Browsing by Author "Nain, Amrinder S."

Now showing 1 - 14 of 14
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    Aligned fibers direct collective cell migration to engineer closing and nonclosing wound gaps
    Sharma, Puja; Ng, Colin; Jana, Aniket; Padhi, Abinash; Szymanski, Paige; Lee, Jerry S. H.; Behkam, Bahareh; Nain, Amrinder S. (2017-09-15)
    Cell emergence onto damaged or organized fibrous extracellular matrix (ECM) is a crucial precursor to collective cell migration in wound closure and cancer metastasis, respectively. However, there is a fundamental gap in our quantitative understanding of the role of local ECM size and arrangement in cell emergence-based migration and local gap closure. Here, using ECM-mimicking nanofibers bridging cell monolayers, we describe a method to recapitulate and quantitatively describe these in vivo behaviors over multispatial (single cell to cell sheets) and temporal (minutes to weeks) scales. On fiber arrays with large interfiber spacing, cells emerge (invade) either singularly by breaking cell-cell junctions analogous to release of a stretched rubber band (recoil), or in groups of few cells (chains), whereas on closely spaced fibers, multiple chains emerge collectively. Advancing cells on fibers form cell streams, which support suspended cell sheets (SCS) of various sizes and curvatures. SCS converge to form local gaps that close based on both the gap size and shape. We document that cell stream spacing of 375 mu m and larger hinders SCS advancement, thus providing abilities to engineer closing and nonclosing gaps. Altogether we highlight the importance of studying cell-fiber interactions and matrix structural remodeling in fundamental and translational cell biology.
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    Aligned nanofiber topography directs the tenogenic differentiation of mesenchymal stem cells
    Popielarczyk, Tracee L.; Nain, Amrinder S.; Barrett, Jennifer G. (MDPI, 2017-01-06)
    Tendon is commonly injured, heals slowly and poorly, and often suffers re-injury after healing. This is due to failure of tenocytes to effectively remodel tendon after injury to recapitulate normal architecture, resulting in poor mechanical properties. One strategy for improving the outcome is to use nanofiber scaffolds and mesenchymal stem cells (MSCs) to regenerate tendon. Various scaffold parameters are known to influence tenogenesis. We designed suspended and aligned nanofiber scaffolds with the hypothesis that this would promote tenogenesis when seeded with MSCs. Our aligned nanofibers were manufactured using the previously reported non-electrospinning Spinneret-based Tunable Engineered Parameters (STEP) technique. We compared parallel versus perpendicular nanofiber scaffolds with traditional flat monolayers and used cellular morphology, tendon marker gene expression, and collagen and glycosaminoglycan deposition as determinants for tendon differentiation. We report that compared with traditional control monolayers, MSCs grown on nanofibers were morphologically elongated with higher gene expression of tendon marker scleraxis and collagen type I, along with increased production of extracellular matrix components collagen (p = 0.0293) and glycosaminoglycan (p = 0.0038). Further study of MSCs in different topographical environments is needed to elucidate the complex molecular mechanisms involved in stem cell differentiation.
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    Cancer Cells Sense Fibers by Coiling on them in a Curvature-Dependent Manner
    Mukherjee, Apratim; Behkam, Bahareh; Nain, Amrinder S. (2019-09-27)
    Metastatic cancer cells sense the complex and heterogeneous fibrous extracellular matrix (ECM) by formation of protrusions, and our knowledge of how cells physically recognize these fibers remains in its infancy. Here, using suspended ECM-mimicking isodiameter fibers ranging from 135 to 1,000 nm, we show that metastatic breast cancer cells sense fiber diameters differentially by coiling (wrapping-around) on them in a curvature-dependent manner, whereas non-tumorigenic cells exhibit diminished coiling. We report that coiling occurs at the tip of growing protrusions and the coil width and coiling rate increase in a curvature-dependent manner, but time to maximum coil width occurs biphasically. Interestingly, bundles of 135-nm diameter fibers recover coiling width and rate on 1,000-nm-diameter fibers. Coiling also coincides with curvature-dependent persistent and ballistic transport of endogenous granules inside the protrusions. Altogether, our results lay the groundwork to link biophysical sensing with biological signaling to quantitate pro- and anti-invasive fibrous environments.
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    Controlling Microbial Adhesion to the Surfaces Using Topographical Cues
    Kargar, Mehdi (Virginia Tech, 2013-05-08)
    The state of adhesion of bacteria to nanofiber-textured model surfaces is analyzed at single-cell level. The results reveal similarities between the effect of topography on bacteria-surface interactions and vesicle-surface interactions. The results are discussed in the context of controlling bacterial adhesion to surfaces using nanofibrous topographical features.
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    Experimental and theoretical model for the origin of coiling of cellular protrusions around fibers
    Sadhu, Raj Kumar; Hernandez-Padilla, Christian; Eisenbach, Samo Penič; Zhang, Lixia; Vishwasrao, Harshad D.; Behkam, Bahareh; Konstantopoulos, Konstantinos; Shroff, Hari; Iglič, Aleš; Peles, Elior; Nain, Amrinder S.; Gov, Nir S. (Nature Research, 2023-09-12)
    Protrusions at the leading-edge of a cell play an important role in sensing the extracellular cues during cellular spreading and motility. Recent studies provided indications that these protrusions wrap (coil) around the extracellular fibers. However, the physics of this coiling process, and the mechanisms that drive it, are not well understood. We present a combined theoretical and experimental study of the coiling of cellular protrusions on fibers of different geometry. Our theoretical model describes membrane protrusions that are produced by curved membrane proteins that recruit the protrusive forces of actin polymerization, and identifies the role of bending and adhesion energies in orienting the leading-edges of the protrusions along the azimuthal (coiling) direction. Our model predicts that the cell’s leading-edge coils on fibers with circular cross-section (above some critical radius), but the coiling ceases for flattened fibers of highly elliptical cross-section. These predictions are verified by 3D visualization and quantitation of coiling on suspended fibers using Dual- View light-sheet microscopy (diSPIM). Overall, we provide a theoretical framework, supported by experiments, which explains the physical origin of the coiling phenomenon.
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    Force-exerting perpendicular lateral protrusions in fibroblastic cell contraction
    Padhi, Abinash; Singh, Karanpreet; Franco-Barraza, Janusz; Marston, Daniel J.; Cukierman, Edna; Hahn, Klaus M.; Kapania, Rakesh K.; Nain, Amrinder S. (2020-07-21)
    Aligned extracellular matrix fibers enable fibroblasts to undergo myofibroblastic activation and achieve elongated shapes. Activated fibroblasts are able to contract, perpetuating the alignment of these fibers. This poorly understood feedback process is critical in chronic fibrosis conditions, including cancer. Here, using fiber networks that serve as force sensors, we identify "3D perpendicular lateral protrusions" (3D-PLPs) that evolve from lateral cell extensions named twines. Twines originate from stratification of cyclic-actin waves traversing the cell and swing freely in 3D to engage neighboring fibers. Once engaged, a lamellum forms and extends multiple secondary twines, which fill in to form a sheet-like PLP, in a force-entailing process that transitions focal adhesions to activated (i.e., pathological) 3D-adhesions. The specific morphology of PLPs enables cells to increase contractility and force on parallel fibers. Controlling geometry of extracellular networks confirms that anisotropic fibrous environments support 3D-PLP formation and function, suggesting an explanation for cancer-associated desmoplastic expansion. Padhi et al. employ nanofibers with controlled structure and alignment as an extra-cellular matrix model, on which they study the exertion of forces from adherent fibroblasts. Identifying force exerting 3D perpendicular lateral protrusions, authors describe a mechanism which leads to the contraction of parallel, neighbouring fibers, and the forces needed to move and align the neighbouring fibers. These findings have relevance in understanding cancer-associated desmoplastic expansion.
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    The Mechanistic Influence of Aligned Nanofiber Networks on Cell Shape, Migration and Blebbing Dynamics of Glioma Cells
    Sharma, Puja; Sheets, Kevin; Elankumaran, Subbiah; Nain, Amrinder S. (The Royal Society of Chemistry, 2013-06-03)
    Investigating the mechanistic influence of the tumor microenvironment on cancer cell migration and membrane blebbing is crucial in the understanding and eventual arrest of cancer metastasis. In this study, we investigate the effect of suspended and aligned nanofibers on the glioma cytoskeleton, cell shape, migration and plasma membrane blebbing dynamics using a non-electrospinning fiber-manufacturing platform. Cells attached in repeatable shapes of spindle on single fibers, rectangular on two parallel fibers and polygonal on intersecting fibers. Structural stiffness (N m_1) of aligned and suspended nanofibers (average diameter: 400 nm, length: 4, 6, and 10 mm) was found to significantly alter the migration speed with higher migration on lower stiffness fibers. For cells attached to fibers and exhibiting blebbing, an increase in cellular spread area resulted in both reduced bleb count and bleb size with an overall increase in cell migration speed. Blebs no longer appeared past a critical cellular spread area of approximately 1400 _m2. Our results highlighting the influence of the mechanistic environment on the invasion dynamics of glioma cells add to the understanding of how biophysical components influence glioma cell migration and blebbing dynamics.
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    Mitotic outcomes and errors in fibrous environments
    Jana, Aniket; Sarkar, Apurba; Zhang, Haonan; Agashe, Atharva; Wang, Ji; Paul, Raja; Gov, Nir S.; DeLuca, Jennifer G.; Nain, Amrinder S. (National Academy of Sciences, 2023-02-27)
    During mitosis, cells round up and utilize the interphase adhesion sites within the fibrous extracellular matrix (ECM) as guidance cues to orient the mitotic spindles. Here, using suspended ECM-mimicking nanofiber networks, we explore mitotic outcomes and error distribution for various interphase cell shapes. Elongated cells attached to single fibers through two focal adhesion clusters (FACs) at their extremities result in perfect spherical mitotic cell bodies that undergo significant 3-dimensional (3D) displacement while being held by retraction fibers (RFs). Increasing the number of parallel fibers increases FACs and retraction fiber-driven stability, leading to reduced 3D cell body movement, metaphase plate rotations, increased interkinetochore distances, and significantly faster division times. Interestingly, interphase kite shapes on a crosshatch pattern of four fibers undergo mitosis resembling single-fiber outcomes due to rounded bodies being primarily held in position by RFs from two perpendicular suspended fibers. We develop a cortex–astral microtubule analytical model to capture the retraction fiber dependence of the metaphase plate rotations. We observe that reduced orientational stability, on single fibers, results in increased monopolar mitotic defects, while multipolar defects become dominant as the number of adhered fibers increases. We use a stochastic Monte Carlo simulation of centrosome, chromosome, and membrane interactions to explain the relationship between the observed propensity of monopolar and multipolar defects and the geometry of RFs. Overall, we establish that while bipolar mitosis is robust in fibrous environments, the nature of division errors in fibrous microenvironments is governed by interphase cell shapes and adhesion geometries.
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    Nanonet force microscopy for measuring forces in single smooth muscle cells of the human aorta
    Hall, Alexander; Chan, Patrick; Sheets, Kevin; Apperson, Matthew; Delaughter, Christopher; Gleason, Thomas G.; Phillippi, Julie A.; Nain, Amrinder S. (2017-07-07)
    A number of innovative methods exist to measure cell-matrix adhesive forces, but they have yet to accurately describe and quantify the intricate interplay of a cell and its fibrous extracellular matrix (ECM). In cardiovascular pathologies, such as aortic aneurysm, new knowledge on the involvement of cell-matrix forces could lead to elucidation of disease mechanisms. To better understand this dynamics, we measured primary human aortic single smooth muscle cell (SMC) forces using nanonet force microscopy in both inside-out (I-O intrinsic contractility) and outside-in (O-I external perturbation) modes. For SMC populations, we measured the I-O and O-I forces to be 12.9 +/- 1.0 and 57.9 +/- 2.5 nN, respectively. Exposure of cells to oxidative stress conditions caused a force decrease of 57 and 48% in I-O and O-I modes, respectively, and an increase in migration rate by 2.5-fold. Finally, in O-I mode, we cyclically perturbed cells at constant strain of varying duration to simulate in vivo conditions of the cardiac cycle and found that I-O forces decrease with increasing duration and O-I forces decreased by half at shorter cycle times. Thus our findings highlight the need to study forces exerted and felt by cells simultaneously to comprehensively understand force modulation in cardiovascular disease.
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    Quantitative Biophysical Metrics for Rapid Evaluation of Ovarian Cancer Metastatic Potential
    Mukherjee, Apratim; Zhang, Haonan; Ladner, Katherine; Brown, Megan; Urbanski, Jacob; Grieco, Joseph P.; Kapania, Rakesh K.; Lou, Emil; Behkam, Bahareh; Schmelz, Eva M.; Nain, Amrinder S. (American Society for Cell Biology, 2022-05-15)
    Ovarian cancer is routinely diagnosed long after the disease has metastasized through the fibrous sub-mesothelium. Despite extensive research in the field linking ovarian cancer progression to increasingly poor prognosis, there are currently no validated cellular markers or hallmarks of ovarian cancer that can predict metastatic potential. To discern disease progression across a syngeneic mouse ovarian cancer progression model, here, we fabricated extracellular-matrix mimicking suspended fiber networks: crosshatches of mismatch diameters for studying protrusion dynamics, aligned same diameter networks of varying inter-fiber spacing for studying migration, and aligned nanonets for measuring cell forces. We found that migration correlated with disease, while force-disease biphasic relationship exhibited f-actin stress-fiber network dependence. However, unique to suspended fibers, coiling occurring at tips of protrusions and not the length or breadth of protrusions displayed strongest correlation with metastatic potential. To confirm that our findings were more broadly applicable beyond the mouse model, we repeated our studies in human ovarian cancer cell lines and found that the biophysical trends were consistent with our mouse model results. Altogether, we report complementary high throughput and high content biophysical metrics capable of identifying ovarian cancer metastatic potential on time scale of hours.
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    Sculpting Rupture-Free Nuclear Shapes in Fibrous Environments
    Aniket, Jana; Tran, Avery; Gill, Amritpal; Kiepas, Alexander; Kapania, Rakesh K.; Konstantopoulos, Konstantinos; Nain, Amrinder S. (Wiley, 2022)
    Cytoskeleton-mediated force transmission regulates nucleus morphology. How nuclei shaping occurs in fibrous in vivo environments remains poorly understood. Here suspended nanofiber networks of precisely tunable (nm–μm) diameters are used to quantify nucleus plasticity in fibrous environments mimicking the natural extracellular matrix. Contrary to the apical cap over the nucleus in cells on 2-dimensional surfaces, the cytoskeleton of cells on fibers displays a uniform actin network caging the nucleus. The role of contractility-driven caging in sculpting nuclear shapes is investigated as cells spread on aligned single fibers, doublets, and multiple fibers of varying diameters. Cell contractility increases with fiber diameter due to increased focal adhesion clustering and density of actin stress fibers, which correlates with increased mechanosensitive transcription factor Yes-associated protein (YAP) translocation to the nucleus. Unexpectedly, large- and small-diameter fiber combinations lead to teardrop-shaped nuclei due to stress fiber anisotropy across the cell. As cells spread on fibers, diameter-dependent nuclear envelope invaginations that run the nucleus’s length are formed at fiber contact sites. The sharpest invaginations enriched with heterochromatin clustering and sites of DNA repair are insufficient to trigger nucleus rupture. Overall, the authors quantitate the previously unknown sculpting and adaptability of nuclei to fibrous environments with pathophysiological implications.
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    Spun-wrapped aligned nanofiber (SWAN) lithography for fabrication of micro/nano-structures on 3D objects
    Ye, Zhou; Nain, Amrinder S.; Behkam, Bahareh (Royal Society of Chemistry, 2016-06-01)
    Fabrication of micro/nano-structures on irregularly shaped substrates and three-dimensional (3D) objects is of significant interest in diverse technological fields. However, it remains a formidable challenge thwarted by limited adaptability of the state-of-the-art nanolithography techniques for nanofabrication on non-planar surfaces. In this work, we introduce Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and cost-effective technique for fabrication of multiscale (nano to microscale) structures on 3D objects without restriction on substrate material and geometry. SWAN lithography combines precise deposition of polymeric nanofiber masks, in aligned single or multilayer configurations, with well-controlled solvent vapor treatment and etching processes to enable high throughput (>10−7 m2 s−1) and large-area fabrication of sub-50 nm to several micron features with high pattern fidelity. Using this technique, we demonstrate whole-surface nanopatterning of bulk and thin film surfaces of cubes, cylinders, and hyperbola-shaped objects that would be difficult, if not impossible to achieve with existing methods. We demonstrate that the fabricated feature size (b) scales with the fiber mask diameter (D) as b1.5 ∝ D. This scaling law is in excellent agreement with theoretical predictions using the Johnson, Kendall, and Roberts (JKR) contact theory, thus providing a rational design framework for fabrication of systems and devices that require precisely designed multiscale features.
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    Suspended Micro/Nanofiber Hierarchical Scaffolds for Studying Cell Mechanobiology
    Wang, Ji (Virginia Tech, 2015-02-11)
    Extracellular matrix (ECM) is a fibrous natural cell environment, possessing complicated micro-and nano- architectures, which provides signaling cues and influences cell behavior. Mimicking this three dimensional environment in vitro is a challenge in developmental and disease biology. Here, suspended multilayer hierarchical nanofiber assemblies fabricated using the non-electrospinning STEP (Spinneret based Tunable Engineered Parameter) fiber manufacturing technique with controlled fiber diameter (microns to less than 100 nm), orientation and spacing in single and multiple layers are demonstrated as biological scaffolds. Hierarchical nanofiber assemblies were developed to control single cell shape (shape index from 0.15 to 0.57), nuclei shape (shape index 0.75 to 0.99) and focal adhesion cluster length (8-15 micrometer). To further investigate single cell-ECM biophysical interactions, nanofiber nets fused in crisscross patterns were manufactured to measure the "inside out" contractile forces of single mesenchymal stem cells (MSCs). The contractile forces (18-320 nano Newton) were found to scale with fiber structural stiffness (2 -100 nano Newton/micrometer). Cells were observed to shed debris on fibers, which were found to exert forces (15-20 nano Newton). Upon CO? deprivation, cells were observed to monotonically reduce cell spread area and contractile forces. During the apoptotic process, cells exerted both expansive and contractile forces. The platform developed in this study allows a wide parametric investigation of biophysical cues which influence cell behaviors with implications in tissue engineering, developmental biology, and disease biology.
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    Tunneling Nanotubes between Cells Migrating in ECM Mimicking Fibrous Environments
    Jana, Aniket; Ladner, Katherine; Lou, Emil; Nain, Amrinder S. (MDPI, 2022-04-14)
    Tunneling nanotubes (TNTs) comprise a unique class of actin-rich nanoscale membranous protrusions. They enable long-distance intercellular communication and may play an integral role in tumor formation, progression, and drug resistance. TNTs are three-dimensional, but nearly all studies have investigated them using two-dimensional cell culture models. Here, we applied a unique 3D culture platform consisting of crosshatched and aligned fibers to fabricate synthetic suspended scaffolds that mimic the native fibrillar architecture of tumoral extracellular matrix (ECM) to characterize TNT formation and function in its native state. TNTs are upregulated in malignant mesothelioma; we used this model to analyze the biophysical properties of TNTs in this 3D setting, including cell migration in relation to TNT dynamics, rate of TNT-mediated intercellular transport of cargo, and conformation of TNT-forming cells. We found that highly migratory elongated cells on aligned fibers formed significantly longer but fewer TNTs than uniformly spread cells on crossing fibers. We developed new quantitative metrics for the classification of TNT morphologies based on shape and cytoskeletal content using confocal microscopy. In sum, our strategy for culturing cells in ECM-mimicking bioengineered scaffolds provides a new approach for accurate biophysical and biologic assessment of TNT formation and structure in native fibrous microenvironments.