The purinergic receptor P2rx7 mediated ATP sensing is required to prevent bone aging by directing mitochondrial fitness of MSCs.

Background: Bone aging, displays osteoporosis and impaired bone formation, intricately linked to the metabolic alteration of mesenchymal stem cells (MSCs). However, the precise mechanisms underlying this relationship remain unclear.

Objectives: To determine how P2rx7 modulates mitochondrial dynamics during bone aging and osteogenic differentiation of MSCs.

Methods: We established P2rx7 mice, to verify the role of P2rx7 in bone metabolism and aging. The bone phenotype was evaluated by micro-CT and histological analyses. The differentiations of MSCs were analyzed by Alizarin red staining and alkaline phosphatase staining. Mitochondrial function was assessed by Seahorse assay, ATP content and membrane potential. Mitochondrial morphology was analyzed by transmission electron microscopy and confocal microscopy.

Results: A decreased expression of P2rx7 concurrent with abnormal mitochondrial dynamics was observed in aged bone tissue. To confirm the role of P2rx7 in bone metabolism and aging, we deleted P2rx7 by using P2rx7 mice and the mice demonstrated premature and exacerbated bone aging. Mechanically, deletion of P2rx7 attenuated the sensitivity of ERK pathway to stimulus, which in turn weakened mitochondrial fusion and resulted in a sparsely connected mitochondrial network via Mitofusion 1. Consistently, P2rx7 deficiency impaired the mitochondrial fitness and bone formation of MSCs. The activation of P2rx7 in MSCs by Benzoylbenzoyl-ATP enhanced the sensitivity of ERK signaling, thereby enhancing mitochondrial fusion and promoting the osteogenic differentiation of MSCs and bone regeneration. Furthermore, restoring mitochondrial fitness in MSCs by Dichloroacetate could rescue the impaired bone regeneration and bone aging observed in P2rx7 mice.

Conclusion: Taken together, our results highlight a role for P2rx7 in regulating mitochondrial dynamics coordinates with ERK pathway, thereby highlighting P2rx7 as a promising target to rejuvenate the tissue aging.