Biology subjects

Rafatian, N.

Publications and source records attributed to Rafatian, N..

5 recordsLinked to original sources

bioRxiv2025

Patient-Specific 3D Heart-On-a-Chip Model of Dilated Cardiomyopathy with Embedded Bead-Based Mapping of Tissue Contractility

Dilated cardiomyopathy (DCM) is the leading cause of heart transplantation, with a 50% risk of progression to heart failure within five years. Conventional disease modeling approaches fail to recapitulate the sophisticated function of the human heart. Alternatively, heart-on-a-chip (HOC) platforms enable real-time monitoring of disease progression and drug responses using miniaturized engineered heart tissues. Here, we developed a functional HOC model using patient-specific human induced pluripotent stem cells (hiPSCs), reprogrammed from the patients blood samples. The chip contains two cell-seeding chambers with flexible silicone pillars to support tissue formation. Healthy and DCM hiPSCs were differentiated into cardiomyocytes, combined with an optimized ratio of human cardiac fibroblasts, encapsulated in a fibrin/Geltrex hydrogel (containing fluorescent beads), and seeded in the device chambers. The tissue gradually compacted and started beating spontaneously. Immunofluorescence assay revealed structural abnormalities in DCM tissues, including reduced cell alignment and elongation. The tissue functional responses (e.g., calcium transients and beating) were investigated after 2 weeks of culture, revealing ventricular tachycardia in DCM tissue and highlighting functional hallmarks of the disease. Finally, the model was validated using a drug with known inotropic and chronotropic effects (i.e., norepinephrine). Our platform demonstrated great potential in drug screening, disease modeling, and personalized medicine.

bioengineering↗

bioRxiv2025

Heart-On-a-Chip with Integrated Ultrasoft Mechanosensors for Continuous Measurement of Cell- and Tissue-scale Contractile Stresses

Heart-on-a-chip platforms aim to miniaturize and replicate the complex structure and function of cardiac tissue. Traditionally, microfabricated pillar pairs have been employed in these systems to provide tissue anchorage and determine contractility parameters based on pillar deflection. However, this approach lacks the spatial resolution required to capture local cell- and tissue-scale mechanical stresses. In this study, we established a non-destructive optical method for continuous micro- and macro-scale contractile force measurements. We utilized our previously developed edge-labeled micro-spherical stress gauges (eMSGs) to map the stresses within a heart-on-a-chip. These ultrasoft mechanosensors visibly deform in response to stresses generated by cells and the extracellular matrix (ECM). The chip consisted of two cell-seeding chambers, each containing flexible silicone pillar pairs to support tissue formation and compaction. Neonatal rat cardiomyocytes (CMs) were encapsulated in a fibrin/Geltrex hydrogel mixture containing eMSGs and seeded into each chamber. Over time, the tissue compacted and began beating spontaneously, demonstrating structural alignment and functional cardiac hallmarks, such as calcium transients and tissue-scale beating. The effects of ECM composition on tissue function were examined, revealing that lower fibrin concentrations significantly enhanced contractile frequency, regularity, and stress generation. Local cell- and ECM-scale mechanics were further investigated by analyzing the shape changes of the dispersible sensors. Lateral and longitudinal stresses were calculated for each sensor, highlighting the critical role of tissue compaction and contraction in cell-generated forces. Finally, the platform was validated using two known drug candidates, with their effects on contractility clearly demonstrated.

bioengineering↗

bioRxiv2024

Biomimetic fractal topography enhances podocyte maturation in vitro

Cells and tissues in their native environment are organized into intricate fractal structures, which are rarely recapitulated in their culture in vitro. The extent to which fractal patterns that resemble complex topography in vivo influence cell maturation, and the cellular responses to such shape stimulation remain inadequately elucidated. Yet, the application of fractal cues (topographical stimulation via self-similar patterns) as an external input may offer a much-needed solution to the challenge of improving the differentiated cell phenotype in vitro. Here, we established fractality in podocytes, branching highly differentiated kidney cells, and glomerulus structure. Biomimetic fractal patterns derived from glomerular histology were used to generate topographical (2.5-D) substrates for cell culture. Podocytes grown on fractal topography were found to express higher levels of functional markers and exhibit enhanced cell polarity. To track morphological complexities of differentiated podocytes, we employed a fluorescent labelling assay where labelled individual cells are tracked within otherwise optically silent confluent cell monolayer to reveal cell-cell interdigitation. RNAseq analysis suggests enhanced ECM deposition and remodeling in podocytes grown on fractal topography compared to flat surface or non-fractal microcurvature, mediated by YAP signaling. The incorporation of fractal topography into standard tissue culture well plates as demonstrated here may serve as a user-friendly bioengineered platform for high-fidelity cell culture.

bioengineering↗

bioRxiv2023

Heart-on-a-chip model of immune-induced cardiac dysfunction reveals the involvement of free mitochondrial DNA and therapeutic effects of endothelial exosomes

Cardiovascular disease continues to take more human lives than all cancer combined, prompting the need for improved research models and treatment options. Despite a significant progress in development of mature heart-on-a-chip models of fibrosis and cardiomyopathies starting from induced pluripotent stem cells (iPSCs), human cell-based models of myocardial inflammation are lacking. Here, we bioengineered a vascularized heart-on-a-chip system with circulating immune cells to model SARS-CoV-2-induced acute myocarditis. Briefly, we observed hallmarks of COVID-19-induced myocardial inflammation in the heart-on-a-chip model, as the presence of immune cells augmented the expression levels of proinflammatory cytokines, triggered progressive impairment of contractile function and altered intracellular calcium transient activities. An elevation of circulating cell-free mitochondrial DNA (ccf-mtDNA) was measured first in the in vitro heart-on-a-chip model and then validated in COVID-19 patients with low left ventricular ejection fraction (LVEF), demonstrating that mitochondrial damage is an important pathophysiological hallmark of inflammation induced cardiac dysfunction. Leveraging this platform in the context of SARS-CoV-2 induced myocardial inflammation, we established that administration of human umbilical vein-derived EVs effectively rescued the contractile deficit, normalized intracellular calcium handling, elevated the contraction force and reduced the ccf- mtDNA and chemokine release via TLR-NF-kB signaling axis.

bioengineering↗

bioRxiv2022

Non-invasive quantification of contractile dynamics in cardiac cells, spheroids and organs-on-a-chip using high frequency ultrasound

Cell-based models that mimic in vivo heart physiology are poised to make significant advances in cardiac disease modeling and drug discovery. In these systems, cardiomyocyte (CM) contractility is an important functional metric, but current measurement methods are inaccurate, low-throughput, or require complex set-ups. To address this need, we developed a standalone non-invasive, label-free ultrasound technique operating at 40-200 MHz to measure the beat rate, beat rhythm, and force of contraction of cardiac models, ranging from single adult CMs to 3D microtissue constructs in standard cell culture formats. The high temporal resolution of 1000 fps resolved the beat profile of single mouse CMs paced at up to 9 Hz, revealing limitations of lower speed optical based measurements to resolve beat kinetics or characterize aberrant beats. Coupling of ultrasound with traction force microscopy enabled the measurement of CM longitudinal modulus and facile estimation of adult mouse CM contractile forces of 2.34 {+/-} 1.40 N, comparable to more complex measurement techniques. Similarly, measurements of beat rate, rhythm, and drug responses of CM spheroid and microtissue models were demonstrated. In conclusion, ultrasound can be used for the rapid characterization of CM contractile function in a wide range of commonly-studied configurations ranging from single cells to 3D tissue constructs using standard well plates, with applications in cardiac drug discovery and cardiotoxicity evaluation.

bioengineering↗