Conductive electrospun polymer improves stem cell-derived cardiomyocyte function and maturation.

Despite numerous efforts to generate mature human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), cells often remain immature, electrically isolated, and may not reflect adult biology. Conductive polymers are attractive candidates to facilitate electrical communication between hPSC-CMs, especially at sub-confluent cell densities or diseased cells lacking cell-cell junctions. Here we electrospun conductive polymers to create a conductive fiber mesh and assess if electrical signal propagation is improved in hPSC-CMs seeded on the mesh network. Matrix characterization indicated fiber structure remained stable over weeks in buffer, scaffold stiffness remained near in vivo cardiac stiffness, and electrical conductivity scaled with conductive polymer concentration. Cells remained adherent and viable on the scaffolds for at least 5 days. Transcriptomic profiling of hPSC-CMs cultured on conductive substrates for 3 days showed upregulation of cardiac and muscle-related genes versus non-conductive fibers. Structural proteins were more organized and calcium handling was improved on conductive substrates, even at sub-confluent cell densities; prolonged culture on conductive scaffolds improved membrane depolarization compared to non-conductive substrates. Taken together, these data suggest that blended, conductive scaffolds are stable, supportive of electrical coupling in hPSC-CMs, and promote maturation, which may improve our ability to model cardiac diseases and develop targeted therapies.

High shear stress enhances endothelial permeability in the presence of the risk haplotype at 9p21.3.

Single nucleotide polymorphisms (SNPs) are exceedingly common in non-coding loci, and while they are significantly associated with a myriad of diseases, their specific impact on cellular dysfunction remains unclear. Here, we show that when exposed to external stressors, the presence of risk SNPs in the 9p21.3 coronary artery disease (CAD) risk locus increases endothelial monolayer and microvessel dysfunction. Endothelial cells (ECs) derived from induced pluripotent stem cells of patients carrying the risk haplotype (R/R WT) differentiated similarly to their non-risk and isogenic knockout (R/R KO) counterparts. Monolayers exhibited greater permeability and reactive oxygen species signaling when the risk haplotype was present. Addition of the inflammatory cytokine TNFα further enhanced EC monolayer permeability but independent of risk haplotype; TNFα also did not substantially alter haplotype transcriptomes. Conversely, when wall shear stress was applied to ECs in a microfluidic vessel, R/R WT vessels were more permeable at lower shear stresses than R/R KO vessels. Transcriptomes of sheared cells clustered more by risk haplotype than by patient or clone, resulting in significant differential regulation of EC adhesion and extracellular matrix genes vs static conditions. A subset of previously identified CAD risk genes invert expression patterns in the presence of high shear concomitant with altered cell adhesion genes, vessel permeability, and endothelial erosion in the presence of the risk haplotype, suggesting that shear stress could be a regulator of non-coding loci with a key impact on CAD.