gms | German Medical Science

Objectives: Arthroscopic minced cartilage (MC) procedures (AMC) have gained popularity for the single-stage treatment of focal cartilage defects in the knee. However, in contrast to conventional MC (CMC) there is scarce evidence regarding the chondrogenic potential of regenerative cartilage tissue (RCT) following AMC. The aim of this study was therefore to characterize and compare the RCT following CMC and AMC, in terms of cell viability, gene expression and matrix synthesis.

Methods: A two-arm study was conducted to evaluate the results of human and porcine samples. Chondral tissue was harvested from the knees of 9 human and 8 porcine donors. Human specimens were <40 years old with intact, native cartilage surfaces and deceased <48 hours prior to harvest. Porcine specimens were euthanized one day before harvest. Arthroscopic harvest was performed with two shaver blades (groups 1 and 2) in 2 operating modes (oscillating vs. forward) and compared to a scalpel-fragmented control. Samples were digested (Collagenase II) to optimize cell differentiation, compared to native tissue samples and analyzed histologically (Trypan blue staining). A subset of porcine samples was analyzed for cell viability, gene expression of cartilage-specific markers (Aggrecan (ACAN), collagen-II, alpha1 (COL2A1), collagen-I, alpha1 (COL1A1), fibronectin 1 (FN)), and cartilage matrix synthesis (Alcian blue staining) after 21 days of 2D culture.

Results and conclusion: In both human and porcine specimens, AMC tissue contained significantly fewer vital chondrocytes (465–773/g³ vs. 2,271–2,564/g³, p=0.02) and significantly lower ratios of vital per total chondrocytes (41–54% vs. 90–91%, p<0.01) compared to the controls, regardless of shaver blade or operating mode. After 21 days, the digested controls showed high expressions of ACAN (29 virtual copy numbers (VCN)/GAPDH) and COL2A1 (30 VCN/GAPDH), which were significantly lower in the digested groups 1 and 2 (ACAN 2–9 VCN/GAPDH, COL2A1 2–7 VCN/GAPDH, p=0.001), regardless of shaver blade or operating mode. The COL1A1 (9–20 VCN/GAPDH) and FN (12–19 VCN/GAPDH) expressions were significantly higher in the digested groups 1 and 2 compared to the digested controls (1 and 5 VCN/GAPDH, p=0.001). Similar observations were made for the native samples, showing an overall decrease in ACAN and COL2A1, but an increase in COL1A1 and FN. The cartilage matrix formed in the digested control showed a strong signal intensity (85/mm²) but was significantly less intense in groups 1 and 2 (7–11 mm², p<0.01).

In conclusion, arthroscopic harvesting of healthy cartilage tissue significantly impaired chondrocyte quantity and viability compared to conventional fragmentation. Furthermore, the high chondrogenic potential of MC to form hyaline-like repair tissue could not be confirmed for arthroscopic techniques, which showed a high expression of fibroblast markers.