Inhibitory Effect of Low-Intensity Pulsed Ultrasound on the Expression of Lipopolysaccharide-Induced Inflammatory Factors in U937 Cells

Recent Advances in Basic Studies of Low-Intensity Pulsed Ultrasound in Periodontal Tissue Regeneration: A Systematic Review

Approximately half of the adult population is suffering from periodontal disease, and conventional periodontal treatment strategies can only slow the progression of the disease. As a kind of tissue engineering, periodontal regeneration brings hope for the treatment of periodontal disease. Low-intensity pulsed ultrasound (LIPUS) is a form of ultrasound with a frequency of 1-3 MHz and a much lower intensity (< 1W/cm2) than traditional ultrasound energy and output. LIPUS has been adopted for a variety of therapeutic purposes due to its bioeffects such as thermal, mechanical, and cavitation effects, which induce intracellular biochemical effects and lead to tissue repair and regeneration ultimately. In this systematic review, we summarize the basic research of LIPUS in the treatment of periodontal disease in periodontal disease animal models and the influence of LIPUS on the biological behavior (including promoting osteogenic differentiation of stem cells and inhibiting inflammatory response) and potential mechanism of periodontal ligament stem cells (PDLSCs), hoping to provide new ideas for the treatment of periodontal disease. We believe that LIPUS can be used as an auxiliary strategy in the treatment of periodontal disease and play an exciting and positive role in periodontal regeneration.

Low-Intensity Pulsed Ultrasound: A Physical Stimulus with Immunomodulatory and Anti-inflammatory Potential

Ultrasound has expanded into the therapeutic field as a medical imaging and diagnostic technique. Low-intensity pulsed ultrasound (LIPUS) is a kind of therapeutic ultrasound that plays a vital role in promoting fracture healing, wound repair, immunomodulation, and reducing inflammation. Its anti-inflammatory effects are manifested by decreased pro-inflammatory cytokines and chemokines, accelerated regression of immune cell invasion, and accelerated damage repair. Although the anti-inflammatory mechanism of LIPUS is not very clear, many in vitro and in vivo studies have shown that LIPUS may play its anti-inflammatory role by activating signaling pathways such as integrin/Focal adhesion kinase (FAK)/Phosphatidylinositol 3-kinase (PI3K)/Serine threonine kinase (Akt), Vascular endothelial growth factor (VEGF)/endothelial nitric oxide synthase (eNOS), or inhibiting signaling pathways such as Toll-like receptors (TLRs)/Nuclear factor kappa-B (NF-κB) and p38-Mitogen-activated protein kinase (MAPK). As a non-invasive physical therapy, the anti-inflammatory and immunomodulatory effects of LIPUS deserve further exploration.

Optimal low-intensity pulsed ultrasound stimulation for promoting anti-inflammatory effects in macrophages

In this paper, we stimulated M1-like macrophages (obtained from U937 cells) with low-intensity pulsed ultrasound (LIPUS) to lower pro-inflammatory cytokine production. A systematic screening of different frequencies, intensities, duty cycles, and exposure times was performed. The optimal stimulation conditions leading to a marked decrease in the release of inflammatory cytokines were determined to be 38 kHz, 250 mW/cm², 20%, and 90 min, respectively. Using these parameters, we verified that up to 72 h LIPUS did not affect cell viability, resulting in an increase in metabolic activity and in a reduction of reactive oxygen species (ROS) production. Moreover, we found that two mechanosensitive ion channels (PIEZO1 and TRPV1) were involved in the LIPUS-mediated cytokine release modulation. We also assessed the role of the nuclear factor κB (NF-κB) signaling pathway and observed an enhancement of actin polymerization. Finally, transcriptomic data suggested that the bioeffects of LIPUS treatment occur through the modulation of p38 MAPK signaling pathway.

Inflammation Responses to Bone Scaffolds under Mechanical Stimuli in Bone Regeneration

Physical stimuli play an important role in one tissue engineering. Mechanical stimuli, such as ultrasound with cyclic loading, are widely used to promote bone osteogenesis; however, the inflammatory response under physical stimuli has not been well studied. In this paper, the signaling pathways related to inflammatory responses in bone tissue engineering are evaluated, and the application of physical stimulation to promote osteogenesis and its related mechanisms are reviewed in detail; in particular, how physical stimulation alleviates inflammatory responses during transplantation when employing a bone scaffolding strategy is discussed. It is concluded that physical stimulation (e.g., ultrasound and cyclic stress) helps to promote osteogenesis while reducing the inflammatory response. In addition, apart from 2D cell culture, more consideration should be given to the mechanical stimuli applied to 3D scaffolds and the effects of different force moduli while evaluating inflammatory responses. This will facilitate the application of physiotherapy in bone tissue engineering.

LIPUS as a potential strategy for periodontitis treatment: A review of the mechanisms

Periodontitis is a chronic inflammatory condition triggered by oral bacteria. A sustained inflammatory state in periodontitis could eventually destroy the alveolar bone. The key objective of periodontal therapy is to terminate the inflammatory process and reconstruct the periodontal tissues. The traditional Guided tissue regeneration (GTR) procedure has unstable results due to multiple factors such as the inflammatory environment, the immune response caused by the implant, and the operator's technique. Low-intensity pulsed ultrasound (LIPUS), as acoustic energy, transmits the mechanical signals to the target tissue to provide non-invasive physical stimulation. LIPUS has positive effects in promoting bone regeneration, soft-tissue regeneration, inflammation inhibition, and neuromodulation. LIPUS can maintain and regenerate alveolar bone during an inflammatory state by suppressing the expression of inflammatory factors. LIPUS also affects the cellular behavior of periodontal ligament cells (PDLCs), thereby protecting the regenerative potential of bone tissue in an inflammatory state. However, the underlying mechanisms of the LIPUS therapy are still yet to be summarized. The goal of this review is to outline the potential cellular and molecular mechanisms of periodontitis-related LIPUS therapy, as well as to explain how LIPUS manages to transmit mechanical stimulation into the signaling pathway to achieve inflammatory control and periodontal bone regeneration.

Biochemical and Physiological Events Involved in Responses to the Ultrasound Used in Physiotherapy: A Review

Therapeutic ultrasound (TUS) is the ultrasound modality widely used in physical therapy for the treatment of acute and chronic injuries of various biological tissues. Its thermal and mechanical effects modify the permeability of the plasma membrane, the flow of ions and molecules and cell signaling and, in this way, promote the cascade of physiological events that culminate in the repair of injuries. This article is a review of the biochemical and physiological effects of TUS with parameters commonly used by physical therapists. Integrins can translate the mechanical signal of the TUS into a cellular biochemical signal for protein synthesis and modification of the active site of enzymes, so cell function and metabolism are modified. TUS also alters the permeability of the plasma membrane, allowing the influx of ions and molecules that modulate the cellular electrochemical signaling pathways. With biochemical and electrochemical signals tampered with, the cellular response to damage is then modified or enhanced. Greater release of pro-inflammatory factors, cytokines and growth factors, increased blood flow and activation of protein kinases also seem to be involved in the therapeutic response of TUS. Although a vast number of publications describe the mechanisms by which TUS can interact with the biological system, little is known about the metabolic possibilities of TUS because of the lack of standardization in its application.

Low-intensity pulsed ultrasound promotes periodontal regeneration in a beagle model of furcation involvement

Objective: To evaluate the regeneration potential of periodontitis tissue treated by low-intensity pulsed ultrasound (LIPUS) combined with the guided tissue regeneration (GTR) technique in a beagle model of furcation involvement (FI).

Background: Achieving predictable regeneration remains a clinical challenge for periodontitis tissue due to the compromised regenerative potential caused by chronic inflammation stimulation. LIPUS, an FDA-approved therapy for long bone fracture and non-unions, has been demonstrated effective in the in vitro attenuation of inflammation-induced dysfunction of periodontal ligament stem cells (PDLSCs), the key cells contributing to periodontal regeneration. However, the in vivo effect of LIPUS on periodontitis tissue is rarely reported.

Methods: A beagle model of FI was established, and the experimental teeth were randomly assigned into three groups: control group, GTR group, and GTR+LIPUS group. Radiographic examinations were performed, and clinical periodontal parameters were recorded to reflect the periodontal condition of different groups. Histological analyses using H&amp;E and Masson’s staining were conducted to evaluate the periodontal tissue regeneration.

Results: LIPUS could enhance new periodontal bone formation and bone matrix maturity in FI after GTR treatment. Moreover, clinical assessment and histomorphometric analyses revealed less inflammatory infiltration and superior vascularization within bone grafts in the LIPUS treatment group, indicating the anti-inflammatory and pro-angiogenic effects of LIPUS in FI.

Conclusion: Our investigation on a large animal model demonstrated that LIPUS is a promising adjunctive approach for the regeneration of periodontitis tissue, paving a new avenue for LIPUS application in the field of periodontal regenerative medicine.

Pulsed-Ultrasound Irradiation Induces the Production of Itaconate and Attenuates Inflammatory Responses in Macrophages

Background

Itaconate is a key metabolite in the innate immune system and exerts strong anti-inflammatory effects in macrophages. For the production of itaconate in macrophages, immune-responsive gene 1 (IRG1) is an imperative enzyme, and activating the IRG1-itaconate pathway is reported to alleviate inflammatory diseases by upregulating nuclear factor-erythroid 2-related factor 2 (NRF2). However, there are very few reports on strategies to increase itaconate production. Ultrasound therapy is a widely used intervention for anti-inflammatory and soft-tissue regeneration purposes. Here we show the effect of ultrasound irradiation on the production of itaconate in macrophages.

Methods

Murine bone marrow-derived macrophages (BMDMs) were exposed to pulsed ultrasound (3.0 W/cm²) for 5 minutes. Three hours after irradiation, the intracellular levels of metabolites and mRNA expression levels of Irg1 and Nrf2 were measured using CE/MS and qPCR, respectively. To evaluate macrophage inflammation status, 3 h after irradiation, the cells were stimulated with 100 ng/mL lipopolysaccharide (LPS) for 1.5 h and the mRNA expression levels of pro-inflammatory factors (Il-1β, Il-6, and Tnf-α) were measured. Student’s t-test, one-way ANOVA and Tukey’s multiple comparison test were used for statistical processing, and the significance level was set to less than 5%.

Results

Ultrasound irradiation significantly increased the intracellular itaconate level and the expression levels of Irg1 and Nrf2 in BMDMs. Upregulation of Il-1β, Il-6, and Tnf-α by LPS was significantly suppressed in BMDMs treated with ultrasound. Ultrasound irradiation did not affect cell viability and apoptosis.

Conclusion

Ultrasound irradiation induces the production of itaconate by upregulating Irg1 expression and attenuates inflammatory responses in macrophages via Nrf2. These results suggest that ultrasound is a potentially useful method to increase itaconate production in macrophages.

Low-intensity pulsed ultrasound enhances bone marrow-derived stem cells-based periodontal regenerative therapies

BACKGROUND

Alveolar bone loss is one of the most common consequence for periodontitis, which is a major obstacle in periodontal regeneration. Bone marrow stromal cells (BMSCs) have shown significant promise in the treatment of various disease, which also contribute to the natural bone repair process. Low-intensity pulsed ultrasound (LIPUS) is a therapeutic ultrasound used in our previous studies to promotes alveolar bone regeneration. In addition, LIPUS was found to be a promising method to enhance mesenchymal stromal cell-based therapies. In the current study, we have investigated the effects of LIPUS combined with BMSCs therapies on BMSCs homing and its potential to promote alveolar bone regeneration.

METHODS

BMSCs were isolated from rat and characterized by multilineages differentiation assay. Then these cells were labeled with luciferase and green fluorescent protein (GFP) by lentivirus in vitro. Periodontal bone defect was made on the mesial area of the maxillary first molar in rats. A total of 1 × 10⁶ Luc-GFP labeled BMSCs were injected into rat tail vein. Bioluminescence imaging was utilized to track BMSCs in vivo. The rats were sacrificed eight weeks after surgery and the samples were harvested. Micro-computed tomography (Micro-CT) was performed to evaluate alveolar bone regeneration. Paraffin sections were made and subject to hematoxylin-eosin staining, masson staining and immunohistochemistry staining.

RESULTS

BMSCs display a fibroblast-like morphology and can differentiate into adipocytes or osteoblasts under appropriate condition. The transfected BMSCs are strongly positive for GFP express. Bioluminescence imaging showed that most of BMSCs were trapped in the lung. A small portion BMSCs were homed to the alveolar bone defect area in BMSCs group, while more cells were observed in BMSCs/LIPUS group compare to other groups on day 3 and 7. Micro-CT results showed that BMSCs/LIPUS group resulted in more new bone formation than other groups. Immunohistochemical results showed higher expression of COL-I and osteopontin in BMSCs/LIPUS group compared with the other groups.

CONCLUSIONS

These results suggested that LIPUS can enhance BMSCs-based periodontal alveolar bone regeneration. This study provides new insights into how LIPUS might provide therapeutic benefits by promoting BMSCs homing.

Low-Intensity Pulsed Ultrasound Promotes Repair of 4-Vinylcyclohexene Diepoxide-Induced Premature Ovarian Insufficiency in SD Rats

Women with premature ovarian insufficiency (POI) may be more vulnerable to a variety of health risks. To seek a new method to treat the disease, the effects of low-intensity pulsed ultrasound (LIPUS) on promoting repair of ovarian injury in female SD rats induced by 4-vinylcyclohexene diepoxide (VCD) were explored in this research. A total of 24 female SD rats were subjected to intraperitoneal injection of VCD to induce POI. Successful modeling was achieved in 22 rats, which were then randomized into VCD + LIPUS group (n = 13) and VCD group (n = 9). The control group (n = 5) was injected with equal normal saline. Hematoxylin and eosin staining, enzyme-linked immunosorbent assay, Western blot analysis, scanning electron microscope, immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated nick end labeling assay were applied to detect the results. The results indicated that rats in the VCD group showed disorder in the estrous cycle, the number of atresia follicles and apoptosis granulosa cells increased (p < .05). After the LIPUS treatment, the estrous cycle recovered, the number of follicles increased (p < .05), the level of E2 and anti-Müllerian hormone enhanced (p < .05), and the follicle-stimulating hormone decreased (p < .05). The expression of NF-κB p65, TNFα, Bax, ATF4, and caspase-3 in ovarian tissue was significantly decreased (p < .05). These findings showed that LIPUS could promote the repair of the VCD-induced ovarian damage in SD rats, which has the potential to be further applied in the clinic.

LIPUS inhibits inflammation and catabolism through the NF-κB pathway in human degenerative nucleus pulposus cells

Background

Low-intensity pulsed ultrasound (LIPUS) is a safe and noninvasive rehabilitative physical therapy with anti-inflammatory effects. The current study investigated the effect of LIPUS on the inflammation of nucleus pulposus (NP) cells and its underlying mechanism.

Methods

Human NP cells were acquired from lumbar disc herniation tissue samples and cultured for experiments. Human NP cells were treated with LPS and then exposed to LIPUS (15 mW/cm², 30 mW/cm² and 60 mW/cm²) for 20 min daily for 3 days to determine the appropriate intensity to inhibit the expression of the inflammatory factors TNF-α and IL-1β. The gene and protein expression of aggrecan, collagen II, MMP-3 and MMP-9 was measured by real‐time PCR and western blotting, respectively. The activity of the nuclear factor‐kappa B (NF‐κB) pathway was examined by western blotting and immunofluorescence. After pretreatment with the NF-κB inhibitor PDTC, the expression of TNF-α, IL-1β, MMP-3 and MMP-9 was measured by real‐time PCR.

Results

LIPUS at intensities of 15 mW/cm², 30 mW/cm² and 60 mW/cm² inhibited LPS-induced NP cell expression of the inflammatory factors TNF-α and IL-1β, especially at 30 mW/cm². LIPUS significantly upregulated the gene and protein expression of aggrecan and collagen II and downregulated the gene and protein expression of MMP-3 and MMP-9 in LPS-induced NP cells. The NF‐κB signaling pathway was inhibited by LIPUS through inhibiting the protein expression of p-P65 and the translocation of P65 into the nucleus in LPS-induced NP cells. In addition, LIPUS had similar effects as the NF-κB inhibitor PDTC by inhibiting the NF-κB signaling pathway, inflammation and catabolism in LPS-induced human degenerative nucleus pulposus cells.

Conclusion

LIPUS inhibited inflammation and catabolism through the NF‐κB pathway in human degenerative nucleus pulposus cells.

Effects of Low-Intensity Transcranial Pulsed Ultrasound Treatment in a Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease. One of the main pathology markers of AD is the beta-amyloid plaques (βA_1-42) created from residues of the badly processed amyloid precursor protein. The accumulation of these plaques can induce neuroinflammation and oxidative stress and impair antioxidant mechanisms, culminating in cognitive and memory deficits. New therapies are necessary to treat AD as the approved drugs do not treat the progress of the disease. Transcranial low-intensity pulsed ultrasound (LIPUS) affects brain metabolism and could be tested as a treatment for AD. This study was aimed at evaluating the LIPUS treatment in a model of AD induced by βA_1-42 intracerebroventricularly (ICV) and its effects on learning memory, neurotrophins, neuroinflammation and oxidative status. βA_1-42 was administered ICV 24 h before the start of a 5-wk LIPUS treatment. The treatment with LIPUS improved recognition memory, as well as increasing nerve growth factor β and brain-derived neurotrophic factor levels in the hippocampus and cortex. There was a decrease in protein damage in the hippocampus treated with LIPUS. Neuroinflammation and oxidative stress were not present in the AD model used. The results indicated that LIPUS is a novel and promising adjuvant strategy for treatment of the late stage of AD.

Development and validation of low-intensity pulsed ultrasound systems for highly controlled in vitro cell stimulation

This work aims to describe the development and validation of two low-intensity pulsed ultrasound stimulation systems able to control the dose delivered to the biological target. Transducer characterization was performed in terms of pressure field shape and intensity, for a high-frequency range (500 kHz to 5 MHz) and for a low-frequency value (38 kHz). This allowed defining the distance, on the beam axis, at which biological samples should be placed during stimulation and to exactly know the intensity at the target. Carefully designed retaining systems were developed, for hosting biological samples. Sealing tests proved their impermeability to external contaminants. The assembly/de-assembly time of the systems resulted ~3 min. Time-domain acoustic simulations allowed to precisely estimate the ultrasound beam within the biological sample chamber, thus enabling the possibility to precisely control the pressure to be transmitted to the biological target, by modulating the transducer's input voltage. Biological in vitro tests were also carried out, demonstrating the sterility of the system and the absence of toxic and inflammatory effects on growing cells after multiple immersions in water, over seven days.

Effects of pulsed ultrasound on olfactory dysfunction in patients with chronic rhinosinusitis: A pilot study

BACKGROUND

and purpose. Olfactory dysfunction is a common symptom of chronic rhinosinusitis (CRS). This study aimed to evaluate the effects of therapeutic pulsed ultrasound (PUS) on olfactory dysfunction in patients with CRS.

MATERIALS AND METHODS

Patients with CRS underwent treatment with PUS for 10 sessions, three days a week. The outcome measures were the Smell Identification Test (SIT) and 20-item Sino-Nasal Outcome Test (SNOT-20).

RESULTS

Fifteen patients (9 male, mean age 48.9 ± 9.7 years) with disease duration of 55.13 ± 65.4 months participated. Analyses showed olfactory dysfunction was completely resolved (Cohen's d = 5.62). The SNOT-20 scores showed significant improvement of CRS symptoms after treatment (Cohen's d = 1.55). Effects remained at one-month follow-up.

CONCLUSION

Therapeutic PUS improved the olfactory dysfunction and sino-nasal symptoms in patients with CRS. The PUS can be considered as a promising strategy to target chronic rhinosinusitis.

Low-intensity pulsed ultrasound inhibits IL-6 in subchondral bone of temporomandibular joint osteoarthritis by suppressing the TGF-β1/Smad3 pathway

OBJECTIVE

This study aimed to provide further information on the exact mechanisms involved in the anti-inflammatory effect of low-intensity pulsed ultrasound (LIPUS) on rabbit temporomandibular joint osteoarthritis (TMJOA) on interleukin-6 (IL-6) production in subchondral bone, IL-6 production in IL-1β stimulated via inhibition of the TGF-β1/Smad3 pathway in mouse embryo osteoblast precursor (MC3T3-E1) cells.

DESIGN

Bilateral joints were injected with type II collagenase to establish TMJOA models in two male and four female rabbits. The left joint was continuously stimulated by LIPUS, while the right joint was treated with the power off in this model. One male and two female rabbits were used as normal healthy controls without treatment. The histological features of subchondral bone were examined by Safranin-O/Fast staining. Immunohistochemistry was conducted to evaluate IL-6 expression. Then, cells were stimulated by LIPUS with IL-1β. IL-6 expression and activity of the TGF-β1/Smad3 pathway were evaluated by Enzyme-linked immunosorbent assay (ELISA), Immunofluorescence and Western blotting, respectively. Specific inhibition of the TGF-β1/Smad3 pathway was conducted by transfecting with small interfering RNA (siRNA) of type II receptor (siTβRII).

RESULTS

LIPUS significantly ameliorated the production of IL-6 in vitro and in vivo. Its inhibitory effect on the production of IL-6 induced by IL-1β in MC3T3-E1 cells was partly reversed by siTβRII knockdown.

CONCLUSIONS

LIPUS inhibited IL-6 production by suppressing the TGF-β1/Smad3 pathway of subchondral bone in TMJOA. These data revealed the part of the pathways involved in the anti-inflammatory effect of LIPUS and provided a possible treatment strategy for TMJOA patients and other inflammatory diseases.

Review on experimental study and clinical application of low-intensity pulsed ultrasound in inflammation

Low-intensity pulsed ultrasound (LIPUS), as physical therapy, is widely used in both research and clinical settings. It induces multiple bioeffects, such as alleviating pain, promoting tissue repair, and shortening disease duration. LIPUS can also mediate inflammation. This paper reviews the application of LIPUS in inflammation and discusses the underlying mechanism. In basic experiments, LIPUS can regulate inflammatory responses at the cellular level by affecting some signaling pathways. In a clinical trial, LIPUS has been shown to alleviate inflammatory responses efficiently. As a cheap, safe, and convenient physical method, LIPUS is promising as anti-inflammatory therapy.

Low-intensity pulsed ultrasound promotes the formation of periodontal ligament stem cell sheets and ectopic periodontal tissue regeneration

Human periodontal ligament stem cells (hPDLSCs) sheets play an important role in periodontal tissue engineering. Low-intensity pulsed ultrasound (LIPUS) has been reported as an effective stimulus to regulate cell biological behavior. The present study aims to explore the potential of LIPUS to promote the formation and function of hPDLSC sheets (hPDLSCSs). Hematoxylin-eosin (H&E) staining, western blot, real-time PCR, alkaline phosphatase (ALP), and alizarin red staining were used to evaluate the formation and osteogenic effect of LIPUS on hPDLSCSs in vitro. Hydroxyapatite with or without hPDLSCSs was transplanted in the subcutaneous pockets on the back of nude mice and histological analysis was performed. H&E staining showed increased synthesis of extracellular matrix (ECM) and real-time PCR detected a significant increase in ECM-related genes after LIPUS treatment. In addition, LIPUS could promote the expression of osteogenic differentiation-related genes and proteins. ALP and alizarin red staining also found LIPUS enhanced the osteogenesis of hPDLSCSs. After transplantation in vivo, more dense collagen fibers similar to periodontal ligament were regenerated. Collectively, these results indicate that LIPUS not only promotes the formation and osteogenic differentiation of hPDLSCSs but also is a potential treatment strategy for periodontal tissue engineering.

Low-intensity pulsed ultrasound upregulates osteogenesis under inflammatory conditions in periodontal ligament stem cells through unfolded protein response

Background

In periodontal tissue engineering, periodontal ligament stem cells derived from patients with periodontitis (P-PDLSCs) are among the most promising and accessible stem cells for repairing disrupted alveolar bone and other connective tissues around the teeth. However, the inflammatory environment influences the osteogenic differentiation ability of P-PDLSCs. We examined low-intensity pulsed ultrasound (LIPUS) in P-PDLSCs in vitro and in rats with experimental periodontitis to determine whether LIPUS can enhance the osteogenic differentiation of stem cells.

Materials and methods

P-PDLSCs were harvested and isolated from the periodontal tissues around the teeth of periodontitis patients, and healthy PDLSCs (H-PDLSCs) were obtained from tissues around healthy teeth. After validation by flow cytometry analysis, the P-PDLSCs were cultured in osteogenic medium either pretreated with the endoplasmic reticulum stress (ERS) inhibitor 4-phenyl butyric acid (4-PBA) or not pretreated and then treated with or without LIPUS (90 mW/cm², 1.5 MHz) for 30 min per day. Cell viability, ERS marker expression, and osteogenic potential were determined between the different treatment groups. LPS-induced H-PDLSCs were used to mimic the inflammatory environment. In addition, we established a model of experimental periodontitis in rats and used LIPUS and 4-PBA as treatment methods. Then, the maxillary bone was collected, and micro-CT and histology staining methods were used to detect the absorption of alveolar bone.

Results

Our data showed that the P-PDLSCs derived from periodontitis tissues were in a more pronounced ERS state than were the H-PDLSCs, which resulted in the former being associated with increased inflammation and decreased osteogenic ability. LIPUS can alleviate ERS and inflammation while increasing the bone formation capacity of P-PDLSCs in vivo and in vitro.

Conclusions

LIPUS may be an effective method to enhance the outcome of periodontal tissue engineering treatments of periodontitis by suppressing inflammation and increasing the osteogenic differentiation of P-PDLSCs through the unfolded protein response pathway, and more detailed studies are needed in the future.

SQSTM1-dependent autophagic degradation of PKM2 inhibits the production of mature IL1B/IL-1β and contributes to LIPUS-mediated anti-inflammatory effect

Synovitis is implicated in the pathology of osteoarthritis (OA) and significantly contributes to the development of OA. As a noninvasive physical therapy, low-intensity pulsed ultrasound (LIPUS) has been reported to possess anti-inflammatory effect in recent years. However, the role of LIPUS on synovitis of OA and the underlying mechanisms are little known. The present study showed that LIPUS ameliorated synovial inflammation in destabilization of the medial meniscus (DMM) mouse model and air pouch model, and alleviated pain gait patterns of DMM mouse. LIPUS dramatically inhibited the production of mature IL1B/IL-1β (interleukin 1 beta) in vitro and in vivo. In addition, LIPUS upregulated the macroautophagy/autophagy level as well as accelerated the formation of an SQSTM1 (sequestosome1)-PKM (pyruvate kinase, muscle) complex in the lipopolysaccharide (LPS)-adenosine triphosphate (ATP)-treated macrophages. Besides, LIPUS downregulated the level of PKM2 in LPS-ATP-treated macrophages, which could be reversed by SQSTM1 knockdown. In brief, the present study for the first time demonstrates that LIPUS inhibits the production of mature IL1B partially via SQSTM1-dependent autophagic degradation of PKM2 in LPS-ATP-treated macrophages, which may further ameliorate the synovial inflammation and gait patterns in animal models. Our data provide new clues for the treatments of synovitis and other inflammatory diseases using LIPUS.

ABBREVIATIONS

3-MA: 3-methyladenene; ATG7: autophagy-related 7; ATP: adenosine triphosphate; BafA1: bafilomycin A₁; BMDMs: bone marrow derived macrophages; CHX: cycloheximide; DMM: destabilization of the medial meniscus; ELISA: enzyme-linked immunosorbent assay; GFP: green fluorescent protein; IL1B/IL-1β: interleukin 1 beta; LIPUS: low-intensity pulsed ultrasound; LIR: LC3-interacting region; LPS: lipopolysaccharide; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MDP: muramyl dipeptide; NFKB/NF-κB: nuclear factor kappa B; NLRP3: NLR family, pyrin domain containing 3; OA: osteoarthritis; PKM/PKM2: pyruvate kinase M1/2; PMA: phorbol-12-myristate-13-acetate; PYCARD/ASC; PYD and CARD domain containing; RFP: red fluorescent protein; siRNAs: small interfering RNAs; SQSTM1: sequestosome 1; TEM: transmission electron microscopy.

LIPUS inhibited the expression of inflammatory factors and promoted the osteogenic differentiation capacity of hPDLCs by inhibiting the NF-κB signaling pathway

BACKGROUND AND OBJECTIVES

As a chronic infectious disease, periodontitis could lead to tooth and bone loss. Low-intensity pulsed ultrasound (LIPUS) is a safe, noninvasive treatment method to effectively inhibit inflammation and promote bone differentiation. However, the application of LIPUS in curing periodontitis is still rare. Our study aimed to explore the ability of LIPUS to inhibit inflammatory factors and promote the osteogenic differentiation capacity of human periodontal ligament cells (hPDLCs), and its underlying mechanism.

MATERIAL AND METHODS

Human periodontal ligament cells were obtained and cultured from the premolar tissue samples for experiments. First, hPDLCs were treated for 24 hours using lipopolysaccharide (LPS) and then exposed to LIPUS (10 mW/cm² , 30 mW/cm² , 60 mW/cm² , and 90 mW/cm² ) to determine the appropriate intensity to inhibit expression of the inflammatory factors interleukin-6 (IL-6) and interleukin-8 (IL-8) expression. The expression of IL-6 and IL-8 was detected by real-time PCR and enzyme-linked immunosorbent assay. The safety of the most appropriate intensity of LIPUS was tested by a cell counting kit 8 test and an apoptosis assay. Then, LPS-induced hPDLCs were treated in osteogenic medium for 7-21 days with or without LIPUS (90 mW/cm² , 30 min/d) stimulation. The osteogenic genes RUNX2, OPN, OSX, and OCN were measured by real-time PCR. Additionally, osteogenic differentiation capacity was determined using alkaline phosphatase (ALP) staining, ALP activity analysis, and Alizarin red staining. The activity of the nuclear factor-kappa B (NF-κB) signaling pathway was determined by western blotting, real-time PCR, immunofluorescence, and pathway blockade assays.

RESULTS

Lipopolysaccharide significantly upregulated the production and gene expression of IL-6 and IL-8, while LIPUS stimulation significantly inhibited IL-6 and IL-8 expression in an intensity-dependent manner. LIPUS (90 mW/cm² ) was chosen as the most appropriate intensity, and there was no detrimental influence on cell proliferation and status with or without osteogenic medium. In addition, consecutive stimulation with LIPUS (90 mW/cm² ) for 30 min/d for 7 days could also inhibit IL-6 and IL-8 gene expression, upregulate the expression of the osteogenesis-related genes RUNX2, OPN, OSX, and OCN, and promote osteogenic differentiation capacity in osteogenic medium in inflamed hPDLCs. The NF-κB signaling pathway was inhibited with LIPUS (90 mW/cm² ) via inhibition of the phosphorylation of IκBα and the translocation of p65 into the nucleus in inflamed hPDLCs. Additional investigations of the NF-κB inhibitor, BAY 11-7082, revealed that LIPUS (90 mW/cm² ) acted similarly to BAY 11-7802 to inhibit the NF-κB signaling pathway and increase osteogenesis-related genes and promote the osteogenic differentiation capacity of inflamed hPDLCs.

CONCLUSION

Low-intensity pulsed ultrasound (90 mW/cm² ) stimulation could be a safe method to inhibit IL-6 and IL-8 in hPDLCs by inhibiting the NF-κB signaling pathway. The effect of LIPUS (90 mW/cm² ) and BAY 11-7082 on LPS-induced inflammation demonstrated that both of these agents were capable of promoting osteogenesis-related gene expression and osteogenic differentiation in hPDLCs, suggesting that the effect of LIPUS on the promotion of osteogenic activity could be mediated in part through its ability to inhibit the NF-κB signal pathway. Hence, LIPUS could be a potential therapeutic method to cure periodontitis.

Low‑intensity pulsed ultrasound promotes periodontal ligament stem cell migration through TWIST1‑mediated SDF‑1 expression

Low‑intensity pulsed ultrasound (LIPUS) is a non‑invasive therapeutic treatment for accelerating fracture healing. A previous study from our group demonstrated that LIPUS has the potential to promote periodontal tissue regeneration. However, the underlying molecular mechanism by which LIPUS promotes periodontal tissue regeneration remains unknown. In the present study, periodontal ligament stem cells (PDLSCs) were isolated from premolars. Flow cytometry and differentiation assays were used to characterize the isolated PDLSCs. LIPUS treatment was administered to PDLSCs, and stromal cell‑derived factor‑1 (SDF‑1) expression levels were examined by reverse transcription‑quantitative polymerase chain reaction with or without blocking the SDF‑1/C‑X‑C motif chemokine receptor 4 (CXCR4) pathway with AMD3100. ELISA was used to evaluate SDF‑1 secretion in PDLSCs. Wound healing and transwell assays were conducted to assess the migration‑promoting effect of LIPUS. A potential upstream gene of SDF‑1, twist family bHLH transcription factor 1 (TWIST1), was silenced by small interfering (si) RNA transfection. The results demonstrated that LIPUS treatment promoted the expression of TWIST1 and SDF‑1 at both the mRNA and protein levels. In addition, LIPUS treatment enhanced the cell migration of PDLSCs. Knockdown of TWIST1 impaired the expression of SDF‑1 and the cell migration ability of PDLSCs. TWIST1 may be an upstream regulator of SDF‑1 in PDLSCs. Taken together, these findings indicate that the SDF1/CXCR4 signaling pathway is involved in LIPUS‑promoted PDLSC migration, which might be one of the mechanisms for LIPUS‑mediated periodontal regeneration. TWIST1 might be a mechanical stress sensor during mechanotransduction.