Citation

Caramés B, Taniguchi N, Seino D, Blanco FJ, D'Lima D, Lotz M. Arthritis Rheum. 2012; 64(4): 1182-1192.

Affiliation

Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, USA.

Copyright

(Copyright © 2012, John Wiley and Sons)

DOI

10.1002/art.33444

PMID

22034068

PMCID

PMC3288456

Abstract

OBJECTIVE.: Mechanical injury induces cell death in cartilage and triggers a remodeling process that ultimately can manifest as osteoarthritis (OA). Autophagy is a process for turnover of intracellular organelles and macromolecules that protects cells during stress responses. This study determined changes and functions of autophagy following mechanical injury to cartilage. METHODS.: Bovine and human cartilage explants were subjected to mechanical impact (40% strain, 500 ms). Cell viability, sulfated glycosaminoglyan (sGAG) release and changes in autophagy markers ULK1, Beclin1 and LC3 were evaluated. Cartilage explants were also treated with the mTORC1 inhibitor and autophagy inducer rapamycin and tested for protective effects against mechanical injury, the cell death inducers nitric oxide and TNFa+Actinomycin D and the proinflammatory cytokine IL-1a. RESULTS.: Mechanical injury induced cell death and loss of sGAG in a time-dependent manner. This was associated with significantly decreased ULK1, Beclin1 and LC3 expression in the cartilage superficial zone (P < 0.05) at 48 hours post-injury. The levels of LC3-II were increased at 24 hours post-injury but decreased at 48 and 96 hours. Rapamycin enhanced expression of autophagy regulators and prevented cell death and sGAG loss in mechanically injured explants. Rapamycin also protected against cell death induced by SNP, TNFa+Actinomycin D and prevented sGAG loss induced by IL-1a. CONCLUSION.: Mechanical injury leads to suppression of autophagy, predominantly in the superficial zone where most of the cell death occurs. Pharmacological inhibition of mTORC1, at least in part by enhancement of autophagy prevented cell and matrix damage suggesting a novel approach for chondroprotection.

Language: en