Optical quantification of intracellular mass density and cell mechanics in 3D mechanical confinement
Optical quantification of intracellular mass density and cell mechanics in 3D mechanical confinement
复制标题
DOI：
10.1039/d0sm01556c
复制
发表时间：
2021-01-28
期刊：
影响因子：
3.4
通讯作者：
Cipitria, Amaia
中科院分区：
文献类型：
--
作者：
Bakhshandeh, Sadra;Taieb, Hubert M.;Cipitria, Amaia
已知细胞的生物物理性质如细胞内质量密度和细胞力学涉及广泛的稳态功能和病理改变。可用于量化此类性质的光学读出是折射率（RI）分布。最近有报道称，最初被认为是细胞内具有最高干质量密度（rho）的细胞器的细胞核实际上具有比其周围的细胞质更低的RI和rho。这些研究要么在悬浮细胞中进行，要么在粘附在2D基底上的细胞中进行，这两种情况都没有反映出细胞被细胞外基质（ECM）包围的体内情况。为了更好地近似3D的情况下，我们封装在3D共价交联的海藻酸盐水凝胶与不同的刚度的细胞，并成像细胞的3D RI分布，使用组合的光学衍射断层扫描（ODT）-落射荧光显微镜。出乎意料的是，与2D培养物相比，3D中的细胞核显示出比细胞质更高的rho。使用布里渊-落射荧光显微镜，我们随后表明，除了更高的rho，细胞核还具有更高的纵向模量（M）和粘度（eta）相比，细胞质。此外，增加水凝胶的刚度导致与顺应性3D藻酸盐中的细胞相比，刚性3D藻酸盐中的细胞的细胞核和细胞质的M更高。用非侵入性技术量化细胞内生物物理特性的能力将提高我们对生物过程如休眠、凋亡、细胞生长或干细胞分化的理解。
Biophysical properties of cells such as intracellular mass density and cell mechanics are known to be involved in a wide range of homeostatic functions and pathological alterations. An optical readout that can be used to quantify such properties is the refractive index (RI) distribution. It has been recently reported that the nucleus, initially presumed to be the organelle with the highest dry mass density (rho) within the cell, has in fact a lower RI and rho than its surrounding cytoplasm. These studies have either been conducted in suspended cells, or cells adhered on 2D substrates, neither of which reflects the situation in vivo where cells are surrounded by the extracellular matrix (ECM). To better approximate the 3D situation, we encapsulated cells in 3D covalently-crosslinked alginate hydrogels with varying stiffness, and imaged the 3D RI distribution of cells, using a combined optical diffraction tomography (ODT)-epifluorescence microscope. Unexpectedly, the nuclei of cells in 3D displayed a higher rho than the cytoplasm, in contrast to 2D cultures. Using a Brillouin-epifluorescence microscope we subsequently showed that in addition to higher rho, the nuclei also had a higher longitudinal modulus (M) and viscosity (eta) compared to the cytoplasm. Furthermore, increasing the stiffness of the hydrogel resulted in higher M for both the nuclei and cytoplasm of cells in stiff 3D alginate compared to cells in compliant 3D alginate. The ability to quantify intracellular biophysical properties with non-invasive techniques will improve our understanding of biological processes such as dormancy, apoptosis, cell growth or stem cell differentiation.