Laser-treated Rats Research Articles

Evaluation of the effects of photobiomodulation on vertebras in two rat models of experimental osteoporosis.

The aim of this study was to evaluate the effects of photobiomodulation (PBM) on cancellous bone in rat models of ovariectomized induced osteoporosis (OVX-D) and glucocorticoid-induced osteoporosis (GIOP). The experiment comprised of nine groups. A group of healthy rats was used for baseline evaluations. The OVX-D rats were further divided into groups as follows: control rats with osteoporosis, OVX-D rats that received alendronate (1mg/kg 60days), OVX-D rats treated with pulsed wave laser (890nm, 80Hz, 900s, 0.0061W/cm2, 5.5J/cm2, three times a week, 60days), and OVX-D rats treated with alendronate + pulsed laser. Dexamethasone was administered to the remaining rats that were split into four groups: control, alendronate-treated rats, laser-treated rats, and GIOP rats treated with alendronate + laser. T12, L1, L2, and L3 vertebrae were subjected to laser. Results of the current study demonstrated that OVX-D and GIOP significantly decreased some stereological parameters, and type 1 collagen gene expression compared to the healthy group. There was a significant increase in osteoclast number in both OVX-D and glucocorticoid administration compared to the healthy group. However, the detrimental effect of the OVX-D procedure on bone was more serious than glucocorticoid administration. Results showed that laser alone had a detrimental effect on trabecular bone volume, and cortical bone volume in groups GIOP and OVX-D compared to those in the healthy group. Alendronate significantly improved total vertebral bone volume, trabecular bone volume, and cortical bone volume, in GIOP and OVX-D groups compared to the laser-treated groups. Furthermore, the alendronate + laser in OVX-D rats and GIOP rats produced significantly increased osteoblast number and type 1 collagen gene expression and caused a significant decrease in osteoclast number compared to the controls.

Effect of photobiomodulation on ischemia/reperfusion-induced renal damage in diabetic rats.

This study was designed to investigate the possible effect of photobiomodulation (PBM) on renal damage induced by ischemia reperfusion (IR) in diabetic rats. Twenty streptozotocin-induced diabetic rats were randomly distributed into two groups, containing ten rats each: IR group (G1) and IR + PBM group (G2). After the right nephrectomy, the ischemia was produced in the left kidney for 30min, followed by the reperfusion for 24h. Then, a 685-nm laser diode with an output power of 15mW (spot size = 0.28cm2 and energy density = 3.2J/cm2) was employed. PBM was carried out by irradiating the rats over six points on the skin over the left kidney region three times, i.e., immediately after skin suturing and 1 and 2h after initiating reperfusion for 6min. At the end of reperfusion period, the rats were anesthetized, and blood samples were collected and used for the estimation of renal function (blood urea nitrogen (BUN) and creatinine). Then, the left kidney was harvested for histological and biochemical examination. The serum levels of BUN and creatinine were significantly higher in G1 compared to G2 (P < 0.05). G1 had higher renal malondialdehyde (MDA) levels compared to G2 (P < 0.05). Renal IR in diabetic rats (G1) resulted in a significant decrease in renal tissue glutathione (GSH) (P < 0.05) when compared to laser-treated rats (G2). A significant restoration was observed in the levels of superoxide dismutase (SOD) (P < 0.05) and catalase (CAT) (P < 0.05) in G2 as compared to G1. The levels of nitric oxide (NO) were increased in G1 in comparison to G2 (P < 0.05). The myeloperoxidase (MPO) activity was significantly higher in the renal tissue of G1 than that of G2 (P < 0.05). In addition, specimens from the G1 had a significantly greater histological injury than those from the G2 (P < 0.05). The results of present investigation revealed that PBM attenuated kidney damage induced by renal IR in diabetic rats.

Evaluation of the effects of pulsed wave LLLT on tibial diaphysis in two rat models of experimental osteoporosis, as examined by stereological and real-time PCR gene expression analyses.

Osteoporosis (OP) and osteoporotic fracture are major public health issues for society; the burden for the affected individual is also high. Previous studies have shown that pulsed wave low-level laser therapy (PW LLLT) has osteogenic effects. This study intended to evaluate the impacts of PW LLLT on the cortical bone of osteoporotic rats' tibias in two experimental models, ovariectomized and dexamethasone-treated. We divided the rats into four ovariectomized induced OP (OVX-d) and four dexamethasone-treated (glucocorticoid-induced OP, GIOP) groups. A healthy (H) group of rats was considered for baseline evaluations. At 14 weeks following ovariectomy, we subdivided the OVX-d rats into the following groups: (i) control which had OP, (ii) OVX-d rats treated with alendronate (1 mg/kg), (iii) OVX-d rats treated with LLLT, and (iv) OVX-d rats treated with alendronate and PW LLLT. The remaining rats received dexamethasone over a 5-week period and were also subdivided into four groups: (i) control rats treated with intramuscular (i.m.) injections of distilled water (vehicle), (ii) rats treated with subcutaneous alendronate injections (1 mg/kg), (iii) laser-treated rats, and (iv) rats simultaneously treated with laser and alendronate. The rats received alendronate for 30 days and underwent PW LLLT (890 nm, 80 Hz, 0.972 J/cm(2)) three times per week during 8 weeks. Then, the right tibias were extracted and underwent a stereological analysis of histological parameters and real-time polymerase chain reaction (RT-PCR). A significant increase in cortical bone volume (mm(3)) existed in all study groups compared to the healthy rats. There were significant decreases in trabecular bone volume (mm(3)) in all study groups compared to the group of healthy rats. The control rats with OP and rats from the vehicle group showed significantly increased osteoclast numbers compared to most other groups. Alendronate significantly decreased osteoclast numbers in osteoporotic rats. Concurrent treatments (compounded by PW LLLT and alendronate) produce the same effect on osteoporotic bone.

An evaluation of the effect of pulsed wave low-level laser therapy on the biomechanical properties of the vertebral body in two experimental osteoporosis rat models.

Osteoporosis (OP) increases vertebral fragility as a result of the biomechanical effects of diminished bone structure and composition. This study has aimed to assess the effects of pulsed wave low-level laser therapy (PW LLLT) on cancellous bone strength of an ovariectomized (OVX-d) experimental rat model and a glucocorticoid-induced OP (GIOP) experimental rat model. There were four OVX-d groups and four dexamethasone-treated groups. A group of healthy rats was used for baseline evaluations. The OVX-d rats were further subdivided into the following groups: control rats with OP, OVX-d rats that received alendronate, OVX-d rats treated with PW LLLT, and OVX-d rats treated with alendronate and PW LLLT. The remaining rats received dexamethasone and were divided into four groups: control, alendronate-treated rats, laser-treated rats, and laser-treated rats with concomitant administration of alendronate. PW LLLT (890 nm, 80 Hz, 0.972 J/cm(2)) was performed on the spinal processes of the T12, L1, L2, and L3 vertebras. We extracted the L1 vertebrae and submitted them to a mechanical compression test. Biomechanical test findings showed positive effects of the PW LLLT and alendronate administration on increasing bending stiffness and maximum force of the osteoporotic bones compared to the healthy group. However, laser treatment of OVA-d rats significantly increased stress high load compared to OVA-d control rats. PW LLLT preserved the cancellous (trabecular) bone of vertebra against the detrimental effects of OV-induced OP on bone strength in rats compared to control OV rats.

Evaluating glucocorticoid administration on biomechanical properties of rats' tibial diaphysis.

Background:Osteoporosis is a disease, which causes bone loss and fractures. Although glucocorticoids effectively suppress inflammation, their chronic use is accompanied by bone loss with a tendency toward secondary osteoporosis.Objectives:This study took into consideration the importance of cortical bone in the entire bone's mechanical competence. Hence, the aim of this study was to assess the effects of different protocols of glucocorticoid administration on the biomechanical properties of tibial bone diaphysis in rats compared to control and low-level laser-treated rats.Materials and Methods:This experimental study was conducted at Shahid Beheshti University of Medical Sciences, Tehran, Iran. We used systematic random sampling to divide 40 adult male rats into 8 groups with 5 rats in each group. Groups were as follows: 1) control, 2) dexamethasone (7 mg/week), 3) dexamethasone (0.7 mg/week), 4) methylprednisolone (7 mg/kg/week), 5) methylprednisolone (5 mg/kg twice weekly), 6) dexamethasone (7 mg/kg three times per week), 7) dexamethasone (0.7 mg/kg thrice per week), and 8) low-level laser-treated rats. The study periods were 4-7 weeks. At the end of the treatment periods, we examined the mechanical properties of tibial bone diaphysis. Data were analyzed by statistical analyses.Results:Glucocorticoid-treated rats showed weight loss and considerable mortality (21%). The biomechanical properties (maximum force) of glucocorticoid-treated rats in groups 4 (62 ± 2.9), 6 (63 ± 5.1), and 7 (60 ± 5.3) were comparable with the control (46 ± 1.5) and low-level laser-treated (57 ± 3.2) rats.Conclusions:In contrast to the findings in humans and certain other species, glucocorticoid administration caused anabolic effect on the cortical bone of tibia diaphysis bone in rats.

Evaluation of the effects of LLLT on biomechanical properties of tibial diaphysis in two rat models of experimental osteoporosis by a three point bending test.

Osteoporosis (OP) is a disease which causes bone loss and fractures, leading to severe pain and deformity. This study has aimed to assess the effects of pulsed wave low-level laser therapy (PW LLLT) on cortical bone in two experimental models of OP in rats. There were four ovariectomized (OVX-d) groups and four dexamethasone-treated groups. The healthy group were considered for baseline evaluations. At 14weeks following ovariectomy, the OVX-d rats were further subdivided into the following: control rats with OP, OVX-d rats that received alendronate (1mg/kg), OVX-d rats treated with LLLT, and OVX-d rats treated with alendronate and LLLT. The remaining rats received dexamethasone for 5weeks and were divided into four groups: control, alendronate-treated rats (1mg/kg), laser-treated rats, and laser-treated rats with concomitant administration of alendronate. The rats received alendronate for 30days. LLLT (890nm, 80Hz, 0.972J/cm(2)) was performed on the tibias three times per week for 8weeks. After 8weeks, tibias were extracted and submitted to a three-point bending test. PW LLLT did not increase the biomechanical parameters of osteoporotic bones compared to controls and healthy rats. PW LLLT associated with alendronate treatment significantly increased stress high load in OVX-d rats compared to the healthy group. PW LLLT at the current study parameters failed to cause beneficial biomechanical effects in the examined osteoporotic cortical bones. PW LLLT associated with alendronate treatment produced a more remarkable effect on bone strength in the ovariectomized induced OP rat model.

Supraphysiologic glucocorticoid administration increased biomechanical bone strength of rats' vertebral body.

The aim of this study is to assess the effects of different glucocorticoid administration protocols on biomechanical properties of the first lumbar vertebral body in rats. We divided 40 male rats into the following groups: control, dexamethasone (7 mg/week), dexamethasone (0.7 mg/week), methylprednisolone (7 mg/kg/week), methylprednisolone (5 mg/kg twice weekly), dexamethasone (7 mg/kg three times per week), dexamethasone (0.7 mg/kg three times per week, and low-level laser treated rats. Lumbar vertebrae in rats were exposed to the pulsed laser. We conducted a biomechanical test to examine the mechanical properties of vertebral body in rats' lumbar bone. Supraphysiologic glucocorticoid administration protocols did not impair the biomechanical properties of rats' vertebral bodies compared to control and laser-treated rats. Supraphysiologic glucocorticoid administration caused an anabolic effect on the vertebral bodies.

Autologous Bone-Marrow Stem Cells Stimulation Reverses Post-Ischemic-Reperfusion Kidney Injury in Rats

Background/Aims: Low-level laser therapy (LLLT) has been found to modulate biological activity. The aim of the present study was to investigate the possible beneficial effects of LLLT application to stem cells in the bone marrow (BM), on the kidneys of rats that had undergone acute ischemia-reperfusion injury (IRI). Methods: Injury to the kidneys was induced by the excision of the left kidney and 60 min of IRI to the right kidney in each rat. Rats were then divided randomly into 2 groups: non-laser-treated and laser-treated. LLLT was applied to the BM 10 min and 24 h post-IRI and rats were sacrificed 4 days post-IRI. Blood was collected before the sacrifice and the kidney processed for histology. Results: Histological evaluation of kidney sections revealed the restored structural integrity of the renal tubules, and a significant reduction of 66% of pathological score in the laser-treated rats as compared to the non-laser-treated ones. C-kit positive cell density in kidneys post-IRI and laser-treatment was (p = 0.05) 2.4-fold higher compared to that of the non-laser treated group. Creatinine, blood urea nitrogen, and cystatin-C levels were significantly 55, 48, and 25% lower respectively in the laser-treated rats as compared to non-treated ones. Conclusion: LLLT application to the BM causes induction of stem cells, which subsequently migrate and home in on the injured kidney. Consequently, a significant reduction in pathological features and improved kidney function post-IRI are evident. The results demonstrate a novel approach in cell-based therapy for acute ischemic injured kidneys. i 2014 S. Karger AG, Basel

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.

Induction of Autologous Bone-Marrow Stem Cells by Low-Level Laser Therapy Has Beneficial Effects on the Kidneys Post-Ischemia-Reperfusion Injury in the Rat

Acute renal failure has a 50% - 80% mortality rate. Currently, treatment options for this life-threatening disease are limited. Low-level laser therapy (LLLT) has been found to modulate biological activity. The aim of the present study was to investigate the possible beneficial effects of laser application to stem cells in the bone marrow, on the kidneys of rats that had undergone ischemia-reperfusion injury (IRI). IRI was induced by occlusion of the renal artery to 3- and 7-month-old rats for 15 or 30 minutes. In an additional experiment IRI was applied to both kidneys for 20 min each in 2-3-month-old rats. Rats were then divided randomly into two groups of control and laser-treated. Laser therapy (Ga-Al-As 810 nm, 200 mW output for 2 min) was applied to the bone marrow 1 and 7 days post-IRI to the kidneys, and rats were sacrificed 2 weeks later. Histomorphometry and immunohistochemistry were performed on kidney sections and blood markers for kidney function. Quantitative histomorphometric analysis revealed a reduction in dilatation of the renal tubules, restored structural integrity of the renal tubules, and reduced necrosis in the laser-treated rats as compared to the control, non-laser-irradiated group. C-kit positive cell density in kidneys post-IRI and laser-treatment was significantly (p = 0.015) 3.2-fold higher compared to the control group. Creatinine and blood urea nitrogen content were significantly lower in the laser-treated rats as compared to control. It is concluded that LLLT application to the bone marrow (BM) causes a significant increase in the density of mesenchymal stem cells in the kidneys post-IRI, probably by induction of stem cells in the BM, which subsequently migrate to the IRI kidney, significantly reducing the pathological features of the kidney and increasing kidney function post IRI.

Effect of autologous mesenchymal stem cells induced by low level laser therapy on cardiogenesis in the infarcted area following myocardial infarction in rats

In this study, we investigated the hypothesis that photobiostimulation by low-energy laser therapy (LLLT) applied to the bone marrow (BM) of myocardial infarcted rats may attenuate the scarring processes that follow myocardial infarction (MI). Wistar rats underwent experimental MI. LLLT (Ga-Al-As diode laser) was applied to the BM of the exposed tibia at different time intervals post-MI (4 hrs, 48 hrs and 5 days). Sham-operated infarcted rats served as control. Infarct size was significantly reduced (55%) in the laser-treated rats as compared to the control non-treated rats, at 2 weeks post-MI. A significant 3-fold increase was observed in the density of desmin immunopositive stained cells 14 days post-MI in the infarcted area of the laser-treated rats as compared to the non-laser-treated controls. The electron microscopy from the control infarcted rat hearts revealed a typical interphase area between the intact myocardium and the infarcted area, with conspicuous fibroblasts with collagen deposition dispersed among them. In rats that were laser treated (to BM), the interphase zone demonstrated cells with different intracellular structures. There was also a significant increase in the percentage of c-kit positive cells and macrophages in the circulating blood of the laser treated rats as compared to control non treated ones. In the majority of the cells clusters of myofibrils anchored to well-developed Z-lines and structures resembling the morphological characteristics of mature intact cardiomyocytes were evident. In conclusion, LLLT to the BM of rats post-MI induces cardiogenesis mainly at the borders of the infarcted area in the heart.

Low-level laser treatment accelerated hair regrowth in a rat model of chemotherapy-induced alopecia (CIA)

Chemotherapy-induced alopecia (CIA) is one of the most distressing side effects of antineoplastic chemotherapy for which there is no effective interventional approach. A low-level laser (LLL) device, the HairMax LaserComb®, has been cleared by the FDA to treat androgenetic alopecia. Its effects may be extended to other settings; we have demonstrated that LaserComb treatment induced hair regrowth in a mouse model for alopecia areata. In the current study, we tested whether LLL treatment could promote hair regrowth in a rat model for CIA. Chemotherapy agents cyclophosphamide, etoposide, or a combination of cyclophosphamide and doxorubicin were administered in young rats to induce alopecia, with or without LLL treatment. As expected, 7-10 days later, all the rats developed full body alopecia. However, rats receiving laser treatment regrew hair 5 days earlier than rats receiving chemotherapy alone or sham laser treatment (with the laser turned off). The accelerated hair regrowth in laser-treated rats was confirmed by histology. In addition, LLL treatment did not provide local protection to subcutaneously injected Shay chloroleukemic cells. Taken together, our results demonstrated that LLL treatment significantly accelerated hair regrowth after CIA without compromising the efficacy of chemotherapy in our rat model. Our results suggest that LLL should be explored for the treatment of CIA in clinical trials because LLL devices for home use (such as the HairMax LaserComb®) provide a user-friendly and noninvasive approach that could be translated to increased patient compliance and improved efficacy.

Effect of Brimonidine on Retinal and Choroidal Neovascularization in a Mouse Model of Retinopathy of Prematurity and Laser-Treated Rats

To determine whether chronic treatment with brimonidine (BRI) attenuates retinal vascular leakage and neovascularization in neonatal mice after exposure to high oxygen in a mouse model of retinopathy of prematurity (ROP), and choroidal neovascularization (CNV) in rats after laser treatment. Experimental CNV was induced by laser treatment in Brown Norway (BN) rats. BRI or vehicle (VEH) was administered by osmotic minipumps, and CNV formation was measured 11 days after laser treatment. Oxygen-induced retinopathy was generated in neonatal mice by exposure to 75% oxygen from postnatal day (P)7 to P12. BRI or VEH was administered by gavage, and vitreoretinal vascular endothelial growth factor (VEGF) concentrations and retinal vascular leakage, neovascularization, and vaso-obliteration were measured on P17. Experimental CNV was induced in rabbits by subretinal lipopolysaccharide/fibroblast growth factor-2 injection. Systemic BRI treatment significantly attenuated laser-induced CNV formation in BN rats when initiated 3 days before or within 1 hour after laser treatment. BRI treatment initiated during exposure to high oxygen significantly attenuated vitreoretinal VEGF concentrations, retinal vascular leakage, and retinal neovascularization in P17 mice subjected to oxygen-induced retinopathy. Intravitreal treatment with BRI had no effect on CNV formation in a rabbit model of nonischemic angiogenesis. BRI treatment significantly attenuated vitreoretinal VEGF concentrations, retinal vascular leakage, and retinal and choroidal neovascularization in animal models of ROP and CNV. BRI may inhibit underlying event(s) of ischemia responsible for upregulation of vitreoretinal VEGF and thus reduce vascular leakage and retinal-choroidal neovascularization.

Induction of autologous mesenchymal stem cells in the bone marrow by low‐level laser therapy has profound beneficial effects on the infarcted rat heart

The adult mammalian heart is known to have a very limited regenerative capacity following acute ischemia. In this study we investigated the hypothesis that photobiostimulation of autologous bone-marrow-derived mesenchymal stem cells (MSCs) by low-level laser therapy (LLLT) applied to the bone marrow (BM), may migrate to the infarcted area and thus attenuate the scarring processes following myocardial infarction (MI). Sprague-Dawley rats underwent experimental MI. LLLT (Ga-Al-As diode laser, power density 10 mW/cm², for 100 seconds) was then applied to the BM of the exposed tibia at different time intervals post-MI (20 minutes and 4 hours). Sham-operated infarcted rats served as control. Infarct size and ventricular dilatation were significantly reduced (76% and 75%, respectively) in the laser-treated rats 20 minutes post-MI as compared to the control-non-treated rats at 3 weeks post-MI. There was also a significant 25-fold increase in cell density of c-kit+ cells in the infarcted area of the laser-treated rats (20 minutes post-MI) as compared to the non-laser-treated controls. The application of LLLT to autologous BM of rats post-MI offers a novel approach to induce BM-derived MSCs, which are consequently recruited from the circulation to the infarcted heart and markedly attenuate the scarring process post-MI.

Enhanced Liver Regeneration Following Acute Hepatectomy by Low-Level Laser Therapy

The aim of the present study was to investigate the effect of low-level laser therapy (LLLT) on liver regeneration following hepatectomy. LLLT has been found to modulate various biological processes. Twelve mature male rats were used. The liver was exposed, and 70% of it was excised. The rats were assigned randomly to two groups: control, non-laser treated, and experimental, laser-treated (diode [Ga-Al-As] laser 804 nm) group. For determination of newly formed blood vessels and proliferating cells, 5-Bromo-2'deoxyuridine (BrdU) was injected intraperitoneally. The rats were sacrificed 2 d post hepatectomy, and histological sections from each liver were processed for analysis of new blood-vessel formation using BrdU immunostaining kit. Mesenchymal stem cells (MSCs) were assessed using c-kit immunostaining. BrdU-labeled cells were counted as for estimation of newly formed hepatic cells. It was found that the number of proliferating cells (BrdU positive cells) per area in the regenerating regions of the livers were significantly (p < 0.01) 2.6-fold higher in the laser-treated rats than in the control non-laser-treated rats. The density of the newly formed blood vessels and c-kit immunopositive cells in the regenerating area of the laser-treated livers was significantly (p < 0.01) 3.3- and 2.3-fold respectively higher than the control non-laser treated livers. It is concluded that LLLT following acute hepatectomy most probably stimulates a significant enhancement of liver regeneration conducive to both the formation of new hepatocytes and MSCs and angiogenesis in the regenerating liver.

Long-Term Safety of Single and Multiple Infrared Transcranial Laser Treatments in Sprague–Dawley Rats

Growing interest exists in the use of near-infrared laser therapies for the treatment of numerous neurologic conditions, including acute ischemic stroke, traumatic brain injury, Parkinson's disease, and Alzheimer's disease. In consideration of these trends, the objective of this study was to evaluate the long-term safety of transcranial laser therapy with continuous-wave (CW) near-infrared laser light (wavelength, 808 ± 10 nm, 2-mm diameter) with a nominal radiant power of 70 mW; power density, 2,230 mW/cm(2), and energy density, 268 J/cm(2) at the scalp (10 mW/cm(2) and 1.2 J/cm(2) at the cerebral cortical surface) in healthy Sprague-Dawley rats. In this study, 120 anesthetized rats received sequential transcranial laser treatments to the right and left parietal areas of the head on the same day (minimum of 5 min between irradiation of each side), on either Day 1 or on each of Days 1, 3, and 5. Sixty anesthetized rats served as sham controls. Rats were evaluated 1 year after treatment for abnormalities in clinical hematology and brain and pituitary gland histopathology. No toxicologically important differences were found in the clinical hematology results between sham-control and laser-treated rats for any hematologic parameters examined. All values fell within historic control reference ranges for aged Sprague-Dawley rats. Similarly, brain and pituitary gland histopathology showed no treatment-related abnormalities or induced neoplasia. Single and multiple applications of transcranial laser therapy with 808-nm CW laser light at a nominal power density of 10 mW/cm(2) at the surface of the cerebral cortex appears to be safe in Sprague-Dawley rats 1 year after treatment.

Episcleral clearance of sodium fluorescein from a bioerodible sub-tenon's implant in the rat

We quantified episcleral drug clearance of sodium fluorescein (NaFl) in rats to examine the hypothesis that there is rapid clearance of episcleral water soluble drugs, and that this rapid clearance may limit the amount of drug that is able to reach the posterior segment from an episcleral location. 2 mm implants containing either 12 or 22 μg of NaFl were manufactured and in vitro release rates were determined. Implants were placed in the sub-Tenon's space and the amount of drug remaining in the conjunctiva/sclera/choroid complex (CSCC) at various time points was quantified following tissue solubilization and fluorescence quantification using a spectrofluorometer. Kinetics of NaFl clearance was determined in live animals, following euthanasia and in animals in which choroidal non-perfusion had been achieved with indocyanine green-enhanced 810 nm diode laser thrombosis of the choroidal vasculature. Choroidal non-perfusion in these laser-treated rats was verified with Concavalin-A staining of choroidal flatmounts. In vitro, >99% of drug was released by 25 min for the low dose implants, and by 60 min for the high dose implants. In vivo, both implant doses were >99% cleared from the episcleral tissue by 3 h. By 7 h, an average of only 0.14 ± 0.131 ng of NaFl per mg of wet tissue weight (mean ± SD) remained in the CSCC with the low dose implant, and 0.29 ± 0.428 ng of NaFl per mg of wet tissue weight remained in animals with the high dose implant. By comparison, in euthanized animals at 7 h following sub-Tenon's implantation, 432.0 ± 181.40 ng of NaFl per mg of wet tissue weight was in the episcleral tissue of animals with the low dose implant, and of 787.8 ± 409.89 ng of NaFl per mg of wet tissue weight remained in the animals with the high dose implant. In live animals with selective thrombosis of the choroidal vasculature, the difference in the amount of drug remaining in the episcleral tissue as compared to control live animals was not significant at all time points for both implant doses. In conclusion, there is rapid clearance of episcleral NaFl delivered from a bioerodible sub-tenon's implant. The clearance mechanisms are dramatically reduced following euthanasia, suggesting that elimination is occurring via active physiologic mechanisms, rather than by passive diffusion clearance (CL(diff)) ( Pfister et al., 2003). Interestingly, the choroid does not appear to play a prominent role as clearance of episcleral NaFl was not affected by elimination of choroidal blood flow. Further work is needed to delineate the pathways of episcleral drug clearance.

Effect of equal daily doses achieved by different power densities of low-level laser therapy at 635 nm on open skin wound healing in normal and corticosteroid-treated rats

Optimal parameters of low-level laser therapy (LLLT) for wound healing are still discussed. Hence, our study was aimed to compare effects of different power densities of LLLT at 635 nm in rats. Four, round, full-thickness, skin wounds were made on the backs of 48 rats that were divided into two groups (non-steroid laser-treated and steroid laser-treated). Three wounds were stimulated daily with a diode laser (daily dose 5 J/cm(2)) each with different power density (1 mW/cm(2), 5 mW/cm(2), and 15 mW/cm(2)), whereas the fourth wound served as a control. Two days, 6 days, and 14 days after surgery, eight animals from each group were killed and samples were removed for histological evaluation. In the non-steroid laser-treated rats, significant acceleration of epithelization and collagen synthesis 2 days and 6 days after surgery was observed in stimulated wounds. In steroid laser-treated rats, 2 days and 14 days after surgery, a decreased leucocyte/macrophage ratio and a reduction in the area of granulation tissue were recorded, respectively. In conclusion, LLLT, by the method we used, improved wound healing in the non-steroid laser-treated rats, but it was useless after corticosteroid treatment.

Growth factors in age-related macular degeneration: pathogenic and therapeutic implications.

To investigate the role of growth factors in choroidal neovascularization in humans with age-related macular degeneration (ARMD) and in rats with choroidal neovascularization produced by krypton laser photocoagulation. Autoradiography using 3H-thymidine in laser-treated rats. Light- and electron-microscopic immunocytochemistry using antibodies to several different growth factors and to the fibroblast growth factor (FGF) receptor. Tissues studied included the retinas of rats that had received krypton red laser photocoagulation, which induces formation of choroidal neovascularization 6-8 weeks after laser treatment, choroidal neovascular membranes (CNVMs) removed surgically from humans with ARMD and whole human eyes obtained postmortem with macular choroidal neovascular lesions from ARMD. Nuclei of retinal pigment epithelium (RPE) and choriocapillary cells in laser-treated rats were labeled with 3H-thymidine up to 80 days after photocoagulation, maximally at 2-7 days after laser treatment. At all intervals, RPE cells in treated areas immunolabeled for aFGF and bFGF. Labeling was strongest within lysosomes. RPE cells in untreated regions did not immunolabel for growth factors. RPE cells from CNVMs in the maculas of humans with ARMD also immunolabeled for aFGF and bFGF. Some choriocapillary endothelial cells in human CNVMs became labeled in a regular array along their anteluminal and luminal plasma membranes with anti-bFGF antibodies and, in a similar pattern, with antibodies to the FGF receptor. Finally, serial sections from some CNVMs in ARMD patients were immunostained alternately for bFGF and for vascular endothelial growth factor (VEGF). RPE cells and choriocapillary endothelial cells in these membranes immunostained for VEGF. Many immunostained for both bFGF and VEGF. In whole human eyes with macular CNVMs RPE cells in regions of normal retina did not immunostain for these growth factors. Several growth factors are not expressed at detectable levels by immunocytochemistry in normal RPE cells in rats or humans but do appear following photocoagulation or the development of CNVMs in ARMD. This suggests that these growth factors have a pathogenic role in choroidal neovascularization. Possibly, bFGF and VEGF act synergistically to accelerate neovascularization. The up-regulation of VEGF in CNVMs is of special interest because up-regulation of this growth factor in other systems appears to be stimulated by tissue hypoxia. Till now, hypoxia has not been considered a major pathogenic agent in the development of CNVMs in ARMD or other macular diseases.