Ultrastructural morphometry of membrane-bound intracytoplasmic collagen fibrils in tendon fibroblasts exposed to He:Ne laser beam

Erbium: Yttrium Aluminum Garnet Laser Accelerates Healing in Indolent Diabetic Foot Ulcers

The objective of the study was to evaluate the effect of the erbium:yttrium aluminum garnet (YAG) laser on diabetic foot ulcers (DFUs) that had not responded to standard care. We retrospectively evaluated 22 nonhealing DFUs that received at least 4 weeks of standard wound care, demonstrated poor healing response, and subsequently were treated with an erbium:YAG laser. We measured the percent wound area reduction (PWAR) for the 4 weeks before initiating laser therapy and the PWAR for 4 weeks after the initiation of laser therapy. Erbium:YAG laser treatment consisted of 2 components: debridement and resurfacing. The laser settings were the same for all treatments. We used the paired t test to compare pretreatment with posttreatment wound area reduction. During the 4-week period before the initiation of laser therapy, the average PWAR was -33.6%. Four weeks after initiating treatment with the erbium:YAG laser, the average PWAR was 63.4% (p = .002) and 72.7% of wounds had ≥50% PWAR. By 12 weeks, 50% of wounds had healed. Erbium:YAG laser therapy accelerated DFU healing in a cohort of patients with ulcers that had been unresponsive to standard of care therapy.

Evaluating the effect of low-level laser therapy on healing of tentomized Achilles tendon in streptozotocin-induced diabetic rats by light microscopical and gene expression examinations

Tendon healing is impaired in individuals diagnosed with diabetes mellitus (DM). According to research, there is considerable improvement in the healing of surgically tenotomized Achilles tendons following low-level laser therapy (LLLT) in non-diabetic, healthy animals. This study uses light microscopic (LM) and semi-quantitative reverse transcription PCR (RT-PCR) analyses to evaluate the ability of LLLT in healing Achilles tendons from streptozotocin-induced diabetic (STZ-D) rats. A total of 88 rats were randomly divided into two groups, non-diabetic and diabetic. DM was induced in the rats by injections of STZ. The right Achilles tendons of all rats were tenotomized 1 month after administration of STZ. Laser-treated rats were treated with a helium-neon (He-Ne) laser that had a 632.8-nm wavelength and 7.2-mW average power. Experimental group rats received a daily dose of 0.014 J (energy density, 2.9 J/cm(2)). Control rats did not receive LLLT. Animals were sacrificed on days 5, 10, and 15 post-operatively for semi-quantitative LM and semi-quantitative RT-PCR examinations of transforming growth factor-beta1 (TGF-β1) gene expression. The chi-square test showed that LLLT significantly reduced inflammation in non-diabetic rats compared with their non-diabetic controls (p = 0.02). LLLT significantly decreased inflammation in diabetic rats on days 5 (p = 0.03) and 10 (p = 0.02) compared to the corresponding control diabetic rats. According to the student's t test, LLLT significantly increased TGF-β1 gene expression in healthy (p = 0.000) and diabetic (p = 0.000) rats compared to their relevant controls. The He-Ne laser was effective in altering the inflammatory reaction and increasing TGF-β1 gene production.

Effect of low-level laser therapy on healing of tenotomized Achilles tendon in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) is associated with musculoskeletal damage. Investigations have indicated that healing of the surgically tenotomized Achilles tendon was considerably augmented following low-level laser therapy (LLLT) in non-diabetic, healthy animals. The aim of the present study was to evaluate the effect of LLLT on the Achilles tendon healing in streptozotocin-induced diabetic (STZ-D) rats via a biomechanical evaluating method. Thirty-three rats were divided into non-diabetic (n = 18) and diabetic (n = 15) groups. DM was induced in the rats by injections of STZ. The right Achilles tendons of all rats were tenotomized 1 month after STZ injections. The two experimental groups (n = 6 for each group) of non-diabetic rats were irradiated with a helium-neon (He-Ne) laser at 2.9 and 11.5 J/cm(2) for ten consecutive days. The two experimental groups of diabetic rats (n = 5 for each group) were irradiated with a He-Ne laser at 2.9 and 4.3 J/cm(2) for ten consecutive days. The tendons were submitted to a tensiometric test. Significant improvements in the maximum stress (MS) values (Newton per square millimeter) were found following LLLT at 2.9 J/cm(2) in both the non-diabetic (p = 0.031) and diabetic (p = 0.019) experimental groups when compared with their control groups. LLLT at 2.9 J/cm(2) to the tenotomized Achilles tendons in the non-diabetic and diabetic rats significantly increased the strength and MS of repairing Achilles tendons in our study.

Low-level laser therapy promotes vascular endothelial growth factor receptor-1 expression in endothelial and nonendothelial cells of mice gastrocnemius exposed to snake venom

Crotalinae snake venoms cause severe local myonecrosis and microvasculature failure at the bite site. We evaluated whether low-level laser therapy (LLLT) could accelerate angiogenesis and myoregeneration in male Swiss mice injected with Bothrops moojeni venom through immunohistochemistry of the vascular endothelial growth factor receptor-1 (VEGFR-1). Envenomed gastrocnemius was either unirradiated (V) or irradiated with HeNe (VHN, 632.8 nm) or GaAs (VGA, 904 nm, 10000 Hz). Animals sacrificed at 3 and 12 h were irradiated once (4 J cm(-2)), at 24 h (twice) and at 3, 7, 21 days (4, 8, 22 times, respectively). At 3 days, LLLT increased angiogenesis (80%:HeNe vs 40%:GaAs), decreased neutrophils and increased proliferation of regenerating cells. However, after 21 days, myoregeneration observed in the VHN group appeared delayed compared with the V group. As LLLT improved revascularization, the suggestive delay in myoregeneration could be a dose-response inhibitory effect caused by multiple irradiations in myogenesis. The immunodetection of VEGFR-1 in neutrophils, macrophages, satellite cells, fibroblasts, Schwann cells and skeletal and smooth muscle fibers (not seen in saline-controls) at only the acute stages of envenoming suggests a mediator role for VEGFR-1 in local alterations. This is the first time that VEGFR-1 expression, and its modulation by photostimulation, has been demonstrated in endothelial and nonendothelial cells of snake envenomed skeletal muscle.

Phototherapy improves healing of chronic venous ulcers

OBJECTIVE

We tested the hypothesis that LED phototherapy with combined 660-nm and 890-nm light will promote healing of venous ulcers that failed to respond to other forms of treatment.

BACKGROUND DATA

A variety of dressings, growth factors, and adjunct therapies are used to treat venous ulcers, but none seems to yield satisfactory results.

MATERIALS AND METHODS

We used a randomized placebo-controlled double-blind study to compare a total of 20 patients divided with 32 chronic ulcers into three groups. In group 1 the ulcers were cleaned, dressed with 1% silver sulfadiazine (SDZ) cream, and treated with placebo phototherapy (<.03 J/cm(-3)) using a Dynatron Solaris 705 phototherapy research device. In group 2 the ulcers were treated similarly but received real phototherapy (3 J/cm(-2)) instead of placebo. In group 3 (controls), the ulcers were simply cleaned and dressed with SDZ without phototherapy. The ulcers were evaluated with digital photography and computer image analysis over 90 d or until full healing was attained.

RESULTS

Ulcers treated with phototherapy healed significantly faster than controls when compared at day 30 (p +/- 0.01), day 60 (p +/- 0.05), and day 90 (p +/- 0.001), and similarly healed faster than the placebo-treated ulcers at days 30 and 90 (p +/- 0.01), but not at day 60. The beneficial effect of phototherapy was more pronounced when the confounding effect of small-sized ulcers was removed from the analysis. Medium- and large-sized ulcers healed significantly faster with treatment (>or=40% rate of healing per month) than placebo or control ulcers (p +/- 0.05).

CONCLUSION

Phototherapy promotes healing of chronic venous ulcers, particularly large recalcitrant ulcers that do not respond to conventional treatment.

Quantification of fibrosis and mast cells in the tissue response of endodontic sealer irradiated by low-level laser therapy

Low-level laser therapy (LLLT) accelerates tissue repair. Mast cells induce the proliferation of fibroblasts and the development of local fibrosis. The objective of this study was to quantify fibrosis rate and mast cells in connective tissue after endodontic sealer zinc oxide and eugenol (ZOE) was implanted and submitted to LLLT, immediately after implant and again 24 h later. Sixty mice were distributed into three groups: GI, GII, and GIII (n = 20). In GI, the tubes filled with Endofill were implanted in the animals and were not irradiated with LLLT. In GII, the tubes containing Endofill were implanted in the animals and then irradiated with red LLLT (InGaAIP) 685-nm wavelength, D = 72 J/Cm(2), E = 2 J, T = 58 s, P = 35 mW, and in GIII, the tubes with Endofill were implanted and irradiated with infrared LLLT (AsGaAl) 830-nm wavelength, D = 70 J/Cm(2), E = 2 J, T = 40 s, P = 50 mW. After 7 days and 30 days, the animals were killed. A series of 6-µm-thick sections were obtained and stained with Toluidine Blue and Picrosirius and analyzed under a standard light microscope using a polarized light filter for the quantification of fibrosis. The statistics were qualitative and quantitative with a significance of 5%. The irradiation with LLLT did not offer improvement in the fibrosis rate, however, it provided a significant decrease in the concentration of independent mast cells for the period studied.

Electrophysiologic effects of a therapeutic laser on myofascial trigger spots of rabbit skeletal muscles

OBJECTIVE

To better understand the mechanisms of therapeutic lasers for treating human myofascial trigger points, we designed a blinded controlled study of the effects of a therapeutic laser on the prevalence of endplate noise (EPN) recorded from the myofascial trigger spot (MTrS) of rabbit skeletal muscle.

DESIGN

In eight rabbits, one MTrS in each biceps femoris muscle was irradiated with a 660-nm, continuous-wave, gallium-aluminum-arsenate (GaAlAs) laser, at 9 J/cm2. The contralateral side of muscle was treated with a sham laser. Each rabbit received six treatments. The immediate and cumulative effects were assessed by the prevalence of EPN with electromyographic (EMG) recordings after the first and last treatments.

RESULTS

Compared with pretreatment values, the percentages of EPN prevalence in the experimental side after the first and last treatments were significantly reduced (P < 0.01 for both). The change in EPN prevalence in the experimental side was significantly greater than in the control side immediately after the first and last treatments (P < 0.05). However, no significant differences were noted between the first and last treatments (P > 0.05).

CONCLUSIONS

In our study, immediate and cumulative effects of a GaAlAs laser applied on MTrS were demonstrated on the basis of the assessment of EPN prevalence. It seems that laser irradiation may inhibit the irritability of an MTrS in rabbit skeletal muscle. This effect may be a possible mechanism for myofascial pain relief with laser therapy.

An in-vivo experimental evaluation of He-Ne laser photostimulation in healing Achilles tendons

There is no method of treatment that has been proven to accelerate the rate of tendon healing or to improve the quality of the regenerating tendon. Low level laser photostimulation has gained a considerable attention for enhancing tissue repair in a wide spectrum of applications. However, there is controversy regarding the effectiveness of laser photostimulation for improvement of the healing process of surgically repaired tendons. Accordingly, the present study was conducted to evaluate the role of helium-neon (He-Ne) laser photostimulation on the process of healing of surgically repaired Achilles tendons. Thirty unilateral Achilles tendons of 30 Raex rabbits were transected and immediately repaired. Operated Achilles tendons were randomly divided into two equal groups. Tendons at group A were subjected to He-Ne laser (632.8 nm) photostimulation, while tendons at group B served as a control group. Two weeks later, the repaired Achilles tendons were histopathologically and biomechanically evaluated. The histopathological findings suggest the favorable qualitative pattern of the newly synthesized collagen of the regenerating tendons after He-Ne laser photostimulation. The biomechanical results support the same favorable findings from the functional point of view as denoted by the better biomechanical properties of the regenerating tendons after He-Ne laser photostimulation with statistical significance (p <or= 0.01) at most of the biomechanical parameters. He-Ne laser photostimulation reported a great value after surgical repair of ruptured and injured tendons for a better functional outcome. It could be applied safely and effectively in humans, especially with respect to the proposed long-term clinical outcome.

Comparative Study Using 685-nm and 830-nm Lasers in the Tissue Repair of Tenotomized Tendons in the Mouse

OBJECTIVE

The objective of this study was to evaluate the effects of 685- and 830-nm laser irradiations, at different fluences on the healing process of Achilles tendon (Tendon calcaneo) of mice after tenotomy.

BACKGROUND DATA

Some authors have shown that low-level laser therapy (LLLT) is able to accelerate the healing process of tendinuos tissue after an injury, increasing fibroblast cell proliferation and collagen synthesis. However, the mechanism by which LLLT acts on healing process is not fully understood.

METHODS

Forty-eight male mice were divided into six experimental groups: group A, tenomized animals, treated with 685 nm laser, at the dosage of 3 J/cm(2); group B, tenomized animals, treated with 685-nm laser, at the dosage of 10 J/cm(2); group C, tenomized animals, treated with 830-nm laser, at dosage of 3 J/cm(2); group D, tenomized animals, treated with 830-nm laser, at the dosage of 10 J/cm(2); group E, injured control (placebo treatment); and group F, non-injured standard control. Animals were killed on day 13 post-tenotomy, and their tendons were surgically removed for a quantitative analysis using polarization microscopy, with the purpose of measuring collagen fibers organization through the birefringence (optical retardation [OR]).

RESULTS

All treated groups showed higher values of OR when compared to injured control group. The best organization and aggregation of the collagen bundles were shown by the animals of group A (685 nm, 3 J/cm(2)), followed by the animals of group C and B, and finally, the animals of group D.

CONCLUSION

All wavelengths and fluences used in this study were efficient at accelerating the healing process of Achilles tendon post-tenotomy, particularly after the 685-nm laser irradiation, at 3 J/cm(2). It suggests the existence of wavelength tissue specificity and dose dependency. Further studies are required to investigate the physiological mechanisms responsible for the effects of laser on tendinuos repair.

Ultrastructural and autoradiographical analysis show a faster skin repair in He-Ne laser-treated wounds

There are evidences that low-intensity red laser radiation is capable to accelerate wound healing. Nowadays, this therapy has been gradually introduced in clinical practice although mechanisms underlying laser effects are poorly understood. To better understand the photobiological effects of laser radiation, this study investigated by electron microscopy, immunohistochemistry and autoradiography the morphological and functional features of irradiated and none irradiated injured mice skin. Full-thickness skin lesions were created on the back of mice and irradiated on days 1, 5, 8, 12, and 15 post-wounding with a He-Ne laser (lambda=632.8nm), dose 1J/cm(2), exposure time 3min. Non-irradiated lesions were used as a control. The mice were inoculated with (3)H-proline and sacrificed one hour after on the 8th, 15th and 22nd days to histological and radioautographical analysis. The irradiated-lesions showed a faster reepithelization compared with control lesions. The irradiated dermis contained a higher number of activated fibroblasts compared to control group and, most of them showed several cytoplasmic collagen-containing phagosomes. In irradiated-lesions, smooth muscle alpha-actin positive cells predominated, which correspond to a higher number of myofibroblasts observed in the electron microscope. Moreover, laser radiation reduced the local inflammation and appears to influence the organization of collagen fibrils in the repairing areas. Quantitative autoradiography showed that the incorporation of (3)H-proline was significantly higher in irradiated-dermis on the 15th day post-wounding (p<0.05). These results suggest that laser radiation may accelerate cutaneous wound healing in a murine model.

Low-Level Laser Therapy Improves Early Healing of Medial Collateral Ligament Injuries in Rats

OBJECTIVE

This study sought to investigate whether or not low-level laser therapy (LLLT) with a helium-neon laser increased biomechanical parameters of transected medial collateral ligament (MCL) in rats.

BACKGROUND DATA

It has been reported that LLLT can enhance tendon healing.

METHODS

Thirty rats received surgical transection to their right MCL, and five were assigned as the control group. After surgery, the rats were divided into three groups: group 1 (n = 10) received LLLT with 0.01 J/cm(2) energy density per day, group 2 (n = 10) received LLLT with 1.2 J/cm(2) energy density per day, and group 3 (sham = exposed group; n = 10) received daily placebo laser with shut-down laser equipment, while the control group received neither surgery nor LLLT. Biomechanical tests were performed at 12 and 21 days after surgery. The data were analyzed by one-way analysis of variance.

RESULTS

The ultimate tensile strength (UTS) of group 2 on day 12 was significantly higher than that of groups 1 and 3. Furthermore, the UTS and energy absorption of the control (uninjured) group were significantly higher than those of the other groups.

CONCLUSIONS

LLLT with a helium-neon laser is effective for the early improvement of the ultimate tensile strength of medial collateral ligament injuries.

The efficacy of laser therapy in wound repair: a meta-analysis of the literature

OBJECTIVE

We determined the overall effects of laser therapy on tissue healing by aggregating the literature and subjecting studies meeting the inclusion and exclusion criteria to statistical meta-analysis.

BACKGROUND DATA

Low-level laser therapy (LLLT) devices have been in use since the mid sixties, but their therapeutic value remains doubtful, as the literature seems replete with conflicting findings.

MATERIALS AND METHODS

Pertinent original research papers were gathered from library sources, online databases and secondary sources. The papers were screened and coded; those meeting every inclusion and exclusion criterion were subjected to meta-analysis, using Cohen's d. statistic to determine the treatment effect size of each study.

RESULTS

Twenty-four studies with 31 effect sizes met the stringent inclusion and exclusion criteria. The overall mean effect of laser therapy on wound healing was highly significant (d = +2.22). Sub-analyses of the data revealed significant positive effects on wound healing in animal experiments (d = +1.97) as well as human clinical studies (d = +0.54). The analysis further revealed significant positive effects on specific indices of healing, for example, acceleration of inflammation (d = +4.45); augmentation of collagen synthesis (d = +1.80); increased tensile strength (d = +2.37), reduced healing time (d = +3.24); and diminution of wound size (d = +0.55). The Fail-Safe number associated with the overall effect of laser therapy was 509; a high number representing the number of additional studies-in which laser therapy has negative or no effect on wound healing-required to negate the overall large effect size of +2.22. The corresponding Fail-Safe number for clinical studies was 22.

CONCLUSION

We conclude that laser therapy is an effective tool for promoting wound repair.

Comparison of single and multiple applications of GaAlAs laser on rat medial collateral ligament repair

BACKGROUND AND OBJECTIVES

To examine single versus multiple applications of the gallium aluminum arsenide (GaAlAs) laser on the healing of surgically injured medial collateral ligaments (MCLs) in rats.

STUDY DESIGN/MATERIALS AND METHODS

Sixteen rats were studied, with 12 receiving surgical transection to their right MCL and 4 receiving a sham injury. Group 1 (n = 4) received a single dose of GaAlAs laser therapy (wavelength 660 nm, average power 8.8 mW, pulse 10 kHz, dosage 31.6 J/cm(2)) directly to their MCL during surgery. Group 2 (n = 4) received 9 doses of GaAlAs laser therapy applied transcutaneously on alternate days (wavelength 660 nm, average power 8.8 mW, pulse 10 kHz, dosage 3.5 J/cm(2)). The controls (Group 3, n = 4) received one session of placebo laser at the time of surgery, with the laser equipment shut down, while the sham injured Group 4 (n = 4) received no treatment. Biomechanical tests for structural stiffness, ultimate tensile strength (UTS), and load-relaxation were done at 3 weeks after injury. The stiffness and UTS data were normalized by expressing as a percentage of the left side of each animal before statistical analysis.

RESULTS

The load-relaxation data did not show any differences between the groups (P = 0.18). The normalized stiffness levels of Groups 2 (81.08+/-11.28%) and 4 (92.66+/-13.19%) were significantly higher (P = 0.025) than that of the control Group 3 (58.99+/-15.91%). The normalized UTS of Groups 2 (81.38+/-5.68%) and 4 (90.18+/-8.82%) were also significantly higher (P = 0.012) than that of the control (64.49+/-9.26%). Although, Group 1 had higher mean stiffness and UTS values than the control, no statistically significant difference was found between these two groups.

CONCLUSIONS

Multiple laser therapy improves the normalized strength and stiffness of repairing rat MCLs at 3 weeks after injury. The multiple treatments seem to be superior to a single treatment when the cumulative dosages are comparable between the two modes of application.

Photobiological Basis and Clinical Role of Low-Intensity Lasers in Biology and Medicine

The purpose of this article is to provide a comprehensive review on the clinical role of low intensity laser therapy (laser photostimulation) in biology and medicine. Studies on wound healing and pain relief are highlighted to show the clinical efficacy of laser therapy. Controversies about the use of low intensity laser as a therapeutic modality for wound healing and pain relief are presented and a brief explanation is provided to overcome these controversies. The importance of standard parameters is emphasized for the applications of low intensity lasers in biology and medicine. A justification has been made to warrant further research on the use of low intensity laser as a therapeutic modality. Although the therapeutic applications of low intensity laser are imminent, the heterogeneity in treatment protocols and study design calls for a vigilant interpretation of the findings.

Therapeutic low energy laser improves the mechanical strength of repairing medial collateral ligament

BACKGROUND AND OBJECTIVES

Low energy laser therapy has been shown to enhance collagen production but its effect on tissue strength is not well reported. We tested the effects of therapeutic laser on the strength of healing medial collateral ligaments (MCLs) in rats.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-four rats received surgical transection to their right MCL and eight received sham operation. After surgery, 16 received a single dose of gallium aluminum arsenide laser to their transected MCL for 7.5 minutes (n = 8) or 15 minutes (n = 8) and eight served as control with placebo laser, while the sham group didn't receive any treatment. The MCLs were biomechanically tested at either 3 or 6 weeks post-operation.

RESULTS

The normalized ultimate tensile strength (UTS) and stiffness of laser and sham groups were larger than control (P < 0.001). The UTS of laser and sham groups were comparable. Laser and sham groups had improved in stiffness from 3 to 6 weeks (P < 0.001).

CONCLUSIONS

A single dose of low energy laser therapy improves the UTS and stiffness of repairing MCL at 3 and 6 weeks after injury.

Laser photostimulation accelerates wound healing in diabetic rats

In this study, we examined the hypothesis that laser photostimulation can facilitate healing of impaired wounds in experimental diabetes using a rat model. Diabetes was induced in male rats by streptozotocin injection and two 6 mm diameter circular wounds were created on either side of the spine. The left wound of each animal was treated with a 632.8 nm He:Ne laser at a dose of 1.0 J/cm2 for five days a week until the wounds closed (three weeks). Measurements of the biomechanical properties of the laser-treated wounds indicated there was a marginal increase in maximum load (16%), stress (16%), strain (27%), energy absorption (47%) and toughness (84%) compared to control wounds of diabetic rats. Biochemical assays revealed that the amount of total collagen was significantly increased in laser treated wounds (274 +/- 8.7 microg) over the control wounds (230 +/- 8.4 microg). Sequential extractions of collagen from healing wounds showed that laser treated wounds had significantly greater concentrations of neutral salt soluble (15%) and insoluble collagen (16%) than control wounds, suggesting accelerated collagen production in laser treated wounds. There was an appreciable decrease in pepsin soluble collagen (19%) in laser treated wounds over control wounds, indicating higher resistance to proteolytic digestion. In conclusion, the biomechanical and biochemical results collectively suggest that laser photostimulation promotes the tissue repair process by accelerating collagen production and promoting overall connective tissue stability in healing wounds of diabetic rats.

Laser photostimulation of collagen production in healing rabbit Achilles tendons

BACKGROUND AND OBJECTIVE

Low energy laser photostimulation at certain wavelengths can enhance tissue repair by releasing growth factors from fibroblasts and stimulate the healing process. This study was designed to evaluate the influence of laser photostimulation on collagen production in experimentally tenotomized and repaired rabbit Achilles tendons.

STUDY DESIGN/MATERIALS AND METHODS

A total of 24 male New Zealand rabbits, ages 10-12 weeks, were used. Following tenotomy and repair, the surgical hind limbs of the rabbits were immobilized in customized polyurethane casts. The experimental animals were treated with a 632.8 nm He:Ne laser daily at 1.0 J cm(-2) for 14 days. Control animals were sham treated with the laser head. On the fifth day after repair, the casts were removed to allow the animals to bear weight on the lower extremity. The animals were euthanized on the 15th postoperative day, then, the Achilles tendons were excised, processed and analyzed.

RESULTS

Biochemical analyses of the tendons revealed a 26% increase in collagen concentration with laser photostimulation indicating a more rapid healing process in treated tendons compared to controls. Sequential extractions of collagen from regenerating tissues revealed that the laser photostimulated tendons had 32% and 33% greater concentrations of neutral salt soluble collagen and insoluble collagen, respectively, than control tendons suggesting an accelerated production of collagen with laser photostimulation. A significant decrease (9%) in pepsin soluble collagen was observed in laser-treated tendons compared to controls. There were no statistically significant differences recorded in the concentrations of hydroxypyridinium crosslinks and acid soluble collagen between treated and control tendons.

CONCLUSION

This study of laser photostimulation on tendon healing in rabbits suggests that such therapy facilitates collagen production in a manner that enhances tendon healing.

Effects on the mitosis of normal and tumor cells induced by light treatment of different wavelengths

OBJECTIVE

Although the background of laser therapy by means of low level energy and power is still only partially understood, there are nevertheless promising reports from clinical studies concerning pain treatment, the acceleration of wound healing, and the modulation of cell functions. In order to contribute to the understanding of such a phototherapeutic procedure cell experiments were performed.

MATERIALS AND METHODS

The influence of light (lambda = 410, 488, 630, 635, 640, 805, and 1,064 nm and broad band white light) on the proliferation of cells was investigated on skeletal myotubes (C2), normal urothelial cells (HCV29), human squamous carcinoma cells of the gingival mucosa (ZMK1), urothelial carcinoma cells (J82), glioblastoma cells (U373MG), and mamma adenocarcinoma cells (MCF7) in a computer-controlled light treatment chamber. The cellular response was tested by way of the following methods: The rate of mitosis was determined by counting the single cells after Orcein-staining. The proliferation index measurements were based on the BrdU incorporation during the DNA synthesis. Statistics were performed using unpaired Student's t-test procedures, stating P < 0. 05 to be significant and P>0.05 not to be significant.

RESULTS

Twenty-four hours after light treatment, a significant increase in the mitotic rate of J82 and HCV29 cells was determined when illuminated with lambda = 410 nm, lambda = 635 nm and lambda = 805 nm, respectively. C2 cells showed an increase only after lambda = 635 nm illumination. In all three cell lines, a maximum mitotic rate was determined after an irradiation between 4 and 8 J/cm(2), while a reduced mitotic rate was measured at 20 J/cm(2). MCF7, U373MG, and ZMK1 cells showed a slight decrease in the mitotic rate with increasing irradiation independent of the wavelength used. When an irradiation of 20 J/cm(2) was applied, all cell lines showed a slight decrease compared to the controls independent to the wavelength used. White light as well as lambda = 1,064 nm does not affect the mitotic rate in this irradiation range. No significant differences in the effects could be determined when the irradiance changed between 10 and 150 mW/cm(2) at certain irradiation values. The BrdU test did not show any significant alterations with respect to possible light induced processes compared to the controls.

CONCLUSIONS

Dependent upon the irradiation parameter, light of a defined wavelength does affect the mitotic rate of both normal as well as tumor cells. It could be hypothesized that the action spectra of the cellular response indicate the participation of endogenous porphyrins and cytochromes as primary photoreceptors. Taking into account all light induced processes, the term biomodulation should preferably be used.

Biochemistry and biomechanics of healing tendon: Part II. Effects of combined laser therapy and electrical stimulation

PURPOSE

In previous studies we demonstrated that early mechanical loading and laser photo-stimulation independently promoted tendon healing. Thus, we tested the hypothesis that a combination of laser phototherapy and mechanical load would further accelerate healing of experimentally tenotomized and repaired rabbit Achilles tendons.

METHODS

Following surgical tenotomy and repair, the tendons of experimental and control rabbits were immobilized in polyurethane casts for 5 d. The repaired tendons of experimental rabbits received mechanical load via electrical stimulation-induced contraction of the triceps surae for 5 d. In addition, experimental tendons were treated with daily doses of 1 J.cm-2 low intensity helium-neon laser throughout the 14-d experimental period.

RESULTS

The combination of laser photostimulation and mechanical load increased the maximal stress, maximal strain, and Young's modulus of elasticity of the tendons 30, 13, and 33%, respectively. However, MANOVA revealed no statistically significant differences in these biomechanical indices of repair of control and experimental tendons. Biochemical assays showed a 32% increase in collagen levels (P < 0.05) and an 11% decrease in mature cross-links in experimental tendons compared with that in controls (P > 0.05). Electron microscopy and computer morphometry revealed no significant differences in the morphometry of the collagen fibers and no visible differences in the ultrastructure of cellular and matrical components of control and experimental tendons.

CONCLUSIONS

These findings indicate that the combination of laser photostimulation and early mechanical loading of tendons increased collagen production, with marginal biomechanical effects on repaired tendons.

Biomodulative effects induced by 805 nm laser light irradiation of normal and tumor cells

The influence of light emitted from a diode laser centred at lambda = 805 nm was investigated on murine skeletal myotubes (C2), normal urothelial cells (HCV29), human squamous carcinoma cells of the gingival mucosa (ZMK) and urothelial carcinoma cells (J82) in a computer-controlled irradiation chamber. Cells were treated with varying fluences between 0 and 20 J cm-2. The response was tested by analysis of the mitotic index using single cell counting after Orcein staining and proliferation index based on BrdU incorporation during DNA synthesis. While the mitotic index of C2, HCV29 and J82 cells increased at a fluence of 4 J cm-2, irradiation with fluences of 20 J cm-2 resulted in a slight decrease. ZMK tumor cells showed a decrease of the mitotic index with both fluences. No significant differences could be determined when using irradiances between 10 mW cm-2 and 150 mW cm-2. The BrdU test after irradiation showed no significant effects compared to the controls in each cell line.

Combined ultrasound, electrical stimulation, and laser promote collagen synthesis with moderate changes in tendon biomechanics

The biomechanical, biochemical, and ultrastructural effects of a multitherapeutic protocol were studied using regenerating rabbit Achilles tendons. The multitherapeutic protocol was composed of low-intensity Ga:As laser photostimulation, low intensity ultrasound, and electrical stimulation. Achilles tendons of 63 male New Zealand rabbits were tenotomized, sutured, immobilized, and subjected to the multitherapeutic protocol for five days, after which casts were removed and the therapy was continued for nine more days without electrical stimulation. The tendons were excised and compared with control tendons. Multitherapy treatment produced a 14% increase in maximal strength, a 42% increase in load-at-break, a 20% increase in maximal stress, a 45% increase in stress-at-break, a 21% increase in maximal strain, and a 14% increase in strain-at-break. Similarly, multitherapy treatment was associated with an increase in Young's modulus of elasticity of 31%, an increase in energy absorption at maximum load of 9%, and an increase in energy absorption at load-at-break of 11%. Biochemical analysis of the tendons showed an increase of 23% in the total amount of collagen in the multitherapy-treated tendons, with fewer mature crosslinks (decrease of 6%). Electron micrographs revealed no ultrastructural or morphologic changes in the tendon fibroblasts or in the extracellular matrix. The improvements measured in tendons receiving multitherapy were consistent but less remarkable compared with our earlier works with single modality protocols. The results warrant the hypothesis that the beneficial effects of ultrasound and laser photostimulation on tendon healing may counteract one another when applied simultaneously.

Low intensity laser therapy: still not an established clinical tool

The surgical, ophthalmological, and dermatological applications of high power lasers are well known and easily understood. What is neither as well known nor as easily understood is that lasers at powers that are orders of magnitude smaller have also been used in the laboratory and clinic for nearly 30 years to modulate cell function, lessen pain, and accelerate healing of soft tissue injuries. This article analyzes the rationale of this approach, examines the utility of laser therapy in its most common clinical applications, reviews and synthesizes the findings, and concludes that although laboratory findings seem authentic, clinical utility remains unestablished.