Biology subjects

Ramahdita, G.

Publications and source records attributed to Ramahdita, G..

4 recordsLinked to original sources

bioRxiv2025

A Micro-Engineered Heart Tissue Model of Desmin-related Cardiomyopathy Caused by Mutant αB Crystalin

Protein quality control (PQC) is essential for maintaining sarcomere integrity in cardiomyocytes. Crystallin B chain (CRYAB) R120G mutation disrupts CRYABs chaperone activity, leading to aggregation of CRYAB and its client proteins (including Desmin), leading to Desmin-related cardiomyopathy (DRM). Prior experimental systems for modeling DRM linked to CRYAB require massive overexpression of CRYAB mutant isoforms, raising questions about translational relevance. Here, we establish the first model of CRYAB-linked DRM that uses genome-edited hiPSC together with isogenic controls, allowing us to study the impact of mutant CRYAB expressed at near endogenous levels. Within micro-engineered heart tissues (HT), CRYAB-R120G mutant hiPSC-derived cardiomyocytes recapitulated key DRM hallmarks, including Desmin and CRYAB aggregation, contractile dysfunction, and increased vulnerability to PQC pathway inhibition. CRYAB-R120G mutant HT also exhibited dysfunctional calcium-contraction coupling, which exacerbated contractile deficits at higher pacing frequencies. JAK1 inhibition with Itacitinib partially restored contractile function at higher pacing frequencies, suggesting JAK1 inhibition as a viable therapeutic strategy. By preserving human-specific structural and functional features, our {micro}HT platform enables mechanistic characterization of proteotoxic cardiomyopathies and offers a scalable system for targeted drug screening.

bioengineering↗

bioRxiv2025

3D-printing-assisted, microfabricated devices reveal hierarchical and temporal mechanosensing in high-density fibroblast culture

Understanding how cells integrate mechanical forces across multiple directions, length scales, and timescales remains a fundamental challenge in mechanobiology. Deciphering how cells integrate this information is particularly important in the context of wound healing, where the timing and duration of the fibroblast-to-myofibroblast transition can determine healing outcomes. Here, we discovered that fibroblasts in engineered tissues respond to directional anisotropy in stress through a hierarchical temporal cascade, with individual cell elongation (24 hr) preceding collective alignment (40 hr), which then drives -smooth muscle actin expression and myofibroblast transition (96h). To enable this discovery, we developed a modified hydrogel-assisted stereolithographic elastomer (HASTE) prototyping platform to incorporate a detergent that improves wettability of template agar hydrogels by poly(dimethylsiloxane) elastomer. HASTE allowed rapid prototyping of intricate 3D micropost arrays that provides isotropic (8-post) versus anisotropic (4-post) boundary conditions. Fibroblasts sensed and responded to stress directionality before bulk tissue reorganization occurs. Computational modeling predicted steady-state activation patterns based on initial stress anisotropy rather than magnitude, and our experiments reveal that reaching this state requires sequential mechanosensitive processes operating across distinct timescales. This temporal hierarchy persists even when extensive cell-cell contacts might be expected to mask matrix-mediated mechanical signals. Our findings demonstrate that fibroblast mechanosensing involves adaptive responses encoded through progressive cell and tissue reorganization. Results provide insight into how nanoscale mechanosensing scales up to direct tissue-level organization, with implications for understanding wound healing, understanding fibrosis, and engineering functional tissue replacements.

bioengineering↗

bioRxiv2023

Mechanical Resistance to Micro-Heart Tissue Contractility unveils early Structural and Functional Pathology in iPSC Models of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is the most common cause of sudden death in the young. Because the disease exhibits variable penetrance, there are likely nongenetic factors that contribute to the manifestation of the disease phenotype. Clinically, hypertension is a major cause of morbidity and mortality in patients with HCM, suggesting a potential synergistic role for the sarcomeric mutations associated with HCM and mechanical stress on the heart. We developed an in vitro physiological model to investigate how the afterload that the heart muscle works against during contraction acts together with HCM-linked MYBPC3 mutations to trigger a disease phenotype. Micro-heart muscle arrays (HM) were engineered from iPSC-derived cardiomyocytes bearing MYBPC3 loss-of-function mutations and challenged to contract against mechanical resistance with substrates stiffnesses ranging from the of embryonic hearts (0.4 kPa) up to the stiffness of fibrotic adult hearts (114 kPa). Whereas MYBPC3+/- iPSC-cardiomyocytes showed little signs of disease pathology in standard 2D culture, HMs that included components of afterload revealed several hallmarks of HCM, including cellular hypertrophy, impaired contractile energetics, and maladaptive calcium handling. Remarkably, we discovered changes in troponin C and T localization in the MYBPC3+/- HM that were entirely absent in 2D culture. Pharmacologic studies suggested that excessive Ca2+ intake through membrane-embedded channels, rather than sarcoplasmic reticulum Ca2+ ATPase (SERCA) dysfunction or Ca2+ buffering at myofilaments underlie the observed electrophysiological abnormalities. These results illustrate the power of physiologically relevant engineered tissue models to study inherited disease mechanisms with iPSC technology.

bioengineering↗

bioRxiv2022

Hydrogel Assisted Double Molding of 3D-Print Enables Prestress Regulation of Micro-Heart Muscle Physiology

Engineered heart tissues have been created to study cardiac biology and disease in a setting that more closely mimics in-vivo heart muscle than 2D monolayer culture. Previously published studies suggest that geometrically anisotropic micro-environments are crucial for inducing "in vivo-like" physiology from immature cardiomyocytes. We hypothesized that such anisotropic tissue geometries regulate tissue prestress, and that in turn this prestress is a major factor regulating cardiomyocytes electrophysiological development. Thus, we studied the effects of tissue geometry on electrophysiology of micro-heart muscle arrays (HM) engineered from human induced pluripotent stem cells (iPSC). Geometries predicted to increase tissue prestress not only affected cardiomyocyte structure, but also had profound effects on electrophysiology. Elongated geometries led to adaptations that yielded increased calcium intake during each contraction cycle. Strikingly, pharmacologic studies revealed a prestress threshold is required for sodium channel function, whereas L-type calcium and rapidly-rectifying potassium channels were largely insensitive. Analysis of RNA and protein levels suggest sodium channel activity changes were related to post-transcriptional, and potentially post-translational, changes. HM formed from Plakophilin 2 (PKP2) knockout iPSC had a cellular structure similar to isogenic controls. However, these tissues exhibited no functional sodium current and an overall lesser degree of electrical remodeling in response to prestress. These results suggest that PKP2, a key component of the nascent desmosome, is crucial to transducing tissue prestress into physiologically beneficial electrical remodeling via activation of sodium channels.

bioengineering↗