Immunohistochemical characteristics of suburothelial microvasculature in the mouse bladder

The morphological characteristics of smooth muscle cells (SMCs) and their innervation of the suburothelial microvasculature of the mouse bladder were investigated by immunohistochemistry. Whole mount bladder mucosal preparations were immune-stained for α-smooth muscle actin (α-SMA) and/or neuronal markers and examined using confocal laser scanning microscopy. Suburothelial arterioles consisted of α-SMA-immunopositive circular smooth muscle cells, while the venular wall composed of α-SMA-positive SMCs that displayed several processes which extended from their cell bodies to form an extensive meshwork. In larger venules, a complex meshwork of stellate-shaped SMCs were observed. NG2 chondroitin sulphate proteoglycan-immunoreactive cell bodies of capillary pericytes were not immunoreactive for α-SMA. In the rat bladder suburothelial venules, circular SMCs were the dominant cell type expressing α-SMA-immunoreactivity. Since α-SMA-positive SMCs in suburothelial arterioles and venules in the mouse bladder had quite distinct morphologies, the innervation of both vessels could be examined by double labelling for α-SMA and various neuronal markers. Varicose nerve bundles immunoreactive for tyrosine hydroxylase (sympathetic nerves), choline acetyltransferase (cholinergic nerves) or substance P (primary afferent nerves) were all detected along side suburothelial arterioles. Single varicose nerve fibres positive for these three neuronal markers were also detected around the venules. Thus, whole mount preparations are useful when examining the morphology of α-SMA-positive SMCs of the microvasculature in the suburothelium of mouse bladder as well as their relationship with their innervations. In conclusion, arterioles and venules of the bladder suburothelium are the target of sympathetic, cholinergic and primary afferent nerve fibres.

Formation and maintenance of blood-urine barrier in urothelium

Blood-urine barrier, which is formed during differentiation of superficial urothelial cells, is the tightest and most impermeable barrier in the body. In the urinary bladder, the barrier must accommodate large changes in the surface area during distensions and contractions of the organ. Tight junctions and unique apical plasma membrane of superficial urothelial cells play a critical role in the barrier maintenance. Alterations in the blood-urine barrier function accompany most of the urinary tract diseases. In this review, we discuss recent discoveries on the role of tight junctions, dynamics of Golgi apparatus and post-Golgi compartments, and intracellular membrane traffic during the biogenesis and maintenance of blood-urine barrier.

Experimental strategies to improve in vitro models of renal ischemia

Ischemia has elicited a great deal of interest among the scientific community due to its role in life-threatening pathologies such as cancer, stroke, acute renal failure, and myocardial infarction. Oxygen deprivation (hypoxia) associated with ischemia has recently become a subject of intense scrutiny. New investigators may find it challenging to induce hypoxic injury in vitro. Researchers may not always be aware of the experimental barriers that contribute to this phenomenon. Furthermore, ischemia is associated with other major insults, such as excess carbon dioxide (hypercapnia), nutrient deprivation, and accumulation of cellular wastes. Ideally, these conditions should also be incorporated into in vitro models. Therefore, the motivation behind this review is to: i. delineate major in vivo ischemic insults; ii. identify and explain critical in vitro parameters that need to be considered when simulating ischemic pathologies; iii. provide recommendations to improve experiments; and as a result, iv. enhance the validity of in vitro results for understanding clinical ischemic pathologies. Undoubtedly, it is not possible to completely replicate the in vivo environment in an ex vivo model system. In fact, the primary goal of many in vitro studies is to elucidate the role of specific stimuli during in vivo pathological events. This review will present methodologies that may be implemented to improve the applicability of in vitro models for understanding the complex pathological mechanisms of ischemia. Finally, although these topics will be discussed within the context of renal ischemia, many are pertinent for cellular models of other organ systems and pathologies.

Fluid flow in the juxtaglomerular interstitium visualized in vivo

Earlier electron microscopy studies demonstrated morphological signs of fluid flow in the juxtaglomerular apparatus (JGA), including fenestrations of the afferent arteriole (AA) endothelium facing renin granular cells. We aimed to directly visualize fluid flow in the JGA, the putative function of the fenestrated endothelium, using intravital multiphoton microscopy of Munich-Wistar rats and C57BL6 mice. Renin content of the AA correlated strongly with the length of the fenestrated, filtering AA segment. Fluorescence of the extracellular fluid marker lucifer yellow (LY) injected into the cannulated femoral vein in bolus was followed in the renal cortex by real-time imaging. LY was detected in the interstitium around the JG AA before the plasma LY filtered into Bowman's capsule and early proximal tubule. The fluorescence intensity of LY in the JGA interstitium was 17.9 ± 3.5% of that in the AA plasma ( n = 6). The JGA fluid flow was oscillatory, consisting of two components: a fast (one every 5–10 s) and a slow (one every 45–50 s) oscillation, most likely due to the rapid transmission of both the myogenic and tubuloglomerular feedback (TGF)-mediated hemodynamic changes. LY was also detected in the distal tubular lumen about 2–5 s later than in the AA, indicating the flow of JGA interstitial fluid through the macula densa. In the isolated microperfused JGA, blocking the early proximal tubule with a micropipette caused significant increases in MD cell volume by 62 ± 4% ( n = 4) and induced dilation of the intercellular lateral spaces. In summary, significant and dynamic fluid flow exists in the JGA which may help filter the released renin into the renal interstitium (endocrine function). It may also modulate TGF and renin signals in the JGA (hemodynamic function).

Obituary to analgesic nephropathy--an autopsy study

BACKGROUND

To determine whether classic analgesic nephropathy with renal papillary and urothelial capillary sclerosis could still be detected at autopsy in the beginning of the 21st century, the present study which is similar to a previous one performed in 1980 was undertaken as suggested by the Ad Hoc Committee of the International Study Group on Analgesics and Nephropathy.

METHODS

Consecutive autopsies of 616 adults performed at the Basle Institute of Pathology between November 2000 and February 2002 were analysed. Tissue samples of renal cortex and papilla of 1220 kidneys and of each ureter and main renal artery available were subjected to a very careful and meticulous study using classical histopathological methodology.

RESULTS

A number of lesions was found macroscopically but not a single case of papillary necrosis or analgesic nephropathy could be detected preceding histological analysis. Histologically, the most frequent lesions were vascular in 57.8% of kidneys followed by glomerular lesions in 13.1% (mostly diabetic glomerulosclerosis). Tubulo-interstitial lesions, mostly pyelonephritis were detected in 9.3% with only a single case of classic analgesic nephropathy with bilateral complete papillary necrosis and ureteral capillary sclerosis in a female who had received a renal transplant 14 years before her demise at the age of 67. In another five cases, complete papillary necrosis was detected associated with pyelonephritis, hydronephrosis or in completely shrunken kidneys. However, in the absence of capillary sclerosis, a histopathological diagnosis of classic analgesic nephropathy could not be made in any of these five cases.

CONCLUSIONS

The Basle autopsy prevalence of analgesic nephropathy decreased continuously from some 3% in 1980 to 0.2% in 2000 as shown by the present study. Similarly, capillary sclerosis of the urinary tract, the initiating event in the pathophysiology of papillary necrosis and analgesic nephropathy and the histological hallmark of the effect of toxic metabolites of phenacetin in analgesic abusers decreased from 4% of autopsy cases between 1978 and 1980 to the single case of the present study observed at the end of 2000. Thus, the classic analgesic nephropathy has disappeared some 20 years after the removal of phenacetin from the analgesic market despite the fact that mixed analgesics containing paracetamol, the main metabolite of phenacetin, have continued to be popular and widely used drugs.

Neovascularisation is a prognostic factor of early recurrence in T1/G2 urothelial bladder tumours

BACKGROUND

Of patients with superficial bladder cancer, a group are still at risk of disease recurrence, progression and death from their cancer after curative treatment. Angiogenesis is a crucial pathogenic mechanism for this type of urothelial cell carcinoma (UCC), and is a potential therapeutic target. However, the selection of the appropriate patients remains a dilemma.

PATIENTS AND METHODS

Vascular endothelial growth factor (VEGF) expression and the presence of angiogenesis and occurrence of CD31, CD34, endoglin and factor VIII immunoexpression, were evaluated in 66 superficial papillary UCCs of the bladder and were correlated with classical histopathological factors and disease outcome.

RESULTS

VEGF immunoreactivity was observed in 100% of cases, and more intensely in the luminal surface. The presence of microvessel clusters independently of a fibrovascular core was observed in 22.7% of cases. Of these, the T1/G2 subgroup had an independent and significantly lower recurrence-free survival (P = 0.0002).

CONCLUSIONS

These results indicate that the presence of angiogenesis in tumour urothelium is a potential prognostic factor in superficial UCC, particularly in T1/G2 tumours, and may be used to select patients for anti-angiogenic treatments.

Interferon-a2b reduces neo-microvascular density in the 'normal' urothelium adjacent to the tumor after transurethral resection of superficial bladder carcinoma

BACKGROUND

As angiogenesis represents one of the hallmarks of cancer we investigated whether intravesically administered interferon-a (IFN-a2b) reduces neo-angiogenesis in the 'normal' urothelium adjacent to the tumor in patients with superficial bladder carcinoma after complete transurethral resection (TUR) of the tumor.

PATIENTS AND METHODS

In the present study 47 patients after TUR of the tumor were examined. 10 patients (group A) received no further treatment (control group); 37 patients (group B) received intravesical treatment with IFN-a2b. The instillations started within 7 days after TUR, were performed weekly for 2 months, twice a month for the next 4 months, and thereafter monthly for 6 more months. Cold cup biopsies were taken before TUR of the transitional cell carcinoma (TCC): from the tumor (T), near tumor (NT) and from normal epithelium (N). Cold cup biopsies 'near tumor', were also taken during follow-up cystoscopy (C1, C2, and C3) 2, 6, and 12 months after TUR, respectively. Angiogenesis was estimated by counting the microvessels detected with CD31 immunostaining.

RESULTS

Significant differences of microvascular density (MVD) between patients of group A and B appear after TUR (p < 0.005, Kruskal-Wallis and Wilcoxon test). The MVD difference was maximal 6 months after TUR (C2(A)-C2(B), second cystoscopy) and measured at 12.17 microvessels/ mm(2) (26.2%).

CONCLUSION

Our results show that the intravesical administration of IFN-a2b after TUR significantly decreases the angiogenic potential of the 'healthy' urothelium adjacent to the tumor in patients with TCC. This observation could possibly explain, to a certain extent, the mechanism by which IFN-a2b reduces the recurrence rate of primary TCC.

Vascular response of the rabbit bladder to short term partial outlet obstruction

Partial bladder outlet obstruction of the rabbit bladder results in a rapid increase in mass characterized by remodeling of the bladder wall. In this study we investigated the effect of partial outlet obstruction on microvessel density and distribution in the bladder wall immunohistochemically using CD31 as a marker for vascular endothelium, and on blood flow using a fluorescent microsphere technique. Transverse sections of bladder wall were examined after 0 (unobstructed), 1, 3, 5, 7, and 14 days of obstruction. The microvasculature of obstructed rabbit bladder mucosa and detrusor smooth muscle apparently increased relative to augmentation of these compartments, while new vessels appeared in the thickening serosa. These vascular changes correlated with results showing that, at 1 week after obstruction, blood flow (ml/min/g tissue) to the mucosa and detrusor was unchanged. Thickening of the serosa, apparent after 1 day of obstruction, began before its vascularization. Then, 1 week post-obstruction, there was significant microvessel formation in the transition region between the detrusor smooth muscle and the increasing serosa; after 2 weeks, the entire serosa was vascularized. The vascularization of the muscle-serosal transition region and then the remaining serosa apparently precedes fibroblast differentiation, providing blood supply and thus metabolic support for this process. All obstructed rabbit bladders in this study were in a state of compensated function based on their weights. Our working hypothesis is that blood flow per unit tissue mass is normal in compensated obstructed bladders, thus allowing for normal contractile function and cellular metabolism. The results of this study indicate the presence of an augmented microvasculature in compensated obstructed rabbit bladders that provides adequate blood perfusion for normal function.

Early cellular and ultrastructural response of the mouse urinary bladder urothelium to ischemia

An experimental ischemic model of mouse urinary bladder was developed to study urothelium permeability and changes in cell ultrastructure. The bladder permeability barrier response to experimental ischemia (30-120 min) was investigated by means of indigo carmine dye, trypan blue and lanthanum nitrate tracer, which were used as quantitative and qualitative indicators of urothelial integrity. Changes to the urothelium were studied by light microscopy, and by scanning and transmission electron microscopy. It was established that ischemia primarily induces breakdown of the blood-urine permeability barrier by disruption of the tight junctions. It causes focal interruption of the contacts between the cells, which is followed by detachment and desquamation of viable urothelial cells. Urothelial damage occurs as funnel-shaped wounds, which can extend into the lamina propria. They are proportional to the duration of ischemia and to the extent of reperfusion induced. Desquamated cells in the bladder lumen, when exposed to hypertonic and toxic urine, gradually become irreversibly changed.

Bladder microvasculature in women with interstitial cystitis

PURPOSE

A cardinal cystoscopic finding in women with interstitial cystitis is mucosal small vessel hemorrhage or glomerulations after hydrodistention. We quantified and compared microvascular density and endothelial proliferation in the bladder biopsies of women with interstitial cystitis and a control group of women who were undergoing incontinence or prolapse surgery.

MATERIALS AND METHODS

We performed computer assisted image analysis and immunohistochemical studies to compare differences in the blood vessel count, and proportional area in the bladder suburothelium and deeper submucosa of bladder biopsies of 52 women, including 26 with interstitial cystitis. Routine light microscopy features were examined and correlated with microvascular density.

RESULTS

In the bladder biopsies of women with interstitial cystitis there was a lower blood vessel count (p = 0.01), and a lower proportion of the total image consisted of blood vessel wall (p = 0.03) in the suburothelium than in control biopsies. We noted no difference in the blood vessel count of the deeper submucosa or in the degree of endothelial cell proliferation. Suburothelial blood vessel differences correlated with the degree of histological change, such as edema, inflammatory infiltrate and vascular congestion.

CONCLUSIONS

We found decreased microvascular density in the suburothelium but not in the deeper submucosa in bladder biopsies of women with interstitial cystitis.

Structure and blood supply of intrinsic lymph nodes in the wall of the rabbit urinary bladder--studies with light microscopy, electron microscopy, and vascular corrosion casting

The urinary bladder is especially subject to infection by virtue of its direct connection to the external urethral opening, and it is natural to anticipate the presence of a well-developed immunological mechanism to respond to this potential threat. The present study describes small, very highly vascular lymph nodes located in the wall of the rabbit bladder, which may be involved in a local response to foreign antigens. The vasculature and structure of these lymph nodes was described using a combination of vascular corrosion casting, ink injection, and light and electron microscopy. The distal abdominal aorta was cannulated, and after clearing the bladder vasculature with buffered saline, one of the following procedures was used: 1) the bladder was perfuse-fixed in preparation for light and electron microscopy; 2) the bladder vasculature was filled with India ink for vessel tracing; or 3) vascular corrosion casts of the vasculature were prepared by infusing resin comprised of a mixture of Mercox, methyl methacrylate monomer, and catalyst. The resulting casts were cleaned with KOH, formic acid, and water in preparation for scanning electron microscopy. Vascular casts and India ink injections revealed the presence of a number of isolated capillary tufts consisting of clusters of one to five "glomeruli," closely associated with the major vesicular vessels along the lateral walls of the bladder, and supplied by tertiary branches of these vessels. Light and electron microscopy showed that the capillary tufts represented the blood supply to small, ovoid lymph nodes located near the serosal surface of the bladder wall and usually restricted to the basal half of the bladder. These nodes were encapsulated and exhibited subcapsular sinuses, numerous small blood vessels, a limited number of high endothelial cells, and, occasionally, nerves and a follicular substructure. The nodes contained abundant lymphocytes, stellate stromal cells, macrophages, and eosinophils, but lacked the obvious cortical and medullary organization and germinal centers often seen in larger lymph nodes. Vascular corrosion casts, vascular ink injections, and microscopic examination confirmed the presence of small, highly vascular lymph nodes closely associated with the main vesicular vessels along the lateral walls of the rabbit bladder. A follicular substructure of the nodes appears to correspond with the "glomerular" capillary arrangement within the nodes as seen with corrosion casts. The rich blood supply may be indicative of the high metabolic demand of lymphatic tissue, and may be altered in response to the level of activity of the node. The close association between the lymphatic tissue and the rich blood supply to the nodes may allow a rapid mobilization of lymphocytes during a local immune response to foreign agents.

Experimental assessment of ureteral free autograft

OBJECTIVE

To establish the sequence of ureteral events under ischemic and desvascularized conditions but without immunologic interference.

MATERIALS AND METHODS

Sixty-two rats were divided into four groups. NU group (n 20) control group, normal ureter; SC group (n 15) only surgical control ureterolysis; NIAFG group (n 13) ureter used as non integrated autologous free graft; IAFG group (n 14): ureter used as integrated autologous free graft. Urographic, histologic and histomorphometric studies were performed.

RESULTS

We established ureteral changes in the NIAFG and IAFG groups, compared to the control groups (NU, SC). Surgical findings and urographic assessment revealed normal peristalsis with no ectasia in some cases, and no ureteral fistulas or extravasations were found in the IAFG group. Histologic findings showed preservation of the architecture of the three normal layers. Histomorphometric studies showed that ureterolysis caused edema in the lamina propria, while changes in ureter free graft depended on whether the ureter was integrated or not. In the NIAFG group only the urothelial layers showed differences and in the IAFG group the ureteral wall appeared thicker. Histomorphometric studies showed preservation of the normal histologic structures in all cases.

CONCLUSIONS

The rat ureter can be used as a free autologous graft and represents an experimental model for immunologic events. We may assume that the necrosis and fibrosis observed in transplanted ureters are secondary to rejection in some cases.