Factors mediating the transdifferentiation of islets of Langerhans to duct epithelial-like structures.
We have previously shown that isolated islets embedded in type 1 collagen gel in the presence of a defined medium undergo transdifferentiation within 96 h to duct epithelial structures. The aim of this study was to identify the factors implicated in this process. Freshly isolated canine islets were embedded in type 1 collagen gel, Matrigel or agarose for up to 120 h and cultured in (i) Dulbecco's modified Eagle's medium (DMEM)/F12 plus cholera toxin (CT), (ii) medium CMRL1066 plus CT, (iii) CMRL1066 plus forskolin and (iv) CMRL1066 alone. At 16 h, intracellular levels of cAMP (fmol/10(3) islets) were increased in groups i-iii (642+/-17, 338+/-48, 1128+/-221) compared with group iv (106+/-19, P<0.01). Epithelial differentiation correlated with the total amount of intracellular cAMP measured over 120 h. Islet-epithelial transformation during the initial 36 h was associated with a wave of apoptosis which was followed by a wave of cell proliferation. During epithelial differentiation there was a progressive loss of all islet hormones and the concomitant expression of cytoskeletal proteins characteristic of duct epithelial cells. Islets in collagen and Matrigel demonstrated high rates of epithelial differentiation (63+/-2% and 71+/-4% respectively) compared with those in agarose gel (0+/-0%, P<0.001). Islets suspended in DMEM/F12 plus CT supplemented with soluble laminin or fibronectin did not undergo transformation. Prior incubation of freshly isolated islets with an integrin-binding arginine-glycine-aspartate motif-presenting synthetic peptide also reduced islet transformation. These studies confirm the biological potential of islets of Langerhans to differentiate to duct epithelial structures. cAMP-mediated signal transduction and an appropriate integrin-matrix interaction are necessary for this process to proceed.
Wang
R
R
Department of Surgery, McGill University, Montreal, Quebec, Canada.
Li
J
J
Rosenberg
L
L
D000818:Animals; D017209:Apoptosis; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D003094:Collagen; D024042:Collagen Type I / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism; D004285:Dogs; D004338:Drug Combinations; D004847:Epithelial Cells / Q000166:cytology; D016326:Extracellular Matrix Proteins / Q000502:physiology; D005260:Female; D007328:Insulin / Q000378:metabolism; D016023:Integrins / Q000502:physiology; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism; D007797:Laminin; D008297:Male; D010183:Pancreatic Ducts / Q000166:cytology*; D011509:Proteoglycans
D024042:Collagen Type I; D004338:Drug Combinations; D016326:Extracellular Matrix Proteins; D007328:Insulin; D016023:Integrins; D007797:Laminin; D011509:Proteoglycans; C059485:matrigel; D003094:Collagen; D000242:Cyclic AMP