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

Purpose: 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. Material and Methods: 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 Affymelrix 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 sutficiant quality which was validated using capillary electropboresis. RNA collected from 8 test animals of die 4 age groups respectively was mixed in equimolar RNA pools which served for the wanscriptome analyses using Affymetrix arrays. Results: 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, epoptosis and bone remodelling. Conclusion: 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. [ABSTRACT FROM AUTHOR]