Contribution of pudendal nerve injury to stress urinary incontinence in a male rat model

Urinary incontinence is a common complication following radical prostatectomy, as the surgery disturbs critical anatomical structures. This study explored how pudendal nerve (PN) injury affects urinary continence in male rats. In an acute study, leak point pressure (LPP) and external urethral sphincter electromyography (EMG) were performed on six male rats with an intact urethra, the urethra exposed (UE), the PN exposed (NE), and after PN transection (PNT). In a chronic study, LPP and EMG were tested in 67 rats 4 days, 3 weeks, or 6 weeks after sham PN injury, PN crush (PNC), or PNT. Urethras were assessed histologically. Acute PNT caused a significant decrease in LPP and EMG amplitude and firing rate compared to other groups. PNC resulted in a significant reduction in LPP and EMG firing rate 4 days, 3 weeks, and 6 weeks later. EMG amplitude was also significantly reduced 4 days and 6 weeks after PNC. Neuromuscular junctions were less organized and less innervated after PNC or PNT at all timepoints compared to sham injured animals. Collagen infiltration was significantly increased after PNC and PNT compared to sham at all timepoints. This rat model could facilitate preclinical testing of neuroregenerative therapies for post-prostatectomy incontinence.

Wireless and Catheter-Free Bladder Pressure and Volume Sensor

Continuous monitoring of bladder activity during normal daily activities would improve clinical diagnostics and understanding of the mechanisms underlying bladder function, or help validate how differing neuromodulation strategies affect the bladder. This work describes a urological monitor of conscious activity (UroMOCA). The UroMOCA included a pressure sensor, urine impedance-sensing electrodes, and wireless battery recharge and data transmission circuitry. Components were assembled on a circuit board and encapsulated with an epoxy/silicone molded package that allowed Pt-Ir electrode feedthrough for urine contact. Packaged UroMOCAs measured 12 × 18 × 6 mm. UroMOCAs continuously transmitted data from all onboard sensors at 10 Hz at 30 cm range, and ran for up to 44 hours between wireless recharges. After in vitro calibration, implantations were performed in 11 animals. Animals carried the device for 28 days, enabling many observations of bladder behavior during natural, conscious behavior. In vivo testing confirmed the UroMOCA did not impact bladder function after a two-week healing period. Pressure data in vivo were highly correlated to a reference catheter used during an anesthetized follow-up. Static volume sensor data were less accurate, but demonstrated reliable detection of bladder volume decreases, and distinguished between voiding and non-voiding bladder events.

Is the time right for a new initiative in mathematical modeling of the lower urinary tract? ICI-RS 2023

INTRODUCTION

A session at the 2023 International Consultation on Incontinence - Research Society (ICI-RS) held in Bristol, UK, focused on the question: Is the time right for a new initiative in mathematical modeling of the lower urinary tract (LUT)? The LUT is a complex system, comprising various synergetic components (i.e., bladder, urethra, neural control), each with its own dynamic functioning and high interindividual variability. This has led to a variety of different types of models for different purposes, each with advantages and disadvantages.

METHODS

When addressing the LUT, the modeling approach should be selected and sized according to the specific purpose, the targeted level of detail, and the available computational resources. Four areas were selected as examples to discuss: utility of nomograms in clinical use, value of fluid mechanical modeling, applications of models to simplify urodynamics, and utility of statistical models.

RESULTS

A brief literature review is provided along with discussion of the merits of different types of models for different applications. Remaining research questions are provided.

CONCLUSIONS

Inadequacies in current (outdated) models of the LUT as well as recent advances in computing power (e.g., quantum computing) and methods (e.g., artificial intelligence/machine learning), would dictate that the answer is an emphatic "Yes, the time is right for a new initiative in mathematical modeling of the LUT."

Can we improve techniques and patients' selection for nerve stimulation suitable for lower urinary tract dysfunctions? ICI-RS 2023

AIMS

Lower urinary tract dysfunctions (LUTD) are very common and, importantly, affect patients' quality of life (QoL). LUTD can range from urinary retention to urgency incontinence and includes a variety of symptoms. Nerve stimulation (NS) is an accepted widespread treatment with documented success for LUTD and is used widely. The aim of this review is to report the results of the discussion about how to improve the outcomes of NS for LUTD treatment.

METHODS

During its 2023 meeting in Bristol, the International Consultation on Incontinence Research Society discussed a literature review, and there was an expert consensus discussion focused on the emerging awareness of NS suitable for LUTD.

RESULTS

The consensus discussed how to improve techniques and patients' selection in NS, and high-priority research questions were identified.

CONCLUSIONS

Technique improvement, device programming, and patient selection are the goals of the current approach to NS. The conditional nerve stimulation with minimally invasive wireless systems and tailored algorithms hold promise for improving NS for LUTD, particularly for patients with neurogenic bladder who represent the new extended population to be treated.

A Flexible Implant for Multi-Day Monitoring of Colon Segment Activity

Monitoring of colon activity is currently limited to tethered systems like anorectal manometry. These systems have significant drawbacks, but fundamentally limit the observation time of colon activity, reducing the likelihood of detecting specific clinical events. While significant technological advancement has been directed to mobile sensor capsules, this work describes the development and feasibility of a stationary sensor for describing the coordinated activity between neighboring segments of the colon. Unlike wireless capsules, this device remains in position and measures propagating pressure waves and impedances between colon segments to describe activity and motility. This low-power, flexible, wireless sensor-the colon monitor to capture activity (ColoMOCA) was validated in situ and in vivo over seven days of implantation. The ColoMOCA diameter was similar to common endoscopes to allow for minimally invasive diagnostic placement. The ColoMOCA included two pressure sensors, and three impedance-sensing electrodes arranged to describe the differential pressures and motility between adjacent colon segments. To prevent damage after placement in the colon, the ColoMOCA was fabricated with a flexible polyimide circuit board and a silicone rubber housing. The resulting device was highly flexible and suitable for surgical attachment to the colon wall. In vivo testing performed in eleven animals demonstrated suitability of both short term (less than 3 hours) and 7-day implantations. Data collected wirelessly from animal experiments demonstrated the ColoMOCA described colon activity similarly to wired catheters and allowed untethered, conscious monitoring of organ behavior.

First in Human Subjects Testing of the UroMonitor: A Catheter-free Wireless Ambulatory Bladder Pressure Monitor

PURPOSE

Urodynamics is the standard method of diagnosing bladder dysfunction, but involves catheters and retrograde bladder filling. With these artificial conditions, urodynamics cannot always reproduce patient complaints. We have developed a wireless, catheter-free intravesical pressure sensor, the UroMonitor, which enables catheter-free telemetric ambulatory bladder monitoring. The purpose of this study was twofold: to evaluate accuracy of UroMonitor pressure data, and assess safety and feasibility of use in humans.

MATERIALS AND METHODS

Eleven adult female patients undergoing urodynamics for overactive bladder symptoms were enrolled. After baseline urodynamics, the UroMonitor was transurethrally inserted into the bladder and position was confirmed cystoscopically. A second urodynamics was then performed with the UroMonitor simultaneously transmitting bladder pressure. Following removal of urodynamics catheters, the UroMonitor transmitted bladder pressure during ambulation and voiding in private. Visual analogue pain scales (0-5) were used to assess patient discomfort.

RESULTS

The UroMonitor did not significantly alter capacity, sensation, or flow during urodynamics. The UroMonitor was also easily inserted and removed in all subjects. The UroMonitor reproduced bladder pressure, capturing 98% (85/87) of voiding and nonvoiding urodynamic events. All subjects voided with only the UroMonitor in place with low post-void residual volume. Median ambulatory pain score with the UroMonitor was rated 0 (0-2). There were no post-procedural infections or changes to voiding behavior.

CONCLUSIONS

The UroMonitor is the first device to enable catheter-free telemetric ambulatory bladder pressure monitoring in humans. The UroMonitor appears safe and well tolerated, does not impede lower urinary tract function, and can reliably identify bladder events compared to urodynamics.

Effects of mesenchymal stem cells and heparan sulfate mimetics on urethral function and vaginal wall biomechanics in a simulated rat childbirth injury model

INTRODUCTION AND HYPOTHESIS

New treatments are needed for pelvic floor disorders. ReGeneraTing Agent® (RGTA®) is a promising regenerative therapy. Therefore, the objective of this study was to compare regenerative abilities of mesenchymal stem cells (MSCs) and RGTA® on regeneration after simulated childbirth injury in rats.

METHODS

Rats underwent pudendal nerve crush and vaginal distension (PNC+VD) or sham injury. Rats that underwent PNC+VD were treated intravenously with vehicle, MSCs or RGTA® 1 h, 7 days, and 14 days after surgery. Sham rats received 1 ml vehicle at all time points. After 21 days, urethral function and pudendal nerve function were tested. Vaginal tissues were harvested for biomechanical testing and histology. Biaxial testing was performed to measure tissue stiffness.

RESULTS

PNC+VD decreased urethral and pudendal nerve function compared with sham. Vaginal wall stiffness was significantly decreased in longitudinal and transverse tissue axes after PNC+VD compared with sham. MSC or RGTA® did not restore urethral or pudendal nerve function. However, MSC treatment resolved loss in vaginal wall stiffness in both tissue axes and improved collagen content within the vaginal wall. RGTA® treatment increased vaginal wall anisotropy by increasing relative stiffness in the longitudinal direction. PNC+VD (with vehicle or MSCs) enhanced elastogenesis, which was not observed after RGTA® treatment.

CONCLUSIONS

Treatment with MSCs facilitated recovery of vaginal wall biomechanical properties and connective tissue composition after PNC+VD, whereas treatment with RGTA® resulted in anisotropic biomechanical changes. This indicates that MSCs and RGTA® promote different aspects of vaginal tissue regeneration after simulated childbirth injury.

Assessing Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury: Animal Models in Preclinical Neuro-Urology Research

Neurogenic bladder dysfunction is a condition that affects both bladder storage and voiding function and remains one of the leading causes of morbidity after spinal cord injury (SCI). The vast majority of individuals with severe SCI develop neurogenic lower urinary tract dysfunction (NLUTD), with symptoms ranging from neurogenic detrusor overactivity, detrusor sphincter dyssynergia, or sphincter underactivity depending on the location and extent of the spinal lesion. Animal models are critical to our fundamental understanding of lower urinary tract function and its dysfunction after SCI, in addition to providing a platform for the assessment of potential therapies. Given the need to develop and evaluate novel assessment tools, as well as therapeutic approaches in animal models of SCI prior to human translation, urodynamics assessment techniques have been implemented to measure NLUTD function in a variety of animals, including rats, mice, cats, dogs and pigs. In this narrative review, we summarize the literature on the use of animal models for cystometry testing in the assessment of SCI-related NLUTD. We also discuss the advantages and disadvantages of various animal models, and opportunities for future research.

Brain-Derived Neurotrophic Factor Is Indispensable to Continence Recovery after a Dual Nerve and Muscle Childbirth Injury Model

In women, stress urinary incontinence (SUI), leakage of urine from increased abdominal pressure, is correlated with pudendal nerve (PN) injury during childbirth. Expression of brain-derived neurotrophic factor (BDNF) is dysregulated in a dual nerve and muscle injury model of childbirth. We aimed to use tyrosine kinase B (TrkB), the receptor of BDNF, to bind free BDNF and inhibit spontaneous regeneration in a rat model of SUI. We hypothesized that BDNF is essential for functional recovery from the dual nerve and muscle injuries that can lead to SUI. Female Sprague-Dawley rats underwent PN crush (PNC) and vaginal distension (VD) and were implanted with osmotic pumps containing saline (Injury) or TrkB (Injury + TrkB). Sham Injury rats received sham PNC + VD. Six weeks after injury, animals underwent leak-point-pressure (LPP) testing with simultaneous external urethral sphincter (EUS) electromyography recording. The urethra was dissected for histology and immunofluorescence. LPP after injury and TrkB was significantly decreased compared to Injury rats. TrkB treatment inhibited reinnervation of neuromuscular junctions in the EUS and promoted atrophy of the EUS. These results demonstrate that BDNF is essential to neuroregeneration and reinnervation of the EUS. Treatments aimed at increasing BDNF periurethrally could promote neuroregeneration to treat SUI.

The Effect of Dosing of Stromal Cell-Derived Factor 1 on Anal Sphincter Regeneration

Aim: The aim of this study is to investigate if a high dose of the stromal cell-derived factor-1 (SDF-1) plasmid improves outcome in a minipig model of chronic anal sphincter injury. Methods: Twenty-two female minipigs underwent excision of the posterior hemicircumference of the anal sphincter complex and were allowed to recover for 6 weeks. They were randomly allocated (n = 6) to receive either 5% dextrose (sham) or 2, 4, or 8 mg of SDF-1 plasmid at the defect site. Two control pigs received no surgery/treatment. Outcome measures included anal manometry at preinjury/pretreatment and 2, 4, and 8 weeks after treatment, recording the mean of eight pressure channels and the posterior channel alone, histopathology using Masson's trichrome, and immunohistochemistry using PGP9.5 for staining of neural structures, and CY3 staining for blood vessels. Data are expressed as mean ± standard error. Manometry analysis used two-way analysis of variance (ANOVA) followed by the Holm-Sidak test. Quantification of muscle/fibrosis was analyzed with a Kruskal-Wallis one-way ANOVA on ranks. Results: Posterior anal pressures were significantly decreased in sham treated animals compared with controls (p = 0.04). In contrast, mean anal pressures at the four time points were not significantly different between groups (p > 0.05). The defect area of the sham treated group showed irregular muscle bundles, while all three SDF-1 treatment groups show organized muscle bundles, with the most organization in the higher dose groups. Quantification of Masson-stained slides showed no statistically significant differences between groups, but did show increased muscle volume in the area of defect in the treatment groups compared with sham. PGP9.5 and CY3 staining showed increased fluorescence in the higher dose groups compared with sham treatment. Conclusion: A single higher dose of the plasmid encoding SDF-1 may increase muscle volume in the area of a chronic defect. Impact statement Fecal or bowel incontinence as a result of a torn anal sphincter complex remains undetected for many years. The resulting defect does not respond well to surgical repair. Regenerating the anal sphincter complex with functional muscle has been a long-term goal. Stem cells home to a site of a chronic injury and cause regeneration when a cell signaling mechanism is available. Stromal cell-derived factor-1 is one such cytokine that has been well researched by us and others to have this effect. It is easy to use clinically and has been used in other applications in humans and considered safe.

Potential role of oxidative stress in the pathogenesis of diabetic bladder dysfunction

Diabetes mellitus is a chronic metabolic disease, posing a considerable threat to global public health. Treating systemic comorbidities has been one of the greatest clinical challenges in the management of diabetes. Diabetic bladder dysfunction, characterized by detrusor overactivity during the early stage of the disease and detrusor underactivity during the late stage, is a common urological complication of diabetes. Oxidative stress is thought to trigger hyperglycaemia-dependent tissue damage in multiple organs; thus, a growing body of literature has suggested a possible link between functional changes in urothelium, muscle and the corresponding innervations. Improved understanding of the mechanisms of oxidative stress could lead to the development of novel therapeutics to restore the redox equilibrium and scavenge excessive free radicals to normalize bladder function in patients with diabetes.

Detrusor Pressure Estimation from Single-Channel Urodynamics

Urodynamics is the current gold-standard for diagnosing lower urinary tract dysfunction, but uses non-physiologically fast, retrograde cystometric filling to obtain a brief snapshot of bladder function. Ambulatory urodynamics allows physicians to evaluate bladder function during natural filling over longer periods of time, but artifacts generated from patient movement necessitate the use of an abdominal pressure sensor, which makes long-term monitoring and feedback for closed-loop treatment impractical. In this paper, we analyze the characteristics of single-channel bladder pressure signals from human and feline datasets, and present an algorithm designed to estimate detrusor pressure, which is useful for diagnosis and treatment. We utilize multiresolution analysis techniques to maximize the attenuation of probable abdominal pressure components in the vesical pressure signal. Results indicate a strong correlation, averaging 0.895 ± 0.121 (N = 40) and 0.812 ± 0.113 (N = 16) between the estimated detrusor pressure obtained by the proposed method and recorded urodynamic data from human and feline subjects, respectively. Clinical Relevance- This work establishes that signal pro-cessing techniques may be applied to vesical pressure alone to accurately reconstruct pressures generated independently by the detrusor muscle. This is relevant for emerging sensors that measure vesical pressure alone or for data analysis of bladder pressure in ambulatory subjects which contains significant abdominal pressure artifacts.

Brain-Derived Neurotrophic Factor Is an Important Therapeutic Factor in Mesenchymal Stem Cell Secretions for Treatment of Traumatic Peripheral Pelvic Injuries

Traumatic neuromuscular injury to the pudendal nerve and urethra during childbirth does not regenerate well and contributes to stress urinary incontinence in women. Mesenchymal stem cells (MSCs) can improve neuroregeneration via their secretions, or secretome, which includes brain-derived neurotrophic factor (BDNF). In this study, we investigated whether BDNF is a key factor in the secretome of MSCs for the facilitation of functional recovery following a dual simulated childbirth injury. BDNF knockdown (KD) MSCs were created using an anti-BDNF shRNA lentivirus vector. A scrambled sequence was used as a transduction control (scrambled). Cells were cultured for 24 h before media was concentrated 50x to create concentrated conditioned media (CCM) containing MSC secretome. CCM of unmanipulated MSCs was screened for high BDNF expression (high BDNF CCM). Concentrated control media (CM) was created by concentrating media not conditioned by cells. Female Sprague-Dawley rats underwent bilateral pudendal nerve crush and vaginal distension (Injury) or sham injury. One hour and 1 week after injury, sham injured rats received CM, and injured rats received CM, high BDNF CCM, KD CCM, or scrambled CCM (300 μl intraperitoneally). Three weeks after injury, rats underwent leak point pressure (LPP) and pudendal nerve sensory branch potential (PNSBP) recordings. The urethra and pudendal nerve were harvested for anatomical assessment. ANOVA followed by the Student-Newman-Keuls test determined significant differences between groups (p < 0.05). BDNF KD CCM had significantly decreased BDNF concentration compared to scrambled CCM, while the concentration in high BDNF CCM was significantly increased. LPP was significantly decreased in CM and KD CCM treated animals compared to sham injury, but not with scrambled or high BDNF CCM. PNSBP firing rate showed a significant decrease with CM treatment compared to sham injury. Neuromuscular junctions in the urethral sphincter in KD CCM, scrambled CCM, and high BDNF CCM were healthier than CM treated rats. While anatomical and nerve function tests demonstrate regeneration of the pudendal nerve with any CCM treatment, LPP results suggest it takes longer to recover continence with reduced BDNF in CCM. BDNF in MSC CCM is an important factor for the acceleration of recovery from a dual nerve and muscle injury.

Stromal cell derived factor 1 plasmid to regenerate the anal sphincters

The aim of this study was to evaluate regeneration of a chronic large anal sphincter defect in a pig model after treatment with a plasmid encoding Stromal Cell Derived Factor-1(SDF-1).

METHODS

Under ethics approved protocol 19 age/weight matched Sinclair mini-pigs were subjected to excision of the posterior 50% of anal sphincter muscle and left to recover for 6 weeks. They were randomly allocated to receive either saline treatment (Saline 1 ml, n = 5), 1 injection of SDF-1 plasmid 2 mg/ml (1 SDF-1, n = 9) or 2 injections of SDF-1, 2 mg/ml each at 2 weeks intervals (2 SDF-1, n = 5). Euthanasia occurred 8 weeks after the last treatment. In vivo outcomes included anal resting pressures done under anesthesia pre-injury, pre-injection and before euthanasia (8 weeks after treatment). Anal ultrasound was done pre injury and pre-euthanasia. Tissues were saved for histology and analyzed quantitatively. Two way ANOVA followed by Holm-Sidak test and one way ANOVA followed by the Tukey test were used for data analysis, p < 0.05 was regarded as significant.

RESULTS

Posterior anal pressures at the 3 time points were not significantly different in the saline group. In contrast, post-treatment pressures in the 1 SDF-1 group pressures were significantly higher than both pre-injury (p = 0.001) and pre-treatment time points (p = 0.003). At the post-treatment time point, both 1 SDF-1 (p = 0.01) and 2 SDF-1 (p = 0.01) groups had significantly higher mean pressures compared to the saline group. Histology showed distortion of normal anatomy with patchy regeneration in the control group while muscle was more organized in both treatment groups.

CONCLUSIONS

Eight weeks after a single or two doses of SDF-1injected into a chronic anal sphincter injury improved resting anal pressures and regenerated muscle in the entire defect. SDF-1 plasmid is effective in treating chronic defects of the anal sphincter in a large animal and could be clinically translated.

Mouse Knockout Models for Pelvic Organ Prolapse: a Systematic Review

INTRODUCTION AND HYPOTHESIS

Mouse knockout (KO) models of pelvic organ prolapse (POP) have contributed mechanistic evidence for the role of connective tissue defects, specifically impaired elastic matrix remodeling. Our objective was to summarize what mouse KO models for POP are available and what have we learned from these mouse models about the pathophysiological mechanisms of POP development.

METHODS

We conducted a systematic review and reported narrative findings according to PRISMA guidelines. Two independent reviewers searched PubMed, Scopus and Embase for relevant manuscripts and conference abstracts for the time frame of January 1, 2000, to March 31, 2021. Conference abstracts were limited to the past 5 years.

RESULTS

The search strategy resulted in 294 total titles. We ultimately included 25 articles and an additional 11 conference abstracts. Five KO models have been studied: Loxl1, Fbln5, Fbln3, Hoxa11 and Upii-sv40t. Loxl1 and Fbln5 KO models have provided the most reliable and predictable POP phenotype. Loxl1 KO mice develop POP primarily from failure to heal after giving birth, whereas Fbln5 KO mice develop POP with aging. These mouse KO models have been used for a wide variety of investigations including genetic pathways involved in development of POP, biomechanical properties of the pelvic floor, elastic fiber deposition, POP therapies and the pathophysiology associated with mesh complications.

CONCLUSIONS

Mouse KO models have proved to be a valuable tool in the study of specific genes and their role in the development and progression of POP. They may be useful to study POP treatments and POP complications.

Feasibility of Real-Time Conditional Sacral Neuromodulation Using Wireless Bladder Pressure Sensor

Continuous sacral neuromodulation (SNM) is used to treat overactive bladder, reducing urine leakage and increasing capacity. Conditional SNM applies stimulation in response to changing bladder conditions, and is an opportunity to study neuromodulation effects in various disease states. A key advantage of this approach is saving power consumed by stimulation pulses. This study demonstrated feasibility of automatically applying neuromodulation using a wireless bladder pressure sensor, a real-time control algorithm, and the Medtronic Summit™ RC+S neurostimulation research system. This study tested feasibility of four conditional SNM paradigms over five days in 4 female sheep. Primary outcomes assessed proof of concept of closed-loop system function. While the bladder pressure sensor correlated only weakly to simultaneous catheter-based pressure measurement (correlation 0.26-0.89, median r=0.52), the sensor and algorithm were accurate enough to automatically trigger SNM appropriately. The neurostimulator executed 98.5% of transmitted stimulation commands with a median latency of 72 ms (n=1,206), suggesting that rapid decision-making and control is feasible with this platform. On average, bladder capacity increased for continuous SNM and algorithm-controlled paradigms. Some animals responded more strongly to conditional SNM, suggesting that treatment could be individualized. Future research in conditional SNM may elucidate the physiologic underpinnings of differential response and enable clinical translation.

Elastin homeostasis is altered with pelvic organ prolapse in cultures of vaginal cells from a lysyl oxidase-like 1 knockout mouse model

Pelvic organ prolapse (POP) decreases quality of life for many women, but its pathophysiology is poorly understood. We have previously shown that Lysyl oxidase‐like 1 knockout (Loxl1 KO) mice reliably prolapse with age and increased parity, similar to women. Both this model and clinical studies also indicate that altered elastin metabolism in pelvic floor tissues plays a role in POP manifestation, although it is unknown if this is a cause or effect. Using Loxl1 KO mice, we investigated the effects of genetic absence of Loxl1, vaginal parity, and presence of POP on the expression of genes and proteins key to the production and regulation of elastic matrix. Cultured cells isolated from vaginal explants of mice were assayed with Fastin for elastic matrix, as well as RT‐PCR and Western blot for expression of genes and proteins important for elastin homeostasis. Elastin synthesis significantly decreased with absence of LOXL1 and increased with parity (p < .001), but not with POP. Cells from prolapsed mice expressed significantly decreased MMP‐2 (p < .05) and increased TIMP‐4 (p < .05). The results suggest changes to elastin structure rather than amounts in prolapsed mice as well as poor postpartum elastin turnover, resulting in accumulation of damaged elastic fibers leading to abnormal tropoelastin deposition. POP may thus, be the result of an inability to initiate the molecular mechanisms necessary to clear and replace damaged elastic matrix in pelvic floor tissues after vaginal birth.

Quantitative Morphometry of Elastic Fibers in Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is common among older women who have delivered children vaginally. While the pathophysiology is not fully delineated, POP can occur in part from insufficient repair of disrupted elastic matrix fibers. Quantification of structural changes to elastic fibers has not been described previously for POP. The goal of this paper is to present a validated technique for morphometric analysis of elastic fibers in vaginal tissue cultures from lysyl oxidase like-1 knock out (LOXL1 KO) mice with POP. The effect of LOXL1 KO, effect of POP, effect of culture, and effect of elastogenic treatment on the changes in elastin fiber characteristics were tested using vaginal tissues from wild type multiparous (WT), LOXL1 KO multiparous prolapsed (POP) and LOXL1 KO multiparous non-prolapsed (NP) mice. Our results show significantly higher mean aspect ratio, maximum diameter and perimeter length in POP compared to NP after 3 weeks of tissue culture. Further, treatment of POP tissues in culture with growth factors with previously documented elastogenic effects caused a significant increase in the mean area and perimeter length of elastic fibers. This technique thus appears to be useful in quantifying structural changes and can be used to assess the pathophysiology of POP and the effect of elastogenic treatments with potential for POP.

Characterization of Lower Urinary Tract Dysfunction after Thoracic Spinal Cord Injury in Yucatan Minipigs

There is an increasing need to develop approaches that will not only improve the clinical management of neurogenic lower urinary tract dysfunction (NLUTD) after spinal cord injury (SCI), but also advance therapeutic interventions aimed at recovering bladder function. Although pre-clinical research frequently employs rodent SCI models, large animals such as the pig may play an important translational role in facilitating the development of devices or treatments. Therefore, the objective of this study was to develop a urodynamics protocol to characterize NLUTD in a porcine model of SCI. An iterative process to develop the protocol to perform urodynamics in female Yucatan minipigs began with a group of spinally intact, anesthetized pigs. Subsequently, urodynamic studies were performed in a group of awake, lightly restrained pigs, before and after a contusion-compression SCI at the T2 or T9-T11 spinal cord level. Bladder tissue was obtained for histological analysis at the end of the study. All anesthetized pigs had bladders that were acontractile, which resulted in overflow incontinence once capacity was reached. Uninjured, conscious pigs demonstrated appropriate relaxation and contraction of the external urethral sphincter during the voiding phase. SCI pigs demonstrated neurogenic detrusor overactivity and a significantly elevated post-void residual volume. Relative to the control, SCI bladders were heavier and thicker. The developed urodynamics protocol allows for repetitive evaluation of lower urinary tract function in pigs at different time points post-SCI. This technique manifests the potential for using the pig as an intermediary, large animal model for translational studies in NLUTD.

Role of lysyl oxidase like 1 in regulation of postpartum connective tissue metabolism in the mouse vagina†

Pelvic organ prolapse (POP) in lysyl oxidase like-1 knockout (Loxl1 KO) mice occurs primarily in parous mice and is rare in nulliparous mice. We determined the effect of Loxl1 deficiency on postpartum regulation of connective tissue metabolism genes and degradative enzyme activity in the vagina at 20 days gestation or 4 h, 48 h, 7 days, 15 days, 25 days, 7 weeks, or 12 weeks postpartum. Nulliparous Loxl1 KO and wildtype (WT) mice aged 11, 18, or 23 weeks were controls. Gene expression and enzyme activity were assessed using real-time quantitative reverse transcription PCR and fluorescein conjugated gelatin zymography, respectively. Parity, but not aging, had a significant influence on gene expression both with time postpartum and between KO and WT mice. Mmp2, Timp1, Timp2, Timp3, Timp4, Col1a1, Col3a1, Acta2, and Bmp1 were differentially expressed between KO and WT mice. Correlational analysis of gene-gene pairs revealed 10 significant differences between parous KO and WT groups, 5 of which were due to lack of co-expression of Bmp1 in KO mice. The overall enzyme activity that could be attributed to MMPs was significantly higher in WT compared to KO mice both 25 days and 12 weeks postpartum, and MMP activity was significantly lower 15 days and 25 days postpartum compared to KO nulliparous controls, but not WT. These findings suggest that Loxl1 deficiency combined with parity has a significant impact on postpartum regulation of connective tissue metabolism, particularly as it relates to co-expression of Bmp1 and altered proteolytic activity.

Therapeutic potential of muscle growth promoters in a stress urinary incontinence model

Weakness of urinary sphincter and pelvic floor muscles can cause insufficient urethral closure and lead to stress urinary incontinence. Bimagrumab is a novel myostatin inhibitor that blocks activin type II receptors, inducing skeletal muscle hypertrophy and attenuating muscle weakness. β₂-Adrenergic agonists, such as 5-hydroxybenzothiazolone derivative (5-HOB) and clenbuterol, can enhance muscle growth. We hypothesized that promoting muscle growth would increase leak point pressure (LPP) by facilitating muscle recovery in a dual-injury (DI) stress urinary incontinence model. Rats underwent pudendal nerve crush (PNC) followed by vaginal distension (VD). One week after injury, each rat began subcutaneous (0.3 mL/rat) treatment daily in a blinded fashion with either bimagrumab (DI + Bim), clenbuterol (DI + Clen), 5-HOB (DI + 5-HOB), or PBS (DI + PBS). Sham-injured rats underwent sham PNC + VD and received PBS (sham + PBS). After 2 wk of treatment, rats were anesthetized for LPP and external urethral sphincter electromyography recordings. Hindlimb skeletal muscles and pelvic floor muscles were dissected and stained. At the end of 2 wk of treatment, all three treatment groups had a significant increase in body weight and individual muscle weight compared with both sham-treated and sham-injured rats. LPP in DI + Bim rats was significantly higher than LPP of DI + PBS and DI + Clen rats. There were more consistent urethral striated muscle fibers, elastin fibers in the urethra, and pelvic muscle recovery in DI + Bim rats compared with DI + PBS rats. In conclusion, bimagrumab was the most effective for increasing urethral pressure and continence by promoting injured external urethral sphincter and pelvic floor muscle recovery.

Advances in Ambulatory Urodynamics

PURPOSE OF REVIEW

This manuscript reviews recent technological advances in ambulatory urodynamics.

RECENT FINDINGS

Ambulatory urodynamics is currently recommended by the International Continence Society as a second-line diagnostic tool in patients with nondiagnostic traditional urodynamics. Novel techniques involving telemetric monitoring are in development, which utilize catheter-free wireless systems to address several recognized shortcomings of inoffice urodynamic studies. Current research in catheter-free bladder pressure measurements involves either an intravesical, intradetrusor, or transdetrusor approach. Real-time bladder volume estimation may be performed using ultrasonography, near-infrared spectroscopy, or bladder volume conductance measurement. Ambulatory urodynamics can measure bladder function in the "real world" setting, capturing physiological bladder filling and emptying and allowing patients to reproduce the activities that may trigger their symptoms. Telemetric devices being developed represent further advances in this field and focus upon improving diagnostic capabilities, evaluating patient response to treatment, and facilitating closed-loop bladder control with neuroprosthetic integration.

What developments are needed to achieve less-invasive urodynamics? ICI-RS 2019

AIMS

To assess the state of technologies for urodynamics that are less invasive than standard cystometry and pressure-flow studies and to suggest areas needing research to improve this.

METHODS

A summary of a Think Tank debate held at the 2019 meeting of the International Consultation on Incontinence Research Society is provided, with subsequent analysis by the authors. Less-invasive techniques were summarized, classified by method, and possible developments considered. Discussions and recommendations were summarized by the co-chairs and edited into the form of this paper by all authors.

RESULTS

There is a full spectrum of technologies available for less-invasive assessment, ranging from simple uroflowmetry through imaging techniques to emerging complex technologies. Less-invasive diagnostics will not necessarily need to replace diagnosis by, or even provide the same level of diagnostic accuracy as, invasive urodynamics. Rather than aiming for a technique that is merely less invasive, the priority is to develop methods that are either as accurate as current invasive methods, or spare patients from the necessity of invasive methods by improving early triaging.

CONCLUSIONS

Technologies offering less-invasive urodynamic measurement of specific elements of function can be potentially beneficial. Less-invasive techniques may sometimes be useful as an adjunct to invasive urodynamics. The potential for current less-invasive tests to completely replace invasive urodynamic testing is considered, however, to be low. Less-invasive techniques must, therefore, be tested as screening/triaging tools, with the aim to spare some patients from invasive urodynamics early in the treatment pathway.

Harnessing the mesenchymal stem cell secretome for regenerative urology

The extensive arsenal of bioactive molecules secreted by mesenchymal stem cells (MSCs), known as the secretome, has demonstrated considerable therapeutic benefit in regenerative medicine. Investigation into the therapeutic potential of the secretome has enabled researchers to replicate the anti-inflammatory, pro-angiogenic and trophic effects of stem cells without the need for the cells themselves. Furthermore, treatment with the MSC secretome could circumvent hurdles associated with cellular therapy, including oncogenic transformation, immunoreactivity and cost. Thus, a clear rationale exists for investigating the therapeutic potential of the MSC secretome in regenerative urology. Indeed, preclinical studies have demonstrated the therapeutic benefits of the MSC secretome in models of stress urinary incontinence, renal disease, bladder dysfunction and erectile dysfunction. However, the specific mechanisms underpinning therapeutic activity are unclear and require further research before clinical translation. Improvements in current proteomic methods used to characterize the secretome will be necessary to provide further insight into stem cells and their secretome in regenerative urology.

Multiple doses of stem cells maintain urethral function in a model of neuromuscular injury resulting in stress urinary incontinence

Stress urinary incontinence (SUI) is more prevalent among women who deliver vaginally than women who have had a cesarean section, suggesting that tissue repair after vaginal delivery is insufficient. A single dose of mesenchymal stem cells (MSCs) has been shown to partially restore urethral function in a model of SUI. The aim of the present study was to determine if increasing the number of doses of MSCs improves urethral and pudendal nerve function and anatomy. We hypothesized that increasing the number of MSC doses would accelerate recovery from SUI compared with vehicle treatment. Rats underwent pudendal nerve crush and vaginal distension or a sham injury and were treated intravenously with vehicle or one, two, or three doses of 2 × 10⁶ MSCs at 1 h, 7 days, and 14 days after injury. Urethral leak point pressure testing with simultaneous external urethral sphincter electromyography and pudendal nerve electroneurography were performed 21 days after injury, and the urethrovaginal complex and pudendal nerve were harvested for semiquantitative morphometry of the external urethral sphincter, urethral elastin, and pudendal nerve. Two and three doses of MSCs significantly improved peak pressure; however, a single dose of MSCs did not. Single, as well as repeated, MSC doses improved urethral integrity by restoring urethral connective tissue composition and neuromuscular structures. MSC treatment improved elastogenesis, prevented disruption of the external urethral sphincter, and enhanced pudendal nerve morphology. These results suggest that MSC therapy for postpartum incontinence and SUI can be enhanced with multiple doses.

Daily bilateral pudendal nerve electrical stimulation improves recovery from stress urinary incontinence

Stress urinary incontinence (SUI) in women is strongly associated with childbirth which injures the pudendal nerve (PN) and the external urethral sphincter (EUS) during delivery. Electrical stimulation (ES) can increase brain-derived neurotrophic factor (BDNF) expression in injured neurons, activate Schwann cells and promote neuroregeneration after nerve injury. The aim of this study was to determine if more frequent ES would increase recovery from SUI in a rat model. Forty female Sprague-Dawley rats underwent either sham injury or pudendal nerve crush (PNC) and vaginal distention (VD) to establish SUI. Immediately after injury, electrodes were implanted at the pudendal nerve bilaterally. Each injured animal underwent sham ES, twice per week ES (2/week), or daily ES of 1 h duration for two weeks. Urethral and nerve function were assessed with leak point pressure (LPP), EUS electromyography and pudendal nerve sensory branch potential (PNSBP) recordings two weeks after injury. LPP was significantly increased after daily ES compared to 2/week ES. EUS neuromuscular junction innervation was decreased after injury with sham ES, but improved after 2/week or daily ES. This study demonstrates that daily bilateral ES to the pudendal nerve can accelerate recovery from SUI. Daily ES improved urethral function more than 2/week ES.

Ambulatory urodynamic monitoring: state of the art and future directions

Urodynamic studies are a key component of the clinical evaluation of lower urinary tract dysfunction and include filling cystometry, pressure-flow studies, uroflowmetry, urethral function tests and electromyography. However, pitfalls of traditional urodynamics include physical and emotional discomfort, artificial test conditions with catheters and rapid retrograde filling of the bladder, which result in variable diagnostic accuracy. Ambulatory urodynamic monitoring (AUM) uses physiological anterograde filling and, therefore, offers a longer and more physiologically relevant evaluation. However, AUM methods rely on traditional catheters and pressure transducers and do not measure volume continuously, which is required to provide context for pressure changes. Novel telemetric AUM (TAUM) methods that use wireless, catheter-free, battery-powered devices to monitor bladder pressure and volume while patients carry out their daily activities are currently being investigated. TAUM devices under current development are innovating in the areas of remote monitoring, rechargeable energy sources, device deployment and retrieval and materials engineering to provide increased diagnostic accuracy and improved comfort for patients with incontinence or voiding dysfunction. These devices hold promise for improving the diagnosis and management of patients with lower urinary tract disorders.

Is submucosal bladder pressure monitoring feasible?

There has been recent interest in placing pressure-sensing elements beneath the bladder mucosa to facilitate chronic bladder pressure monitoring. Wired submucosal sensors with the wires passed through detrusor have been demonstrated in vivo, with limited chronic retention, potentially due to the cable tethering the detrusor. Published studies of submucosal implants have shown that high correlation coefficients between submucosal and lumen pressures can be obtained in caprine, feline, and canine models. We have developed a wireless pressure monitor and surgical technique for wireless submucosal implantation and present our initial chronic implantation study here. Pressure monitors were implanted (n = 6) in female calf models (n = 5). Five devices were implanted cystoscopically with a 25-French rigid cystoscope. One device was implanted suprapubically to test device retention with an intact mucosa. Wireless recordings during anesthetized cystometry simultaneous with catheter-based reference vesical pressure measurements during filling and manual bladder compressions were recorded. Individual analysis of normalised data during bladder compressions (n = 12) indicated high correlation (r = 0.85-0.94) between submucosal and reference vesical pressure. The healing response was robust over 4 weeks; however, mucosal erosion occurred 2-4 weeks after implantation, leading to device migration into the bladder lumen and expulsion during urination. Wireless pressure monitors may be successfully placed in a suburothelial position. Submucosal pressures are correlated with vesical pressure, but may differ due to biomechanical forces pressing on an implanted sensor. Fully wireless devices implanted beneath the mucosa have risk of erosion through the mucosa, potentially caused by disruption of blood flow to the urothelium, or an as-yet unstudied mechanism of submucosal regrowth. Further investigation into device miniaturisation, anchoring methods, and understanding of submucosal pressure biomechanics may enable chronic submucosal pressure monitoring. However, the risk of erosion with submucosal implantation highlights the need for investigation of devices designed for chronic intravesical pressure monitoring.

Stenosis Characterization and Identification for Dialysis Vascular Access

Vascular access dysfunction is the leading cause of hospitalization for hemodialysis patients and accounts for the most medical costs in this patient population. Vascular access flow is commonly hindered by blood vessel narrowing (stenosis). Current screening methods involving imaging to detect stenosis are too costly for routine use at the point of care. Noninvasive, real-time screening of patients at risk of vascular access dysfunction could potentially identify high-risk patients and reduce the likelihood of emergency surgical interventions. Bruits (sounds produced by turbulent blood flow near stenoses) can be interpreted by skilled clinical staff using conventional stethoscopes. To improve the sensitivity of detection, digital analysis of blood flow sounds (phonoangiograms or PAGs) is a promising approach for classifying vascular access stenosis using non-invasive auditory recordings. Here, we demonstrate auditory and spectral features of PAGs which estimate both the location and degree of stenosis (DOS). Auditory recordings from nine stenosis phantoms with variable DOS and hemodynamic flow rate were obtained using a digital recording stethoscope and analyzed to extract classification features. Autoregressive modeling and discrete wavelet transforms were used for multiresolution signal decomposition to produce 14 distinct features, most of which were linearly correlated with DOS. Our initial results suggest that the widely-used auditory spectral centroid is a simple way to calculate features which can estimate both the location and severity of vascular access stenosis.

A Conductance-Based Sensor to Estimate Bladder Volume in Felines

New research tools are essential to help understand the neural control of the lower urinary tract (LUT). A more nuanced understanding of the neuroanatomy of bladder function could enable new treatment options or neuroprosthesis to eliminate incontinence. Here we describe the design, prototyping and validation of a sensing mechanism for a catheter-free fluid volume estimating system for chronic neurophysiological studies of the lower urinary tract and ambulatory urodynamics. The system consists of two stimulation electrodes, one sensing anode, and a microcontroller for control and recording. The packaged device is small enough to be surgically implanted within the bladder lumen, where it does not inhibit bladder function nor inflict trauma. Benchtop evaluation of the conductance-sensing system in simulated bladder-like conditions has demonstrated that the system can predict intra-vesical fluid volume with $< 5$ mL mean error below 40mL and worst-case mean error of 13mL near full-scale volume. These results indicate that conductance-based volume sensing of the urinary bladder is a feasible method for real-time measurement.

Bruit-enhancing phonoangiogram filter using sub-band autoregressive linear predictive coding

Subjective analysis of bruits has long been an element of vascular access physical exams. Digital recordings of blood flow bruits-phonoangiograms (PAGs)-may provide an objective, non-imaging measure of vascular access stenosis. We have analyzed the long-term stability in PAGs from typical dialysis patients with arteriovenous fistulas and grafts and found that typical patients have correlated PAG spectra. PAGs can be analyzed using nonlinear, sub-band frequency-domain linear prediction to produce both bruit-enhanced recordings and a bruit-enhanced power envelope. This approach is novel over prior methods because it adaptively predicts signal envelopes based on physiologic properties of blood flow determined from chronic dialysis recipients. Our results indicate that a generalized bruit-enhancing filter can be developed for dialysis vascular access. Outputs from this filter may be analyzed to determine vascular physiology, including re-stenosis risk.

Sex differences in lower urinary tract biology and physiology

Females and males differ significantly in gross anatomy and physiology of the lower urinary tract, and these differences are commonly discussed in the medical and scientific literature. However, less attention is dedicated to investigating the varied development, function, and biology between females and males on a cellular level. Recognizing that cell biology is not uniform, especially in the lower urinary tract of females and males, is crucial for providing context and relevance for diverse fields of biomedical investigation. This review serves to characterize the current understanding of biological sex differences between female and male lower urinary tracts, while identifying areas for future research. First, the differences in overall cell populations are discussed in the detrusor smooth muscle, urothelium, and trigone. Second, the urethra is discussed, including anatomic discussions of the female and male urethra followed by discussions of cellular differences in the urothelial and muscular layers. The pelvic floor is then reviewed, followed by an examination of the sex differences in hormonal regulation, the urinary tract microbiome, and the reticuloendothelial system. Understanding the complex and dynamic development, anatomy, and physiology of the lower urinary tract should be contextualized by the sex differences described in this review.

Low-cost, Implantable Wireless Sensor Platform for Neuromodulation Research

The role of peripheral nerves in regulating major organ function in health and disease is not well understood. Elucidating the relationships between biomarkers and neural activity during conditions free form anesthesia is essential to advancing future investigations of autonomic organ control and improving precision for neuromodulation treatment approaches. Here we present a simple, customizable, off-the-shelf component sensor platform to meet research needs for studying different organs under conscious, free movement. The platform consists of a small, rechargeable coin-cell battery, an energy-harvesting IC, a low-power microcontroller, a low-power pressure transducer, customizable number of electrodes with a common anode, inductive recharge input, and OOK inductive transmission. A case study demonstrating a bladder implant for long-term monitoring is presented, utilizing a novel, non-hermetic encapsulation approach. The customized platform uses two sleep modes to minimize battery loading, exhibiting a maximum time-averaged current draw of 125 micro-amps during sensing and transmission, with a quiescent current draw of 95 nano-amps into the microcontroller.

Electrical stimulation of the pudendal nerve promotes neuroregeneration and functional recovery from stress urinary incontinence in a rat model

The pudendal nerve can be injured during vaginal delivery of children, and slowed pudendal nerve regeneration has been correlated with development of stress urinary incontinence (SUI). Simultaneous injury to the pudendal nerve and its target muscle, the external urethral sphincter (EUS), during delivery likely leads to slowed neuroregeneration. The goal of this study was to determine if repeat electrical stimulation of the pudendal nerve improves SUI recovery and promotes neuroregeneration in a dual muscle and nerve injury rat model of SUI. Rats received electrical stimulation or sham stimulation of the pudendal nerve twice weekly for up to 2 wk after injury. A separate cohort of rats received sham injury and sham stimulation. Expression of brain-derived neurotrophic factor (BDNF) and β_II-tubulin expression in Onuf's nucleus were measured 2, 7, and 14 days after injury. Urodynamics, leak point pressure (LPP), and EUS electromyography (EMG) were recorded 14 days after injury. Electrical stimulation significantly increased expression of BDNF at all time points and β_II-tubulin 1 and 2 wk after injury. Two weeks after injury, LPP and EUS EMG during voiding and LPP testing were significantly decreased compared with sham-injured animals. Electrical stimulation significantly increased EUS activity during voiding, although LPP did not fully recover. Repeat pudendal nerve stimulation promotes neuromuscular continence mechanism recovery possibly via a neuroregenerative response through BDNF upregulation in the pudendal motoneurons in this model of SUI. Electrical stimulation of the pudendal nerve may therefore improve recovery after childbirth and ameliorate symptoms of SUI by promoting neuroregeneration after injury.

Sensors Selection for Continuous Monitoring of Bowel State and Activity

New research and diagnosis tools are needed to continuously measure bowel state and activity. We investigated functionality of several sensors in vivo and in vitro. Five sensor types, including pressure, infrared, color, conductivity and capacitance, were tested to validate functionality inside the colon. Initial wired prototypes were tested and calibrated in benchtop testing and then inserted intraluminally into pig colon and rectum in three acute surgical procedures. The results from both benchtop and in-vivo testing correlate and indicate that pressure, conductivity, and capacitance measurements could provide information on the state of the bowel and its activity.

Stem Cells for Urinary Incontinence: Functional Differentiation or Cytokine Effects?

Minimally invasive stem cell therapy for stress urinary incontinence may provide an effective nonsurgical treatment for this common condition. Clinical trials of periurethral stem cell injection have been under way, and basic science research has demonstrated the efficacy of both local and systemic stem cell therapies. Results differ as to whether stem cells have a therapeutic effect by differentiating into permanent, functional tissues or exert benefits through a transient presence and the secretion of regenerative factors. This review explores the fate of therapeutic stem cells for stress urinary incontinence and how this may relate to their mechanism of action.

Tunable and Lightweight On-Chip Event Detection for Implantable Bladder Pressure Monitoring Devices

Lower urinary tract dysfunctions, such as urinary incontinence and overactive bladder, are conditions that greatly affect the quality of life for millions of individuals worldwide. For those with more complex pathophysiologies, diagnosis of these conditions often requires a urodynamics study, providing physicians with a snapshot view of bladder mechanics. Recent advancements in implantable bladder pressure monitors and advanced data analysis techniques have made diagnosis through chronic monitoring a promising prospect. However, implants targeted at treatment must remain in the bladder for long periods of time, making minimizing power consumption a primary design objective. Currently, much of the typical implant's power draw is due to data transmission. Previous work has demonstrated an adaptive rate transmission technique to reduce power consumption. However, the ultimate reduction in power consumption can only be attained when the device does not transmit bladder pressure samples, but rather bladder events. In this paper, we present an algorithm and circuit level implementation for on-chip bladder pressure data compression and event detection. It is designed to be a complete, tunable, and lightweight diagnosis and treatment framework for bladder pressure monitoring implants, capable of selectively transmitting compressed bladder pressure data with tunable quality, "snapshots" of significant bladder events, or simply indicate events occurred for the highest energy efficiency. The design aims to minimize area through resource reuse, leading to a total area of 1.75 , and employs advanced VLSI techniques for power reduction. With compression and event detection enabled, the design consumes roughly 2.6 nW in TSMC technology. With only event detection, this reduces to 2.1 nW, making this approach ideal for long-life implantable bladder pressure monitoring devices.

Controlled release of insulin-like growth factor 1 enhances urethral sphincter function and histological structure in the treatment of female stress urinary incontinence in a rat model

OBJECTIVES

To determine the effects of controlled release of insulin-like growth factor 1 (IGF-1) from alginate-poly-L-ornithine-gelatine (A-PLO-G) microbeads on external urethral sphincter (EUS) tissue regeneration in a rat model of stress urinary incontinence (SUI), as SUI diminishes the quality of life of millions, particularly women who have delivered vaginally, which can injure the urethral sphincter. Despite several well-established treatments for SUI, growth factor therapy might provide an alternative to promote urethral sphincter repair.

MATERIALS AND METHODS

In all, 44 female Sprague-Dawley rats were randomised into four groups: vaginal distension (VD) followed by periurethral injection of IGF-1-A-PLO-G microbeads (VD + IGF-1 microbeads; 1 × 10⁴ microbeads/1 mL normal saline); VD + empty microbeads; VD + saline; or sham-VD + saline (sham).

RESULTS

Urethral function (leak-point pressure, LPP) was significantly lesser 1 week after VD + saline [mean (sem) 23.9 (1.3) cmH₂ O] or VD + empty microbeads [mean (sem) 21.7 (0.8) cmH₂ O) compared to the sham group [mean (sem) 44.4 (3.4) cmH₂ O; P < 0.05), indicating that the microbeads themselves do not create a bulking or obstructive effect in the urethra. The LPP was significantly higher 1 week after VD + IGF-1 microbeads [mean (sem) 28.4 (1.2) cmH₂ O] compared to VD + empty microbeads (P < 0.05), and was not significantly different from the LPP in sham rats, demonstrating an initiation of a reparative effect even at 1 week after VD. Histological analysis showed well-organised skeletal muscle fibres and vascular development in the EUS at 1 week after VD + IGF-1 microbeads, compared to substantial muscle fibre attenuation and disorganisation, and less vascular formation at 1 week after VD + saline or VD + empty microbeads.

CONCLUSION

Periurethral administration of IGF-1-A-PLO-G microbeads facilitates recovery from SUI by promoting skeletal myogenesis and revascularisation. This therapy is promising, but detailed and longer term studies in animal models and humans are needed.

Real-time, autonomous bladder event classification and closed-loop control from single-channel pressure data

Urinary incontinence, or the loss of bladder control, is a debilitating condition affecting millions worldwide, which significantly reduces quality of life. Neuromodulation of lower urinary tract nerves can be used to treat sensations of urgency in many subjects, including those with Spinal Cord Injury (SCI). Event driven, or conditional stimulation has been investigated as a possible improvement to the state-of-the-art open-loop stimulation systems available today. However, this requires a robust, adaptive, and noise-tolerant method of classifying bladder function from real-time bladder pressure measurements. Context-Aware Thresholding (CAT) has been previously shown to work well on prerecorded single contraction urodynamic data. In this work, for the first time, we present real-time detection of multiple serial bladder contractions using urodynamic recordings from human subjects with SCI and Neurogenic Detrusor Overactivity (NDO). CAT demonstrated a high degree of accuracy and noise tolerance on prerecorded data from 15 human subjects, with a mean accuracy of 92% and average false positive rate of 0.3 false positives per contraction. Analysis of event detection latencies showed that CAT identified and responded to events 1.4 seconds faster than the original human experimenter. Finally, we present a case study in which CAT was used live for real-time autonomous, closed-loop bladder control in a single human subject with SCI and NDO, successfully inhibiting four consecutive unwanted bladder contractions and increasing bladder capacity by 40%.

Suburothelial Bladder Contraction Detection with Implanted Pressure Sensor

Aims

Managing bladder pressure in patients with neurogenic bladders is needed to improve rehabilitation options, avoid upper tract damage, incontinence, and their associated co-morbidities and mortality. Current methods of determining bladder contractions are not amenable to chronic or ambulatory settings. In this study we evaluated detection of bladder contractions using a novel piezoelectric catheter-free pressure sensor placed in a suburothelial bladder location in animals.

Methods

Wired prototypes of the pressure monitor were implanted into 2 nonsurvival (feline and canine) and one 13-day survival (canine) animal. Vesical pressures were obtained from the device in both suburothelial and intraluminal locations and simultaneously from a pressure sensing catheter in the bladder. Intravesical pressure was monitored in the survival animal over 10 days from the suburothelial location and necropsy was performed to assess migration and erosion.

Results

In the nonsurvival animals, the average correlation between device and reference catheter data was high during both electrically stimulated bladder contractions and manual compressions (r = 0.93±0.03, r = 0.89±0.03). Measured pressures correlated strongly (r = 0.98±0.02) when the device was placed in the bladder lumen. The survival animal initially recorded physiologic data, but later this deteriorated. However, endstage intraluminal device recordings correlated (r = 0.85±0.13) with the pressure catheter. Significant erosion of the implant through the detrusor was found.

Conclusions

This study confirms correlation between suburothelial pressure readings and intravesical bladder pressures. Due to device erosion during ambulatory studies, a wireless implant is recommended for clinical rehabilitation applications.

Wireless Bladder Pressure Monitor for Closed-Loop Bladder Neuromodulation

Conditional neuromodulation is a form of closed-loop bladder control where neurostimulation is applied in reaction to bladder pressure changes. Current methods based on external catheters have limited utility for chronic ambulatory therapy. We have developed a wireless pressure monitor to provide real-time, catheter-free detection of bladder contractions. The device is sized for chronic implantation in the bladder muscle. The pressure monitor consists of an ultra-low-power application specific integrated circuit (ASIC), micro-electro-mechanical (MEMS) pressure sensor, RF antennas, and rechargeable battery. Here we describe an overview of the system, including chronic in vivo test data of a non-hermetic polymer sensor package and chronic testing of the wireless sensor in large animal models. Test results show that the packaging method is viable for chronic encapsulation of implanted pressure sensors. Chronic testing of the pressure monitor revealed some obstacles relating to the chosen implant site within the bladder wall. However, chronic wireless device function was confirmed and data quality was sufficient to detect bladder compressions in large animals, with average correlation coefficient of 0.90.

Air filled, including "air-charged," catheters in urodynamic studies: does the evidence justify their use?

AIMS

Air filled catheters (AFCs) have been actively marketed for the past few years and in some geographic areas are widely used. However, as the scientific basis for introduction of this technology for pressure measurement in urodynamics was not clear, a study group examined the evidence.

METHODS

A search of the peer reviewed literature was carried out.

RESULTS

Four papers were identified, of which two were laboratory experiments and two were clinical papers, in female patients, that compared the pressures recorded by AFCs and those recorded using the traditional water filled catheters (WFCs). These data show that there are differences between the pressures measured by the two types of catheters. As yet, the reasons for these differences are not clear.

CONCLUSIONS

There should be further systematic laboratory and clinical research before AFCs can be recommended for routine clinical use. We would recommend that a professional worldwide multidisciplinary scientific society, such as the International Continence Society, should work with manufacturers and regulatory bodies to ensure that this urodynamic method is properly scientifically evaluated, in the wider interests of patient safety.