| ObjectiveTo explore the effects of aeronautical environmental factors on bone metabolism in civil aviation flight personnel,we investigated the biochemical markers of bone metabolism and calculated the effective dose of cosmic radiation for flight personnel, and then we analyzed the correlations between the level of bone metabolism and the effective dose of cosmic radiation.To explore the pathogenesis of bone injury induced by irradiation,we established the experimental model with two different sources of osteoblasts(MC3T3-E1 cell lines and primary cultured rat's osteoblasts) by in vitro cell culture technology.To explore the effects and mechanism of radiation on osteoblasts,the cultured osteoblasts were irradiated with different doses 137Csγ-rays.We observed the changes of morphology,ALP activity and BGP activity and mRNA expression of bone Glaprotein(BGP),osteoprotegerin(OPG),bone morphogenetic protein-2(BMP-2),insulin-like growth factor-â… (IGF-â… ),which will provide important experimental basis for the prevention and treatment of radioactive bone injury.Methods1.134 healthy male civil aviation flight personnel of xinjiang airline stratified by age (from the age of 20 to 60 years)and 37 healthy male controls(from the age of 20 to 60 years)were randomly selected and were divided into three different age groups(from 20 to 29,from 30 to 39 and above 40 years old).Bone glaprotein(BGP)was measured with radioimmunoassay and bone specific alkaline phosphatase(BALP) was measured with enzyme-linked immunoassay,with the help of aircraft flight information from flight performance manual,software CARI-6 developed by U.S Federal Aviation Administration was used to calculate the effective dose of cosmic radiation along the air lines,then individual annual cosmic radiation dose and cumulative cosmic radiation dose on flight personnel was estimated from the data calculated by CARI-6.The results were analyzed with t-test,and the correlations between the variables and the flight hours were analyzed with linear correlation. 2.The MC3T3-E1 cell lines and the rat's osteoblasts(ROB)isolated from the skull of the newborn SD rats by sequential enzymatic digestion were once irradiated with 137 Csγ-rays(dose Rate of 0.788Gy/min)at 1,3,6 and 9Gy respectively.The control group(0Gy)cells also were taken into the preparation room.The culture medium was changed immediately after irradiation.We observed the morphological changes of osteoblasts with phase-contrast microscope every day and detected cell proliferation by MTT every other day.7 days later,ALP activity and BGP levels were measured. Total RNA was extracted with TRIZOL reagent and mRNA expressions of BGP,OPG,BMP-2 and IGF-â… were determined by RT-PCR semi-quantitatively.Results1.The results showed that both the BGP and BALP level were lower in civil aviation flight personnel,compared with controls.The BGP and BALP in groups aged from 20 to 29 years and from 30 to 39 years were significantly lower than in control group respectively(P＜0.01),while there was no statistical difference between two groups aged above 40 years old(P＞0.05.According to the literature,the average effective dose rate of all flights of Xinjiang Airlines was 2.55μSv.h-1(ranging between 1.39～4.90μSv.h-1).Average annual cosmic radiation dose on flight personnel was 1.88mSv.a-1(ranging between 0.70～4.14mSv.a-1),cumulative cosmic radiation dose on flight personnel was 20.71 mSv(ranging between 2.81～57.52mSv).Both the BGP and the BALP were significantly correlated with annual cosmic radiation dose and cumulative cosmic radiation dose in civil aviation flight personnel.(P＜0.01).2.The results showed that morphology of osteoblasts changed both in MC3T3-E1 cell lines and ROB cells after irradiation.The osteoblasts without irradiation grew intensively with rich cytoplasm and irregular polygon.However,the osteoblasts irradiated with different doses of 137 Csγ-rays were larger,containing more nuclei, homogeneous cytoplasm,poor refraction and multinucleated giant cells occasionally. The above changes were more obvious with increasing dosage of irradiation.3.We found that both MTT(OD)value and the rate of cell proliferation were decreased significantly in osteoblasts irradiated after 1d,3d,5d,7d(P＜0.01). Compared with the control group,the MTT(OD)value was significantly lower in all experimental groups of MC3T3-E1 cell lines and ROB cells.Compared with the control group at the same time point,the rate of cell proliferation in MC3T3-E1 cell lines were significantly lower in all experimental groups.In ROB cells,the rate of cell proliferation were significantly lower in groups irradiated with 3,6,9Gy.While there was statistical difference between the group irradiated with 1Gy and the control group only irradiated after 7days.And the MTT(OD)value was obviously correlated with the dosage of irradiation.4.We found that both the ALP activity and BGP levels were decreased significantly in osteoblasts after irradiation.(P＜0.01).Compared with the control group in MC3T3-E1 cell lines,the ALP activity was significantly reduced in groups irradiated with 3,6 and 9Gy,while the BGP levels were significantly reduced in groups 1,3,6 and 9Gy.In ROB cells,there was a significant difference between the control group and experimental groups on the ALP activity and BGP levels.Both the ALP activity and BGP levels were obviously correlated with the dosage of irradiation.5.We found that mRNA expression of BGP,OPG BMP-2 and IGF-â… was decreased significantly in osteoblasts after irradiation.(P＜0.01).Compared with the control group in MC3T3-E1 cell lines,mRNA expression of BGP,BMP-2 and IGF-â… was significantly lower in groups irradiated with 3,6 and 9Gy,while mRNA expression of OPG were significantly lower in groups 1,3,6 and 9Gy.Compared with the control group in ROB cells,mRNA expression of OPG and BMP-2 was significantly lower in groups irradiated with 3,6 and 9Gy,while mRNA expression BGP and IGF-â… were significantly lower in groups 1,3,6 and 9Gy.Quantity of BGP,OPG,BMP-2 and IGF-â… mRNA expression were obviously correlated with the dosage of irradiation.Conclusions1.Cosmic radiation may affect the level of bone metabolism in civil aviation flight personnel,which was significantly correlated with the effective dose of cosmic radiation.2.The response to irradiation in MC3T3-E1 cell lines and ROB cells was similar, while the sensitivity was slightly different.After irradiation,the morphology of osteoblasts was obviously changed;the proliferation,differentiation and function of osteoblasts were significantly inhibited,which were significantly related to the radiation dose.While the proliferation,differentiation and function of osteoblasts were different in terms of their sensitivity to irradiation,which may reflect their different mechanisms.After irradiation,mRNA expression of BGP,OPG,BMP-2 and IGF-â… were significantly decreased in osteoblasts,which were significantly related to the radiation dose.Irradiation may affect the gene expression of osteoblasts,thus affecting the proliferation,differentiation and function of osteoblasts,which will reduce the bone formation,destruct the balance in the process of rebuilding,and lead to bone damage.
|
PDF Full Text Request