Microarray analysis of cartilage and subchondral bone. (A) Frontal hematoxylin-safranin O stained section of the tibia articular cartilage and subchondral bone isolated from a wild-type C57Bl/6 mouse at six weeks of age. Dissected tissues include the articular cartilage (AC), the underlying subchondral bone (SB) containing trabeculae and bone marrow and the upper part of the growth plate (GP). Scale bar = 50 μm (B) Heatmap showing the correlation between the Robust Multiarray Averaging (RMA) expression values for all samples. The three wild-type (WT) and one heterozygous frizzled-related protein (Frzb+/-) (HZ) mouse cluster apart from the two Frzb-/- (KO) mice. Correlations are presented by colors going from green (lowest) to red (highest). (C) Analysis of the representation of genes in the microarray associated with articular cartilage (collagen type 2a1 (Col2a1), collagen type 9a1 (Col9a1), aggrecan, chondromodulin, cartilage oligomeric matrix protein (Comp)), bone (osteopontin, osteocalcin, collagen type 1a1 (Col1a1), bone sialoprotein 2 (Ibsp), tartrate-resistant acid phosphatase type 5 (Acp5)), and hematopoiesis (B-lymphocyte antigen CD20 (Ms4a1), B-cell progenitor kinase (Btk), lymphoid-restricted immunoglobulin octamer-binding protein (Pou2f2), CD3 antigen (CD3), CD8 antigen (CD8), protein tyrosine phosphatase, receptor type C (CD45)). Cartilage- and bone-specific genes were found in the highest percentiles, while T cell, B cell and platelet related genes, were found in lower amounts.