Effect of laser therapy on immune cells infiltrate after excisional wounds in diabetic rats.

BACKGROUND AND OBJECTIVE: Diabetes alters innate and specific immunity, causing an imbalanced tissue repair process. Very active neutrophils and macrophages are found for a long time in chronic wounds in those individuals. The aim of this study was to evaluate the response of the main effector cells of immunity (neutrophils, macrophages, and T lymphocytes) and to compare the effects of two laser therapy regimens in the postoperative treatment of excision wounds. METHOD: Diabetes was induced in female Wistar rats and a punch was used to cause wounds in the dorsum of each individual. The animals were randomly allocated to a control group (CG), in which the wound was untreated, a single-dose laser group (SLG), in which the wound was submitted to single dose of laser therapy at wavelength of 660 nm, output power of 30 mW, energy density of 4 J/cm(2), and 26-second exposure time, and a fractionated-dose laser group (FLG), submitted to 1 J/cm(2) of laser therapy on Days 1, 3, 8, and 10. Euthanasia was performed on five animals from each group Days 1, 3, 8, 10, 15, and 22. The wound was removed and routinely processed for immunohistochemistry against elastase, CD3, CD68, and CD206 antibodies. The samples were photographed and labeled cells were counted by a blinded observer. The Kruskal-Wallis test was used for the statistical analysis. RESULTS: Neutrophils were predominant in the SLG on Day 1, whereas these cells were mostly found in the CG on Day 3 (P < 0.05). The T lymphocyte count was similar in all groups in the throughout the experiment. On Day 3, the SLG exhibited a greater number of total macrophages (CD68+) (P < 0.05), whereas the macrophage count was similar among the different groups on the other evaluation days. The CD206 + cell counts revealed that the SLG had more M2 macrophages than the CG on Day 8 (P < 0.05), whereas the FLG exhibited more M2 macrophages than the CG on Day 10 (P < 0.05). CONCLUSION: The present findings demonstrate that laser therapy can alter the composition of inflammatory infiltrate in diabetic wounds, leading to a more balanced response transiting from a rapid neutrophil infiltration through to M2 macrophage polarization, especially with a single application of 4 J/cm(2) in the immediate postoperative period.

Tissue responses to postoperative laser therapy in diabetic rats submitted to excisional wounds.

In a previous study about low-level laser therapy biomodulation on a full-thickness burn model we showed that single and fractionated dose regimens increased wound healing and leukocyte influx similarly when compared with untreated control. In order to verify if this finding would be similar in an impaired wound model, we investigated the effect of single and multiple irradiations on wound closure rate, type of inflammatory infiltrate, myofibroblasts, collagen deposition, and optical retardation of collagen in diabetic rats. Female Wistar rats in the same estrous cycle had diabetes induced with streptozotocin and an 8-mm excisional wound performed with a punch. The experimental groups were: control group--untreated ulcer; single-dose group--ulcer submitted to single dose of diode laser therapy (λ = 660 ± 2 nm; P = 30 mW; energy density: 4 J/cm2) and fractionated-dose group--ulcer submitted to 1 J/cm2 laser therapy on Days 1, 3, 8, and 10. The ulcers were photographed on the experimental days and after euthanasia tissue samples were routinely processed for histological and immunohistochemistry analyses. Independently of the energy density, laser therapy accelerated wound closure by approximately 40% in the first three days in comparison to the control group. Laser therapy increased acute inflammatory infiltrate until Day 3. Both laser groups exhibited more myofibroblasts and better collagen organization than the control group. The findings demonstrate that low-level laser therapy in the immediate postoperative period can enhance the tissue repair process in a diabetes model. Similar effects were achieved with laser therapy applied a single time with an energy density of 4 J/cm2 and applied four times with an energy density of 1 J/cm2. The application of laser therapy in the inflammatory phase was the most important factor to the enhancement of the tissue repair process.

Effect of laser therapy on skeletal muscle repair process in diabetic rats.

Skeletal muscle myopathy is a common source of disability in diabetic patients. This study evaluated whether low-level laser therapy (LLLT) influences the healing morphology of injured skeletal muscle. Sixty-five male Wistar rats were divided as follows: (1) sham; (2) control; (3) diabetic; (4) diabetic sham; (5) nondiabetic cryoinjured submitted to LLLT (LLLT); (6) diabetic cryoinjured submitted to LLLT (D-LLLT); and (7) diabetic cryoinjured non-treated (D). Diabetes was induced with streptozotocin. Anterior tibialis muscle was cryoinjured and received LLLT daily (780 nm, 5 J/cm(2), 10 s per point; 0.2 J; total treatment, 1.6 J). Euthanasia occurred on day 1 in groups 1, 2, 3, and 4 and on days 1, 7, and 14 in groups 5, 6, and 7. Muscle samples were processed for H&E and Picrosirius Red and photographed. Leukocytes, myonecrosis, fibrosis, and immature fibers were manually quantified using the ImageJ software. On day 1, all cryoinjured groups were in the inflammatory phase. The D group exhibited more myonecrosis than LLLT group (p < 0.05). On day 14, the LLLT group was in the remodeling phase; the D group was still in the proliferative phase, with fibrosis, chronic inflammation, and granulation tissue; and the D-LLLT group was in an intermediary state in relation to the two previous groups. Under polarized light, on day 14, the LLLT and D-LLLT groups had organized collagen bundles in the perimysium, whereas the diabetic groups exhibited fibrosis. LLLT can have a positive effect on the morphology of skeletal muscle during the tissue repair process by enhancing the reorganization of myofibers and the perimysium, reducing fibrosis.