RECONSTRUCTIVE UROLOGY

Gender Specific Chronological and Morphometric Sssessment of Fetal Bladder Wall Development
Koerner I, Deibl M, Oswald J, Schwentner C, Lunacek A, Fritsch H, Bartsch G, Radmayr C
Department of Pediatric Urology, Medical University of Innsbruck, Innsbruck, Austria
J Urol. 2006; 176: 2674-8

• Purpose: To enhance our understanding of sonographically visible alterations in bladder wall thickness, we delineated phenotypic changes occurring in developing smooth muscle cells of the fetal and postnatal bladder with respect to gender specific differences.
• Materials and Methods: Bladders of 30 male and 18 female fetuses and 4 stillborn infants were immunostained with an alpha-smooth muscle actin antibody. Morphological and morphometric assessment was performed with the assistance of an image analysis system.
• Results: Alpha-smooth muscle actin expression in fetal bladder wall was detectable at 9 weeks of gestation. Bladder wall thickness and mean profile area of smooth muscle bundles increased significantly with advancing gestation, mediated by linear growth patterns. Fetal bladder wall development occurred uniformly, unrelated to gender.
• Conclusions: Although the lower urinary tract emerges in a gender specific way, our results suggest that in normal fetal growth detrusor muscle formation proceeds independent of genital sex.
  
  
• Editorial Comment
  The current paper deals with histologic and morphometric assessment of 18 female and 30 male bladder specimens of human fetuses at 9 to 35 weeks of gestation. The findings underline the theory of those favoring a gender independent development of the lower urinary tract. At various times during fetal development no differences between male and female specimens of the muscular structure and configuration of the bladder was seen contrary to previous reports (1). Furthermore, the growth of the muscular bladder wall was linear with gestational age.
  This is a very elegant study with nice fetal specimens and reveals several interesting aspects. Apart from the main conclusions outlined above it was also interesting to see that the bladder seems to develop relatively late compared to the gut. At 9 weeks, only immature smooth muscle cells were observed in the bladder whereas the bowel already demonstrated clearly visible inner and outer muscular layers. In addition, smooth muscle cells developed first in the ventral portion of the bladder close to the dome. One may speculate that this has something to do with the umbilical vessels.
  Only through the development of the bladder the muscle bundles start to change there shape, direction and intermingling. Unfortunately we do not get any clue from this study when and how neural development starts.
  With studies like that we get important information for further tissue engineering of the urinary bladder. We suppose that at the time of in vitro cultivation intermingling and growth may not be our major goal but that we somehow have to have functional and growth stimulations at the time of implantation, which will bring our cultivated smooth muscle cells to a structure, which resembles the native bladder.

Reference
1. Avni EF, Schulman CC: The origin of vesico-ureteric reflux in male newborns: further evidence in favour of a transient fetal urethral obstruction. Br J Urol. 1996; 78: 454-9.

Dr. Arnulf Stenzl, Dr. Joerg Seibold,
Dr. Udo Nagele & Dr. Karl-Dietrich Sievert
Department of Urology
Eberhard-Karls-University Tuebingen
Tuebingen, Germany