Cyclic Stretch Enhances Osteogenic Differentiation of Human Periodontal Ligament Cells via YAP Activation

Abstract

Periodontal remodeling and alveolar bone resorption and formation play essential roles during orthodontic tooth movement (OTM). In the process, human periodontal ligament cells (HPDLCs) sense and respond to orthodontic forces, contributing to the alveolar bone formation. However, the underlying mechanism in this process is not fully elucidated. In the present study, cyclic stress stimulus was applied on HPDLCs to mimic the orthodontic forces during OTM. Our results demonstrated that cyclic stretch promoted the osteogenic differentiation of HPDLCs. Moreover, our data suggested that yes-associated protein (YAP), the Hippo pathway effector, which also involved in mechanical signaling transduction, was activated as we found that the nuclear translocation of YAP was significantly increased in the cyclic stress treated HPDLCs. The mRNA expression of CTGF and CYR61, the target genes of YAP, was also remarkably increased. Furthermore, knockdown of YAP suppressed the cyclic stretch induced osteogenesis in HPDLCs, while overexpression of YAP in HPDLCs enhanced osteogenesis. We also noticed that YAP activities could be suppressed by the ROCK and nonmuscle myosin II inhibitors, Y-27632 and Blebbistatin. The inhibitors also significantly inhibited the cyclic stretch induced osteogenesis in HPDLCs. Finally, in the murine OTM model, our results revealed that YAP was upregulated and nuclearly translocated in the PDLCs at the tension side. In summary, our present study demonstrated that cytoskeleton remodeling induced activation of YAP signaling pathway was crucial for the cyclic stretch-induced osteogenesis of HPDLCs, which might play important roles during OTM.

Intermittent compressive force promotes osteogenic differentiation in human periodontal ligament cells by regulating the transforming growth factor-β pathway

“…Mechanical stimulation, such as shear, tensile, centrifugation, and vibration, has been shown to regulate osteogenic differentiation [28][29][30][31][32] . Cyclic tensile strain significantly enhanced RUNX2 and OSX expression in human periodontal ligament stem cells (hPDLSCs) 33 .…”

“…Cyclic tensile strain significantly enhanced RUNX2 and OSX expression in human periodontal ligament stem cells (hPDLSCs) 33 . Cyclic stretching upregulated ALP enzymatic activity and osteogenic marker gene expression through the YAP, ROCK, and myosin remodeling pathways 32 . In addition, Wnt signaling also contributed in the hydrostatic force-induced ALP enzymatic activity as well as RUNX2 and OSX mRNA expression in hPDLSCs 31 .…”

Role of YAP/TAZ in Cell Lineage Fate Determination and Related Signaling Pathways

“…Besides substrate stiffness and surface topography, various biophysical stimuli also modulate osteogenesis via YAP/TAZ. These include mechanical stimuli, such as cyclic stretching ( Yang et al, 2018 ), shear stress ( Kim et al, 2014 ), acoustic tweezing ( Xue et al, 2017 ), pH ( Tao et al, 2016 ), microgravity ( Chen et al, 2016 ) and light ( Feng et al, 2015 ). Various exogenous growth factors and protein ligands, such as IRS-1 (insulin receptor substrate 1) ( Wang N. et al, 2018 ), FGF2 (fibroblast growth factor-2) ( Byun et al, 2014a ), CTHRC1 (collagen triple helix repeat containing 1) ( Wang C. et al, 2017 ), FBLN1 (fibulin-1) ( Hang Pham et al, 2017 ), IGF1 (insulin-like growth factor 1) ( Xue et al, 2013 ), and TGF-β1 (transforming growth factor beta one) promote osteogenesis via TAZ activation ( Zhao et al, 2010 ).…”

Mechanistic Insight into Orthodontic Tooth Movement Based on Animal Studies: A Critical Review

“…Yes-associated protein (YAP) and the paralogue transcriptional coactivator with PDZ-binding motif (TAZ), the downstream effectors of the Hippo signaling pathway, have been identified as important regulators during mechanotransduction [ 61 ]. Recent rodent OTM studies showed that YAP and TAZ expression were up-regulated with nuclear translocation in the PDL cells on both compression and tension side [ 62 , 63 ]. Moreover, YAP and TAZ expression were proportional to the applied orthodontic force.…”

“…On the tension side, the same transgenic mice with the YAP deletion in Gli1+ cells showed a significantly decreased proportion of Runx2+ cells by more than 80%. In vitro cyclic stretch promoted the osteogenic differentiation of human PDL cells [ 62 ]. Moreover, the nuclear translocation of YAP was significantly increased with increased expression of connective tissue growth factor (CTGF) and cysteine-rich angiogenic inducer 61 (CYR61) mRNA, the target gene of YAP.…”