Shear stress preconditioning enhances periodontal ligament stem cell survival

OBJECTIVE

The study investigated in vitro the influences of shear stress preconditioning on human periodontal ligament stem cells (hPDLSCs) under serum deprivation.

DESIGN

hPDLSCs were subjected to shear stress at 0.5 and 5 dyn/cm², both with and without serum starvation. Cell viability and apoptosis were assessed using the Resazurin assay and flow cytometry analysis, respectively. Gene and protein expressions were analysed by real-time polymerase chain reaction, immunofluorescent staining, and Western blotting.

RESULTS

Our results revealed that shear stress potentially mitigated serum derivation-induced cell death by inducing cell viability, enhancing colony formation, and inhibiting cell apoptosis. The addition of an ERK inhibitor inhibited the shear stress-induced cell apoptosis resistance. Shear stress treatment upregulated cell viability-related gene expression, including SOX2, SOD1 and BIRC5. In particular, shear stress promoted the nuclear translocation of SOX2. Meanwhile, the expression of BIRC5 was not inhibited by cycloheximide. Shear stress-induced SOX2 and BIRC5 expression was attenuated by PI3K and ERK inhibitors, respectively.

CONCLUSIONS

Shear stress contributes to promoting SOX2 and BIRC5 expression by hPDLSCs, implicating the promotion of stemness and cell survival under serum starvation.

Novel therapeutic strategy for intractable keloids: suppression of intracellular mechanotransduction and actin polymerization via Rho-kinase pathway inhibition

BACKGROUND

Keloid is a dermal fibrotic disorder characterized by excessive extracellular matrix production by fibroblasts. Despite the significance of mechanostimulation in fibrotic diseases, its association with keloid pathophysiology or treatment remains unexplored.

OBJECTIVES

To investigate the role of mechanical force in keloid formation and elucidate the significance of Rho-associated coiled-coil-containing kinase 1 (ROCK1) as a mechanoresponsive target for keloid treatment.

METHODS

Patient-derived keloid fibroblasts (KFs) were subjected to cyclic stretching ranging from 0% to 20% elongation using a cell-stretching system. We observed the inhibitory effects of the ROCK1 inhibitor Y27632 on KFs and keloid formation. Validation was performed using a keloid xenograft severe combined immune-deficient (SCID) mouse model.

RESULTS

ROCK1 was overexpressed in KFs isolated from patients. Cyclic stretching induced fibroblast proliferation and actin polymerization by activating Rho/ROCK1 signalling. Treatment with Y27632 downregulated fibrotic markers reduced the migration capacity of KFs and induced extensive actin cytoskeleton remodelling. In the keloid xenograft SCID mouse model, Y27632 effectively suppressed keloid formation, mitigating inflammation and fibrosis.

CONCLUSIONS

The ROCK1 inhibitor Y27632 is a promising molecule for keloid treatment, exerting its effects through actin cytoskeleton remodelling and nuclear inhibition of fibrotic markers in keloid pathogenesis.

Altered actin dynamics is possibly implicated in the inhibition of mechanical stimulation-induced dermal fibroblast differentiation into myofibroblasts

The formation of hypertrophic scars and keloids is strongly associated with mechanical stimulation, and myofibroblasts are known to play a major role in abnormal scar formation. Wounds in patients with neurofibromatosis type 1 (NF1) become inconspicuous and lack the tendency to form abnormal scars. We hypothesized that there would be a unique response to mechanical stimulation and subsequent scar formation in NF1. To test this hypothesis, we investigated the molecular mechanisms of differentiation into myofibroblasts in NF1-derived fibroblasts and neurofibromin-depleted fibroblasts and examined actin dynamics, which is involved in fibroblast differentiation, with a focus on the pathway linking LIMK2/cofilin to actin dynamics. In normal fibroblasts, expression of α-smooth muscle actin (α-SMA), a marker of myofibroblasts, significantly increased after mechanical stimulation, whereas in NF1-derived and neurofibromin-depleted fibroblasts, α-SMA expression did not change. Phosphorylation of cofilin and subsequent actin polymerization did not increase in NF1-derived and neurofibromin-depleted fibroblasts after mechanical stimulation. Finally, in normal fibroblasts treated with Jasplakinolide, an actin stabilizer, α-SMA expression did not change after mechanical stimulation. Therefore, when neurofibromin was dysfunctional or depleted, subsequent actin polymerization did not occur in response to mechanical stimulation, which may have led to the unchanged expression of α-SMA. We believe this molecular pathway can be a potential therapeutic target for the treatment of abnormal scars.

Effects of Mechanical Stress Stimulation on Function and Expression Mechanism of Osteoblasts

Osteoclasts and osteoblasts play a major role in bone tissue homeostasis. The homeostasis and integrity of bone tissue are maintained by ensuring a balance between osteoclastic and osteogenic activities. The remodeling of bone tissue is a continuous ongoing process. Osteoclasts mainly play a role in bone resorption, whereas osteoblasts are mainly involved in bone remodeling processes, such as bone cell formation, mineralization, and secretion. These cell types balance and restrict each other to maintain bone tissue metabolism. Bone tissue is very sensitive to mechanical stress stimulation. Unloading and loading of mechanical stress are closely related to the differentiation and formation of osteoclasts and bone resorption function as well as the differentiation and formation of osteoblasts and bone formation function. Consequently, mechanical stress exerts an important influence on the bone microenvironment and bone metabolism. This review focuses on the effects of different forms of mechanical stress stimulation (including gravity, continuously compressive pressure, tensile strain, and fluid shear stress) on osteoclast and osteoblast function and expression mechanism. This article highlights the involvement of osteoclasts and osteoblasts in activating different mechanical transduction pathways and reports changings in their differentiation, formation, and functional mechanism induced by the application of different types of mechanical stress to bone tissue. This review could provide new ideas for further microscopic studies of bone health, disease, and tissue damage reconstruction.