Donors For Cell Transplantation Research Articles

Epigenetic aging of human blood cells is influenced by the age of the host body.

Allogenic hematopoietic stem cell transplantation is a therapeutic procedure performed over a wide range of donor and recipient age combinations, representing natural experiments of how the age of the recipient affects aging in transplanted donor cells invivo. We measured DNA methylation and epigenetic aging in donors and recipients and found that biological epigenetic clocks are accelerated in cells transplanted into an older body and decelerated in a younger body. This is the first evidence that the age of the circulating environment influences human epigenetic aging invivo.

Complete correction of murine phenylketonuria by selection-enhanced hepatocyte transplantation.

Hepatocyte transplantation for genetic liver diseases has several potential advantages over gene therapy. However, the low efficiency of cell engraftment has limited its clinical implementation. This problem could be overcome by selectively expanding transplanted donor cells until they replace enough of the liver mass to achieve therapeutic benefit. We previously described a gene therapy method to selectively expand hepatocytes deficient in cytochrome p450 reductase (Cypor) using acetaminophen (APAP). Because Cypor is required for the transformation of APAP to a hepatotoxic metabolite, Cypor-deficient cells are protected from toxicity and are able to expand following APAP-induced liver injury. Here, we apply this selection system to correct a mouse model of phenylketonuria by cell transplantation. Hepatocytes from a wild-type donor animal were edited in vitro to create Cypor deficiency and then transplanted into phenylketonuric animals. Following selection with APAP, blood phenylalanine concentrations were fully normalized and remained stable following APAP withdrawal. Cypor-deficient hepatocytes expanded from < 1% to ~14% in corrected animals, and they showed no abnormalities in blood chemistries, liver histology, or drug metabolism. We conclude that APAP-mediated selection of transplanted hepatocytes is a potential therapeutic for phenylketonuria with long-term efficacy and a favorable safety profile.

Germ cell recovery, cryopreservation and transplantation in the California white sturgeon, Acipenser transmontanus

The white sturgeon (Acipenser transmontanus) is the largest freshwater fish in North America. Because of the unique life history characteristics of sturgeon, including longevity, late maturation and long spawning intervals, their aquaculture can be a significant investment of resources. As a result of habitat loss and overharvesting, natural populations of white sturgeon are threatened and there is a growing effort to improve conservation aquaculture programs. Germ cell transplantation is an innovative technology previously demonstrated in a variety of fish species to be able to produce a surrogate broodstock. The technique relies upon optimal donor germ cell recovery and transplantation into a recipient fish. In this study, we developed and optimized the harvest of donor cells for germline transplantation and evaluated methods for ovary cryopreservation for the first time in the white sturgeon. We found that harvesting gonads from juveniles between the ages of 1.5 and 2.5-years resulted in reliably high proportions of pre-meiotic cells regardless of sex, a critical feature for using white sturgeon for transplantation studies since the species shows no distinguishing external sex characteristics. From the viable cells, we identified germline cells using immunolabeling with the antibody DDX4, a marker specific to the germline. For in vivo tracking of donor cells during transplantations, gonadal cells were stained with a long half-life non-toxic cell membrane dye, PKH26, and microinjected into the peritoneal cavity of newly hatched white sturgeon larvae. Larvae were reared until 3 months post-transplantation to monitor for colonization and proliferation of PKH26-labeled cells within the recipient larval gonads. Furthermore, viable cell detection, assessment of germline-specificity, and transplantation was determined for cells recovered from cryopreserved ovarian tissue from sexually immature females. Transplantations using cells cryopreserved with media supplemented with dimethyl sulfoxide (DMSO) rather than ethylene glycol (EG) demonstrated the highest number of PKH26-labeled cells distributed along the gonadal ridges of the larval recipient. Determining optimal methods of tissue cryopreservation, and germ cell recovery and transplantation are foundational to the future development of germ cell transplantation as a strategy to improve the aquaculture and conservation of this species. Our study demonstrates that conservation actions, such as surrogate breeding, could be utilized by hatcheries to retain or improve natural gamete production without genetic modification, and provide an encouraging approach to the management of threatened sturgeon species.

Induced differentiation of primordial germ cell like cells from SOX9+ porcine skin derived stem cells

Understanding the mechanisms behind porcine primordial germ cell like cells (pPGCLCs) development, differentiation, and gametogenesis is crucial in the treatment of infertility. In this study, SOX9+ skin derived stem cells (SOX9+ SDSCs) were isolated from fetal porcine skin and a high-purity SOX9+ SDSCs population was obtained. The SOX9+ SDSCs were induced to transdifferentiate into PGCLCs during 8 days of cultured. The results of RNA-seq, western blot and immunofluorescence staining verified SDSCs have the potential to transdifferentiate into PGCLCs from aspects of transcription factor activation, germ layer differentiation, energy metabolism, and epigenetic changes. Both adherent and suspended cells were collected. The adherent cells were found to be very similar to early porcine primordial germ cells (pPGCs). The suspended cells resembled late stage pPGCs and had a potential to enter meiotic process. This SDSCs culture-induced in vitro model is expected to provide suitable donor cells for stem cell transplantation in the future.

Pilot Study of Donor-Engrafted Clonal Hematopoiesis Evolution and Clinical Outcomes in Allogeneic Hematopoietic Cell Transplantation Recipients Using a National Registry

Improved treatment options, such as reduced-intensity conditioning (RIC), enable older patients to receive potentially curative allogeneic hematopoietic cell transplantation (HCT). This progress has led to increased use of older HLA-matched sibling donors. An unintended potential risk associated with older donors is transplantation of donor cells with clonal hematopoiesis (CH) into patients. We aimed to determine the prevalence of CH in older HLA-matched sibling donors pretransplantation and to assess the clinical impact of donor-engrafted CH on HCT outcomes. This was an observational study using donor peripheral blood samples from the Center for International Blood and Marrow Transplant Research repository, linked with corresponding recipient outcomes. To explore engraftment efficiency and evolution of CH mutations following HCT, recipient follow-up samples available through the Bone Marrow Transplant Clinical Trials Network (Protocol 1202) were included. Older donors and patients (both ≥55 years) receiving first RIC HCT for myeloid malignancies were eligible. DNA from archived donor blood samples was used for targeted deep sequencing to identify CH. The associations between donor CH status and recipient outcomes, including acute graft-versus-host disease (aGVHD), chronic GVHD (cGVHD), overall survival, relapse, nonrelapse mortality, disease-free survival, composite GVHD-free and relapse-free survival, and cGVHD-free and relapse-free survival, were analyzed. A total of 299 donors were successfully sequenced to detect CH. At a variant allele frequency (VAF) ≥2%, there were 44 CH mutations in 13.7% (41 of 299) of HLA-matched sibling donors. CH mostly involved DNMT3A (n=27; 61.4%) and TET2 (n= 9; 20.5%). Post-HCT samples from 13 recipients were also sequenced, of whom 7 had CH+ donors. All of the donor CH mutations (n=7/7; 100%) were detected in recipients at day 56 or day 90 post-HCT. Overall, mutation VAFs remained relatively constant up to day 90 post-HCT (median change, .005; range, -.008 to .024). Doubling time analysis of recipient day 56 and day 90 data showed that donor-engrafted CH mutations initially expand then decrease to a stable VAF; germline mutations had longer doubling times than CH mutations. The cumulative incidence of grade II-IV aGVHD at day 100 was higher in HCT recipients with CH+ donors (37.5% versus 25.1%); however, the risk for aGVHD by donor CH status did not reach statistical significance (hazard ratio, 1.35; 95% confidence interval, .61 to 3.01; P=.47). There were no statistically significant differences in the cumulative incidence of cGVHD or any secondary outcomes by donor CH status. In subset analysis, the incidence of cGVHD was lower in recipients of grafts from DNMT3A CH+ donors versus donors without DNMT3A CH (34.4% versus 57%; P=.035). Donor cell leukemia was not reported in any donor-recipient pairs. CH in older HLA-matched sibling donors is relatively common and successfully engrafts and persists in recipients. In a homogenous population (myeloid malignancies, older donors and recipients, RICr, non-cyclophosphamide-containing GVHD prophylaxis), we did not detect a difference in cGVHD risk or other secondary outcomes by donor CH status. Subgroup analyses suggest potential differential effects by clinical characteristics and CH mutations. Larger prospective studies are needed to robustly determine which subsets of patients and CH mutations elicit meaningful impacts on clinical outcomes.

Hydrogel assisted photoreceptor delivery inhibits material transfer

Cell therapy holds tremendous promise for vision restoration; yet donor cell survival and integration continue to limit efficacy of these strategies. Transplanted photoreceptors, which mediate light sensitivity in the retina, transfer cytoplasmic components to host photoreceptors instead of integrating into the tissue. Donor cell material transfer could, therefore, function as a protein augmentation strategy to restore photoreceptor function. Biomaterials, such as hyaluronan-based hydrogels, can support donor cell survival but have not been evaluated for effects on material transfer. With increased survival, we hypothesized that we would achieve greater material transfer; however, the opposite occurred. Photoreceptors delivered to the subretinal space in mice in a hyaluronan and methylcellulose (HAMC) hydrogel showed reduced material transfer. We examined mitochondria transfer in vitro and cytosolic protein transfer in vivo and demonstrate that HAMC significantly reduced transfer in both contexts, which we ascribe to reduced cell-cell contact. Nanotube-like donor cell protrusions were significantly reduced in the hydrogel-transplanted photoreceptors compared to the saline control group, which suggests that HAMC limits the contact required to the host retina for transfer. Thus, HAMC can be used to manipulate the behaviour of transplanted donor cells in cell therapy strategies.

Maximizing colonization and proliferation of blue catfish (Ictalurus furcatus) donor stem cells for the creation of xenogenic catfish: Identifying the best host age of triploid channel catfish (I. punctatus)

Xenogenesis is an innovative technology for hybrid catfish (♀ channel catfish, Ictalurus punctatus, × ♂ blue catfish, I. furcatus) embryo production. The xenogeneic process can be accomplished by transplanting undifferentiated diploid germline stem cells derived from donor fish into sterile recipients. This methodology enables recipients to produce donor-derived gametes. Until recently, the timing of transplantation of donor cells into hosts was done with limited knowledge of the best age to inject cells. The age of the host could critically affect the success of germ cell transplantation. The present study aimed to identify the best age of the triploid channel catfish to transplant blue catfish stem cells for production of xenogeneic catfish. Triploid channel catfish fry were injected with blue catfish stem cells labeled with PKH26 dye from 0 to 18 days post-hatch (DPH). Then at 50 DPH (1st time interval) and 90 DPH (2nd time interval), total length (TL), weight (BW), and survival of recipients were evaluated. Colonization of donor cells was evaluated in recipients using PKH26 dye fluorescence to calculate percent cell (<150 μm2) and cluster areas (>150 μm2). PCR determined the percentage of xenogens from gonads. Day of stem cell injection had no impact on TL and BW of recipient fish when evaluated at both sampling intervals. Survival of recipients injected with blue catfish stem cells increased from 0 to 5.4 DPH. After 5.4 DPH, survival remained high (≥82%) for fry injected until 18 DPH. At the 1st time interval, cell and cluster area increased as recipients fish injected from 0 to 5.4 DPH and 0 to 5.6 DPH, respectively. Thereafter, fluorescent cell and cluster area in the host declined with no further decrease after 11.3 and 10.4 DPH, respectively. At the 2nd time interval, cell and cluster area increased as recipients were injected from 0 to 5.8 DPH and 0 to 5.7 DPH and significantly declined with no further decrease after 10.2 and 11.3 DPH, respectively. At the 1st time interval, the highest percentage of xenogens were detected when recipients were injected from 3 to 5 DPH (83.3%), while at the 2nd time interval, the highest percentage of xenogens was detected from 4 to 6 DPH (83.3%). Our results show that 4 to 6 DPH is a suitable timespan to inject donor-derived stem cells into recipients. These findings will enhance the efficiency of germ cell transplantation for commercial-scale hybrid catfish production.

Maturation of stem cell derived retinal organoid cells following subretinal transplantation

AbstractRetinal cell therapy is envisioned as a treatment modality to repair the retina and improve vision in people with degenerative or hereditary retinopathies. In pursuit of this goal, transplantation of ES/iPS‐derived photoreceptor precursor cells is being developed as a treatment to replace lost photoreceptor cells. Several studies have shown that photoreceptor precursors can mature and incorporate into the recipient retina following transplantation in the subretinal space. However, knowledge regarding the identity and distribution of transplanted cells is incomplete, and furthermore, how closely the transplanted photoreceptors resemble normal photoreceptors in an intact wild‐type retina is unclear. In addition, a key gap in knowledge pertains to how the recipient retina regulates the maturation, fate specification, and migration of transplanted donor cells. This talk will describe how the subretinal space in the degenerative recipient eye promotes the maturation of transplanted rod and cone photoreceptor cells. In addition, observations of graft‐derived cells that migrate into the recipient retina, including some that travel long distances away from the graft, are presented. These findings highlight that in vitro human micro‐organogenesis can produce complex organoids with unusual and unexpected ectopic components that do not typically comprise the normal organ, and thus can profoundly influence therapeutic studies that use those organoids. These findings demonstrate the importance of the extracellular microenvironment in determining cell identity and behaviour in human organoids being developed for treatment purposes.

Long-Term Persistence of Mixed Full Donor Chimerism after Double Cord Blood Transplantation. Example of Tolerance in Allogeneic Hematopoietic Cell Transplantation Setting

Background Double umbilical cord blood transplantation (UCBT) is recognized as an alternative source of hematopoietic donor cells for allogeneic haematopoietic cell transplantation (HCT), particularly in adult setting. Because of important infectious complications, UCBT are rarely utilized and more and more replaced by haplo-identical cell transplantation for adult patients. Nevertheless, some very good results were observed with a long-term follow-up. In most cases, after several weeks, one unit turns immuno-dominant and thus, the second one is no longer detected. Patients and Methods We reported three cases of long-term mixed full donor chimerism associated to documented complete remission of haematological malignancies after double UCBT. The indications of UCBT were acute myeloid leukaemia for 2 patients [1 AML MRC (female of 65 years) and 1 transformation of Fanconi disease (female of 20 years)] and acute lymphoid leukaemia for 1 patient (female of 22 years). AML received a reduced intensity and ALL a standard conditioning. The general characteristics of recipients and UCB are presented in Table 1. The chimerism follow-up were performed by STR and qPCR techniques with a sensitivity of 5 and 0.2% respectively. Early after transplantation, patient 1 developed a grade I graft-versus-host disease (GVHD), patient 3 a grade II GVHD treated by extracorporeal photopheresis, and patient 2 did not develop any GVHD. The follow-up of these patients were 14, 13 and 8 years respectively after UCBT without any episodes of relapse and at the last follow-up still a total donor mixed chimerism. Results Results of STR and qPCR after transplantation early revealed the presence of the two transplant units with a total donor chimerism (Table 1). Patient 1 presented a perfectly balanced chimerism with 54 % of the majority unit. The other two patients showed an imbalance in the proportions of their two UCB with 83% and 72% of their majority units respectively but a long-term persistence of 17% and 28% of their second UCB. The study of total blood chimerism during their follow-up revealed a stabilization of the proportions of the two units during the first year (Figure 1). A more in-depth study of circulating cell subsets (CD3+, CD15+ and CD19+) chimerism of patient 1 revealed a very strong initial imbalance of the two units, which ended up being balanced at two years after transplantation. In the other two patients, the respective study of CD3+ and CD33+ cells showed a stabilization of the two unit percentage around six months after transplantation. At five years after transplantation, patient 1 had an in-depth study of circulating cells sub-populations (CD4+ T lymphocytes, CD8+ T lymphocytes, B-lymphocytes, natural killer cells, regulatory T cells, monocytes, naive CD4+ and CD8+ T lymphocytes) by flow cytometry, after separation of the two units cells by specific monoclonal antibody directed against HLA mismatching antigen (HLA-A2). This analysis revealed an imbalance in the percentage of NK and monocytes. The immune-dominant unit had three times more NK cells than the other one and this imbalance ratio increased by twenty-two for monocytes. A co-culture study of the CD4+ lymphocytes demonstrated a lack of reactivity of both unit against the other one but a normal ability to react against an allogeneic third-part cell. Conclusions This expected tolerance, highlighted in co-culture experience, showed rare cases of naturally induced graft tolerance. A study of tolerance markers and underlying mechanisms in these special cases of persistent mixed full donor chimerism is necessary to acquire better knowledge and to define more investigations ways for the induction of tolerance in patients receiving hematopoietic cell transplantation or organ transplantations. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Prevention of non-infectious pulmonary complications after intra-bone marrow stem cell transplantation in mice.

Non-infectious pulmonary complications including idiopathic pneumonia syndrome (IPS) and bronchiolitis obliterans syndrome (BOS), which are clinical and diagnostic manifestations of lung chronic graft-versus-host disease (GVHD), cause significant mortality after allogeneic stem cell transplantation (SCT). Increasing evidence suggests that alloantigen reactions in lung tissue play a central role in the pathogenesis of IPS and BOS; however, the mechanism is not fully understood. Several clinical and experimental studies have reported that intra-bone marrow (IBM)-SCT provides high rates of engraftment and is associated with a low incidence of acute GVHD. In the present study, allogeneic SCT was conducted in mouse models of IPS and BOS, to compare intravenous (IV)-SCT with IBM-SCT. Allogeneic IBM-SCT improved the clinical and pathological outcomes of pulmonary complications compared to those of IV-SCT. The mechanisms underlying the reductions in pulmonary complications in IBM-SCT mice were explored. The infiltrating lung cells were mainly CD11b+ myeloid and CD3+ T cells, in the same proportions as in transplanted donor cells. In an in vivo bioluminescence imaging, a higher proportion of injected donor cells was detected in the lung during the early phase (1 h after IV-SCT) than after IBM-SCT (16.7 ± 1.1 vs. 3.1 ± 0.7 × 105 photons/s/animal, IV-SCT vs. IBM-SCT, P = 1.90 × 10−10). In the late phase (5 days) after SCT, there were also significantly more donor cells in the lung after IV-SCT than after IBM-SCT or allogeneic-SCT (508.5 ± 66.1 vs. 160.1 ± 61.9 × 106 photons/s/animal, IV-SCT vs. IBM-SCT, P = 0.001), suggesting that the allogeneic reaction induces sustained donor cell infiltration in the lung during the late phase. These results demonstrated that IBM-SCT is capable of reducing injected donor cells in the lung; IBM-SCT decreases donor cell infiltration. IBM-SCT therefore represents a promising transplantation strategy for reducing pulmonary complications, by suppressing the first step in the pathophysiology of chronic GVHD.

Abstract LB063: Duplex Sequencing reveals ubiquitous clonal hematopoiesis and complex donor-recipient clonal dynamics following HSCT

Abstract Clonal hematopoiesis (CH aka CHIP) is the process whereby otherwise healthy individuals accumulate clones bearing low-frequency somatic mutations in hematologic malignancy (HM) driver genes. Historically thought to be a phenomenon of the elderly that is associated with increased risk of HM and cardiovascular disease, CH has been observed in increasingly younger cohorts as sequencing technology has advanced. CH in hematopoietic stem cell transplant (HSCT) donors has also been associated with adverse recipient outcomes. In this retrospective analysis, we asked whether CH mutations preferentially expanded in recipients vs. donors in paired samples collected a median of 34 years post-HSCT (range 6-45). 16 donor-recipient pairs were analyzed, 11 of which had a donor sample collected pre-HSCT. All individuals were healthy at the time of contemporary sampling. Median donor age was 26 years (range 12-84) at time of HSCT. We took advantage of the ultra-low error rate (&amp;lt;1-in-10-million) of Duplex Sequencing (DS) to comprehensively assess CH in genomic DNA from blood. We targeted 29 genes recurrently mutated in acute myeloid leukemia (AML) plus 48 kilobases of randomly chosen neutral genomic regions. The mean DS error-corrected molecular depth across all samples was 26,731x for AML-associated genes and 32,812x in the neutral regions. CH was detected in 100% of donors and recipients, with a trend toward more CH clones in older vs. younger donors. We defined CH as mutations observed in at least 2 unique DNA molecules, rather than by a threshold variant allele frequency (VAF). Among the 11 donors with matched historical and contemporary DNA samples, CH mutations in the latter had a higher average VAF and comprised more unique mutations than in the former, reflecting clonal expansions over time. The magnitude of CH expansions was greater for the AML-associated genes than for neutral loci, consistent with positive selection. Post-HSCT the overall number of unique mutations was similar between donors and recipients. Most donor CH variants did not preferentially expand in the recipient. A minority of recipients had a modestly increased overall average VAF relative to paired donors in AML genes. While the VAF of some likely pathogenic variants increased in the recipient vs the donor, this was not the case for most CH mutations in most recipients and the reciprocal was sometimes observed. DS represents a powerful tool for the high-resolution study of CH evolution. In a unique historical cohort comprising longitudinal samples from some of the earliest patients and donors to undergo HSCT, we observed limited instances of accelerated CH in recipients relative to donors. While this cohort is biased due to enriched inclusion of long-term survivors, our data exemplifies how healthy hematopoiesis, indistinguishable between donors and recipients, can be maintained almost half a century following transplant. Citation Format: Masumi Ueda, Jake Higgins, Thomas Smith, Elizabeth Schmidt, Fang Y. Lo, Charles C. Valentine, Jesse J. Salk, Rainer Storb, Jerald P. Radich. Duplex Sequencing reveals ubiquitous clonal hematopoiesis and complex donor-recipient clonal dynamics following HSCT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB063.

Initiation of an eligibility screening protocol prior to tissue typing of potential stem cell donors resulted in substantial cost savings.

e19047 Background: Human Leukocyte Antigen (HLA) typing is a necessary but expensive process to identify suitable donors for allogeneic hematopoietic cell transplantation (HCT) for the treatment of bone marrow disorders and hematologic malignancies. The likelihood of a patient and sibling being fully HLA matched is 25%. An HLA-identical related donor remains the preferred source among HCT recipients due to superior outcomes when compared to unrelated, mismatched, haploidentical, or cord blood. Because of the high probability of finding an HLA matched donor among siblings, and the benefit of quick access to these donors, it had been standard procedure at our institute to test all siblings to identify potential matches. The estimated costs of HLA typing alone is approximately $300-$1000 and is contingent upon the lab utilized and resolution of typing. The costs of HLA typing, additional testing, and screening are significant to patients and health care systems. Methods: Our institution initiated a protocol to assess potential sibling donors prior to HLA typing as per the donor eligibility guidelines of the National Marrow Donor Program (NMDP). From 2018-2020 each sibling was given a questionnaire prior to HLA typing and screened for suitability. If a sibling was determined to be ineligible for donation based on the NMDP guidelines, HLA typing and work up for that sibling was not pursued. Results: Between 2018 and 2020 we identified 789 potential donors for HCT. All potential donors were sent eligibility questionnaires. Based on this screening, 568 potential donors were found to be eligible for donation whereas 221 were ineligible. HLA typing was pursued in all eligible donors. This resulted in and estimated cost savings of $66,000-$221,000 in HLA typing alone. This translated into a substantial health care cost savings for our institution as compared to our prior policy of typing all siblings. Conclusions: Identification and work up for potential HLA matched siblings is critical for identifying optimal donors for HCT. Our previous policy of universal sibling screening was found to be costly due to typing individuals who later were found to be ineligible to donate. We found that the initiation of a simple donor screening protocol that excluded ineligible sibling donors resulted in significant cost savings compared to our prior policy of HLA typing all potential sibling donors. Cost savings are a relevant consideration in all aspects of healthcare and this screening tool could be a practical component of the best practice guidelines for HLA matching and HCT.

Systematic Scoping Review of Studies Reporting Unexpected Donor-Derived Abnormalities from Recipients of Allogeneic Hematopoietic Cell Transplantation: A Proposed Framework for Donor Disclosure

Allogeneic hematopoietic cell transplantation (HCT) is used increasingly to treat blood and immune-based disorders. Post-transplantation testing of HCT recipients can lead to unexpected molecular, cytogenetic, and other information in donor-derived cells, raising questions regarding the potential impact on donor health. This study was conducted to identify the breadth of donor-derived abnormalities identified by testing HCT recipients and to determine the extent to which disclosure and donor follow-up are described. A systematic search and scoping review were conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for scoping review guidelines in OVID MEDLINE and Embase (1947 to May 24, 2021). We identified 38 studies (63 donor-recipient pairs) addressing nonleukemic abnormalities to complement existing literature describing donor cell leukemia and donor-derived myelodysplasia. Donors were unrelated adults (n=20), related family members (n=28), cord blood donors (n=6), or not reported (n=9). Acquired cytogenetic, molecular, and morphologic abnormalities were reported. Donor origin was confirmed by cytogenetic analysis via karyotyping, fluorescence in situ hybridization, single tandem repeat PCR, and other techniques. A disease in donor-derived cells was described in 35 recipients (56.5%). Despite the relevance for testing and disclosure to donors, only 22 cases (32%) mentioned donor follow-up, and in 5 cases the donor developed a disease associated with the identified abnormality. Unrelated donor disclosure was mentioned in 3 of 26 cases (12%), with the findings reported back to the registry. Incidental abnormalities identified in transplanted donor cells may contribute to the post-transplantation risk of illness in the recipient and may be relevant to donor health. A framework for donor disclosure is proposed that incorporates consideration of analytic validity of the testing, potential significance of the finding, and the extent to which the abnormality is actionable. Adoption of effective processes to safeguard both donor and recipient health outcomes related to this issue is needed.

Lung Regeneration by Transplantation of Allogeneic Lung Progenitors Using a Safer Conditioning Regimen and Clinical-grade Reagents.

Over the last decades, several studies demonstrated the possibility of lung regeneration through transplantation of various lung progenitor populations. Recently, we showed in mice that fetal or adult lung progenitors could potentially provide donor cells for transplantation, provided that the lung stem cell niche in the recipient is vacated of endogenous lung progenitors by adequate conditioning. Accordingly, marked lung regeneration could be attained following i.v. infusion of a single cell suspension of lung cells into recipient mice conditioned with naphthalene (NA) and 6Gy total body irradiation (TBI). As clinical translation of this approach requires the use of allogenic donors, we more recently developed a novel transplantation modality based on co-infusion of hematopoietic and lung progenitors from the same donor. Thus, by virtue of hematopoietic chimerism, which leads to immune tolerance toward donor antigens, the lung progenitors can be successfully engrafted without any need for post-transplant immune suppression. In the present study, we demonstrate that it is possible to replace NA in the conditioning regimen with Cyclophosphamide (CY), approved for the treatment of many diseases and that a lower dose of 2 GY TBI can successfully enable engraftment of donor-derived hematopoietic and lung progenitors when CY is administered in 2 doses after the stem cell infusion. Taken together, our results suggest a feasible and relatively safe protocol that could potentially be translated to clinical transplantation of lung progenitors across major MHC barriers in patients with terminal lung diseases.

Clinical and preclinical tolerance protocols for vascularized composite allograft transplantation.

The field of vascularized composite allografts (VCAs) has undergone significant advancement in recent decades, and VCAs are increasingly common and accepted in the clinical setting, bringing hope of functional recovery to patients with debilitating injuries. A major obstacle facing the widespread application of VCAs is the side effect profile associated with the current immunosuppressive regimen, which can cause a wide array of complications such as infection, malignancy, and even death. Significant concerns remain regarding whether the treatment outweighs the risk. The potential solution to this dilemma would be achieving VCA tolerance, which would allow recipients to receive allografts without significant immunosuppression and its sequelae. Promising tolerance protocols are being studied in kidney transplantation; four major trials have attempted to withdraw immunosuppressive treatment with various successes. The common theme in all four trials is the use of radiation treatment and donor cell transplantation. The knowledge gained from these trials can provide valuable insight into the development of a VCA tolerance protocol. Despite similarities, VCAs present additional barriers compared to kidney allografts regarding tolerance induction. VCA donors are likely to be deceased, which limits the time for significant pre-conditioning. VCA donors are also more likely to be human leukocyte antigen–mismatched, which means that tolerance must be induced across major immunological barriers. This review also explores adjunct therapies studied in large animal models that could be the missing element in establishing a safe and stable tolerance induction method.

Characterization and allogeneic transplantation of a novel transgenic cone-rich donor mouse line

ObjectivesCone photoreceptor transplantation is a potential treatment for macular diseases. The optimal conditions for cone transplantation are poorly understood, partly because of the scarcity of cones in donor mice. To facilitate allogeneic cone photoreceptor transplantation studies in mice, we aimed to create and characterize a donor mouse model containing a cone-rich retina with a cone-specific enhanced green fluorescent protein (EGFP) reporter. MethodsWe generated OPN1LW-EGFP/NRL−/− mice by crossing NRL−/− and OPN1LW-EGFP mice. We characterized the anatomical phenotype of OPN1LW-EGFP/NRL−/− mice using multimodal confocal scanning laser ophthalmoscopy (cSLO) imaging, immunohistology, and transmission electron microscopy. We evaluated retinal function using electroretinography (ERG), including 465 and 525 nm chromatic stimuli. Retinal sheets and cell suspensions from OPN1LW-EGFP/NRL−/− mice were transplanted subretinally into immunodeficient Rd1 mice. ResultsOPN1LW-EGFP/NRL−/− retinas were enriched with OPN1LW-EGFP+ and S-opsin+ cone photoreceptors in a dorsal-ventral distribution gradient. Cone photoreceptors co-expressing OPNL1W-EGFP and S-opsin significantly increased in OPN1LW-EGFP/NRL−/− compared to OPN1LW-EGFP mice. Temporal dynamics of rosette formation in the OPN1LW-EGFP/NRL−/− were similar as the NRL−/− with peak formation at P15. Rosettes formed preferentially in the ventral retina. The outer retina in P35 OPN1LW-EGFP/NRL−/− was thinner than NRL−/− controls. The OPN1LW-EGFP/NRL−/− ERG response amplitudes to 465 nm stimulation were similar to, but to 535 nm stimulation were lower than, NRL−/− controls. Three months after transplantation, the suspension grafts showed greater macroscopic degradation than sheet grafts. Retinal sheet grafts from OPN1LW-EGFP/NRL−/− mice showed greater S-opsin + cone survival than suspension grafts from the same strain. ConclusionsOPN1LW-EGFP/NRL−/− retinae were enriched with S-opsin+ photoreceptors. Sustained expression of EGFP facilitated the longitudinal tracking of transplanted donor cells. Transplantation of cone-rich retinal grafts harvested prior to peak rosette formation survived and differentiated into cone photoreceptor subtypes. Photoreceptor sheet transplantation may promote greater macroscopic graft integrity and S-opsin+ cone survival than cell suspension transplantation, although the mechanism underlying this observation is unclear at present. This novel cone-rich reporter mouse strain may be useful to study the influence of graft structure on cone survival.

Postpubertal spermatogonial stem cell transplantation restores functional sperm production in rhesus monkeys irradiated before and after puberty.

Cancer treatment of prepubertal patients impacts future fertility due to the abolition of spermatogonial stem cells (SSCs). In macaques, spermatogenesis could be regenerated by intratesticular transplantation of SSCs, but no studies have involved cytotoxic treatment before puberty and transplantation after puberty, which would be the most likely clinical scenario. To evaluate donor-derived functional sperm production after SSC transplantation to adult monkeys that had received testicular irradiation during the prepubertal period. We obtained prepubertal testis tissue by unilaterally castrating six prepubertal monkeys and 2weeks later irradiated the remaining testes with 6.9Gy. However, because spermatogenic recovery was observed, we irradiated them again 14months later with 7Gy. Three of the monkeys were treated with GnRH-antagonist (GnRH-ant) for 8weeks. The cryopreserved testis cells from the castrated testes were then allogeneically transplanted into the intact testes of all monkeys. Tissues were harvested 10months later for analyses. In three of the six monkeys, 61%, 38%, and 11% of the epididymal sperm DNA were of the donor genotype. The ability to recover donor-derived sperm production was not enhanced by the GnRH-ant pretreatment. However, the extent of filling seminiferous tubules during the transplantation procedure was correlated with the eventual production of donor spermatozoa. The donor epididymal spermatozoa from the recipient with 61% donor contribution were capable of fertilizing rhesus eggs and forming embryos. Although the transplantation was done into the rete testis, two GnRH-ant-treated monkeys, which did not produce donor-derived epididymal spermatozoa, displayed irregular tubular cords in the interstitium containing testicular spermatozoa derived from the transplanted donor cells. The results further support that sperm production can be restored in non-human primates from tissues cryopreserved prior to prepubertal and post-pubertal gonadotoxic treatment by transplantation of these testicular cells after puberty into seminiferous tubules.

Apoptotic Donor Cells in Transplantation.

Despite significant advances in prevention and treatment of transplant rejection with immunosuppressive medications, we continue to face challenges of long-term graft survival, detrimental medication side effects to both the recipient and transplanted organ together with risks for opportunistic infections. Transplantation tolerance has so far only been achieved through hematopoietic chimerism, which carries with it a serious and life-threatening risk of graft versus host disease, along with variability in persistence of chimerism and uncertainty of sustained tolerance. More recently, numerous in vitro and in vivo studies have explored the therapeutic potential of silent clearance of apoptotic cells which have been well known to aid in maintaining peripheral tolerance to self. Apoptotic cells from a donor not only have the ability of down regulating the immune response, but also are a way of providing donor antigens to recipient antigen-presenting-cells that can then promote donor-specific peripheral tolerance. Herein, we review both laboratory and clinical evidence that support the utility of apoptotic cell-based therapies in prevention and treatment of graft versus host disease and transplant rejection along with induction of donor-specific tolerance in solid organ transplantation. We have highlighted the potential limitations and challenges of this apoptotic donor cell-based therapy together with ongoing advancements and attempts made to overcome them.

Maternal microchimerism and cell-mediated immune-modulation enhance engraftment following semi-allogenic intrauterine transplantation.

Successful intrauterine hematopoietic cell transplantation (IUT) for congenital hemoglobinopathies is hampered by maternal alloresponsiveness. We investigate these interactions in semi-allogenic murine IUT. E14 fetuses (B6 females × BALB/c males) were each treated with 5E+6 maternal (B6) or paternal (BALB/c) bone marrow cells and serially monitored for chimerism (>1% engraftment), trafficked maternal immune cells, and immune responsiveness to donor cells. A total of 41.0% of maternal IUT recipients (mIUT) were chimeras (mean donor chimerism 3.0±1.3%) versus 75.0% of paternal IUT recipients (pIUT, 3.6±1.1%). Chimeras showed higher maternal microchimerism of CD4, CD8, and CD19 than non-chimeras. These maternal cells showed minimal responsiveness to B6 or BALB/c stimulation. To interrogate tolerance, mIUT were injected postnatally with 5E+6 B6 cells/pup; pIUT received BALB/c cells. IUT-treated pups showed no changes in trafficked maternal or fetal immune cell levels compared to controls. Donor-specific IgM and IgG were expressed by 1%-3% of recipients. mIUT splenocytes showed greater proliferation of regulatory T cells (Treg) upon BALB/c stimulation, while B6 stimulation upregulated the pro-inflammatory cytokines more than BALB/c. pIUT splenocytes produced identical Treg and cytokine responses to BALB/c and B6 cells, with higher Treg activity and lower pro-inflammatory cytokine expression upon exposure to BALB/c. In contrast, naïve fetal splenocytes demonstrated greater alloresponsiveness to BALB/c compared to B6 cells. Thus pIUT, associated with increased maternal cell trafficking, modulates fetal Treg, and cytokine responsiveness to donor cells more efficiently than mIUT, resulting in improved engraftment. Paternal donor cells may be considered alternatively to maternal donor cells for intrauterine and postnatal transplantation to induce tolerance and maintain engraftment.

Protocol for an open label: phase I trial within a cohort of foetal cell transplants in people with Huntington's disease.

Huntington’s disease is a progressive neurodegenerative disorder characterized by motor, cognitive and psychiatric symptoms. Currently, no disease-modifying therapies are available to slow or halt disease progression. Huntington’s disease is characterized by relatively focal and specific loss of striatal medium spiny neurons, which makes it suitable for cell-replacement therapy, a process involving the transplantation of donor cells to replace those lost due to disease. TRIal DEsigns for delivery of Novel Therapies in neurodegeneration is a phase I Trial Within a Cohort designed to assess safety and feasibility of transplanting human foetal striatal cells into the striatum of people with Huntington’s disease. A minimum of 18 participants will be enrolled in the study cohort, and up to five eligible participants will be randomly selected to undergo transplantation of 12–22 million foetal cells in a dose escalation paradigm. Independent reviewers will assess safety outcomes (lack of significant infection, bleeding or new neurological deficit) 4 weeks after surgery, and ongoing safety will be established before conducting each subsequent surgery. All participants will undergo detailed clinical and functional assessment at baseline (6 and 12 months). Surgery will be performed 1 month after baseline, and transplant participants will undergo regular clinical follow-up for at least 12 months. Evaluation of trial processes will also be undertaken. Transplant participants and their carers will be interviewed ∼1 month before and after surgery. Interviews will also be conducted with non-transplanted participants and healthcare staff delivering the intervention and involved in the clinical care of participants. Evaluation of clinical and functional efficacy outcomes and intervention costs will be carried out to explore plausible trial designs for subsequent randomized controlled trials aimed at evaluating efficacy and cost-effectiveness of cell-replacement therapy. TRIal DEsigns for delivery of Novel Therapies in neurodegeneration will enable the assessment of the safety, feasibility, acceptability and cost of foetal cell transplants in people with Huntington’s disease. The data collected will inform trial designs for complex intra-cranial interventions in a range of neurodegenerative conditions and facilitate the development of stable surgical pipelines for delivery of future stem cell trials. Trial Registration: ISRCTN52651778