The integration and functional evaluation of rabbit pacing cells transplanted into the left ventricular free wall

Abstract

To evaluate the feasibility of cell transplantation to treat bradyarrhythmia, we analyzed the in vivo integration and pacing function after transplantation of mHCN4-modified rabbit bone marrow mesenchymal stem cells (MSCs) into the rabbit left ventricle free wall epicardium. In our investigation, we injected MSCs transduced with or without mHCN4 into the rabbit left ventricle free wall epicardium. Chemical ablation of the sinoatrial node was performed and bilateral vagus nerves were sequentially stimulated to observe premature left ventricular contraction or left ventricular rhythm. We found that the mHCN4-transduced MSC group had a significantly higher ventricular rate and a shorter QRS duration than that of the control and EGFP group. Furthermore, the mHCN4-transduced MSCs, but not the control cells, gradually adapted long-spindle morphology and became indistinguishable from adjacent ventricle myocytes. The modified MSCs showed pacing function approximately 1 week after transplantation and persisted at least 4 weeks after transplantation. In conclusion, a bradyarrhythmia model can be successfully established by chemical ablation of the sinoatrial node and sequential bilateral vagus nerve stimulation. The mHCN4-modified rabbit MSCs displayed evident dynamic morphology changes after being transplanted into rabbit left ventricle free wall epicardium. Our studies may provide a promising strategy of using modified stem cell transplantation to treat bradyarrhythmia.

Keywords: biological pacing.; bone marrow mesenchymal stem cell; mHCN4; subepicardial transplantation.

Figure 1

A: If curve of cells in the mHCN4 group; B: No If can be detected in cells of the EGFP group; C: Tail current in mHCN4 cells when polarized to +20mV; D: If activation curve in mHCN4 cell.

Figure 2

Sinus rhythm and ventricle rhythm (arrow) after vagal nerve stimulation at 2 weeks after transplantation; A: control group, B: EGFP group, C: mHCN4 group (chart drive speed was 25 mm/s).

Figure 3

Transplanted cells observed by HE staining (x400); black arrow indicates transplanted cells, red arrow indicates host ventricle myocytes. A: Three days after transplantation, B: One week after transplantation, C: Two weeks after transplantation. D: Four weeks after transplantation.

Figure 4

Cx43 and Cx45 expression determined by DAB staining between transplanted cells and host cells; red arrow indicates positive signal, brown linear granulates (x400). 1: CX43, 2: CX45; A: Control group, B: EGFP group, C: EGFP-mHCN4 group.

Figure 5

Immunofluorescence of EGFP (Green) and mHCN4 (Red); nuclei were stained by DAPI (blue, x 400). 1: 3 days after transplantation, 2: 1 week after transplantation, 3: 2 weeks after transplantation, 4: 4 weeks after transplantation; A: control group, B: EGFP group, C: EGFP-mHCN4 group.