The Effects Of Dermal Structure And Fat Dome Damage With Skin Fibrosis

Objective we designed an animal model with deep dermis defect or dislocation to explore the relationships among the thickness of dermis,defect of deep dermis and the extent of fibrosis.Method he wound model of the experimental group was established in four steps:Step 1 Cut an intermediate split-thickness skin flap(approximately 1.5 mm thick)with a unilateral pedicle(in the shape of a ‘U’)using a rolling dermatome and create an interface within the dermis.Step 2 Cut over the previous wound and obtain a second layer of skin in the same shape and size above the interface that crosses the dermis and adipose layer.Step 3 Make a vertical incision in the adipose layer on the pedicled side of the wound and reach into the fascia layer to create a blunt separation to make a pocket-like formation in the adipose layer.Step 4 Insert the second-layer skin slice into the pocket-like formation to create a model of deep dermis dislocation defect,forming an upper interface between the dermis and adipose layer which is denoted as the D-F interface.The first three steps remained the same in the control group.However,on the fourth step,both skin slices were returned to their original positions,creating an upper interface within the dermis which was denoted as the D-D interface.The lower interface crossing the dermis and adipose layer was denoted as the D-F interface.We randomly chose 6 discontinuous fields under a light microscope to measure the width of the dermis to compare the difference in dermis defect between the groups;the distance between the epidermis and the upper side of the adipose tissue layer and the width of fibrosis of the D-F interface from the experimental group,as well as the D-D and D-F interfaces in the control group,were also detected.We collected those measurements of width in 6 fields for each wound and analysed them using statistical comparisons to reveal the relationship between the intrinsic thickness of the dermis and the extent of fibrosis.Six discontinuous fields were randomly chosen to measure collagen type I and III around the D-F and D-D interfaces from control group and the D-F interfaces from experimental group using Image J software.The superficial layer and adipose tissue of the experimental group were detected by immunohistochemistry,and the control group was the superficial layer and the deep layer of the dermis,whether adipose tissue can promote fibrosis PCNA,TGF-β1,FGF-2,HGF related cytokines.ELISA in the detection of superficial fibroblast cells,deep fibroblast cells and two kinds of fat cells differences in the secretion of I and type III collagen in cultured cells.Results Thickness measurements of each skin layer revealed that in the HE-stained sections,tissues from the experimental group had a greater degree of dermis defect than those from the control group on days 7,14 and 21(P<0.05).However,the distance between the epidermis and the superior border of the adipose tissue layer remained the same in both groups(P>0.05).The width from the dermis to the surface of the adipose tissue was thicker in the experimental group than in the control group at each time point(P<0.05).Accordingly,there was no significant difference in width between the D-D interface and the D-F interface(P>0.05).In sirius red-stained sections,green collagen type III in the experimental D-F and control D-F interfaces was accompanied by a small amount of red collagen type I.Collagen type III expression in the experimental D-F interfaces was significantly higher than that in the control D-F interfaces at each time point(P<0.05),while collagen type I expression was nearly invariable(P>0.05).However,the amounts of collagen type I and type III showed no significant difference between the D-D interface and D-F interfaces in the control group at any time point(P>0.05).In IHC assays,PCNA,TGF-β1,FGF-2 and HGF proteins were easily detected in dermis and adipose tissue not only in the experimental group but also in the control group.ELISA results showed that the fat cells could promote the secretion I collagen.Conclusions these findings indicate that the degree of skin fibrosis is not closely correlated with the damage to the dermal layer of the skin but rather with the deep dermis defect or the intrinsic-thickness deficiency of the skin tissue.Furthermore,the damaged dermis and adipose tissue were demonstrated to play a role in this fibrosis progression.