[Study on the effect of superficial layer damage on cartilage retention performance]

The superficial layer of articular cartilage acts as a critical physical barrier for joint homeostasis, and its damage is a hallmark of early osteoarthritis. To investigate the effect of superficial layer injury on solute permeation and retention in cartilage, two injury models were established using isolated porcine cartilage: chymotrypsin digestion (mucus layer injury) and physical abrasion (10% removal of the superficial layer). Rhodamine B (479 Da) and rhodamine-labeled dextrans (40 kDa, 150 kDa) were used as tracers. Combined with a custom-built permeation device and laser scanning confocal microscopy, solute transport behaviors under different injury degrees were analyzed. The results showed that superficial layer injury significantly impaired the barrier function, with retention concentrations increasing as injury severity rose. Solutes with lower molecular weights migrated more rapidly and exhibited higher retention levels. The peak solute concentration was localized in the superficial layer of normal cartilage but shifted toward the middle layer after injury. This study demonstrates that superficial layer integrity is essential for regulating cartilage solute transport, providing experimental evidence for understanding substance transport disorders in early cartilage degeneration of osteoarthritis.