Human Peripheral Blood Stem Cells Research Articles

Long-Term Cryopreservation of Peripheral Blood Stem Cell Harvest Using Low Concentration (4.35%) Dimethyl Sulfoxide with Methyl Cellulose and Uncontrolled Rate Freezing at -80 °C: An Effective Option in Resource-Limited Settings

Long-term cryopreservation of peripheral blood stem cells (PBSCs) is highly useful in the setting of tandem/multiple transplantations or treatment of relapse in the autologous hematopoietic stem cell transplantation (HSCT) setting. Even in allogeneic HSCT, donor lymphocyte infusions may be stored for months to years if excess stem cells are collected from donors. Cryopreservation is a delicate, complex, and costly procedure, and higher concentrations of dimethyl sulfoxide (DMSO), a commonly used cryoprotectant, can be toxic to cells and cause adverse effects in the recipient during infusions. In this study, we examined the effect of long-term cryopreservation using 4.35% DMSO (as final concentration) with methyl cellulose and uncontrolled rate freezing in a mechanical freezer (-80 °C) on the viability and colony-forming ability of CD34+ human PBSCs. For patients undergoing autologous HSCT, PBSCs were cryopreserved using DMSO (final concentration of 4.35%) with methyl cellulose. The post-thaw viability of PBSCs was determined using Trypan blue exclusion and flow cytometry-based 7-amino-actinomycin-D (FC-7AAD) methods. Concentrations of CD34+ stem cells and immune cell subsets in post-thaw PBSC harvest samples were assessed using multicolor flow cytometry, and the clonogenic potential of post-thaw stem cells was studied using a colony-forming unit (CFU) assay. CD34+ stem cell levels were correlated with the prestorage CD34 levels using the Pearson correlation test. The viability results in the Trypan blue dye exclusion method and the flow cytometry-based method were compared using Bland-Altman plots. We studied 26 PBSC harvest samples with a median cryopreservation duration of 6.6 years (range, 3.8 to 11.5 years). The median viability of post-thaw PBSCs was >80% using both methods, with a weak agreement between them (r=.03; P=.5). The median CD34+ stem cell count in the post-thaw samples was 9.13×106/kg (range, .44 to 26.27×106/kg). The CFU assay yielded a good proliferation and differentiation potential in post-thaw PBSCs, with a weak correlation between granulocyte macrophage CFU and CD34+ stem cell levels (r=.4; P=.05). Two samples that had been cryopreserved for >8 years showed low viability. Cryopreservation of PBSCs using 4.35% DMSO with methyl cellulose and uncontrolled freezing in a mechanical freezer at -80 °C allows the maintenance of long-term viability of PBSC for up to 8 years.

Cytotoxic and Osteoblast Differentiation Induction Properties of Crude Polar Extract of Piper sarmentosum leaves

Piper sarmentosum or ‘kaduk’ is a well-known herb plant in Malaysia. Its extracts were found to exhibit a bone-protective effect against osteoporotic rats. Our study aim is to morphologically observe the effect of P. sarmentosum ethyl acetate extract on the differentiation of human peripheral blood stem cells (PBSCs) into osteoblasts. P. sarmentosum extracts (1-900 µg/mL) prepared using 1% dimethyl sulfoxide (DMSO) were used in the cytotoxicity assay. Then, the differentiation assay was performed using concentrations of 1-50 µg/mL. The untreated cells acted as the negative control, while the cells cultured in 50 µg/mL ascorbic acid and 10 mM β-glycerophosphate was a positive control. The cytotoxicity effect and proliferation capacity of the cells were analyzed using Trypan Blue exclusion method, while the differentiation of PBSCs was observed using von Kossa staining and ALP gene expression analysis. The result showed a decrease in cells’ viability in a dose-dependent manner during cytotoxicity assay. After 14 days of the differentiation, a constant rate of proliferation could be observed in the treated cells and positive control, while the untreated cells showed an increase in proliferation. The mineralization of extract-treated cells showed significant differences (p<0.05) as compared to the negative control. The expression of ALP was also upregulated on day 14 of differentiation compared to day 0. In conclusion, the extract was capable to induce osteoblast differentiation of human peripheral blood stem cell and potential to be used in tissue regeneration

Osteogenic Potential and Bioactive Profiles of Piper sarmentosum Ethanolic Extract-Treated Stem Cells.

Piper sarmentosum is a well-known traditional herbal plant in various diseases treatments. Multiple scientific studies have also reported various biological activities exhibited by the plant's extract, such as antimicrobial, anticarcinogenic and antihyperglycemic activities, and, in addition, a bone protective effect in ovariectomized rats has been reported. However, no known Piper sarmentosum extract is involved in osteoblast differentiation using stem cells. Our study aims to identify the potential of P. sarmentosum ethanolic extract to induce osteoblast differentiation of human peripheral blood stem cells. Prior to the assay, the proliferation ability of the cells was observed for 14 days and the presence of hematopoietic stem cells in the culture was determined by the expression of SLAMF1 and CD34 genes. During the differentiation assay, the cells were treated with P. sarmentosum ethanolic extract for 14 days. Osteoblast differentiation was examined using an (alkaline phosphatase) ALP assay, by monitoring the expression of osteogenic gene markers and by von Kossa staining. The untreated cells served as the negative control, while cells treated with 50 µg/mL ascorbic acid and 10 mM β-glycerophosphate acted as the positive control. Finally, the determination of the compound profile was performed using a gas chromatography-mass spectrometry (GC-MS) analysis. The isolated cells were able to proliferate for 14 days during the proliferation assay. The expression of hematopoietic stem cell markers was also upregulated during the 14 days assay. Following the differentiation induction, the ALP activity exhibited a significant increase (p < 0.05) from day 3 of the differentiation assay. A molecular analysis also showed that the osteogenic markers ALP, RUNX2, OPN and OCN were upregulated compared to the positive control. The presence of mineralized cells with a brownish-stained morphology was observed, indicating the mineralization process increased in a time-dependent manner regardless of the concentration used. There were 54 compounds observed in the GC-MS analysis, including β-asarones, carvacrol and phytol, which have been shown to possess osteoinductive capacities. Our results demonstrate that the ethanolic extract of P. sarmentosum can induce osteoblast differentiation of peripheral blood stem cells. The extract contains potent compounds which can potentially induce the differentiation of bone cells, i.e., osteoblasts.

The Impact of Graft CD3+ T-Cell Dose on the Outcome of T-Cell Replete Human Leukocyte Antigen-Mismatched Allogeneic Hematopoietic Peripheral Blood Stem Cells Transplantation.

Data on whether the graft CD3-positive (CD3+) T-cell dose in T-cell-replete human leukocyte antigen (HLA)-mismatched allogeneic hematopoietic peripheral blood stem cells transplantation (PBSCT) influences post-transplant outcomes are controversial. Using King Hussein Cancer Center (KHCC) Blood and Marrow Transplantation (BMT) Registry database, 52 adult subjects, receiving the first T-cell-replete HLA-mismatched allogeneic hematopoietic PBSCT for acute leukemias or myelodysplastic syndrome, were identified, from January 2017 to December 2020. The cutoff value of graft CD3+ T-cell dose was identified using the receiver operating characteristic (ROC) formula and Youden's analysis. Subjects were divided into two cohorts: cohort 1 with low CD3+ T-cell dose (n = 34) and cohort 2 with high CD3+ T-cell dose (n = 18). Correlative analyses were performed between CD3+ T-cell dose and the risk of graft-versus-host disease (GvHD), relapse, relapse-free survival (RFS), and overall survival (OS). P-values were two-sided and considered significant when P < 0.05. Subject covariates were displayed. Subject's characteristics were comparable, except for higher nucleated cells and more female donors in the high CD3+ T-cell cohort. The 100-day cumulative incidence of acute GvHD (aGvHD) was 45±7% and 3-year cumulative incidence of chronic GvHD (cGvHD) was 28±6.7%. There was no statistically significant difference between the two cohorts in aGvHD (50% vs. 39%, P = 0.4) or cGvHD (29% vs. 22%, P = 0.7). The 2-year cumulative incidence of relapse (CIR) was 67.5±16.3% for low compared with 14.3±6.8% for high CD3+ T-cell cohort (P = 0.018). Fifteen subjects relapsed and 24 have died, 13 due to disease relapse. There was an improvement in 2-year RFS (94% vs. 83%; P = 0.0022) and 2-year OS (91% vs. 89%; P = 0.025) in low CD3+ T-cell cohort compared with high CD3+ T-cell cohort. Graft CD3+ T-cell dose is the only significant risk factor for relapse (P = 002), and OS (P = 0.030) in univariate analysis which was maintained in multivariate for relapse (P = 0.003), but not for OS (P = 0.050). Our data suggest that high graft CD3+ T-cell dose is associated with lower risk of relapse, and might improve long-term survival, but has no influence on the risk of developing aGvHD or cGvHD.

Insight into the Biological Activity of Hennosides-Glucosides Isolated from Lawsonia inermis (henna): Could They Be Regarded as Active Constituents Instead.

Henna is the current name of the dye prepared from the dry leaf powder of Lawsonia inermis (Lythraceae). Several studies have focused on the chemistry and pharmacology of the henna dyeing active compound, lawsone, obtained from the main constituents of leaves, hennosides, during the processing of plant material. However, knowledge regarding the biological activity of hennosides is largely lacking. In this paper, the redox activity of three hennoside isomers is reported. The pro-oxidative activity was confirmed by their ability to induce mild lysis of erythrocytes and to increase the level of methemoglobin at the concentration ≥ 500 μg/mL. The antioxidant activity of hennosides (concentration ≥100 μg/mL) was determined by FRAP and ABTS assays. At concentration of 500 μg/mL, antioxidant activity of hennoside isomers was equivalent to 0.46 ± 0.08, 0.62 ± 0.28 and 0.35 ± 0.03 mM FeSO4 × 7H2O, and 0.15 ± 0.01, 0.30 ± 0.01 and 0.09 ± 0.01 mM Trolox. Hennosides at 100 μg/mL concentration did not influence viability of human breast cancer cell lines MDA231 and MCF-7 and primary human peripheral blood and periodontal ligament-mesenchymal stem cells, but produced a modest increase in concentration of antioxidants in the cell culture supernatants. The evidenced antioxidant and pro-oxidant activities indicate their potential to act as redox balance regulator, which opens up the possibility of using hennosides in commercial phytomedicines.

How old is too old? In vivo engraftment of human peripheral blood stem cells cryopreserved for up to 18 years - implications for clinical transplantation and stability programs.

Peripheral blood stem cells (PBSC) are commonly cryopreserved awaiting clinical use for hematopoietic stem cell transplant. Long term cryopreservation is commonly defined as five years or longer, and limited data exists regarding how long PBSC can be cryopreserved and retain the ability to successfully engraft. Clinical programs, stem cell banks, and regulatory and accrediting agencies interested in product stability would benefit from such data. Thus, we assessed recovery and colony forming ability of PBSC following long-term cryopreservation as well as their ability to engraft in NOD/SCID/IL-2Rγnull (NSG) mice. To investigate the in vivo engraftment potential of long-term cryopreserved PBSC units. PBSC units which were collected and frozen using validated clinical protocols were obtained for research use from the Cellular Therapy Laboratory at Indiana University Health. These units were thawed in the Cellular Therapy Laboratory using clinical standards of practice, and the pre-freeze and post-thaw characteristics of the units were compared. Progenitor function was assessed using standard colony-forming assays. CD34-selected cells were transplanted into immunodeficient mice to assess stem cell function. Ten PBSC units with mean of 17 years in cryopreservation (range 13.6-18.3 years) demonstrated a mean total cell recovery of 88% ± 12% (range 68%-110%) and post-thaw viability of 69% ± 17% (range 34%-86%). BFU-E growth was shown in 9 of 10 units and CFU-GM growth in 7 of 10 units post-thaw. Immunodeficient mice were transplanted with CD34-selected cells from four randomly chosen PBSC units. All mice demonstrated long-term engraftment at 12 wk with mean 34% ± 24% human CD45+ cells, and differentiation with presence of human CD19+, CD3+ and CD33+ cells. Harvested bone marrow from all mice demonstrated growth of erythroid and myeloid colonies. We demonstrated engraftment of clinically-collected and thawed PBSC following cryopreservation up to 18 years in NSG mice, signifying likely successful clinical transplantation of PBSC following long-term cryopreservation.

Cyclosporine May Inhibit the Effect of Extra-Physiologic Oxygen Shock/Stress on Peripheral Blood Stem Cells

Introduction: Adequate numbers of stem cells with preserved multi-potency and self-renewing capabilities are necessary for successful hematopoietic reconstitution after bone marrow transplantation. Although hematopoietic stem cells (HSC) reside in the bone marrow under a hypoxic microenvironment (1-4% O2), human HSC are collected and processed in ambient air (21% O2) (Spencer et al., Nature 508:269-73). Exposure of murine bone marrow and human cord blood to ambient air for as little as 30 minutes triggered stem cell differentiation from quiescent pluripotent long term stem cells into activated multipotent progenitors (MPPs), a phenomenon called extra-physiologic oxygen shock / stress (EPHOSS)(Mantel et al., Cell 161:1553-65). The effect of EPHOSS on HSCs is mediated through reactive oxygen species (ROS) which open the mitochondrial permeability transition pore (MPTP) and trigger stem cell differentiation. Cyclosporine (CSA) inhibits the MPTP regulator cyclophilin D and prevents MPTP opening (Kroemer et al., Physiol Rev 87:99-163). Currently, mobilized peripheral blood stem cells (PBSCs) are the major source of grafts for hematopoietic cell transplantation. We hypothesized that EPHOSS is detrimental to human PBSCs similar to murine bone marrow and human cord blood stem cells and CSA will protect human PBSCs from the effects of EPHOSS and inhibit their differentiation from pluripotent long term HSC into short term MPPs.Study design and methods. This is a proof-of-concept, prospective, non-interventional study. We obtained G-CSF mobilized PBSCs from healthy related donors under an IRB approved protocol. All donors provided written informed consent. Blood containing HSCs was collected from each donor with minimal exposure to ambient air (<60 seconds). The sample was immediately split and incubated for 60 minutes with and without CSA (50 µg/mL). CSA treated and untreated PBSCs were immunophenotyped by multi-parameter flow cytometry for HSCs (CD34+CD38-CD90+CD45RA-), MPP (CD34+CD38-CD90-CD45RA-) and common lymphoid progenitors (CD34+CD38+CD127+). We used a CD34 ISHAGE-based gating strategy to accurately enumerate HSC and MPP.Results. In four separate experiments, CSA treated PBSCs had a higher median (range) number of HSCs/106 total nucleated cells (TNC) compared to untreated PBSCs ((297 (51 - 512) versus 185 (47 -392), respectively). CSA treated PBSCs also had a higher median (range) HSC:MPP ratio compared to untreated PBSCs ((0.56 (0.40 - 0.70) versus 0.43 (0.30 - 0.50), respectively) suggesting that the differentiation of HSC to MPP upon exposure to air was decreased in the CSA treated PBSCs.Conclusions / future directions. This is the first report describing the effect of EPHOSS in human PBSCs. Our preliminary data suggest that EPHOSS promotes the differentiation of human PBSCs from HSC to MPP and that CSA may inhibit this process. Further confirmatory and mechanistic studies exploring the contribution of MPTP and ROS to EPHOSS are ongoing. The results from this research may potentially change the current practice of collecting PBSCs in ambient air. DisclosuresMcCarthy:Janssen: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria. Chen:Bellicum Pharmaceuticals: Research Funding.

Impact of Human Leukocyte Antigen Loci and Haplotypes on Intestinal Acute Graft-versus-host Disease after Human Leukocyte Antigen-matched Sibling Peripheral Blood Stem Cell Transplantation.

Background:Acute graft-versus-host disease (aGVHD) is a common and severe complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Some studies have found that the presence of certain specific human leukocyte antigen (HLA) loci could affect the occurrence of aGVHD. Meanwhile, the impact of HLA haplotypes on aGVHD has been rarely studied. This study aimed to investigate the effects of HLA loci and haplotypes on intestinal aGVHD.Methods:Totally, 345 consecutive patients undergoing first HLA-matched sibling peripheral blood stem cell transplantation (PBSCT) from February 2004 to June 2013 at Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, were enrolled in this study. HLA loci and haplotypes of recipients with frequency over 5% were searched and their effects on intestinal aGVHD were investigated. Other important factors including donor age, recipient age, donor-recipient sex combinations, and conditioning regimens were also evaluated using logistic regression. Pure upper gastrointestinal tract aGVHD without diarrhea was excluded because the histological proof was unavailable. The follow-up end-point was 6 months after HSCT.Results:The cumulative incidence of intestinal aGVHD was 19.4%, with 18.0% of the patients classified as classic aGVHD and 1.4% as persistent, recurrent, or late aGVHD. Multivariate analysis showed that HLA-A31 locus (odds ratio [OR] 2.893, 95% confidence interval [CI] [1.054, 7.935], P = 0.039), HLA B40-DR15 (OR 3.133, 95% CI [1.250, 7.857], P = 0.015), and HLA B46-DR9 haplotypes (OR 2.580, 95% CI [1.070, 6.220], P = 0.035), female donor for male recipient (OR 2.434, 95% CI [1.319, 4.493], P = 0.004) were risk factors for intestinal aGVHD.Conclusion:The presence of certain HLA loci and haplotypes may influence the occurrence of intestinal aGVHD in PBSCT with HLA-identical sibling donors.

Anti-thymocyte globulin as graft-versus-host disease prevention in the setting of allogeneic peripheral blood stem cell transplantation: a review from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation.

Allogeneic hematopoietic stem cell transplantation is increasingly used as treatment for patients with life-threatening blood diseases. Its curative potential is largely based on immune-mediated graft-versus-leukemia effects caused by donor T cells contained in the graft. Unfortunately, donor T cells are also the cause of graft-versus-host disease. The vast majority of human leukocyte antigen-matched allogeneic hematopoietic stem cell transplants are nowadays carried out with peripheral blood stem cells as the stem cell source. In comparison with bone marrows, peripheral blood stem cells contain more hematopoietic stem/progenitor cells but also one log more T cells. Consequently, the use of peripheral blood stem cells instead of bone marrow has been associated with faster hematologic recovery and a lower risk of relapse in patients with advanced disease, but also with a higher incidence of chronic graft-versus-host disease. These observations have been the basis for several studies aimed at assessing the impact of immunoregulation with anti-thymocyte globulin on transplantation outcomes in patients given human leukocyte antigen-matched peripheral blood stem cells from related or unrelated donors. After a brief introduction on anti-thymocyte globulin, this article reviews recent studies assessing the impact of anti-thymocyte globulin on transplantation outcomes in patients given peripheral blood stem cells from human leukocyte antigen-matched related or unrelated donors as well as in recipients of grafts from human leukocyte antigen haploidentical donors.

NaïVe T Cell Depletion of PBSC Grafts Results in Very Low Rates of Chronic Gvhd and High Survival

BackgroundGraft-versus-host disease (GVHD) frequently causes morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT) as a result of organ damage and infections. In HLA-identical HCT, GVHD results from recognition by donor T cells of minor histocompatibility (H) antigens on recipient tissues. Complete T cell depletion (TCD) of donor hematopoietic cell products is more effective than pharmacologic immunosuppression for preventing GVHD, but is complicated by delayed immune reconstitution and consequent life-threatening infections.Approaches to HCT which preferentially deplete the T cells that primarily cause GVHD and preserve pathogen-specific T cells may improve HCT outcomes.Mature CD3+ CD8+ and CD3+ CD4+ T cells can be classified into CD45RA+ CD62L+ naïve (TN) and CD45RO+ memory (TM) subsets, the latter of which includes effector memory (TEM) and central memory (TCM) cells. Murine studies in which allogeneic TCD bone marrow (BM) is transplanted with purified T cells from individual T cell subsets to irradiated minor H antigen disparate recipients have demonstrated that the most severe GVHD results from transplanting T cells of the TN subset. Purified TCM causes mild GVHD and TEM do not cause detectable GVHD and can transfer immunity to pathogens.In vitro studies have similarly demonstrated that human donor CD8+ T cells specific for recipient minor H antigens are found predominantly within the TN cell subset, suggesting selective TN cell depletion may alter the GVHD incidence and/or severity in human HCT.Methods and resultsWe developed an effective process for engineering human peripheral blood stem cell (PBSC) grafts that depletes CD45RA+ TN cells and retains CD34+ stem cells and functional CD45RO+ TM cells specific for a broad range of opportunistic pathogens (Bleakley BBMT 2014). We are conducting clinical trials to evaluate the selective depletion of TN cells from HLA-matched allogeneic PBSC grafts for the prevention of GVHD in patients with acute leukemia, the first of which has been published (Bleakley JCI 2015, N=35). Seventy patients have now been treated on three consecutive phase II trials. The median age was 34 years (1-56 years), 56% of patients had a diagnosis of ALL, 46% had previously relapsed or had detectable disease (MRD or relapse) at the time of HCT, and 23% had unrelated donor (URD) grafts. Intensive myeloablative, TBI-containing (13.2Gy) conditioning was used for 63 patients, whilst 7 patients received a medium intensity ’midi’ preparative regimen, including 4Gy of TBI. The TN-depletion procedure was successfully performed on URD PBSC products shipped overnight from donor centers throughout the US, as well as on MRD PBSC collected at our centers. Reliable engraftment with high-level donor chimerism was observed in recipients of ’midi’ as well as intensive myeloablative conditioning. The 2-year estimates of overall survival, disease-free survival, survival free of relapse and chronic GVHD (CRFS) and survival free of relapse, grade II-IV acute GVHD, and chronic GVHD (GRFS) are 79%, 73%, 69% and 63% respectively. Median follow-up among survivors is 26 months. The frequency and severity of chronic GVHD is remarkably low (5%) compared to historical rates of 40-60% chronic GVHD in HLA-matched PBSC transplantation with conventional calcineurin inhibitor-based immunosuppression. Relapse and non-relapse mortality (NRM) are acceptably low at 19% and 8%, respectively. No NRM occurred in patients <40 years. Updated results will be presented.ConclusionsThe outcomes of recipients of TN-depleted PBSC grafts compare very favorably to published results of HCT for patients with acute leukemia. For example, the 69% incidence of CRFS at 2 years in TN-depleted recipients compares with reported 2-year GRFS rates of 37% and 17% in recipients of allogeneic PBSC from HLA-matched related donors with or without ATG (Kroger et al. NEJM 2016). Our results suggest that TN-depletion of PBSC grafts may reduce the risk of chronic GVHD without negatively impacting other important HCT outcomes. DisclosuresRiddell:Juno Therapeutics: Equity Ownership, Patents & Royalties, Research Funding; Cell Medica: Consultancy, Honoraria; Adaptive Biotechnologies: Consultancy, Honoraria.

562. Fetal Hemoglobin Expression Can Be Increased by Targeted Disruption of the Gamma Hemoglobin Promoter in Human Peripheral Blood Stem Cells

Hemoglobinopathies such as sickle cell disease and β-thalassemia are both common and morbid inherited genetic disorders. Mutations in the β -globin (HBB) gene result in the expression of pathologic globin molecules or the reduction in expression of the wildtype allele. Despite the high prevalence of these disorders, current treatment options are limited. Patients with a hereditary persistence of fetal hemoglobin (HPFH) have disease modifying mutations that result in the compensatory expression of gamma or delta hemoglobin and these patients tend to have a much less severe phenotype. A previously reported unique 13bp deletion identified in the gamma hemoglobin promoter of two sickle cell patients with HPFH (HbF >30%) offers a novel target for gene editing using targeted endonucleases. This region contains known binding sites for multiple regulatory factors including the DRED repressor complex and the CAAT-box binding factor (CBF). TALENs designed to target this 13bp site have been generated and the mRNA successfully transfected into human peripheral blood CD34 cells. Genomic analysis of TALEN transfected cells reveals the introduction of INDELs by NHEJ in both the γ1 (HBG1) and γ2 (HBG2) genes (33% and 8% respectively). TALEN edited human peripheral blood stem cells were then differentiated into erythroid progeny that express increased levels of fetal hemoglobin detected by both flow cytometry (>50% increase over control) and HPLC (>5-fold increase over control). CRISPR guides (traditional and chemically modified RNA guides) targeting the same locus are currently being compared to TALENs. These data suggest that the introduction of INDELs in this locus is capable of de-repressing the gamma globin gene in human CD34 cells. In vivo mouse xenografts are underway to further assess this approach as a means for a functional cure of a wide array of hemoglobinopathies.

Inducing Effect of Modified Cytokine Cocktail on Dendritic Cells

To investigate the inducing effect of 'modified' cytokine cocktail on the dendritic cell maturation and migration capability. PBMNC were isolated from human peripheral blood stem cell (PBSC) by using density gradient centrifugation, the immature DC (imDC) were induced by using GM-CSF and IL-4 in vitro. Total A549 RNA was transfected into imDC by using electroporation, which was stimulated to matuation by the "gold standard" cytokine cocktail and "modified" cytokine cocktail, respectively. The expression of DC surface markers (CD11c, HLA-DR, CD80, CD83 and CD86) and chemokine receptor (CCR5, CCR7 and CXCR4) were detected by flow cytometry; the mRNA expression levels of DC chemokine receptor (CCR2, CCR5, CCR7, CXCR3 and CXCR4) and chemokine (CCL2, CCL3, CCL5, CCL19, CCL21, CXCL10 and CXCL12) were detected by RT-PCR. As compared with "gold standard cytokine cocktail", the "modified" cytokine cocktail-induced DC expressed higher levels of surface markers (CD11c, HLA-DR, CD80, CD83 and CD86), chemokine receptors (CXCR4) and chemokine (CCL2, CCL3, CCL5, CCL19, CCL21, CXCL10 and CXCL12). The "modified" cytokine cocktail can more effectively induce the DC maturation, enhace the migratory capability of DC and more generate the immunostimulatory DC, when compared with the "gold standard" cytokine cocktail effect.

Development of Optimized Protocol for Generation of NK Cells Expressing Chimeric Antigen Receptors from Hematopoietic Stem Cells for Cancer Immunotherapy

Background : Natural Killer (NK) cells are innate immune cells that mediate cytotoxicity against tumor and virus-infected cells, and represent a very promising source for adoptive cellular approaches for cancer immunotherapy. Extensive research has been conducted, including clinical trials, attempting to harness their properties. Gene modification of NK cells can direct their specificity and enhance their function, but the efficiency of gene transfer in mature NK cells is very limited. We have previously published a protocol for generation of human NK cells from gene-modified hematopoietic stem cells (HSC) isolated from umbilical cord blood. Generation of NK cells from HSC provides the opportunity of generation of younger NK cells and expansion of specific gene-modified clones starting from a smaller number of previously isolated and cryopreserved initial cells, with added advantage of generation of multiple batches from the same donor. Chimeric antigen receptors (CAR) are engineered fusion proteins that combine the antigen specificity of antigen-binding moieties of monoclonal antibodies and intracellular activation motifs capable to activate immune cells. Preliminary evidence suggests that NK cells with specificity directed by second-generation CAR may have enhanced cytotoxicity. The goal is to develop a protocol with maximal generation of CAR-expressing NK cells from human HSC for clinical applications. We have evaluated the use of HSC isolated from G-CSF-mobilized apheresed peripheral blood mononuclear cells (PBSC), the elimination of serum in culture media and the elimination of feeder stroma.Significance : Development of a protocol for clinical translation and large-scale good manufacturing practice (GMP) compatibility, maximally generating functional CAR-expressing NK cells. G-CSF mobilized peripheral blood stem cells (PBSC) were used because of availability of larger HSC numbers, increasing safety and efficacy. Changes in culture media based on available literature were evaluated to promote generation of larger number of cells. Human AB serum and serum free media were tested to determine the cell yield for large-scale GMP-compatible protocol.Methods : A third-generation lentiviral vector co-delivering CD19-specific CAR and enhanced green fluorescent protein (EGFP) was used for gene modification of primary human PBSC. Gene-modified cells were then co-cultured with OP9-DL1 stromal cells over 35-40 days in six different culture media conditions for evaluation. Medium "A" was our previously published protocol and consisted of alpha-MEM enriched with 20% of fetal bovine serum and recombinant human cytokines SCF 5ng/mL, Flt3L 5ng/mL, IL-7 5ng/mL, and IL-15 10ng/mL. Medium "B" was AIM V enriched with 10% of human AB serum and cytokines SCF 5ng/mL, Flt3L 5ng/mL, IL-7 20ng/mL, and IL-15 50ng/mL. Medium "C" was similar to medium "B" excluding human AB serum. After 10 days of culture, IL-2 10ng/mL was added to all three media ("plus") creating six different conditions. Flow cytometry was used for detection of EGFP expression and NK cell surface markers. Digital droplet PCR was used for analysis of number of integrated viral copies. Feeder-free culture conditions were developed with the addition of recombinant human IGF-1 100ng/mL to AIM V culture media enriched with SCF, Flt-3 and IL-15.Results : NK cell differentiation was achieved in all conditions. Feeder-free conditions seemed to present mature NK cells earlier (days 25-30) than stromal co-culture (days 35-45), but lower cell yield. As previously reported, PBSC had lower yields of NK differentiation as compared to umbilical cord blood, but higher concentrations of IL-7 and IL-15 rescued the differentiation. Total cell yields were 100-220-fold expansions, with highest counts recovered from conditions with higher IL-7 and IL-15. The removal of serum and addition of IL-2 did not seem to affect differentiation or proliferation. CD56+/CD16+/CD94+ NK cells were present in 10-40% of all CD56+ cells.Conclusions : Large-scale GMP-compatible generation of clinically-relevant numbers of gene-modified NK cells from HSC is feasible. Higher doses of cytokines IL-7 and IL-15 successfully increase the yield of NK cells from PBSC. Absence of serum did not decrease differentiation or proliferation. PBSC showed folds of expansion and NK cell differentiation comparable to those obtained from umbilical cord blood. DisclosuresNo relevant conflicts of interest to declare.

HSV-sr39TK positron emission tomography and suicide gene elimination of human hematopoietic stem cells and their progeny in humanized mice.

Engineering immunity against cancer by the adoptive transfer of hematopoietic stem cells (HSC) modified to express antigen-specific T-cell receptors (TCR) or chimeric antigen receptors generates a continual supply of effector T cells, potentially providing superior anticancer efficacy compared with the infusion of terminally differentiated T cells. Here, we demonstrate the in vivo generation of functional effector T cells from CD34-enriched human peripheral blood stem cells modified with a lentiviral vector designed for clinical use encoding a TCR recognizing the cancer/testes antigen NY-ESO-1, coexpressing the PET/suicide gene sr39TK. Ex vivo analysis of T cells showed antigen- and HLA-restricted effector function against melanoma. Robust engraftment of gene-modified human cells was demonstrated with PET reporter imaging in hematopoietic niches such as femurs, humeri, vertebrae, and the thymus. Safety was demonstrated by the in vivo ablation of PET signal, NY-ESO-1-TCR-bearing cells, and integrated lentiviral vector genomes upon treatment with ganciclovir, but not with vehicle control. Our study provides support for the efficacy and safety of gene-modified HSCs as a therapeutic modality for engineered cancer immunotherapy. Cancer Res; 74(18); 5173-83. ©2014 AACR.

Gene Transfer Properties and Structural Modeling of Human Stem Cell-derived AAV

Adeno-associated virus (AAV) vectors are proving to be remarkably successful for in vivo gene delivery. Based upon reports of abundant AAV in the human marrow, we tested CD34(+) hematopoietic stem cells for the presence of natural AAV. Here, we report for the first time, the presence of novel AAV variants in healthy CD34(+) human peripheral blood stem cells. The majority of healthy peripheral blood stem cell donors were found to harbor AAV in their CD34(+) cells. Every AAV isolated from CD34(+) cells mapped to AAV Clade F. Gene transfer vectors derived from these novel AAVs efficiently underwent entry and postentry processing in human cord blood stem cells and supported stable gene transfer into long-term, in vivo engrafting human HSCs significantly better than other serotypes. AAVHSC-transduced human CD34(+) cells engrafted in vivo and gave rise to differentiated transgene-expressing progeny. Importantly, gene-marked CD34(+) stem cells persisted long term in xenograft recipients, indicating transduction of primitive progenitors. Notably, correlation of structure with function permitted identification of potential capsid components important for HSC transduction. Thus, AAVHSCs represent a new class of genetic vectors for the manipulation of HSC genomes.

Activated platelet supernatant can augment the angiogenic potential of human peripheral blood stem cells mobilized from bone marrow by G-CSF

Platelets not only play a role in hemostasis, but they also promote angiogenesis and tissue recovery by releasing various cytokines and making an angiogenic milieu. Here, we examined autologous ‘activated platelet supernatant (APS)’ as a priming agent for stem cells; thereby enhance their pro-angiogenic potential and efficacy of stem cell-based therapy for ischemic diseases. The mobilized peripheral blood stem cells (mobPBSCs) were isolated from healthy volunteers after subcutaneous injection of granulocyte-colony stimulating factor. APS was collected separately from the platelet rich plasma after activation by thrombin. mobPBSCs were primed for 6h before analysis. Compared to naive platelet supernatants, APS had a higher level of various cytokines, such as IL8, IL17, PDGF and VEGF. APS-priming for 6h induced mobPBSCs to express key angiogenic factors, surface markers (i.e. CD34, CD31, and CXCR4) and integrins (integrins α5, β1 and β2). Also mobPBSCs were polarized toward CD14(++)/CD16(+) pro-angiogenic monocytes. The priming effect was reproduced by an in vitro reconstruction of APS. Through this phenotype, APS-priming increased cell–cell adhesion and cell–extracellular matrix adhesion. The culture supernatant of APS-primed mobPBSCs contained high levels of IL8, IL10, IL17 and TNFα, and augmented proliferation and capillary network formation of human umbilical vein endothelial cells. In vivo transplantation of APS-primed mobPBSCs into athymic mice ischemic hindlimbs and Matrigel plugs elicited vessel differentiation and tissue repair. In safety analysis, platelet activity increased after mixing with mobPBSCs regardless of priming, which was normalized by aspirin treatment. Collectively, our data identify that APS-priming can enhance the angiogenic potential of mobPBSCs, which can be used as an adjunctive strategy to improve the efficacy of cell therapy for ischemic diseases.

Engineering Human Peripheral Blood Stem Cell Grafts that Are Depleted of Naïve T Cells and Retain Functional Pathogen-Specific Memory T Cells

Graft-versus-host disease (GVHD) is a frequent major complication of allogeneic hematopoietic cell transplantation (HCT). Approaches that selectively deplete T cells that cause GVHD from allogeneic stem cell grafts and preserve T cells specific for pathogens may improve HCT outcomes. It has been hypothesized that the majority of T cells that can cause GVHD reside within the naïve T cell (TN) subset, and previous studies performed in mouse models and with human cells in vitro support this hypothesis. As a prelude to translating these findings to the clinic, we developed and evaluated a novel 2-step clinically compliant procedure for manipulating peripheral blood stem cells (PBSC) to remove TN, preserve CD34+ hematopoietic stem cells, and provide for a fixed dose of memory T cells (TM) that includes T cells with specificity for common opportunistic pathogens encountered after HCT. Our studies demonstrate effective and reproducible performance of the immunomagnetic cell selection procedure for depleting TN. Moreover, after cell processing, the CD45RA-depleted PBSC products are enriched for CD4+ and CD8+ TM with a central memory phenotype and contain TM cells that are capable of proliferating and producing effector cytokines in response to opportunistic pathogens.

Radiolabeling Human Peripheral Blood Stem Cells for Positron Emission Tomography (PET) Imaging in Young Rhesus Monkeys

These studies focused on a new radiolabeling technique with copper (64Cu) and zirconium (89Zr) for positron emission tomography (PET) imaging using a CD45 antibody. Synthesis of 64Cu-CD45 and 89Zr-CD45 immunoconjugates was performed and the evaluation of the potential toxicity of radiolabeling human peripheral blood stem cells (hPBSC) was assessed in vitro (viability, population doubling times, colony forming units). hPBSC viability was maintained as the dose of 64Cu-TETA-CD45 increased from 0 (92%) to 160 µCi/mL (76%, p>0.05). Radiolabeling efficiency was not significantly increased with concentrations of 64Cu-TETA-CD45 >20 µCi/mL (p>0.50). Toxicity affecting both growth and colony formation was observed with hPBSC radiolabeled with ≥40 µCi/mL (p<0.05). For 89Zr, there were no significant differences in viability (p>0.05), and a trend towards increased radiolabeling efficiency was noted as the dose of 89Zr-Df-CD45 increased, with a greater level of radiolabeling with 160 µCi/mL compared to 0–40 µCi/mL (p<0.05). A greater than 2,000 fold-increase in the level of 89Zr-Df-CD45 labeling efficiency was observed when compared to 64Cu-TETA-CD45. Similar to 64Cu-TETA-CD45, toxicity was noted when hPBSC were radiolabeled with ≥40 µCi/mL (p<0.05) (growth, colony formation). Taken together, 20 µCi/mL resulted in the highest level of radiolabeling efficiency without altering cell function. Young rhesus monkeys that had been transplanted prenatally with 25×106 hPBSC expressing firefly luciferase were assessed with bioluminescence imaging (BLI), then 0.3 mCi of 89Zr-Df-CD45, which showed the best radiolabeling efficiency, was injected intravenously for PET imaging. Results suggest that 89Zr-Df-CD45 was able to identify engrafted hPBSC in the same locations identified by BLI, although the background was high.

CD31 expression on peripheral blood stem cells predicts both early neutrophil and platelet engraftments

No detailed information currently exists about the immune phenotypic profiles of peripheral blood stem cells (PBSCs) obtained by different mobilization regimens. The effects of these profiles on the outcome of transplantation are largely unknown. In this prospective study, the surface immune phenotypic features (CD11a, CD18, CD31, CD38, CD44, CD62e, CD62L, CD90, CD117, CD135 and CD184 expression) of sorted PBSCs that had been mobilized by growth factor with (group I and group II) or without (group III) disease-specific chemotherapies were investigated. The immune phenotypic features on mobilized PBSCs in groups I, II and III were not significantly different. The CD31 (platelet endothelial cell adhesion molecule-1) positivity ratio on PBSCs inversely correlated with both the duration of neutrophil (r=−0.32, p=0.03) and platelet (r=−0.36, p=0.02) engraftment. No relationship was found between the engraftment (neutrophil and platelet) durations and CD184 (chemokine receptor CXC motif receptor 4 [CXCR4]) expression on PBSCs. We demonstrated that the surface immune phenotypic profiles on PBSCs obtained by several mobilization regimens were not different. To our knowledge, this is the first study to demonstrate that CD31 expression on human PBSCs may positively affect both neutrophil and platelet engraftment. Contrary to our expectations, CD184 (CXCR4) expression on PBSCs has no effect on neutrophil or platelet engraftment. Considered together, our results suggest that additional surface antigens (such as CD31) may be more effective in the homing process.

Allogeneic Th1 Cells Home to Host Bone Marrow and Spleen and Mediate IFNγ-Dependent Aplasia

Bone marrow graft failure and poor graft function are frequent complications after hematopoietic stem cell transplantation and result in significant morbidity and mortality. Both conditions are associated with graft-versus-host disease (GVHD), although the mechanism remains undefined. Here we show, in 2 distinct murine models of GVHD (complete MHC- and class II-disparate) that mimic human peripheral blood stem cell transplantation, that Th1 CD4+ cells induce bone marrow failure in allogeneic recipients. Bone marrow failure after transplantation of allogeneic naïve CD4+ T cells was associated with increased CD4+ Th1 cell development within bone marrow and lymphoid tissues. Using IFNγ-reporter mice, we found that Th1 cells generated during GVHD induced bone marrow failure after transfers into secondary recipients. Homing studies demonstrated that transferred Th1 cells express CXCR4, which was associated with accumulation within bone marrow and spleen. Allogeneic Th1 cells were activated by radiation-resistant host bone marrow cells and induced bone marrow failure through an IFNγ-dependent mechanism. Thus, allogeneic Th1 CD4+ cells generated during GVHD traffic to hematopoietic sites and induce bone marrow failure via IFNγ-mediated toxicity. These results have important implications for prevention and treatment of bone marrow graft failure after hematopoietic stem cell transplantation.