*2.8. Arthroscopic and Histological Analysis*

Second-look arthroscopy was done with the patients' written consent. Alcian blue staining and immunohistology were applied to evaluate the existence of GAG and collagen type II. The International Cartilage Repair Society (ICRS) arthroscopic assessment scale was used to evaluate the degree of cartilage repair [49,50]. Alcian blue staining (Cat. No. B8438, Sigma-Aldrich, Saint Louis, MO, USA) was used to assess the amount of GAG accumulation in the implanted tissues. Nuclear Fast Red solution (Cat. No. H-3403, Vector Laboratories, Burlingame, CA, USA) was used for counterstaining. The immunohistochemistry was applied to quantify the protein expression level of collagen type II. An anti-collagen type II antibody (Cat. No. Ab34712, Abcam, Cambridge, UK) and UltraVision Quanto Detection System (Cat. No. TL-060-QHL, Thermo Scientific, Fremont, CA, USA) were used for the immunohistochemistry, according to the manufacturer's instructions. All samples were processed and stained using the same procedure.
