Cultivation of ATDC5 cells on fibroin biomaterials. (A) Comparison of cell viability on noncoated substrates (column a), gelatin-coated substrates (column b), and substrates coated with fibroin solutions prepared from degummed w1-pnd (column c), non-degummed Ser-P1A269 (column d), and Ser1/3-P1A269 (column e) cocoons by measuring the WST-8 reaction on the indicated day after cell seeding. Data are shown as the means ± SD; n = four independent samples; * p < 0.05 (one-way ANOVA, followed by Tukey’s test). (B) Early chondrogenic differentiation of ATDC5. The ATDC5 cells were cultured in a differentiation medium; on the indicated day, signs of early differentiation such as cartilage nodule formation were investigated by measuring the amount of glycosaminoglycan produced via Alcian blue staining. Data are shown as the means ± SD; n = four independent samples; *** p < 0.001 (one-way ANOVA, followed by Tukey’s test). (C) Late osteogenic differentiation of ATDC5 cells. During the late osteogenic differentiation of ATDC5, the mineralization of the extracellular matrix was assessed by alizarin red staining. Data are shown as the means ± SD; n = four independent samples (not significant by one-way ANOVA with Tukey’s test).