Tet1 and Tet2 Maintain Mesenchymal Stem Cell Homeostasis via demethylation of P2rX7 promoter

Ten-eleven translocation (Tet) family-mediated DNA oxidation represents a novel epigenetic modification capable of converting 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) to regulate various biological processes. However, it is unknown whether the Tet family affects mesenchymal stem cells (MSCs) or the skeletal system. Here we show that depletion of Tet1 and Tet2 resulted in impaired self-renewal and differentiation of bone marrow MSCs (BMMSCs) and a significant osteopenia phenotype. Mechanistically, Tet1 and Tet2 deficiency reduced demethylation of the P2rX7 promoter and thus downregulated exosome release, leading to intracellular accumulation of miR-297a-5p, miR-297b-5p, and miR-297c-5p. These miRNAs inhibited Runx2 signaling to impair BMMSC function. We show that overexpression of P2rX7 consistently rescued the impaired BMMSCs and osteoporotic phenotype in Tet1 and Tet2 double knockout mice. These results indicate that Tet1 and Tet2 play a critical role in maintaining BMMSC and bone homeostasis through epigenetic regulation of P2rX7 to control exosome and miRNA release. This newly identified Tet/P2rX7/Runx2 cascade may serve as a target for the development of novel therapies for osteopenia disorders.