Age- and site-dependent cell cycle composition of the normal human colonic mucosa.

BACKGROUND AND AIM: As a reference to studies of DNA-ploidy and S- and G2/M-phase fractions in patients with inflammatory bowel diseases, we describe the mucosa of normal individuals with respect to age and localization in the colon.

MATERIALS AND

METHODS

One hundred and sixty-five biopsies from the right, transverse and left colon from 44 subjects (20 men, 24 females, median age 55 years (range 21-80)) who were referred for colonoscopy due to rectal bleeding, diarrhoea or suspicion of neoplasia, but with normal macroscopic and microscopic findings, were analysed by DNA-flow cytometry for ploidy and cell cycle composition. The biopsies were immediately fixed in buffered formalin and then analysed by a method for high quality preparations of cell nuclei without any centrifugation steps, resulting in minimal cell damage and low frequencies of aggregates, making the background levels low in the DNA-histograms.

RESULTS

The median S-phase fraction of the biopsies, all diploid, was 2.35% (0.1-8.3). The S-phase fraction increased linearly with age (p = 0.001) and decreased from the right colon (median 2.75% (0.5-8.3)) over the transverse colon (median 2.3% (0.1-6.2)) to the left colon (median 1.9% (0.8-6.5), p < 0.02). The fraction of G2-cells (median 1.1%, range 0.2-5.1) increased significantly with increased S-phase fraction (p < 0.0001).

CONCLUSION

DNA-FCM analyses of normal colonic tissue demonstrate an age- and site-dependent variation with regard to cell proliferation. This variation has to be taken into consideration when biopsy specimens from chronic colitis mucosa are evaluated.