Effects of He-Ne Laser Photobiomodulation on Cortical Bone Regeneration in a Rat Femoral Defect Model

A metaphyseal bone defect due to infection, tumor or fracture leads to loss of cancellous and cortical bone. An animal model separating the cancellous and cortical healing was used with a combination of a macroporous gelatin-calcium sulphate-hydroxyapatite (Gel-CaS-HA) biomaterial as a cancellous defect filler, and a thin collagen membrane (CM) guiding cortical bone regeneration. The membrane was immobilized with bone morphogenic protein-2 (rhBMP-2) to enhance the osteoinductive properties. The Gel-CaS-HA cancellous defect filler contained both rhBMP-2 and a bisphosphonate, (zoledronate = ZA) to prevent premature callus resorption induced by the pro-osteoclast effect of rhBMP-2 alone. In the first part of the study, the CM delivering both rhBMP-2 and ZA was tested in a muscle pouch model in rats and the co-delivery of rhBMP-2 and ZA via the CM resulted in higher amounts of bone compared to rhBMP-2 alone. Secondly, an established tibia defect model in rats was used to study cortical and cancellous bone regeneration. The defect was left empty, filled with Gel-CaS-HA alone, Gel-CaS-HA immobilized with ZA or Gel-CaS-HA immobilized with rhBMP-2+ZA. Functionalization of the Gel-CaS-HA scaffold with bioactive molecules produced significantly more bone in the cancellous defect and its surroundings but cortical defect healing was delayed likely due to the protrusion of the Gel-CaS-HA into the cortical bone. To guide cortical regeneration, the cortical defect was sealed endosteally by a CM with or without rhBMP-2. Subsequently, the cancellous defect was filled with Gel-CaS-HA containing ZA and rhBMP-2+ZA. In the groups where the CM was doped with rhBMP-2, significantly higher number of cortices bridged. The approach to guide cancellous as well as cortical bone regeneration separately in a metaphyseal defect using two bioactive molecule immobilized biomaterials is promising and could improve the clinical care of patients with metaphyseal defects.

Bone is composed of dense and solid cortical bone and honeycomb-like trabecular bone. Although cortical bone provides the majority of mechanical strength for a bone, there are few studies focusing on cortical bone repair or regeneration. Osteons (the Haversian system) form structural and functional units of cortical bone. In recent years, emerging evidences have shown that the osteon structure (including osteocytes, lamellae, lacunocanalicular network, and Haversian canals) plays critical roles in bone mechanics and turnover. Therefore, reconstruction of the osteon structure is crucial for cortical bone regeneration. This article provides a systematic summary of recent advances in osteons, including the structure, function, turnover, and regenerative strategies. First, the hierarchical structure of osteons is illustrated and the critical functions of osteons in bone dynamics are introduced. Next, the modeling and remodeling processes of osteons at a cellular level and the turnover of osteons in response to mechanical loading and aging are emphasized. Furthermore, several bioengineering approaches that were recently developed to recapitulate the osteon structure are highlighted. Impact statement This review provides a comprehensive summary of recent advances in osteons, especially the roles in bone formation, remodeling, and regeneration. Besides introducing the hierarchical structure and critical functions of osteons, we elucidate the modeling and remodeling of osteons at a cellular level. Specifically, we highlight the bioengineering approaches that were recently developed to mimic the hierarchical structure of osteons. We expect that this review will provide informative insights and attract increasing attentions in orthopedic community, shedding light on cortical bone regeneration in the future.

This study investigated the effects of repeated helium-neon (He-Ne) laser-based photobiomodulation therapy (PBMT) on bone healing in a rat femoral defect model. Bilateral 0.8-mm monocortical bone defects were created in the distal femurs of Sprague-Dawley rats, with one side receiving repeated He-Ne laser irradiation (632.8 nm, 25 mW, 7.5 J) and the other serving as a control. Histological and image-based bone density analyses were performed on postoperative days 7 and 14. The irradiated group exhibited enhanced trabecular bone formation and significantly higher bone density on day 7, particularly in the marrow region. However, bone density decreased in this group by day 14, suggesting progression to bone remodeling. These findings indicate that PBMT using He-Ne laser promotes early-stage bone formation and may accelerate the bone healing process, thus supporting the therapeutic potential of PBMT for bone regeneration.

Background:Platelet-rich plasma (PRP) can provide an assortment of growth factors, but how PRP effects bone regeneration is still unknown. The aim of the study was to explore an optimal method of using PRP and bone marrow stromal cells (BMSCs).Methods:An in vitro experiment was first conducted to determine an appropriate quantity of PRP. BMSCs were cultured with PRP of different concentrations to assess cell proliferation and osteogenic differentiation. Following the in vitro study, a rat femoral segmental defect model was used. Five collagen mixtures consisting of different concentrations of PRP and BMSCs were prepared as follows, i) BMSCs and PRP (platelet 20 x 104/µl), ii) BMSCs and PRP (platelet 100 x 104/µl), iii) BMSCs and PRP (platelet 500 x 104/µl), iv) BMSCs, and v) PRP group (platelet 100 x 104/µl), were used to fill defect. New bone formation was evaluated by soft X-ray and histologic analyses were performed at 2, 4, 6 and 8 weeks postoperatively.Results:The cell proliferation increased PRP concentration-dependently. Cellular alkaline phosphatase activity was higher in moderate concentration than high or low concentration group’s in vitro study. In vivo study, the bone fill percentage of newly formed bone in BMSCs and PRP (platelet 100 x 104/µl) was 46.9% at 8 weeks and increased significantly compared with other groups.Conclusion:BMSCs with moderate level of PRP significantly enhanced bone formation in comparison with BMSCs or PRP transplant in a rat femoral defect model.

Parameter Reproducibility in Photobiomodulation.

Consensus Agreement on the Design and Conduct of Clinical Studies with Low-Level Laser Therapy and Light Therapy for Musculoskeletal Pain and Disorders

Bone regeneration is a complex process influenced by inflammation and pathological conditions. Efforts to enhance this process include chemical and physical interventions, with PBMT therapy showing promise in improving bone regeneration. Despite conflicting findings in existing literature, this review aims to synthesize clinical evidence on using therapy (PBMT) in bone regeneration and explore its potential clinical applications. A systematic search was performed on electronic databases such as Web of Science, Scopus, and PubMed from the beginning until May 2024 for randomized clinical trials that reported the result of PBMT on bone regeneration. The search strategy involved using a mix of relevant medical subject headings (MeSH) terms and pertinent keywords such as photobiomodulation therapy, low-level laser therapy, bone, regeneration, PBMT, and LLLT. From an initial search identifying 1920 articles, this review centered on 13 articles for analysis, predominantly utilizing radiographical or cone-beam computed tomography (CBCT) assessments. Among these, 7 studies indicated that photobiomodulation therapy (PBMT) did not have a significant impact on bone regeneration. Conversely, 4 studies showed a substantial enhancement in bone density and regeneration with PBMT. Furthermore, 2 studies investigated the impact of varying laser characteristics on case and control groups, concluding no significant difference. In spite of the conflicting results from studies mentioned above, it appears that photobiomodulation has shown positive effects on bone reconstruction. However, further research is necessary to optimize the selection of physical parameters of laser such as wavelength, energy density, and power, as they are crucial for optimizing the effectiveness of photobiomodulation for clinical use.

Laser (and LED) Therapy Is Phototherapy

Evaluate the immediate (within 4 hours) effects of laser-induced photobiomodulation (PBM) therapy on Achilles tendon morphology and mechanical properties in healthy and pathologic tendons. Twenty people with healthy Achilles tendons and twelve people with Achilles tendinopathy participated. One Achilles tendon received PBM treatment following an established protocol and the contralateral side received a placebo treatment. Achilles tendon morphology and mechanical properties were evaluated bilaterally with ultrasound imaging and continuous shear wave elastography immediately before treatment, immediately after treatment, then 2- and 4-hours after treatment. There were no immediate effects of PBM on tendon morphology or mechanical properties when comparing the PBM-treated side and placebo-treated side within each cohort. Additionally, the effects of PBM did not differ between healthy and pathologic Achilles tendons. When treated with a laser-induced PBM treatment, healthy and pathologic Achilles tendons do not have immediate (within 4 hours) changes in tendon morphology or mechanical properties. These findings suggest that PBM therapy can be administered before other clinical treatments or high-load activities.

This study aimed to compare in vivo osteogenesis on rough threaded dental implants with and without calcium phosphate (CaP) coating deposition, alone or in association with low-level laser therapy (LLLT) by gallium aluminum arsenide. Four groups were studied: G1: implant; G2: implant + CaP coating; G3: implant + LLLT; and G4: implant + CaP coating + LLLT. LLLT was applied for 7 days at the surgical site before and after placing the implant. Topographic characterization was performed before surgery using scanning electron microscopy and energy dispersion spectrophotometry. Bone-implant contact (BIC) was measured after 1, 2, and 6 weeks and reverse torque after 6 weeks. In short periods, G2, G3, and G4 showed significantly greater BIC than G1 (P < 0.05), but no difference in BIC was observed at 6 weeks. However, the values for the removal torque test at 6 weeks were higher in G2 and G4 (P < 0.05). Both CaP coating alone and using LLLT induce cellular stimulation and improve BIC in short-term healing, resulting in higher implant fixation, and should be considered in clinical practice due to their low cost and high effectiveness.

Photobiomodulation (PBM) therapy has attracted major interest in the field of tissue engineering as it can enhance stem cell differentiation. It has been shown that PBM therapy can stimulate differentiation of cells in culture by exerting biomodulatory effect. Recent evidences show that PBM therapy can positively modulate dental pulp stem cell (DPSC) properties. Combination of PBM therapy with growth factors and biomaterials can possibly accelerate osteogenic differentiation of dental pulp stem cells. To evaluate the biomodulatory effect of low-level laser dose on dental pulp stem cells in the presence of hydroxyapatite-based scaffold particle for osteogenic differentiation. DPSCs were harvested from human premolar teeth and expanded using mesenchymal stem cell medium. Characterization of DPSCs was done using fluorescence-activated cell sorting with CD105, CD44, CD34, and CD45 markers. Cultured DPSCs along with the N-acetylcysteine-labeled hydroxyapatite (NAC-HA) particles and osteogenic differentiation media were exposed to gallium-aluminum-arsenide (Ga-Al-As) diode laser at 810 nm. Cells were divided into 3 groups: L1 (single exposure), L2 (double exposure), and control (no exposure). Osteodifferentiation after PBM therapy was assessed using Alizarin red S staining, Alkaline phosphatase activity (ALP), and by osteopontin expression. Differences between groups at each time point were analyzed using the Mann–Whitney U test. A level of significance of 5% was adopted (p < 0.05). DPSCs grown on NAC-HA polymers show increased cell adhesion and proliferation. Double irradiated groups were consistent with increased calcium (71%) and alkaline phosphatase activity (75%) when compared with single-irradiated groups. mRNA expression of osteopontin was relatively increased in a significant (p < 0.001) manner in L2 when compared with L1 group. Alizarin red S and ALP positive staining confirmed the presence of calcium deposition in the test samples. The osteopontin expression of L2 (216.681) as compared with L1 (123.276) group prove the efficacy of double exposures over a single dose of PBM therapy. The result envisages the enhanced osteogenic potential of PBM therapy on the differentiation of DPSCs in NAC-HA scaffolds. Double exposure of PBM therapy expresses better biomodulatory effect on DPSCs as compared with the single dose.

This systematic review aimed to answer the research focused question: What are the effects of photobiomodulation (PBM) therapy on bone healing after ionizing irradiation in animal models? The EMBASE, LILACS, LIVIVO, PubMed, Scopus, and Web of Science databases, including gray literature, were searched using the following keywords: "Head and Neck Neoplasms"; "Ionizing Radiation"; "Low-Level Light Therapy"; and "Bone regeneration", focusing on the primary studies that assessed the effects of PBM therapy on animal models of irradiated bone. Six studies have met the eligibility criteria and presented an overall regular quality according to the risk of bias assessment tools. All the studies utilized rat animal model and near-infrared laser PBM at low power output setting. Most of the studies showed increased new bone formation, osteocytes, osteoblasts, and vascularization networking, as a result of PBM therapy. However, only one out of the six studies has not shown any differences in bone healing in both lased and non-lased animal groups. Nevertheless, PBM therapy is a potential tool to improve bone healing induced by ionizing radiation. However, due to the scarce number of studies and the great variability of laser parameters and treatment protocols, a clear conclusion cannot be drawn. Hence, extensive preclinical in vivo studies are warranted to ensure these beneficial effects have been addressed prior to translational clinical trials.

Low-level light/laser therapy versus photobiomodulation therapy.

Background: Transcranial photobiomodulation (PBM) therapy has emerged as a promising alternative therapeutic option for the management of neurological and psychiatric disorders. However, the underlying mechanisms of PBM therapy and its effects on motor performance in brain disorders are not yet fully understood. The aim of this literature review is to provide a more detailed and evidence-based explanation of the rationale and intent behind the correlation between PBM therapy and its effects on motor performance in brain disorders. Methods: A literature search was performed in the databases "PubMed/Medline", "Scopus," and "Google Scholar" for all relevant English language papers. A combination of different keywords was used for the database search. Video articles, patents, review articles, book chapters, articles using other transcranial methods, non-transcranial PBM, and case reports were excluded. Results: Out of the 2174 papers, 18 addressed the effect of PBM on motor performance. Among these, four studies were on ischemic stroke models and individuals with stroke, six studies on models associated with traumatic brain injury (TBI), five studies on models associated with neurodegenerative diseases and Parkinson's disease, and four studies related to models and patients with central nervous system inflammation. All studies have shown that motor parameters improve with PBM. In two studies on healthy individuals, 65 showed improvement in motor function and 16 showed improvement in motor evoked potential. In most studies (n=10), the wavelength used was between 800 and 900 nm. Near-infrared or LED continuous light was used in most studies. However, two studies compared the effects of pulsed and continuous waves and found the superiority of pulsed over continuous waves. Conclusions: PBM therapy appears to be useful in brain injury, inducing changes at the behavioral, motor, cellular, and chemical levels. Recent studies suggest that PBM therapy may have potential benefits in improving motor performance in brain disorders, including stroke, traumatic brain injury, Parkinson's disease, and demyelination. However, further research is needed to determine the optimal parameters for PBM therapy and to investigate its effects on motor function in different brain disorders. Overall, PBM therapy appears to be a promising therapeutic option for brain injury and warrants further investigation.

This research aims to examine the influence of human skull bone thickness and density on light penetration in PBM therapy across different wavelengths, focusing on how these bone characteristics affect the absorption of therapeutic light. Analyses explored the effect of skull bone density and thickness on light penetration in PBM, specifically using Low-Level Laser Therapy (LLLT) for efficacy prediction. Measurements of bone thickness and density were taken using precise tools. This approach emphasizes LLLT's significance in enhancing PBM outcomes by assessing how bone characteristics influence light penetration. The study revealed no significant correlation between skull bone density and thickness and light penetration capability in photobiomodulation (PBM) therapy, challenging initial expectations. Wavelengths of 405 nm and 665 nm showed stronger correlations with bone density, suggesting a significant yet weak impact. Conversely, wavelengths of 532 nm, 785 nm, 810 nm, 830 nm, 980 nm, and 1064 nm showed low correlations, indicating minimal impact from bone density variations. However, data variability (R2 < 0.4) suggests that neither density nor thickness robustly predicts light power traversing the bone, indicating penetration capability might be more influenced by bone thickness at certain wavelengths. The study finds that the effectiveness of photobiomodulation (PBM) therapy with bone isn't just based on bone density and thickness but involves a complex interplay of factors. These include the bone's chemical and mineral composition, light's wavelength and energy dose, treatment duration and frequency, and the precise location where light is applied on the skull.