Gestational diabetes mellitus (GDM) is associated with a five-fold increase in congenital heart defects. It is critical to determine the effects of GDM in vivo and high glucose in vitro on neonatal cardiomyocyte progenitor cell (nCPCs) regenerative capacity. We sought to investigate the roles of Mir-195 and its hypothesized target gene, EZH2 in GDM.

We subjected nCPCs in vitro to increasing glucose concentrations and assessed cellular proliferation, migration, and secretome quality. Our in vivo experiments involved injecting female mice with streptozocin and pairing them with non-diabetic male mice. Progenitor cells from resultant embryos at E14.5 were evaluated for viability, proliferation, ROS generation and apoptosis. mRNA expression levels of Mir-195 and EZH2 protein levels were detected using RT-qPCR and western blot analysis respectively.

Subjecting nCPCs in vitro to increased glucose concentration led to increased % cell death, decreased proliferation and expression of paracrine factors (Figure 1). Our in vivo models showed decreased expression of c-kit+/Lin- cells (0.2% v 2.8%; p<0.05) and ISL1+ cells (24% v 51%; p<0.05) and increased dihydroethidium positivity in DM-nCPCs at E14.5 (65% v 57%; p<0.05). Expression of Mir-195 was higher in DM-nCPCs (Figure 2) but EZH2 mRNA and protein expression levels were significantly decreased.

The viability of DM-nCPCs both in vivo and in vitro is decreased compared to NDM-nCPCs suggesting decreased postnatal regenerative capacity and poorer secretome quality. Mir-195 is associated with increased apoptosis and decreased proliferation of nCPCs via abrogation of the protective effects of EZH2. Mir-195 is a target for future therapeutics aimed at ameliorating GDM.