Senescent cells (SnCs) accumulate in many vertebrate tissues with age and contribute to age-related pathologies1,2,3, presumably through their secretion of factors contributing to the senescence-associated secretory phenotype (SASP)4,5,6. Removal of SnCs delays several pathologies7,8,9 and increases healthy lifespan8. Aging and trauma are risk factors for the development of osteoarthritis (OA)10, a chronic disease characterized by degeneration of articular cartilage leading to pain and physical disability. Senescent chondrocytes are found in cartilage tissue isolated from patients undergoing joint replacement surgery11,12,13,14, yet their role in disease pathogenesis is unknown. To test the idea that SnCs might play a causative role in OA, we used the p16-3MR transgenic mouse, which harbors a p16INK4a (Cdkn2a) promoter driving the expression of a fusion protein containing synthetic Renilla luciferase and monomeric red fluorescent protein domains, as well as a truncated form of herpes simplex virus 1 thymidine kinase (HSV-TK)15,16. This mouse strain allowed us to selectively follow and remove SnCs after anterior cruciate ligament transection (ACLT). We found that SnCs accumulated in the articular cartilage and synovium after ACLT, and selective elimination of these cells attenuated the development of post-traumatic OA, reduced pain and increased cartilage development. Intra-articular injection of a senolytic molecule that selectively killed SnCs validated these results in transgenic, non-transgenic and aged mice. Selective removal of the SnCs from in vitro cultures of chondrocytes isolated from patients with OA undergoing total knee replacement decreased expression of senescent and inflammatory markers while also increasing expression of cartilage tissue extracellular matrix proteins. Collectively, these findings support the use of SnCs as a therapeutic target for treating degenerative joint disease.
We thank J. Xu (F.M. Kirby Research Center at Johns Hopkins University) for in vivo luminescence imaging, A. Bendele (Bolder Biopath, Inc.) for the subchondral bone damage analysis and Y. Oh (Johns Hopkins University) for immunoblotting. This work was supported by Unity Biotechnology, Inc. (J.H.E., A.P.V., Y.P., N.D.), the Bloomberg-Kimmel Institute for Cancer Immunotherapy (J.H.E.), the Morton Goldberg Professorship (J.H.E.), National Institute on Aging (NIA) grant AG017242 (J.C.), AG009909 (M.D.), National Cancer Institute (NCI) grant R01CA96985 (J.M.v.D.), a grant from the Paul F. Glenn Foundation (J.M.v.D. and D.J.B.) and a Fulbright scholarship from the Institute of International Education (O.H.J.).
Supplementary Figures 1–13 and Supplementary Table 1.