As an
alternative strategy to electronic pacemaker devices, we explored the feasibility of converting normally-quiescent ventricular myocytes into pacemakers by
somatic cell fusion. The idea is to create chemically-induced fusion between myocytes and syngeneic fibroblasts engineered to express HCN1 pacemaker
ion channels (HCN1 fibroblasts), in normally-quiescent myocardium. HCN1-expressing fibroblasts formed stable heterokaryons with myocytes, generating spontaneously-oscillating action potentials as well as ventricular pacemaker activity
in vivo and provides a platform for an autologous, non-viral, adult
somatic cell therapy. We also converted a
depolarization-activated
potassium-selective channel, Kv1.4, into a hyperpolarization-activated non-selective channel by site-
directed mutagenesis (R447N, L448A, and R453I in S4 and G528S in the pore).
Gene transfer into ventricular myocardium demonstrated the ability of this construct to induce pacemaker activity, with spontaneous
action potential oscillations in adult ventricular myocytes and idioventricular rhythms by
in vivo electrocardiography. Given the sparse expression of Kv1 family channels in the human
ventricle,
gene transfer of a synthetic pacemaker channel based on the Kv1 family has therapeutic utility as a biological alternative to electronic pacemakers.