Cartilage regeneration by transplantation of aggregates of BM MSCs in rats.

(A) Schema for the study. BM MSCs were obtained from GFP transgenic rats. Three days before the surgery, passage 2 GFP positive MSCs were aggregated by hanging drop culture. Osteochondral defect was created in the knee joint. For the MSC group, 4 aggregates were transplanted to the defect. For the control group, the defect was left empty. (B) Protocol for evaluation. (C) Macroscopic observation of osteochondral defects after aggregate transplantation. For the MSC group, 4 aggregates were transplanted to the defect. For the control group, the cartilage defect was left empty. White arrows indicate aggregates of BM MSCs. (D) Macroscopic score for cartilage [43]. Averaged score with standard deviation is shown (n = 7, *p<0.05 by the Mann–Whitney U test). (E) CT images. (F) Sagittal sections stained with Safranin-O/Fast Green. (G) Histological score by Wakitani et al. (S2 Table) [44]. Averaged score with standard deviation is shown (n = 7, *p<0.05 by the Mann–Whitney U test).