gms | German Medical Science

Introduction: MicroRNAs (miRNAs) are post-transcriptional regulators that bind to complementary sequences of target messenger RNAs. By affecting gene regulation, miRNAs are likely to be involved in most biologic processes, especially in regulation of cell division and cell differentiation.

Recently, we analyzed the gene expression in proliferating islets of Langerhans, identifying signaling pathways involved in Beta-cell proliferation. We extended our studies to a microRNA level to identify the regulation of these pathways.

Materials and methods: To stimulate beta-cell proliferation, c57/bl6 mice surgically underwent subtotal pancreatectomy. Proliferating cells were marked with bromodesoxyuridine. Eight mice in each group were either pancreatetomized or sham-operated (splenectomy). After 6 days the pancreatic remnant was excised and proliferating islets were selectively microdissected and compared with the non-proliferating islets of the sham-operated group. totalRNA was extracted and a differential expression analysis was performed between both groups using an Agilent microarray specific for microRNAs. Results were validated using qrtPCR in an independent series. Antagomirs specifically designed to influence microRNA activity of the identified microRNAs were used to regulate mRNA activity in insulinoma cell lines.

Results: Fifteen microRNAs were identified as being differentially expressed in proliferating compared to resting islets, 14 of which were up- and one being down-regulated in the pancreatectomized group. Of these, two miRNAs (mir-132 and mir-141) could be confirmed as being upregulated in proliferating islets via RT-PCR (Fold Change 3.2 and 1.6 respectively). Using antagomirs to regulate the activity of these to miRNAs, significant differences in the proliferation activity of insulinoma cells could be shown.

Conclusion: With this novel approach, we firstly identified the potential role of two miRNAs in proliferation of Beta-cells. We now aim to confirm these results in an animal model using similar antagomirs targeted to the mouse pancreas.

Once confirmed in vivo, an important step in understanding the regulation of beta-cell proliferation has been reached, which will enable us to develop strategies to expand beta cell mass in vivo or in vitro before islet transplantation.