The effects of long-term spinal cord injury on mechanical properties of the rat urinary bladder

Effects of swelling and anatomical location on the viscoelastic behavior of the porcine urinary bladder wall

The ability of the urinary bladder to perform its physiological function depends largely on its mechanical characteristics. Understanding the mechanics of this tissue is crucial to the development of accurate models of not just this specific organ, but of the pelvic floor overall. In this study, we tested porcine bladder to identify variations in the tissue's viscoelastic characteristics associated with anatomical locations and swelling. We investigated this relationship using a series of stress-relaxation experiments as well as a modified Maxwell-Wiechert model to aid in the interpretation of the experimental data. Our results highlight that tissue located near the neck of the bladder presents significantly different viscoelastic characteristics than the body of the organ. This supports what was previously observed and is a valuable contribution to the understanding of the location-specific properties of the bladder. We also tested the effect of swelling, revealing that the bladder's viscoelastic behavior is mostly independent of solution osmolarity in hypoosmotic solutions, but the use of a hyperosmotic solution can significantly affect its behavior. This is significant, since several urinary tract pathologies can lead to chronic inflammation and disrupt the urothelial barrier causing increased urothelial permeability, thus subjecting the bladder wall to non-physiologic osmotic challenge.

Using uniaxial tensile testing to evaluate the biomechanical properties of bladder tissue after spinal cord injury in rat model

To investigate the biomechanical properties of rat bladder tissue after spinal cord injury (SCI) using uniaxial tensile testing. Evidence suggests the bladder wall undergoes remodeling following SCI. There is limited data describing the biomechanical properties of bladder wall after SCI. This study describes the changes in elastic and viscoelastic mechanical properties of bladder tissue using a rat model after SCI. Seventeen adult rats received mid-thoracic SCI. Basso, Beattie, and Bresnahan (BBB) locomotor testing was performed on the rats 7-14 days after injury quantifying the degree of SCI. Bladder tissue samples were collected from controls and spinal injured rats at 2- and 9-weeks post-injury. Tissue samples underwent uniaxial stress relaxation to determine instantaneous and relaxation modulus as well as monotonic load-to failure to determine Young's modulus, yield stress and strain, and ultimate stress. SCI resulted in abnormal BBB locomotor scores. Nine weeks post-injury, instantaneous modulus decreased by 71.0% (p = 0.03) compared to controls. Yield strain showed no difference at 2 weeks post-injury but increased 78% (p = 0.003) in SCI rats at 9 weeks post-injury. Compared to controls, ultimate stress decreased 46.5% (p = 0.05) at 2 weeks post-injury in SCI rats but demonstrated no difference at 9 weeks post-injury. The biomechanical properties of rat bladder wall 2 weeks after SCI showed minimal difference compared to controls. By week 9, SCI bladders had a reduction in instantaneous modulus and increased yield strain. The findings indicate biomechanical differences can be identified between control and experimental groups at 2- and 9-week intervals using uniaxial testing.

Spinal Cord Injury Causes Marked Tissue Rearrangement in the Urethra-Experimental Study in the Rat

Traumatic spinal cord injury (SCI) results in the time-dependent development of urinary impairment due to neurogenic detrusor overactivity (NDO) and detrusor-sphincter-dyssynergia (DSD). This is known to be accompanied by massive changes in the bladder wall. It is presently less clear if the urethra wall also undergoes remodelling. To investigate this issue, female rats were submitted to complete spinal transection at the T8/T9 level and left to recover for 1 week and 4 weeks. To confirm the presence of SCI-induced NDO, bladder function was assessed by cystometry under urethane anesthesia before euthanasia. Spinal intact animals were used as controls. Urethras were collected and processed for further analysis. Following thoracic SCI, time-dependent changes in the urethra wall were observed. Histological assessment revealed marked urethral epithelium reorganization in response to SCI, as evidenced by an increase in epithelial thickness. At the muscular layer, SCI resulted in strong atrophy of the smooth muscle present in the urethral sphincter. Innervation was also affected, as evidenced by a pronounced decrease in the expression of markers of general innervation, particularly those present in sensory and sympathetic nerve fibres. The present data show an evident impact of SCI on the urethra, with significant histological rearrangement, accompanied by sensory and sympathetic denervation. It is likely that these changes will affect urethral function and contribute to SCI-induced urinary dysfunction, and they deserve further investigation.

A constrained mixture-micturition-growth (CMMG) model of the urinary bladder: Application to partial bladder outlet obstruction (BOO)

We present a constrained mixture-micturition-growth (CMMG) model for the bladder. It simulates bladder mechanics, voiding function (micturition) and tissue adaptations in response to altered biomechanical conditions. The CMMG model is calibrated with both in vivo and in vitro data from healthy male rat urinary bladders (cystometry, bioimaging of wall structure, mechanical testing) and applied to simulate the growth and remodeling (G&R) response to partial bladder outlet obstruction (BOO). The bladder wall is represented as a multi-layered, anisotropic, nonlinear constrained mixture. A short time scale micturition component of the CMMG model accounts for the active and passive mechanics of voiding. Over a second, longer time scale, G&R algorithms for the evolution of both cellular and extracellular constituents act to maintain/restore bladder (homeostatic) functionality. The CMMG model is applied to a spherical membrane model of the BOO bladder utilizing temporal data from an experimental male rodent model to parameterize and then verify the model. Consistent with the experimental studies of BOO, the model predicts: an initial loss of voiding capacity followed by hypertrophy of SMC to restore voiding function; bladder enlargement; collagen remodeling to maintain its role as a protective sheath; and increased voiding duration with lower average flow rate. This CMMG model enables a mechanistic approach for investigating the bladder's structure-function relationship and its adaption in pathological conditions. While the approach is illustrated with a conceptual spherical bladder model, it provides the basis for application of the CMMG model to anatomical geometries. Such a mechanistic approach has promise as an in silico tool for the rational development of new surgical and pharmacological treatments for bladder diseases such as BOO.

Increased extracellular matrix stiffness accompanies compromised bladder function in a murine model of radiation cystitis

Radiation cystitis, a long-term bladder defect due to pelvic radiation therapy, results in lower urinary tract symptoms, such as urinary frequency and nocturia, suggestive of compromised bladder compliance. The goal of this study was to identify alterations to the mechanical behavior of the urinary bladder extracellular matrix of a murine model of radiation cystitis, at 3 and 6 months after radiation exposure. The results of this study demonstrated that the extracellular matrix of irradiated bladders was significantly less distensible when compared to age matching controls. These findings coincided with functional bladder changes, including increased number of voids and decreased voided volume. Both mechanical and functional changes were apparent at 3 months post-irradiation and were statistically significant at 6 months, demonstrating the progressive nature of radiation cystitis. Overall, the results of this study indicate that irradiation exposure changes both the mechanical and physiological properties of the bladder. STATEMENT OF SIGNIFICANCE: In humans, radiation cystitis results in lower urinary tract symptoms, such as urinary frequency and nocturia, suggestive of compromised bladder compliance. This pathology can significantly affect recovery and quality of life for cancer survivors. Gaining knowledge about how alterations to the mechanical behavior of the urinary bladder extracellular matrix can affect urinary function will have a significant impact on this population. The results of this study demonstrated that the extracellular matrix of irradiated bladders was significantly less distensible when compared to age matching controls, in a mouse model of radiation cystitis. These findings were accompanied by functional voiding changes, including increased number of voids and decreased voided volume. The results of this study uncovered that irradiation exposure changes the mechanical and physiological properties of the bladder.

Remodeling of extracellular matrix in the urinary bladder of paraplegic rats results in increased compliance and delayed fiber recruitment 16 weeks after spinal cord injury

The ability of the urinary bladder to maintain low intravesical pressures while storing urine is key in ensuring proper organ function and highlights the key role that tissue mechanics plays in the lower urinary tract. Loss of supraspinal neuronal connections to the bladder after spinal cord injury can lead to remodeling of the structure of the bladder wall, which may alter its mechanical characteristics. In this study, we investigate if the morphology and mechanical properties of the bladder extracellular matrix are altered in rats 16 weeks after spinal cord injury as compared to animals who underwent sham surgery. We measured and quantified the changes in bladder geometry and mechanical behavior using histological analysis, tensile testing, and constitutive modeling. Our results suggest bladder compliance is increased in paraplegic animals 16 weeks post-injury. Furthermore, constitutive modeling showed that increased distensibility was driven by an increase in collagen fiber waviness, which altered the distribution of fiber recruitment during loading. STATEMENT OF SIGNIFICANCE: The ability of the urinary bladder to store urine under low pressure is key in ensuring proper organ function. This highlights the important role that mechanics plays in the lower urinary tract. Loss of control of neurologic connection to the bladder from spinal cord injury can lead to changes of the structure of the bladder wall, resulting in altered mechanical characteristics. We found that the bladder wall's microstructure in rats 16 weeks after spinal cord injury is more compliant than in healthy animals. This is significant since it is the longest time post-injury analyzed, to date. Understanding the extreme remodeling capabilities of the bladder in pathological conditions is key to inform new possible therapies.

Location- and layer-dependent biomechanical and microstructural characterisation of the porcine urinary bladder wall

The knowledge of the mechanical properties of the urinary bladder wall helps to explain its storage and micturition functions in health and disease studies; however, these properties largely remain unknown, especially with regard to its layer-specific characteristics and microstructure. Consequently, this study entails the assessment of the layer-specific differences in the mechanical properties and microstructure of the bladder wall, especially during loading. Accordingly, ninety-two (n=92) samples of porcine urinary bladder walls were mechanically and histologically analysed. Generally, the bladder wall and different tissue layers exhibit a non-linear stress-stretch relationship. In this study, the load transfer mechanisms were not only associated with the wavy structure of muscular and mucosal layers, but also with the entire bladder wall microstructure. Contextually, an interplay between the mucosal and muscular layers could be identified. Therefore, depending on the region and direction, the mucosal layer exhibited a stiffer mechanical response to equi-biaxial loading than that offered by the muscular layer when deformed to stretch levels higher than λ=1.6 to λ=2.2. For smaller stretches, the mucosal layer evinces no significant mechanical reaction, while the muscular layer bears the load. Owing to the orientation of its muscle fibres, the muscular layer shows an increased degree of anisotropy compared to the mucosal layer. Furthermore, the general incompressibility assumption is analysed for different layers by measuring the change in thickness during loading, which indicated a small volume loss.

Effect of amniotic fluid stem cell transplantation on the recovery of bladder dysfunction in spinal cord-injured rats

The effects of human amniotic fluid stem cell (hAFSC) transplantation on bladder function and molecular changes in spinal cord-injured (SCI) rats were investigated. Four groups were studied: sham and SCI plus phosphate-buffered saline (SCI + PBS), human embryonic kidney 293 (HEK293) cells, and hAFSCs transplantation. In SCI + PBS rat bladders, cystometry showed increased peak voiding pressure, voiding volume, bladder capacity, residual volume, and number of non-voiding contractions, and the total elastin/collagen amount was increased but collagen concentration was decreased at days 7 and 28. Immunoreactivity and mRNA levels of IGF-1, TGF-β1, and β3-adrenoceptor were increased at days 7 and/or 28. M2 immunoreactivity and M3 mRNA levels of muscarinic receptor were increased at day 7. M2 immunoreactivity was increased, but M2/M3 mRNA and M3 immunoreactivity levels were decreased at day 28. Brain derived-neurotrophic factor mRNA was increased, but immunoreactivity was decreased at day 7. HEK293 cell transplantation caused no difference compared to SCI + PBS group. hAFSCs co-localized with neural cell markers and expressed BDNF, TGF-β1, GFAP, and IL-6. The present results showed that SCI bladders released IGF-1 and TGF-β1 to stimulate elastin and collagen for bladder wall remodelling, and hAFSC transplantation improved these changes, which involved the mechanisms of BDNF, muscarinic receptors, and β3-adrenoceptor expression.

Recommendations for evaluation of bladder and bowel function in pre-clinical spinal cord injury research

Objective: In order to encourage the inclusion of bladder and bowel outcome measures in preclinical spinal cord injury (SCI) research, this paper identifies and categorizes 1) fundamental, 2) recommended, 3) supplemental and 4) exploratory sets of outcome measures for pre-clinical assessment of bladder and bowel function with broad applicability to animal models of SCI.Methods: Drawing upon the collective research experience of autonomic physiologists and informed in consultation with clinical experts, a critical assessment of currently available bladder and bowel outcome measures (histological, biochemical, in vivo functional, ex vivo physiological and electrophysiological tests) was made to identify the strengths, deficiencies and ease of inclusion for future studies of experimental SCI.Results: Based upon pre-established criteria generated by the Neurogenic Bladder and Bowel Working Group that included history of use in experimental settings, citations in the literature by multiple independent groups, ease of general use, reproducibility and sensitivity to change, three fundamental measures each for bladder and bowel assessments were identified. Briefly defined, these assessments centered upon tissue morphology, voiding efficiency/volume and smooth muscle-mediated pressure studies. Additional assessment measures were categorized as recommended, supplemental or exploratory based upon the balance between technical requirements and potential mechanistic insights to be gained by the study.Conclusion: Several fundamental assessments share reasonable levels of technical and material investment, including some that could assess bladder and bowel function non-invasively and simultaneously. Such measures used more inclusively across SCI studies would advance progress in this high priority area. When complemented with a few additional investigator-selected study-relevant supplemental measures, they are highly recommended for research programs investigating the efficacy of therapeutic interventions in preclinical animal models of SCI that have a bladder and/or bowel focus.

What is the utility of urodynamics, including ambulatory, and 24 h monitoring, in predicting upper urinary tract damage in neuro-urological patients and other lower urinary tract dysfunction? ICI-RS 2017

AIMS

This article focuses on how, and if, urodynamics can help to identify which kidneys are in danger of deteriorating in function and also gives recommendations for future research.

METHODS

At the International Consultation on Incontinence-Research Society (ICI-RS) in 2017, a multi-disciplinary group presented a literature search of what is known about the utility of Urodynamics, including ambulatory, and 24 h monitoring, in predicting upper urinary tract damage in neuro-urological patients and other lower urinary tract dysfunctions. Wider discussions regarding knowledge gaps, and ideas for future research ensued and are presented in this paper along with a review of the evidence.

RESULTS

The current treatment strategy both in congenital and acquired neurogenic bladder is rather aggressive and successful when addressing hazards to kidney function. This article has highlighted uncertainties concerning the use of 40 cmH2O DLPP and even the lower value of 20. The current literature suggests that patients with spina bifida and those with spinal cord injury have a higher risk of developing upper urinary tract damage and kidney function impairment than those with multiple sclerosis.

CONCLUSIONS

Future research should focus on less invasive methods to assess the risk to the upper and lower urinary tract such as urine and serum measurements of cytokines that are involved in the pathophysiology of urinary tract impairment.

Location-dependent correlation between tissue structure and the mechanical behaviour of the urinary bladder

The mechanical properties of the urinary bladder wall are important to understand its filling-voiding cycle in health and disease. However, much remains unknown about its mechanical properties, especially regarding regional heterogeneities and wall microstructure. The present study aimed to assess the regional differences in the mechanical properties and microstructure of the urinary bladder wall. Ninety (n=90) samples of porcine urinary bladder wall (ten samples from nine different locations) were mechanically and histologically analysed. Half of the samples (n=45) were equibiaxially tested within physiological conditions, and the other half, matching the sample location of the mechanical tests, was frozen, cryosectioned, and stained with Picro-Sirius red to differentiate smooth muscle cells, extracellular matrix, and fat. The bladder wall shows a non-linear stress-stretch relationship with hysteresis and softening effects. Regional differences were found in the mechanical response and in the microstructure. The trigone region presents higher peak stresses and thinner muscularis layer compared to the rest of the bladder. Furthermore, the ventral side of the bladder presents anisotropic characteristics, whereas the dorsal side features perfect isotropic behaviour. This response matches the smooth muscle fibre bundle orientation within the tunica muscularis. This layer, comprising approximately 78% of the wall thickness, is composed of two fibre bundle arrangements that are cross-oriented, one with respect to the other, varying the angle between them across the organ. That is, the ventral side presents a 60°/120° cross-orientation structure, while the muscle bundles were oriented perpendicular in the dorsal side.

STATEMENT OF SIGNIFICANCE

In the present study, we demonstrate that the mechanical properties and the microstructure of the urinary bladder wall are heterogeneous across the organ. The mechanical properties and the microstructure of the urinary bladder wall within nine specific locations matching explicitly the mechanical and structural variations have been examined. On the one hand, the results of this study contribute to the understanding of bladder mechanics and thus to their functional understanding of bladder filling and voiding. On the other hand, they are relevant to the fields of constitutive formulation of bladder tissue, whole bladder mechanics, and bladder-derived scaffolds i.e., tissue-engineering grafts.

Anatomical and Functional Changes to the Colonic Neuromuscular Compartment after Experimental Spinal Cord Injury

A profound reduction in colorectal transit time accompanies spinal cord injury (SCI), yet the colonic alterations after SCI have yet to be understood fully. The loss of descending supraspinal input to lumbosacral neural circuits innervating the colon is recognized as one causal mechanism. Remodeling of the colonic enteric nervous system/smooth muscle junction in response to inflammation, however, is recognized as one factor leading to colonic dysmotility in other pathophysiological models. We investigated the alterations to the neuromuscular junction in rats with experimental high-thoracic (T3) SCI. One day to three weeks post-injury, both injured and age-matched controls underwent in vivo experimentation followed by tissue harvest for histological evaluation. Spontaneous colonic contractions were reduced significantly in the proximal and distal colon of T3-SCI rats. Histological evaluation of proximal and distal colon demonstrated significant reductions of colonic mucosal crypt depth and width. Markers of intestinal inflammation were assayed by qRT-PCR. Specifically, Icam1, Ccl2 (MCP-1), and Ccl3 (MIP-1α) mRNA was acutely elevated after T3-SCI. Smooth muscle thickness and collagen content of the colon were increased significantly in T3-SCI rats. Colonic cross sections immunohistochemically processed for the pan-neuronal marker HuC/D displayed a significant decrease in colonic enteric neuron density that became more pronounced at three weeks after injury. Our data suggest that post-SCI inflammation and remodeling of the enteric neuromuscular compartment accompanies SCI. These morphological changes may provoke the diminished colonic motility that occurs during this same period, possibly through the disruption of intrinsic neuromuscular control of the colon.

Structural Changes of the Urinary Bladder After Chronic Complete Spinal Cord Injury in Minipigs

Purpose

The aim of this study was to determine the structural changes of the urinary bladder after chronic spinal cord injury (SCI) in minipigs with the primary focus on the analysis of urinary bladder wall proteins and their quantitative distribution.

Methods

Seven Göttingen minipigs (adult, female) underwent a complete spinal cord transection. Follow-up time was 4 months during which the bladder was drained by frequent single catheterisation and data from the bladder diary and daily urine strip test were collected. Samples from the urinary bladder were taken, fixed in 4% paraformaldehyde and stained for histological analyses. Bladder wall thickness, single tissue quantities/distributions, types I and III collagen, and elastin quantifications were performed. Comparisons to healthy urinary bladder tissue of age-matched minipigs were performed for statistical analyses.

Results

No urinary tract infections were observed in our SCI minipig collective during follow-up. A trend towards a reduction in bladder volumes and an increase in incontinence periods were seen. The bladder wall thickness significantly increased after chronic SCI. Furthermore, bladder wall composition was severely altered by a significant loss of smooth muscle tissue and a significant increase in connective tissue. Elastic fibres were reduced in number and altered in their structural appearance after SCI. Type I collagen was significantly increased, while type III collagen was significantly decreased after SCI.

Conclusions

Chronic SCI highlighted that the urinary bladder wall undergoes fibrotic events with reduced contractile and elastic properties due to changes of the bladder wall protein composition. These changes show in detail how SCI severely influences the urinary bladder wall composition and depicts the similarities between minipigs and humans.

Modeling the influence of acute changes in bladder elasticity on pressure and wall tension during filling

Tension-sensitive nerves in the bladder wall are responsible for providing bladder sensation. Bladder wall tension, and therefore nerve output, is a function of bladder pressure, volume, geometry and material properties. The elastic modulus of the bladder is acutely adjustable, and this material property is responsible for adjustable preload tension exhibited in human and rabbit detrusor muscle strips and dynamic elasticity revealed during comparative-fill urodynamics in humans. A finite deformation model of the bladder was previously used to predict filling pressure and wall tension using uniaxial tension test data and the results showed that wall tension can increase significantly during filling with relatively little pressure change. In the present study, published uniaxial rabbit detrusor data were used to quantify regulated changes in the elastic modulus, and the finite deformation model was expanded to illustrate the potential effects of elasticity changes on pressure and wall tension during filling. The model demonstrates a shift between relatively flat pressure-volume filling curves, which is consistent with a recent human urodynamics study, and also predicts that dynamic elasticity would produce significant changes in wall tension during filling. The model results support the conclusion that acute regulation of bladder elasticity could contribute to significant changes in wall tension for a given volume that could lead to urgency, and that a single urodynamic fill may be insufficient to characterize bladder biomechanics. The model illustrates the potential value of quantifying wall tension in addition to pressure during urodynamics.

Effects of exercise training on urinary tract function after spinal cord injury

Spinal cord injury (SCI) causes dramatic changes in the quality of life, including coping with bladder dysfunction which requires repeated daily and nightly catheterizations. Our laboratory has recently demonstrated in a rat SCI model that repetitive sensory information generated through task-specific stepping and/or loading can improve nonlocomotor functions, including bladder function (Ward PJ, Herrity AN, Smith RR, Willhite A, Harrison BJ, Petruska JC, Harkema SJ, Hubscher CH. J Neurotrauma 31: 819-833, 2014). To target potential underlying mechanisms, the current study included a forelimb-only exercise group to ascertain whether improvements may be attributed to general activity effects that impact target organ-neural interactions or to plasticity of the lumbosacral circuitry that receives convergent somatovisceral inputs. Male Wistar rats received a T9 contusion injury and were randomly assigned to three groups 2 wk postinjury: quadrupedal locomotion, forelimb exercise, or a nontrained group. Throughout the study (including preinjury), all animals were placed in metabolic cages once a week for 24 h to monitor water intake and urine output. Following the 10-wk period of daily 1-h treadmill training, awake cystometry data were collected and bladder and kidney tissue harvested for analysis. Metabolic cage frequency-volume measurements of voiding and cystometry reveal an impact of exercise training on multiple SCI-induced impairments related to various aspects of urinary tract function. Improvements in both the quadrupedal and forelimb-trained groups implicate underlying mechanisms beyond repetitive sensory information from the hindlimbs driving spinal network excitability of the lumbosacral urogenital neural circuitry. Furthermore, the impact of exercise training on the upper urinary tract (kidney) underscores the health benefit of activity-based training on the entire urinary system within the SCI population.

Characterization of bladder and external urethral activity in mice with or without spinal cord injury--a comparison study with rats

To clarify the lower urinary tract function in mice, we compared bladder and urethral activity between rats and mice with or without spinal cord injury (SCI). Female Sprague-Dawley rats and C57BL/6N mice were divided into five groups:1) spinal intact (SI) rats,2) SI mice,3) pudendal nerve transection (PNT) SI mice,4) spinal cord injury (SCI) rats, and 5) SCI mice. Continuous cystometry (CMG) and external urethral sphincter (EUS)-electromyogram (EMG) analyses were conducted under an awake, restrained condition. During voiding bladder contractions, SI animals exhibited EUS bursting with alternating active and silent periods, which, in rats but not mice, coincided with small-amplitude intravesical pressure oscillations in CMG recordings. In SI mice with bursting-like EUS activity, the duration of active periods was significantly shorter by 46% (32 ± 5 ms) compared with SI rats (59 ± 9 ms). In PNT-SI mice, there were no significant differences in any of cystometric parameters compared with SI mice. In SCI rats, fluid elimination from the urethra and the EUS bursting occurred during small-amplitude intravesical pressure oscillations. However, SCI mice did not exhibit clear EUS bursting activity or intravesical pressure oscillations but rather exhibited intermittent voiding with slow large-amplitude reductions in intravesical pressure, which occurred during periods of reduced EUS activity. These results indicate that EUS pumping activity is essential for generating efficient voiding in rats with or without spinal cord injury. However, EUS bursting activity is not required for efficient voiding in SI mice and does not reemerge in SCI mice in which inefficient voiding occurs during periods of reduced tonic EUS activity.

Protective effects of Vitamin C against spinal cord injury-induced renal damage through suppression of NF-κB and proinflammatory cytokines

Spinal cord injury [SCI] leads to complex cellular and molecular interactions which affects various organ systems. The present study focused on determining the protection offered by Vitamin C against spinal injury-induced kidney damage in wistar rats. The experimental protocol was performed with three groups; Sham, SCI and Vitamin C [20 mg/kg/bw] followed by SCI. The kidney tissue was investigated for oxidative stress parameters [reactive oxygen species, protein carbonyl, sulphydryl content, thiobarbituric acid reactive species [TBARS], and myeloperoxidase activity] and antioxidant status [glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase activity]. Further, inflammation studies were performed by analyzing expression of NF-κB, cycloxygenase-2, iNOS through western blot analysis and inflammatory cytokines by TNF-α and IL-1β levels. The present study shows clear evidence that Vitamin C treatment abrogated spinal injury-induced oxidative stress and inflammatory responses and enhanced the antioxidant status. Thus, the protection offered by Vitamin C against spinal cord injury-induced kidney damage is attributed to its anti-oxidant and anti-inflammatory effects.

Protective effects of melatonin against spinal cord injury induced oxidative damage in rat kidney: A morphological and biochemical study

Spinal cord injury (SCI) induced oxidative stress affects multiple organ systems including the kidney. We studied the possible protective effects of melatonin on SCI-induced oxidative damage in renal tissues of rats. Wistar albino rats (n = 24) were exposed to SCI and divided into vehicle- or melatonin-treated SCI groups. Melatonin was administred intraperitoneally at a dose of 10 mg/kg for seven days. Renal tissues were investigated by light and electron microscopy. Furthermore, tissue malondialdehyde (MDA) and glutathione (GSH) levels and myeloperoxidase (MPO) and superoxide dismutase (SOD) activities were also determined. In the vehicle-treated SCI group, the renal histology was disturbed compared to controls, whereas the melatonin-treated SCI group showed significantly reduced degeneration of renal tissue as seen by both light and electron microscopy. MDA levels, MPO and SOD activities were increased and GSH levels were decreased in the vehicle-treated SCI group compared to controls. On the other hand, decreased MDA levels and MPO activities and increased GSH levels were observed in the melatonin-treated SCI group compared to vehicle-treated SCI group. These results showed that experimentally induced SCI caused oxidative stress in the rat kidney, whereas melatonin treatment reduced oxidative stress, suggesting that it may be used as a complementary therapy of renal problems occurring following SCI.

The effects of Glivec on the urinary bladder excitation of rats with suprasacral or sacral spinal cord transection

BACKGROUND

To investigate the effects of the c-kit blocker imatinib mesylate (Glivec) on the bladders of animals with suprasacral cord injury (SSCI) and sacral cord injury (SCI).

MATERIALS AND METHODS

We randomized 60 female Sprague-Dawley rats into control, sham, SSCI (T8/9 transection), and SCI (S1-3 transection) groups. Six weeks later, we evaluated the effects of stepwise Glivec administrations on urinary bladder contraction using cystometry and the detrusor strip stretch-test. We investigated spontaneous calcium transients of kit-positive interstitial cells of Cajal (ICCs) with the preloaded Ca(2+) indicator fluo-3AM. The expression levels of c-kit and the number of ICCs in those bladders were determined using Western blot and fluorescence staining analyses, respectively.

RESULTS

Bladder capacity and compliance were decreased in SSCI bladders and increased in SCI bladders (P<0.05). The amplitude and frequency of spontaneous contractions of detrusor strips, the frequency and relative fluorescence intensity of the spontaneous Ca(2+) waves, and c-kit expression in the bladder were significantly increased in the SSCI group and decreased in the SCI group compared with the control and sham groups (P<0.05). The dose-dependent effects of Glivec also confirmed consistent functional variations in bladder activity.

CONCLUSIONS

The expressions and effects of Glivec were enhanced in SSCI bladders and inhibited in SCI bladders, which may indicate potential roles of ICCs for the c-kit signaling pathway in the pathogenesis of SSCI and SCI bladder.

Altered distribution of interstitial cells and innervation in the rat urinary bladder following spinal cord injury

Changes in the distribution of interstitial cells (IC) are reportedly associated with dysfunctional bladder. This study investigated whether spinal cord injury (SCI) resulted in changes to IC subpopulations (vimentin-positive with the ultrastructural profile of IC), smooth muscle and nerves within the bladder wall and correlated cellular remodelling with functional properties. Bladders from SCI (T8/9 transection) and sham-operated rats 5 weeks post-injury were used for ex vivo pressure–volume experiments or processed for morphological analysis with transmission electron microscopy (TEM) and light/confocal microscopy. Pressure-volume relationships revealed low-pressure, hypercompliance in SCI bladders indicative of decompensation. Extensive networks of vimentin-positive IC were typical in sham lamina propria and detrusor but were markedly reduced post-SCI; semi-quantitative analysis showed significant reduction. Nerves labelled with anti-neurofilament and anti-vAChT were notably decreased post-SCI. TEM revealed lamina propria IC and detrusor IC which formed close synaptic-like contacts with vesicle-containing nerve varicosities in shams. Lamina propria and detrusor IC were ultrastructurally damaged post-SCI with retracted/lost cell processes and were adjacent to areas of cellular debris and neuronal degradation. Smooth muscle hypertrophy was common to SCI tissues. In conclusion, IC populations in bladder wall were decreased 5 weeks post-SCI, accompanied with reduced innervation, smooth muscle hypertrophy and increased compliance. These novel findings indicate that bladder wall remodelling post-SCI affects the integrity of interactions between smooth muscle, nerves and IC, with compromised IC populations. Correlation between IC reduction and a hypercompliant phenotype suggests that disruption to bladder IC contribute to pathophysiological processes underpinning the dysfunctional SCI bladder.

Melatonin treatment protects against spinal cord injury induced functional and biochemical changes in rat urinary bladder

Oxidative stress induced by spinal cord injury (SCI) has deleterious effects on the function of several organ systems including the urinary bladder. In this study, we investigated the possible protective actions of melatonin on SCI-induced oxidative damage and urinary bladder dysfunction. Wistar albino rats (n = 24) were divided randomly as control, vehicle- or melatonin (10 mg/kg, ip)-treated SCI groups. To induce SCI, a standard weight-drop method that induced a moderately severe injury at T10 was used. Injured animals were given either vehicle or melatonin 15 min postinjury. One week postinjury, each rat was neurologically examined and then decapitated; blood samples were taken to evaluate neuron-specific enolase (NSE) and soluble protein 100β (S-100β). Spinal cord (SC) and urinary bladder samples were taken for functional studies and histological examination or stored for the measurement of malondialdehyde (MDA), glutathione (GSH) and nerve growth factor (NGF) levels and caspase-3 activity. Isometric contractions in bladder strips were induced by carbachol. In the SCI rats, decreased contractile responses of the bladder strips were found to be restored by melatonin treatment. Serum S-100β levels and NSE activities and tissue MDA levels and caspase-3 activities, all of which were elevated in the vehicle-treated SCI animals as compared to the control values, were reversed by melatonin treatment. On the other hand, reduced GSH and NGF levels due to SCI were restored by melatonin treatment. Furthermore, melatonin treatment improved histological findings. These findings suggest that melatonin reduces SCI-induced tissue injury and improves bladder functions through its effects on oxidative stress and NGF.

Strain history and TGF-β1 induce urinary bladder wall smooth muscle remodeling and elastogenesis

Mechanical cues that trigger pathological remodeling in smooth muscle tissues remain largely unknown and are thought to be pivotal triggers for strain-induced remodeling. Thus, an understanding of the effects mechanical stimulation is important to elucidate underlying mechanisms of disease states and in the development of methods for smooth muscle tissue regeneration. For example, the urinary bladder wall (UBW) adaptation to spinal cord injury (SCI) includes extensive hypertrophy as well as increased collagen and elastin, all of which profoundly alter its mechanical response. In addition, the pro-fibrotic growth factor TGF-β1 is upregulated in pathologies of other smooth muscle tissues and may contribute to pathological remodeling outcomes. In the present study, we utilized an ex vivo organ culture system to investigate the response of UBW tissue under various strain-based mechanical stimuli and exogenous TGF-β1 to assess extracellular matrix (ECM) synthesis, mechanical responses, and bladder smooth muscle cell (BSMC) phenotype. Results indicated that a 0.5-Hz strain frequency triangular waveform stimulation at 15% strain resulted in fibrillar elastin production, collagen turnover, and a more compliant ECM. Further, this stretch regime induced changes in cell phenotype while the addition of TGF-β1 altered this phenotype. This phenotypic shift was further confirmed by passive strip biomechanical testing, whereby the bladder groups treated with TGF-β1 were more compliant than all other groups. TGF-β1 increased soluble collagen production in the cultured bladders. Overall, the 0.5-Hz strain-induced remodeling caused increased compliance due to elastogenesis, similar to that seen in early SCI bladders. Thus, organ culture of bladder strips can be used as an experimental model to examine ECM remodeling and cellular phenotypic shift and potentially elucidate BMSCs ability to produce fibrillar elastin using mechanical stretch either alone or in combination with growth factors.

Acute and chronic deficits in the urinary bladder after spinal contusion injury in the adult rat

Traumatic spinal cord injury (SCI) permanently alters bladder function in humans. Hematuria and cystitis occur in both human SCI as well as in rodent models of SCI. Others have reported early SCI-dependent disruption to bladder uroepithelial integrity that results in increased permeability to urine and urine-borne substances. This can result in cystitis, or inflammation of the bladder, an ongoing pathological condition present throughout the chronic phase of SCI in humans. The goals of our study were twofold: (1) to begin to examine the inflammatory and molecular changes that occur within the bladder uroepithelium using a clinically-relevant spinal contusion model of injury, and (2) to assess whether these alterations continue into the chronic phase of SCI. Rats received either moderate SCI or sham surgery. Urine was collected from SCI and sham subjects over 7 days or at 7 months to assess levels of excreted proteins. Inflammation in the bladder wall was assessed via biochemical and immunohistochemical methods. Bladder tight junction proteins, mediators of uroepithelial integrity, were also measured in both the acute and chronic phases of SCI. Urine protein and hemoglobin levels rapidly increase following SCI. An SCI-dependent elevation in numbers of neutrophils within the bladder wall peaked at 48 h. Bladder tight junction proteins demonstrate a rapid but transient decrease as early as 2 h post-SCI. Surprisingly, elevated levels of urine proteins and significant deficits in bladder tight junction proteins could be detected in chronic SCI, suggesting that early pathological changes to the bladder may continue throughout the chronic phase of injury.

Ex vivo deformations of the urinary bladder wall during whole bladder filling: contributions of extracellular matrix and smooth muscle

As the complete understanding of urinary bladder function requires knowledge of organ level deformations, we conducted ex vivo studies of surface strains of whole bladders during controlled filling. The surface strains derived from displacements of surface markers applied to the posterior surface of excised rat bladders were tracked under slow filling with pressure and volume simultaneously recorded in the passive and completely inactivated states (i.e. with and without smooth muscle tone, respectively). Bladders evaluated in the passive state exhibited spontaneous contractions and larger average peak pressures (16.7 mm Hg compared to 6.4 mm Hg in the inactive state). Overall, the bladders exhibited anisotropic deformations and were stiffer in the circumferential direction, with average peak stretch values of approximately 2.3 and approximately 1.9 in the longitudinal and circumferential directions, respectively, for both states. Although bladders in the passive state were stiffer, they had similar average peak areal stretches of 4.3 in both states. However, differences early in the filling process as a result of a loss in smooth muscle tone in the inactive state resulted in longitudinal lengthening of 36%. Idealizing the bladder as a prolate spheroid, we estimated the wall stress-strain relation during filling and demonstrated that the intact bladder exhibited the classic stress-stretch relation, with a significantly protracted low stress region and peak stresses of 36 and 51 kPa in the longitudinal and circumferential directions, respectively. The present study fills a major gap in the urinary bladder biomechanics literature, wherein knowledge of the pressure-volume-wall stress-wall strain relation was explored for the first time in a functioning organ ex vivo.

On the Mechanical Role of De Novo Synthesized Elastin in the Urinary Bladder Wall

The urinary bladder wall (UBW), which is composed of smooth muscle, collagen, and elastin, undergoes profound remodeling in response to changes in mechanical loading resulting from various pathologies. In our laboratory, we have observed the production of fibrillar elastin in the extracellular matrix (ECM), which makes the UBW a particularly attractive tissue to investigate smooth muscle tissue remodeling. In the present study, we explored the mechanical role that de novo elastin fibers play in altering UBW ECM mechanical behavior using a structural constitutive modeling approach. The mechanical behavior of the collagen fiber component of the UBW ECM was determined from the biaxial stress-stretch response of normal UBW ECM, based on bimodal fiber recruitment that was motivated by the UBW’s unique collagen fiber structure. The resulting fiber ensemble model was then combined with an experimentally derived fiber angular distribution to predict the biaxial mechanical behavior of normal and the elastin-rich UBW ECM to elucidate the underlying mechanisms of elastin production. Results indicated that UBW ECM exhibited a distinct structure with highly coiled collagen fiber bundles and visible elastic fibers in the pathological situation. Elastin-rich UBW ECM had a distinct mechanical behavior with higher compliance, attributable to the indirect effect of elastin fibers contracting the collagen fiber network, resulting in a retracted unloaded reference state of the tissue. In conclusion, our results suggest that the urinary bladder responds to prolonged periods of high strain by increasing its effective compliance through the interaction between collagen and de novo synthesized elastic fibers.

An exploratory pathways analysis of temporal changes induced by spinal cord injury in the rat bladder wall: insights on remodeling and inflammation

BACKGROUND

Spinal cord injuries (SCI) can lead to severe bladder pathologies associated with inflammation, fibrosis, and increased susceptibility to urinary tract infections. We sought to characterize the complex pathways of remodeling, inflammation, and infection in the urinary bladder at the level of the transcriptome in a rat model of SCI, using pathways analysis bioinformatics.

METHODOLOGY/PRINCIPAL FINDINGS

Experimental data were obtained from the study of Nagatomi et al. (Biochem Biophys Res Commun 334: 1159). In this study, bladders from rats subjected to surgical SCI were obtained at 3, 7 or 25 days post-surgery, and Affymetrix GeneChip Rat Genome U34A arrays were used for cRNA hybridizations. In the present study, Ingenuity Pathways Analysis (Ingenuity Systems, www.ingenuity.com) of differentially expressed genes was performed. Analysis of focus genes in networks, functional analysis, and canonical pathway analysis reinforced our previous findings related to the presence of up-regulated genes involved in tissue remodeling, such as lysyl oxidase, tropoelastin, TGF-beta1, and IGF-1. This analysis also highlighted a central role for inflammation and infection, evidenced by networks containing genes such as CD74, S100A9, and THY1.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that tissue remodeling, infection, inflammation, and tissue damage/dysfunction all play a role in the urinary bladder, in the complex response to SCI.