Objective: This study was designed to detect type X collagen expression, at both gene and protein levels, in condylar cartilage during mandibular protrusion triggered by functional appliance.
Methods: One hundred SD rats with age of 5 weeks were selected and divided into 5 experimental groups (n = 5) and 5 control groups (n = 5). Animals in experimental groups were imposed with bite-jumping appliances which caused identical magnitude of mandibular protrusion. The animals of experimental groups, together with their matched controls, were sacrificed 3, 7, 14, 21 and 30 days after the appliance insertion. 6 microns sections were cut from TMJ through the sagittal plane. In situ hybridization and immunohistochemical analysis were performed to detect the expression of type X collegen mRNA transcription and its protein synthesis.
Results: 1. Intensive staining of type X collegen mRNA was found to distribute within the whole area of hypertrophic zone, a sharp contrast to the control groups which showed very little or no staining. 2. Type X collegen protein synthesis, which was highlighted by immunofluoscent staining, was found to spread over the whole hypertrophic zone, compared to the controls that demonstrated a very little staining.
Conclusion: Expression of type X collagen in condylar cartilage indicates the onset of endochondral ossification in condyle in response to mandibular protrusion provoked by functional appliances.