Figure 2

Microarray analyses of gene expression of osteoarthritis and non-osteoarthritis of subchondral bone and qRT-PCR validation in osteoarthritis knee subchondral bone. (A) Differentially expressed genes were classified based on their expression levels with a minimum of twofold, threefold, fourfold, sixfold, and eightfold changes. (B) Unsupervised hierarchical clustering of osteoarthritis (OA) and non-OA samples was performed for genes whose differential expression exceeded twofold (972 genes). Distances between samples were detected with a Euclidean algorithm and clustered with a centroid linkage method. The OA medial tibial (MT) samples (gray) were clustered together and clearly separated from the OA lateral tibial (LT) (brown) and non-OA samples. Non-OA LT samples (N-LT, red) and non-OA MT samples (N-MT, blue) were clustered together with OA LT samples. (C) Eighty-five genes (plus GAPDH) were selected for quantitative reverse-transcription polymerase chain reaction (qRT-PCR) validation on a separate group of nine OA subchondral bone specimens. The results of qRT-PCR were strongly consistent with those of microarray analysis (R² = 0.5764, P <0.0001). FC, fold-change.