than in AYAs at 1 and 3 months post-CBT. CD4⁺ T-cell counts were similar in both children and AYAs after CBT. Conclusion: AYAs with acute leukemia have outcomes of single-unit CBT using MAC without ATG that are as good as those of children. Thus, single-unit CBT using modified MAC without ATG is an acceptable choice for both AYAs and children who do not have a suitable donor.

Effect of nucleated marrow cell dose on relapse and survival in identical twin bone marrow transplants for leukemia

AbstractThe impact of cell dose (number of nucleated donor cells per kilogram recipient weight) on transplantation outcome is controversial and may differ for allogeneic and identical twin (syngeneic) bone marrow transplants. We studied the association between cell dose and outcome in 100 unmanipulated identical twin bone marrow transplantations for leukemia, reported to the International Bone Marrow Transplant Registry between 1985 and 1994, using Cox proportional hazards regression for multivariate analyses. Cell doses ranged from 0.3 to 7.4 × 108 nucleated cells/kg (median, 3.0 × 108cells/kg). Median follow-up was 75 months. Five-year cumulative incidences of transplant-related mortality with high (more than 3 × 108 cells/kg) versus low (less than or equal to 3 × 108 cells/kg) cell doses were 2% (95% confidence interval [CI], 0% to 8%) versus 10% (95% CI, 4% to 20%), respectively. Five-year probabilities of leukemia-free survival were 53% (95% CI, 39% to 67%) and 37% (95% CI, 23% to 52%), respectively. In multivariate analysis, among patients surviving in remission at least 9 months after transplantation, those receiving high cell doses were at significantly lower risk for treatment failure (relapse or death) than those receiving low cell doses (RR, 0.27; 95% CI, 0.12 to 0.6;P = .001). Lower treatment failure resulted from fewer relapses in the high cell dose group (RR for relapse, 0.28; 95% CI, 1.2 to 0.66; P = .003). These findings suggest that outcomes after syngeneic bone marrow transplantation could be improved by transplanting more than 3 × 108 nucleated cells per kilogram. The benefit of high cell dose on relapse may represent a delayed graft-versus-leukemia effect.

Use of low cell dose for unmanipulated donor lymphocyte for management of cytomegalovirus infection: A single-center experience.

Although advancements have been made in monitoring and preventing viral infections in HSCT patients, CMV reactivation still remains a critical post-transplant complication. Adoptive cell therapy is an alternative to pharmacotherapy of CMV infection in refractory patients. We retrospectively reviewed CMV infection cases after allogeneic HSCT who received U-DLI as treatment. In total, five pediatric patients between the ages of 0.5-16years that received U-DLI for a post-HSCT CMV infection were evaluated. The dose of CD3+ lymphocytes administered in DLI was 5×104 /kg, except in one patient transplanted from his sibling. One patient, who was transplanted from an unrelated donor, received U-DLI from his haploidentical mother. CMV titers dramatically reduced after U-DLI. If the availability of CMV-specific CTL is an issue, we propose that one should consider using the U-DLI therapy with low cell dose from a seropositive donor. In case the stem cell donor is seronegative and a seropositive donor is unavailable, using the U-DLI therapy from seropositive, haploidentical donors is a promising way of treatment. More studies need to be conducted to further confirm the safety and efficacy of this treatment procedure.

Temporal changes guided by mesenchymal stem cells on a 3D microgel platform enhance angiogenesis in vivo at a low-cell dose

Therapeutic factors secreted by mesenchymal stem cells (MSCs) promote angiogenesis in vivo. However, delivery of MSCs in the absence of a cytoprotective environment offers limited efficacy due to low cell retention, poor graft survival, and the nonmaintenance of a physiologically relevant dose of growth factors at the injury site. The delivery of stem cells on an extracellular matrix (ECM)-based platform alters cell behavior, including migration, proliferation, and paracrine activity, which are essential for angiogenesis. We demonstrate the biophysical and biochemical effects of preconditioning human MSCs (hMSCs) for 96 h on a three-dimensional (3D) ECM-based microgel platform. By altering the macromolecular concentration surrounding cells in the microgels, the proangiogenic phenotype of hMSCs can be tuned in a controlled manner through cell-driven changes in extracellular stiffness and "outside-in" integrin signaling. The softest microgels were tested at a low cell dose (5 × 104 cells) in a preclinical hindlimb ischemia model showing accelerated formation of new blood vessels with a reduced inflammatory response impeding progression of tissue damage. Molecular analysis revealed that several key mediators of angiogenesis were up-regulated in the low-cell-dose microgel group, providing a mechanistic insight of pathways modulated in vivo. Our research adds to current knowledge in cell-encapsulation strategies by highlighting the importance of preconditioning or priming the capacity of biomaterials through cell-material interactions. Obtaining therapeutic efficacy at a low cell dose in the microgel platform is a promising clinical route that would aid faster tissue repair and reperfusion in "no-option" patients suffering from peripheral arterial diseases, such as critical limb ischemia (CLI).

CD10/Neprilysin Enrichment in Infrapatellar Fat Pad–Derived Mesenchymal Stem Cells Under Regulatory-Compliant Conditions: Implications for Efficient Synovitis and Fat Pad Fibrosis Reversal

Background: Synovitis and infrapatellar fat pad (IFP) fibrosis participate in various conditions of the knee. Substance P (SP), a neurotransmitter secreted within those structures and historically associated with nociception, also modulates local neurogenic inflammatory and fibrotic responses. Exposure of IFP mesenchymal stem cells (IFP-MSCs) to a proinflammatory/profibrotic environment (ex vivo priming with TNFα, IFNγ, and CTGF) induces their expression of CD10/neprilysin, effectively degrading SP in vitro and in vivo. Purpose/Hypothesis: The purpose was to test the therapeutic effects of IFP-MSCs processed under regulatory-compliant protocols, comparing them side-by-side with standard fetal bovine serum (FBS)–grown cells. The hypothesis was that when processed under such protocols, IFP-MSCs do not require ex vivo priming to acquire a CD10-rich phenotype efficiently degrading SP and reversing synovitis and IFP fibrosis. Study Design: Controlled laboratory study. Methods: Human IFP-MSCs were processed in FBS or either of 2 alternative conditions—regulatory-compliant pooled human platelet lysate (hPL) and chemically reinforced medium (Ch-R)—and then subjected to proinflammatory/profibrotic priming with TNFα, IFNγ, and CTGF. Cells were assessed for in vitro proliferation, stemness, immunophenotype, differentiation potential, transcriptional and secretory profiles, and SP degradation. Based on a rat model of acute synovitis and IFP fibrosis, the in vivo efficacy of cells degrading SP plus reversing structural signs of inflammation and fibrosis was assessed. Results: When compared with FBS, IFP-MSCs processed with either hPL or Ch-R exhibited a CD10High phenotype and showed enhanced proliferation, differentiation, and immunomodulatory transcriptional and secretory profiles (amplified by priming). Both methods recapitulated and augmented the secretion of growth factors seen with FBS plus priming, with some differences between them. Functionally, in vitro SP degradation was more efficient in hPL and Ch-R, confirmed upon intra-articular injection in vivo where CD10-rich IFP-MSCs also dramatically reversed signs of synovitis and IFP fibrosis even without priming or at significantly lower cell doses. Conclusion: hPL and Ch-R formulations can effectively replace FBS plus priming to induce specific therapeutic attributes in IFP-MSCs. The resulting fine-tuned, regulatory-compliant, cell-based product has potential future utilization as a novel minimally invasive cell therapy for the treatment of synovitis and IFP fibrosis. Clinical Relevance: The therapeutic enhancement of IFP-MSCs manufactured under regulatory-compliant conditions suggests that such a strategy could accelerate the time from preclinical to clinical phases. The therapeutic efficacy obtained at lower MSC numbers than currently needed and the avoidance of cell priming for efficient results could have a significant effect on the design of clinical protocols to potentially treat conditions involving synovitis and IFP fibrosis.

CD34+ cell dose effects on clinical outcomes after T-cell replete haploidentical allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia using peripheral blood stem cells. A study from the acute leukemia working Party of the European Society for blood and marrow transplantation (EBMT).

Previous observations have reported controversial conclusions regarding cell dose and survival endpoints after allogeneic hematopoietic stem cell transplantation (HSCT). We conducted a retrospective analysis on 414 adult patients (median age 54 years, range, 18-74 years) with acute myeloid leukemia (AML) in first and second complete remission. They received a T-cell replete allogeneic HSCT from haploidentical donors, using peripheral blood stem cells, between 2006-2018. Median number of infused CD34+ was 6.58 × 106 /kg (range, 2.2-31.2 × 106 /kg). Graft-vs-host disease (GVHD) prophylaxis was post-transplant cyclophosphamide in 293 patients and anti-lymphocyte serum in 121 patients. Conditioning was myeloablative in 179 patients and reduced-intensity in 235 patients. After a median follow-up of 23.3 months (range, 12.1-41.8 months), 2-year overall survival (OS) was 64.5% (95% CI 59.3%-69.7%) with leukemia-free survival (LFS) of 57.3% (95% CI 51.8%-62.7%) and non-relapse mortality (NRM) of 23.3% (95% CI 19%-27.7%). Grades III-IV acute GVHD day+100 incidence was 14.6% while extensive chronic GVHD was 14.4% at 2-years. Thirteen (3.2%) patients experienced graft failure. We found the optimal CD34+/kg threshold defining high (n = 334) vs low cell dose (n = 80) at 4.96 × 106 . Recipients of >4.96 × 106 /kg CD34+ cells experienced less NRM (Hazard ratio [HR] 0.48; 95% CI 0.30-0.76) and prolonged LFS (HR 0.63; 95% CI 0.43-0.91) and OS (HR 0.60; 95% CI 0.40-0.88) compared to those in the lower cell dose cohort. Larger cohort studies are needed to confirm these findings.

Outcomes and Challenges of Manufacturing Virus-Specific Cytotoxic T-lymphocytes Using IFN-gamma Cytokine Capture System

Background & Aim Background Viral infection/reactivation after allogeneic hematopoietic stem cell (HSCT) or solid organ transplant (SOT) is a significant cause of morbidity and mortality in drug-refractory patients. Adoptive transfer of allogeneic virus-specific cytotoxic T lymphocytes (vCTLs) can rapidly restore antiviral T cell immunity. The IFN-gamma Cytokine Capture System (CCS, Miltenyi) provides a fast and automated method of isolating vCTLs by stimulating them with virus-specific peptides. Aim To evaluate the safety and efficacy of vCTLs manufactured using IFN-gamma CCS on CliniMACS Prodigy® in children and young adults (CAYA) and highlight technical aspects of vCTL manufacturing by this method. Methods, Results & Conclusion Methods CAYA HSCT or SOT recipients with refractory viral infections (CMV, ADV, EBV, BK) received adoptive transfer of vCTLs from haploidentical relatives or matched donors who screened positive for the relevant vCTL. Following non-mobilized leukocytapheresis, virus-specific CD4+ and CD8+ T cells were isolated using IFN-gamma CCS on CliniMACS Prodigy®. Results Fourteen patients have been treated to date (Table 1). Of patients treated for CMV, EBV, ADV, or their combination, 100% (9) achieved complete remission (CR). 2 out of 4 patients treated for BK achieved CR, 2 had partial remission (PR), and one patient treated for CMV/BK had resolution of CMV and no response (NR) to BK. There were no episodes of acute Grade II-IV GVHD, chronic GVHD, CRS, or infusion reactions. We noted occasional discordance between donor viral serology and their response to the stimulation by the viral Peptivator; for example, we successfully manufactured anti-ADV vCTLs from a donor who was serologically negative to adenovirus. Flow cytometry analysis of rare events in a limited sample required sequential gating strategy to maximally reduce background noise. Products thus manufactured have unique properties, such as low cell dose and high debris content, which may face additional regulatory scrutiny. Conclusion Despite its unique challenges, vCTL manufacturing is rapid, reproducible and effective, and vCTLs are safe and well tolerated in CAYA with HSCT and SOT.

Important considerations for cell therapy manufacturing of mesenchymal stem cell

Background & Aim Recent advances in cell therapy manufacturing, e.g. microcarrier-based 3D culture and perfusion, have paved the way for cost-effective large-scale expansion of mesenchymal stem cells (MSCs). In particular, perfusion and enhanced feed boosts allow the culture to reach increasingly high cell densities. Although the high cell density is favorable to customers due to the low cost and high cell dose requirements, we should not overlook its impact on cell quality. Here, we studied the correlation between 3D culture cell density with a variety of commonly used cell quality parameters for both fresh and post-thaw cells. Methods, Results & Conclusion MSC 3D cultures were carried out using different microcarriers (Cultispher-G, dissolvable Corning Synthemax, and Pall SoloHill collagen) and media in spinner flasks and stirred-tank bioreactors. MSCs were able to expand on all microcarriers (Figure1), reaching a final density of 0.6 to 1 million cells/mL. Attachment and proliferation capacities of 3D-expanded MSCs, harvested at different cell densities, were assessed by culturing them post-harvest on 2D flatware. Figure2 shows that MSCs harvested at low cell densities (day4) proliferated significantly higher than MSCs harvested at high cell densities (day5-8). Similar pattern was observed for 3D-cultured MSCs post-thaw. Cell viability was also evaluated for both fresh and post-thaw MSCs harvested at low and high cell densities. For most cases, MSCs harvested at both low and high cell densities, showed above 90% viability over 0-6 hours (Figure3). MSCs expanded using SoloHill microcarriers displayed >90% post-thaw viability for both low and high cell densities. However, dissolvable Corning-Synthemax exhibited up to 12% and 30% drops, and Cultispher-G up to 24% and 51% drops for low and high cell density groups, respectively. Figure3 also shows that the extent of decline in post-thaw vibility was higher for MSCs harvested at high cell densities versus low cell densities. In conclusions, our findings indicated that the extended 3D culture (i.e. harvesting at higher cell densities) led to compromising attachment and proliferation capacities of MSCs, regardless of the choice of microcarrier. For Cultispher-G and dissolvable Coning-Synthemax, we observed 20-30% lower cell viabilities for MSCs harvested at high densities compared to low densities.

Effect of Allogeneic Cell-Based Tissue-Engineered Treatments in a Sheep Osteonecrosis Model.

Osteonecrosis of the femoral head (ONFH) is defined as a tissue disorder and successive subchondral bone collapse resulting from an ischemic process, which may progress to hip osteoarthritis. Cell therapy with multipotent bone marrow mesenchymal stromal cells (BM-MSC) of autologous origin appears to be safe and has shown regenerative potential in previous preclinical and clinical studies. The use of allogeneic cells is far more challenging, but may be a promising alternative to use of autologous cells. Moreover, an optimized dosage of cells from an allogeneic source is needed to obtain off-the-shelf tissue engineering products (TEPs). The purpose of this study was to evaluate the efficacy of a TEP composed of undifferentiated ex vivo expanded BM-MSC of allogeneic origin, combined with bone matrix particles in variable doses. A comparative analysis of TEP's bone regenerative properties against its autologous counterpart was performed in an early-stage ONFH preclinical model in mature sheep. Allogeneic BM-MSC groups demonstrated bone regeneration capacity in osteonecrotic lesions equivalent to autologous BM-MSC groups 6 weeks after treatment. Likewise, stimulation of bone regeneration by a low cell dose of 0.5 × 106 BM-MSC/cm3 was equivalent to that of a high cell dose, 5 × 106 BM-MSC/cm3. Neither local nor systemic immunological reactions nor tumorigenesis were reported, strengthening the safety profile of allogeneic BM-MSC therapy in this model. Our results suggest that low-dose allogeneic BM-MSC is sufficient to promote bone regeneration in femoral head osteonecrotic lesions, and should be considered in translation of new allogeneic cell-based TEPs to human clinics. Impact statement Cell therapy and tissue engineering hold promise as novel regenerative therapies for musculoskeletal diseases, and particularly in bone regeneration strategies. In this article, we report the evaluation of the efficacy of an allogeneic cell-based tissue engineering product (TEP) in an early-stage osteonecrosis of the femoral head preclinical model in skeletally mature sheep. Moreover, we demonstrate its bone regeneration capacity and safety in vivo and its equivalence to autologous counterparts. These findings have important implications for the translation of new allogeneic cell-based TEPs to human clinics.

Mgta-456, a Cell Therapy Utilizing Expansion of CD34+ Hematopoietic Stem Cells (HSC), Improves HLA Matching for Adult Recipients, Promotes Faster Hematopoietic Recovery and Enables Uniform Engraftment with Less Acute Graft-Vs-Host Disease (GVHD)

<h3>Background</h3> HSC dose and HLA match are risk factors that impact mortality using cord blood units (CBU) in transplant. Low CD34+ doses result in prolonged cytopenia and higher graft failure risk. A minimum cell dose of 3.0 × 10⁷ total nucleated cells (TNC)/kg has generally been required in CBU selection; however, cell dose limits often require the use of a 2^nd unit and markedly limits the availability of 7-8/8 HLA-matched units in larger patients. MGTA-456 is a cell therapy product utilizing an aryl hydrocarbon receptor antagonist for expansion of CD34+ HSCs <i>in vitro</i>. In prior studies with fresh MGTA-456, 36 patients with hematologic malignancies demonstrated rapid neutrophil recovery and 100% engraftment. This study (NCT03674411) will evaluate the safety and efficacy of cryopreserved MGTA-456 and the effectiveness of lowering the TNC threshold of the selected CBU to 1.0 × 10⁷ TNC/kg before expansion to improve HLA match. <h3>Methods</h3> 13 patients aged 2-47 years (12-159 kg) with high-risk hematologic malignancy were enrolled with 11 transplanted to date. Patients received cyclophosphamide 120 mg/kg, fludarabine 75 mg/m2 and total body irradiation 1320 cGy or a busulfan-based regimen for children ≤3 years of age prior to MGTA-456 with cyclosporine/mycophenolate mofetil prophylaxis. G-CSF began the day after infusion until the neutrophil count exceeded 2500/uL for 3 days. <h3>Results</h3> MGTA-456 contained a median 2.3 × 10⁹ CD34+ cells (range, 0.65-8.0) after expansion (422-fold expansion of CD34+ cells [range, 219-1313]). Neutrophil recovery occurred in all patients with a median of 15 days (range, 0-31), similar to recipients of fresh MGTA-456 in a prior study (median 14 days) and significantly faster than in recipients of unmodified CBUs (median 25 days). Median platelet recovery was 41 days (range 24-49) vs 64 days with unmodified CBUs. MGTA-456 CD34+CD90+ content strongly correlated with speed of neutrophil recovery (Fig. 1), consistent with preclinical murine data showing CD34+CD90+ cells represent the true engraftable HSC population. Lowering the TNC requirement to 1.0 × 10⁷ TNC/kg for CBU selection pre-expansion improved HLA match and/or eliminated the need for double CBU transplant in all 5 patients weighing >80 kg. Three patients received 8/8 grafts who would have otherwise received 1 or 2 6/8 units (n=2) or two 7/8 units (n=1) which may account for the low incidence of aGVHD overall (3 cases of Grade 1-2 and no Grade 3-4). With a follow-up of 5.2 months (0.4-8.5 months), all patients are alive. <h3>Conclusion</h3> Cryopreserved MGTA-456 cell therapy resulted in rapid and 100% engraftment with speed of neutrophil recovery correlating with CD34+CD90+ cell dose in patients with high risk hematologic malignancy. Expansion of smaller CBUs increases the chance of finding a better HLA match, particularly for adults, thus reducing the barriers associated with low cell dose and poor HLA match in CBU transplantation.

High Dose Hematopoietic Stem Cell Transplantation Leads to Rapid Neural and Peripheral Disease Cross-Correction Via Robust Hematopoietic and Microglia Recovery

Background Allogeneic hematopoietic stem cell transplant (HSCT) is a curative approach to halt disease progression of select inherited metabolic disorders (IMDs). For IMDs that affect the central nervous system (CNS), donor-derived cells, like microglia, cross-correct defects via production of normal enzyme. The typical cell dose used in HSCT can be sub-optimal and, in gene therapy applications, copy number has been shown to be variable. We developed MGTA-456, a high dose cell therapy that led to rapid neutrophil recovery and 100% engraftment in patients with malignant and non-malignant diseases (Wagner et al Blood 2017; Orchard et al AAN 2019). The impact of cell dose on disease correction, however, is unknown. Here, we show that fast and robust hematopoietic and microglia recovery via high cell dose therapies, like MGTA-456, leads to rapid and complete disease resolution of Hurler syndrome through hematopoietic engraftment in the CNS. Results At 1-16 weeks post-HSCT, transplant of increasing doses of total bone marrow cells following myeloablative busulfan conditioning led to a dose-dependent increase microglial engraftment (26-fold for 10 × 106 cells vs 0.3 × 106 cells, p Relative to low cell dose therapies, transplant of MGTA-456, a high cell dose therapy with two normal IDUA gene copies, led to robust, long-term immune recovery (n=88 animals), 60-fold greater microglial engraftment as early as 2 weeks post-HSCT (Figure D, p 600-fold higher IDUA enzyme levels (Figure E, p Conclusions We show that high dose HSCT leads to improved disease correction, including normalization of behavioral outcomes, via robust engraftment. High dose cell therapies, like MGTA-456, may rapidly and durably resolve peripheral and neurologic disease in patients with IMDs and other neurodegenerative diseases caused by defective microglia.

Review: Biomimetic nanofibers in the ex vivo expansion of cord blood-derived hematopoietic stem cells

This review summarizes current strategies in the development of advanced nanofibrous polymer-based scaffolds via electrospinning, their applications in mimicking the extracellular matrix, and the use of polymer nanofibers to deliver growth factors or small molecules for ex vivo expansion of HSCs. Hematopoietic stem cell (HSC) transplantation has become the standard of care for patients with hematologic cancers, anemia, and a variety of other malignant and non-malignant disorders. Although mobilized peripheral blood (MPB) has become a preferred source of HSCs for transplants, bone marrow (BM) and umbilical cord blood (UCB) are also frequently utilized. Regardless of source, Regardless of source, HSC transplantation suffers from low cell doses. Therefore, methods to increase the cell dose while maintaining the progenitor phenotype, especially the CD34+ progenitor cells, would have a significant clinical impact. Ex vivo expansion of HSCs prior to transplantation is one approach that offers tremendous promise for increasing cell doses and improving clinical outcomes. Many ex vivo strategies have been developed within the last decade in order to address the issue of low cell dose, with more or less success, mainly determined by the degree of difficulty related with maintaining HSCs self-renewal and stemness properties after long-term expansion. Here, we report the current progress of nanofibrous scaffolds for the ex vivo expansion of hematopoietic stem cells (HSCs). In this review, we present the technique of electrospinning for nanofibrous scaffolds, focusing mainly on preparation methods, materials (synthetic, natural, and hybrid polymers), and surface-structural modifications. The variables of nanofiber processing parameters and its impact on the nanofiber assembly is reported as well as the effect of the solution parameters on the structural morphology of the fabricated nanofibers. Critical features of fabricated nanofibers such as porous structure and high specific surface area are addressed, but more importantly the necessity of mimicking the intrinsic properties of the native in vivo microenvironment of the extracellular matrix (ECM). Researchers have been largely successful in replicating the diverse nature of the ECM through the incorporation of small molecules, growth factors, and signaling molecules into 3D scaffolds to generate biomimetic hierarchical structures. Harnessing the potential of the stem cell niche forms the basis of clinical therapy in the ex vivo expansion of cord blood-derived hematopoietic stem cells. As reviewed in this article, advances in nanofiber ex vivo approaches based upon emerging biomaterials opens new doors for artificial niches. Scientific evidence provided in this review verifies that the nanofiber niche provides an ideal mimic of the physical microenvironment of HSCs thereby offering great potential for clinical applications.

High Dose Hematopoietic Stem Cell Transplantation Leads to Rapid Hematopoietic and Microglia Recovery and Disease Correction in a Mouse Model of Hurler Syndrome

Background . Allogeneic hematopoietic stem cell transplant (HSCT) is a promising approach to halt disease progression and prevent or ameliorate neurological symptoms arising from select inherited metabolic disorders (IMDs). Donor-derived cells, including microglia, limit disease progression post-HSCT via production of normal enzyme in a process called cross-correction. A standard cell dose used in HSCT is sub-optimal, resulting in delayed hematopoietic recovery and slower correction of central nervous system (CNS) defects (Lund et al BBMT 2019). To address these limitations, we developed MGTA-456, a cell therapy that contains large numbers of CD34+ cells and has led to accelerated neutrophil recovery and 100% engraftment post-HSCT in patients with malignant and non-malignant diseases (Wagner et al Blood 2017; Orchard et al AAN 2019). We previously showed that MGTA-456 leads to faster hematopoietic and microglia recovery in the brains of NSG mice (Goncalves et al AAN 2019); however, the impact of cell dose on disease outcomes and mechanism of cross-correction are unknown. Here, we show that faster and greater hematopoietic and microglia recovery leads to rapid and complete resolution of disease endpoints in a mouse model of mucopolysaccharidosis I (Hurler syndrome) and that, mechanistically, donor engraftment in the brain is required for disease cross-correction. Results . To determine whether cell dose impacts microglial engraftment, CD45.2 mice were conditioned with a clinically-relevant, myeloablative dose of busulfan and transplanted with increasing doses of CD45.1 bone marrow cells, beginning with 0.3x106 cells/mouse (2x106 cells/kg) based on allometric scaling to model high dose cell therapies. A dose-dependent increase in microglia was observed as early as 1 week post-HSCT, where 10x106 cells led to a 26-fold higher number of donor microglia compared to 0.3x106 cells (p&lt;0.01), an effect that was sustained through 16 weeks post-HSCT (p&lt;0.001). Despite high donor chimerism in the periphery at all cell doses (75-99%), only partial chimerism was observed in the brain. At 16 weeks, donor microglia represented only 2% of microglia after transplant of 0.3x106 cells but this was increased to 35% of total microglia in the brain following transplant of 10x106 cells. These data indicate that while busulfan can facilitate a low level of microglia engraftment, this effect can be enhanced by transplant of high cell doses. To evaluate the impact of cell dose on disease outcomes, we transplanted a low (0.3x106) or high (10x106) cell dose of wild-type bone marrow cells into busulfan-conditioned Idua-/- mice, a model of Hurler syndrome. At 1 month post-HSCT, peripheral donor myeloid chimerism was &gt;75% and &gt;99% for 0.3x106 and 10x106 cells, respectively. In the brain, transplant of 10x106 cells led to significantly higher donor microglial engraftment versus 0.3x106 cells (Figure A). Notably, high cell dose resulted in significantly higher levels of IDUA enzyme in the brain (Figure B), reduced levels of β-hexosaminidase and glycosaminoglycan (GAG) substrate, and normalization of behavioral outcomes, including rotarod performance, to wild type levels (Figure C). In peripheral tissues, transplant of 10x106 cells, but not 0.3x106 cells, led to a reduction of GAGs to wild type levels as early as 1 week post-HSCT (p&lt;0.01). To determine if donor engraftment in the brain is required for cross-correction, we transplanted 10x106 cells into mice conditioned with a myeloablative dose of treosulfan, which is not sufficient to condition the brain for microglia engraftment. Treosulfan conditioning, followed by high dose HSCT, led to &gt;99% donor myeloid chimerism in the periphery but neither increased microglial levels nor corrected CNS defects (Figures A-C), suggesting that donor engraftment in the brain is required for disease modification. Long-term outcomes and impact on skeletal phenotype in this model will also be presented. Conclusions . We demonstrate that high dose HSCT leads to robust microglia engraftment in the brain and improved disease endpoints. These data suggest that strategies to increase cell dose, such as MGTA-456, may accelerate resolution of neurologic disease in patients with IMDs. Similar approaches, possibly coupled with gene modification technologies, could be used to improve microglial function in other neurodegenerative diseases where defective microglia have been implicated. Disclosures Goncalves: Magenta Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties. Hyzy:Magenta Therapeutics: Employment, Equity Ownership. Brooks:Magenta Therapeutics: Employment, Equity Ownership. Boitano:Magenta Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties. Cooke:Magenta Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties.

Comparison of Outcomes between HSCT Donor Sources for Pediatric Patients with Hematologic Malignancies

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for pediatric patients with hematologic malignancies. Historically, matched sibling donors (MSD) have been the preferred donor source given ease of availability and lower rates of graft-versus-host-disease (GVHD). However, only 30% of patients have a MSD and relapse rates are high after MSD HSCT, raising the question of best donor choice. As conditioning regimens evolve, GVHD management improves and supportive care advances, it is important to evaluate the role of donor source on short and long-term clinical outcomes to inform donor selection. We performed a single-center retrospective analysis comparing post-HSCT outcomes in a cohort of pediatric patients undergoing MSD, matched unrelated donor (MUD), and umbilical cord blood (CB) transplants from 2006 to 2018. Methods: A retrospective analysis was performed on an IRB-approved protocol through Fred Hutchinson Cancer Research Center. 232 patients were included who received MSD (n=56), MUD (n=89) or CB (n=87) transplants. Of note, 24 CB patients received expanded CB cells in addition to unmanipulated unit(s). GVHD prophylaxis in all patients consisted of a calcineurin inhibitor and MMF or methotrexate. The vast majority received a high-intensity conditioning regimen (86%, 96%, and 82% respectively for MSD, MUD and CB). Overall survival (OS) and disease-free survival (DFS) were evaluated using the Kaplan-Meier method. Probabilities of non-relapse mortality (NRM), relapse, and acute GVHD were evaluated using cumulative incidence (CI) estimates with appropriate competing risks. The Cox regression model was used for adjusted analysis for age, year of transplant, sex, CMV status, MRD status, disease risk, and conditioning regimen. Results: Patient/treatment/donor demographics are shown in Table 1. Median follow-up was 2.6, 3.7 and 3.1 years for MSD, MUD and CB respectively. Patient diagnosis, disease risk, gender, age, and CMV serology were balanced between groups. CI of engraftment was similar as well, with only one graft failure in the MUD group (Fig 1). Median time to platelet recovery was significantly faster in MUD and MSD groups as compared to the CB group (p&lt;0.0001; p&lt;0.0001). There was no difference in unadjusted 5 year OS (Fig 2) and NRM (Fig 3) between groups. Five-year DFS was significantly higher in CB v. MSD (71% v. 54%, p=0.03) but not between CB v. MUD (71% v. 61%, p=0.18) or between MSD and MUD (p=0.38) (Fig 4). The CI of relapse at 5 years was 20% for CB patients, significantly lower than that of MSD recipients (49%, p=0.003) and not different from MUD (32%, p=0.11) (Fig 5). After adjusted analysis, the risk of DFS failures was higher among recipients of MSD than CB [HR: 1.88 (CI 95%: 1.01-3.47), p=0.04]. When CB versus MUD groups were compared, there was a trend of higher risk of DFS failures in the MUD group [HR: 1.28 (CI 95%: 0.96-1.66), p=0.09]. No difference was observed in risk of DFS failures between MSD versus MUD groups [HR:0.77 (CI 95%: 0.44-1.4), p=0.43]. Incidence of grade II-IV acute GVHD was 90% (95%CI: 82-95%), 75% (95%CI: 61-84%) and 88% (95%CI: 80-94%), for CB, MSD and MUD, respectively (p=0.25). Incidence of grade III-IV acute GVHD was 33% (95%CI: 23-43%) for CB, 9% (95%CI: 3-18%) for MSD, and 11% (95%CI: 5-18%) for MUD. Incidence of grade III-IV was significantly higher for the CB group compared to the other groups (p=0.001); however, nearly 60% of CB recipients with grade III-IV acute GVHD were diagnosed before engraftment had occurred and in retrospect met criteria for pre-engraftment syndrome. Among surviving patients, 23 CB recipients developed chronic GVHD (26% - 15 mild, 4 moderate, 4 severe) as compared to 14 MSD patients (25% - 13 mild, 1 moderate) and 40 MUD patients (45% - 27 mild, 11 moderate, 2 severe). Conclusions: Our data demonstrate no difference in unadjusted OS between MSD, MUD and CB recipients. Importantly, despite this equivalence, 5-year DFS was significantly better in the CB v. MSD group, reflecting the lower relapse rate observed in CB patients and seen previously by us and others. CB continues to be viewed as an "alternative" donor for HSCT due to the low stem cell dose in a CB graft resulting in delayed neutrophil recovery, primary graft failure and increased NRM. However, this was not observed herein, supporting the use of CB for pediatric HSCT perhaps especially in patients at high risk of post-transplant relapse. Disclosures Milano: ExCellThera: Research Funding; Amgen: Research Funding. Delaney:Nohla Therapeutics: Employment, Equity Ownership; Biolife Solutions: Membership on an entity's Board of Directors or advisory committees. Bleakley:HighPass Biotherapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents &amp; Royalties, Research Funding.

Low Lymphocyte Count at Day 30 after Single Cord Blood Transplantation Had Negative Impact on Survival, Because of Higher NRM Rate

&amp;lt;Introduction&amp;gt; Delayed immune reconstitution after allogeneic transplantation increases the risk of treatment-related mortality, and chronic GVHD. Previous reports showed that absolute lymphocyte count at day 30 (ALC30) was a significant prognostic factor of transplantation, and lower numbers of total CD4+ T cells and naïve CD4+ T cells in particular were associated significantly with higher mortality. However, there is little knowledge about the factors associated with low lymphocyte recovery, especially in cord blood transplantation (CBT). The cut-off value of lymphocyte recovery for statistical significance has not been determined yet. &amp;lt;Methods&amp;gt; We retrospectively analyzed the outcome of 579 consecutive patients who underwent single cord blood transplantation (CBT) for the first time at Toranomon Hospital between January 2011 and 2018. Patients with active infection at transplantation (n=40), in poor ECOG PS (3 or more) (n=36), or lacked information about CT before CBT (n=1) were excluded from this study. &amp;lt;Results&amp;gt; Five hundred and two patients (n=317 male; n=185 female) were included in this study. The median age at transplantation was 57 years (range, 16-77), with a median HCT-CI score of 2 (0-10). Underlying diseases were AML (307), MDS (43), MPN (20), ALL (50), mature lymphoid malignancies (54), and others (28). Median spleen index (SI) before transplantation was 60.2 (16.5-319.7). Three hundred and ninety eight patients (79%) were not in remission at transplant. MAC regimens were selected in 400 (80%). TAC alone was used in 132 (26%) as GVHD prophylaxis. Median number of TNC and CD34+ cells infused were 2.62 (1.57-6.85) x 107/kg and 0.86 (0.29-3.77) x 105/kg, respectively. 194 (39%) were positive for anti-HLA antibodies, but none had donor-specific. With a median follow-up of 32 (range, 3-99) months, cumulative incidence of neutrophil engraftment (NE), the 3-year probabilities of overall survival (OS), relapse rate (RR) and non-relapse mortality (NRM) for entire population were 92.8%, 40.6%, 23.5%, and 35.3%, respectively. Underlying disease (myeloid malignancy), disease status at SCT (non-CR), poor PS (PS=2), GVHD prophylaxis (TAC+MMF), low CD34-positive cell dose (&amp;lt;0.8 x 105/kg), and splenomegary (SI ≥ 40) were significantly associated with inferior NE in multivariate analysis. Disease status at SCT (non-CR), poor PS (PS=2), Higher HCT-CI (PS ≥ 3), and GVHD prophylaxis (TAC+MMF) were significantly associated with higher NRM in multivariate analysis. We analyzed the relationship between ALC30 and transplantation outcome. Median number of ALC30 was 231 (3.5-1503), and the 25th percentile was 144. We divided the cohort into two groups, ALC30 low group (&amp;lt;150, n=123), ALC30 high group (≥150, n=346). High number of ALC30 (≥150) was associated with better survival (48.1% vs. 29.5%, p &amp;lt; 0.01) and lower NRM (26.9% vs. 41.9%, p &amp;lt; 0.01) due to reduced incidence of lethal infection (7.1% and 23.4% of total death in ALC30 high and low, respectively, p &amp;lt; 0.01), but was not associated with RR (25.5% vs. 25.1%, p = 0.59). High ALC30 (≥150), as well as younger age (&amp;lt;60), underlying disease (myeloid malignancy), better PS (0-1), and disease status at SCT (CR) showed a superior OS in multivariate analysis. We then assessed factors associated with ALC30, and higher infused dose of CD34-positive cells was the only factor associated with high ALC30, (p=0.03, t-test). Other factors, such as infused TNC dose, type of conditioning, or GVHD prophylaxis did not show significant association with ALC30. &amp;lt;Conclusion&amp;gt; This retrospective study demonstrated that low ALC30 after CBT had negative impact on survival because of higher NRM rate. High CD34-positive cell dose was the only factor associated with high ALC30. Not CD34-positive cell dose, but ALC30 had significant impact on OS in multivariate analysis, so we need to take lymphocyte recovery into account, in an attempt to improve transplantation outcome. Figure Disclosures No relevant conflicts of interest to declare.

Clinical Protocol to Prevent Thrombogenic Effect of Liver-Derived Mesenchymal Cells for Cell-Based Therapies.

The efficacy of mesenchymal stem cell infusion is currently tested in numerous clinical trials. However, therapy-induced thrombotic consequences have been reported in several patients. The aim of this study was to optimize protocols for heterologous human adult liver-derived progenitor cell (HHALPC) infusion, in order to eliminate acute thrombogenesis in liver-based metabolic or acute decompensated cirrhotic (ADC) patients. In rats, thrombotic effects were absent when HHALPCs were infused at low cell dose (5 × 106 cells/kg), or at high cell dose (5 × 107 cells/kg) when combined with anticoagulants. When HHALPCs were exposed to human blood in a whole blood perfusion assay, blocking of the tissue factor (TF) coagulation pathway suppressed fibrin generation and platelet activation. In a Chandler tubing loop model, HHALPCs induced less explosive activation of coagulation with blood from ADC patients, when compared to blood from healthy controls, without alterations in coagulation factor levels other than fibrinogen. These studies confirm a link between TF and thrombogenesis, when TF-expressing cells are exposed to human blood. This phenomenon however, could be controlled using either a low, or a high cell dose combined with anticoagulants. In clinical practice, this points to the suitability of a low HHALPC dose infusion to cirrhotic patients, provided that platelet and fibrinogen levels are monitored.

Low metformin causes a more oxidized mitochondrial NADH/NAD redox state in hepatocytes and inhibits gluconeogenesis by a redox-independent mechanism

The mechanisms by which metformin (dimethylbiguanide) inhibits hepatic gluconeogenesis at concentrations relevant for type 2 diabetes therapy remain debated. Two proposed mechanisms are 1) inhibition of mitochondrial Complex 1 with consequent compromised ATP and AMP homeostasis or 2) inhibition of mitochondrial glycerophosphate dehydrogenase (mGPDH) and thereby attenuated transfer of reducing equivalents from the cytoplasm to mitochondria, resulting in a raised lactate/pyruvate ratio and redox-dependent inhibition of gluconeogenesis from reduced but not oxidized substrates. Here, we show that metformin has a biphasic effect on the mitochondrial NADH/NAD redox state in mouse hepatocytes. A low cell dose of metformin (therapeutic equivalent: <2 nmol/mg) caused a more oxidized mitochondrial NADH/NAD state and an increase in lactate/pyruvate ratio, whereas a higher metformin dose (≥5 nmol/mg) caused a more reduced mitochondrial NADH/NAD state similar to Complex 1 inhibition by rotenone. The low metformin dose inhibited gluconeogenesis from both oxidized (dihydroxyacetone) and reduced (xylitol) substrates by preferential partitioning of substrate toward glycolysis by a redox-independent mechanism that is best explained by allosteric regulation at phosphofructokinase-1 (PFK1) and/or fructose 1,6-bisphosphatase (FBP1) in association with a decrease in cell glycerol 3-phosphate, an inhibitor of PFK1, rather than by inhibition of transfer of reducing equivalents. We conclude that at a low pharmacological load, the metformin effects on the lactate/pyruvate ratio and glucose production are explained by attenuation of transmitochondrial electrogenic transport mechanisms with consequent compromised malate-aspartate shuttle and changes in allosteric effectors of PFK1 and FBP1.

The Prognostic Impact of Pretransplantation Inflammatory and Nutritional Status in Adult Patients after Myeloablative Single Cord Blood Transplantation

Markers of inflammatory and nutritional status, such as the Controlling Nutritional Status (CONUT) score, Prognostic Nutritional Index, Glasgow Prognostic Score, and C-reactive protein-albumin ratio (CAR) has been demonstrated to be associated with poor prognosis in patients with various cancers. Although the relatively low cell dose of a single cord blood unit restricts the indication for cord blood transplantation (CBT) to pediatric and relatively smaller and lighter adult patients, the impact of malnutrition on outcomes after CBT is unclear. We retrospectively analyzed 165 adult patients who underwent myeloablative single-unit CBT in our institute. In multivariate analysis, a higher CONUT score, which is indicative of poor inflammatory and nutritional status, was significantly associated with poor outcomes, including low neutrophil engraftment and development of extensive chronic graft-versus-host disease. A higher CAR, which is also suggestive of poor inflammatory and nutritional status, was significantly associated with poor neutrophil engraftment and higher overall mortality. Body mass index (BMI) was not associated with transplantation outcomes. These data suggest that poor pretransplantation inflammatory and nutritional status might be a more practical parameter than lower BMI, for predicting transplantation outcomes after single CBT for adults.

Use of psychotropic medication among adolescents and adults with autism spectrum disorders

Long-term survival following hematopoietic stem cell transplant (HSCT) in childhood continues to improve, and patients are thus increasingly faced with the late effects of treatment. Infertility is very common for both males and females following HSCT and is one of the most distressing sequelae. Adoption and surrogate egg or sperm donation are possibilities for some patients, but post-HSCT reversal of gonadal failure is not possible. We have recently initiated an oncofertility program with a dedicated practitioner with specific expertise in this area. Our practice is for her to meet with all families and age-appropriate patients during the pre-HSCT evaluation period. This allows patients and families to be accurately informed about the expected treatment-related infertility risk and the available options for fertility preservation. Sperm banking and egg or embryo cryopreservation are established approaches but are not achievable for many children and adolescents. Recently, the harvesting and cryopreservation of ovarian and testicular tissue represents a novel surgical option that allows for the possibility of fertility preservation to be extended to children of all ages. The purpose of this investigation is to evaluate the safety of these procedures proximal to conditioning therapy and HSCT. This is a retrospective report on a consecutive cohort of all patients aged 0 to 25 years who, after discussion with our oncofertility specialist, chose to undergo surgical fertility preservation (laparoscopic unilateral oophorectomy or testicular biopsy) at our institution between March 2018 and April 2020. These procedures occurred under general anesthesia at the time of central line placement prior to the initiation of HSCT conditioning. We assess the safety of the procedures in terms of postoperative complications and impact on HSCT course. Twenty-two patients underwent fertility preservation surgical procedures. Thirteen patients (59%) were female, median age 13 years (1 to 22 years), and 9 (41%) were male, median age 8 years (5 to 12 years). Fourteen (63%) were prepubertal and 8 (36%) pubertal. HSCT indications were hematologic malignancies/solid tumor (40%) and nonmalignant diseases (60%). Most received an allogenic graft (68%) and 81% had myeloablative conditioning. All patients became neutropenic at a median of 10 days (0 to 51 days) from the surgical procedure; 1 was neutropenic at the time of testicular tissue cryopreservation (TTC). The mean duration for the procedures performed, including ovarian tissue cryopreservation (OTC) or TTC, was 98 minutes (49 to 260 minutes) and 97 minutes (56 to 178 minutes), respectively. Estimated blood loss was minimal and no postoperative site infections occurred. One postprocedure, blood culture-negative fever was reported without an identifiable source; the patient completed 48 hours of antibiotics with resolution of fever. Sixty-two percent of females and 56% of males started conditioning within 24 hours of OTC/TTC (15 hours to 113 days; median, 1 day). The median time to engraftment was 22 days (9 to 33 days) in females and 17 days (11 to 67 days) in males, consistent with our institutional benchmarks. One patient with aplastic anemia had primary graft failure, attributed to low cell dose. This patient engrafted after a second transplant from an alternative donor but ultimately died of multiorgan failure. He was neutropenic for over 60 days and never experienced surgical site infection. There were no procedure-related delays to start of conditioning or to discharge. Children of all ages can now be offered the possibility of fertility preservation following HSCT for benign and malignant conditions. Our review suggests that these procedure for both females and males can be performed close to the start of conditioning, which allows for coupling with central access placement. These procedures appear to be safe and do not add to transplant-related morbidity.