DISTRIBUTION OF COLLAGEN XII AND XIV IN THE BLADDER WALL OF THE MALE RAT WITH OUTLET OBSTRUCTION

The Translational Role of Animal Models for Estrogen-Related Functional Bladder Outlet Obstruction and Prostatic Inflammation

The prevalence of LUTS and prostatic diseases increases with age both in humans and companion animals, suggesting that a common underlying cause of these conditions may be age-associated alterations in the balance of sex hormones. The symptoms are present with different and variable micturition dysfunctions and can be assigned to different clinical conditions including bladder outlet obstruction (BOO). LUTS may also be linked to chronic non-bacterial prostatitis/chronic pelvic pain syndrome (CP/CPPS), but the relationship between these conditions is unknown. This review summarizes the preclinical data that supports a role for excessive estrogen action in the development of obstructive voiding and nonbacterial prostatic inflammation. Preclinical studies that are emphasized in this review have unequivocally indicated that estrogens can induce functional and structural changes resembling those seen in human diseases. Recognizing excessive estrogen action as a possible hormonal basis for the effects observed at multiple sites in the LUT may inspire the development of innovative treatment options for human and animal patients with LUTS associated with functional BOO and CP/CPPS.

Muscle cells, nerves, fibroblasts and vessels in the detrusor of the rat urinary bladder

All the cells of rat detrusor muscle fall into one of five ultrastructural types: muscle cells, fibroblasts, axons and glia, and vascular cells (endothelial cells and pericytes). The tissue is ~79% cellular and 21% non-cellular. Muscle cells occupy 72%, nerves ~4% (1/3 axons, 2/3 glia), and fibroblast >3% of space. Muscle cells (up to 6 µm across and ~600 µm long, packed to almost 100,000 per mm²) have surface-to-volume ratio of 2.4 µm²/µm³ ~93% of cell volume is contractile apparatus, 3.1% mitochondria and 2.5% nucleus. Cell profiles are irregular but sectional area decreases regularly towards either end of the cell. Muscle cells are gathered into bundles (the mechanical units of detrusor), variable in length and size, but of constant width. The musculature is highly compact (without fascia or capsule) with smooth outer surfaces and extensive association and adhesion between its cells. Among many types of intercellular contact and junction, digitations are very common, each muscle cell issuing minute finger-like processes that abut on adjacent cells. Sealed apposition are wide areas of specialized contact, possibly forming a chamber between two muscle cells, distinct from the extracellular space at large (stromal space). The innervation is very dense, virtually all intramuscular axons being varicose (including afferent ones). There are identifiable neuro-muscular junctions on each muscle cell, often several junctions on a single cell. There are also unattached terminals. Fibroblasts (involved in the production of collagen), ~1% of the total number of cells, do not make specialized contacts.

Effect of transforming growth factor α overexpression on urogenital organ development in mouse

Transforming growth factor-α (TGFα) promotes cell proliferation by binding to the epidermal growth factor receptor (EGFR). TGFα and EGFR overexpression have been reported in various human cancers. However, whether TGFα induces cancer by itself is unknown in urogenital organs. To investigate whether TGFα overexpression induces carcinogenesis in urogenital organs, we analyzed the phenotypes of urogenital organs in male TGFα transgenic (TG) mice of the CD1 strain. Urogenital organs including the kidney, bladder, prostate, seminal vesicles, testes, and epididymis were isolated from 4- to 48-week-old TGFα TG and wild-type (WT) CD1 mice. Prostates were separated into anterior prostate (AP), dorsolateral prostate (DLP), and ventral prostate (VP). Neither tumor formation nor epithelial hyperplasia was observed in the TGFα TG mouse urogenital organs that we have investigated. Histopathologically, in prostate, we found an increased number of p63-positive basal epithelial cells in the TGFα TG mice AP and DLP. There was no morphological change in the stromal component, such as hypercellular stroma or fibrosis. However, bladder weight was greater in TGFα TG mice than that in WT mice, and distended bladders were observed macroscopically in 19 of 20 TGFα TG mice over 20 weeks of age. Ki67 labeling index was increased significantly in the TGFα TG mouse urethral epithelium, whereas neither epithelial hyperplasia nor hypertrophy was observed. In conclusion, our results suggest that TGFα overexpression in mouse urogenital organs alone may not be responsible for tumor formation and epithelial hyperplasia, but is involved in bladder outlet obstruction.

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.

Developmental aspects of bladder function

A review was conducted of the current knowledge of fetal and postnatal development of autonomic bladder function in animals. Studies of fetal and neonatal bladder development have been done in many animal species. Development of normal bladder function requires coordination of a number of different systems and processes, and continues after birth during the early neonatal period. In many neonatal animals, micturition occurs only after stimulation of a perineal-to-bladder reflex triggered when the mother licks the perineal region, and bladder distension fails to stimulate micturition. Voiding resulting from the normal bladder-to-bladder spinobulbospinal reflex activated by bladder distension develops only slowly over the first few weeks of life as synaptic connections in the sacral parasympathetic nucleus mature. The neurogenic response of bladder strips from young neonates is more sensitive to inhibition by atropine than that of strips from older animals, suggesting that there are developmental changes in the contribution of non-adrenergic, non-cholinergic transmitters to the response of the bladder smooth muscle to intramural nerve stimulation. Release of acetylcholine from cholinergic nerves and the mechanisms required to transform muscarinic receptor stimulation into efficient bladder contraction and emptying are fully developed at birth, but contractile and relaxant responses to many other agonists, such as adenosine triphosphate and noradrenaline, are developmentally regulated. Changes in calcium influx and storage may be responsible for many of these changes. Fetal detrusor is exquisitely sensitive to nitric oxide. Electrical stimulation of precontracted fetal bladder strips causes relaxation, an effect that is not seen in adult tissues, and is decreased by inhibitors of the actions of nitric oxide. Development of bladder function occurs before the onset of puberty and therefore is not normally dependent on sex hormones. However, neonatal treatment with or depletion of sex hormones can modulate bladder function. In particular, alpha-adrenergic receptor-mediated contractile responses of bladder detrusor are increased by prepubertal castration, an effect that may result from increases in the density of alpha-adrenergic receptors and/or changes in alpha-adrenergic receptor subtype expression.

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.

Effect of strip length on the contractile dysfunction of bladder smooth muscle after partial outlet obstruction

OBJECTIVES

Partial outlet obstruction mediates decreased contractile responses and increased collagen synthesis; however, it is not known to what extent the increased collagen contributes to contractile dysfunction.

METHODS

Sixteen WNZ rabbits were divided into three groups: control, 2-week obstructed, and 2-week sham. Each rabbit was anesthetized, and the bladder was excised and cut into equal width strips of 0.5, 1.0, and 2.0-cm lengths. The contractile responses to field stimulation, carbachol, potassium chloride, and adenosine triphosphate were determined. At the end of the experiment, each strip was fixed in formalin and immunostained for collagen.

RESULTS

The contractile responses for the control and sham strips were similar for all strip lengths. In obstructed tissue, the shorter strip lengths generated significantly more tension per cross-sectional area than did the longer strips. The collagen density and distribution were similar for the control and sham bladders. The obstructed bladders had significantly increased collagen deposits between and within the smooth muscle bundles and cells.

CONCLUSIONS

Because the relationship between strip size and contraction were similar for field stimulation, carbachol, and potassium chloride, it is the increased density of connective tissue within and between the muscle bundles and fibers that interferes with contraction (ie, the greater the strip length, the greater the interference and the greater the contractile dysfunction). Therefore, both functional and structural alterations in the obstructed bladder participate in contractile dysfunction.

Morphological analysis of the acute effects of overdistension on the extracellular matrix of the rat urinary bladder wall

PURPOSE

To investigate the morphological effects of acute overdistension in the structure of the extracellular matrix of the bladder wall in rats.

MATERIALS AND METHODS

The bladders of a group of 6 male Wistar rats were transurethrally overdistended for 3 hours. Another identical group (the control group) was only submitted to a sham operation. Specimens from the bladder dome were analyzed with light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

RESULTS

LM--The control group bladders had a 4 to 5 layer urothelium, a lamina propria, and a smooth muscle layer with longitudinal and transversal fibers. The overdistended bladders presented an intense interstitial infiltrate in the lamina propria, and a less intense infiltrate among the smooth muscle fibers. TEM--The cells of the overdistended bladders had a significant amount of vacuoles, unlike the control bladders, where such vacuoles were scarce or absent. SEM--A delicate three-dimensional mesh of collagen fibrils was observed in the lamina propria of the bladder walls from the control group. Whilst for the control group this mesh consisted of distinct geometric structures, with mostly circular cellular spaces surrounded by the fibrils, the overdistended group showed evidence of distortion of the mesh, with flattened and elongated cellular spaces.

CONCLUSIONS

Acute bladder overdistension induces structural modifications, altering the arrangement and interaction of collagen fibrils, as well as incipient tissue damage as edema in the lamina propria and smooth muscle layers.

In vitro rat bladder function after neonatal estrogenization

PURPOSE

Experiments were done to evaluate the functional effects of neonatal diethylstilbestrol (DES) treatment on bladder function in male and female Noble rats.

MATERIALS AND METHODS

At 5 months after neonatal DES bladders were removed and weighed. Ventral and dorsal bladder strips were prepared to evaluate the effects of neonatal DES on contractile responses to electrical field stimulation, carbachol, adenosine triphosphate, phenylephrine and KCl. Relaxant responses to the catecholamines arterenol (norepinephrine), epinephrine and isoproterenol were also monitored.

RESULTS

Neonatal DES resulted in significant increases in bladder mass in males and females. Contractile and relaxant responses were largely unchanged by neonatal DES treatment and the only change observed was a decreased response of ventral strips from male neonatal DES rats to 4 and 8 Hz. stimulation. Ventral strips from male control and neonatal DES rats responded to field stimulation and carbachol with significantly greater responses than dorsal strips and were more sensitive to the relaxant actions of norepinephrine and epinephrine.

CONCLUSIONS

The data confirm that neonatal DES causes infravesical obstruction. However, in contrast to published reports of the effects of surgically induced mild outlet obstruction, neonatal DES treatment has little effect on in vitro bladder strip contractile or relaxant function. Thus, the neonatal DES treated rat does not seem to be a useful model in which to study the in vitro effects of partial outlet obstruction on the bladder.