Driving the pancreatic β-cell function through nanoscale features: the influence of nuclear mechanotransduction

Background and aims: nowadays, to accelerate the development of cell-replacement strategies in diabetes, there is a desperate need to understand mechanisms and stimuli regulating the β-cell development and function. We have recently demonstrated that the extracellular nanotopography promotes β-cell survival, differentiation, and function through the activation of a mechanotransductive pathway, however, the underlying molecular mechanisms need to be further investigated. In the last years, we focused on how mechanical forces might impact the nuclear organization, and thus the transcriptional and translational activities in pancreatic β-cells. Materials and methods: human isolated islets were cultured for 20 days on nanostructured zirconia substrates with a controllable ECM-like roughness (ns-ZrOx), while flat zirconia substrates were used as controls (flat-ZrO2). The activation of nuclear mechanotransduction was assessed by super-resolution fluorescence microscopy and western blot technique and confirmed by shot-gun proteomic. Results: we found that the nanotopography, by reducing the cytoskeletal tension, modulates the nuclear shape and architecture (nuclear area and circularity; p<0.001 ns-ZrOx vs flat-ZrO2). These modifications are paralleled by the spatial reorganization of the nuclear lamina, and a shift of lamin isoforms in the islets grown on the nanosubstrates (p<0.05 ns-ZrOx vs flat-ZrO2). Changes in nuclear lamina might affect the access of transcription factors to the nucleus leading to changes in the transcriptional and translational activities. In accordance, the proteomic analysis revealed the upregulation of chromatin-associated proteins (GO:0031497), RNA binding proteins (GO:0003723), spliceosome (GO:0005681) and heterogeneous nuclear ribonucleoprotein (GO:0030529) complexes in the islets grown on the nanostructure (p<0.05 ns-ZrOx vs flat-ZrO2). Furthermore, we observed that the nanostructure modulates the expression of YAP/TAZ, a soluble transcription factor strictly controlled by mechanical forces and critically involved in the regulation of the β-cell fate (p<0.05 ns-ZrOx vs flat-ZrO2). Conclusions: our data indicate for the first time that the extracellular nanotopography controls the transcriptional and translational activities of pancreatic β-cells, further supporting the hypothesis of a mechanical-induced β-cell reprogramming. These findings provide a better understanding of the mechanotransductive-regulatory mechanisms in β-cells, revealing novel pathways and molecular effectors that may be helpful for designing engineered substrates that can improve the efficacy of replacing therapies in diabetes.