Histological findings of the meniscus at 4 weeks. (A) Hematoxylin and eosin staining. (B) Safranin O staining: the injured site of the miR-210 group was filled with repaired tissue stained with safranin O, while that of the control group was not repaired. Upper panels, best result; lower panels, worst result (bar = 100 μm). (C) Histological score of the miR-210 group (2.3 ± 0.8 points) was significantly higher than that of the control group (1.0 ± 1.0 point) (*P < 0.05, n = 6 for each group). (D) Detection of fluorescein amidite (FAM)-labeled double-stranded (ds) miR-210: distribution of green fluorescence was observed in the meniscus around the injured site 24 hours after injection of the FAM-labeled ds miR-210/atelocollagen complex into the joint (bar = 100 μm). Expression of green fluorescence was observed in the cytoplasm of cells in high-power views (bar = 25 μm). Arrows, FAM-labeled ds miR-210/atelocollagen complex. DAPI, 4′,6-diamidino-2-phenylindole.