Fig. 2.

Development of the hypertrophic cartilage tissues following in vivo implantation. The differentiation of cartilaginous constructs in vivo progressed according to their stage of in vitro maturation. (A, E, and I) Four weeks after implantation, early hypertrophic samples had differentiated further toward hypertrophy, displaying larger lacunae, Col X accumulation, and initiated BSP deposition in the outer rim. (B, F, and J) Eight weeks after implantation, early hypertrophic samples had differentiated even further. This was evidenced by a decrease in GAG accumulation, while Col X was maintained and BSP had also been deposited within the cartilaginous core. (C, G, and K) After 4 weeks, late hypertrophic specimens had undergone more intense remodeling, such that GAG and Col X levels were reduced, while BSP had already been deposited within the cartilaginous core. (D, H, and L) After 8 weeks, the cartilaginous template was almost completely resorbed: Bone structures substituted the GAG positive areas in the central region, while Col X and BSP positive areas were restricted to scattered islands. All the pictures were taken at the same magnification. (Scale bar: 200 μm.)