Compression and tension variably alter Osteoprotegerin expression via miR-3198 in periodontal ligament cells

Hiroyuki Kanzaki,Kanako Itohiya,Satoshi Wada,Koji Noda,Sari Fukaya,Yutaka Miyamoto,Yoshiki Nakamura,Yuuki Yamaguchi,Tsuyoshi Narimiya,Yuta Katsumata

doi:10.1186/s12860-019-0187-2

Abstract

BackgroundOsteoclasts play a critical role in bone resorption due to orthodontic tooth movement (OTM). In OTM, a force is exerted on the tooth, creating compression of the periodontal ligament (PDL) on one side of the tooth, and tension on the other side. In response to these mechanical stresses, the balance of receptor activator of nuclear-factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) shifts to stimulate osteoclastogenesis. However, the mechanism of OPG expression in PDL cells under different mechanical stresses remains unclear. We hypothesized that compression and tension induce different microRNA (miRNA) expression profiles, which account for the difference in OPG expression in PDL cells.To study miRNA expression profiles resulting from OTM, compression force (2 g/cm2) or tension force (15% elongation) was applied to immortalized human PDL (HPL) cells for 24 h, and miRNA extracted. The miRNA expression in each sample was analyzed using a human miRNA microarray, and the changes of miRNA expression were confirmed by real-time RT-PCR. In addition, miR-3198 mimic and inhibitor were transfected into HPL cells, and OPG expression and production assessed.ResultsWe found that certain miRNAs were expressed differentially under compression and tension. For instance, we observed that miR-572, − 663, − 575, − 3679-5p, UL70-3p, and − 3198 were upregulated only by compression. Real-time RT-PCR confirmed that compression induced miR-3198 expression, but tension reduced it, in HPL cells. Consistent with previous reports, OPG expression was reduced by compression and induced by tension, though RANKL was induced by both compression and tension. OPG expression was upregulated by miR-3198 inhibitor, and was reduced by miR-3198 mimic, in HPL cells. We observed that miR-3198 inhibitor rescued the compression-mediated downregulation of OPG. On the other hand, miR-3198 mimic reduced OPG expression under tension. However, RANKL expression was not affected by miR-3198 inhibitor or mimic.ConclusionsWe conclude that miR-3198 is upregulated by compression and is downregulated by tension, suggesting that miR-3198 downregulates OPG expression in response to mechanical stress.

Highlights

Osteoclasts play a critical role in bone resorption due to orthodontic tooth movement (OTM)
Results miRNA expression is mediated by mechanical stress We examined miRNA expression in human periodontal ligament (PDL) (HPL) cells in three different groups using a microarray
MiRNAs targeting OPG are regulated by mechanical stress Since OPG expression is regulated by mechanical stress in OTM, we investigated whether miRNAs upregulated by mechanical stress were miRNAs predicted to target OPG. miRNAs that target OPG were predicted by two databases (Table 2). miR-1207 was on neither list; an miR-1207 mimic and inhibitor were used as negative controls

Summary

Introduction

Osteoclasts play a critical role in bone resorption due to orthodontic tooth movement (OTM). In OTM, a force is exerted on the tooth, creating compression of the periodontal ligament (PDL) on one side of the tooth, and tension on the other side. In response to these mechanical stresses, the balance of receptor activator of nuclear-factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) shifts to stimulate osteoclastogenesis. The mechanism of OPG expression in PDL cells under different mechanical stresses remains unclear. Compression induces RANKL expression [6,7,8,9] and reduces OPG expression [10, 11] in PDL cells, thereby increasing the RANKL/OPG ratio, and favoring RANKL-mediated osteoclastogenesis. The mechanism regulating OPG expression in PDL cells under different mechanical stresses remains unclear

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