Effect of tensile force on the expression of PTHRP in mouse synchondrosis

Abstract

AIM: To evaluate the level and temporal pattern of the expression of PTHrP, a key factor known to regulate the rate of maturation of chondrocytes, in mouse spheno-occipital synchondroses in response to tensile force. MATERIALS AND METHOD: The spheno-occipital synchondroses together with the adjacent structures were aseptically excised from 50 two-day-old BALB/c mice randomly divided into fi ve control and fi ve experimental groups (5 mice per groups). In the experimental group, a tensile force of 0.2 g was applied by helical springs across the spheno-occipital synchondroses; whereas in the control group, helical springs with no tension were used. Both groups were then cultured in serum-free BGJb medium for 6 hours and 1, 2, 3 and 7 days. The tissue were then fi xed and 5 μm sections were cut; fi ve sections from each mouse were used for identifying PTHrP level by immunohistochemical staining (n = 25) and measured with a computer-assisted image analyzing system by one operator. The difference in the level of expression was then analysed by t-test and one-way ANOVA. RESULTS: PTHrP expression in both the control and experimental groups increased at 24 hour after force application, then reduced at 48 hours and continued to reduce until the last day of the experiment. However, the change in the control group was not signifi cantly different at any time point, while the increase at 24 hours in the experimental group was statistically signifi cant (P < 0.05) as well as its decease at 48 hours (P < 0.01) which interestingly made its level signifi cantly lower than that of the control group (P < 0.01). CONCLUSION: Condrocytes in organ-cultured mouse spheno-occipital synchondrosis signifi cantly express more PTHrP in response to tensile force at 24 hours.