Genetic ablation of p16 mitigates premature osteoporosis induced by PTHrP nuclear localization sequence and C-terminal deletion through inhibition of cellular senescence.

Abstract

Background: Premature osteoporosis caused by parathyroid hormone-related peptide (PTHrP) dysfunction presents significant bone health challenges. The role of p16-mediated cellular senescence in this condition remains unclear.

Methods: 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. We analyzed survival, skeletal phenotypes, bone marrow mesenchymal stem cell (BM-MSC) function, and molecular markers of senescence.

Results: Genetic ablation of p16 in KI mice extended their lifespan, increased body size and weight, and improved skeletal growth. Micro-CT analysis revealed significantly increased bone volume, while histological studies showed enhanced chondrocyte proliferation and osteoblast function in p16⁻⁄⁻KI mice compared to KI mice. In vitro experiments demonstrated enhanced differentiation capacity and reduced senescence of BM-MSCs from p16⁻⁄⁻KI mice, as evidenced by increased colony formation and osteogenic marker expression. Molecular analyses indicated that p16 knockout partially reversed oxidative stress, DNA damage, and cellular senescence observed in KI mice, shown by upregulated antioxidant enzymes, reduced DNA damage markers, and decreased senescence markers.

Conclusions: p16-mediated cellular senescence plays a crucial role in premature osteoporosis caused by PTHrP dysfunction. Targeting cellular senescence pathways may offer a promising therapeutic strategy for treating premature osteoporosis and age-related bone loss.