Chondrogenic potential of articular chondrocytes depends on their original location in the knee

Objective: This study aimed to investigate the regenerative capacity of chondrocytes derived from debrided defect cartilage and healthy cartilage from different regions in the joint in order to determine the best cell source for regenerative cartilage therapies.

Methods: Articular cartilage was obtained form Outerbridge grade III and IV cartilage lesions and from macroscopically healthy weight-bearing and non-weight bearing locations in the knee. Chondrocytes isolated from all locations were either pelleted directly (P0 pellets) or after expansion (P2 pellets) and analyzed for GAG, DNA and cartilage-specific gene expression. Harvested cartilage samples and cultured pellets were also analysed by Safranin-O histology and immunohistochemistry for collagen I, II and X. Immunohistochemical stainings were quantified using a computerized pixel-intensity staining segmentation method.

Results: After 4 weeks of culture the P0 pellets derived from grade III or healthy weight bearing chondrocytes contained more (p<0.015) GAG and GAG normalised per DNA compared to those from grade IV and non-weight bearing locations. After expansion, these differences were lost. Cartilage-specific gene expression was higher (p<0.04) in P0 pellets from grade III chondrocytes compared to grade IV chondrocytes. Semiquantitative immunohistochemistry showed a more intense (p<0.033) collagen I and X staining for grade IV debrided cartilage compared to grade III and weight bearing cartilage. Also collagen type X staining intensity was higher (p<0.033) in non-weight bearing cartilage compared to grade III and weight bearing regions.

Conclusion: Chondrocytes derived from debrided cartilage perform better than cells from the non-weight bearing biopsy site, however this difference is lost upon expansion. Based thereon the debrided defect cartilage could be a viable donor site for regenerative cartilage surgery.