Fig. 3

Model systems for studying neurodegeneration. Established experimental models of disease can be categorized into three main areas: in vitro, ex vivo and in vivo. Each type of model system has advantages that can be leveraged to explore disease mechanisms; however, disadvantages exist for each avenue. In vitro models such as cell lines and purified primary cells are a rapid and inexpensive way to explore disease mechanisms, however, extrapolation of results to biological systems is difficult. Ex vivo models, such as the growth of organoids in culture or explanted tissue cultures are multicellular, allow more complex mechanistic questions to be explored. However, they are not ideal representations of in vivo situations due to lack of vascular or peripheral immune components. In vivo models include animals such as non-human primates, mice and rats, Drosophila and Caenorhabditis elegans, and others. Although these models allow for in vivo studies of disease, the cost is high, and the results may not always translate well to human biology.