Introduction
For drug testing and disease researches, both animal models and preclinical trials with cell cultures are extremely important. An impressive percentage of biomedical knowledge and advances were only achieved through animal research and cell culture investigations. Nonetheless, experimenting with animals maintains many limits, as they often respond to pathogens in a different way than humans and also present a different course of the disease, in addition to the ethic concern when animal experiments are involved, besides the obvious ethic limitation when using laboratory lives (Morrisey and Hogan, 2010; Sakamoto, 2012). In regard to monolayer cell cultures, they succeed to imitate some human tissue, but fail to replicate human organs. Also, experiments using animals and cell cultures yield low success rates for new medicines; less than half of new drugs under testing fail due to lack of efficacy or concerns on safety before hitting the market (Arrowsmith and Miller, 2013; Langhans, 2018). Thus, it is understandable and necessary that researchers focus on investigating different research models that can replace the use of animals, yet allowing to simulate human structures as well as diseases more realistically. A rising number of researchers have started to switch from regular, bidimensional (2D) cell culturing to three-dimensional (3D) cultures; while 2D cultures are used for cell expansion and for some tissue-related investigations, the 3D arrangement allows a closer replication of the living situation (Montanez-Sauri et al., 2015). 3D cell culture also presents the possibility of coculturing of different cell lineages in an extracellular matrix-like substance; similar to a full functional organ. In this aspect, they emerge as valuable alternatives to the investigation of functional, biochemical and molecular aspects of human pathologies.