Changes in the proliferative activity of the sigmoid colon with aging in comparison with normal mucosa bordering adenocarcinomas

ABSTRACT

Epithelial lining of the crypts of the sigmoid colon is in continuous renewal and has a high proliferative activity and it is documented that the incidence of colon cancer increases with age. Therefore, the aim of this study was to investigate the changes in the proliferative activity of the normal sigmoid colon with aging and to compare it with that of the normal mucosa taken at least 10 cms from the edge of the adenocarcinoma lesions. This is study was done on twenty human subjects that were divided into 2 group GI aged 20-35 years aged GII aged 55-70 years. Each group was divided into 2 subgroups subgroups A where specimens were taken from colonoscopically normal individuals that also showed no microscopic abnormalities and subgroup B where specimens were taken from normal mucosa at least 10 cms from the edge of adenocarcinoma lesions. Proliferative activity was estimated using PCNA index and the apoptotic activity was estimated by examining the anti-apoptotic Bcl-2 protein expression. Restilts showed hyperplasia in the epithelial lining of the crypts of the aged sigmoid colon. There was a highly significant increase in the PCNA index and in the anti-apoptotic Bcl-2 protein expression with aging in normal human subjects. PCNA index was significantly higher in normal mucosa of adenocarcinoma patients than in mucosa of normal individuals of the same age group. There was a significant increase in the alcian blue positive acid mucins with aging with no detectable difference between mucosa of normal individuals and normal mucosa of adenocarcinoma patients of the same age group. It was concluded that there is enhanced proliferation and decreased apoptosis in the epithelial lining of the sigmoid colon with aging and these changes may be partly responsible for the increased rate of colon cancer with aging. Also, the normal mucosa in patients with adenocarcinoma has higher proliferative and less apoptotic activities than the mucosa of normal individuals