Morphogenesis Of Horn And Construction Of The Dermal Papilla CDNA Expression Library In Bovine

Bovine horn makes up of projecting frontal bone and specializing keratain shell, horn is a kind of skin appendages as well-known. It is said that bovine horn origins from embryonic horn placode at frontal bone and occurs about embryonic age day 70-100. Its morphogenesis resembles hair follicle and forms underlying epithelial-mesenchymal interaction. Our study on horn morphogenesis will provide new model and clue for the research of epithelial-mesenchymal interaction, it is important and significant for hair follicle biology.We use 18 male bovine embryos whose embryonic age covers from 85d to 280d and mature bovine horns as experiment material. HE staining of paraffin-embedded tissue specimens was used to study the process of morphogenesis in horn placode and the structual characteristic of mature horns. IHC was used to explore the expression and function ofβ-catenin in horn placode morphogenesis as well. Furthermore we also construct the cDNA expression library of horn dermal papilla to prepare for further gene study. The results were as follows:1,The results of HE staining: In early phase (E85～140d), the average thickness of epidermis was about 300μm, the basal cells were simple columnar epithelium, the others were polygonal; in metaphase (E141～210d), the average thickness of epidermis was decreased obviously and was about 150μm, the cell size was minished; the structure of hair follicles was mature and the hair shaft was forming; in late phase (E211～280d), the average thickness and shape of epidermis had no changes clearly, but the stratum corneum became thicker. The thickness of dermis in mature bovine horns got thinner from basal part to upper part, but it got thick again at the top. There was much dermal papillae around the dermis, their length was different throughout horn. They were held tightly in the inner of horny shell.2,The results ofβ-catenin IHC: In early phase,β-catenin was detected in cytoplasm of basal cells and on the membrane of other epidermal cells. It had also been detected in the bulge, the hair matrix and the outer root sheath of hair follicles; in metaphase,β-catenin expressed in cytoplasm of all the epidermal cells and nucleus partly, it still located in the bulge, the hair matrix and the outer root sheath of hair follicles; in late phase, the staining of β-catenin was increasing.3,We had constructed the cDNA expression library of horn dermal papilla successfully. The capability of the stable cDNA library was 4×107 and the recombination was 93%. The quality of this library is excellent and it can afford further molecule study.