Development of an Ex Vivo Osteochondral Biomimetic Platform for Mechanistic Investigation of Cartilage Regeneration

Articular cartilage possesses limited intrinsic healing capacity due to its avascular and aneural nature, posing a significant challenge for treating focal chondral defects. While regenerative strategies employing biomaterials and stem cells have progressed, their mechanistic evaluation is hindered by the lack of physiologically relevant in vitro models. This study aimed to establish and characterize a human ex vivo osteochondral explant model to assess cellular and extracellular matrix responses to cartilage repair strategies. Osteochondral explants (10 mm diameter, <i>n</i> = 61) were harvested from femoral condyles of patients undergoing knee arthroplasty. Standardized full-thickness chondral defects (4 mm) were created and assigned to six treatment groups: native control, untreated defect, fibrin glue, collagen type I hydrogel (ChondroFiller^®), fibrin glue + MSCs, and ChondroFiller^® + MSCs. Explants were cultured for 7, 14, or 21 days, followed by metabolic, biochemical, and histological assessments. Explants remained viable for 21 days. Notably, the ChondroFiller^® group showed a 2.4-fold increase in DNA content by day 14, while MSC-treated groups enhanced collagen deposition and GAG production. Significant correlations between DNA and collagen levels were observed in scaffold-based treatments. This ex vivo model offers a reproducible and translational platform to investigate cartilage regeneration with temporal resolution, supporting preclinical testing of emerging therapeutic approaches.