This study shows that a calibrated slight or moderate exercise exerts a beneficial influence on the severity of chondral lesions in ACLT rats. Conversely, a strong effort abolishes this chondroprotective effect. This effect could be related to a reduced level of chondrocyte apoptosis through anti-apoptotic capacities of stress-induced Hsp70 overexpression.

Osteoarthritis is characterized by a gradual degradation of extracellular matrix, resulting from an excess of chondrocyte cell death, mainly due to an increase in apoptotis. Recent studies have revealed the essential role of HSP70 in protecting cells from stressful stimuli. Therefore, overexpressing HSP70 in chondrocytes could represent a good strategy to prevent extracellular matrix destruction. To this end, we have developed a vector carrying HSP70/GFP, and transduced chondrocytes were thus more resistant to cell death induced by mono-iodoacetate (MIA). To overcome the barrier-effect of matrix, we investigated the efficacy of plasmid delivery by electroporation (EP) in rat patellar cartilage. Two days after EP, 50% of patellar chondrocytes were HSP/GFP+. After 3 months, long-term expression of transgene was only depicted in the deep layer (20-30% positive cells). HSP70 overexpression inhibited the natural endochondral ossification in the deep layer, thus leading to a lesser decrease in chondrocyte distribution. Moreover, overexpression of HSP70, after a preventive EP transfer in rat patella, was sufficient to decrease the severity of osteoarthritis-induced lesions, as demonstrated histologically and biochemically. In conclusion, intracellular overexpression of HSP70, through EP delivery, could protect chondrocytes from cellular injuries and thus might be a novel chondroprotective modality in rat OA.

No abstract

To establish a system for efficient direct in vivo gene targeting into rat joint, we have evaluated a strategy of gene transfer by means of the delivery of external electric pulses (EP) to the knee after intra-articular injection of a reporter gene (GFP). Rats were killed at various times after the electro gene-therapy to analyze GFP gene expression by immunohistochemistry. GFP staining was detected in the superficial, middle, and deep zones of the patellar cartilage at days 2 and 9, and thereafter only in the deep zone (months 1 and 2). The average percentage of GFP-positive cells was estimated at 30% both one and 2 months after the gene transfer. Moreover, no pathologic change caused by the EP was detected in the cartilage. The level and stability of the long-term GFP expression found in this study demonstrate the feasibility of a treatment of joint disorders (inflammatory or degenerative, focal or diffuse) using electric gene transfer.