Identification of a CTRP9 Fragment Capable of Enhancing Bone Marrow Mesenchymal Stem Cell Cardioprotection via Cardioreparative Exosome Production Promotion

Abstract

BackgroundThe safety of bone marrow mesenchymal stem cell (BMSC) therapy in ischemic heart injury has been clinically established. However, the poor survival of engrafted stem cells in the ischemic environment limits their therapeutic efficacy for post‐infarction cardiac repair. CTRP9 is a protective cardiokine capable of improving the local microenvironment. The current study attempted to 1) identify a small biologically active CTRP9 fragment with lower immunogenicity, and 2) test a hypothesis that said CTRP9 fragment may promote a healthy microenvironment, and improve implanted stem cell survival and resultant cardioprotection.Methods and ResultsGlobular CTRP9 (gCTRP9, the most biologically active form of CTRP9) and 2 fragments of gCTRP9 (computationally predicted) were cloned and purified. In vitro experiments demonstrated that CTRP9‐F2 possesses biological activity equal to or exceeding gCTRP9. Wild‐type C57BL/6 mice were subjected to myocardial infarction and treated with BMSCs, CTRP9‐F2, or their combination. Administration of CTRP9‐F2, but not BMSCs alone, attenuated MI/R injury. Administration of CTRP9‐F2 plus BMSCs further enhanced the cardioprotective effect of CTRP9‐F2, suggesting a synergistic effect. BMSCs retention/survival in the ischemic region was significantly improved in the CTRP9‐F2 treated group. Conversely, the engrafted BMSC population was significantly reduced in the CTRP9 knockout heart. Mechanistically, CTRP9‐F2 promoted BMSC proliferation and migration, and protected BMSCs against H2O2‐induced cellular death. Interestingly, CTRP9‐F2 significantly enhanced BMSC exosome production, upregulated the exosomal cytoprotective molecule contents, and facilitated cardiomyocyte uptake of BMSC‐derived exosomes. Blockade of ERK1/2 completely abolished the effects of CTRP9‐F2 upon BMSC biology.ConclusionWe identify, for the first time, a small CTRP9 fragment capable of promoting BMSC cardioprotection via augmented exosome‐mediated BMSC‐cardiomyocyte communication.Support or Funding InformationW.W. Smith Foundation (to YJW)