Biology subjects

Momtahan, N.

Publications and source records attributed to Momtahan, N..

3 recordsLinked to original sources

bioRxiv2025

Dynamic Stiffening to Improve Vasculogenesis of hiPSC-Derived Endothelial Progenitors

Multiple groups have reported on the impact of hydrogel stiffness on vascular network formation in vitro, with overall findings indicating that less stiff hydrogels better support vasculogenesis. However, the majority of this research utilized hydrogels with static stiffness, even though vasculogenesis occurs in tandem with changes in extracellular matrix material properties. To that end, we hypothesize that dynamic modulation of hydrogel stiffness during the process of vasculogenesis, recapitulating changes observed during embryonic development, would improve vascular network formation. Using our Collagen I/Norbornene-modified hyaluronic acid hydrogel system, we swelled in additional crosslinker and photoinitiator and exposed the hydrogel to UV light, enabling hydrogel stiffening at user-defined time points with no significant effect on cell viability. We observed that in situ stiffening at early time points, prior to the onset of significant cell migration, resulted in more robust vascular network formation relative to unstiffened controls, while stiffening at later time points disrupted existing vascular networks. These trends continued in in vivo experiments in nude mice, with cell-laden hydrogels stiffened at early time points resulting in improved blood flow, while those stiffened at later time points had the opposite effect. We hypothesized that this was due to differential impacts of focal adhesion kinase (FAK) activation following in situ stiffening, as supplementation with a Rho kinase inhibitor, downstream of FAK, partially reversed the effects of in situ stiffening. Taken together, this research demonstrates the benefits of incorporating dynamic cues into hydrogel design to create more physiologically relevant vasculature.

bioengineering↗

bioRxiv2025

Modulating Hydrogel Stiffness Through Light-Based 3D Printing to Mimic Cardiac Fibrosis and Cardiomyocyte Dysfunction Using hiPSC-Derived Cells

The human hearts limited regenerative capacity is a significant barrier to addressing cardiovascular disease (CVD). This is particularly true for cardiac fibrosis, a form of CVD wherein the wound healing process has gone awry. In cardiac fibrosis, excessive scar tissue formation due to dysregulated remodeling of the hearts extracellular matrix (ECM) results in increased stiffness that reduces cardiac output and can lead to heart failure. This dysregulated ECM deposition is driven by activated cardiac fibroblasts, where cell substrate stiffness is known to play a role in cardiac fibroblast activation. New preclinical models that accurately recapitulate the behavior of activated cardiac fibroblasts are needed to better understand and treat cardiac fibrosis. To this end, we describe a model wherein human induced pluripotent stem cell (hiPSC)-derived cardiac fibroblasts (HCFs) are cultured on 3D printed hydrogels of tunable stiffness, fabricated using dosage controlled digital light processing (DLP). We demonstrate that our model can induce HCF activation in the absence of TGF{beta}, a key mediator of fibroblast activation, surpassing the activation levels seen with HCFs activated with TGF{beta} on protein-coated tissue culture plates. Furthermore, combining stiffer hydrogels with TGF{beta} recapitulates fibroblast activation similar to what is observed in native cardiac tissue. Lastly, by indirectly coculturing HCFs seeded and activated on these stiff hydrogels with hiPSC-derived cardiomyocytes, we demonstrate that the activated HCFs in our cardiac fibrosis model can impair cardiomyocyte function, mimicking the deleterious effects of cardiac fibrosis.

bioengineering↗

bioRxiv2025

Optimizing cardiac organoid culture to enhance maturation, viability, and cardiotoxicity assessments

Development of relevant, human induced pluripotent stem cell-derived cardiac organoids is essential to recapitulate myocardium physiology and functionality for assessment of drug-induced toxicity evaluations. However, the optimal conditions for culturing self-aggregating multicellular cardiac organoids are not well-elucidated, particularly the impact of noncardiomyocytes. In this study, we generated cardiac organoids at varying seeding densities to formulate organoids that meet or exceed the biological diffusion limit. We assessed their morphology, gene expression profiles, beating functionality, viability, and mitochondrial activity over time. Our results show that organoid sizes stabilize by seven days of culture, regardless of seeding density. However, organoids seeded with 20,000 cells retained an optimal cardiac signature that promotes cardiac maturity and minimizes fibrotic tendencies, especially when culturing longer than seven days. While all organoid populations maintained their beating functionalities, those seeded with 80,000 cells exhibited greater cell shedding and increased apoptosis at long term culture. In contrast, minimal apoptosis was observed in organoids seeded with 20,000 cells after seven days. Mitochondrial staining further revealed that organoids seeded with 20,000 cells consistently demonstrated higher metabolic activity. Taken together, organoids seeded with 20,000 cells and cultured for seven days yielded the healthiest morphology, transcriptional signature, and viability, while maintaining robust beating kinetics. Importantly, compared to 2D cultures, these optimized organoids demonstrate improved sensitivity to clinically relevant doxorubicin-induced cardiotoxicity, enabling more accurate dose-response evaluations that better reflect therapeutic conditions. Impact StatementThis work highlights key tissue engineering considerations for generating self-assembling cardiac organoids suitable for scalable, high-throughput drug screening and discovery. Understanding the effect of seeding density and culture duration on organoid size and, consequently on gene expression, beating functionalities, apoptosis, and metabolic activity, has broader implications for establishing optimal organoid culture conditions. These insights enable the production of large quantities of cardiac organoids capable of modeling drug-induced toxicity effects on a clinically relevant timescale.

bioengineering↗