Abstract 202: Engineering Artificial Sinus Node by Reprogrammed Cardiomyocytes

The lack of clinically relevant sinoatrial node (SAN) disease model makes the pathophysiological investigation and therapeutic development stagnant. We hypothesize that engineering SAN by TBX18 somatic-reprogrammed cardiomyocytes on the three-dimension (3D) scaffold could create an in vitro SAN model, sharing similar features with a native SAN. Methods: In addition to neonatal rat ventricular cardiomyocytes (NRVMs) alone, we chose cardiosphere-derived cells (CDCs), or fibroblasts as supportive cells with different mixing ratios to construct engineered SAN. Hydrogel scaffolds including matrigels or platelet gels were used and compared. The engineered tissue was reprogrammed by TBX18 over-expression. Results: The over-expression of TBX18 increased HCN4 and CX45 transcriptions in cardiomyocytes. A stable spontaneous beating rate could be created in TBX18-reprogrammed engineered tissue, made of NRVMs and fibroblasts with matrigel scaffold (beating rate, TBX18 vs. control: 105.0 ± 10.7 bpm vs. 35.5±7.1 bpm, n=12, P<0.001). Although spontaneous beating could be observed in reprogrammed engineered tissues by NRVM alone, NRVM with CDCs, or NRVMs with CDCs and fibroblasts, the beating rates were not stable and slower. The beating rate in engineered tissue did not differ between scaffolds of matrigel and platelet gel. However, inter-experimental variation is higher in platelet gels, compared to matrigels. By immunofluorescent staining, an unique spatial distribution of NRVMs and fibroblasts was identified. NRVMs formed the central core of engineered tissues, encapsulated by fibroblasts, which was similar to a native SAN. The application of a sympathomimetic drug (epinephrine) doubled the beating rate of reprogrammed engineered tissue (P=0.02, n=6-8). Conclusions: A pilot model of engineered SAN was established by TBX18-reprogrammed cardiomyocytes. The supportive cells such as fibroblasts played an important role in tissue engineering of SAN.