| dc.description.abstract | Polypyrrole (PPy) exhibits good optical property and biocompatibility, so we used PPy to construct a bioreactor for electrical stimulation application. Rat cardiomyoblast cells, H9C2, were seeded to the bioreactor which was connected with electrodes in two opposite ends. We applied external power supply and Arduino controller to generate monophasic pulse current (1 Hz and 2 ms) and constant direct current (DC) in electric fields of 1 or 7 V/cm to investigate the effects of electrical stimulation mode as well as electrical fields on the activity, morphology and differentiation of H9C2 cells. The MTT results showed that pulse stimulation at 1 and 7 V/cm both promoted cell activity, whereas constant DC demonstrated cell activity improvement only at 7 V/cm. Only 7 V/cm of pulse or constant DC can align H9C2 cells to parallel to electrical field, and constant DC resulted in better alignment than that of pulse group. The qPCR results showed that pulse and constant at 7 V/cm both enhanced the upregulation of GATA4, a cardiac transcription maker, in early stage of differentiation. Two mature cardiac markers, cardiac muscle troponin T (cTnT) and α-actinin, were also investigated during differentiation. The qPCR and Western blotting results showed that the RNA and protein expression levels of α-actinin were mainly dependent on electric field and independent of stimulation mode. Both RNA and protein expression levels of cTnT also increased with electric fields. However, the qPCR results indicated that pulse stimulation up-regulated cTnT gene higher than that of the constant DC group, especially at 7 V/cm. Interestingly, the Western blotting results showed that these two stimulation modes demonstrated similar cTnT protein expression. We deduced that pulse stimulation decreased cell activity at 7 V/cm, and thus reduced cTnT synthesis. Finally, the immunostaining results demonstrated that 7 V/cm of pulse or constant DC both can align differentiated H9C2 cells due to their effects on cell orientation. Overall, our results suggested that PPy mediated electrical stimulation can promote cardiac myogenesis, and is potential for cardiac tissue engineering application
(DC) in electric fields of 1 or 7 V/cm to investigate the effects of
electrical stimulation mode as well as electrical fields on the activity,
morphology and differentiation of H9C2 cells. The MTT results showed
that pulse stimulation at 1 and 7 V/cm both promoted cell activity,
whereas constant DC demonstrated cell activity improvement only at 7
V/cm. Only 7 V/cm of pulse or constant DC can align H9C2 cells to
parallel to electrical field, and constant DC resulted in better alignment
than that of pulse group. The qPCR results showed that pulse and
constant at 7 V/cm both enhanced the upregulation of GATA4, a cardiac
transcription maker, in early stage of differentiation. Two mature cardiac
markers, cardiac muscle troponin T (cTnT) and α-actinin, were also
investigated during differentiation. The qPCR and Western blotting
results showed that the RNA and protein expression levels of α-actinin
were mainly dependent on electric field and independent of stimulation
mode. Both RNA and protein expression levels of cTnT also increased
with electric fields. However, the qPCR results indicated that pulse
stimulation up-regulated cTnT gene higher than that of the constant DC
group, especially at 7 V/cm. Interestingly, the Western blotting results
showed that these two stimulation modes demonstrated similar cTnT
protein expression. We deduced that pulse stimulation decreased cell
activity at 7 V/cm, and thus reduced cTnT synthesis. Finally, the
immunostaining results demonstrated that 7 V/cm of pulse or constant
DC both can align differentiated H9C2 cells due to their effects on cell
orientation. Overall, our results suggested that PPy mediated electrical
stimulation can promote cardiac myogenesis, and is potential for cardiac
tissue engineering application | en_US |