Assessing the effects of transforming growth factor-beta1 on bladder smooth muscle cell phenotype. I. Modulation of in vitro contractility.
OBJECTIVE
Modulation of the bladder smooth muscle cell phenotype contributes to the resulting bladder dysfunction in many pathological bladder conditions. Transforming growth factor-beta1 is an important regulator of cellular phenotype in fibrotic diseases that has specific effects on bladder smooth muscle cells associated with phenotypic changes. We verified transforming growth factor-beta1 expression in neurogenic bladder tissue and investigated its effects on bladder smooth muscle cell collagen gel contraction.


METHODS
Transforming growth factor-beta1 immunostaining was performed on tissue sections from spinalized rats and quantified based on the ratio of fluorescence to total detrusor area. Rat bladder smooth muscle cells were seeded at different densities on anchored collagen gels and the effect of transforming growth factor-beta1 on contractility was assessed by measuring changes in the collagen gel area with time. Phenotypic changes induced by transforming growth factor-beta1 were detected by immunostaining for caldesmon and the specific isoform high molecular weight caldesmon.


RESULTS
Transforming growth factor-beta1 immunostaining revealed increased levels specifically in the detrusor of spinal cord injured rats. Rat bladder smooth muscle cell contraction increased with larger cell populations and was inhibited by transforming growth factor-beta1. Transforming growth factor-beta1 induced a decrease in high molecular weight caldesmon expression in bladder smooth muscle cells.


CONCLUSIONS
Increased transforming growth factor-beta1 expression in the detrusor of spinal cord injured rats implies up-regulation and localized signaling in response to injury. Bladder smooth muscle cells showed a loss of contractility in response to transforming growth factor-beta1 in all cell populations. A shift in phenotype was confirmed by high molecular weight caldesmon immunostaining. These results suggest that transforming growth factor-beta1 can modulate bladder smooth muscle cell function and may be a crucial regulator of bladder smooth muscle cell phenotype in pathological bladder conditions.
Parekh
Aron
A
Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15219, USA.
Long
Rebecca A
RA
Iannone
Elizabeth C
EC
Chancellor
Michael B
MB
Sacks
Michael S
MS
D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000096:biosynthesis; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D009119:Muscle Contraction / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000150:complications*; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis / Q000494:pharmacology*; D015854:Up-Regulation; D001743:Urinary Bladder / Q000187:drug effects / Q000473:pathology; D001750:Urinary Bladder, Neurogenic / Q000209:etiology / Q000473:pathology*
D002148:Calmodulin-Binding Proteins; D053773:Transforming Growth Factor beta1