ABSTRACT
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.
ABSTRACT
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.
