Electrically Conductive Biohybrid Hydrogel Prevents Post-Infarct Cardiac Arrhythmia and Supports hiPSC-Cardiomyocyte Function

Myocardial infarction (MI) causes cell death, disrupts electrical activity, triggers arrhythmia, and results in heart failure, whereby 50% of MI patients die from sudden cardiac death (SCD). Due to limited renewal capacity of adult cardiomyocytes (CM), the MI-induced CM loss proceeds to the formation of fibrotic tissue and subsequent ventricular wall dilation. Fibrotic tissue is electrically insulating, and such a low conductivity, together with hetero-cellular interactions in the scar border zone, contribute to electrical decoupling of the remaining viable CMs in the infarcted region and promote asynchronous ventricular contractions. The most effective therapy for SCD prevention is implantable cardioverter defibrillators (ICDs). However, ICDs contribute to adverse remodeling and disease progression and do not prevent arrhythmia. Moreover, there is a gap in designing an electrically conductive hydrogel that prevents post-MI arrhythmia and has the potential to be combined with CMs. We developed an injectable collagen-PEDOT:PSS hydrogel that protects infarcted hearts against ventricular tachycardia (VT) and can be combined with hiPSC-cardiomyocytes to promote partial cardiac remuscularization.

 

Figure 1. schematic of the project.

 

We have studied gelation kinetics, electrical conductivity as well as the hydrogel micromorphology by scanning electron microscopy. Moreover, we generated engineered cardiac tissues based on hiPSC-derived CMs and these hydrogels and studied cell survival, microcellular organization of contractile machinery and calcium handling of these cells in the tissues for them up to 40 days. Moreover, RNA-sequencing analyses revealed a shift towards more mature CMs within electrically conductive hydrogels without any external stimuli. Eventually we have transplanted the hydrogels in a cryoinfarction model of MI in mouse. We have assigned five groups, including sham, MI, collagen, collagen-PEDOT:PSS, and collagen-PEDOT:PSS containing hiPSC-derived CMs.
PEDOT:PSS improves collagen gel formation and results in a faster gelation. It transforms single-fibrillar collagen morphology into entangled thick helical microfibrous morphology in collagen-PEDOT:PSS and increases electrical conductivity from ~41 mS/cm for collagen to ~65 mS/cm for collagen-PEDOT:PSS. Compared to cells in collagen hydrogels, hiPSC-CMs in collagen-PEDOT:PSS hydrogels exhibit near-adult sarcomeric length (~2 µm), improved contractility (~500%), enhanced calcium handling, and conduction velocity (~700%). RNA-sequencing data revealed an upregulation of genes associated with conduction, structure, energetics, oxidative phosphorylation and fatty acid oxidation, calcium handling, and cell-ECM interactions, indicating enhanced maturation and improved cell-matrix interactions in hiPSC-CMs within collagen-PEDOT:PSS hydrogels. Injecting collagen-PEDOT:PSS hydrogels in infarcted mouse hearts results in a ~400% decrease in ventricular tachycardia occurrence compared to MI, reaching to the levels of healthy hearts. Furthermore, hiPSC-CM implementation results in improved heart function (fraction shortening: 25% vs. ~18% in MI).
Collectively, the here-developed hydrogel showed great potential to promote stem cell derived CMs maturation and to protect the infarcted heart against ventricular tachycardia. Finally, collagen-PEDOT:PSS hydrogels offer a versatile platform for treating injuries in hearts and other electrically sensitive tissues.