A short course of high-dose cyclophosphamide induces long-term survival of intestinal allografts in mice.

Several transplant programs have recently added cyclophosphamide (CyP) to their immune suppression protocols in an attempt to reduce intestinal graft rejection rates. The present study was undertaken to confirm the benefits of this drug in a murine small bowel transplant model. A short course of monotherapy with CyP 20 mg/kg per dose resulted in a mean survival time (MST) of 17.5 +/- 3.6 days, compared with a MST of 7.5 +/- 0.7 days in the untreated controls (P < 0.01). Cyclosporin A (CsA) 30 mg/kg per day produced comparable survival rates when used as monotherapy (MST: 14.2 +/- 1.3 days) or in combination with CyP 20 mg/kg per dose (MST: 21.3 +/- 5.1 days). Treatment with high dose CyP (40 mg/kg per dose) completely prevented graft loss in 8 of 10 animals (MST: 72.5 +/- 5.3 days, P < 0.01). However, adding CsA abrogated the induction of long-term survival achieved by CyP alone (MST: 23 +/- 0.4 days). These data have important implications for the use of CyP in clinical transplantation.

Changes in the composition of serum bile acid as a predictor of small bowel allograft rejection in rats.

Composition of bile acid was studied as a noninvasive rejection marker after small bowel transplantation (SBT). Orthotopic SBT were performed in rats, and they were divided into four groups: group 1, sham-operated rats; group 2, recipients with isografts; group 3, recipients with allografts treated with FK506; and group 4, recipients with untreated allografts. On postoperative days (POD) 5 and 7, the graft histology, intraluminal bacterial overgrowth, individual bile acids concentration of the recipient serum and bile were examined. On POD 5, early histological findings of acute rejection were observed in group 4, and the ratio of secondary bile acids of this group were significantly higher than the other groups. The bile acid changes were enhanced by bacterial overgrowth on POD 7. The ratio of secondary bile acids changed in relation to acute rejection after SBT, suggesting that they can be useful for early diagnosis of acute SBT allograft rejection.

Reconstruction of the intestinal lymphatic drainage after small bowel transplantation.

BACKGROUND: The surgical procedure of small bowel transplantation normally results in complete disruption of the graft's lymphatic drainage. The present study was undertaken to determine the impact of lymphatic reconstruction (LR) on the outcome of intestinal grafting, using a microsurgical model that immediately restores lymphatic drainage. MATERIALS: Brown Norway (RT1n) intestinal grafts were orthotopically transplanted into Lewis (RT1(1)) rats either with LR (+LR) or without LR (-LR). Recipients were randomly allocated into the following groups: no treatment or cyclosporine (CsA) at a dose of 2, 5, or 10 mg/kg/day subcutaneously from postoperative day (POD) 0 to 6. RESULTS: There was morphological regeneration of lymphatics in the -LR group between 1-3 weeks as previously reported, whereas normal lymph flow was immediately restored in the +LR group. All untreated and CsA(2 mg)-treated allografts were rapidly rejected in both the +LR and -LR groups. In the groups treated with approximately 5 mg of CsA, five of six -LR animals died of chronic rejection between 38 and 86 days (mean survival time +/- SD: 76.7+/-21 days), while all +LR animals survived until death on POD 100 (P < 0.05). Histological features of mucosal damage found in -LR grafts were absent in the +LR grafts. All of the animals treated with 10 mg of CsA survived indefinitely. Sequential histology revealed mild rejection in -LR and +LR grafts on POD 45, but +LR animals had significantly higher body weight gains (POD 50: -LR: 117+/-12% vs. +LR: 136+/-4%, P < 0.01). LR did not affect donor cell migration and nutritional parameters. CONCLUSION: LR improves the long-term results of small bowel transplantation resulting in better survival rates, less mucosal damage due to chronic graft rejection, and greater weight gain. We conclude that impairment of lymph flow may contribute to poor outcomes when standard surgical techniques are used for small bowel transplantation.

Rat-to-mouse small bowel xenotransplantation: a novel model for studying acute vascular and hyperacute xenograft rejection and xenogenic cell migration.

The present study was undertaken to establish a rat-to-mouse vascularized small bowel xenotransplantation model to study acute vascular and hyperacute xenograft rejection, and xenogenic cell migration. Lewis rat small bowel grafts were transplanted heterotopically to group 1, Balb/c mice, and group 2, Balb/c mice pre-sensitized with a donor spleen cell injection. The grafts were examined by serial pathology and flow cytometry. In group 1, acute vascular rejection was present by the 5th post-operative day (POD). Immunohistology showed a strong endothelial deposition of IgG, IgM and C3, associated with a minimal lymphocytic infiltrate. There was a vigorous cell migration from the recipient to the graft, in which recipient origin cells comprised 80.1+/-6.9% of the graft mesenteric lymph node by POD 3. However, there was almost no cell migration from the graft to the recipient. The intestinal xenografts in the group 2 showed massive hemorrhage, fibrin deposition, vascular congestion and thrombosis 60 min after transplantation. IgG and C3 were present on the endothelium as early as 1 min after reperfusion. The vigorous humorally-mediated vascular damage and rapid elimination of donor cells seen with intestinal xenograft rejection are distinct from the usual picture of allograft rejection. Hyperacute rejection can be induced by recipient pre-sensitization with donor spleen cells. The potential advantages of studying xenotransplantation in this model include: (1) the wide range of immunologic reagents available for mice; (2) the opportunity to study the progression of vascular damage easily by performing serial biopsies in the same animal; and (3) the opportunity to study, in vivo, two-way cellular response by examining cell trafficking in the mesenteric lymph nodes.

Extrinsic sympathetic reinnervation after intestinal transplantation in rats.

Although extrinsic denervation is inevitable after intestinal transplantation and leads to poor intestinal function, little is known about the occurrence of extrinsic reinnervation. In this study, extrinsic sympathetic reinnervation was investigated morphologically following syngeneic intestinal transplantation performed on male Lewis strain rats. At 1, 3, 6, 9, 15, and 27 weeks after transplantation, the graft mesenteric arteries and their branches in the intestinal wall were histochemically examined by a glyoxylic acid method demonstrating perivascular sympathetic nerve fibers. At 3 weeks after transplantation, extrinsic sympathetic reinnervation was recognized in the graft mesenteric arteries, where it traversed the arterial anastomosis and extended along the course of the mesenteric arteries from proximal to distal. The degree of reinnervation in the mesenteric arteries was similar to the results obtained in the simple denervation model. The transplanted intestinal tract itself was sympathetically denervated for at least 9 weeks after transplantation, and reinnervation was not recognized until 15 weeks after transplantation. Reinnervation extended into the intestinal wall in every preparation, and the enteric nerves began to be reinnervated at 27 weeks after transplantation, but the density was still at a low level and complete extrinsic reinnervation of the graft would seem to require a much longer time to reestablish itself.