Small Proline- rich Protein 1a Is A Key Downstream Effector Of Microrna-150 During Both Maladaptive Cardiac Remodeling In Mice And Human Cardiac Fibroblast Activation

Background & Objectives: MicroRNA-150 (miR-150) is conserved between rodents and humans, is significantly downregulated during heart failure (HF), and correlates with patient outcomes. We reported that miR-150 is protective during myocardial infarction (MI) in part by decreasing cardiomyocyte (CM) apoptosis and that proapoptotic small proline-rich protein 1a ( Sprr1a ) is a direct CM target of miR-150. We also showed that Sprr1a knockdown in mice improves cardiac dysfunction and fibrosis post-MI and that Sprr1a is upregulated in pathological mouse cardiac fibroblasts (CFs) from ischemic myocardium. However, the direct functional relationship between miR-150 and SPRR1A during both post-MI remodeling in mice and human CF (HCF) activation was not established. Methods & Results: Here, using a novel miR-150 knockout (KO); Sprr1a -hypomorphic ( Sprr1a hypo/hypo ) mouse model, we demonstrate that Sprr1a knockdown blunts adverse post-MI effects caused by miR-150 loss. MiR-150 KO; Sprr1a hypo/hypo mice also exhibit decreased profibrotic markers in the infarct areas of hearts as compared to miR-150 KO mice. Moreover, primary adult HCF studies reveal that SPRR1A is upregulated in hypoxia/reoxygenation-treated HCFs and is downregulated in HCFs exposed to the cardioprotective β-blocker carvedilol, which is inversely associated with miR-150 expression. Significantly, we show that the protective roles of miR-150 in HCFs are directly mediated by functional repression of profibrotic SPRR1A (See Figure). Conclusions: These findings delineate a pivotal functional interaction between miR-150 and SPRR1A as a novel regulatory mechanism pertinent to CF activation and ischemic HF.