Background
The pathogenesis of Temporomandiblar joint(TMJ) osteoarthritis(OA) remains controversial. Imbalance between chondrocyte-controlled reparative processes and degradative processes is considered an important etiologic factor of TMJ OA. The individual groups characterized by the combination of single-nucleotide polymorphisms(SNPs) in the mitochondrial DNA(mtDNA) sequence are called mtDNA haplogroup.  In OA, mitochondrial dysfunction compromises the function of chondrocytes, increases inflammatory responsiveness to cytokines of the chondrocytes, and induces the apoptosis of chondrocyte. This study tried to investigate the association between TMJ OA and mtDNA haplogroups among Korean.

Methods
We recruited 108 patients from Yonsei University Dental Hospital. Buccal swab samples were collected, and DNA was extracted using the QIAamp® DNA Mini Kit. The extracted DNA was analyzed using PCR system to distinguish mtDNA haplogroups M, G, D, D4, D5, M7, M8, M9, M10, N, A, N9, R, F, and B, as well as the D4 subhaplogroups. The genotyping of PCR products was carried out using AB GeneMapper ® ID Software.
Haplogroups of the TMJ OA groups and control group were compared using the chi-square test. 

Results
The frequency of haplogroup M10 and D4j was higher in TMJ OA group than in control group. Frequency of haplogroup D4 was lower in TMJ OA group than in control group.

Conclusion
This is the first study to examine and identify the association between TMJ OA and mtDNA haplogroups in a Korean population. Polymorphisms of these mtDNA haplogroups could be a promising target for ascertaining the pathogenesis of TMJ OA and finding new therapeutic approaches to TMJ OA.

ASSOCIATION BETWEEN TEMPOROMANDIBULAR JOINT OSETOARTHRITIS AND MITOCHONDRIAL DNA HAPLOGRUPS IN A KOREAN POPULATION