Dataset Information

Mechanical Characterization of 3D Ovarian Cancer Nodules Using Brillouin Confocal Microscopy.

ABSTRACT: Introduction:The mechanical interaction between cells and their microenvironment is emerging as an important determinant of cancer progression and sensitivity to treatment, including in ovarian cancer (OvCa). However, current technologies limit mechanical analysis in 3D culture systems. Brillouin Confocal Microscopy is an optical non-contact method to assess the mechanical properties of biological materials. Here, we validate the ability of this technology to assess the mechanical properties of 3D tumor nodules. Methods:OvCa cells were cultured in 3D using two established methods: (1) overlay cultures on Matrigel; (2) spheroids in ultra-low attachment plates. To alter the mechanical state of these tumors, nodules were immersed in PBS with varying levels of sucrose to induce osmotic stress. Next, nodule mechanical properties were measured by Brillouin microscopy and validated with standard stress-strain tests: Atomic Force Microscopy (AFM) and a parallel plate compression device (Microsquisher). Finally, the nodules were treated with a chemotherapeutic commonly used to manage OvCa, carboplatin, to determine treatment-induced effects on tumor mechanical properties. Results:Brillouin microscopy allows mechanical analysis with limited penetration depth (~?92 µm for Matrigel method; ~?54 µm for low attachment method). Brillouin microscopy metrics displayed the same trends as the corresponding "gold-standard" Young's moduli measured with stress-strain methods when the osmolality of the medium was increased. Nodules treated with carboplatin showed a decrease in Brillouin frequency shift. Conclusion:This validation study paves the way to evaluate the mechanics of 3D nodules, with micron-scale three-dimensional resolution and without contact, thus extending the experimental possibilities.

SUBMITTER: Conrad C

PROVIDER: S-EPMC6816613 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Mechanical Characterization of 3D Ovarian Cancer Nodules Using Brillouin Confocal Microscopy.

Conrad Christina C Gray Kelsey M KM Stroka Kimberly M KM Rizvi Imran I Scarcelli Giuliano G

Cellular and molecular bioengineering 20190507 3

<h4>Introduction</h4>The mechanical interaction between cells and their microenvironment is emerging as an important determinant of cancer progression and sensitivity to treatment, including in ovarian cancer (OvCa). However, current technologies limit mechanical analysis in 3D culture systems. Brillouin Confocal Microscopy is an optical non-contact method to assess the mechanical properties of biological materials. Here, we validate the ability of this technology to assess the mechanical proper ...[more]

PMID: 31719911

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Project description:Altered biophysical properties of cancer cells and of their microenvironment contribute to cancer progression. While the relationship between microenvironmental stiffness and cancer cell mechanical properties and responses has been previously studied using two-dimensional (2D) systems, much less is known about it in a physiologically more relevant 3D context and in particular for multicellular systems. To investigate the influence of microenvironment stiffness on tumor spheroid mechanics, we first generated MCF-7 tumor spheroids within matrix metalloproteinase (MMP)-degradable 3D polyethylene glycol (PEG)-heparin hydrogels, where spheroids showed reduced growth in stiffer hydrogels. We then quantitatively mapped the mechanical properties of tumor spheroids in situ using Brillouin microscopy. Maps acquired for tumor spheroids grown within stiff hydrogels showed elevated Brillouin frequency shifts (hence increased longitudinal elastic moduli) with increasing hydrogel stiffness. Maps furthermore revealed spatial variations of the mechanical properties across the spheroids' cross-sections. When hydrogel degradability was blocked, comparable Brillouin frequency shifts of the MCF-7 spheroids were found in both compliant and stiff hydrogels, along with similar levels of growth-induced compressive stress. Under low compressive stress, single cells or free multicellular aggregates showed consistently lower Brillouin frequency shifts compared to spheroids growing within hydrogels. Thus, the spheroids' mechanical properties were modulated by matrix stiffness and degradability as well as multicellularity, and also to the associated level of compressive stress felt by tumor spheroids. Spheroids generated from a panel of invasive breast, prostate and pancreatic cancer cell lines within degradable stiff hydrogels, showed higher Brillouin frequency shifts and less cell invasion compared to those in compliant hydrogels. Taken together, our findings contribute to a better understanding of the interplay between cancer cells and microenvironment mechanics and degradability, which is relevant to better understand cancer progression.

Project description:In the last years, microdosimetric numerical models of cells including intracellular compartments have been proposed, aiming to investigate the poration induced by the application of nanosecond pulsed electric fields (nsPEFs). A limitation of such models was the extremely approximate cell and organelle shapes, leading to an incorrect estimation of the electric field or transmembrane potential distribution in the studied domain. In order to obtain a reliable model of in vitro experiments and a one-to-one comparison between experimental and simulated results, here, a realistic model of 12 human mesenchymal stem cells was built starting from their optical microscopy images where different cell compartments were highlighted. The microdosimetric analysis of the cells group was quantified in terms of electric field and transmembrane potentials (TMPs) induced by an externally applied 10-ns trapezoidal pulse with rise and fall times of 2 ns, with amplitudes ranging from 2 to 30 MV/m. The obtained results showed that the plasma and endoplasmic reticulum (ER) membrane of each cell respond in a different way to the same electric field amplitude, depending on differences in shape, size, and position of the single cell with respect to the applied electric field direction. Therefore, also the threshold for an efficient electroporation is highly different from cell to cell. This difference was quantitatively estimated through the cumulative distribution function of the pore density for the plasma and ER membrane of each cell, representing the probability that a certain percentage of membrane has reached a specific value of pore density. By comparing the dose-response curves resulted from the simulations and those from the experimental study of De Menorval et al. (2016), we found a very good matching of results for plasma and ER membrane when 2% of the porated area is considered sufficient for permeabilizing the membrane. This result is worth of noting as it highlights the possibility to effectively predict the behavior of a cell (or of a population of cells) exposed to nsPEFs. Therefore, the microdosimetric realistic model described here could represent a valid tool in setting up more efficient and controlled electroporation protocols.

Dataset Information

Mechanical Characterization of 3D Ovarian Cancer Nodules Using Brillouin Confocal Microscopy.

Publications

Mechanical Characterization of 3D Ovarian Cancer Nodules Using Brillouin Confocal Microscopy.

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