To observe the effect of recombinant human type-Ⅲ collagen hydrogels on wound healing and vascularization, collagen fiber arrangement, and type-Ⅲ collagen proportion during pig full-thickness skin defect wound healing.

The recombinant human type-Ⅲ collagen powder was mixed with sodium alginate powder in mass ratio 10: 1 and dissolved in aseptic phosphate buffer saline to prepare a solution of 10% collagen content. 10% Ca²⁺ solution was used to crosslink the above mixed solution to form gelatin when used.Bama miniature male pigs (n=3) were used as experimental animal to prepare animal models. In each pig, three square-shaped full-thickness skin defect wounds were made on both sides of the back. Each pig served as its own control. Tissues in the experimental group were treated with recombinant human type-Ⅲ collagen hydrogel and covered with sterile silicone membranes for moisturizing. Positive control tissues were treated with absorbable dressing, and negative control tissues were covered with sterile silicone membranes only. On postoperative days 7, 14, 21, and 90, wounds were grossly observed and specimens collected to assess wound repair and inflammatory responses using hematoxylin-eosin staining under a microscope. CD31 expression and regenerated blood vessel counts were measured immunohistochemically. The collagen fiber arrangement and type-Ⅲ collagen proportion were observed using picrosirius red staining under a polarized light microscope. The experimental data were compared by one-way ANOVA, SNK-q test or Kruskal Wallis H test.

Granulation tissues in the experimental group were smooth, bright red, soft, and moist. Inflammatory responses were reduced and early granulation tissue growth rate was elevated in the experimental group compared to those in the control groups. On postoperative days 7, 14 and 21, CD31 expression revealed that the number of new capillaries in the experimental group was (18.8±2.7), (32.0±4.4) and (42.8±4.5)/hpf respectively, while that in the negative control group was (12.0±3.0), (16.6±2.3) and (12.6±4.1)/hpf, respectively. The number of new capillaries in the experimental group was higher than that in the negative control group at each time point. The differences were statistically significant (with P values below 0.05). The collagen fibers in the experimental group exhibited better arrangement than those in the negative control group, and comparable to the positive control group. Moreover, a higher type-Ⅲ collagen proportion was found in the experimental group than in the positive and negative control groups at 14, 21 and 90 days after surgery according to picrosirius red staining.

Recombinant human type-Ⅲ collagen hydrogel promotes wound healing, induces angiogenesis, promotes collagen fiber better arrangement in regenerated dermal tissues, and increases the type-Ⅲ collagen proportion in regenerated dermal tissues during the process of wound healing. These benefits could improve wound healing and may reduce scar formation after wound healing.