The Expression Differences Of Collagen â…£ And â…¥between Regeneration And Scar Healing Of Skin Wound

Background and Objective Mammal skin wound is usually repaired through regeneration(completely healing) or scar formation(incompletely healing). No matter which one is adopted, wound healing is a complex and procedural process participated by many cells, cell factors, collagens and signaling molecules. Each of them play important role in the post-traumatic inflammatory reaction, cell proliferation, connective tissue formation, wound contraction and skin reconstruction. Scar formation not only produces ugly appearance, but also leads to a dysfunction, for example, serious dysfunction in the joint parts would lead to partial or total loss of organ function. Type Ⅳ and type VI collagen, as the main component of extracellular matrix, play an important role in wound healing. Type IV has multiple effects on wound repair, on the one hand, as the main constructive part of basement membrane, it facilitates the adhension of epidermis to papillary dermis, consequently improves wound healing. On the other hand, it inhibits endothelial cell adhering to basement membrane, subsequently prevents angiogenesis and delays wound repair. Type VI could accelerate the deposition of collagen Ⅰ and Ⅲ, promote cell adhension and activate metalloprotease, which could reconstruct skin wound and advance its repair. Although many investigations have been made in this field, their evolution in skin regeneration and scar formation remains unclear. In this experiment, the integrated model of skin regeneration-scar formation in rabbit ear was established, and the expression of collagen IV and VI in different layers of skin wound zone (from the superficial to deep layers) were tested by Hematoxylin-Eosin staining and immunohistochemistry, By which find their change rules in the process of skin regeneration and scar formation.Materials and Methods:Twenty-six big-ear Japanese rabbits weighing from2.0kg to3.0kg were employed. Each rabbit is housed in a separate cage and given water and feed ad libitum. After one week feeding adaptation, the ventral hair of each rabbit’s ear was depilated with8%Sodium Sulfide and then raised another3days to recover the injury caused by depilator. The animals were anesthetized during the whole operation with2%Pentobarbital Sodium through the vein in ear border, then rabbit’s ears were fully unfolded by self-made equipment, and two wound models---10mm×10mm size, slope from epidermis to cartilage---were made in each ear. Specimen from and around the wounds were respectively taken immediately after operation, and on third-, sixth-, ninth-, twenty and seventh-and fiftieth-postoperative day, and then Hematoxylin-Eosin staining and immunohistochemistry were adopted to test the expression of collagen Ⅳ and Ⅵ. The wounds from the superficial side to the deep side were equally divided into10sections, and each section is1.0mm×1.0mm. The image analysis software-Image-Pro-Plus6.0was adopted to test the average optical density of10points distributed in each section. The results were analyzed by x±s in SPSS18.0. As the variance among each group is homogeneous, their further multiple comparison is conducted by Least Significant Difference method; conversely, Rank Sum Test adopted. P<0.05is considered statistically significant. All study protocols were permitted by the Experimental Animal Ethics Committee of Lanzhou University Second Hospital and all animals received humane care.Results1. Scab was formed on the surface of wounds in third post-operative day, and then dropped off in sixth post-operative days, and the wounds regenerated in ninth day. In the deep wounds, most of the scabs dropped off in ninth day, and epithelized in twelve to14th day, obvious and hard scar was formed in27th day. The scar became soft, and the color of the wounds like the surface around it in50th day.2. Collagen Ⅳ is mainly expressed in skin and blood vessels BMs. Collagen Ⅳ could be tested in the third post-operative day, and reached to its maximum when the wound epithelialized, then significantly reduced in the27th day. Within the27post-operative days, its quantity in superficial wounds is higher than that in deep wounds (p<0.05), and had no obvious difference in50th day(p>0.05).3. Collagen Ⅵ was widely expressed in the entire dermis layer. The wounds began to express in the third post-operative day, and then increased after then, until27th day, began reducing. Within the6post-operative days, its quantity in superficial wounds is higher than that in deep wounds (p<0.05). In the9th,12th,27th post-operative day, its quantity in deep wounds is higher than that in superficial wounds(p<0.05). And in the50th day, no obvious difference was seen among the superficial wounds and the deep wounds.Conclusions1. During the27days after the injury, the expression quantity of Type IV collagen of the superficial wounds is higher than the deep wounds.2. During the6days after the injury, the expression quantity of type VI collagen of the superficial wounds is more than the deep wounds; During9to27days, it is on the contrary.