Influence of Cell Differentiation and IL-1β Expression on Clinical Outcomes After Matrix-Associated Chondrocyte Transplantation

Background: Several patient- and defect-specific factors influencing clinical outcomes after matrix-associated chondrocyte transplantation (MACT) have been identified, including the patient's age, location of the defect, or duration of symptoms before surgery. Little is known, however, about the influence of cell-specific characteristics on clinical results after transplantation. Purpose: The aim of the present study was to investigate the influence of cell differentiation and interleukin-1 (IL-1) expression on clinical outcomes up to 5 years after MACT. Study Design: Case series; Level of evidence, 4. Methods: Twenty-seven patients who underwent MACT of the tibiofemoral joint area of the knee were included in this study. Clinical assessments were performed preoperatively as well as 6, 12, 24, and 60 months after transplantation by using the following scores: the Knee injury and Osteoarthritis Outcome Score (KOOS), the International Knee Documentation Committee (IKDC) Subjective Knee Form, the Noyes sports activity rating scale, the Brittberg clinical score, and a visual analog scale (VAS) for pain. The quality of repair tissue was assessed by magnetic resonance imaging using the magnetic resonance observation of cartilage repair tissue (MOCART) score at 1 and 5 years. Cell differentiation (defined as collagen type II:type I expression ratio), aggrecan, and IL-1 expression were determined by real-time polymerase chain reaction in transplant residuals and were correlated with clinical outcomes. Results: The largest improvements in clinical scores were found during the first year. Two years postoperatively, a stable improvement was reached until 5 years after transplantation, with a mean IKDC score of 34.4 8.6 preoperatively to 77.9 +/- 16 after 24 months (P < .001). Cell differentiation showed a significant positive correlation with nearly all clinical scores at different time points, especially after 12 months (P < .05). IL-1 expression negatively influenced clinical outcomes at 24 months (Brittberg score) and 60 months (Brittberg and VAS scores) after surgery (P < .05). No correlation was found between the MOCART score and clinical outcomes or gene expression. Conclusion: Our data demonstrate that cell differentiation and IL-1 expression influence clinical outcomes up to 5 years after MACT.