Table 4.

Combined gene-cell biopacemaking approaches.

Gene-cell approach	Methodology and experimental details	References
HCN1-expressing fibroblasts fused with freshly isolated myocytes	HCN1-expressing fibroblasts were fused with freshly isolated guinea pig ventricular myocytes and formed fibroblast-myocyte heterokaryons with biological pacemaker activity.	Cho et al., 2007
HCN1-expressing hMSCs	Genetically-engineered MSCs transfected with the human HCN1 gene expressed pacemaker If current. The effect of the hHCN1-transfected MSCs on cardiomyocyte excitability was determined by coculturing genetically engineered MSCs with neonatal rabbit ventricular myocytes.	Zhou et al., 2013
HCN2-expressing hMSCs	Genetically modified hMSCs expressed functional cardiac pacemaker gene HCN2 and induced spontaneous pacemaker activity triggering the contraction of ventricle cardiomyocytes in vitro and in vivo.	Potapova et al., 2004
	HCN2-expressing hMSCs were introduced into the right ventricular apex in dogs and biological pacemaker activity was obtained. Pacing was stable for 6 weeks with no cellular or humoral rejection.	Plotnikov et al., 2007
HCN4-expressing rabbit MSCs	In vivo integration and pacing function were achieved after the transplantation of mHCN4-modified rabbit MSCs into the rabbit left ventricle free wall epicardium. Pacing function of the modified MSCs persisted for at least 4 weeks after transplantation.	Zhang et al., 2012
HCN4-expressing rat MSCs	Genetically modified rat MSCs carrying HCN channels expressed pacemaker If current in vitro. Pacemaking activity was observed after transplantation into the rat host heart.	Nong et al., 2013
TBX18-expressing cardiomyocytes	The conversion of rodent cardiomyocytes to SAN cells in vitro and in vivo using the expression of Tbx18 was performed. Focal Tbx18 gene transfer in the guinea-pig ventricle induced ectopic pacemaker activity, correcting a bradycardic disease phenotype.	Kapoor et al., 2013
SHOX2-overexpression in ESCs	The overexpression of SHOX2 induced the differentiation of ESCs into pacemaker cells and the transplantation of embryoid bodies from SHOX2-transduced ESCs into the left ventricles of rat hearts with a complete heart block. Consistent pacing ability was demonstrated.	Ionta et al., 2015
HCN2/SkM1-overexpression in CPCs	Functional delivery of HCN2/SkM1 via human CPCs demonstrated effectiveness in bradycardia models. In particular, the lentiviral transduction of HCN2 and SkM1 was more efficient than their nucleofection-mediated gene transfer. Moreover, virally transduced cells survived better in vivo.	Végh et al., 2021

MSCs, mesenchymal stem cells; hMSCs, human MSCs; SAN, sinoatrial node; ESCs, embryonic stem cells; CPCs, cardiomyocyte progenitor cells.