Background: Stem cell transplantation has emerged as a widely recognized therapeutic approach for myocardial infarction (MI). The primary objective of this study was to investigate the specific role of suppressor of cytokine signaling 3 (SOCS3) in regulating the differentiation potential of mesenchymal stem cells (MSCs) into functional cardiomyocytes. This research lays important groundwork for the development of novel therapeutic strategies aimed at post-injury cardiac regeneration.

Methods: Isolated from human umbilical cord tissue, MSCs were characterized through confirmation of positive expression of surface markers (CD90, CD73, CD44) in flow cytometry. Their multipotency was verified by demonstrating osteogenic and adipogenic differentiation potential, which was confirmed using Alizarin red and oil red O staining approaches, respectively. To elucidate the role of SOCS3, its expression was knocked down using shRNA (shSOCS3). Subsequently, cell morphological changes and expression of key cardiomyocyte-specific genes and proteins were analyzed. Furthermore, STAT3 knockdown (siSTAT3) and GATA binding protein 4 (GATA4) overexpression plasmids were constructed and employed in vitro to explore the underlying mechanism. Putative binding interaction between the transcription factor STAT3 and the promoter of GATA4 was predicted via the JASPAR database and subsequently validated experimentally by means of chromatin immunoprecipitation (ChIP).

Results: ShSOCS3 promoted cardiomyocyte-like morphological alterations in MSCs. Upregulation in the expression of connexin-43, myosin heavy chain (MHC), cardiac troponin T, NK2 homeobox 5 (NKX-2.5), and GATA4 was also detected following the transfection of shSOCS3. These effects attributable to shSOCS3 were partially reversed by siSTAT3. GATA4, which was bound to STAT3, partially counteracted the effect of siSTAT3.

Conclusion: SOCS3 plays an inhibitory role in the cardiomyogenic differentiation of MSCs, which is mechanistically mediated by the STAT3/GATA4 signaling axis, wherein SOCS3 modulates STAT3 activity, which in turn directly influences the expression of the critical cardiac transcription factor GATA4.