Histology of normal donor and osteoarthritic chondrocyte pellet cultures. Chondrogenic differentiation of chondrocytes obtained from (a, c, e) normal donors (ND) and (b, d, f) osteoarthritic (OA) articular cartilage using the high-density pellet culture system. (a, b) Alcian Blue van Gieson staining and immunohistochemical localization of (c, d) collagen type I and (e, f) type II. (g) Bern Score evaluating the differentiation grade of the cells. Three cultures per donor group.