LONG-TERM CULTURE OF HUMAN PANCREATIC-ISLETS IN AN EXTRACELLULAR-MATRIX - MORPHOLOGICAL AND METABOLIC EFFECTS

In this experiment, various conditions for embedding cultures of human pancreatic islets in type I collagen gel were studied in an attempt t o maintain the highly differentiated functions of islet cells and part icularly insulin secretion over a long period of time. The islets isol ated by a collagenase digestion technique were plated either on or wit hin the collagen gel and refed with either Eagle's minimum essential m edium (5.5 mM D-glucose) or RPMI 1640 medium (11 mM D-glucose) supplem ented with 10% FCS and antibiotics. The comparison between the two cul ture media showed that embedded islets cultured in RPMI had a higher b asal insulin secretion rate, survived longer than their MEM counterpar ts, but exhibited impaired response to an acute glucose test contrasti ng thus with islets cultured in MEM. The secretory behaviour of islets was also related to the different morphological modifications occurri ng during culture. Islets directly embedded within the collagen gel mo re or less maintained their spherical structure and highest secretory capacities. When overlaid with a second layer of collagen, well establ ished monolayers of human islet cells grown on collagen underwent a gr adual and complete reorganization into a three-dimensional islet-like structure with a striking reinforcement of their secretory activity. B oth cultures were able to survive more than 8 weeks, thus proving the usefulness of such a new model for long-term culture. In contrast, sta ndard cultures on culture treated plastic dishes on which islets cells rapidly established wide monolayers, exhibited a rapid and definitive decline in insulin secretion with a survival not exceeding 14 days. I n the light of these different culture conditions, possible mechanisms responsible for disturbance of hormonal release and their implication s for in-vitro study of isolated islets functions are discussed. In co nclusion, this work is a new example of the permissive effects of coll agen matrices on the establishment or maintenance of tissue-like struc tures in vitro, suggesting the definition of a new model for the study of human pancreatic islets in long-term culture.