| Morphogenesis is the process that embryonic cells differentiate into organs and organisms with different appearance and structure.The Bovine hoof skin appendages include the keratin shell that wraps around the distal phalanx and the periphery hair follicle. Research on the morphogenesis of bovine hoof skin appendages not only has the theoretical value to the popular problems in developmental biology and the epithelium-mesenchymal interactions mechanism in the organic morphogenesis, but has application perspective in hair follicle biology, stem cell biology and regeneration medicine. We used paraffin section and HE staining to investigate morphogenesis of bovine hoof skin appendages in histomorphology, then, used immunohistochemical method qualitatively detected the temporal and spatial expressions ofβ-catenin.Those are the initial basic research in the morphogenesis of bovine hoof skin appendages. The results and conclusions see below:1 The histomorphological research in the morphogenesis of bovne hoof skin appendages Using the HE staining invstigated the morphogenesis of bovine hoof's dermis, epidermis, and the hair follicle of the hoof periphery.(1) Dermal papilla appeared in the coronary and parietal part of the hoof in E60 firstly, the dermis and the epidermis interlocked each other and formed the dermal lamellae, this junction became tighter in the developmental process; the dermal papilla in the sole of the hoof first appeared in E70, and grew bigger and deeper in E71-90, in E91 first bifurcation appeared, then the mumber, thickness and length of dermal papilla were all increased, in E91-225, the mumber, the thickness and length of the dermal papilla in the sole of the hoof reached the max value; the perioplic dermal papilla first appeared in E75, the number and size of the perioplic dermal papilla can not matched the dermal papilla in other parts of the hoof.(2) The epidermis grew thicker, swelled upward on the hoof periphery in E70; in E93, first hair germ appeared, placode visable, the cells of the epthelium and the mesenchymal visable; in E106-174, hair germ and hair peg visable; in E210, primary hair follicle appeared; in E230, hair follcile mature. In addtion, we found that the placode, hair germ, hair peg and the hair follicle arranged along the ladder-shape away from the hoof. This demostrated that the skin appendages mature degree exhibited negtive correlation with the distance away from the hoof.(3) The developmental order of the skin appendages in bovine hoof is: coronary and parietal dermal papilla→dermal papilla of the sole→perioplic dermal papilla→placode→hair germ→hair peg→hair follcie; The E191 is a turning point, before E191, hair follcle, dermal papilla and epidermis of the hoof periphery kept developing, the epidermis kept growing thicker, after E191,the development of hair follicle inhibited the development of the epidermis, afterward, the hair follicle and dermal papilla of bovine hoof continuted grow but the epidermis grew thinner and thinner.2 Expression ofβ-catenin in the morphogenesis of bovine hoof skin appendages Using the immunohistochemical method qualitatively detect the temporal and spatial expressions ofβ-catenin in the dermis and epidermis in the morphogenesis of bovine hoof skin appendages.(1)β-catenin kept expressing in the morphogenesis of the dermis and epidermis of bovine hoof. In basal layer in all parts of hoof, expressed from weak to strong intensity in E68-93 gradually, in basal layer in perioplic, coronary, parietal and tip of hoof, in E106-167 and E184-225,β-catenin expressed from less strong to strong intensity gradually; in epidermis, in perioplic,coronary, parietal and tip of hoof,β-catenin expressed from weak to less strong intensity gradually in E68-167, in E184-225, expressed from weak to strong intensity; in basal layer in sole of hoof,β-catenin expressed strongly in early phase in bifurcation, and expressed weakly in metaphase and late phase in bifurcation. No expression was found in dermis in bovine hoof. We also found the nucleusβ-catenin expression in later stage(after E196). we deduced thatβ-catenin here promoted the proliferation and differentiation of epidermal keratinocytes of the bovine hoof. This suggested thatβ-catenin plays an important role in the dermis and epidermis in the morphogenesis of bovine hoof skin appendages.(2)β-catenin was detected in suprabasal, epidermal basal layer, placode,hair bud in early phase(E68-93),and expressed strongly in epidermal basal layer, placode, and hair bud, in suprabasal expressed less strongly; in metaphase(E94-184),β-catenin was detected in epidermis, hair peg, and in suprabasal, epidermal basal layer, hair follicle bulge, inner root sheath, outer root sheath, follicular infundibulum expressed less strongly; in late phase(E184-225),β-catenin expressed weakly in epidermal basal layers, while expressed strongly in.epidermal keratinocytes.The result suggested thatβ-catenin plays an important role in hair follicle morphogenesis in the periphery of bovine hoof in bovine embryos.(3) Noβ-catenin was detected in the dermis of the hoof in the morphogenesis of it's skin appendages;β-catenin expressed from weak to srtong intensity in bovine hoof and hoof periphery epidermal basal layer in E68-93, This indicated thatβ-catenin expression in the morphogenesis of skin appendages has some synchronicity.3 Construction of cDNA expression library of the bovine hoof dermal papillaWe successfully constructed cDNA expression library of the bovine hoof dermal papilla, so futher research can be done to screening and colon the specific expression genes, and this will benifical to the research of the control of the gene expression and the molecular mechanism in the morphogenesis of bovine hoof skin appendage. |
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