During the past 10 years, postoperative mortality associated with surgical treatment of oesophageal carcinoma has been reduced by one-half. However, it appears that all efforts to improve long-term survival with extensive excisional procedures and adjuvant chemotherapy and radiotherapy have failed. Fifty-six of 100 patients presenting to the surgeon with an oesophageal carcinoma have resectable disease. Recent studies suggest that seven of them will die from postoperative complications and 49 patients will be discharged from the hospital after an average of 3 weeks. Of these patients, 27 will survive the first, 12 the second, and ten the fifth year. Although it may be possible to further reduce postoperative complications and mortality, the chances of improving the long-term prognosis of patients with oesophageal carcinoma seem small.

Urea is the principal end product of nitrogen metabolism in mammals. Movement of urea across cell membranes was originally thought to occur by lipid-phase permeation, but recent studies have revealed the existence of specialized transporters with a low affinity for urea (Km > 200 mM)2. Here we report the isolation of a complementary DNA from rabbit renal medulla that encodes a 397-amino-acid membrane glycoprotein, UT2, with the functional characteristics of the vasopressin-sensitive urea transporter previously described in in vitro-perfused inner medullary collecting ducts. UT2 is not homologous to any known protein and displays a unique pattern of hydrophobicity. Because of the central role of this transporter in fluid balance and nitrogen metabolism, the study of this protein will provide important insights into the urinary concentrating mechanism and nitrogen balance.

BACKGROUND & AIMS Identification of intestinal stem cells (ISCs) has relied heavily on the use of transgenic reporters in mice, but this approach is limited by mosaic expression patterns and difficult to directly apply to human tissues. We sought to identify reliable surface markers of ISCs and establish a robust functional assay to characterize ISCs from mouse and human tissues. METHODS We used immunohistochemistry, real-time reverse-transcription polymerase chain reaction, and fluorescence-activated cell sorting (FACS) to analyze intestinal epithelial cells isolated from mouse and human intestinal tissues. We compared different combinations of surface markers among ISCs isolated based on expression of Lgr5–green fluorescent protein. We developed a culture protocol to facilitate the identification of functional ISCs from mice and then tested the assay with human intestinal crypts and putative ISCs. RESULTS CD44+CD24loCD166+ cells, isolated by FACS from mouse small intestine and colon, expressed high levels of stem cell–associated genes. Transit-amplifying cells and progenitor cells were then excluded based on expression of GRP78 or c-Kit. CD44+CD24loCD166+ GRP78lo/− putative stem cells from mouse small intestine included Lgr5-GFPhi and Lgr5-GFPmed/lo cells. Incubation of these cells with the GSK inhibitor CHIR99021 and the E-cadherin stabilizer Thiazovivin resulted in colony formation by 25% to 30% of single-sorted ISCs. CONCLUSIONS We developed a culture protocol to identify putative ISCs from mouse and human tissues based on cell surface markers. CD44+CD24loCD166+, GRP78lo/−, and c-Kit− facilitated identification of putative stem cells from the mouse small intestine and colon, respectively. CD44+CD24−/loCD166+ also identified putative human ISCs. These findings will facilitate functional studies of mouse and human ISCs.