Necessary, Legendary and Detrimental Components of Human Colorectal Organoid Culture Medium: Raising Awareness to Reduce Experimental Bugs

The creation of a specific culture medium for colorectal organoids in 2011 opened a new era in human primary cultures by enabling the indefinite expansion of normal and pathological epithelial organoids. The original formula has been used ever since, with only minor, lab-specific modifications. The goal of culturing organoids from dif-ferent tissues has relied on saving and propagating the pluripotent stem cell. The "magic bullet" and all its subsequent derivatives have pursued this goal. Consequently, agonist and antagonist signals are chronically activated in the organoid medium, forcing organoid cells (as well as any other co-cultured cellular model) into con-strained signaling pathways. This extremely artificial condition is often overlooked in experimental approaches and may bias the results. Furthermore, some molecules in the organoid medium have unpredictable off-target effects that significantly impact the behavior and maturation of certain cell populations. In this short review, we will ex-amine the components of the colorectal organoid medium, describing their activity and necessity for organoid culture. We will also discuss the expected biases in specific experimental settings. While the original organoid medium formula is the gold stand-ard for propagating organoids in vitro, more focused, reliable conditions are necessary for specific organoid-based tests.