Altered extracellular matrix expression in the diverted fetal sheep bladder.
OBJECTIVE
It is unclear whether filling and emptying are important to bladder development. We tested this in an experimental preparation.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Wei
Wenjie
W
Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Howard
Pamela S
PS
Kogan
Barry
B
Macarak
Edward J
EJ
D000818:Animals; D003094:Collagen / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism*; D047109:Fetal Development; D015870:Gene Expression; D019254:Genes, bcl-2; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D034561:Sheep, Domestic; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000196:embryology* / Q000378:metabolism; D014547:Urinary Diversion; D025721:WT1 Proteins / Q000378:metabolism
D051766:Early Growth Response Protein 1; D012333:RNA, Messenger; D025721:WT1 Proteins; D007334:Insulin-Like Growth Factor I; D003094:Collagen