Characterization of senescent mesenchymal stem/stromal cells derived from equine bone marrow and the effects of NANOG on the senescent phenotypes.

In equine regenerative medicine using bone marrow-derived mesenchymal stem/stromal cells (BM-MSC), the importance of the quality management of BM-MSC has been widely recognized. However, there is little information concerning the relationship between cellular senescence and the stemness in equine BM-MSC. In this study, we showed that stemness markers (NANOG, OCT4, SOX2 and telomerase reverse transcriptase) and colony forming unit-fibroblast apparently decreased accompanied with incidence of senescence-associated β-galactosidase-positive cells by repeated passage. Additionally, we suggested that down-regulation of cell proliferation in senescent BM-MSC was related to increased expression of cyclin-dependent kinase inhibitor 2B (CDKN2B). On the other hand, forced expression of NANOG into senescent BM-MSC brought upregulation of several stemness markers and downregulation of CKDN2B accompanied with restoration of proliferation potential and osteogenic ability. These results suggested that expression of NANOG was important for the maintenance of the stemness in equine BM-MSC.