P2RX7 and Osteopenia: In bone marrow mesenchymal stem cells (BMMSCs), TET1 plays a key role in maintaining BMMSC and bone homeostasis by controlling exosome and miRNA release through P2X purinoceptor 7 (P2RX7) demethylation, and could be a target for the development of new therapies for osteopenia [36].