miR‐125b Is an Adhesion‐Regulated microRNA that Protects Mesenchymal Stem Cells from Anoikis

Abstract

Mesenchymal stem cells (MSCs) have the capacity for multilineage differentiation and are being explored as a source for stem cell-based therapies. Previous studies have shown that adhesion to extracellular matrix plays a critical role in guiding MSC differentiation to distinct lineages. Here we conducted a focused screen of microRNAs to reveal one microRNA, miR-125b, whose expression changes as a function of cell adhesion. miR-125b expression was upregulated by limiting cell-matrix adhesion using micropatterned substrates, knocking down beta5 integrin, or placing cells in suspension culture. Interestingly, we noted that suspending hMSCs did not induce substantial apoptosis (anoikis) as is typically observed in adherent cells. Although miR-125b appeared to have some effects of on hMSC differentiation, we demonstrated a striking role for miR-125b in protecting hMSCs from anoikis. Knockdown of miR-125b increased anoikis while expressing a mimic protected cells. Mechanistic studies demonstrated that miR-125b protected against anoikis by increasing ERK phosphorylation and by suppressing p53. Lastly, we found that miR-125b expression is quite limited in endothelial cells and MEFs; the rapid anoikis normally observed in these cells is antagonized by expressing a miR-125b mimic; and induced pluripotent stem (iPS) cells generated from the MEFs led to upregulated miR-125b expression. Together, these observations demonstrate a novel link between cell-matrix adhesion, miR-125b expression, and a stem-cell specific survival program triggered in adhesion-limited contexts such as might occur in early development and wound healing.

miR-125b can enhance skin tumor initiation and promote malignant progression by repressing differentiation and prolonging cell survival

“…S2E,F). These results were noteworthy in light of a recent report that miR-125b protects mesenchymal stem cells from anoikis (Yu et al 2012), suggesting that the role of miR-125b in anchorageindependent survival may extend to multiple cell types.…”

Concise Review: MicroRNA Function in Multipotent Mesenchymal Stromal Cells

“…Remarkably, transgenic mice that ectopically express miR‐206 in osteoblasts show lower bone density and decreased bone formation rate . Silencing endogenous levels of miR‐125b was found to inhibit osteogenesis in a MSC cell line , but not in primary culture of MSCs , stressing the difference of cell lines to primary cultures of MSCs. Also miR‐489 and miR‐541 inhibit osteogenesis , but their targets in this context are not known.…”

“…Also miR‐107, which targets the 3′UTR of programmed cell death‐10, is upregulated during anoxia, while loss of function of miR‐107 results in increased apoptosis . Maintenance of MSCs in suspension leads to upregulation of miR‐125b, which in turn represses p53, protecting cells against anoikis (death by detachment) .…”

microRNA Regulation of Skeletal Development

“…miR-125b, a miRNA identified in MSCs throughout many genetic screens [98,81], is predicted to target Osx. However, a relationship has not been confirmed beyond the finding of reduced Osx mRNA [99].…”