Analysis of Smooth Muscle and Collagen Subtypes in the Normal Newborn and Bladder Exstrophy Patient
Many patients who undergo newborn bladder exstrophy closure, subsequent epispadias repair and later bladder neck reconstruction become completely continent, yet complications can occur. After a successful initial exstrophy closure and later epispadias repair, some patients may fail to gain sufficient capacity for bladder neck reconstruction. Others may fail to gain satisfactory capacity and continence after bladder neck reconstruction. In an attempt to understand the pathogenesis of these failures, the authors first compared bladder biopsies from normal neonatal bladders to newborn exstrophy bladders.
Materials and Methods
Bladder biopsies were taken from midline of the bladder wall just above the base of the trigone in twelve newborn exstrophy patients and compared to bladder sections from nine expired neonates. All bladder specimens were stained with monoclonal antibodies against Types I, III or IV collagen. A subset were further stained with Masson’s Trichrome to define the extracellular matrix. All specimens were then analyzed using a color digital image analysis system.
On initial examination of the extracellular matrix, there was an increase in colla?gen:smooth muscle ratio from 0.38 in controls to 1.2 in newborn exstrophy patients. This ratio was composed of both an increase in collagen as well as a decrease in smooth muscle. The collagen component of the extracellular matrix was then further defined to quantitate how much of each collagen type (I, III & IV) was being deposited.
The authors then examined the ratio of collagen type to total collagen sampled. Compared to control bladders, there was not a statistical difference in the amount of types I or IV in the newborn exstrophy bladder at time of initial closure. Interestingly however, there was a three fold increase in type III collagen, from 0.14+/−.05 to 0.46 +/−0.2 (p≪0.001) in the neonatal control bladders vs. newborn exstrophy bladders, respectively.
This alteration in collagen makeup may represent an earlier developmental stage of the exstrophied bladder at birth which then remodels and changes after successful initial closure. Further studies are underway to examine the collagen composition of bladders at the time of bladder neck reconstruction and failed closures as well as those undergoing bladder augmentation.
KeywordsBladder Neck Bladder Smooth Muscle Exstrophy Bladder Bladder Biopsy Bladder Calculus
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