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Mechanical Properties of Chondrocytes Estimated from Different Models of Micropipette Aspiration.

ABSTRACT: In this study, two viscoelastic creep expressions for the aspirated length of individual solid-like cells undergoing micropipette aspiration (MPA) were derived based on our previous studies wherein the cell size relative to the micropipette and the cell compressibility were taken into account. Next, three mechanical models of MPA, the half-space model (HSM), incompressible sphere model (ICSM), and compressible sphere model (CSM), were employed to fit the MPA data of chondrocytes. The results indicated that the elastic moduli and viscoelastic parameters of chondrocytes for the ICSM and CSM exhibited significantly higher values than those from the HSM (p < 0.001) because of the considerations of the geometric parameter (?) and the compressibility of the cell (?). For the normal chondrocytes, the elastic moduli obtained from the ICSM and CSM (? = 0.3) were 47.4 and 78.9% higher than those from the HSM. In the viscoelasticity, the parameters k₁, k₂, and ? for the ICSM were respectively increased by 37.8, 37.9, and 39.0% compared to those from the HSM, whereas for the CSM (? = 0.3), the above parameters were 135, 314, and 257% higher compared to those from the HSM. And with the increase of ? and ?, the above mechanical parameters decreased. Furthermore, the thresholds of ? varying with ? were obtained for the given values of relative errors caused by the HSM in the elastic and viscoelastic parameters. The above findings obviously indicated that the geometric parameter of MPA and the Poisson's ratio of a cell have marked influences on the determination of cellular mechanical parameters by MPA and thus should be considered in the pursuit of more accurate investigations of the mechanical properties of cells.

SUBMITTER: Li Y

PROVIDER: S-EPMC6554473 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Mechanical Properties of Chondrocytes Estimated from Different Models of Micropipette Aspiration.

Li Yongsheng Y Li Yueqin Y Zhang Quanyou Q Wang Lili L Guo Meiqing M Wu Xiaogang X Guo Yuan Y Chen Jing J Chen Weiyi W

Biophysical journal 20190425 11

In this study, two viscoelastic creep expressions for the aspirated length of individual solid-like cells undergoing micropipette aspiration (MPA) were derived based on our previous studies wherein the cell size relative to the micropipette and the cell compressibility were taken into account. Next, three mechanical models of MPA, the half-space model (HSM), incompressible sphere model (ICSM), and compressible sphere model (CSM), were employed to fit the MPA data of chondrocytes. The results ind ...[more]

PMID: 31103225

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Project description:The mechanical properties of the cell nucleus are increasingly recognized as critical in many biological processes. The deformability of the nucleus determines the ability of immune and cancer cells to migrate through tissues and across endothelial cell layers, and changes to the mechanical properties of the nucleus can serve as novel biomarkers in processes such as cancer progression and stem cell differentiation. However, current techniques to measure the viscoelastic nuclear mechanical properties are often time consuming, limited to probing one cell at a time, or require expensive, highly specialized equipment. Furthermore, many current assays do not measure time-dependent properties, which are characteristic of viscoelastic materials. Here, we present an easy-to-use microfluidic device that applies the well-established approach of micropipette aspiration, adapted to measure many cells in parallel. The device design allows rapid loading and purging of cells for measurements, and minimizes clogging by large particles or clusters of cells. Combined with a semi-automated image analysis pipeline, the microfluidic device approach enables significantly increased experimental throughput. We validated the experimental platform by comparing computational models of the fluid mechanics in the device with experimental measurements of fluid flow. In addition, we conducted experiments on cells lacking the nuclear envelope protein lamin A/C and wild-type controls, which have well-characterized nuclear mechanical properties. Fitting time-dependent nuclear deformation data to power law and different viscoelastic models revealed that loss of lamin A/C significantly altered the elastic and viscous properties of the nucleus, resulting in substantially increased nuclear deformability. Lastly, to demonstrate the versatility of the devices, we characterized the viscoelastic nuclear mechanical properties in a variety of cell lines and experimental model systems, including human skin fibroblasts from an individual with a mutation in the lamin gene associated with dilated cardiomyopathy, healthy control fibroblasts, induced pluripotent stem cells (iPSCs), and human tumor cells. Taken together, these experiments demonstrate the ability of the microfluidic device and automated image analysis platform to provide robust, high throughput measurements of nuclear mechanical properties, including time-dependent elastic and viscous behavior, in a broad range of applications.

Dataset Information

Mechanical Properties of Chondrocytes Estimated from Different Models of Micropipette Aspiration.

Publications

Mechanical Properties of Chondrocytes Estimated from Different Models of Micropipette Aspiration.

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