Multiple nanosecond pulsed electric fields stimulation with conductive poly(l‐lactic acid)/carbon nanotubes films maintains the multipotency of mesenchymal stem cells during prolonged in vitro culture

Mesenchymal stem cells (MSCs) gradually lose multipotency when cultured for prolonged durations in vitro, which significantly hinders subsequent clinical applications. Nanosecond pulsed electric fields (nsPEFs) have been recently investigated to overcome this problem in our lab; however, the differentiation potency of MSCs could only be partially and transiently recovered because the nsPEFs can only be delivered to suspended cells once. Here, we develop a new strategy to apply multiple nsPEFs to adherent MSCs with conductive films to mitigate the decreasing multipotency of prolonged cultured MSCs. The poly(l ‐lactic acid)/graphitized‐carboxylated functionalized carbon nanotubes (PLLA/CNT) films were fabricated as conductive cell culture platforms. Both single and multiple nsPEFs stimulation could significantly increase the differentiation potential of MSCs, as evidenced by upregulated expression of chondrogenic, osteogenic, and adipogenic‐related gene (SOX9, RUNX2, and PPAR‐γ), as well as increased production of proteoglycans, mineralized calcium, and triglycerides. Multiple nsPEFs stimulation demonstrated significant efficacy in upregulating expression of pluripotency genes of OCT4A (3.5‐ to 4.5‐folds), NANOG (3.5‐ to 4.0‐folds), and SOX2 (1.5‐ to 2.0‐folds) and stably maintaining high expression of these genes for nearly 23 days. Notably, nsPEFs stimulation did not significantly shorten telomere length. In conclusion, multiple nsPEFs stimulation could effectively mitigate decreasing multipotency of MSCs during prolonged in vitro culture.     

Risk of childhood acute lymphoblastic leukaemia following parental occupational exposure to extremely low frequency electromagnetic fields

Background:

Earlier studies have reported moderate increases in the risk of acute lymphoblastic leukaemia (ALL) among children whose mothers have been occupationally exposed to extremely low frequency (ELF) electromagnetic fields. Other studies examining parental occupational exposure to ELF and ALL have reported mixed results.

Methods:

In an Australian case–control study of ALL in children aged <15 years, parents were asked about tasks they undertook in each job. Exposure variables were created for any occupational exposure before the birth of the child, in jobs 2 years before birth, in jobs 1 year before birth and up to 1 year after birth.

Results:

In all, 379 case and 854 control mothers and 328 case and 748 control fathers completed an occupational history. Exposure to ELF in all time periods was similar in case and control mothers. There was no difference in exposure between case and control fathers. There was no association between maternal (odds ratio (OR)=0.96; 95% CI=0.74–1.25) or paternal (OR=0.78; 95% CI=0.56–1.09) exposure to ELF any time before the birth and risk of childhood ALL.

Conclusion:

We did not find an increased risk of ALL in offspring of parents with occupational exposure to ELF.     

Occupational and residential exposure to electromagnetic fields and risk of brain tumors in adults: a case-control study in Gironde, France

The etiology of brain tumors remains largely unknown. Among potential risk factors, exposure to electromagnetic fields is suspected. We analyzed the relationship between residential and occupational exposure to electromagnetic field and brain tumors in adults. A case-control study was carried out in southwestern France between May 1999 and April 2001. A total of 221 central nervous system tumors (105 gliomas, 67 meningiomas, 33 neurinomas and 16 others) and 442 individually age- and sex-matched controls selected from general population were included. Electromagnetic field exposure [extremely low frequency (ELF) and radiofrequency separately was assessed in occupational settings through expert judgement based on complete job calendar, and at home by assessing the distance to power lines with the help of a geographical information system. Confounders such as education, use of home pesticide, residency in a rural area and occupational exposure to chemicals were taken into account. Separate analyses were performed for gliomas, meningiomas and acoustic neurinomas. A nonsignificant increase in risk was found for occupational exposure to electromagnetic fields [odds ratio (OR = 1.52, 0.92-2.51)]. This increase became significant for meningiomas, especially when considering ELF separately [OR = 3.02; 95 percent confidence interval (95% CI) =1.10-8.25]. The risk of meningioma was also higher in subjects living in the vicinity of power lines (<100 m), even if not significant (OR = 2.99, 95% CI 0.86-10.40). These data suggest that occupational or residential exposure to ELF may play a role in the occurrence of meningioma.     

永磁磁场对胎鼠大脑皮质神经元细胞的影响

目的以磁源空间磁场定量计算为依据,研究不同强度永磁磁场对胎鼠大脑皮质神经元细胞的影响。方法选取极面中心磁感应强度为3.9、8.0、12.1、20.5、27.0、80.0、170.0、400.0 mT的8组圆片磁源(即A、B、C、D、E、F、G、H组),采用有限元数值法计算其空间磁场,得出磁感应强度。取孕17d胎鼠大脑,分离皮质神经元细胞;将8种不同磁感应强度的磁源分别作用于大鼠脑皮质神经元细胞进行体外培养,6 d后分别用四甲基偶氮唑盐(MTT)法和乳酸脱氢酶(LDH)法检测细胞活力。设非加磁培养大鼠脑皮质神经元细胞为空白对照组。对各组大鼠脑皮质神经元细胞做统计学分析。结果各加磁组皮质神经元细胞光密度(OD)(A组1.204±0.003,B组1.210±0.003,C组1.202±0.004,D组1.220±0.001,E组1.172±0.002,F组1.223±0.012,G组1.235±0.010,H组1.028±0.060)均比空白对照组OD(1.275±0.002)低,其中A、B、C、D、E、H组与空白对照组比较,差异具有统计学意义(P<0.05或0.01),F、G组与空白对照组差异无统计学意义(P>0.05);各加磁组皮质神经元细胞上清液中LDH水平(A组13.33±0.33,B组12.33±0.33,C组8.33±2.33,D组10.67±2.33,E组11.33±4.33,F组10.00±1.00,G组9.00±0.30,H组9.67±0.33)均比空白对照组LDH水平(8.330±0.003)高,其中A、B、D、E、F、H组与空白对照组比较,差异具有统计学意义(P<0.05或0.01),C、G组与空白对照组差异无统计学意义(P>0.05)。结论实验所使用各磁感应强度组磁场对胎鼠大脑皮质神经元细胞代谢有一定抑制作用。     

以视功能障碍为首发症状的脑血管病15例临床特征分析

目的 总结归纳以视力下降、视野缺损为首发症状的脑血管病临床特征。方法 对2008年1月至2009年12月间北京同仁医院神经内科收治的以视力下降、视野缺损为首发症状的脑血管病15例患者进行回顾性分析。结果 患者平均年龄为55±14岁;前循环与后循环病变的平均年龄分别为41±8岁（32～52岁）与60±13岁（42～81岁）。患者主诉包括双眼先后视力下降、单眼视力下降、双眼同时视物不见、双眼偏侧视物不见。诊断烟雾病2例、颈动脉闭塞1例、前循环脑梗死1例、脑血管畸形1例、后循环脑梗死10例。单眼视功能障碍的3例患者均为前循环病变。后循环病变中单或双侧枕、颞叶梗死7例;基底动脉尖综合征1例;脑干梗死2例。结论 以视功能障碍为首发症状的脑血管病可以是前循环病变,也可以是后循环病变;单眼症状为前循环病变,是颈内动脉缺血、闭塞导致的眼征。双眼同时起病及偏盲多是后循环疾病累及枕颞叶所致。     

Impact of imaging landmark on the risk of MRI‐related heating near implanted medical devices like cardiac pacemaker leads

Implanted medical devices such as cardiac pacemakers pose a potential hazard in magnetic resonance imaging. Electromagnetic fields have been shown to cause severe radio frequency‐induced tissue heating in some cases. Imaging exclusion zones have been proposed as an instrument to reduce patient risk. The purpose of this study was to further assess the impact of the imaging landmark on the risk for unintended implant heating by measuring the radio frequency‐induced electric fields in a body phantom under several imaging conditions at 1.5T. The results show that global radio frequency‐induced coupling is highest with the torso centered along the superior–inferior direction of the transmit coil. The induced E‐fields inside the body shift when changing body positioning, reducing both global and local radio frequency coupling if body and/or conductive implant are moved out from the transmit coil center along the z‐direction. Adequate selection of magnetic resonance imaging landmark can significantly reduce potential hazards in patients with implanted medical devices. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

The effect of electromagnetic fields on survival and proliferation rate of dental pulp stem cells

Abstract

Aims: Extremely low-frequency electromagnetic fields (ELF-EMF) can affect biological systems and alter some cell functions like proliferation rate. Dental pulp tissue is known as a source of multipotent stromal stem cells (MSCs), which can be obtained by a less invasive and more available process compared to bone marrow-derived stem cells (BMSCs). This study aimed to consider the effect of ELF-EMF on proliferation rates of human dental pulp stem cells (hDPSCs).

Material and methods: ELF-EMF was generated by a system including autotransformer, multi-meter, solenoid coils, teslameter and its probe. The effect of ELF-EMF with the intensity of 0.5 and 1?mT and 50?Hz on the proliferation rate of hDPSCs was assessed in 20 and 40?min per day for 7?days. MTT assay and DAPI test were used to determine the growth and proliferation of DPSCs.

Results: Based on MTT, ELF-EMF has maximum effect with the intensity of 1?mT for 20?min/day on the proliferation of hDPSCs. The survival and proliferation rate in all exposure groups were significantly higher than the control group. Based on the data obtained from MTT and DAPI assay, the number of viable cells in the group exposed to 1?mT for 20?min/day was higher than other groups (p?<?.05).

Conclusions: Regarding to the results of this study, 0.5 and 1?mT ELF-EMF can enhance survival and proliferation rates of hDPSCs.     

静磁场作用下金属离子对成骨细胞的生物学影响

目的:探讨静磁场(SMF)作用下金属离子对成骨细胞的毒性影响,寻找防治假体周围骨溶解的理论依据。方法:将CoCl2粉末与CrCl3粉末溶于无菌注射用水配制成CoCl2溶液和CrCl3溶液,将Co2+、Cr3+分别与小鼠颅骨成骨细胞(MC3T3-E1)在不同的磁场强度下共培养。将细胞随机分为对照组及3个实验组,各实验组分别放入1、10和100mT的磁场中,培养12、24和48h。倒置显微镜下观察细胞生长情况及形态特征。扫描电镜检测成骨细胞表面超微结构。流式细胞术检测细胞凋亡情况。酶联免疫吸附测定(ELISA)法对培养上清液碱性磷酸酶(ALP)含量进行检测。结果:静磁场作用24h后的成骨细胞呈现更加成熟的形态学特征,不同强度静磁场加载组的成骨细胞细凋亡率除1mT组在12和24h与对照组比较差异无统计学意义外,其他各组不同时段凋亡率均小于对照组。100mT组ALP活性明显高于对照组。结论:静磁场作用下Co2+、Cr3+金属离子对成骨细胞的毒性作用会明显减低,为磁场疗法防治假体周围骨溶解提供了实验依据。     

rTMS对颞叶癫疒间大鼠海马c-FOS和NGF表达的影响

目的:研究低频重复经颅磁刺激(rTMS)对颞叶癫疒间大鼠(TLE)海马结构c-FOS和神经生长因子(NGF)表达的影响。方法:Wistar大鼠共20只,随机抽取5只为对照组。制备成功氯化锂-匹罗卡品化学诱导的TLE模型大鼠10只,随机分为TLE组和重复经颅磁刺激(rTMS)组,每组5只。rTMS组给予0.5Hz,0.4T场强,刺激时程0.2ms,每天20次的1周磁刺激,TLE组和对照组则给予同样次数的声音刺激"(假性"刺激),利用免疫组织化学方法观察对照组、TLE组和rTMS组海马中c-FOS和NGF的表达情况。结果:TLE组大鼠海马区c-FOS表达明显高于对照组,rTMS组大鼠海马区c-FOS表达较TLE组明显降低,但仍高于对照组(均P<0.01)。TLE组大鼠海马区NGF表达明显低于对照组(P<0.01),rTMS组大鼠海马区NGF表达较TLE组明显增高,但与对照组相比表达差别无统计学意义(P=0.09)。结论:适量的rTMS可降低TLE大鼠海马中c-FOS表达,提高NGF表达,对癫疒间造成的病理损伤具有神经保护作用。