Mechanotransduction in human and mouse beta cell lines: reliable models to characterise novel signalling pathways controlling beta cell fate

Background and aim: in recent years, there are evidences suggesting that the interaction between cells and extracellular environment has a pivotal role in tissue differentiation and fate, both in physiological and pathological conditions. Moreover, it has become clear that not only chemical composition, but also physical properties of the extracellular matrix (ECM) affect cell behaviour. The cell ability to respond to changes in their physical environment is known as mechanotransduction and it is prevalently mediated by heterodimeric transmembrane receptors of the family of integrins. Like other tissues, β-cells behaviour is influenced by cell-ECM interaction and there is significant evidence that β-cells depend on extracellular cues to replicate, survive and differentiate. However, the architecture and physical interactions within and surrounding the islets are not completely understood. Thus, aim of the proposed research was to evaluate the mechanotrasductive signalling components in the islets of Langerhans. Material and methods: we used metal oxide layers with tailored nanoscale roughness to fabricate scaffolds that mimic ECM morphology. Isolated human islets grew on these different substrates for 20 days and mechanotrasductive signalling components were evaluated by proteomic analysis; nuclear architecture and focal adhesion were assessed by indirect immunofluorescence. Results: we found that nanostructured substrates cause a relocalization of focal adhesion which may influence protein expression. Proteomic analysis confirmed this hypothesis and showed an up-regulation of focal adhesion molecular components (GO:0005925) and proteins important for actin polymerization (GO:0005856) like TNS1, ARPC2, ARPC1B, DYNLL1, DNAH14, KANK2 protein complexes. The modifications in actin cytoskeleton cause a tension on the nuclear envelope which in turn modulates the program of gene transcription and cellular modelling. Accordingly, we found an up-regulation of the proteins involved in the control of nuclear architecture (GO:0031891) and also a modification of nuclear shape. Conclusion: understanding the mechanotrasductive signalling system may offer a unique possibility to identify molecular or pharmacological targets to prevent and treat diabetes mellitus.