Effect of Different Parameters of In Vitro Static Tensile Strain on Human Periodontal Ligament Cells Simulating the Tension Side of Orthodontic Tooth Movement

Abstract

This study aimed to investigate the effects of different magnitudes and durations of static tensile strain on human periodontal ligament cells (hPDLCs), focusing on osteogenesis, mechanosensing and inflammation. Static tensile strain magnitudes of 0%, 3%, 6%, 10%, 15% and 20% were applied to hPDLCs for 1, 2 and 3 days. Cell viability was confirmed via live/dead cell staining. Reference genes were tested by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and assessed. The expressions of TNFRSF11B, ALPL, RUNX2, BGLAP, SP7, FOS, IL6, PTGS2, TNF, IL1B, IL8, IL10 and PGE2 were analyzed by RT-qPCR and/or enzyme-linked immunosorbent assay (ELISA). ALPL and RUNX2 both peaked after 1 day, reaching their maximum at 3%, whereas BGLAP peaked after 3 days with its maximum at 10%. SP7 peaked after 1 day at 6%, 10% and 15%. FOS peaked after 3 days with its maximum at 3%, 6% and 15%. The expressions of IL6 and PTGS2 both peaked after 1 day, with their minimum at 10%. PGE2 peaked after 1 day (maximum at 20%). The ELISA of IL6 peaked after 3 days, with the minimum at 10%. In summary, the lower magnitudes promoted osteogenesis and caused less inflammation, while the higher magnitudes inhibited osteogenesis and enhanced inflammation. Among all magnitudes, 10% generally caused a lower level of inflammation with a higher level of osteogenesis.

Effect of Tensile Frequency on the Osteogenic Differentiation of Periodontal Ligament Stem Cells

“… 49 Increased osteogenesis is usually accompanied by lower levels of inflammatory cytokines and chemokines. 10 , 50 , 51 Accordingly, in the present study, with increasing frequency, the osteogenic commitment increased, and the suppression of pro-inflammatory genes and the relative inflammatory response pathway were observed.…”

“…The effects of different tensile force magnitudes and durations have been investigated in some studies. Among the magnitudes, a magnitude of 10% generally led to a lower level of inflammation and a higher level of osteogenesis, 10 whereas a magnitude of 12% was found to correlate well with strain conditions at the mid-root under physiological loading conditions 11 , 12 and to induce optimal effects in both the proliferation and osteogenesis of PDLSCs. 13 Cyclic tension alone at 3000 μstrain significantly enhanced SATB Homeobox 2 (Satb2) after 3 h of loading and significantly upregulated Runx2 after 6 h. 14 The synthesis of BMP9 increased under 6-h continuously applied cyclic tension.…”

Cyclic Stretching Triggers Cell Orientation and Extracellular Matrix Remodeling in a Periodontal Ligament 3D In Vitro Model

“…Furthermore, our results support previous studies, emphasizing the importance of working below the mechanical force overload threshold (20% strain) to prevent hydrogel rupture. [3,[62][63][64][65] The same condition (10% strain, 1 h per day) sustained stretching as a determining factor for triggering cell proliferation and ECM remodeling. [3,66] Importantly, the numerical simulations of the stretching hydrogel under this optimal strain of 10% evidenced that the cells experienced stresses up to 280 Pa in magnitude.…”

“…[1] OTM is a remodeling process in which the application of a force induces bone resorption on the compression side and bone apposition on the tension side, that is, between the periodontal ligament (PDL) and alveolar bone. [2,3] PDL is a connective tissue that lies between the cementum covering the root of the tooth and alveolar bone. It firmly anchors the tooth to alveolar bone via Sharpey's fibers.…”

Analysis of ceRNA networks during mechanical tension‐induced osteogenic differentiation of periodontal ligament stem cells

“…The effects of different mechanical parameters, including magnitude and frequency, on the osteogenic differentiation of PDLSCs under tension have been studied. Among different magnitudes, a magnitude of 10% was investigated to lead to a lower level of inflammation and a higher level of osteogenesis [35], and a magnitude of 12% was considered to correlate well with strain conditions at the mid-root under physiological loading conditions [36] and induce optimal effects in both the proliferation and osteogenesis of PDLSCs [37]. In our previous study, we have compared the effects of different frequencies on the osteogenic differentiation of PDLSCs at the magnitude of 12% and found that 0.7 Hz most significantly promoted the osteogenesis of PDLSCs among different frequencies [38].…”