Low-Intensity Pulsed Ultrasound Alleviates Hypoxia-Induced Chondrocyte Damage in Temporomandibular Disorders by Modulating the Hypoxia-Inducible Factor Pathway

Abstract

Temporomandibular disorders are a common cause of chronic pain in the orofacial region and have a complex and multi-factorial pathophysiology. Mechanical loading or inflammatory conditions have been shown to decrease oxygen tension within the joint cartilage and activate the hypoxia-inducible factor (HIF) pathway, which in turn aggravates the pathological processes underlying temporomandibular joint (TMJ) disorders. We previously showed that low-intensity pulsed ultrasound (LIPUS) treatment effectively repairs TMJ injury induced by chronic sleep deprivation (CSD). Here, we explored the effects of LIPUS treatment on hypoxia-induced chondrocyte injury. We found that it effectively restored the proliferation capacity of mandibular chondrocytes under hypoxic conditions and lowered their rate of apoptosis. Chondrogenic capacity, as assessed by type II collagen levels, and mucin-positive areas were also significantly increased after LIPUS treatment. Levels of matrix metalloprotein-3 and interleukin-6 decreased in mandibular chondrocytes following this treatment, whereas the expression of tissue inhibitor of metalloproteinase-1 increased. We also found that HIF-1a expression was upregulated in mandibular chondrocytes under hypoxic conditions and was further enhanced by LIPUS treatment. Similarly, HIF-2a levels increased in mandibular chondrocytes under hypoxic conditions but decreased following LIPUS treatment. Subsequently, we established a CSD-induced TMJ injury model and found that LIPUS increased mucin-positive areas as well as HIF-1a expression and decreased HIF-2 level in the chondrocyte layer. Together, our results indicate that the protective effect of LIPUS on chondrocyte is partly associated with the HIF pathway.

The Attenuating Effect of Low-Intensity Pulsed Ultrasound on Hypoxia-Induced Rat Chondrocyte Damage in TMJ Osteoarthritis Based on TMT Labeling Quantitative Proteomic Analysis

“…Primary temporomandibular condylar chondrocytes were isolated from 3-week-old healthy male Wistar rats (SPF Biotechnology, Beijing, China). The steps for the isolation and culture of these cells were based on a procedure previously published by our group ( Yang et al, 2020 ). Third-generation chondrocytes were incubated in six-well plates (Corning, United States) in the following three groups: normal group (N group), cultured in an atmosphere containing 5% oxygen; low oxygen tension group (L group), cultured in an atmosphere containing less than 1% oxygen; and low oxygen tension + LIPUS treatment group (LP group), incubated in an atmosphere containing less than 1% oxygen and subjected to LIPUS stimulation.…”

“…With an intensity of 45 mW/cm 2 , the optimal effect is achieved after at least 2 weeks of treatment ( Liang et al, 2020 ). Moreover, in vitro simulation of a hypoxic environment has revealed that LIPUS can slow cartilage damage by upregulating HIF-1α and downregulating the HIF-2α pathway ( Yang et al, 2020 ). Current studies of cartilage, synovial fluid, serum and urine associated with joint disease utilizing proteomics aim to understand the pathogenesis and progression of arthritis ( Hsueh et al, 2014 ).…”

The therapeutic effects of low-intensity pulsed ultrasound in musculoskeletal soft tissue injuries: Focusing on the molecular mechanism

“…Moreover, He et al proved that LIPUS protected TMJDs through upregulating ZNT-9 (Zn2+ exporters), which further downregulated the crucial ECM-degrading effector enzymes MMP-3, ADAMTS-5, and ADAMTS-8 (He et al, 2021). According to Yang et al, LIPUS therapy restored the functions of damaged mandibular chondrocytes both in vitro and in vivo through modulating the hypoxia-inducible factor (HIF) pathway (Yang et al, 2020).…”

Effectiveness and Mechanisms of Low-Intensity Pulsed Ultrasound on Osseointegration of Dental Implants and Biological Functions of Bone Marrow Mesenchymal Stem Cells

“…A systemic review and meta-analysis even defined LIPUS as the most effective method for treating bone nonunion besides surgery [19]. In addition, several studies explored the therapeutic effects of LIPUS on cartilage tissue injury of the temporomandibular joint (TMJ) in the last 5 years and found that LIPUS could effectively suppress temporomandibular joint disorders (TMDs) in rats, which was caused by chronic sleep deprivation (CSD) intervention [20][21][22]. A recent review article also confirmed the effect of LIPUS on osteoarthritis of the TMJ [23].…”