Low-intensity pulsed ultrasound (LIPUS) stimulates mineralization of MC3T3-E1 cells through calcium and phosphate uptake

Co-stimulation with piezoelectric PVDF films and low intensity pulsed ultrasound enhances osteogenic differentiation

Bone tissue engineering has emerged as a promising approach to address the challenges of bone fracture repair and regeneration. The application of external stimuli (mechanical and electrical) can drive specific cellular responses and osteogenic differentiation, leading to the development of more effective treatments. Piezoelectric materials modulate cellular proliferation and osteogenic differentiation under both static (without mechanical stimulation) and dynamic (with mechanical stimulation) conditions, activating distinct gene expression pathways. In this work, we investigate the combinatorial effect of poly (vinylidene fluoride) (PVDF) poled and non-poled films, and low-intensity pulsed ultrasound (LIPUS) on early-stage osteogenic differentiation of mouse pre-osteoblasts. Static culture with PVDF poled films enhanced Runx2 and Col1α1 expression without impacting alkaline phosphatase (ALP) activity. Inhibition of ERK phosphorylation using U0126 in PVDF poled films resulted in a ~ 6-8-fold increase in ALP activity, suggesting the involvement of an alternative pathway in osteogenic differentiation. Dynamic culture with LIPUS generated an electric potential of approximately 500 mV across PVDF films and an electrical field of 0-10 mV mm-1. Co-stimulation led to a ~3-fold increase of ALP activity on stimulated PVDF compared to unstimulated films. This study underscores the potential of piezoelectric materials as non-invasive electrical stimulators to enhance the efficacy of ultrasound-based therapies for bone fracture repair.

Yellow light and ultrasound Dual-responsive strontium-doped zinc oxide composites for dental caries prevention and remineralization

Dental caries is one of the most prevalent chronic infectious diseases, mainly due to acid production by bacteria in the plaque biofilm, leading to enamel demineralization, tooth defects and pulpitis. Most of the current treatments are invasive and do not combine restoration of dental tissues, resolution of tooth staining or prevention of dental caries. In this study, a polydopamine (PDA)-encapsulated strontium-doped zinc oxide composite (Sr-ZnO@PDA, denoted as SZ@PDA) has been developed for caries prevention and remineralization. The PDA wrapping endows SZ@PDA with a narrow energy band gap (1.78 eV), which can simultaneously respond to yellow light (YL) with favorable biosafety and ultrasound (US) with high tissue penetration. The synergistic piezo-photocatalytic action of YL and US with the enhanced catalytic efficiency can generate an appropriate amount of reactive oxygen species (ROS), thus destroying the structure of bacterial cellular membranes and decomposing pigments for caries prevention and improvement of tooth staining, respectively. In addition, strontium ions (Sr2+) released by SZ@PDA, as an active element, can promote the remineralization of enamel and dentin, repairing defective dental tissues. Collectively, this versatile system (SZ@PDA) provides an effective strategy for the prevention and treatment of caries.

Possible Association of Nrf2/ARE and NFκB Response to Osteoblast Function in Spheroid Culture Induced by Low-Intensity Pulsed Ultrasound (LIPUS)

OBJECTIVE

NFκB negatively affects bone metabolism through inflammatory pathways, whereas Nrf2 benefits it by regulating antioxidant/detoxifying enzymes through antioxidant response element (ARE) activity. We investigated whether low-intensity pulsed ultrasound (LIPUS) enhances osteogenic differentiation in 3D culture and whether it affects osteoblastic differentiation-associated markers such as calcium and alkaline phosphatase (ALP), and the regulation of NFκB and/or ARE.

METHODS

Murine MC3T3-E1 preosteoblasts were used to produce 3D-spheroids, which were treated with LIPUS. Time-dependent morphological change of spheroids was evaluated by microscopy, histology, and micro-CT. To analyze changes in ARE levels, a combination of LIPUS with an optimal concentration and timing of the Nrf2-inducer sulforaphane was applied. Osteoblast differentiation and mineralization were achieved through stimulation with differentiation medium for 21-28 days, during which LIPUS was used every day at 24-hour intervals. Differentiation was evaluated using calcium and ALP assay. Finally, cells were transduced with SIN-lenti-NFκB/SIN-lenti-ARE construct, and the effects of single-shot LIPUS on NFκB and ARE were evaluated using Nano-Glo® Luciferase Assay.

RESULTS

Morphologically, in LIPUS group, shrinkage behaviour, which may correlate with cell differentiation, was observed to be more pronounced. NFκB activity with LIPUS was significantly lower than without treatment, whereas ARE activity showed significant increase only immediately after LIPUS treatment. Conversely, LIPUS enhanced ARE activity in combination with sulforaphane administration. After 28 days, the calcium content and ALP activity of LIPUS-treated spheroids increased significantly.

CONCLUSION

This study suggests that LIPUS may have NFκB-downregulating, limited ARE-raising effects in combination with sulforaphane, and elevating osteoblast mineralization three-dimensionally. Thus, LIPUS could be useful for treating fractures in conditions of oxidative stress and hyper-inflammation.

Low-intensity pulsed ultrasound reduces oxidative and endoplasmic reticulum stress in motor neuron cells

Endoplasmic reticulum (ER) stress is associated with oxidative stress, which is integral to the development of various pathological conditions, including neurodegenerative disorders. In this study, using NSC-34-a hybrid cell line established by fusing motor neuron-rich embryonic spinal cord cells with mouse neuroblastoma cells-we investigated the effects of low-intensity pulsed ultrasound (LIPUS) stimulation on oxidative (reactive oxygen species)/ER stress-induced neurodegeneration. An ultrasound transducer with a center frequency of 1.15 MHz and a spatial peak temporal average intensity of 357 mW/cm2 was used for delivering ultrasound (for 8 min, via a water-filled tube) to motor neuron cells seeded in a plastic culture dish. LIPUS stimulation significantly increased the level of the antiapoptotic protein B-cell lymphoma 2 (BCL-2) and inhibited the expression of apoptosis-associated proteins such as BCL-2-associated X protein (BAX), CCAAT/enhancer-binding protein-homologous protein (CHOP), and caspase-12, thus extending the survival of motor neurons. LIPUS stimulation also enhanced Ca2+ signaling and activated the Ca2+-dependent transcription factors as nuclear factor of activated T cells (NFAT) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Furthermore, LIPUS stimulation induced the activation of the serine/threonine kinase protein kinase B (AKT). Thus, LIPUS stimulation prevented oxidative/ER stress-mediated mitochondrial dysfunction. In conclusion, as a safe and noninvasive method, LIPUS stimulation can facilitate further development of ultrasound neuromodulation as a tool for neuroscience research.

High-intensity focused ultrasound: an innovative approach for micro-manipulation of demineralized dentine

BACKGROUND

Treatment of deep carious lesions poses significant challenges in dentistry, as complete lesion removal risks compromising pulp vitality, while selective removal often reduces the longevity of restorations. Herein, we propose a minimally invasive approach using High-Intensity Focused Ultrasound (HIFU) for microscale removal of carious dentine. Concurrently, HIFU's antimicrobial effects against associated cariogenic biofilms and the corresponding thermal and biological impacts on surrounding tissues were investigated.

METHODS

A total of 238 sound human molars were utilized, with 203 samples of artificial carious-simulated dentine (ACSD) prepared for HIFU exposure. HIFU (250 kHz) was applied at 20 W for varying durations (60, 120, and 180 s). The acoustic waves were administered via a collimated cone coupled to the dentine surface using ultrasonic gel.

RESULTS

Advanced characterization techniques including scanning electron microscopy (n = 5/group), Raman spectroscopy, atomic force microscopy, and nano-indentation (n = 5/group), demonstrated HIFU's effectiveness in removing demineralized collagen-fibrils. This was reflected in the increased mineral content, nano-hardness, and reduced elastic-modulus of ACSD lesions. Micro-CT (n = 6/group) confirmed the increase in mineral density post-HIFU exposure. Confocal microscopy of Rhodamine-B stained ACSD (n = 5/group) quantified the depth of dentine microscale removal post-HIFU exposure in a time-dependent manner. HIFU's potent anti-biofilm effect (n = 9/group) against Streptococcus mutans biofilms was evidenced by microscopic characterizations and significant reductions in metabolic-activity and colony-forming units. Furthermore, HIFU promoted the proliferation of dental pulp stem cells (n = 3/group) while maintaining the associated temperature-rise within the physiological tolerance.

CONCLUSION

HIFU's potential as an innovative, minimally invasive, non-ionizing tool for dentine carious lesion micromanipulation was demonstrated through the interaction between focused acoustic waves and dentine, warranting further studies for future clinical translation in restorative and/or preventive dentistry.

Study on the Effects of Low-Intensity Pulsed Ultrasound and Iron Ions for Proliferation and Differentiation of Osteoblasts

OBJECTIVE

This study involved the proliferation and differentiation of osteoblasts treated with low-intensity pulsed ultrasound (LIPUS) and iron (Fe3+) ions, respectively. The biological effects of LIPUS and Fe3+ ions on the proliferation and differentiation of osteoblasts were also evaluated.

METHODS

MC3T3-E1 cells were seeded in six-well plates with the medium, which contained different concentrations of Fe3+ (0, 100, 200, 300, 400, 500, 600 and 700 μg L-1, respectively). LIPUS treatment was directed at the bottom of the plate for 20 min at an intensity of 80 mW cm-2 every day.

RESULTS

Viability results showed that a dose of 400 μg L-1 Fe3+ ions had the best effect at promoting osteogenic proliferation in cell culture. The results of alkaline phosphatase staining and mineralization indicated that the differentiation of osteoblasts was promoted by LIPUS and Fe3+ ions. Fluorescence staining results showed that the number of cell nuclei in the LIPUS, Fe3+ and LIPUS-Fe groups increased by 37.20%, 55.81% and 89.76%, respectively. Migration data indicated that migration and proliferation rates were increased by LIPUS and Fe3+, and the results of protein expression indicated that LIPUS and Fe3+ may increase the expression of Wnt, β-catenin, and Runx2, hence promoting normal bone regeneration and development.

CONCLUSION

The combination of LIPUS (1.5 MHz, 80 mW cm-2) and Fe3+ accelerates the proliferation and differentiation of osteoblasts significantly compared with single-factor treatment (stimulated by LIPUS and Fe3+ ions, respectively). This study could establish a foundation for LIPUS-responsive biomaterials in the repair and regeneration of bone tissues.

Developing and Investigating a Nanovibration Intervention for the Prevention/Reversal of Bone Loss Following Spinal Cord Injury

Osteoporosis disrupts the fine-tuned balance between bone formation and resorption, leading to reductions in bone quantity and quality and ultimately increasing fracture risk. Prevention and treatment of osteoporotic fractures is essential for reductions in mortality, morbidity, and the economic burden, particularly considering the aging global population. Extreme bone loss that mimics time-accelerated osteoporosis develops in the paralyzed limbs following complete spinal cord injury (SCI). In vitro nanoscale vibration (1 kHz, 30 or 90 nm amplitude) has been shown to drive differentiation of mesenchymal stem cells toward osteoblast-like phenotypes, enhancing osteogenesis and inhibiting osteoclastogenesis simultaneously. Here, we develop and characterize a wearable device designed to deliver and monitor continuous nanoamplitude vibration to the hindlimb long bones of rats with complete SCI. We investigate whether a clinically feasible dose of nanovibration (two 2 h/day, 5 days/week for 6 weeks) is effective at reversing the established SCI-induced osteoporosis. Laser interferometry and finite element analysis confirmed transmission of nanovibration into the bone, and microcomputed tomography and serum bone formation and resorption markers assessed effectiveness. The intervention did not reverse SCI-induced osteoporosis. However, serum analysis indicated an elevated concentration of the bone formation marker procollagen type 1 N-terminal propeptide (P1NP) in rats receiving 40 nm amplitude nanovibration, suggesting increased synthesis of type 1 collagen, the major organic component of bone. Therefore, enhanced doses of nanovibrational stimulus may yet prove beneficial in attenuating/reversing osteoporosis, particularly in less severe forms of osteoporosis.

Low-intensity pulsed ultrasound reduces alveolar bone resorption during orthodontic treatment via Lamin A/C-Yes-associated protein axis in stem cells

BACKGROUND

The bone remodeling during orthodontic treatment for malocclusion often requires a long duration of around two to three years, which also may lead to some complications such as alveolar bone resorption or tooth root resorption. Low-intensity pulsed ultrasound (LIPUS), a noninvasive physical therapy, has been shown to promote bone fracture healing. It is also reported that LIPUS could reduce the duration of orthodontic treatment; however, how LIPUS regulates the bone metabolism during the orthodontic treatment process is still unclear.

AIM

To investigate the effects of LIPUS on bone remodeling in an orthodontic tooth movement (OTM) model and explore the underlying mechanisms.

METHODS

A rat model of OTM was established, and alveolar bone remodeling and tooth movement rate were evaluated via micro-computed tomography and staining of tissue sections. In vitro, human bone marrow mesenchymal stem cells (hBMSCs) were isolated to detect their osteogenic differentiation potential under compression and LIPUS stimulation by quantitative reverse transcription-polymerase chain reaction, Western blot, alkaline phosphatase (ALP) staining, and Alizarin red staining. The expression of Yes-associated protein (YAP1), the actin cytoskeleton, and the Lamin A/C nucleoskeleton were detected with or without YAP1 small interfering RNA (siRNA) application via immunofluorescence.

RESULTS

The force treatment inhibited the osteogenic differentiation potential of hBMSCs; moreover, the expression of osteogenesis markers, such as type 1 collagen (COL1), runt-related transcription factor 2, ALP, and osteocalcin (OCN), decreased. LIPUS could rescue the osteogenic differentiation of hBMSCs with increased expression of osteogenic marker inhibited by force. Mechanically, the expression of LaminA/C, F-actin, and YAP1 was downregulated after force treatment, which could be rescued by LIPUS. Moreover, the osteogenic differentiation of hBMSCs increased by LIPUS could be attenuated by YAP siRNA treatment. Consistently, LIPUS increased alveolar bone density and decreased vertical bone absorption in vivo. The decreased expression of COL1, OCN, and YAP1 on the compression side of the alveolar bone was partially rescued by LIPUS.

CONCLUSION

LIPUS can accelerate tooth movement and reduce alveolar bone resorption by modulating the cytoskeleton-Lamin A/C-YAP axis, which may be a promising strategy to reduce the orthodontic treatment process.

Study on Synergistic Effects of Nanohydroxyapatite/High-Viscosity Carboxymethyl Cellulose Scaffolds Stimulated by LIPUS for Bone Defect Repair of Rats

Despite the self-healing capacity of bone, the regeneration of critical-size bone defects remains a major clinical challenge. In this study, nanohydroxyapatite (nHAP)/high-viscosity carboxymethyl cellulose (hvCMC, 6500 mPa·s) scaffolds and low-intensity pulsed ultrasound (HA-LIPUS) were employed to repair bone defects. First, hvCMC was prepared from ramie fiber, and the degree of substitution (DS), purity, and content of NaCl of hvCMC samples were 0.91, 99.93, and 0.017%, respectively. Besides, toxic metal contents were below the permissible limits for pharmaceutically used materials. Our results demonstrated that the hvCMC is suitable for pharmaceutical use. Second, nHAP and hvCMC were employed to prepare scaffolds by freeze-drying. The results indicated that the scaffolds were porous, and the porosity was 35.63 ± 3.52%. Subsequently, the rats were divided into four groups (n = 8) randomly: normal control (NC), bone defect (BD), bone defect treated with nHAP/hvCMC scaffolds (HA), and bone defect treated with nHAP/hvCMC scaffolds and stimulated by LIPUS (HA-LIPUS). After drilling surgery, nHAP/hvCMC scaffolds were implanted in the defect region of HA and HA-LIPUS rats. Meanwhile, HA-LIPUS rats were treated by LIPUS (1.5 MHz, 80 mW cm-2) irradiation for 2 weeks. Compared with BD rats, the maximum load and bone mineral density of HA-LIPUS rats were increased by 20.85 and 51.97%, respectively. The gene and protein results indicated that nHAP/hvCMC scaffolds and LIPUS promoted the bone defect repair and regeneration of rats significantly by activating Wnt/β-catenin and inhibiting OPG/RANKL signaling pathways. Overall, compared with BD rats, nHAP/hvCMC scaffolds and LIPUS promoted bone defect repair significantly. Furthermore, the research results also indicated that there are synergistic effects for bone defect repair between the nHAP/hvCMC scaffolds and LIPUS.

The potential role of mechanotransduction in the management of pediatric calvarial bone flap repair

Pediatric patients suffering traumatic brain injuries may require a decompressive craniectomy to accommodate brain swelling by removing a portion of the skull. Once the brain swelling subsides, the preserved calvarial bone flap is ideally replaced as an autograft during a cranioplasty to restore protection of the brain, as it can reintegrate and grow with the patient during immature skeletal development. However, pediatric patients exhibit a high prevalence of calvarial bone flap resorption post-cranioplasty, causing functional and cosmetic morbidity. This review examines possible solutions for mitigating pediatric calvarial bone flap resorption by delineating methods of stimulating mechanosensitive cell populations with mechanical forces. Mechanotransduction plays a critical role in three main cell types involved with calvarial bone repair, including mesenchymal stem cells, osteoblasts, and dural cells, through mechanisms that could be exploited to promote osteogenesis. In particular, physiologically relevant mechanical forces, including substrate deformation, external forces, and ultrasound, can be used as tools to stimulate bone repair in both in vitro and in vivo systems. Ultimately, combating pediatric calvarial flap resorption may require a combinatorial approach using both cell therapy and bioengineering strategies.

Protective effects of low-intensity pulsed ultrasound (LIPUS) against cerebral ischemic stroke in mice by promoting brain vascular remodeling via the inhibition of ROCK1/p-MLC2 signaling pathway

Vascular remodeling is essential for patients with cerebral ischemic stroke (CIS). Our previous study proved that low-intensity pulsed ultrasound (LIPUS) could increase cortical hemodynamics. However, the effects and mechanisms of LIPUS on cerebral vascular remodeling after CIS are still unknown. In this study, we applied LIPUS to the mouse brain at 0.5 h after distal middle cerebral artery occlusion (dMCAO) and subsequently daily for a stimulation time of 30 min. Results showed that compared with the dMCAO group, LIPUS markedly increased cerebral blood flow (CBF), reduced brain swelling, and improved functional recovery at day 3 after CIS. LIPUS promoted leptomeningeal vasculature remodeling, enlarged vascular diameter, and increased the average vessel length and density at day 3 after CIS. Proteomic analysis highlighted that LIPUS mainly participated in the regulation of actin cytoskeleton pathway. Rho kinase 1 (ROCK1) was downregulated by LIPUS and participated in regulation of actin cytoskeleton. Subsequently, we verified that ROCK1 was mainly expressed in pericytes. Furthermore, we demonstrated that LIPUS inhibited ROCK1/p-MLC2 signaling pathway after CIS, which had positive effects on vascular remodeling and cerebral blood circulation. In conclusion, our preliminary study revealed the vascular remodeling effects and mechanism of LIPUS in CIS, provided evidence for potential clinical application of LIPUS.

Ultrasound-derived mechanical stimulation of cell-laden collagen hydrogels for bone repair

Cell therapy is emerging as an effective treatment strategy for many diseases. Here we describe a novel approach to bone tissue repair that combines hydrogel-based cell therapy with low intensity pulsed ultrasound (LIPUS), an FDA approved treatment for fracture repair. Bone marrow-derived stromal cells (BMSCs) have been encapsulated in type I collagen hydrogels and mechanically stimulated using LIPUS-derived acoustic radiation force (ARF). We observed the expression and upward trend of load-sensitive, osteoblast-specific markers and determined that the extent of cell response is dependent on an optimal combination of both hydrogel stiffness and ARF intensity. Specifically, cells encapsulated in hydrogels of optimal stiffness respond at the onset of ultrasound by upregulating early bone-sensitive markers such as calcium, cyclooxygenase-2, and prostaglandin E2 , and later by supporting mineralized tissue formation after 21 days of culture. In vivo evaluation of a critical size calvarial defect in NOD scid gamma (NSG) mice indicated that the implantation of BMSC-laden hydrogels of optimal stiffness improved healing of calvarial defects after daily administration of ARF over 4 weeks. Collectively, these findings validate the efficacy of our system of localized cell delivery for treating bone defects where undifferentiated BMSCs are induced to the osteoblastic lineage. Further, in vivo healing may be enhanced via non-invasive transdermal mechanical stimulation of implanted cells using ARF.

Pulsed frequency modulated ultrasound promotes therapeutic effects of osteoporosis induced by ovarian failure in mice

Low-intensity pulsed ultrasound (LIPUS) has been proved to be an effective technique for the treatment of osteoporosis. To better activate the bone formation-related markers, promote the different stages of osteogenesis, and further enhance the therapeutic effects of ultrasound, this study employed pulsed frequency modulated ultrasound (pFMUS) to treat mice with osteoporosis, which was caused by ovarian failure due to 4-vinylcyclohexene dioxide (VCD) injection. Healthy 8-week-old female C57BL/6J mice were randomly divided into four groups: Sham (S), VCD-control (V), VCD + LIPUS (VU), and VCD + pFMUS (VFU). VU and VFU groups were treated by LIPUS and pFMUS, respectively. Serum analysis, micro-computed tomography (micro-CT), mechanical testing and hematoxylin and eosin (HE) staining were performed to evaluate the therapeutic effects of ultrasound. Quantitative reverse-transcription PCR (qRT-PCR) and western blot analysis were used to explore the mechanism of ultrasound on osteoporosis. Results showed that pFMUS might have better therapeutic effects than traditional LIPUS in terms of bone microstructure and bone strength. In addition, pFMUS could promote bone formation by activating phosphoinositide-3 kinase/protein kinase B (PI3K/Akt) pathway, and slow down bone resorption by increasing osteoprotegerin/receptor activator of nuclear factor κB ligand (OPG/RANKL) ratio. This study is of positive prognostic significance when understanding the mechanism of ultrasound regulation on osteoporosis and establishing novel treatment plan of osteoporosis by multi-frequency ultrasound.

Effects of different physical factors on osteogenic differentiation

Osteoblasts are essential for bone formation and can perceive external mechanical stimuli, which are translated into biochemical responses that ultimately alter cell phenotypes and respond to environmental stimuli, described as mechanical transduction. These cells actively participate in osteogenesis and the formation and mineralisation of the extracellular bone matrix. This review summarises the basic physiological and biological mechanisms of five different physical stimuli, i.e. light, electricity, magnetism, force and sound, to induce osteogenesis; further, it summarises the effects of changing culture conditions on the morphology, structure and function of osteoblasts. These findings may provide a theoretical basis for further studies on bone physiology and pathology at the cytological level and will be useful in the clinical application of bone formation and bone regeneration technology.

Does low-intensity pulsed ultrasound accelerate phasic calcium phosphate ceramic-induced bone formation?

PURPOSE

Low-intensity pulsed ultrasound (LIPUS) has been used to stimulate the healing of the fresh fracture, delayed union, and non-union in both animal and clinical studies. Besides, biphasic calcium phosphate ceramic (BCP) is a promising biomaterial for bone repair as it shows favorable biocompatibility, osteoinduction, and osteoconduction. However, scarcity is known about the combined effect of LIPUS and BCP on bone formation.

METHODS

The combined effect of LIPUS and BCP was studied in a beagle model. Twelve dogs were used. BCP granules without any additions were implanted into bilateral erector spinae muscles. One side is the BCP group, while the counterlateral side is LIPUS + BCP group. Histological and histomorphometric analyses, and quantitative real-time polymerase chain reaction were evaluated.

RESULTS

Compared with BCP alone, the LIPUS + BCP showed no advantages in early bone formation. Furthermore, the Notch signaling pathway-related mRNA has no significant difference between the two groups.

CONCLUSIONS

The preliminary results showed that the BCP, which has intrinsic osteoinduction nature, was an effective and promising material. However, LIPUS has no enhanced effect in BCP induced ectopic bone formation. Furthermore, LIPUS has no effect on the Notch signaling pathway. Whether costly LIPUS could be used in combination with BCP should be a rethink.

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.

Optimization of ultrasound-assisted production of ergosterol from Penicillium brevicompactum by Taguchi statistical method

Ergosterol as a primary metabolite and precursor of vitamin D2, is the most plentiful mycosterols in fungal cell membrane. Process optimization to increase the yield and productivity of biological products is a topic of interest. Ultrasonic waves have many applications in biotechnology, like cell disruption, and enhancement of primary and secondary metabolites production. This study disclosed an optimal condition for ultrasound-assisted production (UAP) of ergosterol from Penicillium brevicompactum MUCL 19,011 using L₉ Taguchi statistical method. The intensity (IS), time of sonication (TS), treatment frequency (TF), and number of days of treatment (DT) were allocated to study the effects of ultrasound on ergosterol production. The results were analyzed using Minitab version 19. The maximum ergosterol, 11 mg/g cell dry weight (CDW), was produced on the tenth day while all factors were at a low level. The days of treatment with a contribution of 45.48% was the most significant factor for ergosterol production. For the first time, this study revealed the positive effect of ultrasound on the production of ergosterol. Ergosterol production increased 73% (4.63 mg/g CDW) after process optimization. Finally, a mathematical model of ultrasound factors with a regression coefficient of R² = 0.978 was obtained for the ergosterol production during ultrasound treatment.

Low-Intensity Pulsed Ultrasound as a Potential Adjuvant Therapy to Promote Spinal Fusion: Systematic Review and Meta-analysis of the Available Data

Despite extensive research, nonunion continues to affect a nontrivial proportion of patients undergoing spinal fusion. Recently, preclinical studies have suggested that low-intensity pulsed ultrasound (LIPUS) may increase rates of spinal fusion. In this study, we summarized the available in vivo literature evaluating the effect of LIPUS on spinal fusion and performed a meta-analysis of the available data to estimate the degree to which LIPUS may mediate higher fusion rates. Across 13 preclinical studies, LIPUS was associated with a 9-fold increase in the odds of successful spinal fusion. Future studies are necessary to establish the benefit of LIPUS on spinal fusion in clinical populations.

Longitudinal effects of low-intensity pulsed ultrasound on osteoporosis and osteoporotic bone defect in ovariectomized rats

Low-intensity pulsed ultrasound (LIPUS) with an intensity (spatial average temporal average, I_SATA) of 30 mW/cm² has been widely proved to be effective on impaired bone healing, but showing little effectiveness in the treatment of osteoporosis. We hypothesized that the intensity of LIPUS may be a key factor in explaining this difference, thus two intensity levels, the widely used 30 mW/cm² and a higher 150 mW/cm², were used to simultaneously treat osteoporosis and osteoporotic bone defect in ovariectomized (OVX) rats with a 1-mm drill hole on their left femurs.Results showed that 150 mW/cm² LIPUS augmented the healing rate of the drill hole than 30 mW/cm² after 3-week LIPUS treatment, although did not further enhance the healing rate after 6-week LIPUS treatment. For ameliorating osteoporosis, 150 mW/cm² LIPUS achieved more advantages over 30 mW/cm² in improving bone density, microstructure and biomechanics 6 weeks after LIPUS intervention. In conclusion, LIPUS with an intensity of 30 mW/cm² was sufficient to facilitate bone defect healing, but a higher intensity can be considered as a rapid trigger for osteoporotic bone repair. In addition, improving the intensity of LIPUS may be a potentially effective consideration for alleviation of osteoporosis, and the LIPUS regimen in the treatment of osteoporosis remains to be optimized.

Bone fracture healing: perspectives according to molecular basis

Fractures have a great impact on health all around the world and with fracture healing optimization; this problem could be resolved partially. To make a practical contribution to this issue, the knowledge of bone tissue, cellularity, and metabolism is essential, especially cytoskeletal architecture and its transformations according to external pressures. Special physical and chemical characteristics of the extracellular matrix (ECM) allow the transmission of mechanical stimuli from outside the cell to the plasmatic membrane. The osteocyte cytoskeleton is conformed by a complex network of actin and microtubules combined with crosslinker proteins like vinculin and fimbrin, connecting and transmitting outside stimuli through EMC to cytoplasm. Herein, critical signaling pathways like Cx43-depending ones, MAPK/ERK, Wnt, YAP/TAZ, Rho-ROCK, and others are activated due to mechanical stimuli, resulting in osteocyte cytoskeletal changes and ECM remodeling, altering the tissue and, therefore, the bone. In recent years, the osteocyte has gained more interest and value in relation to bone homeostasis as a great coordinator of other cell populations, thanks to its unique functions. By integrating the latest advances in relation to intracellular signaling pathways, mechanotransmission system of the osteocyte and bone tissue engineering, there are promising experimental strategies, while some are ready for clinical trials. This work aims to show clearly and precisely the integration between cytoskeleton and main molecular pathways in relation to mechanotransmission mechanism in osteocytes, and the use of this theoretical knowledge in therapeutic tools for bone fracture healing.

Effect of Acoustic Cavitation on Mouse Spermatogonial Stem Cells: Colonization and Viability

OBJECTIVES

The mechanical index has long been one of the main criteria used to assess the safety limits for therapeutic medical applications. However, the safety of the mechanical index parameter is considered to be unknown in male fertility, which has a very significant role in vitro conditions. In this study, the effect of cavitation interactions due to mechanical index regions was evaluated on spermatogonial stem cells.

METHODS

The acoustic pressure and mechanical index equations at the low intensities and the intended frequency were modeled and solved. The mechanical index average of 40 kHz frequency was selected as subthreshold, 0.70, and above the cavitation threshold. Neonatal spermatogonial stem cells were cultured. Spermatogonial stem cells are stimulated by low-level ultrasound for 5 days and colonization and viability evaluated on the seventh day.

RESULTS

Based on modeling, the mechanical index average was chosen as 0.40, 0.51, 0.75, and 0.89. The mechanical index of 0.40 and 0.89 resulted in a number of colonies of 93 ± 4 and 32 ± 4, respectively. An increase in colony diameter could be observed for a 0.40 mechanical index during all days of the culture that in the culture on the seventh day had the largest average colony diameter of 174.05 ± 1.22 μm in comparison with other groups (p < 0.05). The cell viability was not significantly different among the groups.

CONCLUSION

The results suggest that a low-intensity ultrasound of 40 kHz with a 0.40 mechanical index can be effective in increasing the proliferation and colonization of spermatogonia in stem cells during culture.

Effect of inorganic phosphate on migration and osteogenic differentiation of bone marrow mesenchymal stem cells

Background

Phosphate is the major ingredient of bone tissue, and is also an important component of commercial bone substitute materials, bone scaffolds, and implant surface coatings. With the dissolution of the bone substitute materials and the degradation by cells, local ion concentrations will change and affect bone tissue reconstruction. Bone marrow -derived mesenchymal stem cells (BM-MSCs) are main autologous cells to repair injured bone. When bone injure occurs, BM-MSCs migrate to the damaged area, differentiate into osteoblasts, and secrete bioactive factors to promote bone tissue repaired. This study aimed to investigate the effect of inorganic phosphate (Pi) at a series of concentration on migration and osteogenic differentiation of human bone marrow -derived mesenchymal stem cells(hBM-MSCs).

Methods

The culture of hBM-MSCs in mediums with different concentration of Pi from 2 mM to 10 mM were performed. HBM-MSCs migration were examined with transwell assays. HBM-MSCs proliferation were evaluated by cell counting kit-8 colorimetric method. Osteogenic genes expression were analyzed by real-time reverse transcriptase polymerase chain reaction. Mineralized nodules formation were demonstrated by Alizarin red staining.

Result

4–10 mM Pi could effectively promote the migration of hBM-MSCs at 12 h and 18 h. There was no significant difference in the migration number of hBM-MSCs in Pi culture mediums at a concentration of 6, 8, and10mM. 2–10 mM Pi could promote the proliferation of hBM-MSCs to varying degrees in the observation period, while 4–10 mM Pi could promote the osteogenic differentiation and mineralization of hBM-MSCs.

Conclusion

The findings in our study showed 4-10 mM Pi could promote the migration, osteogenic differentiation, and mineralization of hBM-MSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12861-020-00229-x.

[A review of mechanisms by which low-intensity pulsed ultrasound affects bone regeneration]

Low-intensity pulsed ultrasound (LIPUS) is a common physical therapy to accelerate the healing of bone fracture and treat delayed union of bone fracture. Vessels, nerves, and bone tissue are essential constituents of bone system. Recently, increasing evidence has been revealed that LIPUS can not only promote bone regeneration by directly regulating osteoblasts, osteoblasts, mesenchymal stem cells, but also have a positive impact on the repair of bone healing through vessels and nerves. Thus, we reviewed and summarized the latest published literature about the molecular mechanism for the effects of LIPUS on bone regeneration, which might offer a promising therapy for bone-related diseases.