1
|
Thomas-Chemin O, Séverac C, Trévisiol E, Dague E. Indentation of living cells by AFM tips may not be what we thought! Micron 2023; 174:103523. [PMID: 37595406 DOI: 10.1016/j.micron.2023.103523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 08/08/2023] [Accepted: 08/08/2023] [Indexed: 08/20/2023]
Abstract
The models used to calculate Young's moduli from atomic force microscopy (AFM) force curves consider the shape of the indentation. It is then assumed that the geometry of the indentation is identical to the geometry of the indenter, which has been verified for hard materials (E > 1 MPa). Based on this assumption, the force curves calculated by these models, for the same object with a given Young's modulus, are different if the indenter geometry is different. On the contrary, we observe experimentally that the force curves recorded on soft living cells, with pyramidal, spherical, or tipless indenters, are almost similar. This indicates that this basic assumption on the indentation geometry does not work for soft materials (E of the order of 5 kPa or less). This means that, in this case, the shape of the indentation is therefore different from the shape of the indenter. Indentation of living cells by AFM is not what we thought!
Collapse
Affiliation(s)
| | - Childérick Séverac
- RESTORE Research Center, Université de Toulouse, INSERM, CNRS, EFS, ENVT, Université P. Sabatier, Toulouse, France
| | | | - Etienne Dague
- LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, France.
| |
Collapse
|
2
|
Krzemien L, Giergiel M, Kurek A, Barbasz J. The role of the cortex in indentation experiments of animal cells. Biomech Model Mechanobiol 2023; 22:177-187. [PMID: 36282360 PMCID: PMC9958175 DOI: 10.1007/s10237-022-01639-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 09/07/2022] [Indexed: 11/28/2022]
Abstract
We present a model useful for interpretation of indentation experiments on animal cells. We use finite element modeling for a thorough representation of the complex structure of an animal cell. In our model, the crucial constituent is the cell cortex-a rigid layer of cytoplasmic proteins present on the inner side of the cell membrane. It plays a vital role in the mechanical interactions between cells. The cell cortex is modeled by a three-dimensional solid to reflect its bending stiffness. This approach allows us to interpret the results of the indentation measurements and extract the mechanical properties of the individual elements of the cell structure. During the simulations, we scan a broad range of parameters such as cortex thickness and Young's modulus, cytoplasm Young's modulus, and indenter radius, which define cell properties and experimental conditions. Finally, we propose a simple closed-form formula that approximates the simulated results with satisfactory accuracy. Our formula is as easy to use as Hertz's function to extract cell properties from the measurement, yet it considers the cell's inner structure, including cell cortex, cytoplasm, and nucleus.
Collapse
Affiliation(s)
- Leszek Krzemien
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30239 Krakow, Poland
| | - Magdalena Giergiel
- Department of Physics of Nanostructures and Nanotechnology, Institute of Physics, Jagiellonian University, Prof. Stanislawa Lojasiewicza 11, 30348, Krakow, Poland.
| | - Agnieszka Kurek
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30239 Krakow, Poland
| | - Jakub Barbasz
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30239 Krakow, Poland
| |
Collapse
|
3
|
Abstract
PURPOSE OF REVIEW Aging is an important risk factor for cardiovascular disease and is associated with increased vessel wall stiffness. Pathophysiological stiffening, notably in arteries, disturbs the integrity of the vascular endothelium and promotes permeability and transmigration of immune cells, thereby driving the development of atherosclerosis and related vascular diseases. Effective therapeutic strategies for arterial stiffening are still lacking. RECENT FINDINGS Here, we overview the literature on age-related arterial stiffening, from patient-derived data to preclinical in-vivo and in-vitro findings. First, we overview the common techniques that are used to measure stiffness and discuss the observed stiffness values in atherosclerosis and aging. Next, the endothelial response to stiffening and possibilities to attenuate this response are discussed. SUMMARY Future research that will define the endothelial contribution to stiffness-related cardiovascular disease may provide new targets for intervention to restore endothelial function in atherosclerosis and complement the use of currently applied lipid-lowering, antihypertensive, and anti-inflammatory drugs.
Collapse
Affiliation(s)
- Aukie Hooglugt
- Amsterdam UMC, University of Amsterdam, Department of Medical Biochemistry, Amsterdam Cardiovascular Sciences
- Amsterdam UMC, VU University Medical Center, Department of Physiology, Amsterdam Cardiovascular Sciences, Amsterdam, The Netherlands
| | - Olivia Klatt
- Amsterdam UMC, University of Amsterdam, Department of Medical Biochemistry, Amsterdam Cardiovascular Sciences
| | - Stephan Huveneers
- Amsterdam UMC, University of Amsterdam, Department of Medical Biochemistry, Amsterdam Cardiovascular Sciences
| |
Collapse
|
4
|
Adelson RP, Palikuqi B, Weiss Z, Checco A, Schreiner R, Rafii S, Rabbany SY. Morphological characterization of Etv2 vascular explants using fractal analysis and atomic force microscopy. Microvasc Res 2021; 138:104205. [PMID: 34146583 DOI: 10.1016/j.mvr.2021.104205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 05/28/2021] [Accepted: 06/07/2021] [Indexed: 11/25/2022]
Abstract
The rapid engraftment of vascular networks is critical for functional incorporation of tissue explants. However, existing methods for inducing angiogenesis utilize approaches that yield vasculature with poor temporal stability or inadequate mechanical integrity, which reduce their robustness in vivo. The transcription factor Ets variant 2 (Etv2) specifies embryonic hematopoietic and vascular endothelial cell (EC) development, and is transiently reactivated during postnatal vascular regeneration and tumor angiogenesis. This study investigates the role for Etv2 upregulation in forming stable vascular beds both in vitro and in vivo. Control and Etv2+ prototypical fetal-derived human umbilical vein ECs (HUVECs) and adult ECs were angiogenically grown into vascular beds. These vessel beds were characterized using fractal dimension and lacunarity, to quantify their branching complexity and space-filling homogeneity, respectively. Atomic force microscopy (AFM) was used to explore whether greater complexity and homogeneity lead to more mechanically stable vessels. Additionally, markers of EC integrity were used to probe for mechanistic clues. Etv2+ HUVECs exhibit greater branching, vessel density, and structural homogeneity, and decreased stiffness in vitro and in vivo, indicating a greater propensity for stable vessel formation. When co-cultured with colon tumor organoid tissue, Etv2+ HUVECs had decreased fractal dimension and lacunarity compared to Etv2+ HUVECs cultured alone, indicating that vessel density and homogeneity of vessel spacing increased due to the presence of Etv2. This study sets forth the novel concept that fractal dimension, lacunarity, and AFM are as informative as conventional angiogenic measurements, including vessel branching and density, to assess vascular perfusion and stability.
Collapse
Affiliation(s)
- Robert P Adelson
- Bioengineering Program, DeMatteis School of Engineering and Applied Science, Hofstra University, Hempstead, NY, USA
| | - Brisa Palikuqi
- Division of Regenerative Medicine, Ansary Stem Cell Institute, Department of Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Zachary Weiss
- Bioengineering Program, DeMatteis School of Engineering and Applied Science, Hofstra University, Hempstead, NY, USA
| | - Antonio Checco
- Bioengineering Program, DeMatteis School of Engineering and Applied Science, Hofstra University, Hempstead, NY, USA
| | - Ryan Schreiner
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Shahin Rafii
- Division of Regenerative Medicine, Ansary Stem Cell Institute, Department of Medicine, Weill Cornell Medicine, New York, NY, USA
| | - Sina Y Rabbany
- Bioengineering Program, DeMatteis School of Engineering and Applied Science, Hofstra University, Hempstead, NY, USA; Division of Regenerative Medicine, Ansary Stem Cell Institute, Department of Medicine, Weill Cornell Medicine, New York, NY, USA.
| |
Collapse
|
5
|
Huang C, Sun PP, Won J, Wang Y, Boppart SA, Nguyen TH. Effect of Nonphosphorus Corrosion Inhibitors on Biofilm Pore Structure and Mechanical Properties. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:14716-14724. [PMID: 33124800 PMCID: PMC7949192 DOI: 10.1021/acs.est.0c04645] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Understanding the effects of biofilm structural and mechanical properties, which can influence biofilm cohesiveness and detachment under physical stress, is critical for biofilm and biofilm-associated pathogen control. In this study, we used optical coherence tomography (OCT) and nanoindentation to determine the role of silicate and tin (two experimental nonphosphate corrosion inhibitors) on the porous structure and stiffness of three types of multispecies biofilms. These biofilms were grown from groundwater (a drinking water source), and this groundwater was amended with either tin or silicate corrosion inhibitor (0.5 mg/L as Sn and 20 mg/L as SiO2). Based on the elastic moduli of these biofilms, tin biofilms and groundwater biofilms were the stiffest, followed by silicate biofilms. The thickness normalized by the growth time for silicate biofilms was highest at 38 ± 7.1 μm/month, compared to 21 ± 3.2 and 11 ± 2.4 μm/month for tin biofilms and groundwater biofilms, respectively. The silicate biofilms had the greatest overall porosities and were thickest among the three biofilms. Based on the pore network modeling (PNM) of OCT images, larger pores and connections were found in the silicate biofilms compared to those in tin and groundwater biofilms. Our analysis showed that the thicker and more porous biofilms (silicate biofilms) were potentially less resistant to deformation than the thinner and denser biofilms (tin and groundwater biofilms).
Collapse
Affiliation(s)
- Conghui Huang
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Peter P Sun
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Jungeun Won
- Departments of Electrical and Computer Engineering and Bioengineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yin Wang
- Department of Civil and Environmental Engineering, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, United States
| | - Stephen A Boppart
- Departments of Electrical and Computer Engineering and Bioengineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Thanh H Nguyen
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Institute of Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| |
Collapse
|
6
|
Thal LB, Mann VR, Sprinzen D, McBride JR, Reid KR, Tomlinson ID, McMahon DG, Cohen BE, Rosenthal SJ. Ligand-conjugated quantum dots for fast sub-diffraction protein tracking in acute brain slices. Biomater Sci 2020; 8:837-845. [PMID: 31790090 PMCID: PMC7002256 DOI: 10.1039/c9bm01629e] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Semiconductor quantum dots (QDs) have demonstrated utility in long-term single particle tracking of membrane proteins in live cells in culture. To extend the superior optical properties of QDs to more physiologically relevant cell platforms, such as acute brain slices, we examine the photophysics of compact ligand-conjugated CdSe/CdS QDs using both ensemble and single particle analysis in brain tissue media. We find that symmetric core passivation is critical for both photostability in oxygenated media and for prolonged single particle imaging in brain slices. We then demonstrate the utility of these QDs by imaging single dopamine transporters in acute brain slices, achieving 20 nm localization precision at 10 Hz frame rates. These findings detail design requirements needed for new QD probes in complex living environments, and open the door to physiologically relevant studies that capture the utility of QD probes in acute brain slices.
Collapse
Affiliation(s)
- Lucas B Thal
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Vahabikashi A, Gelman A, Dong B, Gong L, Cha EDK, Schimmel M, Tamm ER, Perkumas K, Stamer WD, Sun C, Zhang HF, Gong H, Johnson M. Increased stiffness and flow resistance of the inner wall of Schlemm's canal in glaucomatous human eyes. Proc Natl Acad Sci U S A 2019; 116:26555-26563. [PMID: 31806762 PMCID: PMC6936716 DOI: 10.1073/pnas.1911837116] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cause of the elevated outflow resistance and consequent ocular hypertension characteristic of glaucoma is unknown. To investigate possible causes for this flow resistance, we used atomic force microscopy (AFM) with 10-µm spherical tips to probe the stiffness of the inner wall of Schlemm's canal as a function of distance from the tissue surface in normal and glaucomatous postmortem human eyes, and 1-µm spherical AFM tips to probe the region immediately below the tissue surface. To localize flow resistance, perfusion and imaging methods were used to characterize the pressure drop in the immediate vicinity of the inner wall using giant vacuoles that form in Schlemm's canal cells as micropressure sensors. Tissue stiffness increased with increasing AFM indentation depth. Tissues from glaucomatous eyes were stiffer compared with normal eyes, with greatly increased stiffness residing within ∼1 µm of the inner-wall surface. Giant vacuole size and density were similar in normal and glaucomatous eyes despite lower flow rate through the latter due to their higher flow resistance. This implied that the elevated flow resistance found in the glaucomatous eyes was localized to the same region as the increased tissue stiffness. Our findings implicate pathological changes to biophysical characteristics of Schlemm's canal endothelia and/or their immediate underlying extracellular matrix as cause for ocular hypertension in glaucoma.
Collapse
Affiliation(s)
- Amir Vahabikashi
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
| | - Ariel Gelman
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Biqin Dong
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201
| | - Lihua Gong
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Elliott D. K. Cha
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Margit Schimmel
- Institute of Anatomy, University of Regensburg, D-93053 Regensburg, Germany
| | - Ernst R. Tamm
- Institute of Anatomy, University of Regensburg, D-93053 Regensburg, Germany
| | | | - W. Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, NC 27710
- Department of Biomedical Engineering, Duke University, Durham, NC 27708
| | - Cheng Sun
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201
| | - Hao F. Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611
| | - Haiyan Gong
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Mark Johnson
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611
| |
Collapse
|
8
|
Endothelin receptor-A mediates degradation of the glomerular endothelial surface layer via pathologic crosstalk between activated podocytes and glomerular endothelial cells. Kidney Int 2019; 96:957-970. [PMID: 31402170 DOI: 10.1016/j.kint.2019.05.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 04/08/2019] [Accepted: 05/02/2019] [Indexed: 12/15/2022]
Abstract
Emerging evidence of crosstalk between glomerular cells in pathological settings provides opportunities for novel therapeutic discovery. Here we investigated underlying mechanisms of early events leading to filtration barrier defects of podocyte and glomerular endothelial cell crosstalk in the mouse models of primary podocytopathy (podocyte specific transforming growth factor-β receptor 1 signaling activation) or Adriamycin nephropathy. We found that glomerular endothelial surface layer degradation and albuminuria preceded podocyte foot process effacement. These abnormalities were prevented by endothelin receptor-A antagonism and mitochondrial reactive oxygen species scavenging. Additional studies confirmed increased heparanase and hyaluronoglucosaminidase gene expression in glomerular endothelial cells in response to podocyte-released factors and to endothelin-1. Atomic force microscopy measurements showed a significant reduction in the endothelial surface layer by endothelin-1 and podocyte-released factors, which could be prevented by endothelin receptor-A but not endothelin receptor-B antagonism. Thus, our studies provide evidence of early crosstalk between activated podocytes and glomerular endothelial cells resulting in loss of endothelial surface layer, glomerular endothelial cell injury and albuminuria. Hence, activation of endothelin-1-endothelin receptor-A and mitochondrial reactive oxygen species contribute to the pathogenesis of primary podocytopathies in experimental focal segmental glomerulosclerosis.
Collapse
|