Figure 4.

Histological evaluation of defects via HE staining and IHC staining with collagen II. For HE staining in the gel-cell complex group: (A) At week 4, the surfaces were slightly irregular and filled with cartilaginous and fibrous tissue; (B) at week 8, the surfaces were much smoother, and most parts of the defects were filled with cartilaginous and fibrous tissue; (C) and at week 12, the surface became very smooth, and the superficial layer was repaired with cartilage and the deeper layer was remodelled with bone or osseous-like tissue. For HE staining in the gel only group: (D) At week 4, the surfaces were irregular and filled with fibrous tissue but not cartilaginous and/or osseous tissue; (E) at week 8, the surfaces were still irregular, and most parts of the defects were filled with fibrous or osseous-like tissue; (F) at week 12, the surfaces were smooth and repaired with mostly osseous-like tissue and some fibrous tissue without any cartilage tissue (phase contrast, ×100). For IHC staining in the gel-cell complex group: (G) At week 4, the cartilage layer was stained with type II collagen at a low intensity; (H) at week 8, the cartilage layer was stained with type II collagen at a much higher intensity; (I) at week 12, the cartilage layer was stained with type II collagen at a high intensity. For IHC staining in the gel only group: (J) At week 4, type II collagen staining was negative, and no Pluronic F-127 gel was found on the surface. The same was observed at (K) 8 weeks and (L) 12 weeks post-surgery. HE, hematoxylin and eosin; IHC, immunohistochemical.