Histological analysis of second-look biopsy tissue from patients treated with BioSeed®-C. At 9 to 12 months after implantation, second-look biopsy tissue was stained for proteoglycans with alcian blue. One patient's biopsy tissue showed the formation of mixed repair tissue (a-d) with areas of fibrocartilage ((c), black triangle) and hyaline-like cartilage ((c), white triangle) and a firm bonding to the subchondral bone that was undergoing remodeling ((c), asterisk). Biopsy tissue from three patients (e-j) shows the formation of a hyaline-like cartilaginous repair tissue with intense staining of proteoglycans by alcian blue (e-h), good integration with the underlying bone tissue (f), viable, round cells within lacunae (g) and a smooth surface (h). Chondrocytes showed a columnar distribution and some clustering (g-j). Hematoxylin/eosin staining (i, j) of biopsy tissue of two patients confirmed the presence of viable chondrocytes and the absence of abnormal calcification, apoptosis, necrosis or formation of a fibrous repair tissue.