Functional and morphological differentiation of fetal porcine islet-like cell clusters after transplantation into nude mice.

By using a previously described culture technique for the midgestational fetal porcine pancreas, islet-like cell clusters with a Beta-cell frequency of approximately 5% have been produced in large numbers. These islet-like cell clusters were transplanted beneath the kidney capsule to either normoglycaemic or alloxan-treated nude mice. The grafts consistently failed to cure the alloxan-treated mice immediately after implantation, however, normoglycaemia was restored in a majority of the mice within 2 months after transplantation and in all animals after 4 and 6 months. Indeed, the insulin released from the transplanted fetal Beta cells was able to normalize the serum glucose concentration at porcine levels (4-5 mmol/l) rather than at the level maintained in mice (8-10 mmol/l). In the cured mice there was a normal secretory response to glucose in the grafts as evidenced by normal glucose profiles during intravenous glucose tolerance test and a biphasic insulin response to high glucose when perfusing the graft bearing kidney. On the other hand, in the normoglycaemic animals the second phase faded before the glucose stimulus had been withdrawn. Two months after transplantation the endocrine cells were arranged so that the endocrine non-Beta cells were randomly scattered among a majority of Beta cells. The cell replication of the Beta cells, measured by 3H-thymidine incorporation, was within the lower range of that seen in the native islets of adult mice. No major differences between the controls and the alloxan-treated animals were observed in this respect. Cultured islet-like cell clusters had high rates of glucose utilization, paralleled by low rates of glucose oxidation, compared with adult mouse islets.(ABSTRACT TRUNCATED AT 250 WORDS)