Hepatocyte Growth Factor makes Human Mesenchymal Stem cells be rejuvenated by RAD51 pathway

Abstract

Human embryonic stem cell?derived mesenchymal stem cells (hE-MSCs) represent a better choice than adult stem cells (SCs) for cell-based therapy owing to their limitless capacity for self-renewal. We screened hE-MSCs and human bone marrow (hBM)?derived mesenchymal stem cells (MSCs) to identify secretory cytokines that were more strongly expressed in hE-MSCs and could be used as additives to rejuvenate hMSCs in culture. We identified hepatocyte growth factor (HGF) as a candidate molecule through loss- and gain-of-function experiments in hE-MSCs and hBM-MSCs, respectively. Adding HGF to hBM-MSCs increased telomere length and induced OCT4 and Nanog expression. RAD51 was identified as a factor acting downstream of HGF to promote telomere elongation. OCT4 and Nanog were also upregulated by RAD51 overexpression and downregulated by RAD51 RNA interference. To elucidate the mechanism underlying HGF-RAD51 signaling, we screened the putative RAD51 promoter and identified transcription factor?binding sites for IKAROS family zinc finger (IKZF) and Runt-related transcription factor (RUNX)1. Knockdown of these two factors in hBM-MSCs in the presence of recombinant human HGF reduced telomere length as well as OCT4, Nanog, and RAD51 expression. Treatment of hMSCs with rhHGF had no adverse effects on cell viability, and chromosomal configuration was normal, as determined by G-band analysis and telomere fluorescence in situ hybridization. These results suggest that HGF treatment is a safe and effective means of increasing the self-renewal capacity of hMSCs in cell-based therapies.