title: Cellular turnover of normal gastrointestinal epithelium assessed by changes in telomeric: total DNA signal ratios.
abstract: OBJECTIVE
  The reasons why different areas of gastrointestinal mucosa exhibit widely different rates of malignant change are still poorly understood. Malignancy rates rise markedly with age. We therefore hypothesised that rates of malignant change might correlate with rates of ageing as judged by stem cell turnover. Telomeric DNA is lost with each cell division and so acts as a measure of the number of cell divisions undergone by stem cells. We measured telomeric:total DNA signal ratios in normal gastric (Helicobacter pylori-positive and H. pylori-negative), duodenal and colonic mucosa to see whether ratios correlated with propensity to malignancy.
  
  
  METHODS
  Subjects undergoing diagnostic upper (n = 93) or lower (n = 45) gastrointestinal endoscopy, whose mucosa appeared macroscopically normal, sampled over a wide age range.
  
  
  METHODS
  DNA was extracted from paired blood and mucosal samples (colonic or gastric and duodenal). Telomere length was assessed by dot blot hybridisation with an oligonucleotide-containing telomeric sequence compared with the signal obtained from total genomic DNA. Helicobacter status was assessed by Campylobacter-like organism (CLO) test and serologically.
  
  
  RESULTS
  Telomeric signal ratios were scattered, but correlated within individuals. The ratios tended to decrease with age but the rates of decrease did not correlate with rates of malignant change. Gastric tissue had the shortest ratios and duodenal ratios decreased fastest.
  
  
  CONCLUSIONS
  The telomeric signal ratios did not suggest any obvious basis for differential rates of disease especially malignancy. Infection with H. pylori was not associated with lower gastric telomere ratios.
authors.affiliation: Department of Medicine and Therapeutics, Aberdeen University Medical School, Aberdeen, UK.
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Craig
authors.forename: Alastair
authors.initials: A
authors.lastname: McKinlay
authors.forename: Mark A
authors.initials: MA
authors.lastname: Vickers
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D002455:Cell Division; D003106:Colon; D004247:DNA / Q000032:analysis* / Q000097:blood; D004386:Duodenum; D005260:Female; D016481:Helicobacter Infections / Q000378:metabolism / Q000473:pathology; D016480:Helicobacter pylori; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D013270:Stomach; D016615:Telomere / Q000235:genetics* / Q000648:ultrastructure
chemical_list: D004247:DNA