Tumor-associated macrophages, as mentioned in our previous post featuring mouse macrophages, secrete extracellular vesicles (EVs) that range from a variety of sizes and subcellular origins[1]–[5], and that play a role in tumor progression processes like metastasis and chemotherapy resistance[6]–[8]. The nature of such structures remains still unexplained.
Following a proposed method [5], tumor-derived EVs were isolated from breast cancer cells. They were then harvested and labelled with a fluorescent lipid.
After that, the tumor-derived EVs were added to a mouse brain endothelial cell culture and their uptake was monitored for 11 hours under Nanolive’s 3D Cell Explorer-fluo. While data regarding refractive index was obtained every 10 seconds, fluorescence acquisitions were at a slower frequency in order to avoid fluorescence-induced cell perturbations that may had compromised the observed phenomenon.
Fluorescence increases over time as EVs uptake increases.
As a direct consequence of EVs uptake, newly formed membrane structures are visible using Nanolive’s imaging. They appear as small, dotty, membrane-dense structures, growing at the center of the fluorescent signal.
One of such structures shows a striking dynamic, while at first stationary, far from the nucleus within a spread-out part of the cytoplasm, it suddenly migrates towards the nucleus (signaled with arrows on the video). This new dynamic process is certainly part of the mechanism allowing extracellular vesicles to influence the cellular fate and as such is of great interest. The potential impact of this process on brain endothelial cells can be devastating.
You might have noticed that in comparison to the previously published mouse macrophages uptake, brain endothelial cells have a reduced uptake rate. This is due to the fact that, contrarily to macrophages, brain cells are not specialized in uptake processes.
[1] S. Caruso and I. K. H. Poon, “Apoptotic cell-derived extracellular vesicles: More than just debris,” Frontiers in Immunology, vol. 9, no. JUN. Frontiers Media S.A., 28-Jun-2018.
[2] M. Colombo, G. Raposo, and C. Théry, “Biogenesis, Secretion, and Intercellular Interactions of Exosomes and Other Extracellular Vesicles,” Annu. Rev. Cell Dev. Biol., vol. 30, no. 1, pp. 255–289, Oct. 2014.
[3] M. Mathieu, L. Martin-Jaular, G. Lavieu, and C. Théry, “Specificities of secretion and uptake of exosomes and other extracellular vesicles for cell-to-cell communication,” Nature Cell Biology, vol. 21, no. 1. Nature Publishing Group, pp. 9–17, 01-Jan-2019.
[4] G. Van Niel, G. D’Angelo, and G. Raposo, “Shedding light on the cell biology of extracellular vesicles,” Nature Reviews Molecular Cell Biology, vol. 19, no. 4. Nature Publishing Group, pp. 213–228, 01-Apr-2018.
[5] C. Cianciaruso et al., “Molecular Profiling and Functional Analysis of Macrophage-Derived Tumor Extracellular Vesicles,” Cell Rep., vol. 27, no. 10, pp. 3062-3080.e11, Jun. 2019.
[6] C. F. Ruivo, B. Arbara Adem, M. Silva, S. Onia, and A. Melo, “The Biology of Cancer Exosomes: Insights and New Perspectives,” 2017.
[7] I. Keklikoglou, C. Cianciaruso, E. Güç, … M. S.-N. cell, and undefined 2019, “Chemotherapy elicits pro-metastatic extracellular vesicles in breast cancer models,” nature.com.
[8] A. Becker, B. K. Thakur, J. M. Weiss, H. S. Kim, H. Peinado, and D. Lyden, “Extracellular Vesicles in Cancer: Cell-to-Cell Mediators of Metastasis,” Cancer Cell, vol. 30, no. 6. Cell Press, pp. 836–848, 12-Dec-2016.
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