The role of type IV collagenases in rat bladder development and obstruction

The roles of MCP-1/CCR2 mediated macrophage recruitment and polarization in bladder outlet obstruction (BOO) induced bladder remodeling

Bladder outlet obstruction (BOO) can lead to alternation of bladder structure and function, known as bladder remodeling. Macrophage is a heterogeneous cell type and implicated in immunity regulating and tissue repairment. The relationship between macrophage and BOO remains unclear. We determined the pivotal role of macrophage recruitment and polarization in bladder remodeling. Sprague-Dawley rats underwent surgical operation of a BOO for either 1, 3, 6 weeks and were compared with sham-operated rats. The BOO rats in the experimental group were orally administrated with 5 mg/kg RS-504393, a C-C chemokine receptor (CCR2) antagonist, for 6 weeks, and the rats in the control group were treated with vehicle. Bladder tissues were harvested for assays of flow cytometry, quantitative reverse transcription polymerase chain reaction, histological examinations, immunohistochemistry staining and immunofluorescence. After induction of BOO, M1 macrophages were predominantly observed at inflammatory stage while M2 macrophages were mainly found during fibrosis stage. Flow cytometry analysis revealed that the ratio of M1/M2 significantly increased at 3 weeks (P = 0.0013) when compared to the sham-operated group. Interestingly, our results showed that M2 macrophages promoted BOO-induced fibrosis through indirectly secreting TGF-β and directly transforming to collagen-producing myofibroblast. Additionally, RS-504393 treatment significantly decreased the number of M1 and M2 macrophage infiltration in bladder tissue, and bladder fibrosis was attenuated by RS-504393 treatment compared with that in the vehicle-treated rats. In summary, macrophages play a pivotal role in bladder remodeling and targeting MCP-1/CCR2 signaling pathway might be a therapeutic strategy for human bladder fibrosis.

The interplay of extracellular matrix and microbiome in urothelial bladder cancer

Many pathological changes in solid tumours are caused by the accumulation of genetic mutations and epigenetic molecular alterations. In addition, tumour progression is profoundly influenced by the environment surrounding the transformed cells. The interplay between tumour cells and their microenvironment has been recognized as one of the key determinants of cancer development and is being extensively investigated. Data suggest that both the extracellular matrix and the microbiota represent microenvironments that contribute to the onset and progression of tumours. Through the introduction of omics technologies and pyrosequencing analyses, a detailed investigation of these two microenvironments is now possible. In urological research, assessment of their dysregulation has become increasingly important to provide diagnostic, prognostic and predictive biomarkers for urothelial bladder cancer. Understanding the roles of the extracellular matrix and microbiota, two key components of the urothelial mucosa, in the sequelae of pathogenic events that occur in the development and progression of urothelial carcinomas will be important to overcome the shortcomings in current bladder cancer treatment strategies.

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.

The bladder extracellular matrix. Part I: architecture, development and disease

From the earliest studies with epithelial cells implanted into detrusor muscle to later experiments on smooth muscle in defined collagen gels, cell niche and extracellular matrix (ECM) have been clearly shown to orchestrate cellular behavior and fate whether quiescent, migratory, or proliferative. Normal matrix can revert transformed cells to quiescence, and damaged matrix can trigger malignancy or dedifferentiation. ECM influence in disease, development, healing and regeneration has been demonstrated in many other fields of study, but a thorough examination of the roles of ECM in bladder cell activity has not yet been undertaken. Structural ECM proteins, in concert with adhesive proteins, provide crucial structural support to the bladder. Both structural and nonstructural components of the bladder have major effects on smooth muscle function, through effects on matrix rigidity and signaling through ECM receptors. While many ECM components and receptors identified in the bladder have specific known functions in the vascular smooth musculature, their function in the bladder is often less well defined. In cancer and obstructive disease, the ECM has a critical role in pathogenesis. The challenge in these settings will be to find therapies that prevent hyperproliferation and encourage proper differentiation, through an understanding of matrix effects on cell biology and susceptibility to therapeutics.

Matrix metalloproteinase-7 and epidermal growth factor receptor mediate hypoxia-induced extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase activation and subsequent proliferation in bladder smooth muscle cells

Low oxygen tension (hypoxia) has been implicated in proliferation of vascular smooth muscle cells (SMCs) of the lung. Tissue hypoxia also occurs in the obstructed bladder. The extracellular-regulated kinase mitogen-activated protein kinase 1/2 (Erk1/2) pathway is induced in many cell types during hypoxia. We examined whether hypoxia (3% O2), compared with normoxia (21% O2), induces proliferation responses and activation of the Erk1/2 pathways in primary rat bladder smooth muscle cells (BSMCs). We show that hypoxia induces proliferation of BSMCs at 18 h and, although reduced at 22 h, still remained above normoxic levels. Hypoxia induced a strikingly transient activation of Erk1/2 that lasted only 10-30 min. However, inhibition of the transient Erk1/2 activity with a specific mitogen-activated protein kinase kinase 1 (MEK-1) inhibitor PD 98059 prevented subsequent hypoxia-induced proliferation at 18 h. Interestingly, inhibition of general matrix metalloproteinase (MMP) activity, using either doxycycline or GM 6001, prevented both transient Erk1/2 activity and subsequent proliferation in response to hypoxia. Furthermore, MMP-7 (matrilysin) is activated in the conditioned medium (CM) of BSMCs at 10-20 min of hypoxia. In addition, MMP-7 was also transcriptionally induced at 6 h of hypoxia in an Erk1/2-dependent manner. Moreover, transient Erk1/2 activation and BSMC proliferation were both dependent on epidermal growth factor receptor (EGFR/HER1) but not neu receptor (HER2/ERB2) autophosphorylation. We conclude that hypoxia leads to Erk1/2 activation, which appears to modulate BSMC proliferation through MMP-7-and EGFR-mediated mechanisms.

Mechanotransduction of extracellular signal-regulated kinases 1 and 2 mitogen-activated protein kinase activity in smooth muscle is dependent on the extracellular matrix and regulated by matrix metalloproteinases

Excessive wall stretch of distensible hollow organs in cardiovascular and urinary systems can activate matrix metalloproteinases (MMPs), thereby releasing matrix neoepitopes and growth factor ligands, leading to ERK1/2 activation. However, the role of MMPs in mechanotransduction of ERK1/2 signaling in the bladder is unknown. We examined bladders undergoing sustained distension over time, which provides a novel platform for smooth muscle mechanotransduction studies. Bladder distension ex vivo caused increased proliferation and MMP activity. Conditioned medium from distended compared with undistended bladders induced proliferation in bladder smooth muscle cells (BSMCs). When conditioned medium from distended bladders was used to proteolyze collagen type I matrices, matrices augmented BSMC proliferation, which was inhibited if bladders were distended in presence of broad-spectrum MMP inhibitors. Distension of ex vivo bladders also induced ERK1/2 phosphorylation in situ, which was dependent on MMP activity in the intact bladder. Similarly, stretching BSMCs in vitro induced increases in ERK1/2 activation and ERK1/2-dependent proliferation under discrete mechanical conditions, and distension conditioned medium itself induced MMP-dependent ERK1/2 activation in BSMCs. Overall, stretch-induced proliferation and ERK1/2 signaling in bladder tissue and BSMCs likely depend on secreted MMP activity. Identification of intermediaries between MMPs and ERK1/2 may elaborate novel mechanisms underlying mechanotransduction in bladder smooth muscle.

Collagen Directly Stimulates Bladder Smooth Muscle Cell Growth In Vitro: Regulation by Extracellular Regulated Mitogen Activated Protein Kinase

PURPOSE

Bladders clinically subjected to excessive pressure or distention demonstrate an altered extracellular matrix (ECM) composition. We determined how an altered collagen substratum might affect bladder smooth muscle cell (bSMC) growth in vitro and probed the mechanism of this response.

MATERIALS AND METHODS

Primary culture rat bSMCs were seeded onto culture plates pre-coated with normal type I collagen (NC) or heat denatured type I collagen (DNC) under standard culture conditions. In separate experiments bSMCs from the 2 substrates were enzymatically released and changed to growth on normal collagen (NC-->NC or DNC-->NC) or denatured collagen (DNC-->DNC or NC-->DNC). At 24 hours proliferation was assessed by 3H-thymidine incorporation. Statistical significance in triplicate wells was determined by ANOVA.

RESULTS

The proliferation of bSMCs on DNC was 5-fold greater than on NC (p <0.0001). Passage onto damaged collagen (DNC-->DNC) showed 2-fold further augmentation in proliferation (p <0.0001) but only a 50% decrease when NC was reintroduced (DNC-->NC) (p <0.001). Conversely replating on NC (NC-->NC) generated a 33% decrease in the already low proliferation rate (p <0.001) but 9-fold stimulation of proliferation when changed to damaged ECM (NC-->DNC) (p <0.0001). The mitogenic effect of damaged ECM on bSMC growth was abolished by specific inhibition of extracellular regulated kinase mitogen activated protein kinase signaling using PD98059.

CONCLUSIONS

Damaged type I collagen (ECM) is mitogenic to bSMCs. The response is amplified by re-exposure to DNC. However, mitogenicity is only partially reversible by re-introducing NC. These results demonstrate striking bSMC responsiveness to ECM conformation. Signaling through the extracellular regulated kinase mitogen activated protein kinase pathway supports bSMC-ECM interaction. We speculate that remodeling the ECM in vivo may regulate bSMC growth.

Induction of a hypertrophic growth status of coronary smooth muscle cells is associated with an overexpression of TGF-beta

Hypertrophy of vascular smooth muscle cells occurs during hypertension-induced remodelling of arteries and during development of arteriosclerosis and restenosis following angioplasty but the pathogenesis of the hypertrophic status is not yet fully understood. In a previous study we demonstrated that the synthetic non-sulfated, non-toxic heparin-mimicking compound RG-13577 is capable of inducing a cell cycle-arrested hypertrophic phenotype of coronary smooth muscle cells. In this study we clarify the mode of action of RG-13577 and demonstrate that the RG-13577-induced hypertrophy is associated with an increased expression of TGF-beta1 as indicated by an increase in TGF-beta1-specific protein and mRNA level. Furthermore we show that RG-13577-treated hypertrophic smooth muscle cells maintain full metabolic activity as indicated by a continuous de novo synthesis of protein and proteoglycans and that the RG-13577-induced growth arrest is caused not only by a higher expression of TGF-beta, but also by a reduced response of RG-treated cells to the mitogenic activity of bFGF, PDGF and EGF. The growth inhibitory activity of RG-13577 is reduced in the presence of neutralizing antibodies against TGF-beta. TGF-beta itself has anti-proliferative activity in serum-depleted medium. The RG-13577 effect is reversible since incubation of hypertrophic cells in RG-13577-free medium restores cell volume and [3H]thymidine incorporation to the values of untreated control cells within 4 days. We conclude, that the active metabolic status of RG-13577-treated cells in association with the overexpression of TGF-beta could promote repair processes of injured arteries after angioplasty without stimulating cell proliferation.

Extracellular matrix gene responses in a novel ex vivo model of bladder stretch injury

PURPOSE

Congenital bladder outlet obstruction from either mechanical or functional causes often results in clinical bladder fibrosis. We tested the hypothesis that early molecular changes relevant to fibrosis occur in response to stretch injury of the bladder wall and that specific extracellular matrix receptors mediate some of these responses. Furthermore, we introduce a novel ex vivo model of bladder injury which has advantages over previously described in vivo bladder outlet obstruction models by uniquely interrogating molecular responses to bladder distention.

MATERIALS AND METHODS

The bladders of Sprague Dawley rats were hydrodistended transurethrally, the ureters and bladder neck were ligated, and the whole bladder was excised and incubated in culture medium in the distended state. At fixed time-points control and stretch bladders were snap frozen, RNA was extracted, and semiquantitative reverse transcription polymerase chain reaction for collagens I, III and XII, and RHAMM (receptor for hyaluronic acid) messenger (m) RNA was performed to establish trends in stretch related gene expression. Bladder specimens were also subjected to routine histological evaluation.

RESULTS

An average 3-fold reduction in collagen I mRNA expression was seen with 8 hours of static stretch (p <0.05). Bladder stretch increased collagen III mRNA levels approximately 2.5-fold (p <0.05). Whole bladder collagen XII and RHAMM mRNA were elevated as much as 5-fold (p <0.05) with stretch. Blocking RHAMM function significantly attenuated these matrix gene responses (p = 0.01 to 0.005).

CONCLUSIONS

The ex vivo model of whole bladder stretch is viable and easily reproducible for the study of molecular pathophysiological mechanisms contributing to maladaptive bladder disease. Furthermore, collagen gene transcription is revealed to be rapidly responsive to stretch injury of the bladder. Intact RHAMM receptor function is involved in these responses. Elucidation of the intermediate steps in this response to injury may allow for the development of novel therapeutic strategies which may prevent pathological matrix remodeling seen in clinical bladder disease.

Extracellular matrix gene responses in a novel ex vivo model of bladder stretch injury

PURPOSE

Congenital bladder outlet obstruction from either mechanical or functional causes often results in clinical bladder fibrosis. We tested the hypothesis that early molecular changes relevant to fibrosis occur in response to stretch injury of the bladder wall and that specific extracellular matrix receptors mediate some of these responses. Furthermore, we introduce a novel ex vivo model of bladder injury which has advantages over previously described in vivo bladder outlet obstruction models by uniquely interrogating molecular responses to bladder distention.

MATERIALS AND METHODS

The bladders of Sprague Dawley rats were hydrodistended transurethrally, the ureters and bladder neck were ligated, and the whole bladder was excised and incubated in culture medium in the distended state. At fixed time-points control and stretch bladders were snap frozen, RNA was extracted, and semiquantitative reverse transcription polymerase chain reaction for collagens I, III and XII, and RHAMM (receptor for hyaluronic acid) messenger (m) RNA was performed to establish trends in stretch related gene expression. Bladder specimens were also subjected to routine histological evaluation.

RESULTS

An average 3-fold reduction in collagen I mRNA expression was seen with 8 hours of static stretch (p <0.05). Bladder stretch increased collagen III mRNA levels approximately 2.5-fold (p <0.05). Whole bladder collagen XII and RHAMM mRNA were elevated as much as 5-fold (p <0.05) with stretch. Blocking RHAMM function significantly attenuated these matrix gene responses (p = 0.01 to 0.005).

CONCLUSIONS

The ex vivo model of whole bladder stretch is viable and easily reproducible for the study of molecular pathophysiological mechanisms contributing to maladaptive bladder disease. Furthermore, collagen gene transcription is revealed to be rapidly responsive to stretch injury of the bladder. Intact RHAMM receptor function is involved in these responses. Elucidation of the intermediate steps in this response to injury may allow for the development of novel therapeutic strategies which may prevent pathological matrix remodeling seen in clinical bladder disease.

Matrix metalloproteinases and tissue inhibitor of metalloproteinase-2 in fetal rabbit lung

Cell-extracellular matrix interaction and extracellular matrix remodeling are known to be important in fetal lung development. We investigated the localization of matrix metalloproteinases (MMPs) in fetal rabbit lungs. Immunohistochemistry for type IV collagen, MMP-1, MMP-2, MMP-9, membrane type (MT) 1 MMP, and tissue inhibitor of metalloproteinase (TIMP)-2 and in situ hybridization for MMP-9 mRNA were performed. Gelatin zymography and Western blotting for MT1-MMP in lung tissue homogenates were also studied. MMP-1 and MT1-MMP were detected in epithelial cells, and MMP-2 and TIMP-2 were detected in epithelial cells and some mesenchymal cells in each stage. MMP-9 was found in epithelial cells mainly in the late stage. Gelatin zymography revealed that the ratio of active MMP-2 to latent MMP-2 increased dramatically during the course of development. MT1-MMP was detected in tissue homogenates, especially predominant in the late stage. These findings suggest that MMPs and their inhibitors may contribute to the formation of airways and alveoli in fetal lung development and that activated MMP-2 of alveolar epithelial cells may function to provide an extremely wide alveolar surface.

The hyaluronic acid receptor RHAMM is induced by stretch injury of rat bladder in vivo and influences smooth muscle cell contraction in vitro [corrected]

PURPOSE

Loss of bladder compliance from hypercontractility and fibrosis may represent an injury response to excessive intravesical pressure. Together, interactions between cell and extracellular matrix components regulate cell response to injury and extracellular matrix remodeling. The receptor for hyaluronic acid mediated motility (RHAMM) is a recently described hyaluronic acid binding protein known to influence multiple types of cell extracellular matrix interaction in development, injury and cancer. We evaluate the role of RHAMM in mediating early events in bladder stretch injury.

MATERIALS AND METHODS

An acute stretch injury model was used. The rat bladder was injured by hydrodistention inducing gross hematuria. Tissues were analyzed for temporal and spatial expression of RHAMM in the mucosa and detrusor regions by immunostaining, western and reverse transcriptase polymerase chain reaction analyses. The contractile activity of smooth muscle cell primary cultures was analyzed using a gel contraction assay in the presence of peptide fragments known to block RHAMM function.

RESULTS

Acute hydrodistention caused immediate and significant injury to the bladder, with fracturing of smooth muscle cell bundles, edema and hemorrhage. RHAMM immunolocalized to the mucosa and detrusor within 2 hours of injury, peaking by 5 to 10 hours. A shift from low molecular weight (55 kD.) to high (120 kD.) receptor isoforms was prominent during the peak expression period noted by immunolocalization. RHAMM messenger ribonucleic acid increased only slightly (40%) by 5 hours after injury. Smooth muscle cell primary cultures actively initiated and maintained the contraction of collagen gels by more than 75% of baseline in vitro. Blocking RHAMM function significantly inhibited the ability to less than 25% of smooth muscle cells to contract the gels in vitro.

CONCLUSIONS

Increased expression of RHAMM is an early event precipitated by stretch injury to the bladder. Since extracellular matrix hyaluronic acid is found early in tissue repair responses, its receptor RHAMM may be mediating initial bladder responses to stretch injury, some of which (contraction) may be experimentally blocked in vitro. Since the receptor directly regulates protein kinase signaling which in turn mediates smooth muscle cell contraction and collagen synthesis, further studies of RHAMM function in bladder pathology are warranted.

Neuroanatomical changes in the rat bladder after bladder outlet obstruction

OBJECTIVE

To investigate the histological changes in bladder innervation in response to partial bladder outlet obstruction in a rat model.

MATERIALS AND METHODS

Forty-eight adult female rats had their bladder outlet partially obstructed by ligating the proximal urethra over a 20 G angiocatheter; 18 shamoperated rats served as controls. Animals were killed after 1, 2 and 4 weeks, and their bladders evaluated using computerized morphometry. Immunohistochemical staining for neuronal protein gene-product 9.5 (PGP, a general neuronal marker) and enzyme histochemical staining of acetylcholinesterase, adrenergic fibres and nitric oxide synthase were performed.

RESULTS

Bladder wall changes after obstruction consisted of a six- to sevenfold increase in bladder volume and weight. Smooth muscle hypertrophy was evident equally at all sample times. Cystometry showed functional alterations in bladder capacity and voided pressures; obstructed animals had markedly increased bladder capacities and higher voiding pressures (obstructed, 80-100 cmH2O; normal, 30-40 cmH2O). Neuronal changes in the obstructed bladder were most dramatic within the cholinergic and adrenergic neurotransmitter systems within and surrounding the smooth muscle bundles, where there was less staining than in control animals. PGP immunoreactivity increased slightly. The L-arginine-nitric oxide pathway appeared unperturbed after obstruction.

CONCLUSIONS

These histological findings suggest that neuropathic changes in the bladder after outlet obstruction, including detrusor instability, are mainly the result of anatomical perturbations in the cholinergic and adrenergic pathways.