Real-time PCR of host DNA in feces to study differential exfoliation of colonocytes between rats and humans.
BACKGROUND
Colonic mucosa has a high turnover rate. At the end of their lifespan, colonocytes become senescent and die. Histological studies indicate that senescent colonocytes are shed (exfoliated) into the fecal stream in rats, but phagocytosed by mucosal macrophages in humans. We study whether quantification of host DNA in feces can be used as a non-invasive marker for this differential disposal of colonocytes.


METHODS
Selective primers and probes for the rat and human beta-globin genes were designed and used in real-time PCR reactions.


RESULTS
Host DNA was quantitatively extracted and detected in fecal samples of both species. Feces of rats fed a humanized diet contained approximately 100 microg rat DNA per g freeze-dried feces. In human feces, however, only 5 out of 12 samples contained detectable, though very low (less than 0.35 microg/g), levels of host DNA. This about 300-fold difference could not be attributed to differences in DNase activities in the fecal stream.


CONCLUSIONS
Our results indicate that there is considerable luminal shedding of senescent colonocytes in rats, whereas mucosal phagocytosis is the main route of colonocyte disposal in humans. Thus, real-time PCR of host DNA in feces can be applied as a non-invasive method for studying the differential exfoliation of colonocytes.
Van Lieshout
E M M
EM
Nutrition and Health Program, Wagenigen Center for Food Sciences/NIZO Food Research, 6710 BA Ede, The Netherlands.
Van Doesburg
W
W
Van der Meer
R
R
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology* / Q000502:physiology; D017931:DNA Primers / Q000032:analysis; D004195:Disease Models, Animal; D005243:Feces / Q000166:cytology*; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity
D017931:DNA Primers