The effect of antilymphocyte serum on fetal rat intestine transplanted as free subcutaneous homografts

Isolation of human foetal myoblasts and its application for microencapsulation

Foetal cells secrete more growth factors, generate less immune response, grow and proliferate better than adult cells. These characteristics make them desirable for recombinant modification and use in microencapsulated cellular gene therapeutics. We have established a system in vitro to obtain a pure population of primary human foetal myoblasts under several rounds of selection with non-collagen coated plates and identified by desmin staining. These primary myoblasts presented good proliferation ability and better differentiation characteristics in monolayer and after microencapsulation compared to murine myoblast C2C12 cells based on creatine phosphokinase (CPK), major histocompatibility complex (MHC) and multi-nucleated myotubule determination. The lifespan of primary myoblasts was 70 population doublings before entering into senescent state, with a population time of 18–24 hrs. Hence, we have developed a protocol for isolating human foetal primary myoblasts with excellent differentiation potential and robust growth and longevity. They should be useful for cell-based therapy in human clinical applications with microencapsulation technology.

Engraftment of human early kidney precursors

Kidney transplantation has been one of the major medical advances of the past 30 years; however, it is becoming increasingly apparent that the supply of organs is limited and will not improve with current medical practice. This review summarizes recent data whereby precursors of the adult kidney found in embryos and fetal tissue have been grafted into murine hosts to examine their feasibility as an alternative source for renal transplantation. When obtained at specific time points during human gestation, kidney precursors meet with specific demands; they grow tremendously, differentiate exclusively along the nephric lineage with no evidence of malignant transformation, become vascularised, to a larger extent, by host vessels, and produce urine in host animals. In addition, they exhibit decreased immunogenicity compared to adult counterparts. Organogenesis is best achieved when utilizing early undifferentiated progenitors rather than later-gestation kidneys. Nevertheless, in order for these transplants to be applicable for human transplantation, both a functional urinary anastomosis and derivation of blood supply sufficient to correct biochemical abnormalities remain to be established.

Embryonic committed stem cells as a solution to kidney donor shortage

The number of human kidney transplants has increased rapidly in recent years, but the need greatly exceeds organ availability. Induction of appropriate kidney differentiation and growth from stem or progenitor cell populations represents an attractive option to combat chronic kidney donor shortage. In an analogy to haematopoietic stem cells, which are much more efficient in giving rise to blood than to other cell types, if any at all, renal stem cells could afford an unlimited source for regenerating nephrons. While a single nephrogenic stem cell has not been characterised, indirect evidence suggests that a renal stem cell population is contained within the metanephric mesenchyme, which along with a branch of the Wolffian duct represents the direct precursor of the mature kidney. Human tissue fragments derived from these developing precursors can regenerate renal structures when grafted into mice. Moreover, recent data pinpoints a window of time in human and pig kidney development that may be optimal for transplantation into mature recipients. 'Window' transplants are defined by their remarkable ability to grow, differentiate and undergo vascularisation, achieving successful organogenesis of urine-producing miniature kidneys with no evidence of transdifferentiation into non-renal cell types, lack of tumourigenicity and reduced immunogenicity compared with adult counterparts. In contrast, 'non-window' transplants (earlier or later in gestation) can form teratomas or are more prone to immune rejection and are less suitable for organogenesis. Hopefully, the use of stage-specific early human and porcine kidney precursors to cultivate mature kidney cells in vivo, possibly in conjunction with other modalities of stem cell technology and tissue engineering, will prove valuable to sustain life in patients with failing kidneys.

Allogeneic fetal small bowel graft in pigs treated with cyclosporin A

BACKGROUND

The functional integrity of transplanted fetal intestine was proven in rodents. The authors examined the morphology and development of intraperitoneally transplanted fetal intestine under cyclosporin A (CsA) monotherapy in a large mammal.

METHODS

Allogeneic fetal intestinal grafts were transplanted intraperitoneally in pigs. The graft was wrapped in omentum. Thirteen recipients received grafts harvested at 60 days of gestation and 5 at 105 days of gestation. All recipients received 25 mg/kg/d CsA. CsA blood levels were measured at the end of the study. The development of the grafts was assessed by inspection and histology studying revascularization, maturation, and immune rejection.

RESULTS

All grafts developed neovascularization. The intestinal wall in the 105-day-old group was thick enough to lead to complete mucosal destruction, whereas the 60-day-old group showed viable mucosa. All grafts induced an immune rejection. This immune response was correlated with the CsA blood level. The graft was destroyed within 15 days when CsA trough level was below 70 ng/mL, had a subacute rejection with villi atrophy when CsA trough level ranged from 70 to 150 ng/mL, and had a good appearance in spite of mild blunting of villi when CsA trough level was over 150 ng/mL.

CONCLUSION

Allogeneic fetal intestinal transplantation from 60-day-old embryos in pig achieved successful graft.

Current status of small-bowel transplantation

Patients who have lost such a large portion of their small bowel that they permanently require total parenteral nutrition for survival would greatly benefit by receiving a small-intestinal transplant. Over the past two decades, many experimental studies have delineated the specific problems surrounding small-bowel transplantation and provided strategies for their control. Control of rejection, the most difficult problem, may be achieved with a combination of cyclosporine, azathioprine, prednisone, antithymocyte globulin, and monoclonal antibodies. The threat of graft-versus-host disease originating from the allogeneic lymphatic tissues in the allograft is abolished by in vitro x-irradiation of the cold, nonperfused graft with 1000 rads. Monitoring of the intestinal allograft is possible with the combination of a function test (maltose absorption, glucose absorption, or any other function test) and repeated graft biopsy. Effective short-term preservation of small-bowel segments for up to 18 h is possible by intravascular flushing with a balanced electrolyte solution containing 3% fructose and by subsequent hypothermic storage. Clinical small-bowel transplantation is certainly not an imminent therapeutic tool. However, clinical trials in highly selected patients could be envisioned on the basis of our present understanding of small-bowel transplantation and of transplantation biology in general, and in view of the clinical successes achieved with duodenal grafts transplanted in conjunction with pancreatic grafts.

Fetal allograft survival in immunocompetent recipients is age dependent and organ specific

This study explores whether fetal allograft survival is age dependent and organ specific. Fetal rat tissue (renal, gonadal, hepatic) from the third trimester of gestation (days 15-21) was transplanted into 306 outbred adult rats for 10-30 days. Grafts were studied by morphometric and histologic analysis. Ten days after implantation, renal tissue (N = 75) from late gestation (days 19-21) showed no increase in size. In contrast, 17-day fetal grafts (N = 20) grew 6.8 +/- 3.4 times,* while 15-day fetal grafts (N = 28) grew 17.5 +/- 6.1* times. (The symbol "*" indicates p less than 0.05, compared to original size). Twenty days after implantation, these 15-day fetal grafts (N = 20) grew 48.8 +/- 17.7* times. Ten days after grafting, the younger fetal tissue showed excellent maturation of renal elements and no sign of rejection; older fetal grafts had poor renal architecture and a dense lymphocytic infiltrate. The 15-day fetal gonadal tissue (N = 18) showed a moderate 10.6 +/- 3.2* increase in size while the 15-day hepatic grafts (N = 16) were regularly rejected within 10 days. Selected fetal allografts from early in the third trimester can not only survive but can grow and mature in an immunocompetent recipient. This fetal graft growth appears to be both age dependent and organ specific. The use of fetal organs may broaden the potential pool for transplantation. However, further studies are needed to define the ontogeny of graft acceptance.

Fetal rat intestinal transplantation: cryopreservation and cyclosporin A

Successful preservation of small bowel by cryobiologic techniques would increase the feasibility of intestinal transplants. Immunosuppression by Cyclosporin A (CyA) has also increased interest in intestinal transplantation. We have investigated the effect of cryopreservation and immunosuppression in fetal rat intestinal transplantation. Segments of fetal bowel implanted isogeneically into the paravertebral gutter of young rats were found to grow in a high percentage of animals (53% to 100%). Segments frozen to -20 degrees C or -40 degrees C at two rates of cooling, grew isogeneically (50% to 89%), demonstrating the feasibility of cryopreservation. Histologic examination of this bowel showed preservation of structure. When these segments were cooled and implanted allogeneically, no immunosuppressive effect was found. Segments protected by daily CyA administration grew. No synergistic effect was seen by associating CyA and cryopreservation. These experiments suggest the possibility of creating fetal small bowel long-term banking.

Avascular transplantation of small bowel in newborn piglets

Segments of small bowel of newborn piglets were isolated and wrapped in omentum as free autotransplants. After initial necrosis, they regenerate either completely, or at least their muscular layer is restored. As there is a lot of inflammatory reaction in most of the grafts, the conclusion is drawn that either preexisting infection, or autoaggressive reactions are responsible for this. Homografts behave like autografts in the beginning, their structures being restored, but are all rejected by the sixth week. Immaturity of the immunologic system in the newborn may be the reason for this late rejection.