From <i>ex ovo</i> to <i>in vitro</i>: xenotransplantation and vascularization of mouse embryonic kidneys in a microfluidic chip.

Abstract

Organoids are emerging as a powerful tool to investigate complex biological structures <i>in vitro</i>. Vascularization of organoids is crucial to recapitulate the morphology and function of the represented human organ, especially in the case of the kidney, whose primary function of blood filtration is closely associated with blood circulation. Current <i>in vitro</i> microfluidic approaches have only provided initial vascularization of kidney organoids, whereas <i>in vivo</i> transplantation to animal models is problematic due to ethical problems, with the exception of xenotransplantation onto a chicken chorioallantoic membrane (CAM). Although CAM can serve as a good environment for vascularization, it can only be used for a fixed length of time, limited by development of the embryo. Here, we propose a novel lab on a chip design that allows organoids of different origin to be cultured and vascularized on a CAM, as well as to be transferred to <i>in vitro</i> conditions when required. Mouse embryonic kidneys cultured on the CAM showed enhanced vascularization by intrinsic endothelial cells, and made connections with the chicken vasculature, as evidenced by blood flowing through them. After the chips were transferred to <i>in vitro</i> conditions, the vasculature inside the organoids was successfully maintained. To our knowledge, this is the first demonstration of the combination of <i>in vivo</i> and <i>in vitro</i> approaches applied to microfluidic chip design.