In Vitro Effects

Lasers Med Sci. 2011 Jan 28. [Epub ahead of print]

Low-level laser therapy: a useful technique for enhancing the proliferation of various cultured cells.

Alghamdi KM, Kumar A, Moussa NA.

Department of Dermatology, Vitiligo Research Chair, College of Medicine, King Saud University, PO Box 240997, Riyadh, 11322, Saudi Arabia, kmgderm@yahoo.com.

Abstract

The aim of this work is to review the available literature on the details of low-level laser therapy (LLLT) use for the enhancement of the proliferation of various cultured cell lines including stem cells. A cell culture is one of the most useful techniques in science, particularly in the production of viral vaccines and hybrid cell lines. However, the growth rate of some of the much-needed mammalian cells is slow. LLLT can enhance the proliferation rate of various cell lines. Literature review from 1923 to 2010. By investigating the outcome of LLLT on cell cultures, many articles report that it produces higher rates of ATP, RNA, and DNA synthesis in stem cells and other cell lines. Thus, LLLT improves the proliferation of the cells without causing any cytotoxic effects. Mainly, helium neon and gallium-aluminum-arsenide (Ga-Al-As) lasers are used for LLLT on cultured cells. The results of LLLT also vary according to the applied energy density and wavelengths to which the target cells are subjected. This review suggests that an energy density value of 0.5 to 4.0 J/cm(2) and a visible spectrum ranging from 600 to 700 nm of LLLT are very helpful in enhancing the proliferation rate of various cell lines. With the appropriate use of LLLT, the proliferation rate of cultured cells, including stem cells, can be increased, which would be very useful in tissue engineering and regenerative medicine.

Photomed Laser Surg.  2010 Aug;28 Suppl 1:S3-40.

Laser photobiomodulation of proliferation of cells in culture: a review of human and animal studies.

Peplow PV, Chung TY, Baxter GD.

Department of Anatomy & Structural Biology, University of Otago, Dunedin, New Zealand. phil.peplow@stonebow.otago.ac.nz

Abstract

AIM: The aim of this article was to review experimental studies of laser irradiation of human and animal cells in culture to assess the photobiomodulatory effects of such irradiation.

BACKGROUND: Previous studies have shown that various types of cells respond differently to laser irradiation, depending on irradiation parameters. Cellular outcomes measured or examined include cell numbers, cell viability, and ultrastructural features. A review of these studies may provide a further insight into the clinical effects brought about by laser light on cells and tissues, including laser effects in wound healing and repair of nerves and skeletal muscle after injury.

METHODS: A systematic review was completed of original research articles investigating the effects of laser therapy on human and animal cells in culture (January 2002 to September 2009). Relevant articles were primarily sourced from PubMed and Medline by using EndNote X1, and from secondary searches. Search terms were “cell proliferation,” “laser therapy,” “laser irradiation,” “laser phototherapy,” and “phototherapy.”

RESULTS: In total, 46 relevant articles were included in the review, comprising work completed on a variety of cell types. Although results consistently demonstrated the potential of laser irradiation to affect cellular proliferation in a wavelength- and dosage-dependent manner, the relevance of other key irradiation parameters, such as irradiance, to such effects remained unclear.

CONCLUSIONS: Findings from studies of cells in culture clearly demonstrate the ability of laser irradiation to modulate (typically stimulate) cellular proliferation. The relevance of some irradiation parameters remains occult and represents an important area for further research.

J Clin Laser Med Surg. 2003 Aug;21(4):193-6.

Laser light prevents apoptosis in Cho K-1 cell line.

Carnevalli CM, Soares CP, Zangaro RA, Pinheiro AL, Silva NS.

Institute for Research and Development, Univap, Sao Jose dos Campos, Sao Paulo, Brazil.

OBJECTIVE: The present study investigated the effects of low-level laser therapy (LLLT) on the mitochondria, nucleus, and cytoskeleton of CHO K-1 cells by the use of specific fluorescent probes. BACKGROUND DATA: The use of LLLT has been recommended by several authors for acceleration of the healing process. The literature on the effects of LLLT in this process is highly contradictory because of difficulties in identifying its effects on cells. MATERIALS AND METHODS: CHO K-1 cells were cultivated using MEM containing 5% FBS and were irradiated or not with a semiconductor laser (lambda = 830 nm; phi approximately 0.8 mm; 10 mW; 2 J/cm2). The cells were incubated with specific fluorescent probes–0.1 microM for 30 min with 5,5′, 6,6′-tetrachloro-1, 1′,3,3′-tetraethyl-benzimidazol-carbocyanine iodide (JC-1) for the mitochondria; 5 mM for 5 min of 4′,6′-diamidino, 2′-phenylindole (DAPI)for the nucleus, and 0.1 M of 1:100 PHEM of rhodamine-phalloidin during 1 h for the cytoskeleton–and were analyzed by epifluorescence. RESULTS: Positive biomodulatory effects were observed on irradiated cells compared to their controls as seen on JC-1, DAPI, and rhodamine-phalloidin labeling. Irradiated cells showed an increased level of cellular division, as evidenced by analyzing the intermediary filaments of the cytoskeleton and the chromosomes. Another important observation was that cells maintained under the condition of nutritional deficiency had both membrane and genetic material that was more preserved in comparison to the controls, in which the presence of an apoptotic nucleus could be observed in some cells. CONCLUSION: The results of the present study demonstrate that LLLT, in addition to providing positive biomodulation, acts in the re-establishment of cellular homeostasis when the cells are maintained under the condition of nutritional stress; it also prevents apoptosis in CHO K-1 cells.

Lasers Surg Med. 2005 Jan;36(1):8-12.

Effect of wavelength on low-intensity laser irradiation-stimulated cell proliferation in vitro.

Moore P, Ridgway TD, Higbee RG, Howard EW, Lucroy MD.

University of Oklahoma College of Dentistry, Oklahoma City, Oklahoma 73104, USA.

Abstract

BACKGROUND AND OBJECTIVES: There exist contradictory reports about low-intensity laser light-stimulated cell proliferation. The purpose of this study was to determine the effect of wavelength on proliferation of cultured murine cells.

STUDY DESIGN/MATERIALS AND METHODS: Proliferation of primary cell cultures was measured after irradiation with varying laser wavelengths.

RESULTS: Fibroblasts proliferated faster than endothelial cells in response to laser irradiation. Maximum cell proliferation occurred with 665 and 675 nm light, whereas 810 nm light was inhibitory to fibroblasts.

CONCLUSIONS: These observations suggest that both wavelength and cell type influence the cell proliferation response to low-intensity laser irradiation.

PMID: 15662631 [PubMed – indexed for

J Formos Med Assoc. 2003 Jul;102(7):486-91.

Effects of infrared and low-power laser irradiation on cell viability, glutathione and glutathione-related enzymen activities in primary rat hepatocytes

Kao MJ, Sheen LY.

Department of Physical Medicine and Rehabilitation, China Medical College Hospital, Taichung, Taiwan.

BACKGROUND AND PURPOSE: Both infrared and low-power laser have been applied to improve circulation, wound repair, and pain control. Infrared and low-power laser therapies have the potential for stimulating enzyme activities which might contribute to increased glutathione (GSH) concentration and provide protection against oxidative damage. This study investigated cell viability, and GSH and its related enzyme activities in rat hepatocytes after irradiation. METHODS: Hepatocytes were isolated from 8-week-old male Sprague-Dawley rats and the cultures were divided into infrared, laser, and control groups. The cells were treated with infrared and low-power laser at a distance of 35 cm for 20 minutes. The cell morphology, lactate dehydrogenase (LDH) leakage, lipid peroxidation, GSH concentration, GSH peroxidase, GSH reductase (GRd), and GSH S-transferase activities were measured after irradiation. RESULTS: The morphology and LDH leakage of hepatocytes in the irradiation groups did not differ significantly from those of the control group. After infrared irradiation, a significant decrease in thiobarbituric acid-reactive substances and an increase in GSH concentration were found after 48 hours of incubation compared to the control group (p < 0.05). Furthermore, laser irradiation resulted in a significant increase in GRd activity after 48 hours of incubation compared to the control group (p < 0.05). A 48-hour incubation period produced greater GRd activity in all groups compared to a 24-hour period (p < 0.05). CONCLUSIONS: Irradiation did not damage rat hepatocytes in this study. Infrared was shown to stimulate GSH production, while laser irradiation increased GRd activity.

Lasers Med Sci. 2003;18(2):100-3.

Low-level 809 nm GaAlAs laser irradiation increases the proliferation of human laryngeal carcinoma cells in vitro.

Kreisler M, Christoffers AB, Willershausen B, d’Hoedt B.

Poliklinik fur Zahnarztliche Chirurgie, Johannes Gutenberg-University, Mainz, Germany. matthiaskreisler@web.de

The aim of the study was to investigate the effect of low-level 809 nm laser irradiation on the proliferation rate of human larynx carcinoma cells in vitro. Epithelial tumor cells were obtained from a laryngeal carcinoma and cultured under standard conditions. For laser treatment the cells were spread on 96-well tissue culture plates. Sixty-six cell cultures were irradiated with an 809 nm GaAlAs laser. Another 66 served as controls. Power output was 10 mW(cw) and the time of exposure 75-300 s per well, corresponding to an energy fluence of 1.96-7.84 J/cm2. Subsequent to laser treatment, the cultures were incubated for 72 h. The proliferation rate was determined by means of fluorescence activity of a redox indicator (Alamar Blue Assay) added to the cultures immediately after the respective treatment. The indicator is reduced by metabolic activity related to cellular growth. Proliferation was determined up to 72 h after laser application. The irradiated cells revealed a considerably higher proliferation activity. The differences were highly significant up to 72 h after irradiation (Mann-Whitney U test, p < 0.001). A cellular responsiveness of human laryngeal carcinoma cells to low-level laser irradiation is obvious. The cell line is therefore suitable for basic research investigations concerning the biological mechanisms of LLLT on cells.

Lasers Med Sci. 2003;18(2):95-9.

Increased fibroblast proliferation induced by light emitting diode and low power laser irradiation.

Vinck EM, Cagnie BJ, Cornelissen MJ, Declercq HA, Cambier DC.

Department of Rehabilitation Sciences and Physiotherapy, Ghent University, 9000 Ghent, Belgium. elke.vinck@ugent.be

BACKGROUND AND OBJECTIVE: As Light Emitting Diode (LED) devices are commercially introduced as an alternative for Low Level Laser (LLL) Therapy, the ability of LED in influencing wound healing processes at cellular level was examined. STUDY DESIGN/MATERIALS AND METHODS: Cultured fibroblasts were treated in a controlled, randomized manner, during three consecutive days, either with an infrared LLL or with a LED light source emitting several wavelengths (950 nm, 660 nm and 570 nm) and respective power outputs. Treatment duration varied in relation to varying surface energy densities (radiant exposures). RESULTS: Statistical analysis revealed a higher rate of proliferation (p < 0.001) in all irradiated cultures in comparison with the controls. Green light yielded a significantly higher number of cells, than red (p < 0.001) and infrared LED light (p < 0.001) and than the cultures irradiated with the LLL (p < 0.001); the red probe provided a higher increase (p < 0.001) than the infrared LED probe and than the LLL source. CONCLUSION: LED and LLL irradiation resulted in an increased fibroblast proliferation in vitro. This study therefore postulates possible stimulatory effects on wound healing in vivo at the applied dosimetric parameters.

Lasers Med Sci. 2003;18(2):78-82.

Effect of low-level laser irradiation on osteoglycin gene expression in osteoblasts.

Hamajima S, Hiratsuka K, Kiyama-Kishikawa M, Tagawa T, Kawahara M, Ohta M, Sasahara H, Abiko Y.

Nihon University School of Dentistry at Matsudo, Chiba, Japan.

Many studies have attempted to elucidate the mechanism of the biostimulatory effects of low-level laser irradiation (LLLI), but the molecular basis of these effects remains obscure. We investigated the stimulatory effect of LLLI on bone formation during the early proliferation stage of cultured osteoblastic cells. A mouse calvaria-derived osteoblastic cell line, MC3T3-E1, was utilised to perform a cDNA microarray hybridisation to identify genes that induced expression by LLLI at the early stage. Among those genes that showed at least a twofold increased expression, the osteoglycin/mimecan gene was upregulated 2.3-fold at 2 h after LLLI. Osteoglycin is a small leucine-rich proteoglycan (SLRP) of the extracellular matrix which was previously called the osteoinductive factor. SLRP are abundantly contained in the bone matrix, cartilage cells and connective tissues, and are thought to regulate cell proliferation, differentiation and adhesion in close association with collagen and many other growth factors. We investigated the time-related expression of this gene by LLLI using a reverse transcription polymerase chain reaction (RT-PCR) method, and more precisely with a real-time PCR method, and found increases of 1.5-2-fold at 2-4 h after LLLI compared with the non-irradiated controls. These results suggest that the increased expression of the osteoglycin gene by LLLI in the early proliferation stage of cultured osteoblastic cells may play an important role in the stimulation of bone formation in concert with matrix proteins and growth factors.

J Clin Laser Med Surg. 2003 Jun;21(3):165-70.

Low-level laser irradiation attenuates production of reactive oxygen species by human neutrophils.

Fujimaki Y, Shimoyama T, Liu Q, Umeda T, Nakaji S, Sugawara K.

Department of Hygiene, Hirosaki University School of Medicine, Japan.

OBJECTIVE: The aim of this study was to examine the effects of low-level laser therapy (LLLT) on production of reactive oxygen (ROS) species by human neutrophils. BACKGROUND DATA: LLLT is an effective therapeutic modality for inflammatory conditions. MATERIALS AND METHODS: The laser device used was the infrared diode laser (GaAlAs), 830-nm continuous wave (150 mW/cm(2)). After irradiation, ROS production by neutrophils was measured using luminol-dependent chemiluminescence (LmCL) and expression of CD11b and CD16 on neutrophil surface was measured by flow cytometry. RESULTS: The LmCL response of neutrophils was reduced by laser irradiation at 60 min prior to the stimulation with opsonized zymosan and calcium ionophore. The attenuating effect of LLLT was larger in neutrophils of smokers than non-smokers, while the amount of produced ROS was larger in neutrophils of smokers. Expression of CD11b and CD16 on neutrophil surface was not affected by LLLT. CONCLUSION: Attenuation of ROS production by neutrophils may play a role in the effects of LLLT in the treatment of inflammatory tissues. There is a possible usage of LLLT to improve wound healing in smokers.

J Clin Periodontol. 2003 Apr;30(4):353-8.

Effect of low-level GaAlAs laser irradiation on the proliferation rate of human periodontal ligament fibroblasts: an in vitro study.

Kreisler M, Christoffers AB, Willershausen B, d’Hoedt B.

Department of Oral Surgery, Johannes Gutenberg-University, Augustusplatz 2, 55131 Mainz, Germany. matthiaskreisler@web.de

AIM: The aim of this in vitro study was to evaluate a potential stimulatory effect of low-level laser irradiation on the proliferation of human periodontal ligament fibroblasts (PDLF). MATERIALS AND METHODS: PDLF obtained from third molar periodontal ligaments were cultured under standard conditions and spread on 96-well tissue culture plates. Subconfluent monolayers were irradiated with an 809-nm diode laser operated at a power output of 10 mW in the continuous wave (cw) mode at energy fluences of 1.96-7.84 Jcm-2. The variable irradiation parameters were the time of exposure (75-300 s per well) and the number of irradiations (1-3). After laser treatment, the cultures were incubated for 24 h. The proliferation rate of the lased and control cultures was determined by means of fluorescence activity of a reduction-oxidation (REDOX) indicator (Alamar Blue Assay) added to the cell culture. Proliferation, expressed in relative fluorescence units (RFU), was determined 24, 48 and 72 h after irradiation. RESULTS: The irradiated cells revealed a considerably higher proliferation activity than the controls. The differences were significant up to 72 h after irradiation (Mann-Whitney U-test, p<0.05). CONCLUSION: A cellular effect of the soft laser application is clearly discernible. Clinical studies are needed to evaluate whether the application of low-level laser therapy might be beneficial in regenerative periodontal therapy.

J Clin Laser Med Surg. 2000 Jun;18(3):145-50.

Effect of He-Ne laser (632.8 nm) and Polygen on CHO cells.

Al-Watban FA, Andres BL.

Biological and Medical Research Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Kingdom of Saudi Arabia. watban@kfshrc.edu.sa

OBJECTIVE: We determined the effect of He-Ne laser biostimulation in combination with Polygen (PG) on Chinese hamster ovary (CHO) cells. BACKGROUND DATA: Several studies have shown that He-Ne laser (632.8 nm), growth factors, and growth hormone can enhance cellular proliferation and that the use of low-level laser stimulation combined with growth factor stimulation has scientific support. PG, an animal protein extract containing a blend of growth factors and growth hormone, was used together with a He-Ne laser to determine their efficacy in the enhancement of cellular proliferation. METHODS: The dose-response curves for the colony-forming ability of CHO cells in 5% FCS-MEM with 6-125 microg/ml PG and He-Ne laser with an optimum power density of 1.25 mW/cm2 and cumulative doses of 60-600 mJ/cm2 was given for 3 consecutive days. The combined effects of He-Ne laser 180 mJ/cm2 with 6 and 12 microg/ml PG were determined. Quadruplicate cultures were performed. The student’s t-test was used to ascertain differences of treated groups from controls. RESULTS: The mean number of colonies (MNC) was increased using 180 mJ/cm2 laser by 13.2% (p < 0.01); 6 and 12 microg/ml PG by 19.2% (p < 0.0025) and 13.2% (p = 0.01); laser + PG 6 microg/ml by 23.2% (p < 0.001) and laser + PG 12 microg/ml by 20.5% (p < 0.001). An additional significant increase of 8.8% (p < 0.05) and an insignificant 6.4% (p = 0.086) by laser + PG 6 microg/ml and laser + PG 12 microg/ml were observed, respectively, when compared to the solitary effect of laser. CONCLUSIONS: Results suggest that the He:Ne laser or PG can stimulate CHO cell proliferation and that further stimulation can be achieved by using the He:Ne laser and PG simultaneously. This combination could be useful as a new treatment modality.

Clin Orthod Res. 2001 Feb;4(1):3-14.

The effects of low level laser irradiation on osteoblastic cells.

Coombe AR, Ho CT, Darendeliler MA, Hunter N, Philips JR, Chapple CC, Yum LW.

Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, New South Wales, Australia; Institute of Dental Research, United Dental Hospital, New South Wales, Australia.

Low level laser therapy has been used in treating many conditions with reports of multiple clinical effects including promotion of healing of both hard and soft tissue lesions. Low level laser therapy as a treatment modality remains controversial, however. The effects of wavelength, beam type, energy output, energy level, energy intensity, and exposure regime of low level laser therapy remain unexplained. Moreover, no specific therapeutic window for dosimetry and mechanism of action has been determined at the level of individual cell types. The aim of this study was to investigate the effects of low level laser irradiation on the human osteosarcoma cell line, SAOS-2. The cells were irradiated as a single or daily dose for up to 10 days with a GaAlAs continuous wave diode laser (830 nm, net output of 90 mW, energy levels of 0.3, 0.5, 1, 2, and 4 Joules). Cell viability was not affected by laser irradiation, with the viability being greater than 90% for all experimental groups. Cellular proliferation or activation was not found to be significantly affected by any of the energy levels and varying exposure regimes investigated. Low level laser irradiation did result in a heat shock response at an energy level of 2 J. No significant early or late effects of laser irradiation on protein expression and alkaline phosphatase activity were found. Investigation of intracellular calcium concentration revealed a tendency of a transient positive change after irradiation. Low level laser irradiation was unable to stimulate the osteosarcoma cells utilised for this research at a gross cell population level. The heat shock response and increased intracellular calcium indicate that the cells do respond to low level laser irradiation. Further research is required, utilising different cell and animal models, to more specifically determine the effects of low level laser irradiation at a cellular level. These effects should be more thoroughly investigated before low level laser therapy can be considered as a potential accelerator stimulus for orthodontic tooth movement.

Biull Eksp Biol Med. 1993 Aug;116(8):149-51.

The effect of the blood serum from patients subjected to intravenous laser therapy on the parameters of synaptic transmission

[Article in Russian]

Azbel’ DI, Egorushkina NV, Kuznetsova IIu, Ratushniak AS, Shergin SM, Shurgaia AM, Shtark MB.

The effect of serum of patients with myocardial ischemia after low-level laser therapy on parameters of synaptic conductance of rat hippocampal neurons was investigated. The serum from patients with an initially low level of neuronal activity obtained after determination of laser irradiation increased the amplitude and that from patients with high activity. Thus the process of normalization of these parameters was observed. Our results may help to optimize the course of medical treatment, and subsequently give an insight to understanding of the mechanism of therapeutic effect of laser irradiation.

J Photochem Photobiol B. 1992 Feb 28;12(3):305-10.

Effects of visible and near-infrared lasers on cell cultures.

Lubart R, Wollman Y, Friedmann H, Rochkind S, Laulicht I.

Department of Physics, Bar-Ilan University, Ramat Gan, Israel.

The effect of 360, 632 and 780 nm light on NIH fibroblast cells was examined. Mitosis counts of irradiated cells at various energy doses were taken. Scanning electron micrographs of these cells were studied. It is suggested that low-level laser therapy in the visible and in the near-infrared region is due to cell respiration stimulation by either the endogenous porphyrins in the cell, or by the cytochromes.

J Clin Laser Med Surg. 2003 Dec;21(6):351-5.

Low-intensity near-infrared laser radiation-induced changes of acetylcholinesterase activity of human erythrocytes.

Kujawa J, Zavodnik L, Zavodnik I, Bryszewska M.

Department of Rehabilitation, Medical University of Lodz, Lodz, Poland. jkujawa@box43.gnet.pl

OBJECTIVE: The aim of the present study was to investigate the transformations of red blood cells produced by low-intensity infrared laser radiation (810 nm). BACKGROUND DATA: Low-intensity (the output power of a laser device in the milliwatt range) laser radiation as a local phototherapeutic modality is characterized by its ability to induce non-thermic, nondestructive photobiological processes in cells and tissues. However, the exact theory concerning the therapeutic effects of laser biostimulation has not been developed. MATERIALS AND METHODS: The suspensions of human erythrocytes in PBS (10% hematocrit) were irradiated with near-infrared (810 nm) therapy laser at different light doses (0-20 J) and light power (fluence rate; 200 or 400 mW) at 37 degrees C. As the parameters characterizing the cell structural and functional changes membrane acetylcholinesterase (AchEase) activity, the membrane potential, the level of intracellular glutathione, the level of products of membrane lipid peroxidation, and the cell osmotic stability were measured. RESULTS: It was found that near-infrared low-intensity laser radiation produced complex biphasic dose-dependent changes of the parameters of AchEase reaction in the dose-dependent manner: at smaller doses of radiation (6 J) the maximal reaction rate and Michaelis-Menten constant value decreased, and at higher radiation doses these parameters increased. No significant changes of erythrocyte stability, cellular redox state (reduced glutathione or lipid peroxidation product levels), or cell membrane electrochemical potential were observed. CONCLUSION: Low-intensity near-infrared laser radiation (810 mn) produced AchEase activity changes, reflecting the effect of light on the enzyme due to energy absorption. Protein molecule conformational transitions and enzyme activity modifications in cells have been suggested as laser radiation-induced events.

J Formos Med Assoc. 2003 Jul;102(7):486-91.

Effects of infrared and low-power laser irradiation on cell viability, glutathione and glutathione-related enzyme activities in primary rat hepatocytes

Kao MJ, Sheen LY.

Department of Physical Medicine and Rehabilitation, China Medical College Hospital, Taichung, Taiwan.

BACKGROUND AND PURPOSE: Both infrared and low-power laser have been applied to improve circulation, wound repair, and pain control. Infrared and low-power laser therapies have the potential for stimulating enzyme activities which might contribute to increased glutathione (GSH) concentration and provide protection against oxidative damage. This study investigated cell viability, and GSH and its related enzyme activities in rat hepatocytes after irradiation. METHODS: Hepatocytes were isolated from 8-week-old male Sprague-Dawley rats and the cultures were divided into infrared, laser, and control groups. The cells were treated with infrared and low-power laser at a distance of 35 cm for 20 minutes. The cell morphology, lactate dehydrogenase (LDH) leakage, lipid peroxidation, GSH concentration, GSH peroxidase, GSH reductase (GRd), and GSH S-transferase activities were measured after irradiation. RESULTS: The morphology and LDH leakage of hepatocytes in the irradiation groups did not differ significantly from those of the control group. After infrared irradiation, a significant decrease in thiobarbituric acid-reactive substances and an increase in GSH concentration were found after 48 hours of incubation compared to the control group (p < 0.05). Furthermore, laser irradiation resulted in a significant increase in GRd activity after 48 hours of incubation compared to the control group (p < 0.05). A 48-hour incubation period produced greater GRd activity in all groups compared to a 24-hour period (p < 0.05). CONCLUSIONS: Irradiation did not damage rat hepatocytes in this study. Infrared was shown to stimulate GSH production, while laser irradiation increased GRd activity.

Artificial Cells, Blood Substitutes, and Immobilization Biotechnology. 2000; 28(2):193-201

Biostimulation of human chondrocytes with Ga-Al-As laser: ‘In vitro’ research.

Morrone G, Guzzardella G A, Tigani D et al.

The aim of the study was to verify the effects of lllt performed with GaAlAs (780 nm, 2500 mW) on human cartilage cells in vitro. The cartilage sample used for the biostimulation treatment was taken from the fight knee of a 19-year-old patient. After the chondrocytes were isolated and suspended for cultivation, the cultures were incubated for 10 days. The culture were divided into four groups. Groups I, II, III were subject to biostimulation with the following laser parameters: 300J, 1W, 100Hz,10 min. exposure, pulsating emission; 300J, 1W, 300Hz, 10 min. exposure, pulsating emission; and 300J, 1W, 500Hz, 10 min. exposure, pulsating emission, respectively. Group IV did not receive any treatment. The laser biostimulation was conducted for five consecutive days. The data showed good results in terms of cell viability and levels of Ca and Alkaline Phosphate in the groups treated with laser compared to the untreated group. The results obtained confirm our previous positive in vitro results that the GaAlAs Laser provides biostimulation without cell damage.