MicroRNA-mediated direct cardiac reprogramming is an emerging strategy to regenerate damaged heart tissue, after myocardial infarction (MI), by directly converting endogenous cardiac fibroblasts into induced cardiomyocyte (iCM)-like cells. Since it has been observed that reprogramming was more efficient in vivo than in vitro, a strong focus has been placed on investigating the endogenous environment of the heart. This thesis project was carry out as part of BIORECAR project, and aimed to investigate how cardiac ECM proteins can affect cell reprogramming efficiency and which biological processes they induce, by exploiting different culture substrates for miRNA transfected cells. The main objective of the study was to identify which ECM proteins has the potential to boost or hinder the direct cardiac reprogramming, while investigating the molecular mechanisms that come into play.