Strain Rate during Mechanical Injury of Articular Cartilage Explants Affects the Subsequent Evolution of Cell and Matrix Damage

Introduction: Nonphysiological mechanical loading may be a contributing factor to the initiation and progression of degenerative diseases of articular cartilage such as osteoarthritis. Previous studies have shown that impact loading can give rise to the "propagation" of cell death from impacted to nonimpacted tissue regions [1], perhaps related to the release of toxic oxygen species and induced apoptosis [2]. It has also been shown that acute effects of injurious mechanical loading on cartilage explants can depend upon the rate at which compression is applied [3], with the "gel diffusion" rate [4] representing an apparent "watershed" dividing different biomechanical regimes of matrix injury and cell death. In order to better understand the relationships between cartilage mechanics and the cell response to mechanical injury, the aim of this study was to investigate the effects of compression strain rate on the temporal evolution of spatial patterns of cell and matrix injury between 1 hour and 11 days following mechanical injury of cartilage explants.