Stress urinary incontinence (SUI) is common in women after vaginal delivery (VD) in childbirth or pelvic trauma, and may be associated with altered biomechanical or functional properties of the urethra. The goal of this dissertation was to identify biomechanical and functional changes in the urethra in a rat model of VD, as well as to understand the role of longitudinal smooth muscle in the healthy urethra.
Female rat urethras were isolated in a rat model of SUI induced by VD. Controls were urethras isolated from normal rats. Our established ex vivo urethral testing system was utilized for biomechanical and pharmacological assessments. In this system, outer diameter was measured via a laser micrometer, and recorded along with applied intraluminal pressure to a computer. Urethral thickness was assessed histologically.
Biomechancial properties of the urethra were markedly altered by VD for the baseline, passive (via calcium chelation), and active (stimulation via adrenergic and muscarinic receptors) states, most notably in the proximal urethra. Additionally, contractile responses to phenylephrine and bethanechol increased in the proximal urethra in VD rats compared to controls. There were also changes in the VD mid urethral segment. Functional and biomechanical parameters indicated that basal activity was increased for VD compared to controls in the middle segment, as well as adrenergic active biomechanical properties at low strains. VD impaired the basal tone distally compared to controls, but this was the only difference observed.
VD urethras had evidence of altered collagen and elastin. Additionally, there was a lack of PGP 9.5, tyrosine hydroxylase, and vesicular acetylcholine transferase in the urethras of the VD group. This suggests that VD has mechanically damaging effects on urethral innervation.
Finally, the role of the longitudinal smooth muscle in the urethra was further clarified via a modified urethral testing system. Circumferential and longitudinal testing of baseline, active, and passive urethral properties and function supported the idea that the role of longitudinally-oriented components of the urethra was to lengthen or shorten to enable the circumferential muscle to fully contract and shorten as required.
In summary, this dissertation has provided evidence of damaged muscular, neural, and matrix components of the urethra associated with VD. The combination of these changes may contribute to SUI induced by VD.
|School:||University of Pittsburgh|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 68/10, Dissertation Abstracts International|
|Subjects:||Biomedical research, Anatomy & physiology|
|Keywords:||Biomechanical properties, Birth trauma, Ex vivo tissue, Smooth muscle, Stress urinary incontinence, Urethra, Urinary incontinence|
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