Pig fetal pancreatic monolayers. A model of potential use in transplantation

Endocrine-rich monolayers of pig fetal pancreas that are free of fibroblasts have been established with the ultimate aim of providing guidelines for the culture of the human equivalent. The immunogenic potential of the monolayers--hence their capacity to be grafted--has also been analyzed. Fetuses ranging from 50 to 90 days were used, and, following digestion with collagenase (4 mg/ml, 15-20 min), the pancreatic suspension was plated onto tissue culture vessels containing RPMI 1640. The fetal calf serum concentration was kept low (5%) initially to inhibit fibroblast proliferation, but subsequently increased to 7%. Monolayers from a typical litter of 8-10 fetal pigs produced 6-8 x 10(8) viable epithelial cells by day 10 of culture, of which 75% were endocrine cells. This represents an 8-fold increase in a two-week period. The ratio of beta:alpha:delta:pancreatic polypeptide cells was 19:33:18:5. These monolayers synthesized both DNA, (pro)insulin and protein, and displayed increased insulin release when exposed to 10 mM theophylline, 10 mM Ca2+ and 1.3 microM 12-0-tetradecanoyl-phorbol-13-acetate. Static stimulation with 20 mM glucose however, did not elicit a response in insulin secretion. These cells displayed no reaction to allogeneic lymphocytes in a mixed lymphocyte culture, whereas freshly obtained porcine epithelial cells did. Methods may need to be found to increase the proportion of B cells in this enriched endocrine cell population. In general however, guidelines have been established that may be useful in developing a monolayer of human fetal pancreatic cells with the eventual aim of transplantation. The reduction in immunogenicity of the pig fetal pancreatic cells suggests that they too might be a potential source for transplantation.