Screening the Expression Changes in MicroRNAs and Their Target Genes in Mature Cementoblasts Stimulated with Cyclic Tensile Stress

Cementum is a thin layer of cementoblast-produced mineralized tissue covering the root surfaces of teeth. Mechanical forces, which are produced during masticatory activity, play a paramount role in stimulating cementoblastogenesis, which thereby facilitates the maintenance, remodeling and integrity of cementum. However, hitherto, the extent to which a post-transcriptional modulation mechanism is involved in this process has rarely been reported. In this study, a mature murine cementoblast cell line OCCM-30 cells (immortalized osteocalcin positive cementoblasts) was cultured and subjected to cyclic tensile stress (0.5 Hz, 2000 µstrain). We showed that the cyclic tensile stress could not only rearrange the cell alignment, but also influence the proliferation in an S-shaped manner. Furthermore, cyclic tensile stress could significantly promote cementoblastogenesis-related genes, proteins and mineralized nodules. From the miRNA array analyses, we found that 60 and 103 miRNAs were significantly altered 6 and 18 h after the stimulation using cyclic tensile stress, respectively. Based on a literature review and bioinformatics analyses, we found that miR-146b-5p and its target gene Smad4 play an important role in this procedure. The upregulation of miR-146b-5p and downregulation of Smad4 induced by the tensile stress were further confirmed by qRT-PCR. The direct binding of miR-146b-5p to the three prime untranslated region (3' UTR) of Smad4 was established using a dual-luciferase reporter assay. Taken together, these results suggest an important involvement of miR-146b-5p and its target gene Smad4 in the cementoblastogenesis of mature cementoblasts.