Regulation of differentiation potential of human mesenchymal stem cells by intracytoplasmic delivery of coactivator-associated arginine methyltransferase 1 protein using cell-penetrating peptide.

Recent studies suggest that epigenetic modifications, such as DNA methylation and histone modification, can alter the differentiation potential of stem cells or progenitor cells. Specifically, coactivator-associated arginine methyltransferase 1 (CARM1) is known to act as a coactivator for various transcription factors and to regulate gene expression by chromatin remodeling through histone methylation. Here, for the first time, we have used direct protein delivery of CARM1 using cell-penetrating peptide (CPP) to regulate the differentiation potential of human mesenchymal stem cells (hMSCs). Immunofluorescence showed that the CPP-CARM1 protein is successfully delivered into the nuclei of hMSCs. Further experiments using immunofluorescence and Western blotting showed that the delivered CARM1 protein can effectively methylate the arginine 17 residue of histone H3 in both bone marrow (BM)- and adipose-derived (AD)-hMSCs, thus suggesting that the CARM1 protein delivered by the CPP system is biologically active in hMSCs. Chromatin immunoprecipitation (ChIP) assay and genome-wide gene expression profiling supported the result that delivered CARM1 protein can cause chromatin remodeling through histone methylation. Finally, the CPP-CARM1 protein efficiently elevated the differentiation efficiency of BM-hMSCs and AD-hMSCs into adipogenic, osteogenic, and myogenic cell lineages in vitro. Altered expression of critical genes after hMSC differentiation was reconfirmed by real-time reverse transcription polymerase chain reaction (qRT-PCR). Collectively, our results suggest that CPP-CARM1 can elevate the differentiation potential of hMSCs into various cell types, and that this system using CPP is a useful tool for exogenous protein delivery in clinical applications of cell-based therapy.