Temporal expression of SOX9 and type II collagen in spheno-occipital synchondrosis of mice after mechanical tension stimuli

OBJECTIVE: To associate the expressions of SOX9 and type II collagen during growth in the synchondrosis with and without tensile stress in order to understand the role of these factors in the growth of cartilage in spheno-occipital synchondrosis. MATERIALS AND METHODS: Sixty 1-day-old male BALB/c mice were randomly divided into experimental and control groups. Each group was subdivided again into five different time points which were 6, 24, 48, 72, and 168 hours. Each subgroup consisted of five mice. Each mouse was sacrificed using an overdose of pentobarbitone sodium. The synchondroses were aseptically removed and incubated in a 24-well plate with or without tensile stress in tissue culture. Tissue sections were stained immunohistochemically to quantitatively analyze the expression of SOX9 and type II collagen. RESULTS: There was a statistically significant increase of 57% (P < .001) in the expression of SOX9 between the experimental and control groups at 24 hours, followed by a significant increase of 44.4% (P < .001) in the expression of type II collagen at 72 hours. CONCLUSIONS: SOX9 may play an important role for early differentiation of chondrocytes and increase the expression of type II collagen, a major component of the extracellular matrix, during the growth of cartilage in the spheno-occipital synchondrosis.