HCN4是哺乳动物窦房结等自律性高的区域优势表达的HCN通道亚型，我们早期研究证实，经HCN4基因修饰的骨髓间充质干细胞可使共培养的乳鼠心肌细胞搏动频率增加。但HCN4激活所需时间长，对超极化反应慢，构建的生物起搏细胞与植入周围心肌细胞沟通不良，这些缺点使得单纯HCN4转染构建的生物起搏细胞难以满足临床实际运用的要求。窦房结与周围心肌组织通过缝隙链接蛋白（Cx）形成联系，以Cx45为主。Cx45在窦房结细胞与邻近心肌细胞之间发挥了重要的桥梁作用。我们设想，以慢病毒和脂质体为载体，将HCN4基因和Cx45基因共同转染至骨髓间充质干细胞，产生起搏电流的同时促进起搏电流的传导，构建长期有效的生物起搏细胞，在动物实验中进行验证，为临床应用打下基础。

Hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) is the most predominant isoform in sinoatrial node which is the normal pace making region of the heart. Extensive research toward creating a biological pacemaker by enhancement of HCN4 expression has been performed. We have demonstrated that mesenchymal stem cells (MSCs) transfected with HCN4 genes were capable of increasing the spontaneous beating rate of co-cultured cardiac myocytes in our early study.However, the activaton of HCN4 needs long time,and it's response to hyperpolarization is slow.Furthermore ,there are poor communication between the biological pacemaker cells and implanted cardiomyocytes. These disadvantages make it difficult to meet the requirements of clinical application using biological pacemaker transfected with HCN4. In native sinus node, the connection between pacemaker cells and cardiomyocytes is mainly through connexin 45(Cx45). Cx45 plays an important role in bridge between adjacent cardiomyocytes and sinoatrial node cells.So our idea is, to generate biological pacemaker with MSCs transduced with HCN4 via transfection with a lentiviral vector. These MSCs are cocultured with neonatal rat ventricular myocytes, and while the pacemaker current is generated ,the pacemaker current conduction is promoted.The biological pacemaker constructed in this way will be reexamined in animal experiment,which lay the foundation for clinical application.