DIFFERENTIAL EXPRESSION OF miRNA 328 IN MASSETER MUSCLES OF SUBJECTS WITH FACIAL ASYMMETRY

Abstract

MicroRNAs regulate posttranscriptional expression of target genes leading to inhibition or degradation of mRNA therefore inhibiting synthesis of protein coding genes. We reported that miRNA genes associated with response to ion-channel/transporter functions are differentially expressed in masseter of subjects with facial asymmetry. We have selected one species, miRNA 328, to test whether its expression associates with malocclusion types, asymmetry and TMD among orthognathic surgery patients. RNA was isolated from muscle of patients undergoing mandibular sagittal-split surgical procedures for non-syndromic skeletal discrepancies. Subjects were diagnosed with one of the following types of malocclusion, with or without TMD and facial asymmetry: Class-II or Class-III with vertical normal, open or deep bite. A two-step process was used for quantification of miRNAs. RNA was reverse transcribed and assayed using specific TaqManTM primers and probe for microRNA 328. Standard curve experiments were used for assay analysis. MicroRNA 328 expression values were low, ranging from 1-80pg throughout. Quantifiable differences were detected in comparisons between parameter groups. Statistical significant associations (P<0.04) were found between female Class III and male Class III malocclusion subjects. In addition, interesting differences were identified among TMD-related myalgia groups with p<0.20, and between male Class II and male Class III malocclusion subjects. Power analyses were done to determine the sample sizes needed for each group to attain significance. MicroRNA 328 is differentially expressed in masseter of subjects with Class-II/Class-III malocclusion and in TMD-related myalgia. Larger sample sizes are needed to verify whether microRNA 328 expression acts in both disorders. By power analysis, to reach p<0.05 with a power =0.8, 60 samples are needed in both TMD and Non-TMD groups. Differential expression of microRNA 328 seen in Class III females and males suggests a potential influence on muscle target genes, craniofacial development and pain.