Osteoarthritis score. The histopathology of the OA cartilage samples from all 4 groups (n = 24) were analyzed according to standard grading and staging of OA cartilage histopathology. OA scores were calculated by using the following formula: OA score = most degenerated site in the cartilage (grades 1-6, Table 1) × area of degeneration (stages 1-4) (Table 2). Error bars indicate the standard deviation of each group. Statistically significant differences were observed between the control and hTERT + GRP78 groups 8 and 16 weeks after transplantation.