Effects Of Extremely Low Frequency Electromagnetic Fields On Differentiation Of Mesencephalic Neural Progenitors And The Possible Mechanism

Characteristics of self-renewal and multipotentiality allow neural progenitors engraft and replace damaged tissues in the CNS. However, engrafted into the adult normal and injured CNS, pluripotent neural progenitors differentiate mainly into the glial lineage, suggesting that ex vivo induction toward phenotypes required to replace the damaged populations may be necessary before transplantation.As known, generation of distinct cell types involves the action of both extrinsic signals and inherent "program". Extrinsic signals, including NCAM, PDGF, IL-1 , have been shown to promote neural progenitor cells to acquire a neuronal fate. However, some physical signals do exist in the cell microenvironment except chemical ones. The spatio-temporal distribution and strength of internal electromagnetic field serve as proper signals involved in neural plasticity. It was reported that the growth cone of Xenopus embryonic neurons might response to a 7mV/mm electric signal and extend to the cathod; also, neuronal differentiation was enhanced in the existence of electromagnetic field.The present study was therefore designed to investigate inductive differentiation of mesencephalic neural progenitors by different extremely low frequency electromagnetic fields (ELF-EMFs)(5-40Hz, 8 mT or5 Hz, 4mT) in detail, screening for a stable and effective manipulation of cell differentiation to a neuronal fate.First of all, self-renewal and pluripotent mesencephalic neural progenitors of newborn rats were floatingly cultured in serum-free medium containing bFGF in vitro. In the subsequently serial differentiation studies, the findings were as followed: (l)Among observed chemicals, only 50 pg/ml IL-1 was found to promote neuron-oriented differentiation of mesencephalic neural progenitors while 100 ng/ml GDNF, 10 ng/ml CNTF and 10-5 mM gastrodin indicated a inhibitory effect, the rest chemicals, 10-5mM puerarin, or 10-5mM arctiin, or 10-5mM ginsenoside Rgl, had no effect on neuronal differentiation. These findings confirmed that fate decision of newborn rat mesencephalic progenitors could be manipulated by environmental signals. Only IL-1 could be used to predispose mesencephalic neural progenitors to enrich cell yield in a neuronal phenotype before cell transplantation. (2) The effects of CNTF and IL-1 on neural progenitor differentiation were dose-related. (3) Coeffects of ELF-EMF and cytokines were neither synergized nor antagonized, implying a potential role of organism EMF during CNS development. (4) Exposure for different time to 5/10/20/40 Hz(8 mT) and 5Hz(4 mT)ELF-EMFs stimulated neurogenesis of mesecephalic neural progenitor cellsr 20 Hz EMF showing the maxium effect. Their effect mode was frequency-specific; magnitude of ELF-EMFs might be another involved factor. In addition, 10/20/40 Hz EMF enhanced TH expression. The ELF-EMFs had no impact on neurite outgrowth. It was concluded that ELF-EMF, with the advantage of economy, convenience, as well as easy control, might be an effective method ex vivo to manipulate neural progenitors differentiation in stem-cell therapy.The possible mechanism of the ELF-EMFs effects onneurogenesis of mesencephalic progenitors was further explored. By the analysis of cell cycle disturbution and the examination of mashl, neuroD and notchl mRNA expression in proliferating or differentiating neural progenitors, the findings implied an important role of neuroD in controlling the neuronal fate commitment in mesencephalic neural progenitors from newborn rats. Upregulation of neuroD mRNA expression might underlie ELF-EMF effect on promoting mesencephalic progenitors to a neuronal phenotype. In addition, the immediate ELF-EMF exposure might induce cell cycle arrest, thus also contributing to its stimulating effect of neurogenesis from mesencephalic neural progenitors.In general, the application of ELF-EMFs in manipulating neural progenitor differentiation shows a great deal of promise for accelerating the stem-cell therapy from the laboratory to the clinic. I...