Low level laser irradiation stimulates osteogenic phenotype of mesenchymal stem cells seeded on a three-dimensional biomatrix

Photomodulation of proliferation and differentiation of stem cells by the visible and infrared light

OBJECTIVE

The aim of this article is to review experimental studies of visible and infrared light irradiation of human and animal stem cells (SCs) in vitro and in vivo to assess photobiomodulation effects on their proliferation and differentiation.

BACKGROUND DATA

The clinical application of light irradiation remains controversial, primarily because of the complexity of the rational choice of irradiation parameters. In laboratories, the theoretical justification underlying the choice of irradiation parameters also remains a challenge.

METHODS

A systematic review was completed of original research articles that investigated the effects of light irradiation on human and animal SCs in vitro and in vivo (to June 2014). Relevant articles were sourced from PubMed and MEDLINE(®). The search terms were laser (light) therapy (irradiation), stem cells, and phototherapy, stem cells.

RESULTS

The analysis revealed the importance of cell type when choosing the cell irradiation parameters. The influence of wavelength on the SC proliferation rate seemed to be nonsignificant. The high values of increased proliferation or differentiation were obtained using high power density, low energy density, and short exposure time. SC exposure to light without inducers did not lead to their differentiation. The maximum differentiation was achieved using irradiation parameters different from the ones needed to achieve the maximum proliferation of the same cells.

CONCLUSIONS

Increased power density and reduced energy density were needed to increase the SC response. Based on the analysis, we have presented a graph of the cell response to generalized photostimulus, and introduced the concepts of "photostress" and "photoshock" to describe the stages of this response.

Laser phototherapy at high energy densities do not stimulate pre-osteoblast growth and differentiation

OBJECTIVE

The aim of this study is to evaluate the effects of red and infrared lasers at high energy densities on pre-osteoblast MC3T3 proliferation and differentiation.

BACKGROUND DATA

The acceleration of bone regeneration by low intensity laser irradiation may hold potential benefits in clinical therapy in orthopedics and dentistry.

MATERIALS AND METHODS

Cells were irradiated with red (660 nm) and infrared (780 nm) lasers (90 and 150 J/cm2, 40 mW). The control group did not receive irradiation. Cell growth was assessed by a colorimetric test (MTT) (24, 48, 72, 96 h) and cell differentiation was evaluated by alkaline phosphatase (ALP) quantification after growth in osteogenic medium (72, 96 h; 7, 14 days).

RESULTS

None of the irradiation groups had an enhancement in cell growth (p<0.05). The production of ALP was not influenced by irradiation at any period of time (p>0.05).

CONCLUSIONS

The low intensity laser stimulated neither cell growth nor the production of alkaline phosphatase.

Effect of low-level laser on bone defects treated with bovine or autogenous bone grafts: in vivo study in rat calvaria

Objective. The purpose of this study was to histologically evaluate the effect of low-level laser (LLL) on the healing of critical size defects (CSD) in rat calvaria, filled with autogenous or inorganic bovine bone grafts. Methods. Sixty rats were divided into 6 groups (n = 10): C (control—filled with blood clot), LLL (low-level laser—GaAlAs, λ 780 nm, 100 mW, 210 J/cm², Φ 0.05 cm²; 6 J/point), AB (autogenous bone), ABL (autogenous bone + low-level laser), OB (inorganic bovine bone), and OBL (inorganic bovine bone + LLL). Material and Methods. The animals were killed after 30 days. Histological and histometric analyses were performed by light microscopy. Results. The groups irradiated with laser, LLL (47.67% ± 8.66%), ABL (39.15% ± 16.72%), and OBL (48.57% ± 28.22%), presented greater area of new bone formation than groups C (9.96% ± 4.50%), AB (30.98% ± 16.59%), and OB (11.36% ± 7.89%), which were not irradiated. Moreover, they were significantly better than group C (Kruskal-Wallis test followed by Dunn test, P < 0.05). Conclusion. The laser accelerated the healing of bone defects and the resorption of particles of the graft material.

Low-level laser therapy promotes the osteogenic potential of adipose-derived mesenchymal stem cells seeded on an acellular dermal matrix

This study investigates the feasibility of using an adipose-derived mesenchymal stem cell (ASC)-seeded acellular dermal matrix (ADM) along with low-level laser therapy (LLLT) to repair bone defect in athymic nude mice. Critical-sized calvarial defects were treated either with ADM, ADM/LLLT, ADM/ASCs, or ADM/ASCs/LLLT. In micro-computed tomography scans, the ADM/ASCs and the ADM/ASCs/LLLT groups showed remarkable bone formation after 14 days. Additionally, bone regeneration in the ADM/ASCs/LLLT group was obvious at 28 days, but in the ADM/ASCs group at 56 days. Bone mineral density and bone tissue volume in the ADM/ASCs/LLLT group significantly increased after 7 days, but in the ADM/ASCs group after 14 days. Histological analysis revealed that the defects were repaired in the ADM/ASCs and the ADM/ASCs/LLLT group, while the defects in the ADM and the ADM/LLLT groups exhibited few bone islands at 28 and 56 days. The successful seeding of ASCs onto ADM was confirmed, and LLLT enhanced the proliferation and the survival of ASCs at 14 days. Our results indicate that ASC-seeded grafts promote bone regeneration, and the application of LLLT on ASC-seeded ADM results in rapid bone formation. The implantation of an ASC-seeded ADM combined with LLLT may be used effectively for bone regeneration.

Laser and light-emitting diode effects on pre-osteoblast growth and differentiation

The acceleration of bone regeneration by low-intensity laser irradiation may hold potential benefits in clinical therapy in orthopedics and dentistry. The purpose of this study is to compare the effects of light-emitting diode (LED) and laser on pre-osteoblast MC3T3 proliferation and differentiation. Cells were irradiated with red, infrared, and LED (3 and 5 J/cm(2)). Lasers had a power density of 1 W/cm(2) and irradiation time of 2 and 5 s. LED had a power density of 60 mW/cm(2) and irradiation time of 50 and 83 s. Control group did not receive irradiation. Cell growth was assessed by a colorimetric test (MTT) (24, 48, 72, and 96 h), and cell differentiation was evaluated by alkaline phosphatase (ALP) quantification after growth in osteogenic medium (72 and 96 h and 7 and 14 days). At 24 h, the cell growth was enhanced 3.6 times by LED (5 J/cm(2)), 6.8 times by red laser (3 J/cm(2)), and 10.1 times by red laser (5 J/cm(2)) in relation to control group (p < 0.05). At the other periods, there was no influence of irradiation on cell growth (p > 0.05). The production of ALP was not influenced by irradiation at any period of time (p > 0.05). Low-intensity laser and LED have similar effects on stimulation of cell growth, but no effect on cell differentiation.

Visible 532 nm laser irradiation of human adipose tissue-derived stem cells: effect on proliferation rates, mitochondria membrane potential and autofluorescence

BACKGROUND AND OBJECTIVE

The photobiological effect of laser light on cells and tissues originates from light absorption by endogenous chromophores and hence it depends on the wavelength of light source and cell type. Earlier studies regarding the biostimulation effects of green laser light investigated a wide variety of cells but not adipose tissue-derived stem cells (ADSCS). In this study we reported the in vitro effect of 532-nm Nd:YAG laser on proliferation, mitochondrial activity of these mesenchymal stem cells (MSCs) on the autofluorescence emission at wavelengths associated with nicotinamide adenine dinucleotide (NADH) and flavoproteins.

MATERIALS AND METHODS

ADSCS were exposed to 532 nm second harmonic generation laser light at moderate power density (0.153 W/cm(2)) for periods of 30, 45, 60, 180, and 300 seconds. Mitochondrial membrane potential was measured using JC1 stain and confocal laser scanning microscopy, cell proliferation rates, and cellular autofluorescence emission at 450 and 540 nm wavelengths were measured using micro plate spectrofluorometer 48 hours after irradiation.

RESULTS

Shorter (30-60 seconds) exposure times led to significantly increased proliferation, attributed to increased mitochondrial activity (P < 0.05). At longer exposures we observed a significant decrease in proliferation and autofluorescence (P < 0.05). Strong correlation was observed between proliferation rates of cells and autofluorescence intensity.

CONCLUSION

Our results show that autofluorescence of the respiratory chain components and key autofluorescent metabolites offers a non-invasive method to quantify cellular response to laser irradiation.

Enhanced wound healing effect of canine adipose-derived mesenchymal stem cells with low-level laser therapy in athymic mice

BACKGROUND

Adipose-derived mesenchymal stem cells (ASCs) are attractive cell source for skin tissue engineering. However, one obstacle to this approach is that the transplanted ASC population can decline rapidly in the recipient tissue.

OBJECTIVE

The aim of this study was to investigate the effects of low-level laser therapy (LLLT) on transplanted canine ASCs in a skin wound animal model.

METHODS

LLLT, ASC transplantation (ASCs) and ASC transplantation with LLLT (ASCs+LLLT) were applied to the wound bed in athymic mice. Wound healing was assessed by gross evaluation and by hematoxylin and eosin staining. The survival, differentiation and secretion of vascular endothelial growth factor and basic fibroblast growth factor of the ASCs were evaluated by immunohistochemistry and Western blotting.

RESULTS

The ASCs and ASCs+LLLT groups stimulated wound closure and histological skin regeneration. The ASCs+LLLT group enhanced the wound healing, including neovascularization and regeneration of skin appendages, compared with the ASCs group. The ASCs contributed skin regeneration via differentiation and secretion of growth factors. In the ASCs+LLLT group, the survival of ASCs was increased by the decreased apoptosis of ASCs in the wound bed. The secretion of growth factors was stimulated in the ASCs+LLLT group compared with the ASCs group.

CONCLUSION

These data suggest that LLLT is an effective biostimulator of ASCs in wound healing that enhances the survival of ASCs and stimulates the secretion of growth factors in the wound bed.

Shining light on nanotechnology to help repair and regeneration

Phototherapy can be used in two completely different but complementary therapeutic applications. While low level laser (or light) therapy (LLLT) uses red or near-infrared light alone to reduce inflammation, pain and stimulate tissue repair and regeneration, photodynamic therapy (PDT) uses the combination of light plus non-toxic dyes (called photosensitizers) to produce reactive oxygen species that can kill infectious microorganisms and cancer cells or destroy unwanted tissue (neo-vascularization in the choroid, atherosclerotic plaques in the arteries). The recent development of nanotechnology applied to medicine (nanomedicine) has opened a new front of advancement in the field of phototherapy and has provided hope for the development of nanoscale drug delivery platforms for effective killing of pathological cells and to promote repair and regeneration. Despite the well-known beneficial effects of phototherapy and nanomaterials in producing the killing of unwanted cells and promoting repair and regeneration, there are few reports that combine all three elements i.e. phototherapy, nanotechnology and, tissue repair and regeneration. However, these areas in all possible binary combinations have been addressed by many workers. The present review aims at highlighting the combined multi-model applications of phototherapy, nanotechnology and, reparative and regeneration medicine and outlines current strategies, future applications and limitations of nanoscale-assisted phototherapy for the management of cancers, microbial infections and other diseases, and to promote tissue repair and regeneration.

The effect of noncoherent red light irradiation on proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells

Mesenchymal stem cells (MSCs) are promising for use in regenerative medicine. Low-level light irradiation (LLLI) has been shown to modulate various processes in different biological systems. The aim of our study was to investigate the effect of red light emitted from a light-emitting diode (LED) on bone marrow MSCs with or without osteogenic supplements. MSCs both with and without osteogenic supplements were divided into four groups, and each group was irradiated at doses of 0, 1, 2 and 4 J/cm(2). Cellular proliferation was evaluated using WST-8 and 5-ethynyl-2'-deoxyuridine (EdU) fluorescence staining. The alkaline phosphatase activity, mineralization, and expression of osteoblast master genes (Col1α1, Alpl, Bglap and Runx2) were monitored as indicators of MSC differentiation towards osteoblasts. In groups without osteogenic supplements, red light at all doses significantly stimulated cellular proliferation, whereas the osteogenic phenotype of the MSCs was not enhanced. In groups with osteogenic supplements, red light increased alkaline phosphatase activity and mineralized nodule formation, and stimulated the expression of Bglap and Runx2, but decreased cellular proliferation. In conclusion, nonconherent red light can promote proliferation but cannot induce osteogenic differentiation of MSCs in normal media, while it enhances osteogenic differentiation and decreases proliferation of MSCs in media with osteogenic supplements.

Transcriptional regulation of bone sialoprotein gene by CO(2) laser irradiation

Bone sialoprotein (BSP), an early marker of osteoblast differentiation, has been implicated in the nucleation of hydroxyapatite during de novo bone formation. Low-power laser irradiation has a stimulating effect on cells and tissues. Although the carbon dioxide (CO(2)) laser is a hard surgical laser, we have attempted to use it at low energy density to achieve biological alterations. To investigate the effects of CO(2) laser irradiation on BSP gene transcription, we used rat osteoblast-like ROS17/2.8 cells. BSP mRNA levels were increased at 12 h after irradiation with the CO(2) laser (2 W, 20 s). Transient transfection assays using various sizes of the rat BSP gene promoter linked to the luciferase reporter gene showed that CO(2) laser irradiation induced luciferase activity of a -116 to +60 BSP promoter construct (pLUC3) at 12 h in the cells. Transcriptional stimulation by CO(2) laser irradiation was abrogated in the pLUC3 construct containing a 2-bp mutation in the fibroblast growth factor 2 response element (FRE). Gel shift analyses showed that CO(2) laser irradiation increased the binding of nuclear protein to FRE. These studies demonstrate that CO(2) laser irradiation increases BSP transcription via FRE in the rat BSP gene promoter.

The effect of photosensitizer drugs and light stimulation on osteoblast growth

OBJECTIVE

A promising new treatment in dentistry involves the photodynamic process, which utilizes a combination of two therapeutic agents, namely a photosensitizer drug and a low dose of visible light. We investigated the in vitro effect of low intensity laser irradiation (visible light irradiation at 670 nm) using doses ranging between 0.5 and 3 J/cm(2), combined with nanoemulsion (NE) of the photosensitizer drug aluminum phthalocyanine chloride (AlClPc), ranging from 0.5 to 5 μmol/L, on the growth and differentiation of osteoblastic cells isolated from rat bone marrow.

BACKGROUND DATA

Treatments using laser radiation of low intensity in dentistry are of great interest, especially in bucco-maxillofacial surgery and dental implantology, where this approach is currently employed to stimulate osteogenesis. In the presence of oxygen, the combination of these agents could induce cellular biostimulation, via an efficient noninvasive method.

METHODS

We have done the colorimetric MTT assay, collagen content, total protein content, ALP activity and bone-like nodule formation.

RESULTS

We observed that an increased number of viable cells was evident upon application of a laser dosage equal to 0.5 J/cm(2) when combined with 0.5 μmol/L of AlClPc/NE, suggesting cellular biostimulation.

CONCLUSIONS

It was possible to demonstrate that low intensity laser irradiation can play an important role in promoting biostimulation of osteoblast cell cultures. Therefore, whether biostimulation of osteoblastic cell cultures by photodynamic therapy or the cytotoxic effect of this therapy occurs only depends upon the light dose, and the results can be completely reversed.

The effects of low-level laser irradiation on differentiation and proliferation of human bone marrow mesenchymal stem cells into neurons and osteoblasts--an in vitro study

Bone marrow-derived mesenchymal stem cells (BMSCs) are promising for use in regenerative medicine. Several studies have shown that low-level laser irradiation (LLLI) could affect the differentiation and proliferation of MSCs. The aim of this study was to examine the influence of LLLI at different energy densities on BMSCs differentiation into neuron and osteoblast. Human BMSCs were cultured and induced to differentiate to either neuron or osteoblast in the absence or presence of LLLI. Gallium aluminum arsenide (GaAlAs) laser irradiation (810 nm) was applied at days 1, 3, and 5 of differentiation process at energy densities of 3 or 6 J/cm(2) for BMSCs being induced to neurons, and 2 or 4 J/cm(2) for BMSCs being induced to osteoblasts. BMSCs proliferation was evaluated by MTT assay on the seventh day of differentiation. BMSCs differentiation to neurons was assessed by immunocytochemical analysis of neuron-specific enolase on the seventh day of differentiation. BMSCs differentiation to osteoblast was tested on the second, fifth, seventh, and tenth day of differentiation via analysis of alkaline phosphatase (ALP) activity. LLLI promoted BMSCs proliferation significantly at all energy densities except for 6 J/cm(2) in comparison to control groups on the seventh day of differentiation. LLLI at energy densities of 3 and 6 J/cm(2) dramatically facilitated the differentiation of BMSCs into neurons (p < 0.001). Also, ALP activity was significantly enhanced in irradiated BMSCs differentiated to osteoblast on the second, fifth, seventh, and tenth day of differentiation (p < 0.001 except for the second day). Using LLLI at 810 nm wavelength enhances BMSCs differentiation into neuron and osteoblast in the range of 2-6 J/cm(2), and at the same time increases BMSCs proliferation (except for 6 J/cm(2)). The effect of LLLI on differentiation and proliferation of BMSCs is dose-dependent. Considering these findings, LLLI could improve current in vitro methods of differentiating BMSCs prior to transplantation.

[Stimulation of mucoperiostal slice epithelization by small power laser after the primary plastic of oroantral communication]

INTRODUCTION

The oroantral communication is a pathologic communication between the oral cavity and maxillary sinus. It originates with extraction of the upper lateral teeth. Primary plastics communication, which is more extensive than 5 mm has been unsuccessful in 16%. Small power lasers have positive reaction on wounds healing. The aim of this work was to determine the lasers effects on slice epithelization after the plastics more extensive than 5 mm.

MATERIAL AND METHODS

The experimental research was done on dogs with extraction of the upper second premolars on both sides, and formed oroantral communication having diameter of 10 mm. After the plastics of sinus, the left side slices were exposed to radiation for 7 days, and the opposite slices healed spontaneously. Eight points (8x1J) were treated for 100s by GaAlAs laser, power 10 mW and wavelength 670 nm. Biopses of the slices connections were taken on the 14th day to be laboratory treated and examined microscopially. The study included 36 examinees with communication diameter of 10 mm and performed plastics of sinuses. In half of the examinees wounds were exposed to radiation for 7 days, and in other examinees they healed spontaneously. The results were analyzed on the fourteenth day according to the scale: (1) complete healing, without dehiscention; (2) incomplete healing, with minimal dehiscention; (3) communication did not heal, with partial dehiscention; (4) open communication, with significant dehiscention.

RESULTS AND DISCUSSION

The microscopic analysis shows that no wounds exposed to radiation were overcast with mucous membrane which had smooth sub epithelia chronic inflammation and inflammable infiltrate, and strong fibroplasias and granulations. Wounds exposed to radiation had mucous membrane without any signals of inflammation. Laser radiation causes anti-inflammatory reaction, i.e., it provokes reduction of exudation, alteration and proliferation, it blocks cyclo- and lipo-oxygenation by delaying the synthesis of prostaglandin, stimulates neutrophyll, macrophage and lissome activity and it activates the function of immune complex T and B lymphocytes, so this difference could be primary referred to the action of laser. Our clinical study shows that complete healing of oroantral communication was recorded in 88.8% of the examinees who were exposed to radiation in relation to 50%, of those who did not receive radiation therapy which is statistically much higher percentage (chi2 test < 0.05). The surgery was repeated in 5.6% of those who had received radiation therapy and in 16.7% of those who had not been exposed to radiation. Laser radiation stimulates changing of ADP in ATP and it accelerates cells metabolism, it increases microcirculation and accelerates substance exchange of cells, it increases DNK and RNK synthesis and stimulates cells division, which cause quicker regeneration of epithelia, i.e., it accelerates the process of wound healing.

CONCLUSION

It can be concluded that small power laser can be used successfully as additional method of treatment, after closing of oroantral communication surgically.

The effect of nanoparticle-enhanced photoacoustic stimulation on multipotent marrow stromal cells

In this article, we report a novel nanoparticle-enhanced biophysical technique that differentiates multipotent marrow stromal cells (MSCs) toward osteoblasts. We show that a brief (10 min) daily nanoparticle-facilitated exposure of MSCs to nanosecond pulse laser-induced photoacoustic (PA) stimulation enhances their differentiation toward osteoblasts. To observe osteodifferentiation under PA stimulation, tissue culture plates were seeded with MSCs without the osteogenic culture supplements (OS, 0.01 M beta-glycerophosphate, 50 mg/L ascorbic acid, 10(-8) M dexamethasone) in the presence and absence of single-walled carbon nanotubes (SWNTs) and gold nanoparticles (GNPs). The alkaline phosphatase activity, calcium content, and osteopontin secretion were monitored as indicators of MSCs' differentiation toward osteoblasts. The PA stimulated groups show up to 612% increase in calcium content compared to the controls cultured with osteogenic supplements (without PA stimulation) after 16 days. Among the PA stimulated groups, at day 16, MSCs incubated with SWNTs at 10 microg/mL concentrations showed up to 97% greater calcium content than those that did not contain SWNTs. The results demonstrated that PA stimulation not only promotes osteogenesis but also is synergistically enhanced by the presence of nanoparticles and, thus, has major implications for bone regeneration applications.

Low-energy laser irradiation promotes synovial fibroblast proliferation by modulating p15 subcellular localization

BACKGROUND AND OBJECTIVE

Low-energy laser irradiation (low-level laser therapy) (LELI/LLLT/photobiomodulation) has been found to modulate various biological effects, especially those involved in promoting cell proliferation. Synovial fibroblasts are important in maintaining the homeostasis of articular joints and have strong chondrogenetic capacity. Here, we investigated the effect and molecular basis of LELI on synovial fibroblast proliferation.

STUDY DESIGN/MATERIALS AND METHODS

HIG-82 rabbit synovial fibroblasts were cultured, and laser irradiation (660 nm) was applied at the power density of 40 mW/cm(2) for 2 minutes, corresponding to laser fluence of 4.8 J/cm(2). The effect of LELI on cell proliferation, cell cycle progression, and expression of cyclin-dependent kinase inhibitors (CKIs) were investigated. We also examined whether the effects of LELI on HIG-82 cell proliferation were affected by cAMP content, which is known to influence the cell cycle via inducing CKIs.

RESULTS

LELI promoted HIG-82 synovial fibroblast proliferation and induced cytoplasmic localization of cyclin-dependent kinase inhibitor p15 (INK4B/CDKN2B). Moreover, the proliferation of HIG-82 synovial fibroblasts was reduced by cAMP, while cAMP inhibitor, SQ22536, induced p15 cytoplasmic localization and as a result, elevated synovial fibroblast proliferation was observed. In addition, the promotive effect of LELI-induced HIG-82 synovial fibroblast proliferation was abolished by cAMP treatment. Our findings suggest that cAMP may be involved in the effect of LELI on synovial fibroblast proliferation.

CONCLUSION

We revealed the effect and molecular link involved in synovial fibroblast proliferation induced by 660-nm LELI. Our study provides new insights into the mechanisms by which LELI has biological effects on synovial fibroblast proliferation. These insights may contribute to further investigation on biological effects and application of LELI in regenerative medicine.

Effects of low-level laser therapy on proliferation and differentiation of murine bone marrow cells into osteoblasts and osteoclasts

BACKGROUND AND OBJECTIVE

Low-Level Laser Therapy (LLLT) has been suggested to improve bone tissue healing. The cellular and molecular mechanisms involved in this effect are still unclear but bone cell proliferation and differentiation alteration have been proposed. The aim of the present study was to investigate, in vitro, the effect of LLLT on bone cell proliferation, osteoblastic and osteoclastic differentiation, both involved in bone remodeling and regeneration.

STUDY DESIGN/MATERIALS AND METHODS

Murine bone marrow cells, which contain both osteoblast and osteoclast progenitors, were cultured and induced to differentiate in the absence or in the presence of LLLT. Laser exposition parameters were determined using a powermeter and consisted in an 808 nm infrared wavelength laser light in continuous mode, with an energy density of 4 J/cm(2) administered three times a week. Cell proliferation and differentiation were assessed after specific staining and microscopic analysis of the cultures after various times, as well as by quantitative RT-PCR analysis of a panel of osteoblast and osteoclast markers after nucleic acid extraction.

RESULTS

The use of a powermeter revealed that the power emitted by the optical fiber of the laser device was markedly reduced compared to the displayed power. This allowed to adjust the LLLT parameters to a final energy density exposure of 4 J/cm(2). In these conditions, proliferation of bone marrow mesenchymal stem cells as well as osteoclast or osteoblast differentiation of the corresponding progenitors were found similar in control and LLLT conditions.

CONCLUSION

Using the present experimental protocol, we concluded that an 808 nm wavelength infrared LLLT does not alter murine bone progenitor cell proliferation and differentiation. Moreover our results confirm the necessary use of a powermeter to fix LLLT protocol parameters.

In vitro effects of low-level laser irradiation for bone marrow mesenchymal stem cells: proliferation, growth factors secretion and myogenic differentiation

BACKGROUND AND OBJECTIVES

Bone marrow derived mesenchymal stem cells (BMSCs) have shown to be an appealing source for cell therapy and tissue engineering. Previous studies have confirmed that the application of low-level laser irradiation (LLLI) could affect the cellular process. However, little is known about the effects of LLLI on BMSCs. The aim of this study was designed to investigate the influence of LLLI at different energy densities on BMSCs proliferation, secretion and myogenic differentiation.

STUDY DESIGN/MATERIALS AND METHODS

BMSCs were harvested from rat fresh bone marrow and exposed to a 635 nm diode laser (60 mW; 0, 0.5, 1.0, 2.0, or 5.0 J/cm(2)). The lactate dehydrogenase (LDH) release was used to assess the cytotoxicity of LLLI at different energy densities. Cell proliferation was evaluated by using 3-(4, 5-dimethylithiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) and 5-bromo-2'-deoxyuridine (BrdU) assay. Production of vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) were measured by enzyme-linked immunosorbent assay (ELISA). Myogenic differentiation, induced by 5-azacytidine (5-aza), was assessed by using immunocytochemical staining for the expression of sarcomeric alpha-actin and desmin.

RESULTS

Cytotoxicity assay showed no significant difference between the non-irradiated group and irradiated groups. LLLI significantly stimulated BMSCs proliferation and 0.5 J/cm(2) was found to be an optimal energy density. VEGF and NGF were identified and LLLI at 5.0 J/cm(2) significantly stimulated the secretion. After 5-aza induction, myogenic differentiation was observed in all groups and LLLI at 5.0 J/cm(2) dramatically facilitated the differentiation.

CONCLUSIONS

LLLI stimulates proliferation, increases growth factors secretion and facilitates myogenic differentiation of BMSCs. Therefore, LLLI may provide a novel approach for the preconditioning of BMSCs in vitro prior to transplantation.

Osteonecrosis of the jaws caused by bisphosphonates: evaluation of a new therapeutic approach using the Er:YAG laser

A series of 49 patients diagnosed with osteonecrosis and all treated with latest-generation bisphosphonates was reviewed retrospectively to evaluate the use of erbium-doped: yttrium, aluminum, and garnet laser (Er:YAG) in terms of clinical outcome, and examine current trends from the clinical-therapeutic standpoint. Pathology reports on specimens submitted over the previous 7 years from either the mandible or the maxilla were reviewed; 49 patients were identified as having osteonecrosis of the jaws. For each of these cases, the medical history and profile were evaluated; 19 were treated with conservative therapy, 20 with radical surgery, and 10 with Er:YAG laser (2,940 nm). Of the 20 patients treated surgically (bone baquette, curettage, sequestrectomy of the necrotic bone), some required re-treatment, which resulted in bone fracturing. None of the patients were treated successfully. The 19 cases treated conservatively produced an improvement in symptoms, but not remission of the lesions. Of the ten patients treated with Er:YAG laser, six achieved total remission of signs and symptoms, four an improvement, and re-treatment was required in one case. Our present approach is to recommend intensive prophylactic care before the administration of bisphosphonates, and great caution is advised even in simple maneuvers like curettage, because this may exacerbate the avascular process. The use of Er:YAG laser appears to be promising (within the limits of our experience). It can be concluded that at 1 year of laser surgery, the treatment led to significant improvements in clinical parameters, and may represent a valid alternative, although studies on a larger scale are needed.

Initial effects of low-level laser therapy on growth and differentiation of human osteoblast-like cells

Low-level laser therapy is a clinically well established tool for enhancement of wound healing. In vitro studies have also shown that low level laser therapy has a biostimulatory effect on cells of different origin. The aim of this in vitro study was to investigate the initial effect of low-level laser therapy on growth and differentiation of human osteoblast-like cells. SaOS-2 cells were irradiated with laser doses of 1 J/cm2 and 2 J/cm2 using a diode laser with 670 nm wave length and an output power of 400 mW. Untreated cells were used as controls. At 24 h, 48 h and 72 h post irradiation, cells were collected and assayed for viability of attached cells and alkaline phosphatase specific activity. In addition, mRNA expression levels of osteopontin and collagen type I were assessed using semi-quantitative RT-PCR. Over the observation period, cell viability, alkaline phosphatase activity and the expression of osteopontin and collagen type I mRNA were slightly enhanced in cells irradiated with 1 J/cm2 compared with untreated control cells. Increasing the laser dose to 2 J/cm2 reduced cell viability during the first 48 h and resulted in persistently lower alkaline phosphatase activity compared with the other two groups. The expression of osteopontin and collagen type I mRNA slightly decreased with time in untreated controls and cells irradiated with 1 J/cm2, but their expression was increased by treatment with 2 J/cm2 after 72 h. These results indicate that low-level laser therapy has a biostimulatory effect on human osteoblast-like cells during the first 72 h after irradiation. Further studies are needed to determine the potential of low-level laser therapy as new treatment concept in bone regeneration.

Nd:YAG laser biostimulation in the treatment of bisphosphonate-associated osteonecrosis of the jaw: clinical experience in 28 cases

OBJECTIVE

To research an efficient treatment for the management of bisphosphonate-associated osteonecrosis.

BACKGROUND DATA

Necrosis of the jawbone has recently been described in association with systemic bisphosphonate therapy with drugs including zoledronic acid, pamidronate, and alendronate. The extent and clinical characteristics of bisphosphonate-associated osteonecrosis (BON) of the jaw are extremely variable, and range from the presence of fistulae in the oral mucosa or orofacial tissues, to large exposed areas of necrotic bone within the oral cavity. Clinical signs and symptoms commonly reported include pain, swelling, the presence of pus, loose teeth, ill-fitting dentures, and paresthesias of the inferior alveolar nerve when the necrosis affects the mandible. Fractures have also been reported. The treatment of BON of the jaw is still controversial since no therapy has proven to be efficacious as shown by the literature on the subject.

MATERIALS AND METHODS

In this study we report results achieved with 28 patients affected by BON of the jaw, who received treatment with the Nd:YAG laser alone or in combination with conventional medical or surgical treatment. Clinical variables such as severity of symptoms, presence of pus, and closure of mucosal flaps before and after therapy were evaluated to establish the effectiveness of laser irradiation. The 28 patients with BON were subdivided into four groups: eight patients were treated with medical therapy only (antibiotics with or without antimycotics and/or antiseptic rinses), six patients were treated with medical and surgical therapy (necrotic bone removal and bone curettage), six patients were treated with medical therapy associated with laser biostimulation, and eight patients were treated with medical therapy associated with both surgical therapy and laser biostimulation.

RESULTS

Of the 14 patients who underwent laser biostimulation, nine reported complete clinical success (no pain, symptoms of infection, or exposed bone or draining fistulas), and three improved their symptomatology only, with a follow-up of between 4 and 7 mo.

CONCLUSIONS

While the results reported in this study are not conclusive, they indicate that laser therapy has potential to improve management of BON.

Effects of low level red-light irradiation on the proliferation of mesenchymal stem cells derived from rat bone marrow

Mesenchymal stem cells (MSCs) are capable of regenerating various mesenchymal tissues and are essential in supporting the growth and differentiation of hematopoietic stem cells within the bone marrow microenvironment in vivo. To achieve clinically meaningful numbers of cells, many approaches have been used to maintain the differentiation potentialities and expand enough cells for clinical treatments. Previously, we have reported that low level light irradiation (LLLI) using 630 nm light emitting diodes (LEDs) could enhance replicative and colony formation potentials of MSCs derived from human bone marrow. The purpose was to study the effect on the proliferation of MSCs derived from the rat bone marrow by red light LLLI (630 nm) under different parameters of irradiation. The irradiance used was 5, 10 or 15 mW/cm2, and the radiant exposure was 2 or 4 J/cm2. Rat MSCs were irradiated at room temperature with single and multiple exposures. The results showed that the proliferation of MSCs plated at the low density (100 cells/well) and high density (1000 cells/well) was enhanced by multiple exposures of red-light LED treatment. The rate of proliferation of MSCs plated at the high density was not as high as those plated at the low density. The optimal parameter for LLLI was at irradiance of 15 mW/cm2, and radiant exposure of 4 J/cm2. The effect on the proliferation of cells by single dose irradiation was temporary. Multiple stimuli may be necessary for the enhancement of cell growth.

Effects of two types of low-level laser wave lengths (850 and 630 nm) on the orthodontic tooth movements in rabbits

The effects of low-level lasers on bone cellular activity, bone structures, bone healing, fibroblasts activity and inflammation process have already been investigated. Considering orthodontic tooth movement, which is a complicated inflammatory process involving simultaneous bone apposition and resorption, the aim of this controlled study is to investigate the quantitative effects of a pulsed 850 nm laser (Optodan) and a continuous 630 nm laser (KLO3) on the orthodontic tooth movement in rabbits. This experimental study was conducted on 18 male albino rabbits divided into three equal groups of control, Optodan and KLO3. In all the groups, NiTi-closed coil springs were used on the first mandibular molars with 4-oz tension. The control group was not irradiated by laser, but the teeth in the laser groups were irradiated 9 days according to the periodontal therapeutic protocols. After 16 days, samples were sacrificed. The distance between the distal surface of the first molar and the mesial surface of the second molar was measured with 0.05-mm accuracy. The data were subjected to the statistical tests of Kolmogrov Smirnov and variance analysis. The mean orthodontic tooth movements of the first mandibular molars were 1.7 +/- 0.16 mm in control group, 0.69 +/- 0.16 mm in Optodan group and 0.86 +/- 0.13 mm in KLO3 group. There were statistically significant difference between the control and the two other laser-irradiated groups (P < 0.001). The findings of the present study imply that the amounts of orthodontic tooth movement, after low-level laser therapy, are diminished. It could not be concluded that any low-level laser will reduce the speed of teeth movement in orthodontic treatments, and further studies with less or more energies may show different results.