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We sought to determine if bladder cycling is required for remodeling during fetal development.For this study 5 fetal sheep bladders were harvested after 2 weeks of urinary diversion, initiated at approximately 90 days of gestation. Six unoperated sheep bladders of approximately 105 days of gestational age were used as controls. Dividing cells and cells undergoing apoptosis were quantified by using Ki-67 antibody and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling) assay, respectively. In addition, expression of the antiapoptosis gene, Bcl2, and cell division control protein 42 were quantified by real-time polymerase chain reaction.The thickness of bladder tissue layers is dramatically altered as a consequence of urinary diversion (defunctionalization). The percentage of Ki-67 and TUNEL positive cells in control bladders was 5.8% and 47.1%, respectively. However, in diverted bladders apoptosis and cell mitosis were significantly decreased with essentially 0% of Ki-67 and TUNEL positive cells per microscope field in the mucosa and detrusor muscle layers. In addition, relative mRNA expression of antiapoptotic gene Bcl2 was significantly lower in control than in diverted bladder tissue, while Cdc42 was significantly higher in the detrusor but not in the lamina propria.Cell mitotic activity and coordinated cell death appear to be involved in growth and remodeling, which are activated by the mechanical input that occurs during bladder cycling. Fetal urinary diversion results in a repression of mitotic and apoptotic activity, limiting normal bladder growth and remodeling.

We evaluated and quantified the levels of sarcoglycans present in the detrusor muscle layer of rabbits with partial bladder outlet obstruction.Rabbits underwent surgery, as previously described, to partially obstruct the urethra. One, 3, 7 and 14 days after obstruction the detrusor muscle layer was dissected free of the remaining bladder tissue and extracted with detergent to isolate the transmembrane components of the dystroglycan-glycoprotein complex. Several components of the dystroglycan-glycoprotein complex were characterized and quantified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting.Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis several bands were noted on gels with a molecular weight (43 and 35 kDa, respectively) corresponding to beta and gamma-sarcoglycan. As obstruction progressed longitudinally, the levels of beta and gamma-sarcoglycan showed progressive decrease at the protein level with beta-sarcoglycan levels recovering at later time points. Bladders with a functional physiology that showed more advanced symptoms of dysfunction had a greater decrease in beta and gamma-sarcoglycan protein.The levels of beta and gamma-sarcoglycan progressively change with obstruction with greater changes occurring in the levels of gamma-sarcoglycan. It is likely that alterations in the dystroglycan-glycoprotein complex are responsible for some of the changes in muscle physiology that occur as a consequence of obstruction.

It is unclear whether filling and emptying are important to bladder development. We tested this in an experimental preparation.Urinary diversion was performed in 7 fetal lambs at 90 days of gestation and 6 unoperated fetal lambs served as controls. Transmural sections were analyzed for changes in tissue layer thickness and/or composition after 14 days of urinary diversion. Matrix mRNA levels (collagen I and III, and FN) as well as the cytokines/growth factors IGF-1, EGR-1, WT-1 and BCL-2 were quantified by real-time polymerase chain reaction. Hydroxyproline measurements of total collagen and collagen subtype quantification were done by enzyme-linked immunosorbent assay.Diverted fetal bladders showed a 27% and 57% decrease in mucosal and detrusor muscle layer thickness, respectively. In contrast, there was a 270% increase in serosal layer thickness in diverted bladders. The mRNA levels of COL1A1, COL3A1, IGF-1, EGR-1 and the anti-apoptotic gene BCL-2 were increased significantly in the serosal/detrusor layer of diverted bladders. In the mucosa levels of these mRNAs remained unchanged except for those of FN and WT-1, which were significantly decreased and increased, respectively. Total collagen, and type I and III collagen protein levels were significantly increased in diverted bladders.The lack of mechanical loading in diverted bladders leads to the arrest of detrusor smooth muscle growth, and concurrent fibrosis and thickening of the serosal layer. Changes in the levels of IGF-1, BCL-2 and EGR-1 likely have regulatory roles that affect the smooth muscle phenotype in the detrusor layer.