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1. Microenvironmental determinants of organized iPSC-cardiomyocyte tissues on synthetic fibrous matrices

   https://doi.org/10.1039/D0BM01247E  

   DePalma, Samuel J.; Davidson, Christopher D.; Stis, Austin E.; Helms, Adam S.; Baker, Brendon M. (January 2021, Biomaterials Science)

   null (Ed.)

   Cardiomyocytes derived from induced pluripotent stem cells (iPSC-CMs) show great potential for engineering myocardium to study cardiac disease and create regenerative therapies. However, iPSC-CMs typically possess a late embryonic stage phenotype, with cells failing to exhibit markers of mature adult tissue. This is due in part to insufficient knowledge and control of microenvironmental cues required to facilitate the organization and maturation of iPSC-CMs. Here, we employed a cell-adhesive, mechanically tunable synthetic fibrous extracellular matrix (ECM) consisting of electrospun dextran vinyl sulfone (DVS) fibers and examined how biochemical, architectural, and mechanical properties of the ECM impact iPSC-CM tissue assembly and subsequent function. Exploring a multidimensional parameter space spanning cell-adhesive ligand, seeding density, fiber alignment, and stiffness, we found that fibronectin-functionalized DVS matrices composed of highly aligned fibers with low stiffness optimally promoted the organization of functional iPSC-CM tissues. Tissues generated on these matrices demonstrated improved calcium handling and increased end-to-end localization of N-cadherin as compared to micropatterned fibronectin lines or fibronectin-coated glass. Furthermore, DVS matrices supported long-term culture (45 days) of iPSC-CMs; N-cadherin end-to-end localization and connexin43 expression both increased as a function of time in culture. In sum, these findings demonstrate the importance of recapitulating the fibrous myocardial ECM in engineering structurally organized and functional iPSC-CM tissues. 

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2. A Study of Gene Expression, Structure, and Contractility of iPSC-Derived Cardiac Myocytes from a Family with Heart Disease due to LMNA Mutation

   https://doi.org/10.1007/s10439-021-02850-8  

   Mehrabi, Mehrsa; Morris, Tessa A.; Cang, Zixuan; Nguyen, Cecilia H.; Sha, Yutong; Asad, Mira N.; Khachikyan, Nyree; Greene, Taylor L.; Becker, Danielle M.; Nie, Qing; et al (December 2021, Annals of Biomedical Engineering)

   Abstract Genetic mutations to the Lamin A/C gene ( LMNA ) can cause heart disease, but the mechanisms making cardiac tissues uniquely vulnerable to the mutations remain largely unknown. Further, patients with LMNA mutations have highly variable presentation of heart disease progression and type. In vitro patient-specific experiments could provide a powerful platform for studying this phenomenon, but the use of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) introduces heterogeneity in maturity and function thus complicating the interpretation of the results of any single experiment. We hypothesized that integrating single cell RNA sequencing (scRNA-seq) with analysis of the tissue architecture and contractile function would elucidate some of the probable mechanisms. To test this, we investigated five iPSC-CM lines, three controls and two patients with a (c.357-2A>G) mutation. The patient iPSC-CM tissues had significantly weaker stress generation potential than control iPSC-CM tissues demonstrating the viability of our in vitro approach. Through scRNA-seq, differentially expressed genes between control and patient lines were identified. Some of these genes, linked to quantitative structural and functional changes, were cardiac specific, explaining the targeted nature of the disease progression seen in patients. The results of this work demonstrate the utility of combining in vitro tools in exploring heart disease mechanics. 

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3. Deep learning reveals how cells pull, buckle, and navigate fibrous environments

   https://doi.org/10.1073/pnas.2424047122  

   Padhi, Abinash; Daw, Arka; Agashe, Atharva; Sawhney, Medha; Talukder, Maahi M; Pour, Mehran_M H; Jafari, Mohammad; Genin, Guy M; Alisafaei, Farid; Kale, Sohan; et al (November 2025, Proceedings of the National Academy of Sciences)

   Cells in tissues navigate fibrous environments fundamentally differently than they do on flat substrates, but the establishment of cell forces in physiological fibrous settings remains poorly understood. Although factors such as the stiffness of the extracellular matrix (ECM) are known to drive behaviors, including cell motility on flat nonfibrous substrates, the interplay between fiber architecture and stiffness in fibrous ECM is not known. Here, we find that in fibrous environments, the directionality of mechanical forces overrides ECM stiffness as the primary regulator of contractility in migrating cells. Using an approach combining phase microscopy with deep learning to map forces in real time, termed deep learning-enabled live-cell fiber-force microscopy (DLFM), we reveal that when cells transition between anisotropic and isotropic stress fields, their contractility significantly drops despite encountering stiffer ECM, contrary to the behavior of cells on flat nonfibrous substrates. Unlike the peripheral adhesions observed on flat nonfibrous substrates, cells in fibrous matrices form force-generating adhesions throughout their body, stabilized by out-of-plane mechanical components unique to fiber geometry. Cells exhibit distinct force signatures during migration, division, and differentiation, with temporal signatures that predict stem cell fate. These findings, enabled by combining deep learning and the mechanics of cells and fibers, explain long-standing paradoxical behavior of cells navigating deformable fibrous environments, how they can pull and tug at them, and identify tension anisotropy as a master regulator of cell behavior, with implications for cancer invasion, tissue engineering, and regenerative medicine. 

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4. Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation

   https://doi.org/10.1073/pnas.2322762122  

   Hong, Yuan; Peng, Xiangjun; Yu, Haomin; Jafari, Mohammad; Shakiba, Delaram; Huang, Yuxuan; Qu, Chengqing; Melika, Ermia E; Tawadros, Andrew K; Mujahid, Aliza; et al (March 2025, Proceedings of the National Academy of Sciences)

   Mechanical stretch can activate long-lived changes in fibroblasts, increasing their contractility and initiating phenotypic transformations. This activation, critical to wound healing and procedures such as skin grafting, increases with mechanical stimulus for cells cultured in two-dimensional but is highly variable in cells in three-dimensional (3D) tissue. Here, we show that static mechanical stretch of cells in 3D tissues can either increase or decrease fibroblast activation depending upon recursive cell–extracellular matrix (ECM) feedback and demonstrate control of this activation through integrated in vitro and mathematical models. ECM viscoelasticity, signaling dynamics, and cell mechanics combine to yield a predictable, but nonmonotonic, relationship between mechanical stretch and long-term cell activation. Results demonstrate that feedback between cells and ECM determine how cells retain memory of mechanical stretch and have direct implications for improving outcomes in skin grafting procedures. 

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5. Mechanical cues guide the formation and patterning of 3D spheroids in fibrous environments

   https://doi.org/10.1093/pnasnexus/pgaf263  

   Sharma, Sharan; Agashe, Atharva; Hill, Jennifer C; Ganguly, Keya; Sharma, Puja; Richards, Tara D; Huang, Weijian; Kaczorowski, David J; Sanchez, Pablo G; Kapania, Rakesh; et al (August 2025, PNAS Nexus)

   Amon, Cristina (Ed.)

   Abstract Multicellular spheroids have shown great promise in 3D biology. Many techniques exist to form spheroids, but how cells take mechanical advantage of native fibrous extracellular matrix (ECM) to form spheroids remains unknown. Here, we identify the role of fiber diameter, architecture, and cell contractility on spheroids’ spontaneous formation and growth in ECM-mimicking fiber networks. We show that matrix deformability revealed through force measurements on aligned fiber networks promotes spheroid formation independent of fiber diameter. At the same time, larger-diameter crosshatched networks of low deformability abrogate spheroid formation. Thus, designing fiber networks of varying diameters and architectures allows spatial patterning of spheroids and monolayers simultaneously. Forces quantified during spheroid formation revealed the contractile role of Rho-associated protein kinase in spheroid formation and maintenance. Interestingly, we observed spheroid–spheroid and multiple spheroid mergers initiated by cell exchanges to form cellular bridges connecting the two spheroids. Unexpectedly, we found large pericyte spheroids contract rhythmically. Transcriptomic analysis revealed striking changes in cell–cell, cell–matrix, and mechanosensing gene expression profiles concordant with spheroid assembly on fiber networks. Overall, we ascertained that contractility and network deformability work together to spontaneously form and pattern 3D spheroids, potentially connecting in vivo matrix biology with developmental, disease, and regenerative biology. 

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