MiR-145-5p modulates collagen production and fibroblast behaviour after cardiac injury partially via COL5A1

In contrast to humans, zebrafish hearts after cryoinjury undergo transient fibrotic scarring that subsequently resolves and renews with functional cardiomyocytes. To understand the molecular mechanisms underlying cardiac scarring and fibrotic resolution in zebrafish, we investigated cardiac transcriptomic responses in zebrafish at 14 days post-cryoinjury. Principal component analyses revealed distinct transcriptome clusters corresponding to healthy and injured hearts, highlighting significant changes during cardiac regeneration. Gene set enrichment analyses indicated that extracellular matrix organization and inflammatory response pathways were activated in cryoinjured hearts, while mitochondrial organization and oxidative phosphorylation pathways were downregulated. Notably, miR-145-5p was downregulated and col5a1 upregulated in the cryoinjured hearts, contrasting with the expression patterns of miR-145-5p and COL5α1 in the left ventricles of ischemic cardiomyopathy patients. Prediction of miRNA-mRNA interaction and a dual luciferase assay identified COL5A1 as a target of miR-145-5p. Inhibition of miR-145-5p in human cardiac fibroblasts increased COL5A1 and α-SMA, decreased COL1A, and stimulated fibroblast differentiation, proliferation, and migration. Conversely, overexpression of miR-145-5p led to the opposite effects. Downregulation of COL5A1 suppressed fibroblast proliferation and migration, which could be rescued by inhibition of miR-145-5p. Moreover, downregulation of col5a1 attenuated cardiac fibrotic scar resolution in zebrafish. Interestingly, downregulation of COL5A1 or inhibition of miR-145-5p diminished the expression of integrin subunits ITGβ3 and ITGβ5. Furthermore, inhibition of miR-145-5p potentiated the suppression of TGF-β/SMAD signalling and the enhancement of fibroblast proliferation mediated by inhibiting integrin αvβ3 and αvβ5 with cilengitide. Collectively, miR-145-5p modulates collagen production and fibroblast behaviour partially via targeting COL5A1 and through integrin-mediated pathways.