【Abstract】 Objective To investigate the expression of connexin 40 (Cx40) and hyperpolarization-activated cycl icnucleotide-gated cation channel 4 (HCN4) in rat bone marrow mesenchymal stem cells (BMSCs) cocultured with the sinoatrialnode (SAN) tissues in vitro, so as to evaluate the possibil ity of BMSCs differentiation into SAN cells. Methods BMSCs wereisolated from Sprague Dawley rats (aged 4-6 weeks, male or female) by the adhesive method and cultured; BMSCs at the 3rdpassage were marked with carboxyfluorescein succinimidyl ester, and then were incubated on 6-well culture plate; cell climingsl ices were prepared at the same time. SAN tissue was taken and cut into 0.3 cm × 0.3 cm mass, and then placed into 4℃ PBSsolution. The SAN tissue mass was cocultured with marked BMSCs at the 3rd passage for 3 weeks as the experimental group, andBMSCs at 3rd passage were cultured alone for 1 week as the control group. At 1, 2, and 3 weeks after coculture, the mean integratedabsorbance (MIA) values of Cx40 and HCN4 were measured by Image pro plus 5.0 through the method of immunohistochemistry,and the mRNA expressions of Cx40 and HCN4 were identified by real-time fluorescent quantitative PCR. Results TheMIA values of Cx40 and HCN4 in the experimental group were higher than that in the control group, showing significantdifferences (P lt; 0.01). In the experimental group, the expressions of Cx40 and HCN4 increased gradually with time. The longerthe culture time was, the higher the expressions of Cx40 and HCN4 were, showing significant differences (P lt; 0.05). The mRNAexpressions of Cx40 and HCN4 in the experimental group were significantly higher than those in the control group (P lt; 0.01); inthe experimental group, the mRNA expressions of Cx40 and HCN4 increased gradually with time, showing significant differencesbetween different time points (P lt; 0.05). Conclusion The expressions of Cx40 and HCN4 increase obviously after coculturingBMSCs with SAN tissue, indicating that BMSCs could differentiate into SAN cells by coculturing with SAN tissue in vitro.
Objective To review the current status and problems in developing cardiac biological pacemaker(CBP) by cell transplantation. Methods The l iterature over the past decade concerning CBP constructed through celltransplantation was reviewed and summarized. Results Experiments in vivo testified that the cell transplantation was feasible for CBP construction, and the transplantation of sinus atrial node cell and stem cell was still the predominant method for constructing CBP. However, such problems as difficult ampl ification of transferred cardio muscle cell, low success rate of CBP construction as well as unstable function of CBP make it lag behind the tremendous cl inical demands. The gene transfection technology might be one of the approaches to resolve these issues. Conclusion As one feasible method for CBP construction, the cell transplantation has a bright future in the cl inical appl ication and is worthy of further study.
Objective To investigate the feasibility of recombinant lentivirus (LVs) mediated hyperpolarization- activated cyclic nucleotide-gated cation channel 4 (HCN4) gene transfecting rat bone mesenchymal stem cells (BMSCs) so as to construct the biological pacemaker cells. Methods Sprague Dawley rats at the age of 3-5 weeks were selected to isolate and culture BMSCs using modified whole bone marrow adherent culture method. LVs was used as carrier, and enhanced green fluorescent protein (EGFP) as marker to build LVs-HCN4-EGFP virus liquid. The BMSCs at passage 3 were transfected with LVs-HCN4-EGFP virus liquid (experimental group) and LVs-EGFP null virus liquid (control group). Fluorescence microscope was used to observe the green fluorescent protein expression after 24, 48, and 72 hours of transfection; Western blot method was used to detect the HCN4 protein expression. The electrophysiology was used to detect the pacemaker current in the experimental group. Results After transfection, BMSCs in the experimental group showed normal morphology and good growth; scattered green fluorescence could be seen at 48 hours under fluorescence microscope, with a transfection efficiency of about 10%; the fluorescence expression increased slightly, with the transfection efficiency of 20% to 25% at 72 hours. While no expression of green fluorescence was seen in the control group. Western blot results showed that the same band expression as a relative molecular mass of HCN4 protein were found at 72 hours after transfection in the experimental group, only weak expression of protein band was seen in the control group; the gray value of the experimental group (33.75 ± 0.41) was significantly higher than that of the control group (23.39 ± 0.33) (t=17.524, P=0.013). In the experimental group, the pacemaker current was recorded, and it could be blocked by CsCl, in accordance with the characteristics of pacemaker current. Conclusion The recombinant LVs mediated HCN4 gene is successfully transfected into rat BMSCs, and the expression of HCN4 protein and the pacemaker current can be detected.
Objective To observe the change of sino-atrial nodal tissue structure and ectopic pacing function after xenogenic sino-atrial nodal tissue transplanted into left ventricular wall, so as to provide new ideas for the treatment of sick sinus syndrome and severe atrioventricular block. Methods Seventy healthy rabbits were selected, male or female, and weighing 1.5-2.0 kg. Of them, 42 were used as reci pient animals and randomly divided into sham operation group, warm ischemia transplantation group, and cold ischemia transplantation group (n=14), the other 28 were used as donors of warm ischemia and cold ischemia transplantation groups, which were sibl ing of the recipients. In recipients, a 6-mm-long and about 2-mm-deep incision was made in the vascular sparse area of left ventricular free wall near the apex. In sham operation group, the incision was sutrued directly by 7-0 Prolene suture; in cold ischemia transplantation group, after the aortic roots cross-clamping, 4 ℃ cold crystalloid perfusion fluid infusion to cardiac arrest, then sinoatrial node were cut 5 mm × 3 mm for transplantation; in warm ischemia transplantation group, the same size of the sinus node tissue was captured for transplantation. After 1, 2, 3, and 4 weeks, 3 rabbits of each group were harvested to make bradycardia by stimulating bilateral vagus nerve and the cardiac electrical activity was observed; the transplanted sinus node histology and ultrastructural changes were observed. Results Thirty-six recipient rabbits survived (12 rabbits each group). At 1, 2, 3, and 4 weeks after bilateral vagus nerve stimulation, the cardiac electrical activity in each group was significantly slower, and showed sinus bradycardia. Four weeks after operation the heart rates of sham operation group, warm ischemia, and cold ischemia transplantation group were (81.17 ± 5.67), (82.42 ± 7.97), and (80.83 ± 6.95) beats/ minute, respectively; showing no significant difference among groups (P gt; 0.05). And no ectopic rhythm of ventricular pacing occurred. Sino-atrial nodal tissue survived in 6 of warm ischemic transplantation group and in 8 of cold ischemia transplantation group; showing no significant difference between two groups (P gt; 0.05). Two adjacent sinoatrial node cells, vacuole-l ike structure in the cytoplasm, a few scattered muscle microfilaments, and gap junctions between adjacent cells were found in transplanted sinus node. Conclusion The allograft sinus node can survive, but can not play a role in ectopic pacing.
Objective Through analyzing BKCa channel expression in atrial fibroblasts in patients with sinus rhythm and atrial fibrillation (AF), to explore the mechanism of myocardial fibrosis and provide new therapeutic strategies for the treatment and reversal of AF structure reconstruction. Methods We selected 10 patients of rheumatic heart valvular disease who underwent valve replacement surgery. They were 5 patients with sinus rhythm (a sinus rhythm group, 2 males and 3 females with an average age of 49.1±8.3 years) and 5 with AF (an AF group, 3 males and 2 females with an average age of 50.3±5.8 years). About 100 mg tissue was obtained from the right auricula dextra, and the atrial fibroblasts were cultured by tissue block adherence method, and the expression of BKCa channel genes and proteins in cultured fibroblasts was detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting methods. Results (1) The general data of 10 patients between the AF group and the sinus rhythm group were compared. There was no significant difference between the two groups in age (t=1.21, P=0.67) and sex (t=2.56, P=0.75). There was statistical difference in the left atrial diameter and the right atrium diameter between the two groups (t=19.45, P=0.01; t=23.52, P=0.06); (2) the mRNA expression of BKCa subunit was detected by qRT-PCR method, and there was no significant difference in the mRNA expression of BKCa α and BKCa β1 between the two groups (t=3.14, P=0.79; t=2.88, P=0.69); (3) the expression of BKCa protein was detected by western blotting method, and there was no significant difference in the protein expression of BKCa α and BKCa β1 between the two groups (t=0.55, P=0.31; t=0.73, P=0.46). Conclusion BKCa pathway may not be involved in the pathogenesis and maintenance of AF, but it may play an important role in the process of myocardial fibrosis.
Objective To study the influence of ischemia-reperfusion on the expression of the hyperpolarization activated cycl icnucleotide gated cation channel 4 (HCN4) and to discuss the mechanism of functional disturbance of sinoatrial node tissue (SANT) after ischemia reperfusion injury (IRI). Methods Eighty five healthy adult rabbits, weighing 2-3 kg, were randomly divided into 3 groups: control group [a suture passed under the root section of right coronary artery (RCA) without l igation, n=5], experimental group A (occluding the root section of RCA for 30 minutes, then loosening the root 2,4, 8 and 16 hours, n=10), experimental group B (occluding the root section of RCA for 1 hour, then loosening the root 2, 4,8 and 16 hours, n=10). At the end of the reperfusion, the SANT was cut off to do histopathological, transmission electronmicroscopical and immunohistochemical examinations and semi-quantitative analysis. Results The result of HE stainingshowed that patho-injure of sinoatrial node cell (SANC) happened in experimental groups A and B after 2 hours of reperfusion, the longer the reperfusion time was, the more serious patho-injure of SANC was after 4 and 8 hours of reperfusion, SANC reached peak of damage after 8 to 16 hours of reperfusion; patho-injure of SANC was more serious in experimental group B than in experimental group A at the same reperfusion time. Immunohistochemical staining showed that the expression of HCN4 located in cellular membrane and cytoplasm in the central area of SANC and gradually decreased from the center to borderl ine. The integral absorbance values of HCN4 expression in the control group (397.40 ± 34.11) was significantly higher than those in the experimental group A (306.20 ± 35.77, 216.60 ± 18.59, 155.40 ± 19.11 and 135.00 ± 12.30) and in the experimental group B (253.70 ± 35.66, 138.70 ± 13.28, 79.10 ± 9.60 and 69.20 ± 8.42) after 2, 4, 8 and 16 hours of reperfusion (P lt; 0.05). With reperfusion time, the expression of HCN4 of SANC decreased, which was lowest after 8 hours of reperfusion; showing significant difference among 2, 4 and 8 hours after reperfusion (P lt; 0.05) and no significant difference between 8 and 16 hours after reperfusion (P gt; 0.05). At the same reperfusion time, the expression of HCN4 was higher in the experimental group A than in the experimental group B. The result of transmission electron microscope showed that ultramicrostructure of SANC was damaged after reperfusion in experimental groups A and B. The longer the reperfusion time was, the more serious ultramicrostructure damage of SANC was, and reached the peak of damage after 8 hours of reperfusion. Ultramicrostructure of SANC was not different between 8 and 16 hours of reperfusion. At the same reperfusion time, the ultramicrostructure damage of SANC was moreserious in experimental group B than in experimental group A. Conclusion IRI is harmful to the morphous and structure ofSANC, and effects the expression of HCN4 of SANC, which is concerned with functional disturbance and arrhythmia.