Cell-matrix interface regulates dormancy in human colon cancer stem cells.

Cancer relapse after chemotherapy remains a main cause of cancer-related death. Although the relapse is thought to result from the propagation of resident cancer stem cells1, a lack of experimental platforms that enable the prospective analysis of cancer stem cell dynamics with sufficient spatiotemporal resolution has hindered the testing of this hypothesis. Here we develop a live genetic lineage-tracing system that allows the longitudinal tracking of individual cells in xenotransplanted human colorectal cancer organoids, and identify LGR5+ cancer stem cells that exhibit a dormant behaviour in a chemo-naive state. Dormant LGR5+ cells are marked by the expression of p27, and intravital imaging provides direct evidence of the persistence of LGR5+p27+ cells during chemotherapy, followed by clonal expansion. Transcriptome analysis reveals that COL17A1-a cell-adhesion molecule that strengthens hemidesmosomes-is upregulated in dormant LGR5+p27+ cells. Organoids in which COL17A1 is knocked out lose the dormant LGR5+p27+ subpopulation and become sensitive to chemotherapy, which suggests that the cell-matrix interface has a role in the maintenance of dormancy. Chemotherapy disrupts COL17A1 and breaks the dormancy in LGR5+p27+ cells through FAK-YAP activation. Abrogation of YAP signalling prevents chemoresistant cells from exiting dormancy and delays the regrowth of tumours, highlighting the therapeutic potential of YAP inhibition in preventing cancer relapse. These results offer a viable therapeutic approach to overcome the refractoriness of human colorectal cancer to conventional chemotherapy.

Ngn3-Positive Cells Arise from Pancreatic Duct Cells.

The production of pancreatic ß cells is the most challenging step for curing diabetes using next-generation treatments. Adult pancreatic endocrine cells are thought to be maintained by the self-duplication of differentiated cells, and pancreatic endocrine neogenesis can only be observed when the tissue is severely damaged. Experimentally, this can be performed using a method named partial duct ligation (PDL). As the success rate of PDL surgery is low because of difficulties in identifying the pancreatic duct, we previously proposed a method for fluorescently labeling the duct in live animals. Using this method, we performed PDL on neurogenin3 (Ngn3)-GFP transgenic mice to determine the origin of endocrine precursor cells and evaluate their potential to differentiate into multiple cell types. Ngn3-activated cells, which were marked with GFP, appeared after PDL operation. Because some GFP-positive cells were aligned proximally to the duct, we hypothesized that Ngn3-positive cells arise from the pancreatic duct. Therefore, we next developed an in vitro pancreatic duct culture system using Ngn3-GFP mice and examined whether Ngn3-positive cells emerge from this duct. We observed GFP expressions in ductal organoid cultures. GFP expressions were correlated with Ngn3 expressions and endocrine cell lineage markers. Interestingly, tuft cell markers were also correlated with GFP expressions. Our results demonstrate that in adult mice, Ngn3-positive endocrine precursor cells arise from the pancreatic ducts both in vivo and in vitro experiments indicating that the pancreatic duct could be a potential donor for therapeutic use.

Intestinal epithelial organoids: regeneration and maintenance of the intestinal epithelium.

Vital functions of the intestines: digestion, absorption, and surface barrier are performed by the intestinal epithelium, which consists of various differentiated cells and intestinal stem cells. Recent technological advances in sequencing technology, including single-cell transcriptomics and epigenetic analysis, have facilitated the genetic characterization of diverse intestinal epithelial cell types and surrounding mesenchymal niche environments. Organoids have allowed biological analysis of the human intestinal epithelium in coordination with genome engineering, genetic lineage tracing, and transplantation into orthotopic tissue. Together, these technologies have prompted the development of organoid-based regenerative therapies for intestinal diseases, including short-bowel syndrome. This article provides an overview of the current understanding of intestinal epithelial self-renewal during homeostasis and regeneration and provides a perspective for future organoid medicine.

Inhibition of the serotonin-induced inward current by dextromethorphan in rat nodose ganglion neurons.

Dextromethorphan is one of the most widely used antitussives for the treatment of cough. In the present study, we investigated the effect of dextromethorphan on 5-hydroxytryptamine (5-HT)-induced currents in acutely dissociated rat nodose ganglion neurons using nystatin-perforated patch-clamp recording configuration. The 5-HT-induced current was inhibited by the 5-HT(3) receptor antagonist tropisetron, while the selective 5-HT(3) receptor agonist 1-(m-chlorophenyl)-biguanide hydrochloride (mCPBG) induced a similar current. Dextromethorphan reversibly and concentration-dependently inhibited the 5-HT-induced inward current. The inhibition did not appear to be voltage-dependent. Both the peak and steady-state 5-HT-induced currents were inhibited by dextromethorphan, although the peak current was more sensitive to dextromethorphan block. The IC(50) values for the inhibition of peak and steady currents evoked by 3 muM 5-HT were 16.4 and 34.4 muM, respectively. In the presence of 10 muM dextromethorphan, the concentration-response curve for 5-HT was shifted to the right without changing the maximum response, while high concentrations reduced the maximum current. The 5-HT EC(50) values in the presence of 0, 10, 30 and 60 muM dextromethorphan were 4.3, 6.8, 15.5 and 40.6 muM, respectively. The results indicate that dextromethorphan inhibits the 5-HT-induced current of rat nodose ganglion neurons, and further suggest that dextromethorphan at a low concentration acts as a competitive inhibitor of 5-HT(3) receptors.