Expression of Egr-1 in normal and OA cartilage. (a) RNA was extracted from normal (n = 9) and OA (n = 9) cartilage, reverse-transcribed into cDNA, and processed for real-time polymerase chain reaction. The threshold cycle values were converted to the number of molecules. Data were expressed as copies of the gene's mRNA detected per 10,000 glyceraldehyde-3-phosphate dehydrogenase (GAPDH) copies. *P < 0.05 versus normal samples. (b) Percentage of chondrocytes expressing Egr-1 in normal and OA cartilage. The results are the mean ± standard deviation of nine normal and nine OA specimens. *P < 0.05 versus normal cartilage. Representative immunostaining of human normal (c) and OA (d) cartilage for Egr-1 protein. Egr-1, early growth response gene 1; OA, osteoarthritis.