3.4 Characterization of RHC/EGF freeze-dried dressing
Scanning electron microscopy results
of RHC and RHC/EGF (1: 1) freeze-dried dressing are shown in Fig. 3. RHC
and RHC/EGF
freeze-dried
dressing had an obvious but irregular pore structure, which facilitated
substance exchange between cells and freeze-dried dressing. However,
compared with RHC freeze-dried dressing, RHC/EGF freeze-dried dressing
self-assemble by lyophilization to form a distinct fiber structure. This
is very similar to the natural ECM
structure. Conducive to the rapid
integration of wound skin during wound repair, and accelerate the speed
and effect of skin wound repair. In addition, solubility experiments
show that RHC and RHC/EGF freeze-dried dressing have good solubility.
Both can be completely dissolved in physiological saline in a short time
(3~5 s), forming a transparent and uniform aqueous
solution and easy-to-use.
3.5. Wound-Healing effect of RHC/EGF forfull-thickness skin defects
in Vivo
We
separately lyophilized EGF, RHC and RHC/EGF to obtain
freeze-dried
dressing. After establishing the
full-thickness skin defects model, the wounds were treated with RHC and
RHC/EGF
freeze-dried dressing respectively. Wounds treated with EGF served as a
positive control group, while physiological saline was administered to
the control group. Wound closure results at each time point in each
experimental group are shown in Fig. 4A. Healing time of the RHC/EGF
group was obviously reduced compared with that of the other groups, and
the wound closure rate of the RHC/EGF group was much higher than that of
the other two groups. These results indicated that RHC/EGF increased the
healing capability of wounds compared with RHC or
EGF. At 10 days post-wounding, a
significantly higher wound closure percentage was monitored in EGF
(88.39 ± 4.13%) and RHC/EGF (90.33 ± 7.47%) versus closure in RHC
(69.32 ± 6.18%) and control (65.79 ±
9.48%),
showing a significant difference (P <0.01) (Fig. 4B). The
appearances of the wounds indicated that RHC/EGF freeze-dried dressing
was an optimal wound dressing for accelerating early healing of skin
wounds. Importantly,
RHC/EGF
freeze-dried dressing improved wound appearance, whereas non-treatment
developed noticeable large and elongate scars.
Then, the histological analysis was
further investigated via H&E staining to assess the quality of the
newly formed skin tissue (Fig. 4C). Early in the process of wound
healing, the reduction of inflammatory cells and the presence of more
capillaries in the damaged skin are beneficial to speeding up wound
repair. At 3d, H&E staining results indicated relief of wound
inflammation and significant capillary growth in the RHC/EGF group,
while there were large amounts of inflammatory cells infiltrating into
the upper layer of dermis in the control and there were almost no
capillaries. Re-epithelialization is an important stage of wound repair.
Through re-epithelialization, the wound area is continuously reduced
until the wound is completely closed and a new dermal layer is
completely formed.(Xiao, Reis, Feric,
Knee, & Radisic, 2016) Evaluation of the skin-injury model after
treatment for 14 and 21 d (Fig. 4D) indicated significantly increased
epithelial thickness in the RHC/EGF group (41.66 ±
4.62μM,P <0.01) compared with control (26.83 ± 3.58μM) and RHC
groups(32.33 ± 3.18μM).