Gene Expression of Proteoglycans in TMJ Disc of Growing Rats

Objectives: Proteoglycans are categorized into small leucine rich proteoglycans (SLRPs) and modular proteoglycans. Decorin, biglycan, fibromodulin and lumican belong to SLRPs. Versican, a modular proteoglycan produced by fibroblasts, is distributed in a variety of tissues, including cartilage, aorta, skin, tendon and brain, and has four splicing variants (V0, V1, V2, V3). Three proteoglycans are thought to be involved in extracellular matrix assembly and in biological interaction with cells. In this study, we examined gene expression and region specificity of SLRPs and versican in the temporomandibular joint (TMJ) disc of rats. Methods: Male growing Wistar rats were used as experimental animals. The TMJ disc were extracted and embedded in OTC compound. After the specimens were cut into 5ƒÝm-thick sagittal sections, samples from three different regions of the disc (anterior band, posterior band, and intermediate zone) were dissected by laser microdissection (LMD). For quantitative analysis of mRNA expression, total RNA was isolated from the TMJ discs. One step RT-PCR were performed with SYBR Green in GeneAmp 5700 Sequence Detection System. Copy number of mRNA was calculated by an external standard (plasmid including each cDNA diluted serially in log steps from 108 to 10 copies) and was normalized to a reference cDNA (GAPDH). Results: Quantitative RT-PCR analysis showed that mRNA expression of SLRPs in the TMJ disc, the expression level of biglycan was highest. In the anterior band, biglycan, fibromodulin and lumican gradually decreased with growing. In the posterior band and intermediate zone, in both showed similar dimension, biglycan, fibromodulin increased after 8 weeks. Expression level of V0, V1 and V3 gradually decreased with growing, and V2 peaked at 8 weeks. Conclusion: Gene expression of proteoglycans showed regional differences and age-related changes in the TMJ disc of growing rats.