Fig.10 Representative images of upper epidermis around wound tissue sections in different treatment groups stained by H&E on day 3 (Scale bar ¼ 1 mm). (B) Quantification of the length of neo-epithelial tongue in different treatment groups on day 7 (n ¼ 3). (C) Quantification of the area of neo-epithelium in different treatment groups on day7 ( n ¼ 3). Data represent mean \(\pm\) SD; *, P < 0.05, **, P <0.01, ***, P < 0.001.
Following second laser welding, we proceeded with the extraction of samples on the seventh day as shown in Fig.11. Our aim was to investigate the relationship between healing efficacy and the thickness of the upper epidermis. The regeneration site of the upper epidermis was clearly marked, subsequently expanded to a 10μm scale, and the thickness of the upper epidermis was calculated. Our findings revealed that seven days post-wounding, the least degree of upper epidermal thickness was observed in the control group. Conversely, the most significant thickness was noted in the 60° laser group, followed by the 90° and 30° laser groups respectively. A prior analysis concluded that the upper epidermis exhibited optimal regenerative capacity after the initial phase of 90° laser treatment. Additionally, on the seventh day following the second round of laser welding, the thickness of the upper epidermis reached its zenith within the 60° laser group. This suggests that the first round of laser welding at a 90° incident angle effectively triggers an inflammatory response, thus hastening the healing process [47-49]. However, the secondary laser welding at a 90° incident angle results in relatively higher thermal damage, which paradoxically hinders epithelial regeneration. In contrast, although the laser with a 60° incident angle didn’t yield the most noticeable effect after the first stage of laser welding, it did ensure reasonable thermal damage based on the initial laser welding. Consequently, the healing process was expedited following the second laser procedure.
Regarding laser welding at 30° incident angle, less epithelial regeneration was observed in comparison to the other groups (as shown in Fig.10(A) and Fig.11(A)). This implies that the healing process was more convoluted and slower for these samples. More specifically, epithelial hyperplasia was accompanied by inflammation, and there was a failure to achieve 100% heat transfer in the wound area at the level of the dermis.