Age dependent apoptosis and loss of rhabdosphincter cells

Purpose: To our knowledge the exact age dependent morphological and functio nal changes of the sphincter mechanism have not been investigated. Therefor e, cell densities of the urethra and the urethral rhabdosphincter across va rious age groups, and the appearance of apoptosis were examined to explore the changes in these structures during the aging process. Materials and Methods: Specimens were obtained from 16 male and 7 female ca davers 5 weeks to 92 years old. Histological sections were taken from 3 dif ferent levels of the rhabdosphincter and urethra. The terminal deoxynucleot idyl transferase-mediated deoxyuridine triphosphate nick end-labeling metho d was used to detect apoptosis in the urethra and rhabdosphincter. In all s pecimens relative Volume densities of the striated muscle fibers, apoptotic indexes and diameters of the rhabdosphincter and urethra were determined. Results: An age dependent increase of apoptosis of the striated muscle fibe rs of the rhabdosphincter led to a dramatic decrease in the number of stria ted muscle cells. In the 5-week-old neonate 87.6% and in the gl-year-old wo man 34.2% of the rhabdosphincter consisted of striated muscle cells. Overal l, a direct linear correlation between the age of the specimens and decreas e in volume densities of the striated muscle cells was evident. Conclusions: The dramatic decrease in the number of striated muscle cells i n the rhabdosphincter of the elderly due to apoptosis represents the morpho logical basis for the high incidence of stress incontinence in this populat ion.