Microarray analysis of chondrogenic genes in condylar cartilage

Abstract

AIM: To investigate chondrogenic gene expression changes in mandibular condylar cartilage under mechanical strain. MATERIALS AND METHOD: Two hundred and eighty, 35-day-old, female Sprague-Dawley rats randomly divided into seven experimental and seven control groups. The experimental groups were fi tted with bite-jumping appliances. Each group of rats was killed on the following experimental days: 1, 3, 7, 9, 14, 30 and 33. Immediately after sacrifi ce, the condyles were dissected and total RNA was extracted to oligonucleotide microarray gene chips containing 15,923 genes. After a series of microarray data analyses, genes were excluded if absent across all time points in both groups. All genes that were either unchanged or whose expression was changed less than ×2 in relation to the control group were excluded from further analyses. This selection resulted in a net of 1,082 genes, 666 were increased in expression, and 416 decreased in expression, at least a two-fold changed. This group of genes was further analyzed using hierarchical clustering and selforganizing maps, and resulted in the identifi cation of numerous genes not previously known to be regulated in condylar cartilage during chondrogenesis under mechanical strain. RESULTS: Sixteen genes were involved in chondrogenesis. To focus on these genes that were more specifi c to chondrogenesis, the results were validated by both RT-PCR and immunostaining. CONCLUSIONS: Using microarray technology to analyze the gene expression of mandibular condylar cartilage under mechanical strain, some chondrogenic regulating factors involved in condylar cartilage growth were identified.