Chondrogenic potential of articular chondrocytes depends on their original location

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

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

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 normalized per DNA compared to those from grade IV and NWB 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 NWB cartilage compared to grade III and weight-bearing regions.

Chondrocytes derived from debrided cartilage perform better than cells from the NWB 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.