Effects of low intensity laser irradiation during healing of infected skin wounds in the rat

Photodynamic therapy mediated by methylene blue-loaded PEG accelerates skin mouse wound healing: an immune response

PURPOSE

Conventional approaches for enhancing wound healing may not always yield satisfactory results. Instead, we test the effectiveness of a newly developed photodynamic therapy (PDT) that uses methylene blue (MB) loaded with polyethylene glycol (PEG) (MB-PEG) hydrogel to accelerate wound healing process in mice.

METHODS

A dorsal skin incision with 6 mm punch which topically subjected to MB-PEG hydrogel and a low-level laser light of red light to assess the regeneration process of wounded skin. A total of 63 adult male CD1 mice divided into normal group (no treatment) and other wound groups received different treatments of laser (650 ± 5 nm and power intensity of 180 mW/cm2), MB-PEG, or PDT (MB-PEG followed by laser). The wound healing parameters were investigated by histological examination of the skin and measuring of proinflammatory cytokines at the early stage (48 h) and a late one on day 21.

RESULTS

at 48 h, the score of tissue granulation, inflammation, and angiogenesis process were markedly improved in wounded groups that received MB + PEG combined with laser compared to the group treated with laser alone. On day 21, a significant improvement of the inflammation was detected in the group treated with MB + PEG plus laser compared to the other groups. At 48 h, the upregulated serum levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in the wound group were significantly (P < 0.001) reduced in the group treated with MB + PEG combined with laser.

CONCLUSION

MB-PEG based hydrogel improves and accelerates wound closure in the context of laser compared to either single treatment.

A novel investigational preclinical model to assess fluence rate for dental oral craniofacial tissues

OBJECTIVE

Photodynamic Therapy (PDT) and Photobiomodulation (PBM) are recognized for their potential in treating head and neck conditions. The heterogeneity of human tissue optical properties presents a challenge for effective dosimetry. The porcine mandible cadaver serves as an excellent model and has several similarities to human tissues of the dental oral craniofacial complex. This study aims to validate a novel modeling system that will help refine PDT and PBM dosimetry for the head and neck region.

METHODS AND MATERIALS

Light transmission was analyzed through several tissue combinations at distances of 2 mm to 10 mm. Maximum light fluence rates (mW/cm2) were compared across tissue types to reveal the effects of tissue heterogeneity.

RESULTS

The study revealed that light fluence is affected by tissue composition, with dentin/enamel showing reduced transmission and soft tissue regions exhibiting elevated values. The porcine model has proven to be efficient in mimicking human tissue responses to light, enabling the potential to optimize future protocols.

CONCLUSION

The porcine mandible cadaver is a novel model to understand the complex interactions between light and tissue. This study provides a foundation for future investigations into dosimetry optimization for PDT and PBM.

Pulsed low-intensity laser treatment stimulates wound healing without enhancing biofilm development in vitro

OBJECTIVES

Treating infected or chronic wounds burdened with biofilms still is a major challenge in medical care. Healing-stimulating factors lose their efficacy due to bacterial degradation, and antimicrobial substances negatively affect dermal cells. Therefore, alternative treatment approaches like the pulsed low intensity laser therapy (LILT) require consideration.

METHODS

The effect of pulsed LILT (904 nm, in three frequencies) on relevant human cells of the wound healing process (fibroblasts (BJ), keratinocytes (HaCaT), endothelial cells (HMEC), monocytes (THP-1)) were investigated in in-vitro and ex-vivo wound models with respect to viability, proliferation and migration. Antimicrobial efficacy of the most efficient frequency in cell biological analyses of LILT (3200 Hz) was determined in a human biofilm model (lhBIOM). Quantification of bacterial load was evaluated by suspension method and qualitative visualization was performed by scanning electron microscopy (SEM).

RESULTS

Pulsed LILT at 904 nm at 3200 Hz ± 50% showed the most positive effects on metabolic activity and proliferation of human wound cells in vitro (after 72 h - BJ: BPT 0.97 ± 0.05 vs. 0.75 ± 0.04 (p = 0.0283); HaCaT: BPT 0.79 ± 0.04 vs. 0.59 ± 0.02 (p = 0.0106); HMEC: 0.74 ± 0.02 vs. 0.52 ± 0.04 (p = 0.009); THP-1: 0.58 ± 0.01 vs. 0.64 ± 0.01 (p > 0.05) and ex vivo. Interestingly, re-epithelialization was stimulated in a frequency-independent manner. The inhibition of metabolic activity after TNF-α application was abolished after laser treatment. No impact of LILT on monocytes was detected. Likewise, the tested LILT regimens showed no growth rate reducing effects on three bacterial strains (after 72 h - PA: -1.03%; SA: -0.02%; EF: -1,89%) and one fungal (-2.06%) biofilm producing species compared to the respective untreated control. Accordingly, no significant morphological changes of the biofilms were observed after LILT treatment in the SEM.

CONCLUSIONS

Frequent application of LILT (904 nm, 3200 Hz) seems to be beneficial for the metabolism of human dermal cells during wound healing. Considering this, the lack of disturbance of the behavior of the immune cells and no growth-inducing effect on bacteria and fungi in the biofilm can be assigned as rather positive. Based on this combined mode of action, LILT may be an option for hard to heal wounds infected with persistent biofilms.

Healing Process of Rat Skin Wounds Treated With Vitamin C and Low-Intensity Laser Therapy

Introduction: This study evaluated, from a histological point of view, the process of repairing skin wounds caused in the dorsal region of rats when subjected to treatment with vitamin C, low-intensity laser, and association of both.

Methods: Forty-eight adult male rats (Rattus norvegicus, albinus, Wistar), weighing between 250 and 300 g were used in this study. The rats were anesthetized with sodium pentobarbital (10 mg/kg) intraperitoneally (IP) and a circular area of ​​skin of approximately 8 mm in diameter was removed from the dorsal region of their back by a punch. The animals were randomly divided into four groups of 12 individuals: Group I, control group, was treated with saline solution; Group II was treated with topical application of vitamin C; Group III was treated with low-intensity laser; and Group IV was treated with both low-intensity laser and topical application of vitamin C. Samples were histologically analyzed through optical microscopy with hematoxylin and eosin staining and collagen I and III concentrations were quantified using the picrosirius-hematoxylin histochemical method and further submitted to statistical analysis.

Results: Whilst the control and vitamin C groups admittedly showed slight epithelial proliferation at the wound edges, the group irradiated with low-intensity laser and the group treated with both laser and vitamin C had already partially formed epidermis, with a more organized underlying connective tissue and less evident inflammatory process. The group treated with laser alone obtained a higher concentration of type I collagen fibers and the group with the highest amount of type III collagen fibers was the one treated with the association of vitamin C and laser.

Conclusion: The present findings suggest that in spite of all treatments being effective in the repair of skin wounds compared to the control group, the isolated use of low-intensity therapy laser and its combined use with topical vitamin C showed the most favorable results, indicating that those could be further used for the treatment of skin wounds.

In Vitro Evidences of Different Fibroblast Morpho-Functional Responses to Red, Near-Infrared and Violet-Blue Photobiomodulation: Clues for Addressing Wound Healing

Although photobiomodulation (PBM) has proven promising to treat wounds, the lack of univocal guidelines and of a thorough understanding of light–tissue interactions hampers its mainstream adoption for wound healing promotion. This study compared murine and human fibroblast responses to PBM by red (635 ± 5 nm), near-infrared (NIR, 808 ± 1 nm), and violet-blue (405 ± 5 nm) light (0.4 J/cm2 energy density, 13 mW/cm2 power density). Cell viability was not altered by PBM treatments. Light and confocal laser scanning microscopy and biochemical analyses showed, in red PBM irradiated cells: F-actin assembly reduction, up-regulated expression of Ki67 proliferation marker and of vinculin in focal adhesions, type-1 collagen down-regulation, matrix metalloproteinase-2 and metalloproteinase-9 expression/functionality increase concomitant to their inhibitors (TIMP-1 and TIMP-2) decrease. Violet-blue and even more NIR PBM stimulated collagen expression/deposition and, likely, cell differentiation towards (proto)myofibroblast phenotype. Indeed, these cells exhibited a higher polygonal surface area, stress fiber-like structures, increased vinculin- and phospho-focal adhesion kinase-rich clusters and α-smooth muscle actin. This study may provide the experimental groundwork to support red, NIR, and violet-blue PBM as potential options to promote proliferative and matrix remodeling/maturation phases of wound healing, targeting fibroblasts, and to suggest the use of combined PBM treatments in the wound management setting.

Effect of Photobiomodulation Therapy (660 nm) on Wound Healing of Rat Skin Infected by Staphylococcus

Objective: To assess the impact of photobiomodulation (PBM) therapy on healing of infected wounds and document the microscopic findings throughout the recovery process. Background: Previous studies have suggested that PBM accelerates wound healing and reduces inflammation and pain. However, the ideal protocol and ultimate value of PBM treatment for infected wounds are controversial. Materials and methods: Eight-month-old male rats were randomly divided into the control group, the nonirradiation group, or the irradiation group. A 1 cm diameter skin excision was made. The wounds of the nonirradiated and irradiated rats were inoculated with a suspension of Staphylococcus aureus. We then performed 7 days of PBM therapy at a wavelength of 660 nm for 35 min/day. On day 8, the rats were sacrificed for histological assessment. Sections were stained with hematoxylin and eosin, Masson trichrome, and a proliferating cell nuclear antigen (PCNA) kit. Defect diameter was calculated using the Visus Image Analysis System. Results: The irradiated group had more epithelial cells and richer granulation tissue compared to those in the other groups. The irradiation group had a significantly smaller defect size than the nonirradiation group (p < 0.01) and the control group (p < 0.05). The amount of collagen was highest in the irradiation group and was graded as 3, 2, and 3+ in the control, nonirradiation, and irradiation groups, respectively. The percentage of PCNA in the control group was significantly lower than that in the other two groups (p < 0.05). Conclusions: PBM therapy (660 nm) promoted cell proliferation and collagen synthesis, thereby improving the wound healing response to an S. aureus infection.

Comparison of Anti-Microbial Effects of Low-Level Laser Irradiation and Microwave Diathermy on Gram-Positive and Gram-Negative Bacteria in an In Vitro Model

Background and Objectives: The aim of this study was to compare the effects of low-level laser therapy and continuous microwave diathermy on the growth of Gram-negative and Gram-positive bacteria and to establish their efficacy as an alternative therapeutic modality.

MATERIALS AND METHODS

Laser fluence of 13 Joules (J)/cm², 18 J/cm² and 30 J/cm² were used against several bacterial strains. Microwave dosages of 25, 50 and 100 watts (W) were used, respectively.

RESULTS

A significant difference between the three groups was observed using repeated analysis of variance (RANOVA) (F value: 0.74, and p value: 0.001). The Greenhouse-Geisser correction (GG) revealed significant results for laser irradiation alone. However, effect size calculation showed effects with microwave diathermy as well as laser fluence.

CONCLUSIONS

Low-level laser therapy appears to be an effective modality of treatment when compared with continuous microwave diathermy on the Gram-negative and the Gram-positive bacterial strains tested. Microwave diathermy revealed large and medium effects on the bacterial cell counts with dominant effects on Gram-negative strains.

Improvement in infected wound healing in type 1 diabetic rat by the synergistic effect of photobiomodulation therapy and conditioned medium

We investigated the effects of photobiomodulation therapy (PBMT) and conditioned medium (CM) of human bone marrow mesenchymal stem cells (hBM-MSC) individually and/or in combination on the stereological parameters and the expression of basic fibroblast growth factor (bFGF), hypoxia-inducible factor (HIF-1α), and stromal cell-derived factor-1α (SDF-1α) in a wound model infected with methicillin-resistant Staphylococcus aureus (MRSA) in diabetic rats. CM was provided by culturing hBM-MSCs. Type 1 diabetes mellitus (T1DM) was induced in 72 rats, divided into four groups, harboring 18 rats each: group 1 served as a control group, group 2 received PBMT, group 3 received CM, and group 4 received CM + PBMT. On days 4, 7, and 15, six animals from each group were euthanized and the skin samples were separated for stereology examination and gene expression analysis by real-time polymerase chain reaction. In the CM + PBMT, CM, and PBMT groups, significant decreases were induced in the number of neutrophils (1460 ± 93, 1854 ± 138, 1719 ± 248) and macrophages (539 ± 69, 804 ± 63, 912 ± 41), and significant increases in the number of fibroblasts (1073 ± 116, 836 ± 75, 912 ± 41) and angiogenesis (15 230 ± 516, 13 318 ± 1116, 14 041 ± 867), compared with those of the control group (2690 ± 371, 1139 ± 145, 566 ± 90, 12 585 ± 1219). Interestingly, the findings of the stereological examination in the CM + PBMT group were statistically more significant than those in the other groups. In the PBMT group, in most cases, the expression of bFGF, HIF-1α, and SDF-1α, on day 4 (27.7 ± 0.14, 28.8 ± 0.52, 27.5 ± 0.54) and day 7 (26.8 ± 1.4, 29.6 ± 1.4, 28.3 ± 1.2) were more significant than those in the control (day 4, 19.3 ± 0.42, 25.5 ± 0.08, 22.6 ± 0.04; day 7, 22.3 ± 0.22, 28.3 ± 0.59, 24.3 ± 0.19) and other treatment groups. The application of PBMT + CM induced anti-inflammatory and angiogenic activities, and hastened wound healing process in a T1 DM model of MRSA infected wound.

Laser parameters for efficient biomedical stimulation: A study to increase cognitive response rate

BACKGROUND:

The laser is able to irradiate the exact amount of stimulation to an area by a non contact method, and has the advantage of being able to stimulate the local target area.

OBJECTIVE:

This study examined an efficient method of laser tactile stimulation using laser parameter combinations.

METHODS:

The laser parameters that could cause an increase in the cognitive response rate of human subjects were examined without increasing the amount of total laser energy.

RESULTS:

As a result, the appropriate matching parameters such as duty ratio, pulse frequency, and exposure time of laser pulses showed a dominant influence in effectively increasing the tactile response rate of subjects with limited amount of total laser energy.

CONCLUSIONS:

This study can be applied to neurophysiology, cognitive research, and clinical laser application.

Low-intensity laser therapy efficacy evaluation in FVB mice subjected to acute and chronic arthritis

Rheumatoid arthritis, an autoimmune inflammation, has a high prevalence in the population, and while therapy is available, it required often injection of drugs causing discomfort to patients. This study evaluates the clinical and histological effect of low-intensity laser therapy (LILT) as an alternative treatment, in a murine model of acute and chronic inflammation. FVB mice received either a Zymosan A injection into one knee joint inducing acute inflammation, followed after 15 min or 24 h by LILT or a collagen bovine type II injection emulsified in "Freund's Complete Adjuvant" to induce chronic arthritis, followed at 4 weeks with multiple LILT sessions. LILT mediated by either 660, 808, or 905 nm and tissue response was evaluated based on clinical symptoms and histological analysis of inflammatory infiltrate and damage to the articular surfaces. LILT can be effective in elevating clinical symptoms, so Kruskal-Wallis testing indicated no significant differences between knees affected by acute arthritis and treated once with LILT and an injured knee without treatment (p > 0.05) for 660 and 808 nm with some improvements for the 905-nm LILT. Mice receiving two treatments for acute arthritis showed exacerbation of inflammation and articular resorption following therapy with a 660-nm continuous laser (p < 0.05). For chronic inflammation, differences were not noted between LILT treated and untreated injured knee joints (p > 0.05). Among the lasers, the 905 nm tends to show better results for anti-inflammatory effect in acute arthritis, and the 660 nm showed better results in chronic arthritis. In conclusion, LILT wavelength selection depends on the arthritis condition and can demonstrate anti-inflammatory effects for chronic arthritis and reduced resorption area in this murine model.

The effect of combined photobiomodulation and metformin on open skin wound healing in a non-genetic model of type II diabetes

This study intended to examine the combined influences of photobiomodulation (PBM) and metformin on the microbial flora and biomechanical parameters of wounds in a non-genetic model of type II diabetes mellitus (TII DM). We induced a non-genetic model of TII DM in 20 rats by feeding them a 10% fructose solution for 2weeks followed by an injection of streptozotocin (STZ, 40mg/kg). After 21days from the injection of STZ, we induced one full-thickness skin wound in each of the diabetic rats. We randomly divided the rats into four groups: i) placebo; ii) pulsed wave laser (890nm, 80Hz, 0.324J/cm²); iii) metformin; and iv) laser+metformin. Rats received daily intraperitoneal injections of metformin (50mg/kg). On days 7and 15 we inspected the microbial flora of each wound. On day 15 we obtained a standard sample from each healing wound for biomechanical analyses. PBM significantly decreased colony-forming units (CFUs) 7days after wound infliction compared to the placebo group (LSD test, p=0.012). Metformin significantly enhanced the biomechanical property (stress high load) of the wounds compared to the placebo group (LSD test, p=0.028). We observed the same significant result for PBM compared to the placebo group (LSD test, p=0.047). PBM significantly accelerated the wound healing process and significantly reduced CFUs of bacteria in a non-genetic rat model of TII DM.