Studies of composite grafts of fetal pancreas (FP) and fetal liver (FL) in the streptozotocin-induced diabetic rat.

A hepatotrophic effect of pancreatic islets on co-transplanted hepatocytes has been described recently by Ricordi et al. We investigated a possible reciprocal effect of co-transplanted fetal liver (FL) on fetal pancreas (FP) isografted into streptozotocin diabetic rats. FL was co-transplanted with FP in three sites: the new intramural small bowel (ISB) site, the conventional renal subcapsular (RSC) site, and the historically inhospitable intramuscular (IM) site. Overall, as compared to grafts of FP alone, composite FP/FL grafts consistently provided earlier restoration of normoglycemia in streptozotocin diabetic recipients (24 +/- 8 vs. 67 +/- 43 days P = 0.001). The proportion of recipients rendered normoglycemic and the clearance of glucose was site-dependent. For FP and FP/FL recipients respectively, the ISB site resulted in 100% normoglycemia in both groups (19/19 and 6/6), the RSC site resulted in 71% (5/7) and 40% (2/5) and the IM site resulted in 14% (1/7) and 67% (6/9). In normoglycemic recipients, glucose clearance was normal or supraphysiologic except for the RSC site. Composite isografts brought about normoglycemia in 75% (6/8) of recipients treated with beta-cell toxic doses of cyclosporine that prevented reversal of diabetes in recipients of FP alone. Co-transplantation of FL benefits FP through paracrine mechanisms mediated by unknown factor(s). Thus, as compared to grafts of FP alone, composite FP/FL grafts established normoglycemia more rapidly, mitigated cyclosporine toxicity and corrected diabetes when transplanted in the small bowel site. There are several mediators that may be responsible for these paracrine effects between the liver cells and the pancreas. IGF-1 elaborated by FL is the most likely trophic factor.(ABSTRACT TRUNCATED AT 250 WORDS)