CRISPR-Cas9 technology can be used to engineer organoids for studies of gastrointestinal development and disease pathogenesis. In the February issue of Gastroenterology, Masayuki Fujii et al review derivation of organoids from human gastrointestinal tissues and how CRISPR-Cas9 has advanced studies of the digestive system.
CRISPR-Cas9 genome editing technology allows researchers to introduce DNA double-strand breaks at specific genomic loci, to disrupt or knock-in genes more efficiently than other technologies. Epithelial organoids can be derived from stem cells and pluripotent cells from mouse and human intestinal, gastric, esophageal, liver, and pancreatic tissues for study of infections, inflammation, regeneration, and carcinogenesis. These 3-dimensional tissues can be carried indefinitely and have varying levels of cellular complexity, with similarities to organ systems. The CRISPR-Cas9 and organoid technologies can be combined to study the effects of specific genetic changes on tissue function and disease development (see figure).
Fujii et al discuss the use of organoids and CRISPR-Cas9 to study non-neoplastic gastrointestinal diseases such as cystic fibrosis, multiple intestinal atresia, microvillus inclusion disease, and DGAT1 deficiency. Patient-derived organoids have been used to study Barrett’s esophagus and DNA methylation patterns specific to the intestinal mucosa affected by Crohn’s disease. Gastric organoids are used to study the effects of H pylori infection.
The authors review the gastrointestinal cancers that can be modeled using CRISPR-Cas9 modification of gastrointestinal organoids. Fujii et al state that deconstructing the carcinogenic process into single genetic elements by engineering cancer genes in untransformed human organoids is a powerful approach to study how individual genetic alterations contribute to transformation and carcinogenesis. They review the genetic reconstruction of colorectal cancer, pancreatic cancer, and gastric cancer. Organoids derived from colorectal tumors of patients have been modified with CRISPR-Cas9 to label and track cancer stem cells.
These combined technologies can also be used in studies for regenerative medicine. Researchers have engrafted human colonic organoids into the surface of the mouse rectum and generated a lineage-tracing system for human LGR5-positive colon cells. A separate group has shown that human bile duct organoids can stably replace damaged mouse gallbladder walls or common bile ducts. Genetically modified organoids are also ideal for drug screening and identification of genetic factors that affect drug activity and metabolism.
Fujii et al conclude that organoids are now available from every type of healthy and diseased gastrointestinal tissue, and CRISPR-Cas9–mediated editing can be used to identify factors required for homeostasis, pathogenesis, regeneration, and drug response.