Effects Of Estrogen And Androgen On Osteoblasts And Medullary Bone Formation In Layer

Estrogen and androgen play important roles in bone metabolism. There are a lot of medullary bone formation before the sex maturation, and the medullary bone provide calcium for the calcification of the egg shell during the laying period. Estrogen and androgen are relative to the medullary bone formation, and effect osteoblasts proliferation, differentiation, cell cycle and apoptosis via estrogen receptor and androgen receptor. Considering that estrogen and androgen’s important role in medullary bone formation, there were two aims of this study, one was to find the effects of estrogen and androgen on medullary bone, and the other was to find the changes of osteoblasts function to provide theory for medullary bone formation.Experiment I Effects of Estrogen, Androgen and Both Combined on Bone Metabolism of ISA Hens before Sexual MaturityObjective: To observe the effects of estrogen, androgen and their combination on bone metabolism in the period of adolescent cage layer hens. Methods: 300 adolescent ISA hens (92 days old) were divided into 5 groups, the experiment lasted 20 days. Cortical bone histomorphometric analysis were observated. Plasma calcium (Ca), phosphorus (P), alkaline phosphatase (AKP), tartrate-resistant acid phosphatase (StrACP) were measured by automatic biochemistry analyzer. Results: Compared with control, the concentration of AKP and humerus weight increased significantly (P<0.05) in estrogen group; the concentration of AKP, humerus weight, CAR, Cr. ED and Cr. Ar increased significantly (P<0.05) in androgen group; the concentration of AKP and Ca, humerus weight, CAR, and Cr. Ar increased significantly (P<0.05) in their combined group at 10 days. The concentration of Ca and P increased (P<0.05) and the concentration of StrACP decreased (P<0.05) in estrogen group; Cr. Wi increased (P<0.05) in combined group at 15 days. Cr. ID increase and Cr. ED decrease (P<0.05) in combined group at 20 days. There was no significant difference of the control and solvent. Conclusion:It revealed that estrogen could stimulate bone formation, inhibit bone resorption and improve the bone development in hens; androgen could increase cortical bone size and mass in pre-sexual maturation hens; estrogen and androgen combined could promote bone formation, resorption, and bone turnover. ExperimentⅡEffects of Estrogen, Androgen, and Both Combined on the Medullary Bone FormationObjective: To observe the effects of estrogen, androgen, and their combination on the medullary bone formation in young birds. Methods: 300 ISA pullets and 90 ISA roosters of 92 days old were fed for one week before experiment.300 ISA pullets were averagely divided into A, B, C, D, and E groups at random, respectively. Group F was castrated ISA roosters. The experiment lasted for 20 days. In the initial and different phases of the experiment, the bone samples were collected for making bone slice. Results: The results showed that the medullary bone did not form in group A, B, or D. However, the medullary bone began to be reduced in group C at 15 days. A large amount of the medullary bone could be found in group E and F at 10 days. Compared with control A and B, the concentration of E2 increased and testosterone decreased in group C and E. (P<0.05); the concentration of E2 decreased and testosterone increased in group D (P<0.05); the concentration of E2 increased and testosterone decreased in group F (P<0.05). Conclusion:estrogen and androgen had dependent effects on medullary bone formation in pre-sexual maturation hens.ExperimentⅢEffects of the Estrogen, Androgen, and Both Combined on the Estrogen Receptor, Androgen Receptor and Their mRNA Expression in Bone Tissue in Layers.Objective: To observe the location of estrogen receptor and androgen receptor in bone tissue, and the effects of estrogen, androgen, and both combined on the estrogen receptor and androgen receptor mRNA expression. Methods: Immunohistochemistry assay was used to observe the location of estrogen receptor and androgen receptor. RT-PCR assay was used to determine the expression of estrogen receptor and androgen receptor. Results: The results of Immunohistochemistry indicated that estrogen receptor was in cell nucleus and cytoplasm of osteoblasts and osteoclasts, and increased by estrogen and both combined. The results of RT-PCR assay indicated that estrogen induce ER expression and androgen induce AR mRNA expression. Conclusion:estrogen and androgen could prompt the ER and AR expression, respectively. The ER and AR level had direct correlation with blood plasma estrogen and androgen.ExperimentⅣEffects of Estrogen, Androgen, and both Combined on Chicken Osteoblasts Proliferation, Differentiation, Cell Cycle and ApoptosisObjective: The objective of this experiment was to investigate the effects of estrogen, androgen and both combined on chicken osteoblasts proliferation, alkaline phosphatase (AKP) activity, the cell cycle, and apoptosis. Methods: The osteoblasts were treated with estrogen and androgen alone or in combination. The cell proliferation were detected with MTT method, the cell apoptosis and cell cycle with flowcytometry. Results: The results indicated that the estradiol, testosterone and both treatments could significantly enhance osteoblastic proliferation and AKP activity, accelerate the osteoblast cell cycle, and stimulated osteoblast DNA synthesis in a period of 24 h. Estrogen, used alone or with testosterone, inhibited chicken osteoblast apoptosis. However, testosterone alone induced cell apoptosis. Conclusion:Estrogen combined with testosterone promoted osteoblast proliferation and AKP activity, accelerated the osteoblast cell cycle, inhibited osteoblast apoptosis.ExperimentⅤEffects of Estrogen, Androgen, and both Combined on Chicken Osteoblast mRNA Expression of Estrogen Receptor and Androgen Receptor.Objective: The objective of this experiment was to investigate the effects of estrogen, androgen, and both combined on osteoblast mRNA expression of estrogen receptor (ER) and androgen receptor (AR). Methods: The osteoblasts were treated with estrogen and androgen alone or in combination. The mRNA expression of estrogen receptor and androgen receptor with fluorescence real-time quantitative RT-PCR. Results: Estrogen alone and combined with androgen could promote the mRNA expression of estrogen receptor; androgen and combined with estrogen could also promote the mRNA expression of androgen receptor. Conclusion:Estrogen combined with androgen could induce ER and AR mRNA expression.