Biology subjects

Galie, P. A.

Publications and source records attributed to Galie, P. A..

4 recordsLinked to original sources

bioRxiv2025

Tissue-dependent mechanosensing by cells derived from human tumors

Alterations of the extracellular matrix (ECM), including both mechanical (such as stiffening of the ECM) and chemical (such as variation of adhesion proteins and deposition of hyaluronic acid (HA)) changes, in malignant tissues have been shown to mediate tumor progression. To survey how cells from different tissue types respond to various changes in ECM mechanics and composition, we measured physical characteristics (adherent area, shape, cell stiffness, and cell speed) of 25 cancer and 5 non-tumorigenic cell lines on 7 different substrate conditions. Our results indicate substantial heterogeneity in how cell mechanics changes within and across tissue types in response to mechanosensitive and chemosensitive changes in ECM. The analysis also underscores the role of HA in ECM with some cell lines showing changes in cell mechanics in response to presence of HA in soft substrate that are similar to those observed on stiff substrate. This pan-cancer investigation also highlights the importance of tissue-type and cell line specificity for inferences made based on comparison between physical properties of cancer and normal cells. Lastly, using unsupervised machine learning, we identify phenotypic classes that characterize the physical plasticity, i.e. the distribution of physical feature values attainable, of a particular cell type in response to different ECM-based conditions.

biophysics↗

bioRxiv2020

The SARSCoV2 spike protein alters barrier function in 2D static and 3D microfluidic in vitro models of the human blood-brain barrier

As researchers across the globe have focused their attention on understanding SARS-CoV-2, the picture that is emerging is that of a virus that has serious effects on the vasculature in multiple organ systems including the cerebral vasculature. Observed effects on the central nervous system includes neurological symptoms (headache, nausea, dizziness), fatal microclot formation and in rare cases encephalitis. However, our understanding of how the virus causes these mild to severe neurological symptoms and how the cerebral vasculature is impacted remains unclear. Thus, the results presented in this report explored whether deleterious outcomes from the SARS-COV-2 viral spike protein on primary human brain microvascular endothelial cells (hBMVECs) could be observed. First, using postmortem brain tissue, we show that the angiotensin converting enzyme 2 or ACE2 (a known binding target for the SARS-CoV-2 spike protein), is expressed throughout various caliber vessels in the frontal cortex. Additionally, ACE2 was also detectable in primary human brain microvascular endothelial (hBMVEC) maintained under cell culture conditions. Analysis for cell viability revealed that neither the S1, S2 or a truncated form of the S1 containing only the RBD had minimal effects on hBMVEC viability within a 48hr exposure window. However, when the viral spike proteins were introduced into model systems that recapitulate the essential features of the Blood-Brain Barrier (BBB), breach to the barrier was evident in various degrees depending on the spike protein subunit tested. Key to our findings is the demonstration that S1 promotes loss of barrier integrity in an advanced 3D microfluid model of the human BBB, a platform that most closely resembles the human physiological conditions at this CNS interface. Subsequent analysis also showed the ability for SARS-CoV-2 spike proteins to trigger a pro-inflammatory response on brain endothelial cells that may contribute to an altered state of BBB function. Together, these results are the first to show the direct impact that the SARS-CoV-2 spike protein could have on brain endothelial cells; thereby offering a plausible explanation for the neurological consequences seen in COVID-19 patients.

neuroscience↗

bioRxiv2020

CD44 regulates blood-brain barrier integrity in response to fluid shear stress.

Fluid shear stress is an important mediator of vascular permeability, yet the molecular mechanisms underlying the response of the blood-brain barrier to shear have yet to be studied in cerebral vasculature despite its importance for brain homeostasis. The goal of this study is to probe components of shear mechanotransduction within the blood-brain barrier to gain a better understanding of pathologies associated with changes in cerebral blood flow including ischemic stroke. Interrogating the effects of shear stress in vivo is complicated by the complexity of factors in the brain parenchyma and the difficulty associated with modulating blood flow regimes. Recent advances in the ability to mimic the in vivo microenvironment using three-dimensional in vitro models provide a controlled setting to study the response of the blood-brain barrier to shear stress. The in vitro model used in this study is compatible with real-time measurement of barrier function using transendothelial electrical resistance as well as immunocytochemistry and dextran permeability assays. These experiments reveal that there is a threshold level of shear stress required for barrier formation and that the composition of the extracellular matrix, specifically the presence of hyaluronan, dictates the flow response. Gene editing to modulate the expression of CD44, a receptor for hyaluronan that previous studies have identified to be mechanosensitive, demonstrates that the receptor is required for the endothelial response to shear stress. Manipulation of small GTPase activity reveals CD44 activates Rac1 while inhibiting RhoA activation. Additionally, adducin-{gamma} localizes to tight junctions in response to shear stress and RhoA inhibition and is required to maintain the barrier. This study identifies specific components of the mechanosensing complex associated with the blood-brain barrier response to fluid shear stress, and therefore illuminates potential targets for barrier manipulation in vivo.

cell biology↗

bioRxiv2018

Loss of vimentin intermediate filaments decreases peri-nuclear stiffness and enhances cell motility through confined spaces

The migration of cells through tight constricting spaces or along fibrous tracks in tissues is important for biological processes, such as embryogenesis, wound healing, and cancer metastasis, and depends on the mechanical properties of the cytoskeleton. Migratory cells often express and upregulate the intermediate filament protein vimentin. The viscoelasticity of vimentin networks in shear deformation has been documented, but its role in motility is largely unexplored. Here, we studied the effects of vimentin on cell motility and stiffness using mouse embryo fibroblasts derived from wild-type and vimentin-null mice. We find that loss of vimentin increases motility through small pores and along thin capillaries. Atomic force microscopy measurements reveal that the presence of vimentin enhances the perinuclear stiffness of the cell, to an extent that depends on surface ligand presentation and therefore signaling from extracellular matrix receptors. Together, our results indicate that vimentin hinders three-dimensional motility by providing mechanical resistance against large strains and may thereby protect the structural integrity of cells.

biophysics↗