We report on an experimental study of the role of mode of delivery and pregnancy on the architecture of vaginal elastic fibers and vaginal vault elasticity in female Sprague-Dawley rats. In primiparous rats submitted to spontaneous or Cesarean delivery and virgin rats submitted to simulated delivery, the tortuosity of elastic fibers (defined as the ratio of length to end-to-end distance) was observed to decrease when measured two days to two weeks postpartum. In addition, the measured tortuosity of elastic fibers in multiparous rats was greater than that of virgin rats. The tortuosity of elastic fibers of all rats measured at two days postpartum were found to be similar to that of multiparous rats. At two weeks postpartum the measured tortuosity of vaginal elastic fibers was indistinguishable from virgin rats, regardless of the delivery method. Borrowing from the field of polymer physics, a model is suggested that connects elastic fiber tortuosity to the resulting tension under an applied stress; fibers having high tortuosity are expected to provide less structural support than more linear, low tortuosity fibers. To probe the macroscopic effects in elasticity due to architectural changes observed in elastic fibers, we have measured the stiffness of the vaginal vault in each cohort using a pressure-infusion system. The vaginal vault stiffness of all primiparous rats measured two weeks postpartum was greater than that measured two days postpartum. In addition, the vaginal vault of virgin rats was stiffer than that of multiparous rats. These observations confirmed that vaginal vault elastic fibers undergo significant remodeling due to pregnancy and parturition, and that the complex remodeling may be a significant contributor to tissue elasticity. Remarkably, regardless of the mode of delivery or simulated tissue trauma, elastic fiber tortuosity is observed to decrease from two days to two weeks postpartum indicating the onset of repair and recovery of tissue stiffness.

contractility studies, and for mRNA and protein analyses of major S1P/ROK pathway constituents via real-time polymerase chain reaction and Western blotting, respectively. In addition, early-passage SM cells were transfected with recombinant sphingosine kinase (SPHK, the enzyme that converts sphingosine to S1P). RESULTSBladders from PUO rats had greater mRNA expression of the S1P2 and S1P3 receptors, as well as SPHK1, than the sham controls (4.78, 2.04 and 2.72 times, respectively). PUO rats also had significantly greater expression of RhoA and ROK α (1.76 and 2.19 times, respectively). Western blotting and organbath contractility studies showed similar changes at the protein and in vitro functional level, with an increased contractility of bladder strips from PUO rats to exogenous S1P. Transfection of SPHK into isolated SM cells increased ROK expression. CONCLUSIONSWe show for the first time that the S1P signalling pathway is significantly upregulated in response to PUO in male rats at both the molecular and in vitro functional levels, correlating with an activation of the RhoA/ROK pathway. Further, we provide novel data that SPHK overexpression increases ROK expression in vitro , suggesting a novel hypothesis of S1P-induced bladder overactivity in the mechanism for PUOinduced bladder dysfunction and the S1P signalling pathway as a possible therapeutic target for bladder overactivity. KEYWORDSbladder, outlet obstruction, sphingosine-1-phosphate, Rho-kinase OBJECTIVESTo examine the effect of partial urethral obstruction (PUO) on the sphingosine-1-phosphate (S1P, a bioactive lipid shown to modulate smooth muscle, SM) pathway in the bladders of male rats, and to determine the effect of PUO on the RhoA/Rho-kinase (ROK) pathway, and whether there is a molecular cross-talk with the S1P pathways associated with bladder overactivity (S1P1-S1P3, where S1P1 is associated with nitric oxide-mediated SM relaxation, and S1P2 and S1P3 receptors are associated more with SM contraction via the ROK pathway). MATERIALS AND METHODSIn all, 20 male rats were divided into two groups and underwent PUO or a sham operation (control). After 2 weeks all rats were killed humanely and bladder specimens used for in vitro organ-bath physiological

The tissues and organs of the female reproductive tract and pelvic floor undergo significant remodeling and alterations to allow for fetal growth and birth. In this work, we report on a study of the alterations of murine reproductive tract collagen resulting from pregnancy and parturition by spectrophotometry, histology, and (13)C, (2)H nuclear magnetic resonance (NMR). Four different cohorts of rats were investigated that included virgin, multiparous, two- and fourteen-day postpartum primiparous rats. (13)C CPMAS NMR revealed small chemical shift differences across the cohorts. The measured H-C internuclear correlation times indicated differences in dynamics of some motifs. However, the dynamics of the major amino acids, e.g., Gly, remained unaltered with respect to parity. (2)H NMR relaxation measurements revealed an additional water reservoir in the postpartum and multiparous cohorts pointing to redistribution of water due to pregnancy and/or parturition. Spectrophotometric measurements indicated that the collagen content in virgin rats was highest. Histological analysis of the upper vaginal wall indicated a signature of collagen fiber dissociation with smooth muscle and a change in the density of collagen fibers in multiparous rats.

What ' s known on the subject? and What does the study add? Partial urethral obstruction (PUO), a common urologic pathology in men and children, can be associated with detrusor overactivity (DO), but the exact molecular mechanisms responsible for the altered contractile phenotypes have not been fully elucidated.Our study is the fi rst to determine by direct patch-clamp current measurement that PUO, to recapitulate many of the pathological characteristics of benign prostatic hyperplasia (BPH), is associated with an approximate 5-fold decrease in bladder myocyte Maxi-K channel activity. Similar to others we report a 40% decrease in Maxi-K α subunit expression which correlates with the observed decrease in Maxi-K activity, but uniquely as much as a 5-fold increase in expression of Maxi-K β subunit which we hypothesize may be a compensatory response. Based upon our previous fi nding of increased detrusor overactivity (DO) in similar male PUO rats, we suggest the Maxi-K channel as a therapeutic target to treat BPH associated lower urinary tract symptoms (LUTS). OBJECTIVES• To examine the effect of partial urethral obstruction (PUO) on bladder smooth muscle outward potassium current and the contribution of the large-conductance calcium-activated potassium (Maxi-K, BKCa) channel to this activity in smooth muscle cells isolated from bladders of sham-operated and PUO male rats using whole-cell patch clamp recording techniques.• To determine the effect of PUO on the expression of the Maxi-K channel α and β 1 subunits and in vitro detrusor contractility. MATERIALS AND METHODS• Twenty adult male Sprague -Dawley rats were divided equally into two groups and subjected to surgical ligation of the urethra (PUO) or sham surgery (SHAM).• After 2 weeks, the detrusors from PUO and SHAM rats were used for molecular analyses (mRNA and protein quantifi cation of Maxi-K subunits) or organ bath contractility studies, or myocytes were isolated for conventional whole-cell patch clamp analyses. RESULTS• PUO increased bladder mass 2.5-fold and detrusor strips exhibited a more tonic-type contraction and increased contractility compared with controls (SHAM).• Iberiotoxin (300 nM) sensitive Maxi-K channel current comprised about 40% of the outward whole-cell current in SHAM bladders but only about 8% in PUO bladders.• Expression of the α subunit of the Maxi-K channel was signifi cantly decreased ∼ 40% while the expression of the β 1 subunit was increased ∼ 2-fold at the mRNA level. The increase in β 1 expression was confi rmed by Western blotting. CONCLUSIONS• Our fi ndings show that obstruction of the rat bladder is associated with decreased Maxi-K channel activity of bladder smooth muscle cells, determined via direct current measurement.• Increased expression of the β 1 subunit points to a compensatory reaction to decreased Maxi-K channel activity.• Maxi-K channel openers or gene therapy may therefore provide therapeutic benefi t for the overactive bladder. KEYWORDSMaxi-K , BKCa , subunit , detrusor overactivity , benign prostatic hyperplasi...