It has long been known that cells cultured in two dimensions (2D) are not representative of the in vivo situation as a result of their growth being restricted to a flat surface. This minimises cell-cell and cell-matrix interactions, causing the distinctive phenotype to be lost and the cells to react differently to external cues, yet 2D cell culture remains one of the mainstays of research programmes worldwide. Numerous failures in translating effective therapies from cell models into humans can partly be attributed to a reliance on 2D cell culture, and have driven the development of more physiologically relevant human models. With the establishment of three-dimensional (3D) cell culture methods during the past few decades significant advancement of a wide range of therapeutic strategies has been afforded; a key breakthrough within this field has been the development of organoid technology.
The term organoid is used to describe a 3D cell culture which consists of organ-specific cell types. These simplified mini organs share the in vivo architecture and functionality of the original tissue, making them ideal model systems for research. Organoids can be generated from primary tissue samples which contain adult stem cells, from embryonic stem cells (ESC) or from induced pluripotent stem cells (iPSC), and their development represents one of the most exciting recent advancements in stem cell research. The number of publications referencing organoids has increased dramatically in the last ten years, with their use described for disease modelling, drug screening, regenerative therapy, host-microbe interactions and for studies of organogenesis and morphogenesis.
Patient-derived organoids hold huge potential for increasing our understanding of various disease states and predicting treatment response. They also open up many possibilities for personalised medicine. For example, transcriptional and proteomic analyses performed on organoid models derived from normal and neoplastic pancreas tissues have been used to identify key genes associated with progression of pancreatic cancer1, while our understanding of the neurobiology of Zika virus has advanced through the use of brain organoids; organoid modelling followed by ZIKV infection has suggested neural progenitor cells to be particularly susceptible to infection2. In another study, the CRISPR/Cas9 genome editing system has been used to correct the CFTR locus by homologous recombination in cultured intestinal stem cells of cystic fibrosis patients, providing proof of concept for gene correction in primary adult stem cells derived from patients with a single-gene hereditary defect3.
As organoid research has increased in popularity, the range of supporting tools and reagents has grown accordingly. A number of companies offer high quality media products, matrix components, growth factors and small molecules designed specifically for organoid generation, while others provide protocols and technical support to promote the successful establishment of organoid cultures. We should of course remember that organoid culture, although extremely sophisticated, is in reality simply an advanced form of cell culture; as such many existing tried and trusted reagents are applicable to this research field. For example, PeproTech’s extensive range of cytokines and growth factors may be used in organoid research, and their epidermal growth factor (EGF), Noggin and R-Spondin proteins were all cited in a recent publication describing the establishment of different 3D systems, including organoid culture, to culture gastrointestinal epithelium.
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