Development of an improved protocol to analyse gene expression in temporomandibular joint condylar cartilage of rats...

During recent years, gene expression analyses based on DNA chip technologies have allowed for the genome-wide identification of genes potentially associated with growth processes in a variety of organs. The present study aims to identify genes differentially expressed in the growing temporomandibular joint cartilage by means of transcriptome analyses.

In total, the condylar cartilage of 32 rats comprising 4 age groups (newborn, 10 days, 21 days, 8 weeks) were used for analysis. Transcriptome analyses were carried out using Affymetrix Expression Arrays (Rat Genome 230 2.0 Arrays). The availability of high-quality RNA preparations from homogeneous tissue samples is a fundamental precondition of successful transcriptome analyses using DNA arrays. An optimised preparation protocol allowed RNA isolation of sufficient quality which was validated using capillary electrophoresis. RNA collected from 8 test animals of the 4 age groups respectively was mixed in equimolar RNA pools which served for the transcriptome analyses using Affymetrix arrays.

Statistical analysis of the gene expression data indicated the existence of genes differentially regulated in the growing temporomandibular cartilage. This evidence, however, requires validation by RT-PCR using individual animals' RNA. Preliminary candidate genes belong, among others, to the groups of matrix-degrading proteases, protease inhibitors and genes involved in cell growth, apoptosis and bone remodelling.

These differentially expressed genes in TMJ growth identified using DNA array technology may possibly contribute to a better understanding of growth biology and provide an approach to necessary therapy.