Kalkunte, N. | Search bioRxiv

bioRxiv2022

Engineering Alignment has Mixed Effects on hiPSC-CM Maturation

The potential of human induced pluripotent stem cell differentiated cardiomyocytes (hiPSC-CMs) is greatly limited by their functional immaturity. Strong relationships exist between CM structure and function, leading many in the field to seek ways to mature hiPSC-CMs by culturing on biomimetic substrates, specifically those that promote alignment. However, these in vitro models have so far failed to replicate the alignment that occurs during cardiac differentiation. We show that engineered alignment, incorporated before and during cardiac differentiation, affects hiPSC-CM electrochemical coupling and mitochondrial morphology. We successfully engineer alignment in differentiating hiPSCs as early as Day 4. We uniquely apply optical redox imaging to monitor the metabolic changes occurring during cardiac differentiation. We couple this modality with cardiac-specific markers, which allows us to assess cardiac metabolism in heterogeneous cell populations. The engineered alignment drives hiPSC-CM differentiation towards the ventricular compact CM subtype and improves electrochemical coupling in the short term. Moreover, we observe glycolysis to oxidative phosphorylation switch throughout differentiation and CM development. On the subcellular scale, we note changes in mitochondrial morphology in the long term. Our results demonstrate that cellular alignment accelerates hiPSC-CM maturity and emphasizes the interrelation of structure and function in cardiac development. We anticipate that combining engineered alignment with additional maturation strategies will result in improved development of mature CMs from hiPSC and strongly improve cardiac tissue engineering. Impact StatementThis work demonstrates the mixed effect of engineered structure in inducing matured function of human induced pluripotent stem cell -derived cardiomyocytes. Isolating the impacts of hiPSC-CM alignment on functionality is a necessary step in optimizing the culture conditions to develop cardiac cell therapies. Furthermore, our work has broader implications concerning how we understand the impact of mechanical microenvironments on stem cell differentiation and development.

bioengineering↗

bioRxiv2021

Towards prevention of re-entrant arrhythmias: Injectable hydrogel electrodes enable direct capture of previously inaccessible cardiac tissues

Re-entrant arrhythmias--the leading cause of sudden cardiac death--are caused by diseased myocardial tissue and consequent delayed myocardial conduction. Access to the coronary veins that cross the "culprit" scar regions where re-entry originates can provide improved pacing to these delayed regions, offering a novel opportunity to prevent ventricular arrhythmias and circumvent the need for painful defibrillation, risky cardiac ablation, or toxic and often ineffective antiarrhythmic medications. However, there are no pacing electrodes which are small or focal enough to navigate these tributaries. To address this need, we have developed an injectable conductive hydrogel that can fill the epicardial coronary veins and their mid-myocardial tributaries. When connected to a standard pacing lead, these injected hydrogels can be converted into flexible electrodes that directly pace the previously inaccessible mid-myocardial tissue. In our two-component system, hydrogel precursor solutions can be injected through a dual lumen catheter in a minimally invasive deployment strategy to provide direct access to the diseased regions with precision and ease. Mixing of the two solutions upon injection into the vein activates redox-initiated crosslinking of the gel for rapid in situ cure without an external stimulus. An ex vivo porcine model was used to identify the requisite viscosity and cure rate for gel retention and homogeneity. Ionic species added to the hydrogel precursor solutions conferred conductivity above target myocardium values that was retained after implantation. Successful in vivo deployment demonstrated that the hydrogel electrode filled the anterior interventricular vein with extension into the septal (mid-myocardial) venous tributaries to depths far more distal and refined than any current technologies allow. In addition to successful capture and pacing of the heart, analysis of surface ECG tracings revealed a novel pacing observation highly specific for and suggestive of capture of extensive swaths of septal myocardial tissue. This is the first report of an injectable electrode used to successfully pace the mid-myocardium and mimic physiologic conduction. Furthermore, in vivo cardiac electroanatomical mapping studies in an ablation scar model showed uniform capture along the hydrogel in the vessels as well as increased capture area compared to point pacing. Collectively, these findings demonstrate that this injectable hydrogel electrode can be deployed to scarred regions of the heart to provide a reliable pacing modality that most closely resembles native conduction with the potential to eliminate delayed myocardial conduction and associated re-entry. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/467102v2_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1577526org.highwire.dtl.DTLVardef@cc510dorg.highwire.dtl.DTLVardef@1dd426eorg.highwire.dtl.DTLVardef@1346aab_HPS_FORMAT_FIGEXP M_FIG C_FIG One Sentence SummaryInjectable hydrogel electrodes achieve pacing that mimics physiologic conduction by capturing midmyocardial tissue

bioengineering↗