Comparative Study of 1,064-nm Laser-Induced Skin Burn and Thermal Skin Burn

A Preliminary Study on Quantitative Analysis of Collagen and Apoptosis Related Protein on 1064 nm Laser-Induced Skin Injury

To investigate the associated factors concerning collagen and the expression of apoptosis-related proteins in porcine skin injuries induced by laser exposure, live pig skin was irradiated at multiple spots one time, using a grid-array method with a 1064 nm laser at different power outputs. The healing process of the laser-treated areas, alterations in collagen structure, and changes in apoptosis were continuously observed and analyzed from 6 h to 28 days post-irradiation. On the 28th day following exposure, wound contraction and recovery were notably sluggish in the medium-high dose group, displaying more premature and delicate type III collagen within the newly regenerated tissues. The collagen density in these groups was roughly 37-58% of that in the normal group. Between days 14 and 28 after irradiation, there was a substantial rise in apoptotic cell count in the forming epidermis and granulation tissue of the medium-high dose group, in contrast to the normal group. Notably, the expression of proapoptotic proteins Bax, caspase-3, and caspase-9 surged significantly 14 days after irradiation in the medium-high dose group and persisted at elevated levels on the 28th day. During the later stage of wound healing, augmented apoptotic cell population and insufficient collagen generation in the newly generated skin tissue of the medium-high dose group were closely associated with delayed wound recovery.

Skin Thermal Management for Subcutaneous Photoelectric Conversion Reaching 500 mW

Despite possessing higher tissue transmittance and maximum permissible exposure power density for skin relative to other electromagnetic waves, second near-infrared light (1000-1350 nm) is scarcely applicable to subcutaneous photoelectric conversion, owing to the companion photothermal effect. Here, skin thermal management is conceived to utmostly utilize the photothermal effect of a photovoltaic cell, which not only improves the photoelectric conversion efficiency but also eliminates skin hyperthermia. In vivo, the output power can be higher than 500 mW with a photoelectric conversion efficiency of 9.4%. This output power is promising to recharge all the clinically applied implantable devices via wireless power transmission, that is, clinical pacemakers (6-200 µW), drug pumps (0.5-2 mW), cochlear (5-40 mW), and wireless endo-photo cameras (≈100 mW).

Evaluation of a 3.8-µm laser-induced skin injury and their repair with in vivo OCT imaging and noninvasive monitoring

To explore a 3.8-µm laser-induced damage and wound healing effect, we propose using optical coherence tomography (OCT) and a noninvasive monitoring-based in vivo evaluation method to quantitatively and qualitatively analyze the time-dependent biological effect of a 3.8-µm laser. The optical attenuation coefficient (OAC) is computed using a Fourier-domain algorithm. Three-dimensional (3-D) visualization of OCT images has been implemented to visualize the burnt spots. Furthermore, the burnt spots from the 3-D volumetric data was segmented and visualized, and the quantitative parameters of the burnt spots, such as the mean OACs, areas, and volumes, were computed. Then, OCT images and histological sections were analyzed to compare the structural changes. Within a certain radiation range, there is a linear relationship between radiation dose and temperature. Dermoscopic images, OCT images, and histological sections showed that, within a certain dose range, as the radiation doses increased, the cutaneous damage became more serious. One hour after laser radiation, the mean OACs increased and then decreased; the areas of burnt spots always increased and were 0.95 ± 0.07, 1.01 ± 0.06, 1.025 ± 0.07, 0.99 ± 0.07, 0.98 ± 0.07, 1.00 ± 0.07, 0.96 ± 0.05, and 0.98 ± 0.06 mm^-1, respectively; the areas were 2.10 ± 0.63, 3.75 ± 1.85, 5.95 ± 1.62, 8.35 ± 0.88, 9.44 ± 1.28, 10.29 ± 0.49, 12.27 ± 0.96, and 13.127 ± 1.90 mm²; and the volumes were 1.54 ± 0.41, 2.86 ± 0.09, 3.73 ± 0.49, 4.14 ± 0.80, 7.21 ± 0.52, 6.77 ± 0.45, 8.36 ± 0.25, and 10.65 ± 0.51 mm³; and 21 days after laser radiation, the volumes were 0.67 ± 0.18, 1.64 ± 0.08, 1.87 ± 0.12, 2.57 ± 0.34, 3.43 ± 0.26, 3.64 ± 0.04, 3.84 ± 0.15, and 4.16 ± 0.53 mm³, respectively. We investigated the time-dependent biological effect of 3.8-µm laser-induced cutaneous damage and wound healing using the quantitative parameters of OCT imaging and noninvasive monitoring. The real-time temperature reflects the photothermal effect during laser radiation of mouse skin. OCT images of burnt spots were segmented to compute the mean OACs, burnt area, and quantitative volumes. This study has the potential for in vivo noninvasive and quantitative clinical evaluation in the future.

Quantitative analysis of collagen and capillaries of 3.8-μm laser-induced cutaneous thermal injury and wound healing

The biological effects of cutaneous thermal injury and wound healing after 3.8-μm laser radiation were investigated by observing the effects of different radiation doses on in vivo cutaneous tissue. A 3.8-μm laser with a radiation dose that changes from small (5.07) to large (15.74 J/cm²) was used to irradiate mouse skin with the 2 × 4 grid array method. The healing progress of laser-injured spots, pathological morphology (H&E staining), and collagen structure changes (Sirius Red staining) were dynamically observed from one hour to 21 days after laser radiation, and the capillary count and collagen content were quantitatively and comparatively analyzed. When the radiation doses were 5.07, 6.77, 8.21, and 9.42 J/cm², a white coagulation spot predominantly occurred, and when the radiation doses were 11.09 12.23, 14.13, 15.74 J/cm², a small injured spot predominantly occurred. One hour after radiation, the collagen structure was obviously damaged. Three to fourteen days after radiation, the hyperplasia and morphology of the collagen in the 5.07 J/cm² group were significantly better than those in the other dose groups. The number of capillaries in the 5.07 J/cm² and 6.77 J/cm² groups was significantly higher than that in the normal group (P < 0.01 or P < 0.05). Twenty-one days after radiation, only the collagen in the 5.07 J/cm² group was densely arranged, and it was basically close to the normal group level. The collagen content in the 5.07 J/cm² group was approximately 10.7%, but it was still lower than that in the normal group (with a collagen content of approximately 14.1%). The collagen in the other dose groups was diminished and had not returned to the normal group level. As the dose of the 3.8-μm laser increased, skin thermal injury gradually increased, the full-thickness skin increased, and the collagen content decreased, showing better dose-dependent and time-dependent effect relationships. The increase in capillaries in the early stage of laser radiation and the significant increase in collagen content in the middle and late stages of laser radiation were two important factors that promoted wound healing.

Dose-dependent study of effects of 532-nm continuous wave laser on rat skin: A mechanistic insight

Visible lasers emitting in the green spectral region are being routinely employed in various medical and defense fields namely treatment of pigmented lesions, tattoo inks, port wine stains, dazzling the target or mob dispersal. Despite their increasing applications, lasers also tend to pose occupational hazards to operators, ancillary personnel, individuals undergoing laser therapies. This study was aimed at investigating the effects of different doses of 532-nm continuous wave laser on rat skin. The present study demonstrated that higher fluences of 532-nm continuous wave (CW) laser induces significant tissue damage through induction of tumor necrosis factor-α, cyclooxygenase-2, tumor protein (p53), PARP 1, caspase3 which in turn leads to tissue damage and cell death. Furthermore, level of heat shock proteins, pAkt were found up-regulated as a cope up response to laser-induced stress. On the basis of the findings, irradiation with 532-nm CW laser up to 2.5 J/cm² was found within the safe exposure limits. Thus, it is probably the first attempt to demonstrate the tissue damage induced by 532-nm CW laser on skin, which may help in choosing safe laser dose for certain skin-based applications and evolving methods to ameliorate laser-inflicted injuries.

Lumbar sympathectomy regulates vascular cell turnover in rat hindfoot plantar skin

BACKGROUND

Sympathetic denervation and impaired angiogenesis cause skin diseases. However, the relationship between the sympathetic nervous system and vascular cell turnover in normal skin remains unclear.

OBJECTIVE

To determine the effects of sympathetic denervation on vascular cell turnover in normal skin.

METHODS

Rats underwent bilateral L2-4 sympathetic trunk resection (sympathectomy group) or sham operation (control). Hindfoot plantar skin was analyzed 2 weeks and 3 months postoperatively.

RESULTS

Mural cell marker (α-smooth muscle actin; p < 0.001, and desmin; p = 0.047) expression decreased 2 weeks after sympathectomy, but recovered 3 months after sympathectomy (p > 0.05). CD31 levels were lower in the experimental group than in the control group at 2 weeks (p = 0.009), but not at 3 months. Von Willebrand factor, vascular endothelial growth factor, and angiopoietin-2 expression were not significantly different between the groups (p > 0.05). Angiopoietin-1 expression levels were higher in the experimental group than in the control group at 2 weeks (p = 0.035), but not at 3 months.

CONCLUSIONS

Lumbar sympathectomy regulates vascular cell turnover in rat hindfoot plantar skin by inhibiting mural cell proliferation and increasing angiopoietin-1 expression. Sympathetic nerves therefore play an important role in plantar skin vascular cell turnover.

Comparative evaluations of hypertrophic scar formation in in vivo models

BACKGROUND AND OBJECTIVE

Hypertrophic scar (HTS) results from a connective tissue reaction to trauma, inflammation, surgery, or burn on skin. In spite of various techniques for wound generation, the degree of scar in animal models after healing is still unpredictable and less reproducible. The objective of the current study was to identify the appropriate method to create the maximal HTS tissue in a reliable manner by comparing three different methods in vivo.

MATERIALS AND METHODS

A 27 ICR mice were tested for the in vivo evaluations. Three different methods were applied to develop wounds on the back of each mice for quantitative evaluations on collagen formation: Group 1 (thermal burn), Group 2 (chemical burn), and Group 3 (physical punch). After injury, each lesion was photographed to examine physical variations in the wound areas. Histological analysis was conducted on days 0, 7, and 28 to assess the extent of the injury in the tissue and to quantitatively compare the amount of collagen formation after wound healing.

RESULTS

Compared with Groups 1 and 3, Group 2 demonstrated the largest wound area that gradually decreased with healing time. However, the minimal axial damage (along tissue depth) occurred to Group 2 at day 0 (183.7 ± 28.9, 38.1 ± 9.2, and 296.0 ± 81.7 µm for Groups 1, 2, and 3, respectively). After 28 days, all the groups showed the complete healing and accompanied a significant increase in the number of fibroblast and collagen generation with well-oriented and denser collagen fibers, in comparison with normal skin. Group 2 yielded twice thicker skin (both epidermis and dermis) than the other groups (970.8 ± 108.8 µm for Group 2 vs. 381.5 ± 30.8 µm for Group 1 and 442.9 ± 56.3 µm for Group 3; P < 0.001).

CONCLUSION

The proposed chemical burn can be the optimal method to create collagenous scar tissue in the mouse model. Further in vivo investigations with rat models will be performed to validate the current technique for laser scar treatment in terms of reliability and immunohistochemical responses. Lasers Surg. Med. 9999:XX-XX, 2017. © 2017 Wiley Periodicals, Inc.

A systematic and quantitative method for wound-dressing evaluation

Background

For patients with skin defects such as burns, wound dressing plays important roles in protecting the wound. Before a novel wound dressing is applied to a patient, a series of tests should be performed to ensure its safety and efficacy. Different types of animal wound-healing models have been used to study the bio-function of different wound dressings; however, a systematic way to evaluate the effect of a wound dressing on wound healing and cutaneous regeneration is lacking.

Methods

In the study presented here, full-thickness wound models were established in mice, and a systematic way to quantitatively analyze the wound-healing process and the histological results is described.

Results

It was found that the rate of wound healing in the tested wound dressing (TWD) group was higher than that in the control group, and the re-epithelialization and the formation of granulation tissue were enhanced when the TWD was applied. Meanwhile, the inflammatory response was attenuated in the TWD group, and more mature and better aligned collagen fibers in the healed wound tissue was found in the TWD group compared with that in the control group.

Conclusions

A systematic, quantitative way to analyze the effect of a wound dressing on wound healing was established. And it might be helpful for the design of wound dressing in the future.

Influence of different energy densities of laser phototherapy on oral wound healing

The aim of the present prospective study was to evaluate the impact of laser phototherapy (LPT) on the healing of oral ulcers. Different power densities were used on oral wounds in Wistar rats (n=72) randomly divided into three groups: control (0 J/cm2), 4 J/cm2 laser, and 20 J/cm2 laser. Ulcers (3 mm in diameter) were made on the dorsum of the tongue with a punch. Irradiation with an indium-gallium-aluminum-phosphide laser (660 nm; output power: 40 mW; spot size: 0.04 cm2) was performed once a day in close contact with the ulcer for 14 consecutive days. A statistically significant acceleration in healing time was found with wounds treated with 4 J/cm2 LPT. Moreover, striking differences were found in the ulcer area, healing percentage, degree of reepithelialization, and collagen deposition. The most significant changes occurred after 5 days of irradiation. Based on the conditions employed in the present study, LPT is capable of accelerating the oral mucosa wound-healing process. Moreover, faster and more organized reepithelialization and tissue healing of the oral mucosa were achieved with an energy density of 4 J/cm2 in comparison to 20 J/cm2.