Temporal expression of elastic fiber components in bladder development

Compound 48/80 increases murine bladder wall compliance independent of mast cells

A balance between stiffness and compliance is essential to normal bladder function, and changes in the mechanical properties of the bladder wall occur in many bladder pathologies. These changes are often associated with the release of basic secretagogues that in turn drive the release of inflammatory mediators from mast cells. Mast cell degranulation by basic secretagogues is thought to occur by activating an orphan receptor, Mas-related G protein-coupled receptor B2 (Mrgprb2). We explored the effects of the putative mast cell degranulator and Mrgprb2 agonist Compound 48/80 on urinary bladder wall mechanical compliance, smooth muscle contractility, and urodynamics, and if these effects were mast cell dependent. In wild-type mice, Mrgprb2 receptor mRNA was expressed in both the urothelium and smooth muscle layers. Intravesical instillation of Compound 48/80 decreased intermicturition interval and void volume, indicative of bladder overactivity. Compound 48/80 also increased bladder compliance while simultaneously increasing the amplitude and leading slope of transient pressure events during ex vivo filling and these effects were inhibited by the Mrgprb2 antagonist QWF. Surprisingly, all effects of Compound 48/80 persisted in mast cell-deficient mice, suggesting these effects were independent of mast cells. These findings suggest that Compound 48/80 degrades extracellular matrix and increases urinary bladder smooth muscle excitability through activation of Mrgprb2 receptors located outside of mast cells. Thus, the pharmacology and physiology of Mrgprb2 in the urinary bladder is of potential interest and importance in terms of treating lower urinary tract dysfunction.

Pelvic Organ Support in Animals with Partial Loss of Fibulin-5 in the Vaginal Wall

Compromise of elastic fiber integrity in connective tissues of the pelvic floor is most likely acquired through aging, childbirth-associated injury, and genetic susceptibility. Mouse models of pelvic organ prolapse demonstrate systemic deficiencies in proteins that affect elastogenesis. Prolapse, however, does not occur until several months after birth and is thereby acquired with age or after parturition. To determine the impact of compromised levels of fibulin-5 (Fbln5) during adulthood on pelvic organ support after parturition and elastase-induced injury, tissue-specific conditional knockout (cKO) mice were generated in which doxycycline (dox) treatment results in deletion of Fbln5 in cells that utilize the smooth muscle α actin promoter-driven reverse tetracycline transactivator and tetracycline responsive element-Cre recombinase (i.e., Fbln5f/f/SMA++-rtTA/Cre+, cKO). Fbln5 was decreased significantly in the vagina of cKO mice compared with dox-treated wild type or controls (Fbln5f/f/SMA++-rtTA/Cre-/-). In controls, perineal body length (PBL) and bulge increased significantly after delivery but declined to baseline values within 6-8 weeks. Although overt prolapse did not occur in cKO animals, these transient increases in PBL postpartum were amplified and, unlike controls, parturition-induced increases in PBL (and bulge) did not recover to baseline but remained significantly increased for 12 wks. This lack of recovery from parturition was associated with increased MMP-9 and nondetectable levels of Fbln5 in the postpartum vagina. This predisposition to prolapse was accentuated by injection of elastase into the vaginal wall in which overt prolapse occurred in cKO animals, but rarely in controls. Taken together, our model system in which Fbln5 is conditionally knock-downed in stromal cells of the pelvic floor results in animals that undergo normal elastogenesis during development but lose Fbln5 as adults. The results indicate that vaginal fibulin-5 during development is crucial for baseline pelvic organ support and is also important for protection and recovery from parturition- and elastase-induced prolapse.

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.

GAGs and GAGs diseases: when pathophysiology supports the clinic

The urinary epithelium has been the subject of considerable interest and much research in recent years. What has radically changed in the last decade is the concept of what the bladder epithelium really is. It is currently no longer considered just a simple barrier and a non-specific defence against infections, and it has been recognized as a specialized tissue regulating complex bladder functions and playing a fundamental and active role in the pathogenesis of cystitis. Researchers have been focussing on the receptors and mediators that are active in the sub-epithelial layer, with the hope that understanding the role of the urothelium defect will offer the opportunity for new therapeutic strategies. On the surface of the urothelial umbrella-cells there is a thick layer of glycoproteins and proteoglycans, which together are called Glycosaminoglycans (GAGs). They constitute a hydrophilic mucosal coating and act as a barrier against solutes found in urine. In recent years they have received special attention because injury to Gags, due to different noxae, has been identified as the first step in the genesis of chronic inflammatory bladder diseases, such as recurrent urinary tract infections, chemical or radiation cystitis, interstitial cystitis and/or Bladder Pain Syndrome. Aim of this study is to define the importance of the urothelium starting from the anatomy and physiology of the bladder wall. Furthermore, we will underline the role of glycosaminoglycans, focusing both on their pathophysiological role in the principal bladder diseases and on the therapeutic aspects from the clinical point of view.

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.

The impact of pregnancy and childbirth in the urethra of female rats

The aim of this study was to evaluate the modifications in the amount of collagen, muscular, and elastic fibers in the mid-urethra of adult female rats during the pregnancy and after the natural childbirth, cesarean, and after simulated trauma of childbirth. The authors evaluated the histomorphometric aspects (collagen, muscular, and elastic fibers) in the mid-urethra of 70 animals distributed in seven groups: group 1 (n = 10)--control, group 2 (n = 10)--pregnant female rats, group 3 (n = 10)--female rats submitted to cesarean, group 4 (n = 10)--female rats with natural childbirth, group 5 (n = 10)--virgin female rats with simulated trauma of childbirth, group 6 (n = 10)--female rats submitted to cesarean followed by simulation of childbirth trauma, and group 7 (n = 10)--female rats with natural childbirth followed by simulation of childbirth trauma. The average concentration of collagen and elastic fibers and the collagen/muscular fiber correlation in groups 1, 2, and 3 were similar and significantly inferior to groups 4, 5, 6, and 7. The average of muscular fibers was similar in groups 1, 2, and 3 and significantly superior to groups 4, 5, 6, and 7. Pregnancy and cesarean did not induce alterations in collagen, muscular, and elastic fibers. However, the vaginal delivery and simulation of childbirth trauma determined the decrease in muscular fibers and the increase in collagen and elastic fibers and the correlation collagen/muscular fiber.

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.

Extracellular matrix and nuclear localization of beta ig-h3 in human bladder smooth muscle and fibroblast cells

The extracellular matrix (ECM) plays an essential role in bladder structure and function. In this study, expression of beta ig-h3, a recently identified extracellular matrix protein, was investigated in human bladder tissue, and human bladder smooth-muscle (SMC) and fibroblast cells in vitro. SMCs secreted greater than three times the level of this protein compared with fibroblasts. The relative levels of beta ig-h3 mRNA in the two cell types reflected the protein expression. Immunohistochemical analysis demonstrated protein deposition in the ECM as well as cytoplasmic localization and, unexpectedly, nuclei. Anti-beta ig-h3 antibodies also stained the matrix surrounding the detrusor SMCs and nuclei of bladder fibroblasts, SMCs, and urothelium in intact bladder tissue. Western blot analyses of medium and matrix fractions obtained from cells in vitro revealed protein of approximately 70-74 kDa, whereas nuclear extracts contained a 65-kDa reactive protein band. We propose that although this protein is a structural component of bladder ECM, its nuclear localization suggests that it has other regulatory and/or structural functions.