Is cervical dilatation during parturition at term associated with apoptosis

Aims: Cellular turnover may be involved in remodeling of the cervix during parturition. Therefore, the number and localization of apoptotic and proliferating cells during cervical dilatation at term were determined. Methods: Biopsy specimens from the lower uterine segment of 36 women undergoing cesarean section with a cervical dilatation of <2 cm (n=10), 2-<4 cm (n=9), 4-6 cm (n=8), and 6 cm (n=9) were examined for nuclear fragmentation by the TUNEL assay, and for cell survival by the apoptosis-blocking bcl-2. Proliferation was marked by Ki-67, epithelial cells by cytokeratin and leukocytes by CD 45. For quantification of apoptotic and proliferating cells, eight random fields of each specimen stained for TUNEL or Ki-67 were blindly counted by two investigators. For statistical evaluation, 90% confidence intervals based on a Poisson distribution were used; groups with non-overlapping intervals were considered significantly different. Results: Apoptotic cells were found exclusively within the stromal compartment, while bcl-2 was expressed in epithelial cells and leukocytes. Proliferating cells were of stromal and epithelial origin. The number of apoptotic as well as proliferating cells ranged from 0 to 2 cells per high-power field (median number 0) in all groups. The confidence intervals were overlapping for all groups, showing no statistical difference between them. Conclusion: Apoptosis does not seem to play a decisive role in the process of cervical dilatation during parturition at term.