Hypomagnetic field (HMF), one of the key environmental risk factors for astronauts traveling in outer space, has previously been shown to repress locomotion of mammalians. However, underlying mechanisms of how HMF affects the motor system remains poorly understood. In this study, we created an HMF (<3 μT) by eliminating geomagnetic field (GMF, ∼50 μT) and exposed primary mouse skeletal muscle cells to this low magnetic field condition for a period of three days. HMF-exposed cells showed a decline in cell viability relative to GMF control, even though cells appeared normal in terms of morphology and survival rate. After a 3-day HMF-exposure, glucose consumption of skeletal muscle cells was significantly lower than GMF control, accompanied by less adenosine triphosphate (ATP) and adenosine diphosphate (ADP) content and higher ADP/ATP ratio. In agreement with these findings, mitochondrial membrane potential of HMF-exposed cells was also lower, whereas levels of cellular Reactive Oxygen Species were higher. Moreover, viability and membrane potential of isolated mitochondria were reduced after 1 h HMF-exposure in vitro. Our results indicate that mitochondria can directly respond to HMF at functional level, and suggest that HMF-induced decline in cell functionality results from a reduction in energy production and mitochondrial activity.

Living organisms are exposed to the geomagnetic field (GMF) throughout their lifespan. Elimination of the GMF, resulting in a hypogeomagnetic field (HMF), leads to central nervous system dysfunction and abnormal development in animals. However, the cellular mechanisms underlying these effects have not been identified so far. Here, we show that exposure to an HMF (<200 nT), produced by a magnetic field shielding chamber, promotes the proliferation of neural progenitor/stem cells (NPCs/NSCs) from C57BL/6 mice. Following seven-day HMF-exposure, the primary neurospheres (NSs) were significantly larger in size, and twice more NPCs/NSCs were harvested from neonatal NSs, when compared to the GMF controls. The self-renewal capacity and multipotency of the NSs were maintained, as HMF-exposed NSs were positive for NSC markers (Nestin and Sox2), and could differentiate into neurons and astrocyte/glial cells and be passaged continuously. In addition, adult mice exposed to the HMF for one month were observed to have a greater number of proliferative cells in the subventricular zone. These findings indicate that continuous HMF-exposure increases the proliferation of NPCs/NSCs, in vitro and in vivo. HMF-disturbed NPCs/NSCs production probably affects brain development and function, which provides a novel clue for elucidating the cellular mechanisms of the bio-HMF response.Electronic supplementary materialThe online version of this article (doi:10.1007/s13238-016-0300-7) contains supplementary material, which is available to authorized users.

Hypomagnetic fields (HMF), that is, the elimination of the geomagnetic field (GMF), are a risk factor to the health of astronauts in outer space. It has been established that continuous HMF exposure affects cytoskeleton assembly, cell proliferation, embryonic development, and even learning and memory. In addition, although there were some previous studies that focused on the effects of long-term HMF-exposure, so far very limited investigations have been conducted to examine the short-term HMF effect in animals. In this study, we exposed adult male C57BL/6 mice to a 3-axis Helmholtz-coil HMF-simulation system for 72 h and found that short-term HMFexposure induced a significant increase in anxiety-related behaviors. And our findings provide important information for both psychological intervention and the health care of astronauts.