Costal Chondrocyte–Derived Pellet-Type Autologous Chondrocyte Implantation for Treatment of Articular Cartilage Defect

Background: Because articular chondrocyte-based autologous chondrocyte implantations (ACIs) have restrictively restored articular cartilage defects, alternative cell sources as a new therapeutic option for cartilage repair have been introduced. Purpose: To assess whether implantation of a costal chondrocyte–derived pellet-type (CCP) ACI allows safe, functional, and structural restoration of full-thickness cartilage defects in the knee. Study Design: Case series; Level of evidence, 4. Methods: In this first-in-human study, 7 patients with symptomatic, full-thickness cartilage lesions were enrolled. The chondrocytes isolated from the patients’ costal cartilage were expanded, followed by 3-dimensional pellet culture to prepare the CCP-ACI. Implantation of the pellets was performed via minimal arthrotomy and secured with a fibrin sealant. Clinical scores, including the International Knee Documentation Committee (IKDC) subjective, Lysholm, and Tegner activity scores, were estimated preoperatively and at 1, 2, and 5 years postoperatively. High-resolution magnetic resonance imaging was also performed to evaluate cartilage repair as well as to calculate the MOCART (magnetic resonance observation of cartilage repair tissue) score. Results: The costal chondrocytes of all patients formed homogeneous-sized pellets, which showed the characteristics of the hyaline cartilaginous tissue with lacunae-occupied chondrocytes surrounded by glycosaminoglycan and type II collagen-rich extracellular matrix. There were no treatment-related serious adverse events during the 5-year follow-up period. Significant improvements were seen in all clinical scores from preoperative baseline to the 5-year follow-up (IKDC subjective score, 34.67 to 75.86; Lysholm score, 34.00 to 85.33; Tegner activity score, 1.17 to 4.67; and MOCART score, 28.33 to 83.33). Two patients had complete defect filling on magnetic resonance imaging evaluation at 1 year. Moreover, at 5 years postoperatively, complete defect filling was observed in 4 patients, and hypertrophy or incomplete defect filling (50%-100%) was observed in 2 patients. Conclusion: The overall results of this clinical study suggest that CCP-ACI can emerge as a promising therapeutic option for articular cartilage repair with good clinical outcomes and structural regeneration and with stable results at midterm follow-up. Registration: NCT03517046 (ClinicalTrials.gov identifier)