Fig. 3

Safranin-O staining and type-2 collagen immunohistochemical staining at 2, 4, and 12 weeks. At 2 weeks, all defects were filled with fibrous tissue. In the defects in G-I with DN gel and the untreated controls, and G-II with DN gel, some tissue was stained with Safranin-O. At 4 weeks, the defects in G-I with DN gel and the untreated controls and G-II and III with DN gel were filled with a sufficient volume of proteoglycan-rich tissue with regenerated sub chondral bone tissue. At 12 weeks, the histology showed similar findings to that at 4 weeks in all groups, while the area and degree of the Safranin-O staining were reduced in the defects in G-III with DN gel. Immunohistochemical staining for type-2 collagen were consistent with the Safranin-O staining. Black scale bar = 1 mm