Histological Observation Of Chicken Wounded Skin Healing Process Without Scar Tissue

It is a big problem to the surgeon that wound healing of skin is usually acommpanied by cicatrix, which not only affects the appearance but also affects the function of organs. We found that there was no scar formation after trauma when we did chicken ovariectomy. It sparked us research interests in the skin wound healing processes of chicken.Firstly, normal skin structures of different parts of the chicken, included Pectoral apterium, Scapular apterium, Postauricular apterium, Pectoral pterylae, Crural pterylae, Back pterylae and Cervical pterylae, were observed and studied under light microscope after sequentially steps, including collected skin samples, formalin-fixed, paraffin- embedded tissue samples sectioned and stained with hematoxylin and eosin (HE) and orcein stain. It was observed that the epidermis of the normal chicken skin was thin and with a few layers number. Stratum spinosum cells diffused distribution between the stratum basale and the stratum transitivum. The stratum superficiale of back pterylae, pectoral pterylae, pectoral apterium and postauricular apterium contained more fibrocytes and capillaries. The smooth muscle were not distributed in the stratum compactum of pterylae, and the smooth muscle were distributed in the stratum laxum of pterylae and apterium. The stratum laxum was thicker than stratum compactum. It was not found that lamina elastica distributed in the cervical pterylae.Secondly, the histological changes in wound healing processes of adult chicken pterylae and apterium were observed. The result showed that the wound accompanied by bleeding phenomenon, inflammatory exudates and scar generation at the 1st day after trauma. It was observed that the granulation tissue contained a large number of fibroblasts and capillaries at the 4th day after trauma. The wound site was filled by granulation tissue and the surface covered thicker epidermis at the 9th day after trauma. And then, the upper level of granulation tissue slowly transformed into stratum superficiale and stratum compactum. The deep level of granulation tissue gradually reduced and finally disappeared progressively, meanwhile the lamina elastica and the stratum laxum of dermis formed slowly. The granulation tissue had disappeared ultimately and no scar tissue formatted at the 60th day after trauma.In addition, immunohistochemistry was used to study the variation of fibroblast growth factor (FGF), and epidermal growth factor (EGF) of adult chicken during the healing process. The result showed that the expression level of FGF was very low in normal skin tissue of chicken. FGF expression level in wound site began to rise at the 2nd day after trauma and reached a peak at the 7th day, and returned to the normal level at the 14th day after trauma. EGF expression level began to rise at the 2nd day after trauma, and reached a peak at the 4th day, and then began to decrease. It returned to the normal level at the 30th day after trauma. The results revealed that these two growth factors were involved in the formation of granulation tissue in early stage during the healing process.These results showed that the formation of the granulation tissue during the healing process of chicken skin has the same characteristics with the mammal. However, there was no scar tissue formation of granulation tissue at the final stage.