Fig.13 (A)Representative images of
wound tissue sections stained by Picrosirius Red in different treatment
groups on day 3 (Scale bar ¼ 200μm and 10μm). (B) Quantification of the
Ratio of collagen I:III in different treatment groups on day 3 (n ¼
3).(C) Quantification of the content of collagen I in different
treatment groups on day 3 (n ¼ 3)
Next, we need to compare collagen distribution behavior and prognosis in
samples after the second laser welding on the 7th day
and the 14th day. As shown in Fig.14(A), the
deposition area of collagen basically coincides with the proliferation
area of COL-1 fiber, indicating that after the second laser welding, the
proliferation of COL-1 fiber was mainly stimulated. However, for 90°
laser group, the outcome was the opposite. After the second laser
welding, the content of COL-1 fiber in the 90° laser group was greatly
reduced. On the other hand, the COL-3 fiber content was significantly
higher than that after the first stage of laser welding, resulting in
ratio of collagen type was only 1.62 on the 7th day.
This trend was maintained until the 14th day, when the
COL-3 fiber type continued to increase and the ratio of collagen type
was only 0.86, lower than normal skin. For the samples of 60° laser
group, after the second laser welding, the COL-1 fibers of the samples
acquired a large proliferation, and the ratio of collagen type reached
5.2 on the 7th day, which was much higher than other
groups for all time points, indicating that the strength of samples
could be greatly increased after the second laser welding with
60°incident angle, which laid a good foundation for the subsequent
healing process. This also explained the reasons for samples of 60°
laser group on the 14th day were the most similar to
the collagen structure of normal skin tissue, consistent with the
analysis results after Masson staining, and also explains the
rationality of the argument. The collagen type ratio of 30° laser group
on the 7th and the 14th day was
between 2-2.5, which on the one hand ensured the healing speed and
softness of tissue to a certain extent, but also indicated that the
proliferation process of COL-1 fibers was much slower. Although the
wounds of the samples were completely closed on day 14, the
proliferation of COL-1 fibers in the later stage would take longer time[50].
At the same time, as shown in Fig.14(C), we also calculated the
proportion of collagen fiber deposition in samples at these two time
points. We found that although the proportion of collagen deposition in
the 90° laser group was the highest on the third day, it did not
increase significantly after the second laser treatment due to
additional thermal damage caused by vertically incident laser. The
proportion of collagen deposition in the 60° laser group reached a
maximum of 34.6% on day 7, and then continued to increase during the
following healing process.
In this section, the distribution of collagen deposition, the
proliferation tendency of collagen types and the structure and
morphology of collagen network were discussed in detail. In Fig.14(A),
it can be seen that the COL-1 fiber distribution of the samples in the
90° laser group is the most significant, and the COL-3 fiber
distribution is also very fine. At the same time, the deposition area of
collagen network according to Masson staining is also wide and the
overall collagen network turned out to be very fine and dense,
indicating that the healing process of samples was the fastest under 90°
laser welding, but COL-1 collagen was proliferated too much and could be
tended to cause scars. The collagen network of the 30° samples also
showed fine morphology after Masson staining, but differed from the 90°
laser group, the samples of the 30° laser welding showed more COL-3
fibers, and the ratio of two types of collagens were the lowest among
all groups, indicating that the skin elasticity was better, but the
healing process would be very slow, and there was a tendency of
inflammation recurrence in the later stage. On the
14th day, the two staining results of samples under
were the closest to normal skin. From the perspective of collagen growth
behavior, it can be concluded that
60° laser welding was the most conducive to wound healing.