Therapeutic efficacy of early photobiomodulation therapy on the zones of stasis in burns: An experimental rat model study

Photobiomodulation in Burn Wounds: A Systematic Review and Meta-Analysis of Clinical and Preclinical Studies

Objective: This systematic review and meta-analysis main goal was to evaluate the efficacy of photobiomodulation as burn wounds treatment. Methods: Systematic review of literature available in databases such as PubMed, Web of Science, Embase, Latin American and Caribbean Health Sciences Literature (LILACS), and The Cumulative Index to Nursing and Allied Health Literature (CINAHL) and gray literature in Google Scholar, Livivi, and Open Gray. SYRCLE's RoB tool was applied to determine methodological quality and risk of bias, and meta-analysis was performed using the software Review Manager. Results: Fifty-one studies, gathering more than three thousand animals were included in this systematic review, and four studies were selected to the meta-analysis due to their suitability. The results indicated that photobiomodulation was not effective to improve, statistical significantly, wound retraction (SMD = -0.22; 95% CI = -4.19, 3.75; p = 0.91; I2 = 92%) or collagen deposition (SMD = -0.02; 95% CI = -2.17, 2.13; p = 0.99; I2 = 78%). Conclusion: This meta-analysis suggests that photobiomodulation, applied in burn wounds, accordingly to the protocols presented by the selected studies, was not effective over analyzed outcomes. However, this conclusion could be further discussed and verified in more homogeneous animal models and human clinical trials.

Development of a Wound Epithelialization Healing Model: Reducing the Impact of Contraction Healing on the Wound Surface

Animal experiments are important in trauma-related studies because they simulate in vivo effects. Rodents are a good choice for preparing trauma models; however, contractile healing in rodents results in a healing pattern that differs considerably from that in humans. Therefore, this study developed a new rodent model that avoids contractile healing of the skin around the wound using an anticontraction ring, and the skin in the wound's center remains intact and acts as a source for epithelialized diffusion healing. Cell proliferation, migration, revascularization, and collagen secretion did not differ between the novel and conventional full-skin defect trauma models. However, the healing rate at various stages significantly differed between the 2 groups owing to differences in the healing patterns. And without effective treatment, the experimental group cannot heal. The stabilities of the novel and conventional methods were good regardless of operator or batch. In summary, this new animal trauma model provides a stable experimental environment similar to that in humans, which may promote trauma-related research.

Determining transfusion use in major burn patients: A retrospective review and analysis from 2009 to 2019

Blood transfusion is an important treatment for patients with major burns. Understanding the predictive factors of blood product usage in major burns can improve effective transfusion therapy. We retrospectively reviewed the medical records of the Burn Center, First Affiliated Hospital of the Chinese Naval Military Medical University, from August 2009 to July 2019 and enrolled all patients with major burns treated in that decade. Basic information, condition, and blood-transfusion details of the patients were analyzed to identify predictive factors for blood use and prognosis. Despite a yearly decreasing trend, the frequency of use of blood-product usage in major burns was high at 57.72%, with 5.39 times and 28.76 units of blood usage per person. Burn area was the most important predictive factor for blood transfusion at different stages. Burn depth, combined with injury, age, and other factors, affected blood use. Blood use or volume correlated with prognosis; especially, platelet and cryoprecipitate use was significantly associated with increased mortality. Blood product usage in major burns patients is related not only to the clinical condition, but also to doctors' experience, which can predict prognosis. Blood use is associated with increased mortality, although we found no evidence of a causal association.

Nestin and NG2 transgenes reveal two populations of perivascular cells stimulated by photobiomodulation

Pericytes and glial cells are known to collaborate in dental pulp tissue repair. Cell-based therapies that stimulate these stromal components may be of therapeutic relevance for partially vital dental pulp conditions. This study aimed to examine the early effect of photobiomodulation (PBM) in pericytes from experimentally injured pulp tissue. To accomplish this, we used the Nestin-GFP/NG2-DsRed mice, which could allow the identification of distinct pericyte phenotypes. We discovered the presence of two pericytes subsets within the dental pulp, the Nestin ⁺ NG2⁺ (type-2) and Nestin^- NG2⁺ (type-1). Upon injury, PBM treatment led to a significant increase in Nestin⁺ cells and pericytes. This boost was mainly conferred by the more committed pericyte subset (NestinNG2⁺ ). PBM also stimulated terminal blood vessels sprouting adjacent to the injury site while maintaining signs of pulp vitality. In vitro, PBM induced VEGF upregulation, improved dental pulp cells proliferation and migration, and favored their mineralization potential. Herein, different subsets of perivascular cells were unveiled in the pulp tissue. PBM enhanced not only NG2⁺ cells but nestin-expressing progenitors in the injured dental pulp.

Modeling Burn Progression Using Comb Burns: The Impact of Thermal Contact Duration on Model Outcomes

BACKGROUND

Burn progression is a phenomenon that remains poorly characterized. The mechanisms of burn conversion are not completely understood, and consequently, both predictive diagnostic tools and interventions are limited. The rat comb burn model is a commonly used approach to study horizontal burn conversion. However, there is significant variability in how the model is performed. Skin contact duration, comb device heating method, comb heating duration, amount of pressure applied, the weight of the comb, and associated depth of burn are all variables that are heterogeneous in studies utilizing the model.

MATERIALS AND METHODS

Here, contact duration was examined to determine the impact the duration of burn delivery has on the conversion of interspaces in this model. Data from multiple experiments consisting of 10, 15, 20, 30, 40, and 45 s comb burns were compiled and assessed. Burns were made using combs heated in a 100°C dry bath and then monitored for 2 d. Interspace viability was assessed by digital and laser doppler imaging and biopsy procurement.

RESULTS

Laser Doppler Imaging and viable interspace measurements showed that as burn duration increased, the percentage of the viable interspace and interspace perfusion decreased. Additionally, a contact time of 30 s or greater was required to result in 100% interspace conversion.

CONCLUSIONS

These results demonstrate a need to better characterize and potentially standardize the rat comb burn model to reduce variation and maintain it as a valuable tool for controlled studies of the pathophysiology of burn wound progression.

Photobiomodulation drives pericyte mobilization towards skin regeneration

Photobiomodulation is being widely applied for improving dermal or mucosal wound healing. However, the underlying cellular and molecular processes that directly contribute to its effects remain poorly understood. Pericytes are relevant cells involved in the wound microenvironment and could be one of the main targets of photobiomodulation due to their plasticity and perivascular localization. Herein, we investigate tissue repair under the photobiomodulation stimulus using a pericyte labeled (or reporter) transgenic mice. Using a model of two contralateral back wounds, one the control and the other photoactivated daily (660 nm, 20 mW, 0.71 W/cm2, 5 J/cm2, 7 s, 0.14 J), we showed an overall influx of immune and undifferentiated cells and higher mobilization of a potent pericyte subpopulation (Type-2 pericytes) in the photoactivated wounds in comparison to the controls. Doppler analysis showed a significant increase in the blood flow in the photoactivated wounds, while marked vascular supply was observed histologically. Histochemical analysis has indicated more advanced stages of tissue repair after photoactivation. These data suggest that photobiomodulation significantly accelerates tissue repair through its vascular effects with direct recruitment of pericytes to the injury site.

Modification and utility of a rat burn wound model

This study aimed to improve the conventional rat burn wound model and to validate its utility. In total, 60 Sprague-Dawley rats were divided equally into the control and experimental groups. Altogether, 60 burn wound models with zones of stasis were created in each group. Gross visual assessments of the burn wounds were performed at 0, 24, and 48 hours after burn creation. The rates of necrosis in the zones of stasis were calculated, and the blood flow from the wounds was examined. Wound tissues were collected 48 hours after the burn and subjected to hematoxylin and eosin staining to determine whether the models were successfully established. The model success rates were calculated. The success rate of the burn wound models was significantly different between the control group and the experimental group (93.33% [56/60] vs 100%; P = .042). The Cronbach's alpha values and the respective correlation coefficients indicated that the stability of the zones of stasis in the models on the two sides of the spine was higher in the experimental group than in the control group. The standard deviations of the rate of necrosis, blood flow, and density of necrotic cells and apoptosis cell density, and inflammatory factor content in the zones of stasis were smaller in the experimental group than in the control group at 48 hours after model construction. This suggested that the stability of repeated procedures was higher in the experimental group than in the control group. The novel device for creating burns in animal models facilitated the effective creation of zones of stasis for rat burn wound models. Both the model success rate and stability were higher compared with the conventional model construction method. In addition, the use of the novel device can better align with the requirements of self-controlled studies.

Effects of Pulsed 810 nm Al-Ga-As Diode Laser on Wound Healing Under Immunosuppression: A Molecular Insight

BACKGROUND AND OBJECTIVES

Dysregulated inflammation is one of the major contributing factors for the prevalence of non-healing chronic wound in immunosuppressed subjects. Photobiomodulation (PBM) has emerged as a potential non-thermal, light-based therapeutic healing intervention for the treatment of impaired wounds.

STUDY DESIGN/MATERIALS AND METHODS

The present study delineates the underlying molecular mechanisms of PBM 810 nm laser-induced full-thickness cutaneous wound repair in immunosuppressed rats at continuous and pulsed wave-mode with power-density of 40 mW/cm ² , fluence 22.6 J/cm ² for 10 minutes daily for 7 post-wounding days. Molecular markers were assessed using biochemical, enzyme-linked immunosorbent assay quantification, enzyme kinetics and immunoblots analyses pertaining to inflammation, oxidative stress, cell survival, calcium signaling, and proliferation cascades.

RESULTS

Results distinctly revealed that pulsed 810 nm (10 Hz) PBM potentially influenced the cell survival and proliferation signaling pathway by significantly upregulated phospho-protein kinase B(phospho-Akt), phospho-extracellular-signal-regulated kinase 1 (ERK1), transient receptor potential vanilloid-3 (TRPV3), Ca²⁺ , calmodulin, transforming growth factor-β1 (TGF-β1), TGF-βR3, and Na ⁺ /K ⁺ -ATPase pump levels. PBM treatment resulted in reduction of exaggerated inflammatory responses evident by significantly repressed levels of interleukin-1β (IL-1β), IL-6, cyclooxygenase 2 (COX-2), and substance-P receptor (SPR), as well as inhibited apoptotic cell death by decreasing p53, cytochrome C, and caspase 3 levels (P < 0.05), which, in turn, effectively augment the wound repair in immunosuppressed rats. PBM treatment also lowered 4-hydroxynoneal (HNE) adduct level and NADP/NADPH ratio and upregulated the GRP78 expression, which might culminate into reduced oxidative stress and maintained the redox homeostasis.

CONCLUSIONS

Taken together, these findings would be helpful in better understanding of the molecular aspects involved in pulsed 810 nm laser-mediated dermal wound healing in immunosuppressed rats through regulation of cell survival and proliferation via Ca²⁺ -calmodulin, Akt, ERK, and redox signaling. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.