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

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.

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.

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).

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.