Microarray Analysis of Differential Gene Expression Between Traumatic Temporomandibular Joint Fibrous and Bony Ankylosis in a Sheep Model

BACKGROUND: The type of traumatic temporomandibular joint (TMJ) ankylosis depends on the degree of severity of TMJ trauma. Here, we performed comprehensive differential molecular profiling between TMJ fibrous and bony ankylosis. MATERIAL/METHODS: Six sheep were used and a bilateral different degree of TMJ trauma was performed to induce fibrous ankylosis in one side and bony ankylosis in the other side. The ankylosed calluses were harvested at days 14 and 28 postoperatively and analyzed by Affymetrix OviGene-1_0-ST microarrays. DAVID was used to perform the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis for the different expression genes (DEGs). The DEGs were also typed into protein–protein interaction (PPI) networks to get the interaction data. Ten DEGs, including 7 hub genes from PPI analysis, were confirmed by real-time PCR. RESULTS: We found 90 and 323 DEGs at least 2-fold at days 14 and 28, respectively. At day 14, bony ankylosis showed upregulated DEGs, such as TLR8, SYK, NFKBIA, PTPRC, CD86, ITGAM, and ITGAL, indicating a stronger immune and inflammatory response and cell adhesion, while genes associated with anti-adhesion (PRG4) and inhibition of osteoblast differentiation (SFRP1) had higher expression in fibrous ankylosis. At day 28, bony ankylosis showed increased biological process related to new bone formation, while fibrous ankylosis was characterized by a prolonged immune and inflammatory reaction. CONCLUSIONS: This study provides a differential gene expression profile between TMJ fibrous and bony ankylosis. Further study of these key genes may provide new ideas for future treatment of TMJ bony ankylosis.