Abstract
Administration of mesenchymal stem cells (MSCs) has the potential to ameliorate degenerative disorders and to repair damaged tissues. The homing of transplanted MSCs to injured sites is a critical property of engraftment. Our aim was to identify microRNAs involved in controlling MSC proliferation and migration. MSCs can be isolated from bone marrow and umbilical cord Wharton's jelly (BM-MSCs and WJ-MSCs, respectively), and WJ-MSCs show poorer motility yet have a better amplification rate compared with BM-MSCs. Small RNA sequencing revealed that miR-146a-5p is significantly overexpressed and has high abundance in WJ-MSCs. Knockdown of miR-146a-5p in WJ-MSCs inhibited their proliferation yet enhanced their migration, whereas overexpression of miR-146a-5p in BM-MSCs did not influence their osteogenic and adipogenic potentials. Chemokine (C-X-C motif) ligand 12 (CXCL12), together with SIKE1, which is an I-kappa-B kinase epsilon (IKKε) suppressor, is a direct target of miR-146a-5p in MSCs. Knockdown of miR-146a-5p resulted in the down-regulation of nuclear factor kappa-B (NF-κB) activity, which is highly activated in WJ-MSCs and is known to activate miR-146a-5p promoter. miR-146a-5p is also downstream of CXCL12, and a negative feedback loop is therefore formed in MSCs. These findings suggest that miR-146a-5p is critical to the uncoupling of motility and proliferation of MSCs. Our miRNome data also provide a roadmap for further understanding MSC biology.