The Roles of Androgens and Androgen Receptor on Bone Formation and Osteoblast Activity

• Main Authors: Je-Min、Chang, 張哲銘
• Other Authors: Yan-Der Hsuuw
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/16807895838674867151

碩士 === 國立屏東科技大學 === 畜產系 === 94 === Androgen receptor (AR)、a member of the nuclear receptor superfamily、has been demonstrated to be important in the mediation with androgen action for the bone growth and metabolism. The aim of this study is to examine the effects of AR on the mice bone development. All study mice were maintained in a barrier facility in accord with individual ventilation cage system. All mice were determined genotypically and classified into wild type (WT) and androgen receptor knockout (ARKO) mice. The study was divided into five objectives. In objective one、we measured the length of mice femur and tibia at 4、7、15、20、30、40 and 50 weeks of age. Results show that、in comparison of femur and tibia length between ARKO and WT mice、there is no significant difference before sexual maturity (age of 4 and 7 weeks). However、the lengths of femur of ARKO after 20 weeks of age、and tibia after 15 weeks of age were trend longer than WT mice. On the other hand、we utilized the histological sections to compare the condrocytes development in growth plate between ARKO and WT. Before sexual maturity (4 and 7 weeks old)、the number of condrocytes in growth plat in femur and tibia of WT mice were increase than ARKO . However、the number of condrocytes in growth plate in femur and tibia of ARKO mice were higher than WT mice post maturity (after age 15 weeks) . Furthermore、we examined the cartilage and metaphyseal in the growth plate of femur and tibia at age of 4 and 7 week old. In the metaphysic、AR inactivation resulted in a significant reduction of growth plate height from the femur and tibia in male ARKO mice. ARKO mice showed a significant reduction in primary spongiosa height、sepongiosa trabecular bone number and secondary spongiosa trabecular bone volumes(P<0.05). In the proximal tibia and distal femur of ARKO mice、there was a significant decline in the total growth plate height、the cell number of proliferative chondrocytes per column、the cell number of hypertrophic chondrocyte per column、and the height of the resting and poliferative chondrocyte(P<0.05). In objective two、Three-dimensional computed tomography was used to exam the anatomical tibia structure of 7 weeks old WT and ARKO mice. The radiography shows that WT mice had higher percentage of bone volume、percentage of bone surface and the number of trabecular number than ARKO mice (P<0.05). However、the density of bone volume、the WT mice is more dense than ARKO mice (P<0.05). In objective three、we utilize Real-time PCR to examine the expression of Alkaline phosphatase、Indian Hedgehog and PTHrPR in growth plate in distal femur and proximal tibia of 7 weeks old both WT and ARKO mice. The results indicate that the ARKO had lower expression of Ihh、PTHrPR and mRNA in ALP than WT mice. Therefore the WT mice had better condrocytes formation、differentiation and mineralization than ARKO mice. In objective four、in order to evaluate the bone formation、the mice calvariae was used.We used the mouse calvariae organ culture model to analyze the effects of dihydrotestosterone (DHT) on the development of osteoblast. We obtained the 4 days old ARKO and WT neonatal rat calvaria and plated separated in contain with 10nM DHT medium and maintained for 7 days.The results show that with add DHT in culture medium promote the number of osteobalst、the wildth and new bone area in WT mice (P<0.05). However、the result was no significant of ARKO mice. In objective five、in the examination the capacity of osteoblast migration and adhesion、the results indicate that the DHT increase the capacity of osteoblast migration and adhesion significantly in calvaria cell of WT mice (P< 0.05). However、no significant results in calvaria cells of ARKO mice.In conclusion、this study indicate that with knockout of androgen receptor can lead to changes in the structure of growth plate、the number of trabecular and volume of femur and tibia. Although、knockout androgen receptor may have potential effects on increase the length of femur and tibia in the post-maturity mice. However、this could due to the androgen is unable to switch the growth of growth plate which proliferate the number of condrocytes. This could be due to the low capacity of proliferation Zone differentiate to hypertrophic in growth plate consequently、the number of trabecular is decreased in ARKO mice、and it may explain the high osteoporosis in ARKO mice. Moreover、ARKO mice has less gene expression in differentiation and mineralization of condrocytes and irresponsive to DHT leading decreased capacity in the formation、migration and adhesion of calvariae cell. Therefore、the androgen receptor plays an important role in mice bone formation and morphology development.