Elastin and collagen in the normal and obstructed urinary bladder

Investigation of Fiber-Driven Mechanical Behavior of Human and Porcine Bladder Tissue Tested Under Identical Conditions

The urinary bladder is a highly dynamic organ that undergoes large deformations several times per day. Mechanical characteristics of the tissue are crucial in determining the function and dysfunction of the organ. Yet, literature reporting on the mechanical properties of human bladder tissue is scarce and, at times, contradictory. In this study, we focused on mechanically testing tissue from both human and pig bladders using identical protocols to validate the use of pigs as a model for the human bladder. Furthermore, we tested the effect of two treatments on tissue mechanical properties. Namely, elastase to digest elastin fibers, and oxybutynin to reduce smooth muscle cell spasticity. Additionally, mechanical properties based on the anatomical direction of testing were evaluated. We implemented two different material models to aid in the interpretation of the experimental results. We found that human tissue behaves similarly to pig tissue at high deformations (collagen-dominated behavior) while we detected differences between the species at low deformations (amorphous matrix-dominated behavior). Our results also suggest that elastin could play a role in determining the behavior of the fiber network. Finally, we confirmed the anisotropy of the tissue, which reached higher stresses in the transverse direction when compared to the longitudinal direction.

New mouse model of underactive bladder developed by placement of a metal ring around the bladder neck

OBJECTIVE

To develop a new mouse model of underactive bladder (UAB) caused by chronic bladder outlet obstruction (BOO).

METHODS

BOO was created in 6-week-old male C57BL/6 mice using surgery to loosely place a silver jump ring around the bladder neck of each mouse. Micturition behavior (assessed with a metabolic cage) and cystometry were used to evaluate bladder function at 8 and 16 weeks after BOO. Following completion of the functional studies, the bladders of the mice were excised, weighed, and subjected to histological analysis.

RESULTS

Micturition behavior analysis showed that mice subjected to BOO for 16 weeks had a lower frequency of micturition (7.3 ± 1.1 vs 12.5 ± 3.0 times/d, P < .05) and volume per void (106.0 ± 0.1 vs 133.9 ± 3.2 μL, P < .05) than mice subjected to BOO for 8 weeks. Cystometry revealed that mice subjected to BOO for 16 weeks had lower baseline pressure (8.4 ± 0.6 vs 14.0 ± 0.7 cmH₂ O, P < .01) and micturition pressure (13.9 ± 1.1 vs 42.8 ± 1.7 cmH₂ O, P < .05) than mice subjected to BOO for 8 weeks. BOO caused progressive increases in bladder mass and collagen deposition over time.

CONCLUSIONS

We successfully established a novel mouse model of UAB using surgery to place a silver jump ring loosely on the bladder neck. BOO initially induced bladder overactivity but subsequently resulted in UAB due to deterioration of detrusor smooth muscle contractility and progressive deposition of collagen in the bladder wall.

Structural study of endopelvic fascia in prostates of different weights. Anatomic study applied to radical prostatectomy

PURPOSE

To evaluate the structure of the endopelvic fascia in prostates of different weights.

METHODS

We studied 10 patients with BPH (prostates> 90 g); 10 patients with prostate adenocarcinoma (PAC) (prostates< 60 g) and five young male cadavers (control group). During the surgery a small sample of endopelvic fascia was obtained. We analyzed elastic fibers, collagen and smooth muscle. The stereological analysis was done with the Image Pro and Image J programs. Means were statistically compared using the one-way ANOVA with the Bonferroni test and a p<0.05 was considered statistically significant.

RESULTS

The mean of the prostate weight was 122 g in BPH patients, 53.1g in PAC patients and 18.6g in control group. Quantitative analysis documented that there are no differences (p=0.19) in Vv of elastic fibers and in Vv of type III collagen (p=0.88) between the three groups. There was a significant difference (p=0<0.0001) in the quantification of SMC in patients with prostates > 90 g (mean=9.61%) when compared to patients with prostates < 60 g (mean=17.92%) and with the control group (mean=33.35%).

CONCLUSION

There are differences in endopelvic fascia structure in prostates> 90 g, which can be an additional factor for pre-operatory evaluation of radical prostatectomy.

MiR-133 modulates TGF-β1-induced bladder smooth muscle cell hypertrophic and fibrotic response: implication for a role of microRNA in bladder wall remodeling caused by bladder outlet obstruction

Bladder outlet obstruction (BOO) evokes urinary bladder wall remodeling significantly, including the phenotype shift of bladder smooth muscle cells (BSMCs) where transforming growth factor-beta1 (TGF-β1) plays a pivotal role given the emerging function of modulating cellular phenotype. miR-133 plays a role in cardiac and muscle remodeling, however, little is known about its roles in TGF-β1-induced BSMC hypertrophic and fibrotic response. Here, we verified BOO induced bladder wall remodeling and TGF-β1 expression mainly located in bladder endothelium. Furthermore, we uncovered miR-133a/b expression profile in BOO rats, and then explored its regulated effects on BSMCs' phenotypic shift. Our study found that miR-133 became down-regulated during rat bladder remodeling. Next, we sought to examine whether the expression of miR-133 was down-regulated in primary BSMCs in response to TGF-β1 stimulation and whether forced overexpression of miR-133 could regulate profibrotic TGF-β signaling. We found that stimulation of BSMCs with exogenous TGF-β1 of increasing concentrations resulted in a dose-dependent decrease of miR-133a/b levels and transfection with miR-133 mimics attenuated TGF-β1-induced α-smooth muscle actin, extracellular matrix subtypes and fibrotic growth factor expression, whereas it upregulated high molecular weight caldesmon expression compared with the negative control. Also, downregulation of p-Smad3, not p-Smad2 by miR-133 was detected. Additionally, miR-133 overexpression suppressed TGF-β1-induced BSMC hypertrophy and proliferation through influencing cell cycle distribution. Bioinformatics analyses predicted that connective tissue growth factor (CTGF) was the potential target of miR-133, and then binding to the 3'-untranslated region of CTGF was validated by luciferase reporter assay. These results reveal a novel regulator for miR-133 to modulate TGF-β1-induced BSMC phenotypic changes by targeting CTGF through the TGF-β-Smad3 signaling pathway. A novel antifibrotic functional role for miR-133 is presented which may represent a potential target for diagnostic and therapeutic strategies in bladder fibrosis.

Congenital genitourinary abnormalities in children with Williams-Beuren syndrome

OBJECTIVE

Williams-Beuren syndrome (WBS) is an autosomal dominant disorder caused by a gene deletion on chromosome 7q11.23. Patients with WBS usually show a group of features such as developmental delay, cardiovascular anomalies, mental retardation, and characteristic facial appearance. Abdominal wall defects, external genitalia anomalies, and structural abnormalities of the urinary tract have been scarcely evaluated and were the focus of our study.

MATERIALS AND METHODS

We prospectively evaluated 41 boys and 38 girls with WBS, with a mean age of 8.8 ± 4.1 (range 3-19 years). All patients were examined for the evaluation of inguinal and umbilical hernias and genital anomalies. All patients were offered a radiological evaluation, including urinary tract ultrasound, voiding cystourethrogram, and dimercaptosuccinic acid renal scintigraphy (DMSA scan).

RESULTS

Of the 41 boys, 30 (73.1%) had abnormalities on physical examination, including bilateral undescended testis in 13 (31.7%), retractile testis in four (9.7%), hypospadias in four (9.7%), and unilateral cryptorchidism in three (7.3%) patients. Of the 38 female subjects, 17 (44.7%) had at least one abnormality, including umbilical hernia in 11 (28.9%), unilateral inguinal hernia in four (10.5%), and bilateral inguinal hernia in three (7.8%) patients. Uroradiological abnormalities were found in 41 patients (51.9%). On sonography, six (7.6%) patients had unilateral hydronephrosis, three (3.8%) had a duplicated collecting system, and two (2.5%) had kidney stones. On DMSA, performed in 36 patients, four (11.1%) had unilateral renal scarring and two (5.5%) had bilateral renal scarring. Cystourethrography was obtained from 56 patients, of whom 27 (48.2%) had bladder diverticulum, 18 (32.1%) had bladder wall trabeculation, and three (5.3%) had vesicoureteral reflux. We found no association of urological abnormalities with cardiovascular defects.

CONCLUSIONS

Patients with WBS have a high prevalence of abdominal wall, external genitalia, and urological abnormalities, emphasizing the importance of proper physical examination and radiological investigation in this population.

Structural analysis of testicular appendices in patients with cryptorchidism

OBJECTIVES

Report the incidence and structure of testicular appendices (TAs) in patients with cryptorchidism, comparing their incidence with epididymal anomalies (EA) and patency of the vaginal process (PVP) and analyzes the structure of TAs.

MATERIAL AND METHODS

We studied 72 testes of patients with cryptorchidism (average of 6 years), and 8 testes from patients with hydroceles (average of 9 years). We analyzed the relations among the testis, epididymis and PVP and prevalence and histology of the TAs. The appendices of 10 patients with cryptorchidism and 8 with hydrocele were dissected and embedded in paraffin and stained with Masson trichrome; Weigert and Picro-Sirius Red with polarization and immunohistochemistry analysis of the collagen type III fibers to observe collagen. The stereological analysis was done with the software Image Pro and Image J, using a grid to determine volumetric densities (Vv). Means were statistically compared using the ANOVA and unpaired T test (p < 0.05).

RESULTS

Of the 72 testes with cryptorchidism, 20 (27.77%) presented EA, 41 (56.9%) had PVP and 44 (61.1%) had TAs. Of the 44 testes with cryptorchidism and appendices, 30 (68.18%) presented PVP and 11 (25%) presented EA. There was no alteration of the epithelium in the appendices of patients in both groups. Stereological analysis documented the prevalence of ESFs (mean of 1.48%), prevalence of veins (mean of 10.11%) and decrease (p = 0.14) of SMCs in the TAs of patients with cryptorchidism (mean = 4.93%). Collagen III prevailed in the TAs of patients with cryptorchidism.

CONCLUSION

The testicular appendices presented significant structural alteration in the patients with cryptorchidism, indicating that TAs present a structural remodeling.

Mir-29 repression in bladder outlet obstruction contributes to matrix remodeling and altered stiffness

Recent work has uncovered a role of the microRNA (miRNA) miR-29 in remodeling of the extracellular matrix. Partial bladder outlet obstruction is a prevalent condition in older men with prostate enlargement that leads to matrix synthesis in the lower urinary tract and increases bladder stiffness. Here we tested the hypothesis that miR-29 is repressed in the bladder in outlet obstruction and that this has an impact on protein synthesis and matrix remodeling leading to increased bladder stiffness. c-Myc, NF-κB and SMAD3, all of which repress miR-29, were activated in the rat detrusor following partial bladder outlet obstruction but at different times. c-Myc and NF-κB activation occurred early after obstruction, and SMAD3 phosphorylation increased later, with a significant elevation at 6 weeks. c-Myc, NF-κB and SMAD3 activation, respectively, correlated with repression of miR-29b and miR-29c at 10 days of obstruction and with repression of miR-29c at 6 weeks. An mRNA microarray analysis showed that the reduction of miR-29 following outlet obstruction was associated with increased levels of miR-29 target mRNAs, including mRNAs for tropoelastin, the matricellular protein Sparc and collagen IV. Outlet obstruction increased protein levels of eight out of eight examined miR-29 targets, including tropoelastin and Sparc. Transfection of human bladder smooth muscle cells with antimiR-29c and miR-29c mimic caused reciprocal changes in target protein levels in vitro. Tamoxifen inducible and smooth muscle-specific deletion of Dicer in mice reduced miR-29 expression and increased tropoelastin and the thickness of the basal lamina surrounding smooth muscle cells in the bladder. It also increased detrusor stiffness independent of outlet obstruction. Taken together, our study supports a model where the combined repressive influences of c-Myc, NF-κB and SMAD3 reduce miR-29 in bladder outlet obstruction, and where the resulting drop in miR-29 contributes to matrix remodeling and altered passive mechanical properties of the detrusor.

Stereological and biochemical analysis of the urethral edges in patients submitted to end-to-end anastomosis for bulbar urethral stricture

PURPOSE

To study the morphologic alterations in the proximal and distal urethral edges from patients submitted to end-to-end bulbar urethroplasty.

MATERIALS AND METHODS

We analyzed 12 patients submitted to anastomotic urethroplasty to treat bulbar strictures less than 2.0 cm in length. After excision of the fibrotic segment to a 28Fr urethral caliber, we obtained biopsies from the spongious tissue of the free edges (proximal: PROX and distal: DIST). Controls included normal bulbar urethras obtained from autopsies of 10 age matched individuals. The samples were histologically processed for smooth muscle cells (SMC), elastic system fibers and collagen. Stereological analysis was performed to determine the volumetric density (Vv) of each element. Also, a biochemical analysis was performed to quantify the total collagen content.

RESULTS

Vv of SMC was reduced in PROX (31.48 ± 7.01 p < 0.05) and similar in DIST when compared to controls (55.65 ± 9.60%) with no statistical difference. Elastic fibers were increased in PROX (25.70 ± 3.21%; p < 0.05) and were similar to controls in DIST (15.87 ± 4.26%). Total collagen concentration in PROX (46.39 ± 8.20 µg/mg), and DIST (47.96 ± 9.42 µg/mg) did not differ from controls (48.85 ± 6.91 µg/mg). Type III collagen was similarly present in all samples.

CONCLUSIONS

After excision of the stenotic segment to a caliber of 28Fr, the exposed and macroscopically normal urethral edges may present altered amounts of elastic fibers and SMC, but are free from fibrotic tissue. When excising the peri-stenotic tissue, the surgeon should be more careful in the proximal end, which is the most altered.

Advances in biomimetic regeneration of elastic matrix structures

Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures.

Amitriptyline aggravates the fibrosis process in a rat model of infravesical obstruction

Infravesical obstruction (IVO) secondary to benign prostatic hypertrophy can affect up to 50% of men over 50 years old and may cause serious and irreversible alterations throughout the urinary tract, especially in the bladder. Therapeutic approaches are currently limited. Amitriptyline has recently been described as an analgesic, anti-inflammatory and myorelaxant in some experimental models. The objective of this study was to investigate the effects of amitriptyline hydrochloride on the process of fibrosis in a bladder outlet obstruction model in rats. Male Wistar rats were subjected to IVO and studied at intervals of 1 and 14 days postprocedure. The rats were randomly divided into five groups: sham, IVO1-T, IVO1-NT, IVO14-T and IVO14-NT. Bladder tissue was processed for histopathology, immunohistochemistry and RT-PCR. The IVO14 groups presented bladder fibrosis, smooth muscle cell hypertrophy and bladder wall thickening. The IVO14-T group demonstrated a higher intensity of fibrosis, higher macrophage infiltration rate and higher gene expression of Transforming growth factor (TGF) Tgf-β1. Thus this data shows that in this experimental mode amitriptyline had an amplifying effect on the process of fibrosis as a whole.

Altered bladder function in elastin-deficient mice at baseline and in response to partial bladder outlet obstruction

OBJECTIVE

• To examine functional and molecular changes of the bladders from elastin-haploinsufficient mice (Eln(+/-) ) at baseline as well as in response to partial bladder outlet obstruction (pBOO).

MATERIALS AND METHODS

• Female Eln(+/-) and wild type (Wt) mice (3-4 months old) were studied. • The bladder elastin content was quantified by measuring desmosine. • Mice were divided into two groups to undergo surgery to create pBOO or to undergo sham surgery. Three days after surgery, bladder function was evaluated by in vivo cystometry, and the contractile response of bladder strips exposed to electrical field stimulation (EFS) and carbachol was examined by ex vivo myography.

RESULTS

• The Eln(+/-) -sham mice had a 33.6% decrease in bladder elastin compared with Wt-sham mice. • Cystometry showed significantly decreased bladder compliance and capacity in Eln(+/-) -sham vs Wt-sham mice; pBOO increased bladder compliance and capacity to a greater extent in Eln(+/-) mice compared with Wt mice. • Bladder strips from Eln(+/-) -sham mice showed a significantly heightened contractile response to both EFS and carbachol compared with Wt-sham mice. • A significantly increased contractile response to carbachol was detected in Wt-pBOO vs Wt-sham but not between Eln(+/-) -pBOO and Eln(+/-) -sham mice.

CONCLUSION

• The results that elastin-deficient mice had decreased bladder compliance and capacity and increased bladder contractility; and that Wt-pBOO mice showed an enhanced contractile response to carbachol, but Eln(+/-) -pBOO mice did not, suggest that elastin is critical for normal bladder function and is involved in bladder response to pBOO.

Effect of Partial Bladder Outlet Obstruction on the Morphology of Elastin in Rabbit Bladder Smooth Muscle

OBJECTIVES

Elastin, in association with collagen, allows the body's organs to stretch and relax. Collagen and elastin, the major components of connective tissue, are present throughout the bladder wall and are intimately related to bladder compliance. The present study was undertaken to evaluate elastin morphologically using immunostaining and electron microscopy in the rabbit model of partial bladder outlet obstruction (PBOO).

METHODS

Four groups of Japanese white rabbits underwent either PBOO by mild ligation of the urethra (2- and 4-week PBOO) or no obstruction (2- and 4-week sham). Histopathological examination was performed by Elastica van Gieson staining, scanning electron microscopy, transmission electron microscopy, and ultra-high voltage electron microscopy. The number of pixels representing elastin fibers in computerized images was analyzed using Adobe Photoshop Version 2.0.

RESULTS

Bladder weight significantly increased after PBOO. Increase in the thickness of the bladder wall was observed after obstruction on histopathological examination. On scanning electron microscopy, elastin was very thick and was found in large configurations. 3-D analysis using electron microscopic tomography revealed that elastic fibers in the bladder had a coil-like appearance in the muscle layer, with each fiber composed of several fibrils. Such structures may be closely related to the physiological function of the bladder.

CONCLUSION

Elastin in the bladder assumes the form of a coil during micturition. We examined that the increase in elastin makes it difficult for elastin to stretch linearly resulting in reduced elasticity. This change may be one of the factors involved in the decrease in compliance mediated by PBOO.

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

We have demonstrated that bladder wall tissue in spinal cord injury (SCI) rats at 10 days post-injury is more compliant and accompanied by changes in material class from orthotropic to isotropic as compared to normal tissue. The present study examined the long-term effects (3-, 6-, and 10-weeks) post-SCI on the mechanical properties of bladder wall tissues, along with quantitative changes in smooth muscle orientation and collagen and elastin content. Bladder wall compliance (defined as det(F) - 1 under an equi-biaxial stress state of 100 kPa, where F is the deformation gradient tensor) was found to be significantly greater at 3- and 6-weeks (0.873 +/- 0.092 and 0.864 +/- 0.112, respectively) when compared to the normal bladders (0.260 +/- 0.028), but at 10 weeks the compliance reduced (0.389 +/- 0.061) to near that of normal bladders. This trend in mechanical compliance closely paralleled the collagen/elastin ratio. Moreover, changes in material class, assessed using a graphical technique, correlated closely with quantitative changes in smooth muscle fiber orientation. The results of the present study provide the first evidence that, while similarities exist between acute and chronic responses of the urinary bladder wall tissue to SCI, the overall alterations are distinct, result in profound and complex time dependent changes in bladder wall structure, and will lay the basis for simulations of the bladder wall disease process.

Stereological study of collagen and elastic system in the detrusor muscle of bladders from controls and patients with infravesical obstruction

OBJECTIVE

Compare detrusor muscle of normal and patients with infravesical obstruction, quantifying the collagen and elastic system fibers.

MATERIALS AND METHODS

We studied samples taken from bladders of 10 patients whose ages ranged from 45 to 75 years (mean = 60 years), who underwent transvesical prostatectomy for treatment of BPH. Control material was composed of 10 vesical specimens, removed during autopsies performed in cadavers of accident victims, with ages between 18 and 35 years (mean = 26 years).

RESULTS

The results of collagen and elastic fibers quantification (volumetric density) demonstrated the following results in percentage (mean +/- standard deviation): collagen in BPH patients = 4.89 +/- 2.64 and 2.32 +/- 1.25 in controls (p < 0.0001), elastin in BPH patients = 10.63% +/- 2.00 and 8.94% +/- 1.19 in controls (p < 0.0001).

CONCLUSION

We found that the components of connective tissue, collagen and elastic system fibers are increased in the detrusor muscle of patients with infravesical obstruction, when compared to controls.

Review: Tissue Engineering of the Urinary Bladder: Considering Structure-Function Relationships and the Role of Mechanotransduction

A variety of conditions encountered in urology result in bladder dysfunction and the need for bioengineered tissue substitutes. Traditionally, a number of synthetic materials and natural matrices have been used in experimental and clinical settings. However, the production of functional bladder tissue replacements remains elusive. The urinary bladder sustains considerable structural deformation during its normal function and represents an ideal model tissue in which to study the effects of biomechanical simulation on tissue morphogenesis, differentiation, and function. However, the actual role of mechanical forces within the bladder has received little attention. A strategy in which in vitro-generated tissue constructs are conditioned by exposure to the same mechanical forces as they would encounter in vivo could potentially be used both in the development of functional tissue replacements and to further study the role of biomechanical signalling. The purpose of this review is to examine the role and structure-function relationship of the urinary bladder and, through consultation of the literature available on mechanotransduction and tissue engineering of alternative tissues, to determine the factors that need to be considered when biomechanically engineering a functional bladder.

Elastin metabolism in pelvic tissues: is it modulated by reproductive hormones?

OBJECTIVE

The purpose of this study was to investigate the effect of relaxin on extracellular matrix protein expression in pelvic fibroblasts that were cultured from women with stress urinary incontinence compared with asymptomatic control subjects.

STUDY DESIGN

Periurethral vaginal wall fibroblasts from premenopausal women with stress urinary incontinence and continent women (in both the proliferative and secretory phase of the menstrual cycle) were stimulated with increasing concentrations of relaxin (0-500 ng/mL). The supernatant was sampled for matrix metalloproteinase-2 and -9 by zymography. Tissue inhibitors of metalloproteinase-1 and -2 and alpha-1 antitrypsin were evaluated with Western blot. Total elastase activity was measured by generation of free amino groups from succinylated elastin. Increasing concentrations of alpha-1 antitrypsin were added to cell lysate to evaluate total elastase activity inhibition.

RESULTS

Proliferative-phase stress urinary incontinence fibroblasts demonstrated an increase in matrix metalloproteinase-2 and no change in matrix metalloproteinase-9 and tissue inhibitors of metalloproteinase-1 and -2 expressions with increasing relaxin concentrations. Cells from control subjects showed increased expression of matrix metalloproteinase-2 and -9, but no change in tissue inhibitors of metalloproteinases. Secretory-phase stress urinary incontinence fibroblasts showed no response in matrix metalloproteinase or tissue inhibitors of metalloproteinase expressions with relaxin stimulation. Secretory-phase control fibroblasts reacted by increasing matrix metalloproteinase-2 and -9 and tissue inhibitors of metalloproteinase-2. With respect to total elastase activity and alpha-1 antitrypsin expression, increasing doses of relaxin appear to increase elastolytic activity in stress urinary incontinence cells by decreasing the expression of alpha-1 antitrypsin in proliferative phase cells or increasing the total elastase activity in secretory phase cells. Fibroblast total elastase activity was inhibited by increasing concentrations of alpha-1 antitrypsin.

CONCLUSION

Elastase activity appears to be increased in relaxin-stimulated stress urinary incontinence fibroblasts by either decreased inhibitor (alpha-1 antitrypsin) production or increased elastase activity.

ELASTIN CONTENT OF THE RENAL PELVIS AND URETER DETERMINES POST-PYELOPLASTY RECOVERY

PURPOSE

We evaluated the collagen-to-smooth muscle tissue matrix ratio and percentage of elastin in the renal pelvis, ureteropelvic junction (UPJ) and ureter, and compared these findings with the degree of obstruction, patient age and post-pyeloplasty renal recovery.

MATERIALS AND METHODS

We analyzed histological sections from 75 patients with UPJ obstruction. Nine patients were excluded owing to bilateral UPJ obstruction and an improper specimen. We divided the specimen obtained from pyeloplasty into 3 parts, namely the renal pelvis above the obstruction, the obstructed UPJ portion and the ureter below the obstruction. To examine the collagen and smooth muscle, sections were stained using Masson's trichrome, and elastic van Giesson stain was used for elastin, smooth muscle and collagen. Collagen, smooth muscle and elastin populations were identified, and the tissue matrix ratio and percentage of elastin were calculated by color image analysis.

RESULTS

In patients with lower ratios of collagen-to-smooth muscle in the UPJ proper hydronephrosis was more improved postoperatively (p = 0.049). In patients with a lower percentage of elastin in the renal pelvis, UPJ and ureter hydronephrosis was more improved postoperatively (p <0.0001).

CONCLUSIONS

Because the UPJ portion was resected during pyeloplasty, the renal pelvis and the ureter remaining after pyeloplasty are likely to be related to improved hydronephrosis. A higher percentage of elastin in the renal pelvis and ureter contributes to inelasticity and low compliance, and results in a slower recovery from hydronephrosis after pyeloplasty.

Altered bladder function in transgenic mice expressing rat elastin

The elasticity of tissues subjected to repeated deformation is provided by the presence of elastic fibers in the extracellular matrix (ECM). The most abundant component of elastic fibers is elastin, whose soluble precursor is tropoelastin. To establish the role elastin plays in the bladder, this study describes the biosynthetic, histologic, and physiologic consequences of expression of an isoform of rat tropoelastin in transgenic mouse bladder. The polymerase chain reaction (PCR) was used to determine expression of a rat tropoelastin minigene in transgenic mice. Histochemical methods were used to demonstrate changes in elastic fibers in frozen sections of bladder. Cystometric analysis was carried out in transgenic and non-transgenic mice, prior to and after 3 weeks of partial outlet obstruction. The PCR assay demonstrated that bladder tissue of transgenic mice expressed rat tropoelastin mRNA, whereas non-transgenes did not. Increased deposition of elastic fibers was demonstrated with the Verhoeff-van Gieson stain. Bladders of transgenic animals were more compliant than bladders of their non-transgenic littermates. Partial outlet obstruction resulted in increased bladder volume and more compliant bladders in non-transgenic mice. In contrast, the bladder volume and compliance in transgenes was almost unchanged by obstruction. This study demonstrates that normal elastic fiber assembly is prerequisite for the compliant properties of the bladder wall. Moreover, the response of the bladder to obstruction is critically influenced by elastin synthesis.

Role of type III collagen in bladder filling

The function of the urinary bladder is to store urine at low pressure and expel it periodically. To accomplish this, it must have the appropriate structural properties to accommodate slow but continuous volume changes. While much is presently known about the functional measurements of compliance, relatively little is known about the structural basis of compliance. In the present study, immunohistochemistry has been used to localize type III collagen fibers in the bladder wall at different intravesical volumes. To improve the resolution of these fibers, confocal microscopy was utilized to determine the changes in type III collagen fiber orientation and correlate them with the degree of mechanical distension of the bladder wall at partial and full capacity. We demonstrate that there were significant changes in both the orientation and conformation of type III collagen fibers during bladder filling. These observations support the view that volume accommodation in the bladder is achieved by changes in the arrangement of type III collagen. These data suggest that abnormal deposition or arrangement of type III collagen fibers can have an impact on normal bladder function.

The production of nerve growth factor by human bladder smooth muscle cells in vivo and in vitro

OBJECTIVE

To measure the concentrations of nerve growth factor (NGF) in tissue biopsies taken from subjects with a normal bladder and from patients diagnosed to have idiopathic detrusor instability (associated with a reduction in the density of motor nerves), and to use an in vitro model to study the mechanisms of NGF expression.

MATERIALS AND METHODS

Biopsy specimens were obtained during endoscopic and open surgery from patients undergoing routine bladder surgery. The patients were divided into two categories based upon urodynamic characterization. The NGF content in samples from 11 normal bladders and seven idiopathic unstable bladders were measured using an enzyme-linked immunosorbent assay. The mechanisms influencing net NGF production were explored using detrusor cells in vitro.

RESULTS

The mean (SEM) NGF content was significantly higher in unstable tissues, at 0.96 (0.05) pg/microg protein, than in the normal bladder, at 0.53 (0.05) pg/microg protein. In the cell model, acetylcholine (10 micromol/L), noradrenaline (1 and 10 micromol/L) and ATP (1 micromol/L) caused a significant increase in net NGF production; acetylcholine at 1 micromol/L had no effect. Direct stimulation of protein kinase C (PKC) by phorbol ester (33 ng/mL) or elevation of cAMP using forskolin (10 micromol/L) increased NGF, suggesting that at least two intracellular pathways (PKC- and PKA-dependent) are involved. The expression of c-Fos was increased by phorbol 12-myristate 13-acetate added before NGF, suggesting that c-Fos may be involved in regulating NGF production.

CONCLUSION

These data suggest a role for NGF in the physiology and pathophysiology of the human bladder, and indicate some of the possible mechanisms which might regulate NGF production.

Focal changes in nerve, muscle and connective tissue in normal and unstable human bladder

OBJECTIVE

To compare and quantify, in a morphological study, the changes that occur in the connective tissue elements (elastin and collagen), muscle fibre diameters and nerve densities between normal, idiopathic and neuropathic bladders.

MATERIALS AND METHODS

Bladder tissue was obtained from 27 patients undergoing cystectomy for carcinoma, from 12 with idiopathic instability and from seven neuropathic patients who were undergoing ileocystoplasty. A combination of histochemical and immunohistochemical techniques were used to detect detrusor muscle, connective tissue and nerve profiles in the bladder tissue.

RESULTS

In both idiopathic and neuropathic bladder tissue the structural changes were highly punctate. From the density of nerve profiles, three areas were defined: (i) apparently unaffected normal fascicles with a high density of nerves, no hypertrophy of the muscle and no infiltration of elastin and collagen. The nerve density in these areas was similar to that in normal bladder tissue. (ii) Fascicles with a low density of nerve profiles, muscle hypertrophy but no connective tissue infiltration. (iii) Areas with few nerve profiles, muscle hypertrophy and extensive elastin and collagen infiltration within the fascicles. The mean (sem) density of nerve profiles in control tissue was 752 (53) nerves/mm2 and in the idiopathic bladders was 905 (91), 81 (20) and 74 (38) nerves/mm2 in the three defined areas, respectively. In the neuropathic tissues the nerve profile densities were 672 (249), 57 (23) and 37 (28) nerves/mm2, respectively. Fibre diameter, elastin and collagen content and nerve density were measured in normal and unstable bladder tissue using these three defined areas. The mean (sem) fibre diameter was 6.81 (0.52) in normal bladder; in idiopathic bladder tissue the fibre diameters in the three areas were 6.72 (0.62), 7.06 (0.62) and 7.34 (1.15) micrometer, respectively, and in neuropathic bladders were 6.75 (0.62), 8.24 (0.62) and 9.35 (0.62) micrometer, respectively. The relative areas of elastin were 0.79 (0.70), 0.56 (0.45) and 18.3 (4.1)% for the control, normal and affected areas of the neuropathic bladders, respectively, and the relative areas of collagen were 3.5 (1.3), 6.15 (3.6) and 15.7 (5. 0)%, respectively. The pattern was similar in idiopathic bladders.

CONCLUSION

These observations suggest that the primary defect in the idiopathic and neuropathic bladders is a loss of nerves accompanied by a hypertrophy of the cells. These changes may continue with further hypertrophy of the cells and an increased production of elastin and collagen within the muscle fascicles.

Collagen studies for pediatric ureteropelvic junction obstruction

OBJECTIVES

Ureteropelvic junction (UPJ) obstruction is the most common form of urinary tract obstruction in pediatrics. There is controversy regarding the need for early surgical intervention in many patients with apparent neonatal UPJ obstruction. To demonstrate the differences in type and amount of collagen in adult and pediatric UPJ obstruction, collagen studies were performed.

METHODS

The experimental groups are 9 pediatric patients with UPJ obstruction and 13 adult patients with UPJ obstruction. Six patients with normal UPJ were assigned as controls for each experimental group. The collagen content of UPJ was quantitated by hydroxyproline analysis. Immunohistochemical staining and Western blotting for collagen types I and III were performed.

RESULTS

The collagen content of pediatric UPJ was significantly lower in value than that of adult UPJ (P < 0.05). Immunohistochemical staining revealed that collagen type I was located in interfascicular space and collagen type III was located in intrafascicular space in both age groups. In Western blotting the relative intensity of collagen type III for pediatric UPJ was weaker than that of adult groups.

CONCLUSIONS

These results suggest that a larger series of patients should be examined to determine whether quantitative analysis for collagen types I and III would provide some kind of prognostic test for UPJ outcome in pediatric patients.

Temporal expression of elastic fiber components in bladder development

Fetal and postnatal bovine bladders were examined for expression of elastic fiber components by immunohistochemistry as well as by measurement of steady state mRNA levels. Expression of fibrillin-1, microfibril-associated glycoprotein (MAGP) and elastin during the fetal period were compared with that of postnatal two year old animals (heifers) and adults. Each bladder was separated into two distinct tissue samples: 1) the outer smooth muscle layer (detrusor) and 2) the inner epithelium (urothelium) lined lamina propria (urotherial-lamina propria). Each of these samples was analyzed separately. Distribution of the elastic fiber components, determined by immunohistochemistry with matrix-specific antibodies, was different depending upon the region of the bladder wall examined and its developmental stage. In particular, MAGP and fibrillin-1 were conspicuously present in the urothelium during the later fetal stages. RNA products of elastic fiber genes were detectable both in the detrusor smooth muscle and urothelial-lamina propria fractions. The highest level of expression occurred in the urothelial-lamina propria fraction during the late second-early third trimester. Elastin expression was different from that of MAGP and fibrillin-1. The highest levels of steady-state elastin mRNA occurred at the earliest developmental stages examined and then progressively decreased through term. A high level of elastin expression occurred within the inner or lamina propria layer of the bladder. Since this layer is the functional capacitance layer within the bladder, its flexibility is likely related to the structural integration of elastin and associated microfibrillar components.

Smooth muscle development in the obstructed fetal bladder

OBJECTIVES

To evaluate changes in the smooth muscle and connective tissue development in the obstructed and normal fetal bladder.

METHODS

The smooth muscle and connective tissue composition of 19 fetal urinary bladders, including those of 9 fetuses with anatomic obstruction and 10 controls free of urologic disease, were analyzed by light microscopy and computer-assisted color image analysis.

RESULTS

The bladder wall thickness was markedly increased in obstructed fetuses throughout gestation as compared with that in controls. The disparity in bladder wall thickness increased rapidly during gestation. The percent area density of smooth muscle and connective tissue as well as the ratio of smooth muscle to connective tissue remained the same in the obstructed and normal control fetal bladders.

CONCLUSIONS

Although bladder outlet obstruction is associated with a marked increase in bladder wall thickness, the percent of smooth muscle and connective tissue comprising the mural histology remains relatively constant as compared with that of normal fetal controls. This study suggests that bladder outlet obstruction in the fetus is not associated with excess collagen deposition but rather with an increased amount of bladder with normal cellular content and a concomitant increase in smooth muscle development.

Ureteral cell cultures II: Collagen production and response to pharmacologic agents

PURPOSE

To investigate the in vitro response of ureteral cells to potentially anti-fibrotic agents.

MATERIALS AND METHODS

Cultured human uroepithelial cells, smooth muscle cells, and myofibroblasts were assayed for proliferation and production of collagen types I and III, with and without the presence of hydrocortisone, colchicine, retinol, verapamil, and D-penicillamine.

RESULTS

Hydrocortisone stimulated the proliferation of all three cell types and reduced the type I and type III collagen production by myofibroblasts and smooth muscle cells, respectively. Verapamil enhanced the growth of uroepithelial cells and decreased collagen III production by both uroepithelial and smooth muscle cells. D-penicillamine increased the proliferation of uroepithelial and smooth muscle cells, and inhibited collagen type III production by all three cell types.

CONCLUSIONS

In vitro evidence suggests that hydrocortisone, verapamil, and D-penicillamine have effects that could favorably alter the healing of endoscopic ureteral incisions.

Collagen types I and III localization by in situ hybridization and immunohistochemistry in the partially obstructed young rabbit bladder

PURPOSE

The objective of the study was to investigate the alteration of collagen expression patterns at the transcription and translation levels during partial outlet obstruction and to compare changes in collagen types I and III gene expression, and protein deposition during early and subacute phases of obstruction.

MATERIALS AND METHODS

Following 1, 2, 7, 14 and 21 days of partial bladder obstruction in 2-week-old rabbits bladder tissues were evaluated for collagen types I and III messenger ribonucleic acid localization by in situ hybridization and for protein localization by immunohistochemical study.

RESULTS

There is up regulation of collagen types I and III gene expression after obstruction. Up regulation of collagen gene expression immediately after obstruction is within the lamina propria and the message moves into the muscular layer as obstruction progresses. Protein deposition for both collagen types is analogous to that of gene expression.

CONCLUSIONS

Up regulation of collagen types I and III gene expression, and increased protein deposition after partial obstruction demonstrate that the alteration in collagen synthesis is at least partially transcription regulated. This alteration starts from superficial layers of the bladder wall and becomes deeper as the pathological process progresses.

Congenital bladder obstruction: research strategies and directions

The clinical significance of congenital bladder obstruction is evident to those who deal with children suffering from severe bladder dysfunction and renal failure. It is a lifelong effect often requiring complex surgical reconstruction and renal transplantation. CBO also represents an important pathophysiologic process with relevance to other organ systems in which hypertrophic and fibrotic processes occur. CBO occurs in a dynamic and developing organ in which function and development are interdependent. Alterations of one will induce alterations in the other which then affect the first. Multiple levels of organization are involved and relevant, from the cell to the whole bladder as a part of the organism. Functional and developmental changes have been demonstrated in models of CBO. Much attention has been focused on the connective tissue compartment of the bladder due to its important role in determining bladder compliance characteristics. Preliminary findings suggest that connective tissue remodeling may be affected by alterations in the balance of the regulatory mechanisms of collagen degradation. Further studies should be able to define these alterations and may permit specific modulation of these mechanisms.

Type III collagen decreases in normal fetal bovine bladder development

In normal fetal bovine bladder development we have shown that compliance increases at approximately the same time that urine production first occurs. The late first trimester fetal bladders are relatively stiff with a progressive increase in bladder compliance peaking in the newborn period. From the newborn period through adulthood, we documented a relatively modest decrease in bladder compliance, which may result from the normal aging process. To account for these changes, we have used the bovine model to perform biochemical analyses of the major structural collagens that are found in the bladder (types I and III). These results show that the per cent of type III collagen decreases in the developing bladder from the end of the first trimester until the newborn period. Comparing the newborn bladder to that of a mature adult, we documented a relatively modest increase in the amount of type III collagen. We demonstrated that the ratio of type III-to-type I collagen parallels the normal compliance changes in the developing fetal and mature bovine bladder.

Loss of elasticity in dysfunctional bladders: urodynamic and histochemical correlation

To store adequate volumes of urine at low safe pressures an elastic bladder wall is required. We developed 2 new techniques to measure this ability in our urodynamic laboratory: pressure specific bladder volume, which measures the bladder capacity at a given pressure, and dynamic analysis of bladder compliance. Recently, morphometric and histochemical techniques have been used to determine the relative volume of connective tissue in the bladder wall and to measure the 2 major types (I and III) of collagen within the bladder wall. These methods quantitate 3 parameters of bladder ultrastructure: 1) relative volume of per cent connective tissue, 2) ratio of connective tissue to smooth muscle and 3) ratio of type III to type I collagen. These parameters have been shown to be abnormally elevated in patients with dysfunctional bladders compared to normals. The purpose of the study was to describe the ultrastructural changes that occur in the wall of dysfunctional bladders and to determine the ability of these new urodynamic techniques to detect reliably the clinical effect of these histological changes. The study included 29 consecutive patients with dysfunctional bladders necessitating bladder augmentation. All patients had upper tract changes and/or were incontinent despite treatment with clean intermittent catheterization and pharmacotherapy. Preoperative urodynamic evaluation included measurement of the total bladder capacity, pressure specific bladder volume and dynamic analysis of bladder compliance. Full thickness bladder biopsies were obtained from the dome of the bladders during augmentation. The per cent connective tissue and the ratio of connective tissue to smooth muscle were determined for all patients, and 4 unselected patients from this group had the ratio of type III to type I collagen determined. These histological results were compared to previously established normal values. All 29 patients had a decreased pressure specific bladder volume and dynamic analysis of bladder compliance, whereas 9 had a normal total bladder capacity. The per cent connective tissue was 35.19 +/- 2.84 and ratio of connective tissue to smooth muscle was 0.60 +/- 0.08 compared to normal values of 10.6 +/- 0.020 and 0.131 +/- 0.021, respectively (p < 0.05). Ratio of type III to type I collagen was also significantly elevated in the 4 samples analyzed (30.53 +/- 1.37 versus 24.00 +/- 2.50, p < 0.05). We conclude that poor storage function of poorly compliant bladders is secondary to an alteration in the connective tissue content of the bladder wall. Furthermore, these pathological ultrastructural changes are universally reflected by an abnormally low pressure specific bladder volume and dynamic analysis of bladder compliance. This strong association validates the use of these parameters and suggests that they are urodynamic indicators of a loss of elasticity in bladder wall.

Detrusor Morpho-functional Correlations in Obstruction due to Benign Prostatic Hyperplasia (BPH)

This study was aimed at checking out a possible connection between detrusor primary lesions and clinical and urodynamic data in patients with cervico-prostatic obstruction. 40 patients were evaluated, of whom 32 had symptomatic benign prostatic hyperplasia and 8 were controls. A biopsy of the right side wall of the bladder was carried out. The lesions found (muscular hypertropy, fibroelastosis, alteration of the nerve fibres) in relation to their gravity, correlated to the presumable date when symptoms started and to three data from urodynamic evaluation (significant residual p.m., degree of obstruction according to Schafer's chart, presence of detrusor-motor instability). The interference of physiological ageing on results is not underestimated, but this correlation exists. However, the lack of fine quantitative evaluations of follow-up on the possible reversibility of the same lesions after removal of the obstruction, make it impossible at this stage to state how close the correlation is.

Evidence of possible carcinogenesis during conformational changes in bladder mucosa induced by bladder outlet obstruction

Fourier transform infrared spectroscopy with attenuated total reflectance technique was applied to determine the mucosa on the surface of the rabbit urinary bladder wall before and after obstruction. Several abnormal spectra related to the hydrogen bonding in nucleic acids of protein, previously found in the colon malignant tissues, appeared in the infrared spectra of the obstructed bladder mucosa, which could not be found in normal bladder mucosa. Urinary bladder outlet obstruction seemed to induce carcinogenesis in the obstructed bladder mucosa by forming several infrared spectral abnormalities.