Photobiomodulation Increases Viability in Full-Thickness Grafts in Rats Submitted to Nicotine.

BACKGROUND AND OBJECTIVES: Photobiomodulation (PBM) therapy with 830 nm wavelength or 660 wavelength to compare the effects with parameters of 30 mW, 0.028 cm2 , 9.34 seconds, and 3.64 J on the total integration of total skin grafts in rats submitted to nicotine. STUDY DESIGN/MATERIALS AND METHODS: Sixty male Wistar rats were divided in six groups: Sham-skin-grafting surgery; 830 nm-skin-grafting followed by 830 nm irradiation; 660 nm-skin grafting followed by 660 nm irradiation; Nicotine-subjected to subcutaneous nicotine injection (2 mg/kg twice a day for 4 weeks), followed by skin grafting; Group Nicotine/830 nm-similar to Group Nicotine, followed by 830 nm irradiation; Group Nicotine/660 nm-similar to Group Nicotine, followed by 660 nm irradiation. The percentage contraction of the grafting tissue was evaluated through ImageJ®. The thickness of the epidermis, inflammatory infiltrates, and the space between the implanted tissue and receptor bed were determined by histology; and the expression of vascular growth factor and blood vessel density (factor VIII) were evaluated by immunohistochemistry. RESULTS: The PBM at both wavelengths promoted a facilitating effect on the integration of the skin graft under nicotine and had a more significant effect on the thickness of the epidermis and expression of angiogenesis without nicotine at a wavelength of 830 nm. Different wavelengths influence responses related to the viability of cutaneous grafts in rats submitted to nicotine. CONCLUSIONS: The PBM with 830 nm and 660 nm promoted beneficial results in skin grafts submitted to the deleterious action of nicotine. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Histological assessment of non-ablative laser stimulation of tissue repair in acellular dermal grafts.

AIM: The objective of this study was to compare integration of AlloDerm® acellular dermal grafts in animals subjected to non-ablative laser irradiation and animals not exposed to this therapy. METHODS: Standardized AlloDerm® fragments measuring 5 mm² were grafted into the subcutaneous tissue overlying the calvaria in 32 Wistar rats. Laser therapy (685 ηm), at a dose of 4 J/cm2 per session, was applied immediately after surgical intervention and every 48 hours thereafter for a total of four applications. RESULTS: Analysis of histology slides revealed significantly greater edema in the control group. There was no neutrophil infiltration in the laser-irradiated group at any point during the study period, whereas such infiltration was present in control animals at three of the four points of observation. In the laser therapy group, lymphocyte infiltration was observed from day 1, whereas in the control group, it was only apparent from day 3. Vascularization was substantially greater in the control group. In the experimental group, the AlloDerm® graft was completely replaced by fibrous tissue. CONCLUSION: These findings suggest that add-on non-ablative laser therapy is an effective stimulator of healing and graft integration after placement of AlloDerm® acellular dermal grafts.

Influence of the use of laser phototherapy (lambda660 or 790 nm) on the survival of cutaneous flaps on diabetic rats.

OBJECTIVE: The aim of this study was to assess and compare the effects of laser phototherapy (LPT) on cutaneous flaps on diabetic rats. BACKGROUND: Diabetes mellitus is characterized by high blood glucose levels. Its main complications are delayed wound healing, an impaired blood supply, and a decrease in collagen production. Cutaneous flaps are routinely used in several surgical procedures, and most failures are related to poor blood supply. LPT has been studied using several healing models. ANIMALS AND METHODS: Twelve Wistar rats were randomized into three groups: group 1 (G1; diabetic animals without treatment), group 2 (G2; diabetic animals irradiated with lambda680 nm), and group 3 (G3; diabetic animals irradiated with lambda790 nm). Diabetes was induced with streptozotocin. A 2- x 8-cm cutaneous flap was raised on the dorsum of each animal, and a plastic sheet was introduced between the flap and the bed to cause poor blood supply. Nonirradiated animals acted as controls. The dose per session was 40 J/cm(2). Laser light was applied transcutaneously and fractioned on 16 contact points at the wound margins (16 x 2.5 J/cm(2)). Animal death occurred on day 8 after surgery. Specimens were taken, processed, cut, stained with eosin (HE) and sirius red, and underwent histological analysis. RESULTS: It is shown that accute inflammation was mostly discrete for G3. Chronic inflammation was more evident for G2. Fibroblast number was higher for G3. Angiogenesis was more evident for G3. Necrosis was more evident for G2. Statistical analysis among all groups showed significant differences (p = 0.04) on the level of acute inflammation between G1 and G3, tissue necrosis between G1 and G2 (p = 0.03), chronic inflammation between (p = 0.04), fibroblastic proliferation between G2 and G3 (p = 0.05), and neovascularization between G2 and G3 (p = 0.04). CONCLUSION: LPT was effective in increasing angiogenesis as seen on irradiated subjects and was more pronounced when IR laser light was used.

The effects of 660 nm and 780 nm laser irradiation on viability of random skin flap in rats.

BACKGROUND AND OBJECTIVE: Some studies have shown that laser phototherapy is able to increase skin flap viability by decreasing the necrotic area and increasing neoangiogenesis. However, the mechanism by which laser acts on cells is not fully understood. The present study investigated the effects of two different laser wavelengths at 30 and 40 J/cm(2) on the viability of skin flap in rats. MATERIAL AND METHODS: Sixty male animals were used in this study. They were distributed into the following groups (n = 12 each group): control group, group irradiated with 660 nm at 30 J/cm(2); group irradiated with 780 nm, at 30 J/cm(2), group irradiated with 660 nm at 40 J/cm(2); and group irradiated with 780 nm at 40 J/cm(2). The skin flap was performed on the back of all animals studied, with a plastic sheet interposed between the flap and the donor site. Laser irradiation was done immediately after the surgery and on days 1, 2, 3, and 4 post-surgery. The percentage of the necrotic area of the flap was calculated at day 7 post-surgery. RESULTS: Control group showed a necrotic area of 62.83%. Interestingly, no statistically significant differences were found among the treated groups and the control group. CONCLUSION: This present study showed that 660 nm and 780 nm lasers at doses of 30 and 40 J/cm(2) were not effective for decreasing the necrotic area of the skin flaps in rats.

Effect of low-level laser therapy on mast cells in viability of the transverse rectus abdominis musculocutaneous flap.

OBJECTIVE: To assess the effect of low-level laser therapy (LLLT) on viability of mast cells of the transverse rectus abdominis musculocutaneous (TRAM) flap. BACKGROUND DATA: LLLT has been recently used on the TRAM flap to stimulate mast cells. MATERIALS AND METHODS: Eighty-four Wistar rats were randomly divided into seven groups of 12 rats in each: group 1 (sham laser therapy); group 2 received 3 J/cm(2) at one point; group 3 received 3 J/cm(2) at 24 points; group 4 received 72 J/cm(2) at 1 point; group 5 received 6 J/cm(2) at 1 point; group 6 received 6 J/cm(2) at 24 points; and group 7 received 144 J/cm(2) at 1 point. All experimental groups underwent LLLT immediately after TRAM surgery and on the next two following days, for three sessions in total. The percentage of the area of skin flap necrosis was calculated on the fourth postoperative day and two samples of skin were collected from each rat with a 1-cm(2) punch to perform mast cell evaluations with toluidine blue dye. RESULTS: Statistically significant differences were found in the percentage of necrosis, and higher values were seen in group 1 than in all other groups. Among groups 3-7 no statistically significant differences were found (p < 0.292). For mast cells, when group 1 was compared to groups 5 (6 J/cm(2) at 1 point) and 7 (144 J/cm(2) at 1 point), it had fewer mast cells. CONCLUSION: LLLT at a wavelength of 670 nm was effective at reducing the necrotic area, and we found that it can stimulate mast cells growth to increase vascular perfusion.

Effect of application site of low-level laser therapy in random cutaneous flap viability in rats.

OBJECTIVE: This study aimed to investigate the effect of diode laser (830 nm) irradiation on the viability of ischemic random skin flaps in rats, as well as to determine the most effective site for applying laser radiation to speed healing. BACKGROUND DATA: Low-level laser therapy (LLLT) has recently been used to improve the viability of ischemic random skin flaps in rats. MATERIALS AND METHODS: Seventy Wistar rats were used and divided into seven groups of 10 rats each: group 1, sham laser treatment; group 2, which received irradiation at 1 point 5 cm from the flap's cranial base; group 3, which received irradiation at 2 points (5 and 7.5 cm from the flap's base); group 4, which received irradiation at 3 points (2.5, 5 and 7.5 cm from the flap's base); group 5, which received irradiation at 1 point 2.5 cm from the flap's base; group 6, which received irradiation at 2 points (2.5 and 5 cm from the flap's base); and group 7, which received irradiation at 1 point 7.5 cm from the flap's base. The animals were subjected to laser therapy at an energy density of 36 J/cm(2) for 72 sec immediately after surgery, and one time on each of the four subsequent days. The percentage of necrotic skin flap area was calculated on the seventh postoperative day using a paper template. RESULTS: The results showed that the rats in group 5 had the highest increase in skin flap viability, with a statistically significant difference compared to the other groups. Statistically significant differences were not seen between any of the other groups. CONCLUSION: The diode laser was effective in increasing skin flap viability in rats, and laser irradiation of a point 2.5 cm from the cranial base flap was found to be the most effective.

Depletion of donor-derived Langerhans cells promotes corneal allograft survival.

A mouse model of penetrating keratoplasty was used to evaluate the efficacy of ultraviolet radiation (UVR) and hyperbaric oxygen (HBO) treatments in depleting corneal Langerhans cells (LC) and promoting corneal allograft survival. The presence of donor-derived LC dramatically increased the immunogenicity and rejection rate of corneal allografts. Rejection increased from 40% in LC- corneal grafts to 80% in grafts containing donor-derived LC. Pretreatment with either HBO or UVR resulted in a sharp decrease in both the incidence and tempo of rejection for grafts containing donor LC, but neither procedure affected the fate of LC- corneal allografts. UVR-treatment abolished the immunogenicity of LC+ grafts. UVR-treated orthotopic grafts failed to elicit either cytotoxic T lymphocyte (CTL) or delayed-type hypersensitivity (DTH) responses that were any greater than naive control mice. The results suggest that purging corneal allografts of stray donor-derived LC might improve corneal allograft survival in high-risk patients without jeopardizing the functional integrity of the graft.

Influence of a transfusion of donor leukocytes treated with 8-methoxypsoralen and long-wave ultraviolet light (PUVA) on skin allograft survival in mice.

The influence of pretransplant donor spleen cell infusions on murine skin graft survival was studied. In dependence on the time interval between transplantation and transfusion an accelerated or delayed rejection of the grafts was observed. If the donor spleen cells were treated with the photosensitizer 8-methoxypsoralen and UVA light (PUVA) a graft prolongation was achieved at all time intervals. Furthermore, the survival of antigenically unrelated grafts was also prolonged. An additional immunosuppressive treatment or the recipients with antilymphocyte serum, but not cyclophosphamide, led to a further prolongation of graft survival. The survival of PUVA treated skin grafts was not longer in recipients preinfused with PUVA treated donor cells compared with untreated hosts. The results presented in this work may have implications in clinical organ transplantation to prevent sensitizing reactions by sparing protective mechanisms for the graft.

Reduced MHC class II antigen expression on rat heart and kidney cells after in vitro exposure to longwave ultraviolet irradiation.

The pretreatment of both kidney and heart donor with the photosensitizer 8-methoxy-psoralen followed by in vitro longwave ultraviolet graft irradiation (PUVA therapy) significantly prolonged graft survival times in rats even across a strong major histocompatibility complex (MHC) barrier. Immunohistological studies using monoclonal antibodies (Mab) to rat MHC class I and II antigens showed a significant reduction of class II antigen expression after PUVA therapy in both Sprague-Dawley rat kidneys and hearts. Using MHC class I Mab there were no differences in distribution pattern in untreated as well as in PUVA treated organs. Thus, our results represent the first in vivo evidence that photochemotherapy-induced graft survival time prolongation is closely connected with its ability to reduce MHC class II antigen expression.

Prolongation of the survival of skin grafts in mice by PUVA treatment.

The combined application of psoralen and UVA radiation to skin grafts induced a prolongation of the survival time of the grafts in mice. This was observed using the H-Y barrier, an allogeneic barrier without H-2 disparities, and a strong H-2 incompatible barrier. The effect is probably due to a reduction of antigen-presenting cells, or to other, unknown mechanisms.