Smooth muscle differentiation and cell turnover in mouse detrusor development.
OBJECTIVE
We systematically analyzed detrusor muscle differentiation in normal mice with a focus on cell turnover (proliferation and apoptosis) as well as on expression of the muscle specific proteins alpha-smooth muscle actin and desmin.


METHODS
The stages examined were embryonic days 14 and 18, and postnatal day 1 and week 6, representing a period spanning organ inception to postnatal maturity. Alpha-smooth muscle actin, desmin and proliferating cell nuclear antigen were assessed by immunohistochemical testing of whole bladders and Western blot analysis of dissected detrusor layers. Apoptosis was detected in tissue sections by end-labeling.


RESULTS
Alpha-smooth muscle actin was expressed by the detrusor layer throughout maturation with levels significantly increasing from embryonic days 14 to 18 and cytoplasmic staining gaining in uniformity postnatally. Desmin expression in the detrusor was insignificant at embryonic day 14 but increased progressively thereafter. Proliferating cell nuclear antigen expression in the detrusor was highest at organ inception and fell stepwise at each developmental stage with low levels postnatally. Apoptosis in the detrusor was only detected at embryonic day 14.


CONCLUSIONS
These results demonstrate that morphological growth of the mouse detrusor muscle is accompanied by complex serial changes in the expression of muscle specific proteins and in cell turnover. Strikingly, detrusor muscle cell differentiation and proliferation are inversely related. These detailed studies may serve as a comparison for future experiments involving aberrant mouse bladder development.
Smeulders
N
N
Nephro-Urology Unit, Institute of Child Health, University College London, London, United Kingdom.
Woolf
A S
AS
Wilcox
D T
DT
D000199:Actins / Q000032:analysis; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D003893:Desmin / Q000032:analysis; D051379:Mice; D009130:Muscle, Smooth / Q000166:cytology / Q000254:growth & development; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D001743:Urinary Bladder / Q000166:cytology* / Q000196:embryology / Q000254:growth & development*
D000199:Actins; D003893:Desmin; D018809:Proliferating Cell Nuclear Antigen