Regulated laminin-332 expression in human islets of Langerhans

In this article, the authors show that LN-332 is expressed in isolated human islets with labeling confined to endocrine cells. Labeling in isolated islets is granular but don’t colocalize with hormone secretory granules. LN- 332 is most abundant in cultured islets compared to freshly isolated islets and is found in a culture medium, which suggests that it is secreted by islets. When islets are exposed to interleukin (IL)-1B, expression and secretion of LN-332 increase compared to control. Inhibition of phosphatidylinositol 3-kinase (PI3-K) activity, inhibited culture and IL-1B-induced LN-332 expression in islets. These results show that LN-332, known to have some beneficial effect on B-cells in vitro, is produced and secreted by endocrine islet cells and is up-regulated by stress conditions such as culture and IL-1-exposure. Altogether, their observations can be considered as prerequisites necessary to hypothesize that the in vitro effect of LN-332 on B-cell secretion, viability, and replication is of physiological relevance as well.