Role of microRNA-181a, 181b, 181c, and 181d in orthodontic tooth movement: A prospective cohort study

In recent times, noncoding RNAs have received increasing interest for their potential role in the molecular pathways of orthodontic tooth movement. This study was designed to evaluate microRNA (miRNA)181a, 181b, 181c, and 181d as potential biomarkers by measuring their expression in gingival crevicular fluid (GCF) during different phases of tooth movement.

GCF was collected from patients undergoing fixed appliance treatment at 4 time points: T0: Baseline (pretreatment), T1: 24 hours after force application (initial phase), T2: 7-14 days after force application (lag phase), and T3: 14-21 days after force application (log phase). Total RNA was isolated using the Qiagen miRNeasy kit (Qiagen, Hilden, Germany), quantified using NanoDrop (NanoDrop, Wilmington, Del), and converted to complementary DNA using the miScript Reverse Transcription kit (Qiagen). Quantitative real-time polymerase chain reaction was performed to assess the expression of miRNA-181a, 181b, 181c, and 181d. Statistical analyses included the Shapiro-Wilk test, the Friedman test, and Dunn's multiple comparison test.

All 4 miRNA-181 subtypes were expressed at baseline (T0) in GCF. After orthodontic force application, their expression progressively increased in subsequent phases. MiRNA-181b showed a significant rise at T1 (P = 0.013), and miRNA-181a showed a significant increase at T2 (P = 0.035). By T3, all 4 subtypes showed significantly increased expression compared with T0 (P <0.0001).

All 4 miRNAs were expressed throughout the study period from T0-T3 with progressive increase in expression from T0-T3. However, at each given time point (T0, T1, T2, and T3), there was no statistically significant difference among the subtypes. This study provides evidence that miRNA-181 subtypes function as potential biomarkers of orthodontic tooth movement.