Genetic Ablation of p16 Mitigates Premature Osteoporosis Induced by PTHrP Nuclear Localization Sequence and C-terminal Deletion through Inhibition of Cellular Senescence

Premature osteoporosis due to parathyroid hormone-related peptide (PTHrP) dysfunction presents significant bone health challenges. This study explores the role of p16-mediated cellular senescence in this condition using a Pthrp knock-in (KI) mouse model lacking the nuclear localization sequence and C-terminus of PTHrP. We generated p16⁻⁄⁻KI mice and compared them with wild-type, p16⁻⁄⁻, and KI mice. The genetic ablation of p16 in KI mice extended their lifespan, increased body size, and weight. Micro-CT analysis revealed a significant increase in bone volume, while histological and immunohistochemical studies revealed enhanced chondrocyte proliferation and osteoblast function in p16⁻⁄⁻KI mice. In vitro experiments showed enhanced differentiation capacity and reduced senescence of bone marrow mesenchymal stem cells (BM-MSCs) from p16⁻⁄⁻KI mice. Molecular analyses indicated that p16 knockout partially reversed oxidative stress, DNA damage, and cellular senescence observed in KI mice, as evidenced by upregulated antioxidant enzymes, reduced DNA damage markers, and decreased senescence markers. These findings highlight the critical role of p16-mediated cellular senescence in the premature osteoporosis phenotype of KI mice, suggesting that targeting cellular senescence pathways could offer a promising therapeutic strategy for premature osteoporosis and age-related bone loss. This research provides new insights into the interplay between genetic factors, cellular senescence, and bone metabolism in the context of aging and osteoporosis.