Model of optical biopacemaker based on integration of photosensitive cardiomyocytes into cardiac culture

The methods of cardiac conduction system recovery with the use of reprogrammed cells and biomaterials, which could provide a stable physiological heart rate throughout the lifetime, are currently studied for possible applications in the heart rhythm disorder treatment. The main issue of intramyocardial transplantation is the transplanted cells' survival and electrophysiological connections formation with the recipient cardiomyocytes. In this paper, in search for working approaches for creating an optical biological pacemaker, we studied the effectiveness of various methods of photosensitive cardiac ChR2-HL-1 line cells integration into neonatal rat cardiac monolayers. For the study, two approaches of co-cultivation were selected: isolated cells and clusters integration of the Ch2-HL-1 line in various concentrations into monolayers. The effectiveness of the obtained model pacemaker was evaluated by the following means: registration of excitation waves initiated by optical stimulation, which affected only cells of the Ch2-HL-1 line, was carried out by optical mapping; immunocytochemical analysis methods were used to characterize the morphology of the obtained co-cultures and to assess the degree of the integration of the embedded structures into the monolayer. In the course of the research it was shown that the most effective method of integration of cells in the primary culture is the cluster method: 100 % of samples with clusters, integrated after 6 hours of monolayer cultivation, showed stable generation of excitation waves at physiologically significant external stimulation frequencies, compared with 88 % for specimens with integrated isolated cells at frequencies lower than physiological. Moreover, the samples with the cluster integration method turned out to be much more resistant (100 % in the cluster method and 25 % in the infusion of isolated cells] to sodium channel inhibitor, lidocaine. The efficiency of integration depends on the conditions of cell growth, which is discussed in more detail in the results of the study. The obtained results are applicable in the development of a biological pacemaker.