Implications for bidirectional signaling between afferent nerves and urothelial cells-ICI-RS 2014

Effect of epidural analgesia on postpartum bladder sensation

INTRODUCTION

This study investigates the effects of epidural analgesia on postpartum urinary bladder sensation. Urinary retention and inability to void are well known side effects of epidural analgesia but the causes are unknown. The incidence of postpartum hypotonic bladder injury is increased in women receiving epidural analgesia during labour. We hypothesise that long-acting local anaesthetics used in epidural analgesia can impair bladder sensation and can lead to an increased risk of asymptomatic overdistension.

METHOD

Primiparous women between 38-42 weeks gestation who had received epidural analgesia prior to being in labour were recruited. The women were catheterised prior to insertion of the epidural to obtain baseline bladder sensation measurements of first sensation to void and maximum bladder capacity from cystometry. Women who delivered by spontaneous vaginal delivery were followed up. Postnatally, cystometry was repeated until bladder sensation returned to within 10 % of the pre-delivery volumes, bladders were not filled beyond 600 ml.

RESULTS

Sixty women were recruited prior to insertion of the epidural but only eighteen were studied postpartum as they had a spontaneous vaginal delivery. The mean time for cystometry values to return to pre-delivery levels was 6.6 h with a maximum duration of 8 h. The mean volume of urine produced before bladder sensation returned was 1054 ml.

CONCLUSION

Epidural analgesia delays the return of bladder sensation by up to 8-hours post-delivery. The volume of urine passed during this time can be as much as 1400 ml. Bladder catheterisation should be performed following epidural analgesia to minimise the possibility of bladder overdistension.

Activation of Piezo1 channels enhances spontaneous contractions of isolated human bladder strips via acetylcholine release from the mucosa

Enhanced spontaneous bladder contractions (SBCs) have been thought one of the important underlying mechanisms for detrusor overactivity (DO). Piezo1 channel has been demonstrated involved in bladder function and dysfunction in rodents. We aimed to investigate the modulating role of Piezo1 in SBCs activity of human bladder. Human bladder tissues were obtained from 24 organ donors. SBCs of isolated bladder strips were recorded in organ bath. Piezo1 expression was examined with reverse transcription-quantitative polymerase chain reaction and immunofluorescence staining. ATP and acetylcholine release in cultured human urothelial cells was measured. Piezo1 is abundantly expressed in the bladder mucosa. Activation of Piezo1 with its specific agonist Yoda1 (100 nM-100 μM) enhanced the SBCs activity in isolated human bladder strips in a concentration-dependent manner. The effect of Yoda1 mimicked the effect of a low concentration (30 nM) of carbachol, which can be attenuated by removing the mucosa, blocking muscarinic receptors with atropine (1 μM), and blocking purinergic receptors with pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS, 30 μM), but not by tetrodotoxin (1 μM). Activation of urothelial Piezo1 with Yoda1 (30 μM) or hypotonic solution induced the release of ATP and acetylcholine in cultured human urothelial cells. In patients with benign prostatic hyperplasia, greater Piezo1 expression was observed in bladder mucosa from patients with DO than patients without DO. We conclude that upregulation and activation of Piezo1 may contribute to DO generation in patients with bladder outlet obstruction by promoting the urothelial release of ATP and acetylcholine. Inhibition of Piezo1 may be a novel therapeutic approach in the treatment of overactive bladder.

Native tissue repair of cardinal/uterosacral ligaments cures overactive bladder and prolapse, but only in pre-menopausal women

INTRODUCTION

The aim of this article was to study the effect of native tissue cardinal/uterosacral ligament repair on overactive bladder (OAB) and pelvic organ prolapse (POP).

MATERIAL AND METHODS

Inclusion criteria included decrease of urge symptoms following insertion of a gauze tampon in the posterior fornix of vagina ('simulated operation'). Exclusion criteria included SUI, POP grades 3-4. The surgery consisted of plication of cardinal/uterosacral ligaments. Post-operative assessment was performed at3, 6, 12 and 18 months after surgery and included evaluation by stage of prolapse, Urinary Distress Inventory Short Form 6 (UDI-6), Overactive Bladder Questionnaire (OAB-q), Pelvic Floor Impact Questionnaire- Short Form 7 (PFIQ-7), and International Consultation on Incontinence Questionnaire - Urinary Incontinence Short Form (ICIQ-SF) questionnaires and voiding diary.

RESULTS

At 3 months, cure rates for frequency, urgency, nocturia and prolapse were comparable. By the 6-month review, catastrophic failure commenced in the postmenopausal group, parallel for all pa-rameters, starkly contrasting with premenopausal group. At 18 months, % cure rates for pre-menopausal (post-menopausal in brackets) were 79.6 (15.4) for POP, 67.3 (20.5) for urgency, 87.7 (20.5) for nocturia and 59.2 (15.4) for frequency.

CONCLUSIONS

We hypothesize the stepwise parallel recurrence of POP and symptoms in the menopausal group was a consequence of collagen deficiency in the plicated ligaments. Nevertheless, plication of uterosacral-cardinal ligament complex is simple, inexpensive, effective, especially applicable pre-menopausally for POP and as an alternative treatment option in that difficult group of pre-menopausal women who have major OAB/nocturia symptoms but only minimal prolapse.

The urethra in continence and sensation: Neural aspects of urethral function

AIMS

Traditionally, the urethra has been considered a mere conduit to guide urine from the bladder to the external side of the body. Building evidence indicates that the urethra may directly influence bladder function via mechanisms restricted to the lower urinary tract (LUT).

METHODS

Here, we discuss the tissue arrangement of the urethra and addressed the contribution of new paraneuronal cells to LUT function. We also briefly reviewed two frequent LUT pathologies associated with urethral dysfunction.

RESULTS

Continence depends on an intact and functional urethral sphincter, composed of smooth, and striated muscle fibers and regulated by somatic and autonomic fibers. Recent studies suggest the existence of an urethro-vesical reflex that also contributes to normal LUT function. Indeed, the urethral lumen is lined by a specialized epithelium, the urothelium, in the proximal urethra. In this region, recent evidence demonstrates the presence of specific paraneuronal cells, expressing the neurotransmitters acetylcholine and serotonin. These cells are in close proximity of nerve fibers coursing in the lamina propria and are able to release neurotransmitters and rapidly induce detrusor contractions, supporting the existence of an urethro-vesical crosstalk.

CONCLUSION

The mechanism underlying the fast communication between the urethra and thebladder are beginning to be understood and should involve the interaction between specificepithelial cells and fibres innervating the urethral wall. It is likely that this reflex should bealtered in pathological conditions, becoming an attractive therapeutic target.

Effects of intravesical prostaglandin E2 on bladder function are preserved in capsaicin-desensitized rats

Prostaglandin E2 (PGE2) instilled into the bladder generates symptoms of urinary urgency in healthy women and reduces bladder capacity and urethral pressure in both humans and female rats. Systemic capsaicin desensitization, which causes degeneration of C-fibers, prevented PGE2-mediated reductions in bladder capacity, suggesting that PGE2 acts as an irritant (Maggi CA, Giuliani S, Conte B, Furio M, Santicioli P, Meli P, Gragnani L, Meli A. Eur J Pharmacol 145: 105-112, 1988). In the present study, we instilled PGE2 in female rats after capsaicin desensitization but without the hypogastric nerve transection that was conducted in the Maggi et al. study. One week after capsaicin injection (125 mg/kg sc), rats underwent cystometric and urethral perfusion testing under urethane anesthesia with saline and 100 µM PGE2. Similar to naïve rats, capsaicin-desensitized rats exhibited a reduction in bladder capacity from 1.23 ± 0.08 mL to 0.70 ± 0.10 mL (P = 0.002, n = 9), a reduction in urethral perfusion pressure from 19.3 ± 2.1 cmH2O to 10.9 ± 1.2 cmH2O (P = 0.004, n = 9), and a reduction in bladder compliance from 0.13 ± 0.020 mL/cmH2O to 0.090 ± 0.014 mL/cmH2O (P = 0.011, n = 9). Thus, changes in bladder function following the instillation of PGE2 were not dependent on capsaicin-sensitive pathways. Further, these results suggest that urethral relaxation/weakness and/or increased detrusor pressure as a result of decreased compliance may contribute to urinary urgency and highlight potential targets for new therapies for overactive bladder.

Effect of Botulinum Toxin A on Bladder Pain-Molecular Evidence and Animal Studies

Botulinum toxin A (BTX-A) is a powerful neurotoxin with long-lasting activity that blocks muscle contractions. In addition to effects on neuromuscular junctions, BTX-A also plays a role in sensory feedback loops, suggesting the potentiality for pain relief. Although the only approved indications for BTX-A in the bladder are neurogenic detrusor overactivity and refractory overactive bladder, BTX-A injections to treat bladder pain refractory to conventional therapies are also recommended. The mechanism of BTX-A activity in bladder pain is complex, with several hypotheses proposed in recent studies. Here we comprehensively reviewed properties of BTX-A in peripheral afferent and efferent nerves, the inhibition of nociceptive neurotransmitter release, the reduction of stretch-related visceral pain, and its anti-inflammatory effects on the bladder urothelium. Studies have also revealed possible effects of BTX-A in the human brain. However, further basic and clinical studies are warranted to provide solid evidence-based support in using BTX-A to treat bladder pain.

The Botulinum Treatment of Neurogenic Detrusor Overactivity: The Double-Face of the Neurotoxin

Botulinum neurotoxin (BoNT) can counteract the highly frequent involuntary muscle contractions and the uncontrolled micturition events that characterize the neurogenic detrusor overactivity (NDO) due to supra-sacral spinal cord lesions. The ability of the toxin to block the neurotransmitter vesicular release causes the reduction of contractions and improves the compliance of the muscle and the bladder filling. BoNT is the second-choice treatment for NDO once the anti-muscarinic drugs have lost their effects. However, the toxin shows a time-dependent efficacy reduction up to a complete loss of activity. The cellular mechanisms responsible for BoNT effects exhaustion are not yet completely defined. Similarly, also the sites of its action are still under identification. A growing amount of data suggest that BoNT, beyond the effects on the efferent terminals, would act on the sensory system recently described in the bladder mucosa. The specimens from NDO patients no longer responding to BoNT treatment displayed a significant increase of the afferent terminals, likely excitatory, and signs of a chronic neurogenic inflammation in the mucosa. In summary, beyond the undoubted benefits in ameliorating the NDO symptomatology, BoNT treatment might bring to alterations in the bladder sensory system able to shorten its own effectiveness.

Spontaneous Activity and the Urinary Bladder

The urinary bladder has two functions: to store urine, when it is relaxed and highly compliant; and void its contents, when intravesical pressure rises due to co-ordinated contraction of detrusor smooth muscle in the bladder wall. Superimposed on this description are two observations: (1) the normal, relaxed bladder develops small transient increases of intravesical pressure, mirrored by local bladder wall movements; (2) pathological, larger pressure variations (detrusor overactivity) can occur that may cause involuntary urine loss and/or detrusor overactivity. Characterisation of these spontaneous contractions is important to understand: how normal bladder compliance is maintained during filling; and the pathophysiology of detrusor overactivity. Consideration of how spontaneous contractions originate should include the structural complexity of the bladder wall. Detrusor smooth muscle layer is overlain by a mucosa, itself a complex structure of urothelium and a lamina propria containing sensory nerves, micro-vasculature, interstitial cells and diffuse muscular elements.Several theories, not mutually exclusive, have been advanced for the origin of spontaneous contractions. These include intrinsic rhythmicity of detrusor muscle; modulation by non-muscular pacemaking cells in the bladder wall; motor input to detrusor by autonomic nerves; regulation of detrusor muscle excitability and contractility by the adjacent mucosa and spontaneous contraction of elements of the lamina propria. This chapter will consider evidence for each theory in both normal and overactive bladder and how their significance may vary during ageing and development. Further understanding of these mechanisms may also identify novel drug targets to ameliorate the clinical consequences of large contractions associated with detrusor overactivity.

The urinary microbiota: a paradigm shift for bladder disorders?

PURPOSE OF REVIEW

A resident microbial community [the female urinary microbiota (FUM)] exists within the female bladder of many adult women. Information about the FUM is likely to modify the diagnosis, prevention and treatment of adult women with urinary disorders. This review highlights key findings from recent literature relevant to adult, nonpregnant women.

RECENT FINDINGS

Similar to other human microbial communities, the FUM varies in its characteristics, including organism diversity and predominant organism identity. Recent literature reveals previously undetected organisms and community characteristics that appear associated with certain urinary symptoms, including urinary tract infection and urgency urinary incontinence. The role of individual organisms may range from beneficial to pathogenic and may vary on the basis of an individual's FUM characteristics. The simple dichotomy of 'infected' or 'sterile' no longer sufficiently captures the microbiological complexity of the female bladder.

SUMMARY

Deeper understanding of the FUM should yield better methods to restore the microbiota to a healthy state, providing symptom relief. Opportunities to modify the FUM without antibiotic use are exciting possibilities for future research; stand-alone antibiotic use may be reevaluated to improve treatment precision. Long-standing nomenclature for conditions such as asymptomatic bacteriuria and urinary tract infection will likely require modification.

What are the origins and relevance of spontaneous bladder contractions? ICI-RS 2017

INTRODUCTION

Storage phase bladder activity is a counter-intuitive observation of spontaneous contractions. They are potentially an intrinsic feature of the smooth muscle, but interstitial cells in the mucosa and the detrusor itself, as well as other muscular elements in the mucosa may substantially influence them. They are identified in several models explaining lower urinary tract dysfunction.

METHODS

A consensus meeting at the International Consultation on Incontinence Research Society (ICI-RS) 2017 congress considered the origins and relevance of spontaneous bladder contractions by debating which cell type(s) modulate bladder spontaneous activity, whether the methodologies are sufficiently robust, and implications for healthy and abnormal lower urinary tract function.

RESULTS

The identified research priorities reflect a wide range of unknown aspects. Cellular contributions to spontaneous contractions in detrusor smooth muscle are still uncertain. Accordingly, insight into the cellular physiology of the bladder wall, particularly smooth muscle cells, interstitial cells, and urothelium, remains important. Upstream influences, such as innervation, endocrine, and paracrine factors, are particularly important. The cellular interactions represent the key understanding to derive the integrative physiology of organ function, notably the nature of signalling between mucosa and detrusor layers. Indeed, it is still not clear to what extent spontaneous contractions generated in isolated preparations mirror their normal and pathological counterparts in the intact bladder. Improved models of how spontaneous contractions influence pressure generation and sensory nerve function are also needed.

CONCLUSIONS

Deriving approaches to robust evaluation of spontaneous contractions and their influences for experimental and clinical use could yield considerable progress in functional urology.

Urothelial bladder afferent neurons in the rat are anatomically and neurochemically distinct from non-urothelial afferents

There is mounting evidence underscoring a role for the urothelium in urinary bladder sensation. Previous functional studies have identified bladder primary afferents with mechanosensitive properties suggesting urothelial innervation and/or communication. The current study identifies a group of urothelium-innervating afferent neurons in rat, and characterizes and compares the properties of these and non-urothelial afferent neuron populations. Lumbosacral (LS) primary afferent neurons were retrogradely labeled using intraparenchymal (IPar) microinjection or intravesical (IVes) infusion of tracer into the bladder. Using these techniques, separate populations of neurons were differentiated by dorsal root ganglion (DRG) somata labeling and dye distribution within the bladder. IPar- and IVes-labeled neurons accounted for 85.0% and 14.4% of labeled L6-S1 neurons (P < .001), respectively, with only 0.6% of neurons labeled by both techniques. Following IVes labeling, dye was contained only within the periurothelial bladder region in contrast to non-urothelial distribution of dye after IPar labeling. Electrophysiological characterization by in situ patch-clamp recordings from whole-mount DRG preparations indicated no significant difference in passive or active membrane properties of IPar and IVes DRG neurons. However, calcium imaging of isolated neurons indicates that a greater proportion of IPar- than IVes-labeled neurons express functional TRPA1 (45.7% versus 25.6%, respectively; P < .05). This study demonstrates that two anatomically distinct groups of LS bladder afferents can be identified in rat. Further studies of urothelial afferents and the phenotypic differences between non-/urothelial afferents may have important implications for normal and pathophysiological bladder sensory processing.

Comparative study of the organisation and phenotypes of bladder interstitial cells in human, mouse and rat

With most research on interstitial cells (IC) in the bladder being conducted on animal models, it remains unclear whether all structural and functional data on IC from animal models can be translated to the human context. This prompted us to compare the structural and immunohistochemical properties of IC in bladders from mouse, rat and human. Tissue samples were obtained from the bladder dome and subsequently processed for immunohistochemistry and electron microscopy. The ultrastructural properties of IC were compared by means of electron microscopy and IC were additionally characterized with single/double immunohistochemistry/immunofluorescence. Our results reveal a similar organization of the IC network in the upper lamina propria (ULP), the deep lamina propria (DLP) and the detrusor muscle in human, rat and mouse bladders. Furthermore, despite several similarities in IC phenotypes, we also found several obvious inter-species differences in IC, especially in the ULP. Most remarkably in this respect, ULP IC in human bladder predominantly displayed a myoid phenotype with abundant presence of contractile micro-filaments, while those in rat and mouse bladders showed a fibroblast phenotype. In conclusion, the organization of ULP IC, DLP IC and detrusor IC is comparable in human, rat and mouse bladders, although several obvious inter-species differences in IC phenotypes were found. The present data show that translating research data on IC in laboratory animals to the human setting should be carried out with caution.

MicroRNAs as potential biomarkers to predict the risk of urinary retention following intradetrusor onabotulinumtoxin-A injection

AIMS

MicroRNAs (miRs) control post-transcriptional gene expression, and this is relevant in understanding better chronic diseases and treatment outcomes. The role of miRs in the pathology and treatment outcomes of overactive bladder (OAB) is unknown. In this study, we assessed the differential expression of miRs in OAB patients responding with either normal or elevated post-void residual volumes (PVRs) ≥200 mL following intradetrusor injection of onabotulinumtoxin-A (onaBoNT-A).

METHODS

Female OAB patients refractory to OAB drugs were consented for this study. Cystoscopic-guided punch bladder biopsy was obtained at the time of injection of onaBoNT-A 100 units. The expression of 13 miR species, selected for their known effect on neurotrophin expression and smooth muscle function, was measured. PVRs and urine nerve growth factor (NGF) levels were measured at baseline and at the follow-up visit.

RESULTS

Fourteen patients with mean age of 66 years were consented. Of these patients, nine maintained PVRs <200 mL after onaBoNT-A injection to comprise the low PVR group. The other five patients with PVRs ≥200 mL comprised the high PVR group. The expression of miR221 and miR125b was upregulated by 11- and 2-fold, respectively, in patients who responded with low PVRs after onaBoNT-A (P < 0.05). Urine NGF levels at baseline were not different between the two groups.

CONCLUSIONS

This study suggests that deficiency in the pretreatment expression of miR221 and miR125b may predispose OAB patients to high PVRs following intradetrusor onaBoNT-A. Additional studies are needed to better understand the role of miRs in OAB.