RESUMO
OBJECTIVE: To study the functional properties of I(f) channels and the changes in mechanical activity of mouse mesenchymal stem cells (mMSCs) transfected with mHCN4. METHODS: mMSCs were purified by using CD11b-immunomagnetic microbeads and transfected with pMSCV-mHCN4-EGFP or pMSCV-EGFP. We examined the kinetic characteristics of the mHCN4 channel. The morphological changes of positively transfected mMSCs were investigated at the same time. RESULTS: The I(f) current recorded from the experimental group was sensitive to extracellular Cs(+) (-44.5 +/- 4.2 vs. -5.5 +/- 1.0 pA/pF, p < 0.001). The half-maximal activation was -99.0 +/- 5.8 mV. The time constant of activation was 451 +/- 61 ms under -140 mV. The control cells did not show the current under the same conditions. The absolute values of half-maximal activation decreased in the presence of cAMP or cGMP in the experimental group (-78.6 +/- 10.4 and -85.7 +/- 8.6 vs. -99.0 +/- 5.8 mV, respectively, p < 0.05). mMSCs transfected with pMSCV-mHCN4-EGFP could form spontaneous beating cells. Extracellular Cs(+) decreased the beating rate significantly (196 +/- 50 vs. 66 +/- 23 bmp, p < 0.01). CONCLUSIONS: Functional I(f) channels can be reconstructed in mMSCs infected with mHCN4. mMSCs modified by successful transfection with mHCN4 can differentiate so as to develop spontaneous mechanical activity.
