Recombinant human SGK3 protein hydrogel: a novel therapeutic strategy for myocardial repair in ischemia/reperfusion injury.

Myocardial infarction (MI) leads to substantial cardiomyocyte loss and heart failure, whereas current therapies fail to promote cardiac regeneration. Our prior work demonstrated that serum and glucocorticoid-regulated kinase 3 (SGK3) promote cardiac repair. To overcome the limitations of viral gene therapy, we develop a recombinant human SGK3 (rhSGK3) protein fused with a cell-penetrating peptide and encapsulate it in a thermosensitive PLGAPEG-PLGA hydrogel for sustained local delivery. In vitro, rhSGK3 efficiently enters neonatal mouse cardiomyocytes and significantly promotes proliferation, reduces OGD/R-induced apoptosis, stabilizes OGD/R-induced mitochondrial membrane potential, and upregulates the expressions of glycolytic enzymes including PKM2, LDHA, PFKP, and HK2, while shifting energy metabolism from oxidative phosphorylation toward glycolysis. These effects are reversed by the glycolysis inhibitor 2-DG. Mechanistically, rhSGK3 activates the HIF-1α/HK2 signaling axis, and HIF-1αknockdown abolishes its pro-proliferative and anti-apoptotic effects. In an in vivo myocardial ischemia/reperfusion (I/R) mouse model, intramyocardial injection of rhSGK3-hydrogel preserves mitochondrial ultrastructure, enhances cardiomyocyte proliferation, reduces apoptosis, attenuates fibrotic scar formation, and significantly improves cardiac function at 28 days post-I/R. Importantly, HIF-1α knockdown in vivo reverses these protective effects. Together, these findings suggest that local delivery of rhSGK3 via a thermosensitive hydrogel promotes cardiac repair after I/R injury through HIF-1α/HK2-mediated glycolytic reprogramming and mitochondrial protection. This study presents a promising protein-based, gene-integration-free therapeutic strategy for myocardial repair.