Study On The Galvanotaxis Of The Cells Under Non-DC Electric Fields

Numerous studies show that steady ion current is involved in the process of wound healing and embryogenesis.In cracking the function of embryonic current and applying physiological strength electric field to the cells,the endogenous electric field is found to be capable of regulating the migration and division of the cells,as well as neural growth.In vitro,most kinds of the cells have the ability of migrating along with the direction of the imposed physiological-strength electric field,which is called galvanotaxis,or electrotaxis.Understanding of the galvanotaxis will give us insights about how they perform in vivo,Therefore,we can alter the imposed electric field to study the cells' behavior to further regulate their behavior in vivo,and finally to regulate regeneration,development,and etc.At the moment,various cells have been studied on their galvanotaxis under DCEF(direct current electric field),including mechanism and quantitative studies.Meanwhile numerous clinical studies show that non-DCEF(non-direct current electric field)help wound healing and regeneration.However,galvanotaxis under non-DCEF and comparison of galvanotactic responses between non-DCEF and DCEF remain elusive.Therefore,using the classic galvanotatic chamber with timelapse technique,we studied the migration of D.discoideum under DCEF,pDCEFs(pulsed direct current electric fields)and bpEFs(bipolar pulse electric fields)to elucidate the difference of the behavior of the cells between non-DCEF and DCEF so as to relate the galvanotaxis of the cells in DCEF with those in non-DCEFs that are widely applied in clinical studies of wound healing.In this article,we designed a novel stimulator according to the electrical property of galvanotactic chamber and agar bridges,whose output voltage range was from-120 V to 120 V,frequency was up to 50 Hz.When changed settings,the stimulator was able to impose electric field in the cham'ber with various waveforms,such as DCEF,pDCEF,bpEF.Using this device,we investigated the influence of different parameters of the electric fields on the galvanotaxis of the cells,such as duty cycle,frequency,polarity,directedness,trajectory speed,angle,and voltage transient,etc.The results show that,1)Similar to the ones in DCEF,the cells under polar non-DC electric fields also migrated along with the direction of the electric field,and their directedness may depend upon the accumulative charge in a single repetitive period.2)The directional characteristics of the cells under the electrically neutral EFs were the same as that without EF,but their trajectory speeds were much higher.Among all the electric fields studied in this research,10 Hz 80%duty cycle bpEF turned out to be the best to induce directional migration of the cells with narrowest distribution of the angles of the trajectory,meanwhile,10 Hz 50%duty cycle bpEF triggered the highest trajectory speed.3)The parameter of EMR we introduced in this article,is especially suitable for distinguishing the directional characteristics between two cell groups with similar directedness and different trajectory patterns.The results show that non-DCEFs can also induce galvanotaxis just like DCEF does,some of which induce better directional characteristics and/or trajectory speed of the cells.The net charge in a single period of the electric field determines the migrating direction of the cells,which underpins the galvanotactic response.The voltage transient,the polarity and the frequency of the electric fields also contribute to the galvanotaxis of the cells.The results suggest that electric pulses are vital to galvanotaxis and non-DCEF is promising in both basic and clinical researches.