Human colon stem cells have been identified and grown in a lab-plate for the first time. This achievement, made by researchers of the Colorectal Cancer Lab at the Institute for Research in Biomedicine (IRB Barcelona) and published in Nature Medicine, is a crucial advance towards regenerative medicine.
Throughout life, stem cells of the colon regenerate the inner layer of our large intestine in a weekly basis. For decades scientists had evidences of the existence of these cells yet their identity remained elusive. Scientists led by the ICREA Professor and researcher at the Institute for Research in Biomedicine (IRB Barcelona) Eduard Batlle discovered the precise localization of the stem cells in the human colon and worked out a method that allows their isolation and in vitro expansion, that is their propagation in lab-plates. Growing cells outside the body generally requires providing the cells in a lab-plate with the right mix of nutrients, growth factors and hormones. But in the same way that each of the more than 200 types of cells in our body differs from the others so too do optimal growing conditions in the lab. Consequently, human adult stem cell culture in labs has been a truly impossible mission until now. Batlle’s team has also established the conditions for maintain living human colon stem cells (CoSCs) outside of the human body: “This is the first time that it has been possible to grow single CoSCs in lab-plates and to derive human intestinal stem cell lines in defined conditions in a lab setting,” explains the IRB Barcelona researcher Peter Jung, first author of the study together with Toshiro Sato, from the University Medical Center Utrecht in The Netherlands.
CoSCs renew the epithelium lining of the large intestine, and changes in these cells are believed to account for the pathophysiology of large-bowel disorders including colorectal cancer, the authors report. Unfortunately, scientists have to date been unable to isolate CoSCs. Drs. Battle et al.’s search for CoSCs in humans was founded on previous work indicating that mouse small intestinal stem cells (ICSs) and cancer stem cells express high amounts of EPHB2.
Building on this, the IRB-led team used an antibody against the EPHB2 extracellular domain to purify EPHB2-positive intestinal epithelial cells from histologically normal fresh tissue biopsied from patients with colorectal cancer or diverticulitis. From these sampless they isolated EpCAM+ crypt epithelial cell populations expressing various levels of surface EPHB2.
Further analysis of these cells showed that those with the lowest levels of surface EPHB2 expressed the highest levels of colonic differentiation markers. In addition, EPHB2-negative cells showed up to a 2,500% reduction in the expression of proliferation genes, “implying that this population was composed of cell cycle-arrested, terminally differentiated cells,” they note.
The researcher then subdivided EPHB2-expressing cells on the basis of expression levels of the marker. They found that EPHB2high cells had the longest average telomere length and expressed the highest levels of mouse ISC markers. Expression profiling studies showed that in EPHB2high cells there was a set of 90 genes including LGR5, ASCL2, and EPHB3 that was consistently expressed at higher levels in comparison with EPHB2medium cells.