Uniaxial cyclic stretch enhances osteogenic differentiation of OPLL-derived primary cells via YAP-Wnt/β-catenin axis

Abstract

The pathogenesis of posterior longitudinal ligament ossification (OPLL) remains inadequately understood. Mechanical stimulation is one of the important pathogenic factors in OPLL. As one of the mechanical stimulation transduction signals, the yes-associated protein (YAP) interacts with the Wnt/β-catenin signalling pathway, which plays an important role in osteogenic differentiation. This study aimed to demonstrate the role of YAP-Wnt/β-catenin axis in cell differentiation induced by mechanical stress. Primary cells extracted from posterior longitudinal ligament tissues from OPLL or non-OPLL patients were subjected to sinusoidal uniaxial cyclic stretch (5 %, 0.5 Hz, 3 d). The expression of runt-related transcription factor 2, collagen I, osterix, osteocalcin and alkaline phosphatase were compared between the static and the experimental groups. In addition, the cytoskeleton was detected using phalloidin staining while YAP phosphorylation states and nuclear location were identified using immunofluorescence. The results showed that mechanical stretching loading increased the expression of osteogenic genes and proteins in the OPLL group, while it had no significant effect on the control group. When OPLL cells were stretched, YAP exhibited an obvious nuclear translocation and the Wnt/β-catenin pathway was activated. Knocking down YAP or β-catenin could weaken the impact upon osteogenic differentiation induced by mechanical stimulation. YAP-mediated mechanical stimulation promoted osteogenic differentiation of OPLL cells through Wnt/β-catenin pathway and this progress was independent of the Hippo pathway.

Effect of mechanical stimulation on tissue heterotopic ossification: an in vivo experimental study

“…The PLL located in the intervertebral space is subjected to tensile stress due to the spine’s flexion and extension, while the PLL close to the vertebral body is subjected to less tensile stress due to its close connection to the vertebral body. Furthermore, immunofluorescence staining indicated a significant increase in YAP expression at the site of ligamentous heterotopic ossification, which is consistent with previous in vitro studies ( Zhu et al, 2023 ). This finding suggests that mechanical stimulation plays a vital role in the pathological process.…”

“…They allow researchers to study the pathophysiological mechanisms of diseases and potential treatments more accurately. Previous research has shown that mechanical stimulation has a significant impact on cell osteoblastic differentiation at the cellular level, and this process is associated with the nuclear translocation of the mechanical signal response factor YAP ( Zhu et al, 2023 ). In this study, we aimed to establish an appropriate animal model that can serve as a basis for further in vivo investigation of this mechanism.…”

“…Our previous study demonstrated the significance of yes-associated protein (YAP), a transcriptional coactivator that plays a crucial role in promoting osteogenic differentiation of cells under tensile stress ( Zhu et al, 2023 ). However, its in vivo relevance has yet to be validated.…”

The roles of Hippo/YAP signaling pathway in physical therapy

“…For example, under dynamic culture conditions, primary cells from patients with heterotopic ossification showed significantly raised expression of osteogenic marker genes compared to static culture, indicating that mechanical stimulation may promote osteogenic differentiation of ligaments [58]. Zhu et al found that mechanical stimulation had a significant effect on osteoblast differentiation at cellular level, which was related to the nuclear translocation of the mechanical signaling response factor YAP [59]. On this basis, they used CRISPR/Cas9 technology to establish EIIa cre -Enpp1 flox/flox genedeficient mice and demonstrated that mechanical stimulation played a key role in the pathological process of heterotopic ossification of tendons and ligaments.…”