The Study On Dermal Substitute Containing Human Hair Keratin

Tissue engineering dermal substitute is reconstructed generally with collagen as the matrix seeded with fibroblasts. However, the vascularization and being overtaken by the receptor's own tissue is slow after transplantation. In our study, we used first time the human hair keratin (HHK) as a matrix component to prepare the dermal substitute, to observe its possible merits and shortcomings, and to explore whether it could become an effective component in the preparation of tissue engineering skin. We constructed the living dermal substitute using this new matrix embedded with rat dermal fibroblasts (RDF), then grafted it subcutaneously in rats. By histological and immunohistochemical staining, we observed the morphology of this three-dimensional culture system with hair net, and explored the formation of a neo-dermis when the dermal substitute consisting of collagen and human hair was grafted subcutaneously in rats.(1) The study of RDFs in the three-dimenasional culture with human hair net. After subcultured 3-4 generations, RDFs were mixed in collagen solution, into which the human hair net was put before it gelled, then cultured in a three-dimenasional way, while the control was RDFs in gel. After 7 days in culture, prominent contraction occurred in the control gel, its diameter was about 1/3 of the original, while contraction was inhibited by the hair net in the experiment gel. The morphology of RDFs in the two groups were compared by microscopy and collagen type I immunostaining. After 3 weeks of culture, in the collagen lattice with human hair net, RDFs were in long spindle shape, arranging in a plane parallel to the surface of the gel. However, in the control RDFs were arranged randomly. Besides, cytoplasm was stained positively for collagen type I in both cultures. The observations verified that human hair net functions as a mechanical device.(2) The study of grafting in rats subcutaneously of dermal substitute. On 4th day post-grafting, the infiltration of neutrophils and monocytes were observed in both groups but more serious around the hair. On 7th day, theinfiltration was ameliorated, whereas a layer of macrophages surrounded the hair; blood vessels were observed in the two groups, while that was sparse in control graft. On 10th day, vWF immunohistochernistry showed that the grafts with hair were more vascularized. After 2 weeks, macrophages surrounded human hair like a sheath. After 3 weeks human hair was degraded a little and newly formed collagenous fibers were observed. From the 5th to the 12th week, the grafts were mostly replaced by newly formed connective tissue including elastic fibers. Human hair still existed though it was spattered. Histological observations demonstrate that human hair in the matrix improved the vascularization and the regeneration of connective tissue which maybe attributed to the inflammation spurred by the human hair; while the long-term chronic inflammation and the human hair color still remains problems to be overcome.