P.F. Keane

Comparative assessment of ureteral stent biomaterial encrustation

Long-term use of ureteral stents is hindered by the inherent problem of biomaterial encrustation which may lead to stone formation and attendant problems. The wide variety of polymeric biomaterials currently used for stent fabrication suggests that no single material is significantly superior to the others at resisting encrustation. A model representing upper urinary tract conditions was employed to compare the long-term struvite and hydroxyapatite encrustation of five materials currently used in the fabrication of ureteral stents. Silicone was least prone to struvite encrustation, followed by polyurethane, silitek, percuflex and hydrogel-coated polyurethane, in rank order. Similarly, silicone was least prone to hydroxyapatite encrustation, followed by silitek, polyurethane, percuflex and hydrogel-coated polyurethane. This study has shown that the problem of encrustation may limit the long-term use of ureteral stent biomaterials and suggests directions for improvement of biomaterials in this regard.

Morphological expression of KIT positive interstitial cells of Cajal in human bladder.

Purpose We investigated the 3-dimensional morphological arrangement of KIT positive interstitial cells of Cajal in the human bladder and explored their structural interactions with neighboring cells. Materials and Methods Human bladder biopsy samples were prepared for immunohistochemistry/confocal or transmission electron microscopy. Results Whole mount, flat sheet preparations labeled with anti-KIT (Merck, Darmstadt, Germany) contained several immunopositive interstitial cell of Cajal populations. A network of stellate interstitial cells of Cajal in the lamina propria made structural connections with a cholinergic nerve plexus. Vimentin positive cells of several morphologies were present in the lamina propria, presumably including fibroblasts, interstitial cells of Cajal and other cells of mesenchymal origin. Microvessels were abundant in this region and branched, elongated KIT positive interstitial cells of Cajal were found discretely along the vessel axis with each perivascular interstitial cell of Cajal associated with at least 6 vascular smooth muscle cells. Detrusor interstitial cells of Cajal were spindle-shaped, branched cells tracking the smooth muscle bundles, closely associated with smooth muscle cells and vesicular acetylcholine transferase nerves. Rounded, nonbranched KIT positive cells were more numerous in the lamina propria than in the detrusor and were immunopositive for anti-mast cell tryptase. Transmission electron microscopy revealed cells with the ultrastructural characteristics of interstitial cells of Cajal throughout the human bladder wall. Conclusions The human bladder contains a network of KIT positive interstitial cells of Cajal in the lamina propria, which make frequent connections with a cholinergic nerve plexus. Novel perivascular interstitial cells of Cajal were discovered close to vascular smooth muscle cells, suggesting interstitial cells of Cajal-vascular coupling in the bladder. KIT positive detrusor interstitial cells of Cajal tracked smooth muscle bundles and were associated with nerves, perhaps showing a functional tri-unit controlling bladder contractility.

The effect of antisense Bcl-2 oligonucleotides on Bcl-2 protein expression and apoptosis in human bladder transitional cell carcinoma

PURPOSE Bcl-2 is an important determinant of transitional cell carcinoma of the bladder recurrence and progression as well as a factor in patient response to chemotherapy or radiotherapy. We determined Bcl-2 down-regulation after antisense oligonucleotide therapy and synergism with mitomycin C in transitional cell carcinoma of the bladder. MATERIALS AND METHODS Bcl-2 protein was quantified using flow cytometry and immunohistochemistry in 4 bladder cancer cell lines, in bladder washings from 6 patients with carcinoma in situ and in 16 patient tumor samples. The synergistic effects of antisense oligonucleotides G3139 and 2009, and mitomycin C were investigated in 4 cell lines, while 2009 down-regulation was examined in 20 tumor explants in an ex vivo model. RESULTS Bcl-2 protein expression was found in all 4 cell lines and in 5 of the 6 cell populations derived from patients with carcinoma in situ. Of the 16 tumors 7 were classified positive by frozen section immunohistochemistry and quantitative flow cytometry. G3139 and 2009 down-regulated Bcl-2 protein expression in all 4 cell lines and 2009 down-regulated Bcl-2 protein expression in half of the Bcl-2 positive tumor specimens. There was only evidence in 1 cell line, T24/83, that Bcl-2 protein expression down-regulation enhanced mitomycin C induced apoptotic cell death. CONCLUSIONS Bcl-2 was expressed in a significant proportion of bladder tumors and in carcinoma in situ. Therefore, antisense oligonucleotides represent a viable strategy for Bcl-2 protein down-regulation. However, it may not always translate into an increased level of mitomycin C induced apoptosis in transitional cell carcinoma of the bladder.

Characterization and assessment of a novel poly(ethylene oxide)/polyurethane composite hydrogel (Aquavene) as a ureteral stent biomaterial.

The effective long-term use of indwelling ureteral stents is often hindered by the formation of encrusting deposits which may cause obstruction and blockage of the stent. Development of improved ureteral stent biomaterials capable of preventing or reducing encrustation is therefore particularly desirable. In this study, the suitability as a ureteral stent biomaterial of Aquavene, a novel poly(ethylene oxide)/polyurethane composite hydrogel was compared with that of silicone and polyurethane, two materials widely employed in ureteral stent manufacture. Examination of Aquavene in dry and hydrated states by confocal laser scanning microscopy, scanning electron microscopy, and atomic force microscopy showed the presence of numerous channels within a cellular matrix structure. The channel size increased considerably to as much as 10 microm in diameter in the hydrated state. Aquavene provided superior resistance to encrustation and intraluminal blockage over a 24-week period in a simulated urine flow model. Unobstructed urine flow continued with Aquavene at 24 weeks, whereas silicone and polyurethane stents became blocked with encrustation at 8 and 10 weeks, respectively. Weight loss within Aquavene on the order of 9% (w/w) over the 24-week flow period indicates that extraction of the noncrosslinked poly(ethylene oxide) hydrogel may be responsible for the prevention of encrustation blockage of this biomaterial. In the dry state, Aquavene was significantly harder than either silicone or polyurethane, as shown by Youngs modulus, and rapidly became soft on hydration. These additional properties of Aquavene would facilitate ease of stent insertion in the dry state past obstructions in the ureter and provide improved patient comfort on subsequent biomaterial hydration in situ. Aquavene is a promising candidate for use in the urinary tract, as it is probable that effective long-term urine drainage would be maintained in vivo. Further evaluation of this novel biomaterial is therefore warranted.

Evidence of prostate cancer screening in a UK region.

To examine the pattern of use of prostate‐specific antigen (PSA) testing in a UK region, where National Health Service policy does not recommend screening for prostate cancer.

Development of a model for assessment of biomaterial encrustation in the upper urinary tract.

A need exists for ureteral stent materials capable of preventing or reducing encrustation. The aim of this study, therefore, was to develop an in vitro model producing biomaterial encrustation similar to that on stents in vivo. Three models were designed and evaluated. Polyurethane stent sections were immersed in human urine (37 degrees C, 5% CO2): (1) with and (2) without crushed human kidney stone and (3) in an artificial urine (37 degrees C, 5% CO2). Encrustation of similar composition, as determined by infrared spectroscopy, X-ray diffraction and energy dispersive X-ray analysis, formed on stent materials in vivo, in artificial urine and in human urine with crushed kidney stone. Magnesium ammonium phosphate (struvite) and calcium phosphate (hydroxyapatite) predominated in all encrustations. The reproducibility and ease of use of the artificial urine model provided optimum encrustation assessment of materials presently used in ureteral stents and evaluation of novel biomaterials.

Sequential polyurethane–poly(methylmethacrylate) interpenetrating polymer networks as ureteral biomaterials: mechanical properties and comparative resistance to urinary encrustation

The mechanical properties and resistance to urinary encrustation of sequential-interpenetrating polymer networks (IPNs) composed of polyurethane (PU) and polymethylmethacrylate (PMMA), have been described. Mechanical properties were determined using tensile testing and dynamic mechanical analysis, whereas resistance to encrustation was examined using an in vitro model for encrustation simulating in vivo encrustation. Maximum and minimum tensile strength at break, Young’s modulus, storage and loss moduli were associated with PMMA and PU, respectively. IPNs demonstrated intermediate mechanical properties which were dependent on the concentrations of the component polymers. Conversely, maximum elongation at break was observed for PU and this parameter decreased as the concentration of PMMA increased in the IPN. The dynamic mechanical damping parameter, tan δ, was similar for all IPNs at 37°C. Increased advancing and decreased receding contact angles were observed for IPNs in comparison with the native PU. The rate and extent of encrustation, measured as the percentage surface coverage, was similar for PU, IPNs and PMMA. In contrast, encrustation on polyhydroxyethylmethacrylate, a model hydrogel, was greater than observed for the IPNs or component polymers. No apparent correlation was observed between the rate and/or extent of encrustation and polymer contact angle. It is concluded that these IPNs may be of clinical benefit in patients providing stent resistance to extrinsic compression of the ureter in comparison with native PU. The comparable resistance to encrustation between the IPNs and PU indicates that the use of IPNs should not be restricted in this regard.

Apoptosis and its clinical significance for bladder cancer therapy

the confusion over definitions of cell death and the need Introduction to view apoptosis within the broader context as a process of growth regulation. Apoptosis describes the Apoptosis is a unique form of cell death in which the cell activates a self-destruct mechanism, causing its events of cell death which occur throughout normal development and as a response to a variety of initiation death. The realization that most, if not all, anticancer agents eCect tumour killing through the activation of stimuli. Apoptosis is often incorrectly referred to as being synonymous with programmed cell death (PCD). apoptosis has emphasized the key role of the process in tumour growth and cytotoxic resistance [1]. In the last Not all apoptosis is PCD but, as implied by the term PCD, cell death is predetermined by a genetic clock decade, there has been intensive scientific research in the field and as the understanding of the genetic moduwhich is activated at an appropriate time [6,7]. An example of PCD can be seen in the perfect timing of the lation of the apoptotic process evolves, new therapeutic options arise. A critical development in the current death of individual cells in invertebrates and in embryonic development [8]. Thus PCD should be reserved for understanding of cytotoxic cell killing is that DNA damage induced by an anticancer agent does not necesdescribing death that is a normal part of life or development, but not related to a specific form of sarily result in cell death. Thus, cells cannot be seen as passive recipients of drug-induced damage. Rather, eCeccell death. Another form of cell death, necrosis, is distinct from tive killing involves the cell being able to activate the genes involved in the apoptotic process [2,3]. Therefore, apoptosis and occurs after injury or toxic damage. It is not seen in normal development and is fundamentally inappropriate expression of oncogenes and tumour suppressor genes (TSGs) is fundamental to the sequential diCerent from apoptosis both in its nature and biological significance [9,10]. In necrosis, the cell is unable events which lead to the development of cancer and resistance to cytotoxic therapy [4]. to maintain ionic homeostasis and metabolic collapse results. Consequently, the cell swells and the membranes In bladder cancer the mechanisms of chemoresistance are not fully understood and this may in part be due to a leak, resulting in an inflammatory reaction. In contrast, during apoptosis, the cell membrane maintains its integlack of knowledge of the processes involved in apoptosis. However, many investigators within the bladder cancer rity and cytosolic proteins cross-link to produce a net which envelopes the cell and prevents leakage of cellular research community are now addressing the issue of drug resistance and apoptosis. This review will discuss the curstructures. Therefore, in apoptosis, the surrounding tissue architecture is not disrupted and there is no rent understanding of the concepts of apoptosis and the clinical significance of the processes involved in resistance inflammation [11]. to cytotoxic therapy in bladder cancer.

Baseline prostate-specific antigen level and risk of prostate cancer and prostate-specific mortality: diagnosis is dependent on the intensity of investigation.

Background: When considering prostate biopsy, men and their physicians must balance the potential benefits of early diagnosis of localized cancer with the implications of overdiagnosis of clinically insignificant cancers. We investigated the risk of prostate cancer and prostate cancer–specific and all-cause mortality by baseline prostate-specific antigen (PSA) level in a population-based cohort study in Northern Ireland, where PSA screening is not recommended and where low to moderately raised (<10.0 ng/mL) PSA levels were not routinely investigated. Methods: From a regional electronic database of PSA results, men who had their initial PSA between January 1, 1994 and December 31, 1998 were identified and followed for diagnosis of prostate cancer and prostate cancer–specific and all-cause mortality until December 31, 2003. Results: 68,354 men (mean age, 65.2 years) were included, with 50,676 (74.1%) having a baseline PSA of <4.0 ng/mL; 402 (0.8%) of these were subsequently diagnosed with prostate cancer. PSA level was positively associated with risk of prostate cancer and prostate-specific mortality. In men with baseline PSA <4.0 ng/mL, the rate of prostate cancer and high-grade cancer diagnosis was <2 and <1 cases per 1,000 person-years, respectively, whereas prostate-specific mortality was very low (0.18 cases per 1,000 person-years) compared with overall mortality (28.71 cases per 1,000 person-years). Conclusion: Following a PSA result, men need to be aware not only of the risk of prostate cancer but also of having cancer that may cause them harm during their lifetime or, more importantly, kill them. These data should inform and reassure men of their risk of clinically significant prostate cancer. (Cancer Epidemiol Biomarkers Prev 2008;17(2):271–8)

Mechanical performance of polyurethane ureteral stents in vitro and ex vivo

A serious problem associated with the use of ureteral stents is fracture in situ. Following clinical observations of fracture of polyurethane stents in vivo, this study examined the mechanical properties of 17 polyurethane stents (double-J containing drainage holes) retrieved from patients over a 24-week period of insertion. In addition, stents were immersed in human and artificial urine in an in vitro model at 37 degrees C to determine their general propensity to fracture. Mechanical properties of ureteral stents were examined using the standard ASTM D-412 tensile test and by the novel application of dynamic mechanical analysis (DMA). The ultimate tensile strength and elongation at break (but not the Youngs modulus) of unused polyurethane stent sections containing side-drainage holes were greater than stent sections devoid of side-drainage holes. No correlations were observed between increased or decreased Youngs modulus, ultimate tensile strength or elongation at break of polyurethane stents and their time of immersion in either human urine or artificial urine in simulated upper urinary tract conditions of 37 degrees C and 5% CO2. Similarly, no correlations were observed between Youngs modulus, ultimate tensile strength or elongation of polyurethane stents and stent dwell time in situ. DMA of retrieved stents revealed that their tan delta value and storage modulus did not differ significantly from unused stents following dwell times in situ of up to 24 weeks. No changes in the glass transition temperatures were observed in retrieved stents. Although patient variation was observed, the results indicate that the polyurethane stents examined in vitro and following removal from patients did not exhibit any greater propensity to fracture than their unused counterparts. Fracture of retrieved polyurethane stents, arising in vivo and also during subsequent tensile testing, was observed to occur along the drainage holes, suggesting that elimination of these holes will reduce the incidence of polyurethane ureteral stent fracture in use.