Immunohistochemistry at 24 and 52 weeks. Safranin O staining (a, e), immunostaining for type II collagens (b, f), immunostaining for type X collagens (c, g), and IgG staining as controls (d, h) at 24 weeks (a–d) and 52 weeks (e–h). No positive Immunostaining for type X collagens was observed in the implanted area during the regeneration period. Scale bar =200 μm. Representative subjects of three experiments for each time course are shown.