Nuovi approcci nello sviluppo di modelli in vitro vascolarizzati

Several culture methods are available in research, among these 3D cell cultures in vitro are becoming popular due to their ability to withstand complex experiment. In addition, they can resemble in a more accurate way natural animal systems compared to bidimensional culture techniques. However, it is essential to identify potential limitations to provide more effective models. This work aims at presenting which restraints need to be overcome with a focus on the issue of vascularization. Namely, the lack of efficient and perfused vessels in organoids, strongly limits their functionality. Hence many groups of research developed protocols to promote vessel formation. In this thesis are presented three papers in which the authors aim at ameliorating different types of organoids by acting directly on cells during the generation of the model. The approach chosen by Low, J.H. et al. consists in promoting the formation of a vascular network in kidney organoid exploiting the induction with a specific subset of growth factors. The same goal has been achieved by the group of Holloway, E. M. et al. by choosing a completely different method. They verified the presence of endothelial cells by performing a transcriptomic analysis during the development of intestinal organoids. Then, upon the characterization and isolation of these ECs, the authors established a novel protocol to prolong the survival and expansion of the endothelium in the model. This procedure allowed to stimulate vessel formation, leading to the generation of vascularized Human Intestinal Organoids. Finally, in the article published in Nature by Palikuqi, B. et al. it is presented a novel technique which allows to reprogram adult endothelial cells, generating reset vascular endothelial cells. The reprogramming is mediated by the induction of hematoendothelial fate modulator, in particular the expression of ETV2 in turns stimulates the assembly of perfused 3D vessels in colorectal organoids and tumoroids. To conclude, the purpose of this work is to depict different approaches aiming at ameliorating threedimensional models by facing the lack of a functional vasculature network.