In utero transplantation of haemopoietic stem cells

A murine model of graft-vs-host disease after in utero hematopoietic cell transplantation

PURPOSE

Graft-vs-host disease (GvHD) is a known complication of in utero bone marrow transplantation. However, GvHD has been difficult to study owing to frequent fetal demise. We describe the first consistent murine model of GvHD with postnatal survival after in utero hematopoietic cell transplantation.

METHODS

A 50/50 mixture of bone marrow and splenocytes (10(6)) from 6-week-old C57/BL6 (H2-b) mice was injected intraperitoneally into Balb/c (H2-d) fetuses at e14 to 16. Live born pups were followed for clinical GvHD. Peripheral blood and hematopoietic organ chimerism was confirmed by flow cytometry and polymerase chain reaction. Organ samples were isolated for histology.

RESULTS

Twenty-seven (75%) of 36 surviving pups displayed clinical GvHD by 2 weeks compared with 9 developmentally normal pups. Mean difference in weight between the 2 groups was 2.9 g at 7 days and 5.2 g at 14 days of life (P < .0001). All 27 pups with clinical GvHD and 1 normal-appearing pup had blood chimerism ranging from 1.5% to 65%. Eight of the 9 normal-appearing pups had 0% chimerism. Histologic analysis revealed findings of GvHD in liver, spleen, small intestine, and skin specimens of only chimeric pups.

CONCLUSIONS

A consistent murine model of GvHD can be achieved after in utero transplantation of major histocompatibility complex-mismatched bone marrow and splenocytes. Future studies will use this model to examine approaches to prevent GvHD after in utero stem cell transplantation.

Bone marrow cell transfer into fetal circulation can ameliorate genetic skin diseases by providing fibroblasts to the skin and inducing immune tolerance

Recent studies have shown that skin injury recruits bone marrow-derived fibroblasts (BMDFs) to the site of injury to accelerate tissue repair. However, whether uninjured skin can recruit BMDFs to maintain skin homeostasis remains uncertain. Here, we investigated the appearance of BMDFs in normal mouse skin after embryonic bone marrow cell transplantation (E-BMT) with green fluorescent protein-transgenic bone marrow cells (GFP-BMCs) via the vitelline vein, which traverses the uterine wall and is connected to the fetal circulation. At 12 weeks of age, mice treated with E-BMT were observed to have successful engraftment of GFP-BMCs in hematopoietic tissues accompanied by induction of immune tolerance against GFP. We then investigated BMDFs in the skin of the same mice without prior injury and found that a significant number of BMDFs, which generate matrix proteins both in vitro and in vivo, were recruited and maintained after birth. Next, we performed E-BMT in a dystrophic epidermolysis bullosa mouse model (col7a1(-/-)) lacking type VII collagen in the cutaneous basement membrane zone. E-BMT significantly ameliorated the severity of the dystrophic epidermolysis bullosa phenotype in neonatal mice. Type VII collagen was deposited primarily in the follicular basement membrane zone in the vicinity of the BMDFs. Thus, gene therapy using E-BMT into the fetal circulation may offer a potential treatment option to ameliorate genetic skin diseases that are characterized by fibroblast dysfunction through the introduction of immune-tolerated BMDFs.

Prenatal transplantation of cytokine-stimulated marrow improves early chimerism in a resistant strain combination but results in poor long-term engraftment

OBJECTIVE

In the absence of immunodeficiency, only microchimerism (<0.1%) has been achieved in human fetal recipients or nonhuman primates following in utero hematopoietic cell transplantation (IUHCT). We hypothesized that enhanced long-term engraftment might be more reliably achieved in microchimeric systems if higher levels of chimerism existed during development of adaptive immunity. To evaluate this hypothesis, we stimulated the donor cells with vascular endothelial growth factor (VEGF) and stem cell factor (SCF) prior to IUHCT in a chimerism-resistant murine strain combination.

METHODS

Donor Balb/c marrow was cultured in media with or without VEGF and SCF supplementation for 12 hours prior to IUHCT into B6 fetuses at 14 days postcoitum (dpc). Donor cell phenotype, homing, and chimerism were assessed at short and long-term time points and transplanted animals received skin allografts at 8 weeks.

RESULTS

In pretreated allogeneic recipients, early chimerism rates were more than double that of controls (71% vs 33%, p = 0.01). These differences were associated with higher numbers of pretransplant donor cell colony-forming cells without change in donor cell homing. Despite prolonged skin allograft survival for pretreated recipients compared with controls (mean survival = 20.8 vs 8.2 days, p < 0.001), long-term engraftment was unchanged.

CONCLUSIONS

These findings demonstrate that higher levels of early chimerism in recipients of cytokine-stimulated marrow result in improved short-term chimerism and tolerance. Future studies are needed to confirm the existence of a "threshold" level of chimerism necessary to sustain long-term engraftment.

Human Fetal Mesenchymal Stem Cells as Vehicles for Gene Delivery

First-trimester fetal blood contains a readily expandable population of stem cells, human fetal mesenchymal stem cells (hfMSCs), which might be exploited for autologous intrauterine gene therapy. We investigated the self-renewal and differentiation of hfMSCs after transduction with onco-retroviral and lentiviral vectors. After transduction with either a MoMuLV retrovirus or an HIV-1-based lentiviral vector carrying the ss-galactosidase and green fluorescent reporter gene, respectively, transgene expression, self-renewal, and differentiation capabilities were assessed 2 and 14 weeks later. Transduction with the lentiviral vector resulted in higher efficiencies than with the MoMuLV-based vector (mean, 97.7 +/- 1.4% versus 80.2 +/- 5.4%; p = .02). Transgene expression was maintained with lentiviral-transduced cells (94.6 +/- 2.6%) but decreased over 14 weeks in culture with onco-retroviral-transduced cells (48.3 +/- 3.9%). The self-renewal capability of these cells and their ability to undergo osteogenic, adipogenic, and myogenic differentiation was unimpaired after transduction with either vector. Finally, clonal expansion of lentivirally modified cells was expanded over 20 population doublings with maintenance of multiline age differentiation capacity. These results suggest that hfMSCs may be suitable targets for ex vivo genetic manipulation with onco-retroviral or lentiviral vectors without affecting their stem cell properties.

Isolation and therapeutic potential of human haemopoietic stem cells

The haemopoietic stem cell (HSC) has long been regarded as an archetypal, tissue specific, stem cell, capable of completely regenerating haemopoiesis after myeloablation. It has proved relatively easy to harvest HSC, from bone marrow or peripheral blood. In turn, isolation of these cells has allowed therapeutic stem cell transplantation protocols to be developed, that capitalise on their prodigious self renewal and proliferative capabilities. Ex vivo approaches have been described to isolate, genetically manipulateand expand pluripotent stem cell subsets. These techniques have been crucial to the development of gene therapy, and may allow adults to enjoy the potential advantages of cord blood transplantation. Recently, huge conceptual changes have occurred in stem cell biology. In particular, the dogma that, in adults, stem cells are exclusively tissue restricted has been questioned and there is great excitement surrounding the potential plasticity of these cells, with the profound implications that this has, for developing novel cellular therapies. Mesenchymal stem cells, multipotent adult progenitor cells and embryonic stem cells are potential sources of cells for transplantation purposes. These cells may be directed toproduce HSC, in vitro and in the future may be used for therapeutic, or drug development, purposes.

Influence of intrauterine injection of rat fetal hepatocytes on rejection of rat liver transplantation

AIM: To investigate the influence of immune tolerance induced by intrauterine exposure to fetal hepatocytes on liver transplantation in the adult rat.

METHODS: LOU/CN rat fetal hepatocytes were injected into the fetuses of pregnant CHN rats (14-16 days of gestation). At 7-9 weeks of age, the surviving male rats received orthotopic liver transplantation (OLT) from male LOU/CN donors and the survival period was observed and monitered by mixed lymphocyte reaction assay and cytotoxicity test.

RESULTS: (1) A total of 31 pregnant CHN rats with 172 fetuses received fetal hepatocytes from LOU/CN rats via intrauterine injection. Among them, thirteen pregnant rats showed normal parturition, with 74 neonatal rats growing up normally. (2) The mean survival period after OLT in rats with fetal exposure to fetal hepatocytes was 32.1 ± 3.7 days, which was significantly different from the control (11.8 ± 2.3 days, P < 0.01) in rats without fetal induction of immune tolerance. (3) Mixed lymphocyte proliferation assays yielded remarkable discrepancies between the groups of rats with- or without fetal exposure to fetal hepatocytes, with values of 8411 ± 1361 and 22473 ± 1856 (CPM ± SD, P < 0.01) respectively. (4) Cytotoxicity assays showed values of 21.2 ± 6.5% and 64.5 ± 7.2% (P < 0.01) in adult rats with or without fetal induction of immune tolerance.

CONCLUSION: Intrauterine injection of fetal hepatocytes into rat fetuses can prolong the survival period of liver transplant adult male rats recipients, inducting immune tolerance in OLT.

A glance into somatic stem cell biology: basic principles, new concepts, and clinical relevance

Somatic stem cells are undifferentiated cells with a high capacity for self-renewal that can give rise to one or more specialized cell types with specific functions in the body. Profound characterization of these cells has been difficult due to the fact that their frequency in different tissues of the body is extremely low; furthermore, their identification is not based on their morphology but on immunophenotypic and functional assays. Nevertheless, significant advances in the study of these cells at both cellular and molecular levels have been achieved during the last decade. The majority of what we know concerning somatic stem cell biology has come from work on hematopoietic stem cells. More recently, however, there has been a great amount of information on neural and epithelial stem cells. The importance of stem cell research has gone beyond basic biology and is currently contributing to the development of new medical approaches for treatment of hematologic, neurologic, autoimmune, and metabolic disorders (cellular therapy).