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| Palisades are multi-cellular circular structures that can be localized around occluded vascular vessels in glioblastomas. This geometry suggests the following formation process. Initially the tumour grows around the vasculature in a cylindrical shape. This structure facilitates the tumour supply of oxygen and nutrients. The cells that are closest positioned to the vessel obtain have
a better access to nutrients and oxygen than those positioned at the outer parts. At a certain point, due to tumor growth, the pressure exerted by the tumor cells on the vessel is such that to cause vessel collapse. This moment represents a dramatical change for those cells that were positioned nearby to the vessel. After collapse they loose oxygen and nutrient supply as they are at the centre of tumour. As a consequence they become hypoxic and, if the tumour geometry or the irrigating vasculature do not change, they die. At the outer rim of the tumour, the effects of vessel collapse are different. In this region, the cells are not immersed in the tumour mass and when lack of oxygen and nutrients occurs they can activate migration mechanisms that allow them to invade the nearby tissue in the search for areas where oxygen and nutrients are available. The collective migration results in the formation of a palisade.
Observation of palisades under microscopy is constrained to two dimensional layers as a consequence of the experimental setups. Advanced microscopy has been able to reproduce three dimensional images of particular tissue structures,
however, up to our knowledge, a three dimensional shape of palisades has not been reproduced yet.
This is due to the difficult constraints that glioblastomas represent to be observed in-vivo. In this talk we present three dimensional realistic simulations, based on a multi-scale coupling of the evolution of tumor cells and the oxygen diffusion in tissue (treating blood vessels as immersed boundaries),
that depict the shape of palisades during its formation. These images can provide to clinicians and biologists for a better understanding of the palisades 3-D structure and how glioblastomas grow. |
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