Immunohistochemistry analysis of in vitro constructs. As shown in Figure 4A, fibrin/PLGA exhibited strong immunopositivity of collagen type II which mainly localized at the pericellular and inter-territorial matrix. Minimal collagen type II expression could be observed in the PLGA construct (Figure 4C). After 3 weeks, collagen type II expression was maintained in fibrin/PLGA (Figure 4E) and PLGA (Figure G). Collagen type I in fibrin/PLGA constructs showed moderate immunopositivity at week-2 (Figure 4B) and week-3 (Figure 4F), as did PLGA (Figure 4D, Figure 4H).