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Published on: August 14, 2019
Temporal and spatial dimensions of postnatal growth of the mouse urinary bladder urothelium
Andreja Erman1, Gaj Vidmar, Kristijan Jezernik
1Institute of Cell Biology, Faculty of Medicine, Lipiceva 2, 1000 Ljubljana, Slovenia.
Insights
Mouse urothelium growth post-birth involves high cell proliferation rates, with distinct peaks. This growth primarily increases cell numbers within existing layers, not by adding new layers.
Area of Science:
- Urothelial biology
- Developmental biology
- Cell proliferation studies
Background:
- Postnatal development of the urothelium is crucial for urinary tract function.
- Understanding urothelial renewal informs tissue regeneration and disease research.
Purpose of the Study:
- To investigate the temporal and spatial patterns of mouse urothelial growth during the first two postnatal weeks.
- To quantify urothelial cell proliferation rates and mitotic activity in early life.
- To determine the contribution of cell layer expansion versus cell number increase to urothelial growth.
Main Methods:
- Quantitative analysis of urothelial cell proliferation rates.
- Semiquantitative analysis of cell division orientation (parallel vs. perpendicular to the urothelium).
- Microscopic examination of urothelial tissue from newborn to two-week-old mice.
Main Results:
- Urothelial cell proliferation is significantly higher in the first two postnatal weeks compared to adults.
- Three distinct peaks of proliferative and mitotic activity were observed: around birth/day 1, days 6-7, and day 14.
- High proliferation rates correlate with urothelial cell death around birth and on days 6-7.
- Proliferative response is mainly in the basal cell layer, with predominantly parallel cell division.
- Perpendicular cell division increased on the day of birth and postnatal day 7.
Conclusions:
- Postnatal mouse urothelial growth is characterized by heightened cell proliferation.
- Growth occurs primarily through an increase in cell numbers within existing layers, rather than the formation of new layers.
- Specific temporal patterns of proliferation and cell division orientation suggest dynamic developmental processes in the early postnatal period.
Abstract:
Postnatal growth and renewal of mouse urothelium start on the day of birth. In the present study, temporal and spatial dimensions of urothelial growth were studied during the first two postnatal weeks. Quantitative analysis showed that the rate of urothelial cell proliferation is significantly higher during all 14 postnatal days than in adult mice. Three peaks of proliferative and mitotic activity were revealed: on the day of birth and postnatal day 1, on days 6 and 7, and on day 14. The high proliferation rate around the day of birth and at postnatal days 6 and 7 coincides with cell death in the urothelium. Semiquantitative analysis showed that during all 14 postnatal days, the urothelial proliferative response is mostly confined to the basal cell layer. Urothelial cells divide predominantly in parallel to the plain of the urothelium on all chosen postnatal days. Increased portions of urothelial cells, dividing perpendicularly to the urothelium were observed only on the day of birth and on postnatal day 7. Our results suggest that postnatal growth of mouse urothelium is particularly the result of an increasing number of cells in individual cell layers and not the result of an increasing number of cell layers.
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