Comparative RNA-sequencing analysis of the prostate in a mouse model of benign prostatic hyperplasia with bladder outlet obstruction

In ageing men, benign prostatic hyperplasia (BPH) is a chronic disease that leads to progressive lower urinary tract symptoms (LUTS) caused by obstruction of the bladder outlet (BOO). Patients with LUTS (such as increased frequency and urgency of urination) and complications of BOO (such as hydronephrosis and bladder stones) are at risk of serious health problems. BPH causes a rapidly rising burden of LUTS far exceeding that of other urological conditions. Treatment outcomes are unsatisfactory for BPH largely due to the lacking of fully understanding of the pathogenesis. Hormonal imbalances related to androgen and oestrogen can cause BPH, but the exact mechanism is still unknown, even the animal model is not fully understood. Additionally, there are no large-scale data to explain this mechanism. A BPH mouse model was established using mixed slow-release pellets of testosterone (T) and estradiol (E2), and we measured gene expression in mouse prostate tissue using RNA-seq, verified the results using qRT‒PCR, and used bioinformatics methods to analyse the differentially expressed genes (DEGs).

Molecular Characterization of Non-Neurogenic and Neurogenic Lower Urinary Tract Dysfunction (LUTD) in SCI-Induced and Partial Bladder Outlet Obstruction Mouse Models

We examined bladder function following spinal cord injury (SCI) by repeated urodynamic investigation (UDI), including external urethral sphincter (EUS) electromyography (EMG) in awake restrained mice and correlated micturition parameters to gene expression and morphological changes in the bladder. A partial bladder outlet obstruction (pBOO) model was used for comparison to elucidate both the common and specific features of obstructive and neurogenic lower urinary tract dysfunction (LUTD). Thirty female C57Bl/6J mice in each group received an implanted bladder catheter with additional electrodes placed next to the EUS in the SCI group. UDI assessments were performed weekly for 7 weeks (pBOO group) or 8 weeks (SCI group), after which bladders were harvested for histological and transcriptome analysis. SCI mice developed detrusor sphincter dyssynergia (DSD) one week after injury with high-pressure oscillations and a significantly increased maximal bladder pressure P_max and were unable to void spontaneously during the whole observation period. They showed an increased bladder-to-bodyweight ratio, bladder fibrosis, and transcriptome changes indicative of extracellular matrix remodeling and alterations of neuronal signaling and muscle contraction. In contrast, pBOO led to a significantly increased P_max after one week, which normalized at later time points. Increased bladder-to-bodyweight ratio and pronounced gene expression changes involving immune and inflammatory pathways were observed 7 weeks after pBOO. Comparative transcriptome analysis of SCI and pBOO bladders revealed the activation of Wnt and TGF-beta signaling in both the neurogenic and obstructive LUTD and highlighted FGF2 as a major upregulated transcription factor during organ remodeling. We conclude that SCI-induced DSD in mice leads to profound changes in neuronal signaling and muscle contractility, leading to bladder fibrosis. In a similar time frame, significant bladder remodeling following pBOO allowed for functional compensation, preserving normal micturition parameters.

Enhanced Hypoxia-Associated Genes in Impaired Contractility From Bladder Outlet Obstruction

BACKGROUND

Hypoxia damages the bladder wall and contributes to the initiation of bladder dysfunction. The change of hypoxia is not well known in impaired bladder contractility caused by long-term bladder outlet obstruction (BOO). We aimed to find out whether hypoxia of bladder tissue is present and what signaling mechanisms are involved in the decompensated bladder in BOO.

METHODS

Twenty 6-week-old female Sprague-Dawley rats were divided into 2 groups, 10 rats each: group 1, sham operation; group 2, BOO for 8 weeks. Eight weeks after the onset of BOO, we did cystometric evaluation and processed polymerase chain reaction (PCR) array for hypoxia pathway using bladder tissues. The PCR array consists of 84 genes known to be involved in the hypoxic response, cell differentiation, and metabolism. We did quantitative PCR (qPCR) and immunohistochemical staining of bladder tissue for hypoxia.

RESULTS

Eight genes were at least 2-fold upregulated and 3 genes were at least 2-fold downregulated in BOO group, compared with the sham operation group. The up-regulated genes (fold change) belonging to the hypoxia-inducible factor (HIF) 1 interactor included Cdkn2a (11.0), and the down-regulated genes belonging to HIF and co-transcription factors included Hif3a (-39.6) and Per1 (-5.1) by BOO. Genes influenced each other by means of TGFβ1, TNF, and TP53.

CONCLUSION

Hypoxia genes were increased in impaired contractility because of long-term BOO. The gene expression profiles could explain the molecular mechanisms of hypoxia in impaired contractility because of long-term BOO.

Increased transient receptor potential canonical 3 activity is involved in the pathogenesis of detrusor overactivity by dynamic interaction with Na+/Ca2+ exchanger 1

Transient receptor potential canonical 3 (TRPC3) is a nonselective cation channel, and its dysfunction is the basis of many clinical diseases. However, little is known about its possible role in the bladder. The purpose of this study was to explore the function and mechanism of TRPC3 in partial bladder outlet obstruction (PBOO)-induced detrusor overactivity (DO). We studied 31 adult female rats with DO induced by PBOO (the DO group) and 40 sham-operated rats (the control group). Here we report that the expression of TRPC3 in the bladder of DO rats increased significantly. Furthermore, PYR10, which can selectively inhibit the TRPC3 channel, significantly reduced bladder excitability in DO and control rats, but the decrease of the bladder excitability of DO rats was more obvious. PYR10 significantly reduced the intracellular calcium concentration in smooth muscle cells (SMCs) in DO and control rats. Finally, Na+/Ca2+ exchanger 1 (NCX1) colocalizes with TRPC3 and affects its expression and function. Collectively, these results indicate that TRPC3 plays an important role in the pathogenesis of DO through a synergistic effect with NCX1. TRPC3 and NCX1 may be new therapeutic targets for DO.

Circular RNA Plasmacytoma Variant Translocation 1 (CircPVT1) knockdown ameliorates hypoxia-induced bladder fibrosis by regulating the miR-203/Suppressor of Cytokine Signaling 3 (SOCS3) signaling axis

The effects of circular RNAs (circRNAs) on bladder outlet obstruction (BOO)-induced hypertrophy and fibrogenesis in rats and hypoxia-induced bladder smooth muscle cell (BSMC) fibrosis remain unclear. This study aimed to determine the regulatory role of circRNAs in the phenotypic changes in BSMCs in BOO-induced rats.circRNAmicroarray and real-time PCR were used to explore differentiated expressed circRNAs. Bioinformatics analyses and dual-luciferase reporter were performed to identify the targets for circRNA PVT1 (circPVT1). BOO was performed to establish a bladder fibrosis animal model. The circPVT1 and suppressor of cytokine signaling 3 (SOCS3) expression levels were upregulated (p = 0.0061 and 0.0328, respectively), whereas the microRNA-203a (miR-203) level was downregulated in rats with bladder remodeling (p=0.0085). Bioinformatics analyses and dual-luciferase reporter assay results confirmed that circPVT1 sponges miR-203 and that the latter targets the 3'-untranslated region of SOCS3. Additionally, circPVT1 knockdown alleviated BOO-induced bladder hypertrophy and fibrogenesis. Furthermore, hypoxia was induced in BSMCs to establish a cell model of bladder fibrosis. Hypoxia induction in BSMCs resulted in upregulated circPVT1 and SOCS3 levels (p = 0.0052) and downregulated miR-203 levels. Transfection with circPVT1 and SOCS3 shRNA ameliorated hypoxia-induced transforming growth factor-β (TGF-β1), TGFβR1, α-smooth muscle actin, fibrotic growth factor, extracellular matrix subtypes, BSMC proliferation, and apoptosis-associated cell injury, whereas co-transfection with miR-203 inhibitor counteracted the effect of circPVT1 shRNA on these phenotypes.These findings revealed a novel circRNA regulator of BOO-associated bladder wall remodeling and hypoxia-induced phenotypic changes in BMSCs by targeting the miR-203-SOCS3 signaling axis.

Genome-Wide Survey for Microdeletions or -Duplications in 155 Patients with Lower Urinary Tract Obstructions (LUTO)

Lower urinary tract obstruction (LUTO) is, in most cases, caused by anatomical blockage of the bladder outlet. The most common form are posterior urethral valves (PUVs), a male-limited phenotype. Here, we surveyed the genome of 155 LUTO patients to identify disease-causing CNVs. Raw intensity data were collected for CNVs detected in LUTO patients and 4.392 healthy controls using CNVPartition, QuantiSNP and PennCNV. Overlapping CNVs between patients and controls were discarded. Additional filtering implicated CNV frequency in the database of genomic variants, gene content and final visual inspection detecting 37 ultra-rare CNVs. After, prioritization qPCR analysis confirmed 3 microduplications, all detected in PUV patients. One microduplication (5q23.2) occurred de novo in the two remaining microduplications found on chromosome 1p36.21 and 10q23.31. Parental DNA was not available for segregation analysis. All three duplications comprised 11 coding genes: four human specific lncRNA and one microRNA. Three coding genes (FBLIM1, SLC16A12, SNCAIP) and the microRNA MIR107 have previously been shown to be expressed in the developing urinary tract of mouse embryos. We propose that duplications, rare or de novo, contribute to PUV formation, a male-limited phenotype.

Partial inhibition of activin receptor-like kinase 4 alleviates bladder fibrosis caused by bladder outlet obstruction

The bladder undergoes profound structural alterations after bladder outlet obstruction (BOO), characterized by hypertrophy of the bladder wall and accumulation of extracellular matrix (ECM). Transforming growth factor-β (TGF-β) has been found to promote fibrosis of the bladder induced by partial bladder outlet obstruction (pBOO). Activin receptor-like kinase 4 (ALK4) is a downstream receptor of the TGF-β superfamily. However, the role of the ALK4-Smad2/3 pathway in the pathogenesis of bladder fibrosis caused by pBOO remains unknown. This study focused on learning the role of ALK4 in the process of bladder fibrosis caused by pBOO. The pBOO mice models showed that ALK4 expression was found to upregulate in the wild-type bladder 6 weeks after pBOO compared to control group. Then, mice with heterozygous knockout of the ALK4 gene (ALK4+/-) were generated. Histological analysis and Western blot (WB) results showed significant suppression of collagen expression in the bladders of ALK4+/- mice after pBOO compared with WT mice. WB also showed that ALK4+/- mice demonstrated significant suppression of phosphorylated Smad2/3 (p-Smad2/3) expression in the bladder 6 weeks after pBOO but not of phosphorylated extracellular signal-regulated kinase, c-Jun N-terminal kinase or protein 38 (p-ERK, p-JNK, p-P38) expression. This effect might have occurred through partial inactivation of the Smad2/3 signaling pathway. In vitro, ALK4 overexpression promoted collagen production in cultured BSMCs and activated the Smad2/3 signaling pathway. Taken together, our results demonstrated that ALK4 insufficiency alleviated bladder fibrosis in a mouse model of pBOO partly by suppressing Smad2/3 activity.

Rare Variants in BNC2 Are Implicated in Autosomal-Dominant Congenital Lower Urinary-Tract Obstruction

Congenital lower urinary-tract obstruction (LUTO) is caused by anatomical blockage of the bladder outflow tract or by functional impairment of urinary voiding. About three out of 10,000 pregnancies are affected. Although several monogenic causes of functional obstruction have been defined, it is unknown whether congenital LUTO caused by anatomical blockage has a monogenic cause. Exome sequencing in a family with four affected individuals with anatomical blockage of the urethra identified a rare nonsense variant (c.2557C>T [p.Arg853^∗]) in BNC2, encoding basonuclin 2, tracking with LUTO over three generations. Re-sequencing BNC2 in 697 individuals with LUTO revealed three further independent missense variants in three unrelated families. In human and mouse embryogenesis, basonuclin 2 was detected in lower urinary-tract rudiments. In zebrafish embryos, bnc2 was expressed in the pronephric duct and cloaca, analogs of the mammalian lower urinary tract. Experimental knockdown of Bnc2 in zebrafish caused pronephric-outlet obstruction and cloacal dilatation, phenocopying human congenital LUTO. Collectively, these results support the conclusion that variants in BNC2 are strongly implicated in LUTO etiology as a result of anatomical blockage.

Functional and molecular evidence for Kv7 channel subtypes in human detrusor from patients with and without bladder outflow obstruction

The aim of the study was to investigate whether Kv7 channels and their ancillary β-subunits, KCNE, are functionally expressed in the human urinary bladder. Kv7 channels were examined at the molecular level and by functional studies using RT-qPCR and myography, respectively. We found mRNA expression of KCNQ1, KCNQ3-KCNQ5 and KCNE1-5 in the human urinary bladder from patients with normal bladder function (n = 7) and in patients with bladder outflow obstruction (n = 3). Interestingly, a 3.4-fold up-regulation of KCNQ1 was observed in the latter. The Kv7 channel subtype selective modulators, ML277 (activator of Kv7.1 channels, 10 μM) and ML213 (activator of Kv7.2, Kv7.4, Kv7.4/7.5 and Kv7.5 channels, 10 μM), reduced the tone of 1 μM carbachol pre-constricted bladder strips. XE991 (blocker of Kv7.1-7.5 channels, 10 μM) had opposing effects as it increased contractions achieved with 20 mM KPSS. Furthermore, we investigated if there is interplay between Kv7 channels and β-adrenoceptors. Using cumulative additions of isoprenaline (β-adrenoceptor agonist) and forskolin (adenylyl cyclase activator) in combination with the Kv7 channel activator and blocker, retigabine and XE991, we did not find interplay between Kv7 channels and β-adrenoceptors in the human urinary bladder. The performed gene expression analysis combined with the organ bath studies imply that compounds that activate Kv7 channels could be useful for treatment of overactive bladder syndrome.

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.

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.

Vascular endothelial growth factor and bladder from a different perspective: not only an angiogenic factor

Angiogenesis has a key role for embryonic development and is crucial in several major diseases. Molecular basis of angiogenesis has been widely investigated (J Biochem Mol Biol. 2006;39:469-478, Oncogene. 2000;19:5598-5605). In this review, vascular endothelial growth factor (VEGF) and related receptors and their key roles in embryonic bladder development are discussed. The normal VEGF expression and related angiogenesis pattern of embryonic bladder are highlighted. The VEGF family especially VEGF-A is the major player in angiogenesis as well as many other angiogenic factors and activates 2 tyrosine kinase receptors, VEGFR-1 and VEGFR-2 (J Biochem Mol Biol. 2006;39:469-478). Besides its worthy role in angiogenesis, VEGF-A also seems to participate in normal bladder development (J Urol. 2007;177:1552-1557, Br J Urol Int. 2006;98:217-225). In previous studies, we have shown that exogenous VEGF or hypoxia-induced endogenous upregulation of this protein accelerates the growth of the bladder by detrusor and urothelium hypertrophy and hyperplasia (J Urol. 2007;177:1552-1557, Br J Urol Int. 2006;98:217-225, Dev Biol. 1997;183:139-149, Neurourol Urodyn. 2004;23:342-348). This abrupt role of VEGF on detrusor muscle through a hypoxic pathway may potentially be a part of the solution for many urologic conditions such as remodeling of detrusor muscle in antenatal bladder outlet obstruction.

Role of angiogenesis in bladder response to partial outlet obstruction

Benign prostatic hyperplasia (BPH) is a disease that has its etiology in the abnormal growth of the adult human prostate gland that accompanies the aging process in men. The symptomatic presentation of this disease, however, is related largely to degenerative changes in the bladder that occur as a result of the increasing urethral resistance and partial bladder outlet obstruction (PBOO) caused by the growing prostate gland. BPH is characterized by bladder hypertrophy, significant decreases in urinary flow and compliance, presence of residual urine after voiding, voiding urgency and incontinence (). Obstructed bladder dysfunction secondary to BPH is a slow, progressive disease that is so strongly associated with human aging that it is an expected occurrence of the male aging process. Although the symptoms of BPH are usually not life threatening, they effect an extremely negative quality of life for men who suffer from them. However, many men delay seeking medical treatment for early BPH since bladder function can remain relatively normal as the hypertrophying bladder initially compensates for the progressive increase in urethral resistance caused by prostatic obstruction. The limited changes in micturition pressure and flow characteristics that occur during compensated function are not usually disabling enough to motivate seeking medical attention, which, often, is not sought until the symptoms become typical of advanced disease. Recent advances in detection methods enable identification of patients with significant BPH during compensation before the bladder becomes dysfunctional (decompensated). A more complete understanding of the disease processes that underlie the loss of bladder function associated with BPH might enable the development of treatments that better protect these early-stage BPH patients from the more debilitating aspects of the disease. This review updates the understanding of obstructive bladder dysfunction via the use of animal models.

Changes of gap junctional cell-cell communication in overactive detrusor in rats

To evaluate the changes in intercellular communication through gap junctions in detrusor overactivity (DO), we studied 23 adult female Wistar rats with DO after partial outflow obstruction (DO group) and 13 sham-operated rats (control group). The two groups were compared by means of urodynamics, light and electron microscopy, expression of Cx40, Cx43, and Cx45 mRNA genes with RT-PCR, Cx43 protein with Western blot analysis, and functional intercellular communication with scrape loading dye transfer (SLDT) and fluorescence recovery after photobleaching (FRAP). The number of gap junctions and the expression of connexin mRNA and Cx43 protein were increased in DO rats, and intercellular communication through gap junctions increased after 6 wk of partial outflow obstruction as assessed with SLDT and FRAP techniques. The findings provide a theoretical rationale for using Cx43 antagonists and gap junction inhibitors in the treatment of patients with overactive detrusor secondary to partial bladder outflow obstruction.

[Inhibition on phenotypic transformation of detrusor smooth muscle cells after bladder outlet obstruction by E2F decoy strategy]

OBJECTIVE

To investigate the inhibitory effect of E2F decoy strategy on the phenotypic transformation of detrusor smooth muscle cells (DSMCs) so as to verify the effect of the E2F decoy strategy in improvement of the bladder function after bladder outlet obstruction (BOO).

METHODS

Rat DSMCs were cultured, underwent cyclic mechanical stretch so as to establish BOO model, and then were divided into 3 groups: E2F-ODN decoy group [transfected with E2F-decoy ODN tagged with carboxy-fluorescein (FAM), a at its 3' end], Mis-decoy group (transfected with mismatch E2F-decoy ODN), and control group (without transfection). Inverted fluorescence microscopy was used to detect the green fluorescence of FAM in the successfully transfected cells. The proliferation of the cells was observed by MTT method. RT-PCR was used to examine the mRNA expression of proliferating cell nuclear antigen (PCNA). Western blotting was used to detect the protein expression of PCNA and cdk2 kinase.

RESULTS

FAM-labeled E2F-ODN was detected stably in the DSMCs of the E2F-ODN decoy group 24 hours after transfection. The proliferation of the DSMCs of the E2F-ODN decoy group was decreased significantly compared with the mismatch E2F-ODN decoy and control groups (both P < 0.01). The mRNA expression of PCNA, protein expression of PCNA and cdk2 kinase of the E2F-ODN decoy group were all significantly lower than those of the other 2 groups (all P < 0.01).

CONCLUSION

E2F-decoy ODN can be transfected and stably expressed in DSMCs. The phenotypic transformation of DSMCs can be successfully inhibited by E2F decoy strategy, which clarifies the potential role of structural stability-based method on improvement of bladder function recovery after BOO.

Age-related changes of P2X(1) receptor mRNA in the bladder detrusor from men with and without bladder outlet obstruction

The urinary bladder purinergic system is reported to change with age and with bladder dysfunction. Here, we examined the expression of purinergic P2X(1) receptors in detrusor and mucosa (urothelium+lamina propria) from male control bladder and investigated age-related P2X(1) receptor mRNA expression in control and obstructed detrusor. Biopsy specimens were obtained at cystoscopy from control patients (n=46, age range 30-86years) and patients diagnosed with outlet obstruction (n=29, 46-88years). Calponin expression (measured by RT-PCR) was similar in control and obstructed detrusor and did not change with age. Quantitative competitive RT-PCR was used to measure P2X(1) receptor and GAPDH mRNA in control and obstructed detrusor. P2X(1) receptor mRNA expression was 9-fold (p<0.0001) higher in the detrusor than in the mucosa. Expression of mRNA for the internal control GAPDH remained stable with age and across control and obstructed detrusor. No difference in P2X(1) receptor expression was observed between control and obstructed detrusor (p=0.35). However, an age-related decrease in P2X(1) mRNA expression was observed in control (n=27; p=0.0054; Spearman coefficient r=-0.520) but not obstructed detrusor (n=19; p=0.093; r=-0.396). Downregulation of P2X(1) mRNA expression might occur as a result of an increased component of neural ATP release in the aging bladder.

Null mutation in macrophage migration inhibitory factor prevents muscle cell loss and fibrosis in partial bladder outlet obstruction

Idiopathic detrusor underactivity (DU) and detrusor decompensation which develops following partial bladder outlet obstruction (pBOO) are both associated with smooth muscle degeneration and fibrosis. Macrophage migration inhibitory factor (MIF), an important mediator of bladder inflammation, has been shown to promote fibroblast survival and muscle death in other tissues. We evaluated the hypothesis that MIF has similar actions in the bladder by studying detrusor responses to pBOO or sham surgery in anesthetized female mice rendered null for the mif gene (MIF KO) and in wild-type (WT) controls, all killed 3 wk after surgery. WT mice revealed intense MIF immunoreactivity in urothelial cells which decreased, without change in overall mif mRNA levels. Stereologically sound quantitative morphometric measurements were performed in the middetrusor region of each bladder. MIF KO bladders were normal in appearance, yet were 30–40% heavier, with increased middetrusor collagen and muscle, compared with WT controls. In WT mice, pBOO increased the collagen-to-muscle ratio 1.9-fold and middetrusor collagen 1.8-fold, while nucleated muscle counts were 22% lower. In MIF KO mice, by contrast, pBOO had no significant effect on any of these parameters. In primary bladder muscle cultures, treatment with rMIF protein increased TUNEL staining, raising the proportion of early and late apoptotic cells on flow cytometry. Our studies implicate MIF in the sequence of events leading to detrusor muscle loss and fibrosis in obstruction. They raise the possibility that strategies designed to antagonize MIF synthesis, release, or biological activity could prevent or delay DU and urinary retention.

Investigation of early protein changes in the urinary bladder following partial bladder outlet obstruction by proteomic approach

We investigated the pathophysiological mechanism by proteomic approach as a possible tool to detect the marker proteins to develop lower urinary tract symptoms following bladder outlet obstruction (BOO). Rats were randomized into 3 groups; control, sham operation and BOO groups. BOO group was divided into 1, 3, and 5 day-group. Conventional proteomics was performed with high resolution 2-D gel electrophoresis followed by computational image analysis and protein identification using mass spectrometry using rat urinary bladders. A comparison of bladder of BOO group with control bladder showed that three proteins of optineurin, thioredoxin and preprohaptoglobin were over-expressed in the bladder of BOO group. In addition, four proteins, such as peroxiredoxin 2, transgelin, hippocampal cholinergic neurostimulating peptide (HCNP) and beta-galactoside-binding lectin, were under-expressed in the bladder of BOO group. These data supported that downregulation of HCNP might make detrusor muscle be supersensitive to acetylcholine, up-regulation of optineurin means the protection of nerve injury, and down-regulation of transgelin means the decreased contractility of detrusor muscle. Beside these proteins, other proteins are related to oxidative stress or have a nonspecific function in this study. However more information is needed in human bladder tissue for clinical usage.

A MALE MURINE MODEL OF PARTIAL BLADDER OUTLET OBSTRUCTION REVEALS CHANGES IN DETRUSOR MORPHOLOGY, CONTRACTILITY AND MYOSIN ISOFORM EXPRESSION

PURPOSE

Mice with gene deletion or targeted over expression are important for understanding the remodeling that follows partial bladder outlet obstruction (PBOO). This condition predominates in males. We produced PBOO in male mice and now report the physiological, histological and molecular consequences.

MATERIALS AND METHODS

Male C57bl/6 mice were surgically obstructed or subjected to sham surgery and unoperated mice served as controls. Four weeks later the bladders were excised and their function was assessed with in vitro whole bladder cystometry. The optimum volume for pressure generation was determined and isometric pressures were measured for field stimulation and depolarization with KCl. Bladder hypertrophy was classified as severe-bladder mass greater than 50 mg or mild-bladder mass less than 50 mg. The percent muscle fraction was determined by histological analyses. The expression of C-terminal (SM1 and SM2) and N-terminal (SM-B and SM-A) isoforms of myosin heavy chain was analyzed by reverse transcriptase-polymerase chain reaction.

RESULTS

Severely hypertrophied bladders had larger optimum volume (p >0.001) and generated less pressure in response to field stimulation (p >0.001) and KCl (p >0.01) with a slower rate of pressure generation than controls or sham operated mice. Increased SM1-to-SM2 and SM-A-to-SM-B ratios were noted in severely obstructed bladders relative to controls or sham operated mice (p <0.05). The muscle fraction decreased slightly in the severely hypertrophied group (p not significant).

CONCLUSIONS

Our male mouse model of PBOO demonstrates an increase in bladder mass, larger capacity and significantly decreased pressure generation in the in vitro whole bladder model. Obstruction induced increases in the expression of C-terminal (SM1) and N-terminal (SM-A) myosin heavy chain isoforms.

Murine in vitro whole bladder model: a method for assessing phenotypic responses to pharmacologic stimuli and hypoxia

AIMS

Recent advances in genetic manipulation have allowed for over expression or deletion of selective genes in mice. This offers urologic investigators new means of understanding bladder function in the context of normal development or the response to outlet obstruction. It is important to correlate any genetic manipulations in mice with specific phenotypic properties such as voiding patterns, or muscle strip physiology. We describe a simple in vivo whole bladder preparation that may be used to study the phenotypic changes in bladder function.

METHODS

Murine bladders were mounted on a 30 gauge needle and mounted in an organ chamber containing a physiologic buffer solution. Passive bladder properties were assessed with cystometry, and active contractile responses were measured in response to electrical field stimulation and agonists. The effects of hypoxia were also studied.

RESULTS

Compliance in the murine bladder is dependent upon actin myosin interactions, and increased in the presence of calcium free buffer and EGTA. The sarcoplasmic reticulum plays a smaller role in the contraction of murine bladder than in other species. Murine bladder smooth muscle demonstrated a remarkable ability to withstand hypoxia.

CONCLUSIONS

This simple model can be adapted to help study the murine bladder smooth muscle phenotype under highly controlled circumstances.

THE MOLECULAR GENETIC BASIS OF MITOCHONDRIAL MALFUNCTION IN BLADDER TISSUE FOLLOWING OUTLET OBSTRUCTION

PURPOSE

Bladder dysfunction following partial outlet obstruction is a frequent consequence of benign prostatic hyperplasia and an increasingly common problem given the aging of the general population. Recent studies from this and other groups have begun to elucidate the molecular bases for the well described physiological malfunctions that characterize this clinical entity. We summarized and synthesized that information.

MATERIALS AND METHODS

Using modern methods of molecular genetics, including real-time polymerase chain reaction, real-time reverse transcriptase-polymerase chain reaction and others, as well as traditional experimental techniques such as electron microscopy we and others examined the transcriptional profile, morphology, etc of bladder smooth muscle mitochondria in experimental models of outlet obstruction.

RESULTS

Data from many studies have demonstrated that aberrant gene expression in the mitochondrial and mitochondria related nuclear genetic systems underlies the loss of compliance and other attributes of bladder dysfunction following outlet obstruction. Such aberrant transcriptional characteristics engender loss of function in the electron transport and oxidative phosphorylation systems. Morphological studies of mitochondria in the animal model systems support this conclusion.

CONCLUSIONS

In large part the loss of function in bladder smooth muscle following outlet obstruction results from the attenuation of mitochondrial energy production. In this article we reviewed and synthesized all available experimental observations relevant to this problem and we suggest future lines of inquiry that should prove fruitful in developing new strategies to treat the condition.

Bladder smooth muscle cell phenotypic changes and implication of expression of contractile proteins (especially caldesmon) in rats after partial outlet obstruction

BACKGROUND

The purpose of the present study was to investigate morphological changes in bladder smooth muscle of rats with partial outlet obstruction. We investigated smooth muscle cell phenotypic changes and implication of synthetic phenotype in contractility decrease and bladder compliance after bladder outlet obstruction.

METHODS

Partial bladder outlet obstruction was introduced in female rats. Bladder were removed at 1, 3, 6, 10 and 20 weeks after the obstruction. Temporal pattern of changes in bladder mass, light microscopic pathogenesis and phenotypic expression of the bladder smooth muscle cells in the electron micrographs were investigated. Expression of contractile protein was also investigated by the immunoblotting method.

RESULTS

Marked increase in bladder mass with marked thickening of smooth muscle layer was observed at 1 week after obstruction. The ratio of myocytes exhibiting contractile and synthetic phenotypes was almost constant until 6 weeks after the obstruction, but thereafter, synthetic phenotypes gradually increased and the ratio (synthetic/contractile phenotype) was 1.5-fold at 20 weeks after the obstruction. Caldesmon was most markedly expressed after the obstruction among contractile proteins examined by the immunoblotting method.

CONCLUSION

Phenotypic changes were confirmed in bladder smooth muscle, and the decrease of the ratio of contractile phenotype was observed after long-term obstruction of the bladder outlet. Among the contractile proteins in the bladder smooth muscle cell, caldesmon was considered a reliable marker for predicting the pathogenetic conditions of the bladder.

Urinary outflow obstruction increases apoptosis and deregulates Bcl-2 and Bax expression in the fetal ovine bladder

During organogenesis, net growth of tissues is determined by a balance between proliferation, hypertrophy, and apoptotic death. Human fetal bladder outflow obstruction is a major cause of end-stage renal failure in children and is associated with complex pathology in the kidney and lower urinary tract. Experimental manipulation of the fetal sheep urinary tract has proved informative in understanding the pathobiology of congenital obstructive uropathy. In this study we used an ovine model of fetal bladder outflow obstruction to examine effects on apoptotic cell death in the developing urinary bladder. While 30 days of obstruction in utero between 75 and 105 days gestation resulted in overall growth of the fetal bladder as assessed by weight, protein, and DNA measurements, we found that apoptosis, as assessed by in situ end-labeling, was up-regulated in fetal bladder detrusor muscle and lamina propria cells and that this was accompanied by a down-regulation of the anti-death protein Bcl-2 and an up-regulation of the pro-death protein Bax. Moreover, activated caspase-3, an effector of apoptotic death, was increased in obstructed bladders. This is the first study to define altered death in an experimental fetal model of bladder dysmorphogenesis. We speculate that enhanced apoptosis in detrusor smooth muscle cells is part of a remodeling response during compensatory hyperplasia and hypertrophy. Conversely, in the lamina propria, an imbalance between death and proliferation leads to a relative depletion of cells.

Cloning of COX4 cDNA from the NZ white rabbit and expression of this gene in bladder smooth muscle following partial outlet obstruction

We cloned and characterized the rabbit COX4 coding sequence, then examined expression of the gene in bladder smooth muscle following partial obstruction of the bladder outlet. Obstruction was done surgically in male NZ white rabbits and bladders procured at 1, 3, 5, 7, and 14 days post-obstruction (two animals/time). RNA, then cDNA, was prepared from smooth muscle from each sample. Cloning was done from cDNA by PCR. COX4 mRNA in smooth muscle was defined by real-time RT-PCR, using cDNA from bladder samples. The rabbit COX4 coding sequence specifies a protein of 169 amino acids, including a membrane transit sequence for mitochondrial (mt) entry. Expression of COX4 in bladder smooth muscle decreased by 80% in the first day post-obstruction and remained low through 14 days post-obstruction. Cytochrome oxidase activity decreased sharply in the first 3 days post-obstruction in smooth muscle, in concert with COX4 transcript levels. Partial outlet obstruction of the rabbit urinary bladder results in attenuation in smooth muscle of mRNA synthesis from the COX4 gene. In turn, this results in attenuated activity of mt electron transport due to limited availability of nucleus-encoded components required for the assembly of cytochrome oxidase.

Infravesical obstruction in aromatase over expressing transgenic male mice with increased ratio of serum estrogen-to-androgen concentration

PURPOSE

The potential role of estrogen in the development of infravesical obstruction is still unresolved. Aromatase over expressing transgenic mice provide a novel instrument for investigating the consequences of prolonged systemic or local increases in endogenous estrogen concentrations. Two aromatase over expressing transgenic mouse strains with different prostatic phenotypes (reduced and normal size, respectively) were compared in urodynamic studies with each other and with the wild-type strain.

MATERIALS AND METHODS

The bladder and urethra were exposed in adult male wild-type or transgenic mice. High frequency oscillations of intraluminal bladder pressure and flow rate from the distal urethra were simultaneously recorded with the mice under anesthesia.

RESULTS

No changes were observed in voiding in MMTV-arom+ mice. These mice are known to have only slightly elevated estradiol concentrations in serum, suggesting a localized increase in estrogen production. In AROM+ mice the aromatase gene was detected in several organs, including the testis and bladder. These mice are known to have markedly increased estrogen and decreased serum androgen concentrations, and reduced prostate size. Compared with wild-type mice AROM+ mice showed higher mean maximal bladder pressure plus or minus standard deviation (33.1 +/- 6.4 versus 25.6 +/- 4.8 mm. Hg, p = 0.046) and decreased mean maximal flow rate (3.1 +/- 1.6 versus 17.7 +/- 5.4 ml. per minute, p <0.0001), consistent with the presence of the infravesical obstruction. Morphologically the proximal rhabdosphincter in AROM+ mice showed atrophy (relative mean thickness 0.005 +/- 0.015 versus 0.013 +/- 0.002 mm., p <0.0001).

CONCLUSIONS

Activation of the aromatase gene during an earlier developmental stage under the ubiquitin C promoter and highly elevated serum estrogen concentrations may explain the differences in voiding and prostate size in the AROM+ mouse strain.

Contractile protein expression in bladder smooth muscle is a marker of phenotypic modulation after outlet obstruction in the rabbit model

PURPOSE

We determined changes in contractile protein expression before and after the relief of partial bladder outlet obstruction in the rabbit model and assessed their potential role as predictors of recovery.

MATERIALS AND METHODS

We examined the ratio of the smooth muscle myosin heavy chain isoforms SM2-to-SM1, caldesmon isoform expression and bladder function in obstructed and unobstructed adult rabbit bladders. Cystometry, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis were done to determine changes in bladder function and contractile protein expression.

RESULTS

Overall we observed significant correlation of bladder weight with the SM2-to-SM1 ratio (p <0.05). Regardless of the duration of obstruction (up to 10 weeks) the ratio appeared to stabilize around a value comparable to that in fetal rabbit smooth muscle cells, suggesting a reversal of SM2 and SM1 expression to a level similar to that at the fetal stage. The pattern of h and l-caldesmon isoform expression showed an increase in l-caldesmon expression in obstructed bladders. Except for decreased leak point pressure in the obstructed group we noted no statistically significant urodynamic changes in bladder capacity or compliance.

CONCLUSIONS

There is significant correlation of bladder weight, which is the best known marker of obstruction, with the SM2-to-SM1 ratio. The myosin heavy chain isoform expression ratio appears to be an indicator of phenotypic modulation in bladder smooth muscle before and after the relief of bladder outlet obstruction. Thus, it may be useful as a marker of bladder dysfunction and predictor of functional recovery. Regression to a fetal pattern of protein expression may suggest irreversible damage to smooth muscle cells, possibly limiting recovery.

Review article: The molecular era of bladder research. Transgenic mice as experimental tools in the study of outlet obstruction

PURPOSE

To review the crucial role of transgenic mice as experimental tools in the study of outlet obstruction.

MATERIALS AND METHODS

We reviewed the literature for studies that have used mice as models for outlet obstruction.

RESULTS

The combination of genetic manipulations and cellular physiology defines state-of-the-art experiments that explore the reciprocal mesenchymal-epithelial interactions that regulate bladder cell mechanisms.

CONCLUSIONS

The use of transgenic mice in bladder research has provided important data with respect to the molecular signals that drive bladder development, homeostasis, and the response to injury.

Mitochondrial DNA deletion of the human detrusor after partial bladder outlet obstruction-correlation with urodynamic analysis

OBJECTIVES

To investigate mitochondrial DNA (mtDNA) mutations in human detrusor after partial bladder outlet obstruction (BOO) and correlate the findings with the results of urodynamic studies.

METHODS

Sixty-two male patients with and without BOO were recruited and assessed by the International Prostate Symptom Score, a quality-of-life assessment index, and sonography. The severity of partial BOO was determined by pressure-flow study with an International Continence Society (ICS) nomogram. Random detrusor biopsies obtained cystoscopically were analyzed by polymerase chain reaction (PCR) techniques to detect possible mtDNA deletions. Primer-shift PCR and DNA sequencing were then performed to characterize specific mtDNA deletions. A semiquantitative PCR method was used to determine the proportion of the deleted mtDNA in detrusor. Finally, the mtDNA deletion and the urodynamic results were compared statistically.

RESULTS

A 4977-bp mtDNA deletion was identified in the human detrusor. Its incidence and proportion were found to increase after partial BOO (P = 0.005 and 0.012, respectively). The incidence of the mtDNA deletion was 4.2% (1 of 24) in the unobstructed group, 27.8% (5 of 18) in the equivocal group, and 40% (8 of 20) in the obstructed group. The mean proportion of the 4977-bp deleted mtDNA was 23.7 and 12.7 times higher in the obstructed and equivocal groups, respectively, compared with that of the unobstructed group.

CONCLUSIONS

We found mtDNA with the 4977-bp deletion in human detrusor and an increase of this deletion after partial BOO. This molecular change might account for the previous observations of mitochondrial functional impairment and voiding dysfunction after partial BOO.

Mitochondrial and mitochondrial-related nuclear genetic function in rabbit urinary bladder following reversal of outlet obstruction

Partial outlet obstruction of the rabbit urinary bladder causes increased tissue hypertrophy and decreased contractility of that organ; we showed that, in an experimental rabbit model, both correlate closely with alterations in the status and expression of mitochondrial (mt), and mt-related nuclear, genetic parameters in bladder smooth muscle. Here we investigate the rate and overall level of recovery of mt and nuclear genetic function following reversal of outlet obstruction in the same animal model. Release from outlet obstruction at 28 days resulted in improvement in both level of hypertrophy and contractile function in all bladders studied. However, bladders fell into two groups based on whether relative copy mt genome number per cell was above or below that of unobstructed controls. Bladders with high mt DNA content adjusted organellar genome copy number toward normal post-reversal but did not properly adjust mt transcript levels; mt-related nuclear transcripts in these samples showed recovery. Bladders with low mt DNA content showed no adjustment of those levels toward normal post-reversal but did show some adjustment in other mt and nuclear genetic parameters. Thus, a limiting factor for return of normal bladder function following reversal of outlet obstruction may be recovery of normal mt genetic performance.

Transcription of mitochondrial and mitochondria-related nuclear genes in rabbit bladder following partial outlet obstruction

Using the rabbit model, we showed that partial outlet obstruction of the urinary bladder causes significant changes in the status and expression of the mitochondrial (mt) genetic system in bladder smooth muscle immediately after obstruction is initiated. Here we investigate quantitatively the severity of the mt genetic response to partial outlet obstruction in both short- and long-term obstructed rabbits. Based on previous functional studies, bladders with mass < 6 fold greater than control were considered compensated; bladders with mass > 6 fold that of control were considered decompensated. Analyses of DNA from compensated rabbit bladders showed that relative mt genome copy number decreased to 30% of control values. Transcript analyses for these samples showed that mt RNA levels increased 3 fold to compensate for lower template copy number. Analysis of decompensated bladders demonstrated that mt genome copy number increased to approximately 90% of control levels; mt transcripts progressively decreased in these samples by as much as 30 fold. In contrast, transcription of a mt-related nuclear gene decreased 3-9 fold in compensated bladders but increased 10-30 fold in decompensated bladders. Activity for the cytochrome oxidase complex, and for the mt enzyme citrate synthase, decreased steadily with increasing bladder hypertrophy. These data suggest that bladder dysfunction following partial outlet obstruction is mediated partly by a significant loss in mt and mt-related nuclear gene coordination.

An additional type of male sterility and inherited urinary obstruction in mice with the t-haplotype th7

The t-complex on mouse chromosome 17 results in transmission ratio distortion in males heterozygous for complete haplotypes, and sterility in those homozygous for semi-lethal or doubly heterozygous for complementing lethal haplotypes. This sterility is due to inability of spermatozoa to fertilize. The haplotype th7 is an unusual laboratory-derived haplotype, postulated to carry a small duplication of t chromatin. Males heterozygous for th7 show a new form of sterility, apparently due to failure to form copulation plugs during mating. This is accompanied by a strong propensity to acute urinary obstruction. It is suggested that both the failure to form copulation plugs and the urinary obstruction are due to some abnormality in function of the accessory sex glands, and are the result of incorrect dosage of a gene in the postulated duplication. The symbol Msu for male sterility and urinary obstruction is suggested for the locus concerned. Previously a recessive form of abnormal behaviour had also been attributed to this duplication.

Assessment of stress gene mRNAs (HSP-27, 60 and 70) in obstructed rabbit urinary bladder using a semi-quantitative RT-PCR method

Stress proteins (HSPs) participate in the cellular response to various stresses including hyperthermia, hypoxia and injury. A previous work using northern blot analysis demonstrated increased expression of stress protein 70 (HSP-70) in rabbit bladder tissue subjected to partial outlet obstruction. In order to determine if the increased expression was specific for HSP-70 or, alternatively, indicated a generalized stress protein response, a modified quantitative RT-PCR technique was used to quantitate HSP mRNAs (HSP-27, 60, and 70) in normal and obstructed rabbit urinary bladder tissues. The results show the following: 1) The modified semi-quantitative RT-PCR is a sensitive and reproducible technique for detecting mRNA in bladder tissue. 2) Constitutive levels of HSP-27, HSP-60, and HSP-70 mRNAs were detected in control bladder tissues; the relative signal intensity was highest for HSP-70 and lowest for HSP-27. 3) A transient increase in HSP mRNAs was observed after obstruction; the mRNAs of HSP-27, 60 and 70 increased 4.3-, 5.6-, and 2.4-fold, respectively, at 24 h following obstruction, then gradually returned to control levels by the end of one week post-obstruction and remained stable up to 14 days post-obstruction. These data indicate that the modified quantitative RT-PCR is a useful technique for detecting mRNA in bladder tissue; the stress response which occurs in rabbit urinary bladder tissue following partial outlet obstruction is a general phenomenon.

Expression of cell growth regulated genes in the fetal kidney: relevance to in utero obstruction

Previous studies of fetal urinary tract obstruction (bladder outlet obstruction and ureteral obstruction) in lambs have shown that obstructions created relatively early in gestation (4/10 to 6/10 term) can significantly affect growth of the developing kidney. This suggests that urinary tract obstruction in utero can alter normal mechanisms of kidney growth. However, a mechanism for these effects has not yet been proposed. In this study we have used mRNA expression analysis to characterize the temporal sequence of expression of several growth-regulated genes during normal ovine kidney development. The purpose of this study was to test the hypothesis that early obstructions, such as those believed to arise in congenital obstructive uropathy in humans, might have a disproportionate effect on hyperplastic growth if the cellular growth fraction (percent of cells in the organ undergoing DNA synthesis) was greater in the second trimester than in the last. Northern blot analysis of the cell cycle-dependent genes histone H3, c-myc and ornithine decarboxylase (ODC) indicated a progressive, gradual decline in cellular proliferation in the kidney from approximately 60 to 135 days (4/10 term to term) gestation, as evidenced by decreases in the respective mRNA levels. The greatest levels of cell proliferation occurred near the midpoint of gestation. This indirect measurement of decline in cellular growth fraction was reflected in direct measurements of change in relative kidney weight. To test whether this decline in mRNA levels occurs widely among genes expressed in the fetal kidney during this period, relative expression levels of more than 300 anonymous mRNA transcripts were evaluated by differential display analysis. This method showed that genes whose expression patterns resembled the growth-regulated genes constituted less than 5% of the expressed mRNAs identified. These data indicate that intrauterine urinary tract obstructions that arise at or near the midpoint of gestation coincide with the highest rates of cell proliferation occurring in the second and third trimesters and, therefore, might adversely affect mechanisms of cell proliferation.

Genetic and cellular characteristics of bladder outlet obstruction

Urinary bladder outlet obstruction is a common medical problem. In order to understand the effects of outlet obstruction on bladder morphology, physiology, and pharmacology, several animal models of obstruction have been developed using a variety of species. Although there are marked differences in bladder size, capacity, compliance, physiology, and pharmacology among these species, responses to outlet obstruction have many common characteristics. This article will be separated into six areas: introduction, genetic factors mediating the response during the initial period of partial outlet obstruction and overdistension, cytostructural alterations that accompany compensated bladder function, alterations in innervation accompanying bladder hypertrophy secondary to partial outlet obstruction, alterations in calcium translocation during bladder hypertrophy, and metabolic factors involved in the response to partial outlet obstruction.

Bladder function in experimental outlet obstruction: pharmacologic responses to alterations in innervation, energetics, calcium mobilization, and genetics

The two functions of the urinary bladder is to store urine at low intravesical pressures, and to periodically expel the urine through a coordinated contraction of the bladder and relaxation of the urethra. To a large extent, urinary bladder function depends upon the underlying structure of the organ as a whole, particularly on the inter-relationships among the smooth muscle, connective tissue, and neuronal elements. An alteration in the ratio of connective tissue to smooth muscle, for example, can significantly alter compliance and functional capacity, structurally impairing the bladder's ability to empty efficiently and fully. Thus, a change in structural compartmentation can affect bladder function independent of autonomic receptor density, response to receptor stimulation, and the contractile capabilities of the smooth muscle elements. Similarly, a selective alteration in either the afferent or efferent innervation of the bladder or urethra can induce significant alterations in the structural interrelationships between smooth muscle and connective elements. In addition, the bladder responds rapidly to alterations in urine volume and urethral resistance with marked changes in bladder and urethral structure and function, and these changes are under the controls of specific genes that are known to control cellular growth, hypertrophy, and hyperplasia. A knowledge of the mechanisms that control the response to specific forms of stress may lead to novel therapies for specific disease states.

Molecular aspects of bladder outlet obstruction

In an animal model of obstruction, increasing load induces significant smooth muscle hypertrophy which is associated with a down-regulation of myosin heavy chain expression. This undoubtedly contributes to the decreased smooth muscle contractility seen in this model. Moreover, obstruction-induced hypertrophy leads to the development of a dedifferentiated smooth muscle phenotype, as evidenced by a revision of the cell to fetal (of non-muscle) gene expression patterns. Similar alterations are seen in atherosclerotic vessels and other pathologic smooth muscle systems. In these systems, dedifferentiation is also associated with significant alterations in extracellular matrix expression. It seems likely that obstruction in the bladder induces dedifferentiation of the smooth muscle cell which alters contractility as well as extracellular matrix expression, leading to altered bladder performance and decreased compliance.

Update on bladder smooth-muscle physiology

The urinary bladder responds to distension induced by a number of different stresses with rapid and substantial increases in bladder mass and concomitant alterations in the contractile responses to neuronal stimulation, pharmacological simulation by autonomic agonists, and membrane depolarization. Furosemide, sucrose, or diabetes-induced diuresis, as well as outlet obstruction and overdistension all produce similar effects on the bladder. Accompanying the increases in bladder mass and contractile changes are increases in DNA synthesis and [3H]-thymidine uptake. Autoradiographic studies have localized the increased DNA synthesis following bladder distension initially to the urothelium, followed by slower increases in labelling of the lamina propria and extramural connective tissue. The net result of these compartmental differences in DNA synthesis is a reorganization of the structural relationships between smooth-muscle cells, the connective-tissue matrix, and the extrinsic connective-tissue lamina. This may contribute to the functional changes which occur after severe overdistension. Increases in the expression of heat-shock protein-70, basic fibroblast growth factor, N-ras, and c-myc, and decreases in transforming growth factor-beta occurred acutely after obstruction, suggesting that these changes may play a role in obstruction-induced bladder hypertrophy. Removal of the obstruction induces apoptosis of urothelial and connective tissue elements in the bladder, accompanied by increases in transforming growth factor-beta and decreases in basic fibroblast growth factor genes, and a reversal of the bladder dysfunction. Therefore the bladder hyperplasia after outlet obstruction and the regression following removal of the obstruction seem to be directly opposing processes governed by gene expression.

Detrusor hyperplasia and expression of "immediate early" genes with onset of abnormal urodynamic parameters

To determine the stimulus for growth of the detrusor with a pathophysiological obstruction to the urinary stream, we studied urodynamic parameters, detrusor weight, detrusor DNA content, and the expression of early growth-related protooncogenes in a model of gradual onset bladder outflow obstruction and reversal of obstruction. Silver jeweler's jump rings were placed loosely round the urethra of immature guinea pigs, allowing an obstruction to develop gradually with animal growth. At 1, 2, 4, and 8 wk after surgery, animals were killed after urodynamic studies under urethan anesthesia. Bladders were removed, and mucosa-free detrusor was weighed and frozen for assay of DNA content and expression of c-fos and c-myc protooncogenes. Results were compared with sham-operated age-matched control animals. One week after surgery there was no change in the urodynamic parameters, detrusor weight, or DNA content. At 2, 4, and 8 wk after placement of the silver rings, animals developed obstructive voiding patterns, an increase in detrusor weight, and total DNA content. The onset of obstructive voiding patterns correlated with transient increased levels of c-fos and c-myc mRNA by Northern blot analysis. Autoradiography of in vivo [methyl-3H]thymidine-labeled detrusor muscle from obstructed animals showed myocyte DNA synthesis and mitosis, implying myocyte hyperplasia. After removal of the silver ring, the obstructive voiding patterns resolved and detrusor weight and DNA content returned to levels of the control animals. These results suggest that in the guinea pig bladder subjected to a gradual onset outflow obstruction, detrusor growth is initiated by the development of obstructive voiding patterns.(ABSTRACT TRUNCATED AT 250 WORDS)