Fig. 4

Histological and immunohistochemicasl assay of osteogenesis in cells after 21 days in monolayer cell culture. For inducing osteogenesis monolayer cultures containing BM-MSCs and MSC-like cells from hyaline cartilage, LCF and the joint capsule were incubated with osteogenic differentiation medium for 21 days. Contols were maintained in cell culture medium. Native, unstained tissue samples (a), Alizarin Red S stainings (b) for detection of extracellular calcium deposits and immunohistochemical stainings of collagen type I (Col I; c) from control and differentiatied samples were compared. From day 12 to day 21 dense deposits formed in differentiated monolayers and Alizarin Red S (a) as well as immunohistochemical stainings of Col I (c) were positive in all differentiated cell cultures in contrast to controls. Representative samples were captured at low (100x; black bar = 200 μm) and high (200x; black bar = 150 μm) magnification. Col I, collagen type I; d, days; diff., differentiation; LCF, ligamentum capitits femoris