HUMAN PANCREATIC BETA-CELL DEOXYRIBONUCLEIC ACID-SYNTHESIS IN ISLET GRAFTS DECREASES WITH INCREASING ORGAN DONOR AGE BUT INCREASES IN RESPONSE TO GLUCOSE STIMULATION IN-VITRO

Human pancreatic beta-cell proliferation may be crucial for the succes s of islet transplantation. The aim of this study was to test the hypo thesis that adult human beta-cells proliferate in vitro and in vivo an d respond with increased rates of replication to factors known to prom ote rodent islet-cell proliferation, i.e. glucose, human recombinant G H, and FCS. For this purpose, human islets were prepared from a total of 19 adult heart-beating organ donors and cultured for 48 h with or w ithout the additives described above. H-3-thymidine was added to the m edium during the last 60 min of culture. After immunohistochemical sta ining for insulin and autoradiography, the labeling index (LI; i.e. % of labeled beta-cells over total number of beta-cells) was estimated b y light microscopy. Islets also were transplanted under the kidney cap sule of normal or alloxan-diabetic nude mice. After 2 weeks, H-3-thymi dine was injected and the islet grafts prepared for determination of L I, as described above. Islets cultured at 5.6 mM glucose showed an inc reased beta-cell proliferation compared with islets cultured at 2.8 mM glucose (P < 0.05). However, culture at 11 mM glucose failed to furth er increase beta-cell proliferation. Addition of GH (1 mu g/ml) to the medium, in the presence of 1% FCS and 5.6 mM glucose, did not influen ce the rate of beta-cell proliferation. In islets transplanted to hype rglycemic nude mice, beta-cell proliferation was similar to that obser ved in islets grafted into normoglycemic nude mice. Proliferation, how ever, decreased with increasing organ donor age. This study shows that pancreatic beta-cells from adult man are able to proliferate both in vitro and in vivo. Moreover, beta-cells from adult human donors respon d with increased proliferation to glucose in vitro and show a decrease d proliferation in vivo with increasing donor age.