Study On Histological Structure Of Sika Deer Antlers And Differentiation Of Mesenchymal Layer Cells In Vitro

Deer antlers are the only mammalian appendage to display an annual cycle of full regeneration. The growth phase in antlers involves the rapid proliferation of a number of tissue types including epidermis, dermis, cartilage, bone, vessel and nerves. Antlers thus provide an excellent model to study the developmental regulation of these tissues. Growth factors are implicated in pedicle formation and antler transformation in deer. In the process of deer antler growth, the growth tip is the most important tissue, however, the histological structure of sika deer antlers hasn't been systematicly verified yet. Recently, there is still some debate as to whether this process represents"true"endochondral ossification and there is not enough evidence for the problem that weather the cells in mesenchymal layer are MSC. In order to study the mechanism of antler formation in sika deer, it is necessary to study the characteristic of growth tip in sika deer antlers.The structure of sika deer antlers has been observed using light microscopy and transmission electron microscope(TEM). The results showed that the growth tip of sika deer antlers consisted of dermis, reserve mesenchyme, precartilage, transition zone and cartilage. The prechonseoblast, chonseoblast and cartilage cells were found gradually from precartilage to cartilage. The histological structure of the growth tip of sika deer antlers was similar to that of the tissue in the process of entochondrostosis. The cells in the mesenchymal layer were similar to each other, and were inactive. The mesenchymal layer might be the stem cells reserving layer. The sika deer antlers might be formed by the process of endochondral ossification.In order to study the characteristics and the roles in the process of antler formation of mesenchymal layer cells, we firstly established the culture and reserve methods of mesenchymal layer cells in sika deer antlers in vitro. The mesenchymal layer cells could be differentiated into cartilage-like cells in vitro with TGF-β1. The cells was checked up with the ways of histology, MTT assay and immunocytochemistry. The results showed that, the mesenchymal layer cells could be cultured in vitro by tissue predigest cell culture, and the suitable medium was DMEM with 10%FBS. Mixing with 5% DMSO + 10% FBS + 80% DMEM and gradually cooled, the cells had high survival rate. The tissue of mesenchymal layer was competent at 4℃for 7 days. Morphology of cells in sika deer antlers was fibroblast-like in vitro, which could not be dyed with toluidine blue. Col II protein was not expressed in these cells. The biological characteristics of mesenchymal layer cells were kept steady before passage 5. Being treated with TGF-β1, the mesenchymal layer cells could be differentiated into cartilage-like cells, indicating that these cells had the potency of differentiation into cartilage cells.This study suggested that the progress of sika deer anlter formination was endochondral ossification. The mesenchymal layer cell was a kind of ASC, and the tissue might be the stem cell reserving layer in anlter growth. Furthermore, to ensure the characteristics of the mesenchymal layer cells and explore the regeneration mechanism of the sika deer antlers, more experiments shoud be done. in the future.