Tensile stress on the expression of Sox 9 and subsequent release of Type II collagen in a synchondrosis

Abstract

AIM: To evaluate the expression of SOX 9 and the associated release of type II collagen, at the molecular level, in the spheno-occipital synchondroses upon application of tensile stress across the mouse cranial base in vitro. MATERIALS AND METHOD: Fifty newborn male BALB/c mice were sacrifi ced and the spheno-occipital synchondroses were aseptically excised and randomly assigned to fi ve control and experimental groups. Each group was divided into fi ve time points. In the experimental groups, mechanical force was applied across the synchondroses, using helical springs. For the control groups, the springs were not activated. Both groups were incubated in 24 well plates and cultured for 6, 24, 48, 72 and 168 hours. In situ hybridisation was undertaken for quantitative analysis of SOX 9 and type II collagen expression. RESULTS: Quantitative analysis revealed that SOX9 and type II collagen expressions reached a peak at 24 and 72 hours, respectively. Compared with the control groups, the experimental groups of both SOX9 and type II collagen were consistently higher at all time points. Application of tensile stress across the spheno-occipital synchondroses increased the expression of SOX 9 and subsequently up regulated the expression of type II collagen, which is a major component of the extracellular matrix. CONCLUSIONS: Application of mechanical force could enhance growth of the spheno-occipital synchondroses and points to the effect of growth of epigenetic structures such as the brain on the growth of the spheno-occipital synchondrosis.