Editorial: Cardiac optogenetics: Using light to observe and excite the heart

Cardiac optogenetics: Using light to observe and excite the heartThis is the editorial to the special edition "Cardiac optogenetics: using light to observe and excite the heart.The application of fluorescent voltage sensitive dyes to study excitable cells was established 50 years ago (Tasaki et al., 1969) but only recently has chemical and imaging technology developed sufficiently for its mainstream use.In contrast, the field of cardiac optogenetics was established only a decade ago by publications demonstrating lightmediated excitation of the heart in mice (Bruegmann et al., 2010), zebrafish (Arrenberg et al., 2010) and cardiomyocytes in vitro (Abilez et al., 2011;Jia et al., 2011).Ever since, the subject of optogenetics has expanded to encompass a number of different applications.Early translational approaches considered light-mediated cardiac resynchronization therapy (Nussinovitch and Gepstein 2015), defibrillation (Bruegmann et al., 2016;Crocini et al., 2016;Nyns et al., 2017) and cardioversion (Bruegmann et al., 2018;Nyns et al., 2019).In this regard, Diaz-Maue et al. developed a mesh of electrodes and LEDs to correlate electrical rotor activity during arrhythmias with defibrillation efficacy of optogenetic stimulation and Patrick Boyle's group explored in simulations the use and application of anion conducting channelrhodopsins (Ochs et al.).While leading also to depolarization in cardiomyocytes (Kopton et al., 2018), the much larger ion conductance improved the efficiency of optogenetic defibrillation, which is an intriguing result directly demanding experimental verification.State-of-the-art solutions for one of the biggest hurdles of translation, the development of implantable light devices has been expertly summarized and thoughtfully discussed by Igor Efimov's group in this issue (Madrid et al.).