ABSTRACT
Extracellular matrix proteins are known to mediate, through integrins, cell adhesion and are involved in a number of cellular processes, including insulin expression and secretion in pancreatic islets. We investigated whether expression of some extracellular matrix proteins were implied in islets-like structure formation, named pseudoislets. For this purpose, we cultured the ß-cell line, RINm5F, during 1, 3, 5 and 7 days of culture on treated or untreated culture plate to form adherent cells or pseudoislets and analysed insulin, collagen IV, fibronectin, laminin 5 and ß1-integrin expression. We observed that insulin expression and secretion were increased during pseudoislets formation. Moreover, we showed by immunohistochemistry an aggregation of insulin secreting cells in the centre of the pseudoislets. Peripheral ß-cells of pseudoislets did not express insulin after 7 days of culture. RT-PCR and immunohistochemistry studies showed a transient expression of type IV collagen in pseudoislets for the first 3 days of culture. Study of fibronectin expression indicated that adherent cells expressed more fibronectin than pseudoislets. In contrast, laminin 5 was more expressed in pseudoislets than in adherent cells. Finally, expression of ß1-integrin was increased in pseudoislets as compared to adherent cells. In conclusion, laminin 5 and collagen IV might be implicated in pseudoislets formation whereas fibronectin might be involved in cell adhesion. These data suggested that extracellular matrix proteins may enhance the function of pseudoislets.
Subject(s)
Extracellular Matrix Proteins/physiology , Islets of Langerhans/cytology , Islets of Langerhans/physiology , Spheroids, Cellular/cytology , Spheroids, Cellular/physiology , Animals , Cell Adhesion Molecules/genetics , Cell Adhesion Molecules/metabolism , Cell Culture Techniques/methods , Cells, Cultured , Collagen Type IV/genetics , Collagen Type IV/metabolism , Collagen Type IV/physiology , Extracellular Matrix Proteins/genetics , Extracellular Matrix Proteins/metabolism , Fibronectins/genetics , Fibronectins/metabolism , Gene Expression , Insulin/genetics , Insulin/metabolism , Islets of Langerhans/metabolism , Rats , Spheroids, Cellular/metabolism , KalininABSTRACT
Anionic glucophospholipids were recently reported as a new family of tubule-forming lipids. We report here investigations on the structure of nanotubules made from a glucophospholipid with a mixed fluorocarbon-hydrocarbon hydrophobe, using freeze fracture and cryo-transmission electron microscopy (TEM) and X-ray and neutron small angle scattering (SAXS, SANS). The hollow and regularly shaped tubules are very thin: they have an external radius of 140 Å and an internal radius of 35 Å on the average. Their 105 Å-thick wall appears to consist in three bilayers in which the glucophospholipid molecules are probably in a tilted and/or interdigitated configuration. Upon heating these nanotubes convert reversibly into vesicles; transformation is complete at 60 degrees C. Copyright 1999 Academic Press.
