Association of Proinflammatory Gene Polymorphisms With Pain-Related Temporomandibular Disorder

Objectives: Studies have already pointed out the association between polymorphisms in inflammatory genes and pain-related temporomandibular disorders (TMDp), but results remain conflicting. Therefore, in order to further elucidate, we investigated the association between polymorphisms in cytokine and chemokine genes with TMDs.
Methods: Study involved 170 individuals:85 TMDp patients, diagnosed according to DC/TMD, and 85 healthy controls. Intensity of orofacial pain was measured through Characteristic Pain Intensity (CPI) score from Graded Chronic Pain Scale, whereas TMD patients with CPI>50 were considered as a high pain intensity group (HPI). Genomic DNA was extracted from buccal mucosa swabs. Single nucleotide polymorphisms (SNPs) in genes encoding interleukin 8 (CXCL8; rs2227306, rs2227307), transforming growth factor β (TGFB1, rs4803455) and tumour necrosis factor-alpha (TNF, rs1800629) were analysed by real time-PCR using Taqman Genotyping assays. Assessment was performed according to dominant and recessive genetic models where minor allele represented the risk allele. Chi-Square Test, Fisher's Exact Test and Mann-Whitney U test were used for data analysis.
Results: The frequency of patients carrying minor allele G of rs2227307 was higher in TMDp patients than in CTRs (70% vs. 55%, p=0.041). Carriers of minor allele G and T of rs2227307 and rs2227306 respectively were significantly more represented in HPI group when compared to the rest of participants (75% vs. 57%, p=0.023; 71% vs. 55%, p=0.047, respectively). Also, TMDp subjects carrying GG+GT of rs2227307 polymorphism reported significantly shorter pain duration in last 6 months (80 vs.112 days, p=0.041) and significantly higher worst facial pain (7.3 vs. 6.5, p=0.031) compared to the subjects with the TT genotype.
Conclusions: Certain SNPs may predict pain intensity and chronicity in TMDp patients. Our results support the association between SNPs in pro-inflammatory chemokine genes and TMDp, highlighting the potential utility of genetic testing in predicting pain severity. Further research is needed to confirm these findings and explore underlying mechanisms.