(116bb) Modulation of Lubricin Gene Expression Following Cartilage Mechanical Injury

Osteoarthritis (OA) is a prevalent joint disease among the elderly population. Traumatic injury to the cartilage at an early age is a major factor that leads to OA development later in life. The objectives of the study are to evaluate how injurious compression affects the lubricin gene expression in cartilage at different time points after injury, and to quantify the peak stresses in the cartilage produced by graded levels of compressive strain rates. Traumatic injury is simulated in vitro by applying a 50% compressive strain to bovine cartilage explants at 100%/s strain rate. Lubricin gene expression was sequentially analyzed by RNA extraction, reverse transcription into cDNA, and real-time PCR. At cartilage surface layer, injury increased lubricin expression after two days of culture but the underlying layer instead contained very low lubricin expression levels. Compared to 100%/s, a 1mm/s strain rate produced very different peak stresses but similar lubricin expression at two days after injury. The lubricin expression response to different strain rates may be elucidated by looking at larger ranges of graded strain rates. Further, looking at earlier time points within the first 24 hours after injury will provide more clues to the transient effect of injury on cartilage.