Research Of Partial-thickness Articular Cartilage Defects In A Rat Model And Related Cytological Changes

Objective To establish partial-thickness articular cartilage defects model in adult rats and investigate the change of tissue and cartilage cells.Methods Forty-five male Sprague Dawley rats(aged 10 weeks and weighing 300-400 g)were randomly divided into operated group(n=15),sham-operated group(n=15)and control group(n=15).Partial-thickness articular cartilage defects model was made by scarification with a converted ophthalmic knife in the sagittal direction on the weight-bearing region of femoral condyles in operated group.Direct suture after opening of the knee joint was performed in sham-operated group,and no operation was done in control group.Postoperatively rats were exposed to BrdU(lml/day)for consecutive 3 days.Five rats were sacrificed at 1,7,and 14 days after operation respectively for macroscopic evaluation,HE staining,Safranin O staining,TUNEL immunohistochemical staining,CD 105,BrdU,CD 105/integrin ?1 immunofluorescence and double labeling staining.The histological score of HE staining,gray value of Safranin O staining and CD 105-positive cells count were compared among groups at each time point.Results All rats were alive after operation.Macroscopic evaluation showed chondromalacia cartilage fibrosis around the cartilage defects with aggravating tendency with time in operated group,but no chondromalacia and cartilage fibrosis in sham-operated and control groups.HE staining demonstrated a number of activated cells accumulating around the linear injury with nonuniform distribution in operated group,and uniform size and distribution in sham-operated and control groups.The histological scores at each time point in operated group were significantly higher than those in sham-operated group and control group(P<0.05),but no significant intragroup difference was found in all three groups(P>0.05).Safranin O staining was nonuniform with hypochromasia around cartilage defects in operated group,but the staining was uniform in sham-operated group and control group.In terms of gray value of Safranin O staining,no intragroup and intergroup difference was found(P>0.05).Results of TUNEL histochemistry showed chondrocyte apoptosis at the bottom of cartilage defects.CD 105 immunofluorescence staining demonstrated that CD 105-positive cells distributed unevenly around the linear injury in operated group.CD 105-positive cells count in operated group was significantly higher than those in sham-operated group and control group at each time point(P<0.05);CD 105-positive cells increased significantly with time in operated group(14d compared with 7d,7d compared with 1d,both P<0.05).BrdU-label-retaining cells and CD105/integrin ?1-positive cells were observed around the cartilage defects in operated group,but was not observed in sham-operated group and control groupConclusion The partial-thickness articular cartilage defects model is successfully established by scarification with a converted ophthalmic knife in rats.The characteristic of damaged articular cartilage corresponded to early osteoarthritis and the cartilage defects could not repaired spontaneously completely in the model.There were BrdU-label-retaining cells accumulating around the cartilage defects,which could express the stem cell marker CD 105 and integrin ?1 that play a role in cell migration and adhesion.These activated cells were possibly chondrogenic progenitor cells.