Mechanical strain induces Cbfa1 and type X collagen expression in mandibular condyle.

Core binding factor a1 (Cbfa1) is a crucial transcriptional factor for chondrocyte maturation and osteoblast differentiation in the mandibular condyle. To quantitatively assess the amount of mRNA expression of Cbfa1 and type X collagen in response to mandibular advancement. 420, 35-day-old female Sprague-Dawley rats, were randomly divided into 20 experimental and 10 control groups corresponding to 10 time points. Experimental animals were advanced in either single or stepwise manner. Condylar cartilage was dissected under microscope and total RNA was extracted, Cbfa1 and type X collagen mRNA was quantified with real-time RT-PCR. Cbfa1 and type X collagen mRNA expression for all groups reached their peak on experimental day 21. During single advancement, Cbfa1 and type X collagen mRNA expression was consistently higher (3-fold and 2.8-fold respectively) than that of stepwise advancement (2-fold). The second advancement in the stepwise group resulted in both Cbfa1 and type X collagen level reaching another peak on day 51. Mandibular advancement promoted chondrocytes maturation and osteoblast differentiation by upregulating Cbfa1 expression. Stepwise advancement produced a higher level of Cbfa1 and type X collagen expression leading to bigger cartilage template onto which bone will form through endochondral ossification.