Peter van Mourik

85 Forskolin-induced swelling protocol Figure 3 . Example of a goo d quality biopsy. Note the pink colour and round shape. Transport of biopsies to the laboratory CRITICAL: Intestinal crypts can be retrieved from a rectal/ colon biopsy (hereafter referred to as “colon biopsy”) with a high efficiency (> 95% success rate) within 48 h of the biopsy collection. However, tissue quality gradually decreases over time leading to a reduced chance of successfully isolating crypts from the biopsies. Therefore, immediate transport of the colon biopsies at 4 °C in AD-DF+++ is essential to ensure successful crypt isolation and establish efficient colon organoid cultures. Note: Good quality colon biopsies should be round and have a slightly pink to red colour (see figure 3 & 4). When you are uncertain about the quality of the rectal biopsies, please check if intestinal crypts are visible under the light microscope. Good quality biopsies show a honeycomb- like structure in which the stem cell crypts reside. If this structure is not visible, the biopsy is of bad quality (figure 4B). Figure 4. Examples of biopsies as viewed under a microscope (bright field, 4 x magnification). (A) Good quality biopsies, note the honeycomb structure indicative of intestinal crypts. (B) Bad quality biopsies, this can be due to lack of tissue depth of the biopsy leading to an absence of intestinal crypts. 4