不同类型低频电磁场抵抗失重引起的骨流失

目的 研究和比较50 Hz 0.6 mT低频脉冲电磁场(PEMFs)和50 Hz 1.8 mT正弦交变电磁场(SEMFs)防止尾吊大鼠骨量下降的效果,为失重引起的骨流失防治提供理论参考和科学依据。方法 采用尾吊模型大鼠在地面模拟微重力,将40只SD大鼠随机分为对照组、后肢悬吊(HLS)组、HLS+PEMFs组和HLS+SEMFs组4组,每组10只。HLS+PEMFs组和HLS+SEMFs组分别采用50 Hz 0.6 mT的PEMFs和50 Hz 1.8 mT的SEMFs两种电磁场进行治疗,每天干预90 min,4周后处死大鼠。采用双能X射线吸收测定法检测大鼠股骨和椎骨骨密度(BMD),AG-IS型生物力学仪检测生物力学强度,ELISA法检测血清骨钙素(OC)、抗酒石酸酸性磷酸酶5b(Tracp 5b)浓度、甲状旁腺激素(PTH)和环磷酸腺苷(cAMP)的含量,Micro-CT和HE染色观察骨组织微结构。结果 HLS组股骨(P=0.000)和椎骨(P=0.001)的BMD显著低于对照组;HLS+PEMFs组股骨(P=0.001)和椎骨(P=0.039)的BMD显著高于HLS组;HLS+SEMFs组股骨的BMD明显高于HLS组(P=0.003),但椎骨的BMD与HLS组差异无统计学意义(P=0.130);HLS+PEMFs组和HLS+SEMFs组股骨(P=0.818)和椎骨(P=0.614)的BMD差异均无统计学意义。HLS组股骨和椎骨的最大载荷(P=0.000,P=0.009)和弹性模量(P=0.015,P=0.009)显著低于对照组;HLS+PEMFs组股骨(P=0.038)和椎骨(P=0.087)的最大载荷显著高于HLS组,但弹性模量与HLS组相比差异无统计学意义(P=0.324,P=0.091);HLS+SEMFs组股骨和椎骨的最大值载荷(P=0.190,P=0.222)和弹性模量(P=0.512,P=0.437)与HLS组相比差异均无统计学意义。HLS+PEMFs组和HLS+SEMFs组股骨(P=0.585,P=0.948)和椎骨(P=0.668,P=0.349)的最大载荷和弹性模量差异均无统计学意义。HLS组的血清OC水平显著低于对照组(P=0.000),HLS+PEMFs组(P=0.000)和HLS+SEMFs组(P=0.006)的OC水平显著高于HLS组。HLS组的血清Tracp 5b浓度显著高于对照组(P=0.011),HLS+PEMFs组(P=0.459)和HLS+SEMFs组(P=0.469)与对照组相比差异无统计学意义;HLS+PEMFs组(P=0.056)和HLS+SEMFs组(P=0.054)的血清Tracp 5b浓度与HLS组相比差异无统计学意义。HLS组的PTH(P=0.000)和cAMP浓度(P=0.000)显著低于对照组;HLS+PEMFs组和HLS+SEMFs组的PTH(P=0.000,P=0.000)和cAMP浓度(P=0.000,P=0.000)显著高于HLS组。HLS组股骨松质骨与对照组相比非常稀疏,且体积较小。而对照组、HLS+PEMFs组和HLS+SEMFs组的松质骨密度和体积很接近。与对照组相比,HLS组大鼠的BMD(P=0.000)、骨体积(BV)/组织体积(TV)(P=0.000)、骨小梁数量(Tb.N)(P=0.000)和骨小梁厚度(Tb.Th)(P=0.000)最低,骨小梁离散程度(Tb.Sp)(P=0.000)和骨表面积(BS)/BV(P=0.000)最大;与HLS组相比,HLS+PEMFs组和HLS+SEMFs组的Tb.Sp(P=0.000,P=0.000)和BS/BV(P=0.000,P=0.000)显著降低,BMD(P=0.000,P=0.000)、BV/TV(P=0.001,P=0.004)、Tb.Th(P=0.000,P=0.001)和Tb.N(P=0.000,P=0.001)显著升高。HLS+PEMFs组和HLS+SEMFs组的骨小梁厚度差异有统计学意义(P=0.024)。HLS组(P=0.000)、HLS+PEMFs组(P=0.000)和HLS+SEMFs组(P=0.000)骨小梁表面成骨细胞密度明显低于对照组,HLS+PEMFs组(P=0.000)和HLS+SEMFs组(P=0.000)明显高于HLS组。HLS组骨内膜成骨细胞密度显著低于对照组(P=0.000),HLS+PEMFs组(P=0.000)和HLS+SEMFs组(P=0.000)显著高于HLS组,HLS+PEMFs组又显著高于HLS+SEMFs组(P=0.041)。HLS组相比对照组骨髓腔中产生大量脂肪空洞,但治疗组中脂肪球明显减少,几乎与对照组没有差别。HLS组每mm ²骨髓中的脂肪细胞数目是对照组的4倍(P=0.000),HLS+PEMFs组(P=0.000)和HLS+SEMFs组(P=0.000)显著低于HLS组,HLS+PEMFs组和HLS+SEMFs组间差异无统计学意义(P=0.086)。 结论 50 Hz 0.6 mT的PEMFs和50 Hz 1.8 mT的SEMFs治疗可以有效提高尾吊大鼠的BMD和生物力学值,促进大鼠血液中骨形成标记物的浓度,可能通过影响PTH含量激活cAMP通路,进一步提高成骨细胞含量,防止骨微结构的恶化,是良好的电磁场治疗方法。其中PEMFs治疗更显著,可防止约50%的BMD和最大载荷值的降低,通过促进骨形成更好地提高尾吊大鼠骨量。

Different Types of Low-frequency Electromagnetic Fields Resist Bone Loss Caused by Weightlessness

Objective To compare the effects of 50-Hz 0.6-mT low-frequency pulsed electromagnetic fields(PEMFs) and 50-Hz 1.8-mT sinusoidal alternating electromagnetic fields(SEMFs) in preventing bone loss in tail-suspended rats,with an attempt to improve the prevention and treatment of bone loss caused by weightlessness.Methods Tail-suspension rat models were used to simulate microgravity on the ground. Forty rats were randomly divided into four groupscontrol group,hindlimb-suspended(HLS) group,HLS+PEMFs group,and HLS+SEMFs group],with 10 rats in each group. In the PEMFs treatment group and SEMFs treatment group,the intervention was 90 min per day. Rats were sacrificed after four weeks. Bone mineral density(BMD) of femur and vertebra was measured by dual-energy X-ray absorptiometry and biomechanical strength by AG-IS biomechanical instrument. Serum osteocalcin(OC),tartrate-resistant acid phosphatase 5b(Tracp 5b),parathyroid hormone(PTH),and cyclic adenosine monophosphate(cAMP) were detected by ELISA. The microstructure of bone tissue was observed by Micro-CT and HE staining.Results The BMD of the femur(P=0.000) and vertebrae(P=0.001) in the HLS group was significantly lower than in the control group;the BMD of the femurs(P=0.001) and vertebrae(P=0.039) in the HLS+PEMFs group was significantly higher than in the HLS group;the BMD of the femurs in the HLS+SEMFs group was significantly higher than in the HLS group(P=0.003),but the BMD of the vertebrae showed no significant difference(P=0.130). There was no significant difference in the BMD of the femur(P=0.818) and vertebrae(P=0.614) between the HLS+PEMFs group and the HLS+SEMFs group. The maximum load(P=0.000,P=0.009) and elastic modulus(P=0.015,P=0.009) of the femurs and vertebrae in the HLS group were significantly lower than those in the control group;the maximum load of the femur(P=0.038) and vertebrae(P=0.087) in the HLS+PEMFs group was significantly higher than that in the HLS group,but the elastic modulus was not significantly different from that in the HLS group(P=0.324,P=0.091). The maximum load(P=0.190,P=0.222) and elastic modulus(P=0.512,P=0.437) of femurs and vertebrae in the HLS+SEMFs group were not significantly different from those in the HLS group. There were no significant differences in the maximum load and elastic modulus of femurs(P=0.585,P=0.948) and vertebrae(P=0.668,P=0.349) between the HLS+PEMFs group and the HLS+SEMFs group. The serum OC level in the HLS group was significantly lower than that in the control group(P=0.000),and the OC level in HLS+PEMFs group(P=0.000) and HLS+SEMFs group(P=0.006) were significantly higher than that in the HLS group. The serum Tracp 5b concentration in the HLS group was significantly higher than that in the control group(P=0.011). There was no significant difference between the HLS+PEMFs group(P=0.459) and the HLS+SEMFs group(P=0.469) compared with the control group.Serum Tracp 5b concentrations in the HLS+PEMFs group(P=0.056) and the HLS+SEMFs group(P=0.054) were not significantly different from those in the HLS group. The PTH(P=0.000) and cAMP concentrations(P=0.000) in the HLS group were significantly lower than those in the control group. The PTH(P=0.000,P=0.000) and cAMP concentrations(P=0.000,P=0.000) in the HLS+PEMFs group and the HLS+SEMFs group were significantly higher than in the HLS group. The femoral cancellous bone of the HLS group was very sparse and small compared with the control group. The density and volume of the cancellous bone were similar among the control group,HLS+PEMFs group,and HLS+SEMFs group. Compared with the control group,the HLS group had lower BMD(P=0.000),bone volume (BV)/tissue volume(TV)(P=0.000),number of trabecular bone (Tb.N)(P=0.000),and trabecular thickness(Tb.Th)(P=0.000) and higher trabecular bone dispersion(Tb.Sp)(P=0.000) and bone surface area(BS)/BV(P=0.000). Compared with the HLS group,the HLS+PEMFs group and the HLS+SEMFs group had significantly lower Tb.Sp(P=0.000,P=0.000) and BS/BV(P=0.000,P=0.000) and significantly increased BMD(P=0.000,P=0.000),BV/TV(P=0.001,P=0.004),Tb.Th(P=0.000,P=0.001),and Tb.N(P=0.000,P=0.001). The trabecular thickness significantly differed between the HLS+PEMFs group and the HLS+SEMFs group(P=0.024). The HLS group(P=0.000),HLS+PEMFs group(P=0.000),and HLS+SEMFs group(P=0.000) had the significantly lower osteoblast density on the trabecular bone surface than the control group;however,it was significantly higher in the HLS+SEMFs group(P=0.000) and the HLS+PEMFs group(P=0.000) than in the HLS group. The HLS group had significantly lower density of osteoblasts in the endothelium than the control group(P=0.000);however,the density of osteoblasts was significantly higher in HLS+PEMFs group(P=0.000) and HLS+SEMFs group(P=0.000) than HLS group and was significantly higher in HLS+PEMFs group than in HLS+SEMFs group(P=0.041). Compared with the control group,a large number of fatty cavities were produced in the bone marrow cavity in the HLS group,but the fat globules remarkably decreased in the treatment groups,showing no significant difference from the control group. The number of adipose cells per mm ² bone marrow in the HLS group was 4 times that of the control group(P=0.000);it was significantly smaller in the HLS+PEMFs group(P=0.000) and HLS+SEMFs group(P=0.000) than in the HLS group,whereas the difference between the HLS+PEMFs group and the HLS+SEMFs group was not statistically significant(P=0.086). Conclusions 50-Hz 0.6-mT PEMFs and 50-Hz 1.8-mT SEMFs can effectively increase bone mineral density and biomechanical values in tail-suspended rats,increase the concentration of bone formation markers in rat blood,activate the cAMP pathway by affecting PTH levels,and thus further increase the content of osteoblasts to prevent the deterioration of bone micro-structure. In particular,PEMFs can prevent the reduction of bone mineral density and maximum load value by about 50% and increase the bone mass of tail-suspended rats by promoting bone formation.