| Background and objectiveIn hospital,permanent pacemaker is treated as the only treatment forⅡtype of second or third degree atrioventricular block; after all, pacemaker as a foreign body, the battery of which needs to be replaced, makes a great deal of inconvenience to patients, is there a better way to treat block? In the past, some scholars transplanted bone marrow mesenchymal stem cells (BMSCs) for treatment of atrioventricular block, and obtained certain effects.BMSCs as a kind of multi-differentiation cells in the bone marrow microenvironment ,can be induced into neural cells, adipocytes, osteoblasts, cardiac cells, liver cells and other cells.Recent experiments show that BMSCs, which were cultrued in vitro, can induced differentiation into cardiomyocyte-like cells by 5 - azacytidine (5-aza). At the same time, the number of connexin 43 (Cx43) on cell membrane, which could connnect with the cardiac cells to form gap junctional intercellular communication (GJIC) and plays the role of cardiac pacing conduction,was increaseing. In this study, we used this feature of induced BMSCs, transplanted them into the atrioventricular node of atrioventricular block model and explored their therapeutic effec to atrioventricular block through monitoring their body surface electrocardiogram.Materials and methodsThe BMSCs were separated and cultured from New Zealand rabbit bone marrow by discontinuous Percoll separation medium density gradient centrifugation. The BMSCs were expanded from primary generation to the forth generation in vitro, and were induced by 5-aza. Inverted microscope was used to observe differentiation of the BMSCs and morphology of the cardiomyocytes.Following right thoracotomy and pericardiotomy, 150μl of 70% ethanol was injected into the myocardium5-8mm below the epicardial surface between the aortic root and the right atrial wall using the epicardial fat pad as a landmark of the injection point.Ten days after the surgery,the rabbits were observed body surface electrocardiogram. Those who still had atrioventricular block were given thoracotomy again.The cells transplanted treatment group was transplanted induced BMSCs which had been labeled by DAPI ,into atrioventricular node.The control group was not given any treatment; the medium treatment group were injected with medium treatment; cell transplantation group were transplanted induced BMSCs for treatment.After treatment, the surface ECG of rabbits were recorded every two days.We observed the transplanted BMSCs'survival state and distribution area by immunofluorescence.Results1. Under direct vision of thoracotomy, a stable model of atrioventricular block can successfully built through injecting 70% alcohol into the rabbit's atrioventricular node.2. After 2 weeks of treatment, detected by surface ECG, the rabbit atrioventricular block of control group is not self-improvement (p> 0.05); the culture medium treated rabbits'atrioventricular block were no significant changes (p> 0.05 ); and in the cell transplantation treatment group, part of the rabbit atrioventricular block have significantly improved (p <0.05).3. By rapid frozen section and the fluorescence electron microscope, the BMSCs grow well in the transplant site; but cells grow irregularly, and were lack of consistent direction.Conclusion1. By injecting 70% alcohol into the rabbit atrioventricular node, atrioventricular block model can be successfully constructed .2. After differentiate into cardiomyocyte-like cells,the autologous bone marrow mesenchymal stem cells have a certain of therapeutic effect in atrioventricular block.3. Autologous BMSCs after induction growed well in atrioventricular node. |
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