Tissue-engineered implants are commonly applied for the treatment of localized cartilage lesions. The goal of this project is to determine and establish biomolecular parameters accounting for the quality of collagen I-matrices seeded with autologous chondrocytes (~transplants). A special focus is laid on cartilage-constituting, matrix-degrading, and cell surface proteins since they might influence the clinical outcome after implantation. Two identical transplants, from a local biotech company, are routinely manufactured and delivered for each patient and unutilized implants are available for analyses. This offers the unique opportunity to correlate molecular parameters with clinical data of the respective patients. This will enable to establish a panel of cellular markers that help to evaluate and to determine the quality of tissue-engineered matrices. In addition, the knowledge of the critical parameters determining a positive clinical outcome will facilitate the optimization of cell-seeded matrices.