Regenerated hyaline-cartilage tissues (low magnification, x2). A and B: At 2 weeks, symmetrical triangular zones rich in cells were observed in a localized zone close to the bony wall and the implanted gel in the defect. A cartilage-like tissue rich in proteoglycan (A: Safranin-O stain) and type-2-collagen (B: Immunostaining) appeared in the triangular zones. C and D: At 4 weeks, the defect was filled with a sufficient volume of the tissue rich in proteoglycan (C: Safranin-O stain) and type-2-collagen (D: Immunostaining). E, F, G, and H: Control (untreated) specimens at 2 and 4 weeks. The defects were filled with fibrous and osseous tissues.