Fig. 1

Histological and immunohistochemical analysis of chondrogenic differentiation and hypertrophic differentiation in mesenchymal stromal cells after incubation with R57A, GDF-5 and TGF-ß1 21 days in pellet culture. Mesenchymal stromal cells (MSCs) were incubated with 500 ng/ml (a) and 1000 ng/ml (b) of the mutant R57A, 500 ng/ml (c) and 1000 ng/ml (d) of growth and differentiation factor 5 (GDF-5) or transforming growth factor beta (TGF-β)1 (e) in pellet cultures for 21 days. Untreated cultures treated with standard cell culture medium were maintained as negative controls (f). Clear signs of chondrogenesis as judged by histological Alcian Blue stainings and immunohistochemical stainings of Collagen type II (Collagen II) were observed in all pellet cultures treated with R57A, GDF-5 and TGF-ß1 (Alcian Blue, Collagen II, a-e) while internal controls showed no positive staining (Alcian Blue, Collagen II, f). All cultures showed slightly positive immunohistochemical stainings of the hypertrophy marker collagen type X (Collagen X, a-e). Representative samples were captured at low (50x; black bar = 100 μm) and high (200x; black bar = 50 μm) magnification. GDF-5, growth and differentiation factor 5; MSCs, mesenchymal stromal cells; TGF-ß transforming growth factor beta