[Acellular matrix for functional reconstruction of the urogenital tract. Special form of "tissue engineering"?]. / Azelluläre Matrix zur funktionellen Rekonstruktion des Urogenitaltraktes. Eine Sonderform des "tissue engineering?"

Organ substitution and reconstruction of the urogenital system still poses a problem regarding an adequate substitute. Usually non-organ-specific materials are used for reconstruction (bowl, buccal mucosa). This nonspecific tissue can cause side effects that result from the origin and the natural function. Different groups have shown that an acellular matrix graft in the urinary bladder and the urethra served as a scaffold for complete regeneration of all organ wall components and that this organ-specific regeneration simultaneously facilitates functional restitution. New approaches will presumably effect better regeneration after seeding the matrix with organ-specific cells (i.e., urothelial cells). Smaller studies on genital reconstructive surgery could show that vaginal substitution with an acellular matrix might be possible or that there could be a possible substitute for the tunica during surgical treatment of Peyronie's disease.

In vitro construction of urinary bladder wall using porcine primary cells reseeded on acellularized bladder matrix and small intestinal submucosa.

BACKGROUND: Partial or radical cystectomy requires replacement of the urinary reservoir normally achieved by using small or large bowel segments. Our aim was to establish tissue engineering of an bioartificial bladder wall using primary cultures of porcine urothelial (pUC) and bladder smooth muscle cells (pSMC) to be reseeded on different acellular biological matrices. METHODS: Primary porcine cultures of pUC and pSMC were established from open bladder biopsy material 25 mm2 in size. Acellular matrix was generated either from a) porcine bladder wall segments or b) tubular small intestinal submucosa with the still attached decellularized muscularis layer. Reseeding of these matrices with primary cells was done in a two-dimensional static model and in a three-dimensional rotating bioreactor perfused with cell culture medium for a period of 6 weeks. RESULTS: Prior to reseeding the cultured cells were characterized as pUC and pSMC by immunohistochemical staining with either anti-keratin 7 or anti-alpha actin. For both matrices a reseeded double layer cell system of pUC and pSMC could be identified after incubation in the described systems for 6 weeks. CONCLUSIONS: Our results document successful generation of tissue engineered urinary bladder wall, which can be used in further large animal transplantation experiments.

Tunica albuginea acellular matrix graft for penile reconstruction in the rabbit: a model for treating Peyronie's disease.

OBJECTIVE: To evaluate the use of an acellular matrix graft of the tunica albuginea for functional penile reconstruction in severe cases of Peyronie's disease. MATERIALS AND METHODS: In 18 rabbits, an acellular matrix graft of the tunica albuginea was used to cover a 4 x 8 mm tunical defect, and six animals each were killed 1, 3 and 6 months later; four unoperated animals served as histological controls. Before death an erection was induced by papaverine, with the quality classified on a scale of 0-5, and cavernosography performed. After death the penis was prepared for histological study, and the cell number, collagen and elastic fibre content evaluated in the regenerated matrix, and in control specimens and four unimplanted matrices. RESULTS: Of 18 experimental animals, 11 had normal erections before death, four had slight penile deviation and three developed no erection. Failure was caused by severe postoperative haematoma, resulting in scar tissue. There was no graft rejection. Histologically there was no difference between natural and regenerated tunica. The collagen content and cell number were not significantly different in regenerated and control samples. There were significantly fewer elastic fibres in the unimplanted grafts and the 1-month group, but in later samples this difference was no longer evident. CONCLUSION: The homologous acellular matrix graft of the tunica albuginea warrants further evaluation as an alternative treatment in Peyronie's disease, despite some postoperative failures. The advantage of this orthotopic biomaterial is its rapid integration, with no rejection.

Advances in uroradiological imaging.

The development of new imaging techniques and the refinement of established methods in uroradiological imaging is proceeding rapidly. In the last few years several important developments have been implemented in the routine diagnostic evaluation of urological patients.A milestone is the recent advent of multidetector helical computed tomography (CT), enabling the radiologist to provide the clinician with high-quality three-dimensional (3-D) reconstructions of the urological organs. Powerful workstations are an indispensable tool in the post-processing of CT and magnetic resonance imaging (MRI)data. Significant advances in imaging were obtained in the fields of oncological imaging (e.g. prostate MRI and spectroscopic imaging), paediatric uroradiology(e.g. MR urography) and the evaluation of stone disease by unenhanced helical CT.

Time dependent smooth muscle regeneration and maturation in a bladder acellular matrix graft: histological studies and in vivo functional evaluation.

PURPOSE: We evaluated the time dependence of smooth muscle regeneration and restoration of in vivo functional properties in bladder augmented with a bladder acellular matrix graft. MATERIALS AND METHODS: A total of 45 Sprague-Dawley rats underwent augmentation cystoplasty with a bladder acellular matrix graft. Two rats each were sacrificed at various intervals within the first 21 days and 6 each were sacrificed at 4, 8 and 12 weeks. This second group underwent preoperative and postoperative assessment of bladder function, including cystometry, electrostimulation and stimulation with ice water, potassium and carbachol, as well as labeling of the bladder wall by the injection of fluorescent microspheres. After sacrifice slides of the bladders prepared for hematoxylin and eosin, trichrome, KI67, vimentin, desmin, smooth muscle specific alpha-actin and fluorescent microspheres were evaluated. RESULTS: Within 2 weeks the number of cells in the matrix as well as the proliferation index increased rapidly and then decreased gradually. Erythrocytes and inflammatory cells were found in the matrix within 2 to 4 days, followed by fibroblasts. A bladder host-to-matrix shift was evident by the appearance of microspheres in the matrix. Cell marker expression indicated the early appearance of vimentin and alpha-actin within the first 10 days. Distinct desmin expression was observed later, when the first smooth muscle cells were recognized. Functional evaluation revealed restored bladder function at 12 weeks. CONCLUSIONS: The time dependent increase of muscle cell markers during smooth muscle cell regeneration in a bladder acellular matrix graft is concordant with the progressive restoration of bladder function. These results may support the bladder acellular matrix graft concept for clinical application.

Heterologous acellular matrix graft for reconstruction of the rabbit urethra: histological and functional evaluation.

PURPOSE: In a rabbit model we evaluated urethral replacement by a free heterologous dog acellular matrix graft and compared these results with those of a homologous graft with the exclusion of antigenicity as a major goal. MATERIALS AND METHODS: In 14 male New Zealand rabbits a 0.8 to 1.1 cm. segment of urethra was resected and replaced with a tubular acellular 1.0 to 1.5 cm. (mean 1.3) urethral matrix graft placed on an 8Fr feeding tube. Seven animals received a rabbit graft, 7 received a canine graft and 3 untreated rabbits served as controls. All animals underwent urethral pressure profile determination and retrograde urethrography before 8 and 6 were sacrificed at 6 and 8 months, respectively. Grafted and normal specimens were evaluated by histological testing. RESULTS: In all animals the acellular matrix graft remained in its original position. Histological examination showed complete epithelialization and progressive vessel infiltration. At 6 months more than a third of the homologous grafts had smooth muscle bundles but the heterologous grafts had only poorly disseminated smooth muscle. Picrosirius red stain demonstrated a shift in the ratio of collagen types I-to-III with an increase in type III in the processed homologous and heterologous matrices that did not change significantly postoperatively. At 8 months the urethral pressure profile detected no difference in control and matrix grafted animals, and urethrography did not readily differentiate host from implant. CONCLUSIONS: In the heterologous matrix all tissue components were present after 6 months with no signs of rejection and even gradual improvement with time. However, regenerated smooth muscle did not equal that in normal rabbit urethra and it was not well oriented. Even after 8 months only a few disseminated smooth muscle cells were evident. Most alpha-actin positive cells were surrounding the vessels. Although function was normal, the alteration in the collagen ratio effected by matrix production indicated that the matrix collagen appeared not to have been replaced by host collagen. The increase in collagen type III may explain the lack of stricture in the grafted animals on normal retrourethrography.

Tolterodine: an overview.

Tolterodine has emerged as a new anticholinergic drug to treat detrusor instability in recent years. This substance and its major metabolite DD01 exhibit a favourable effect-to-side-effect ratio for the bladder. Several clinical studies demonstrated the drug's efficacy in reducing the symptoms of an overactive bladder (urgency, urge incontinence and high micturition frequency) and in increasing functional bladder volume. With a clinical effectiveness comparable to oxybutynin, the side effect-profile measures up favourably to oxybutynin. Consequently, though some limitations need to be addressed, tolterodine can be regarded as the drug of first choice to treat overactive bladders in a variety of patient groups: the young (and otherwise healthy), the elderly, as well as in patients with renal and hepatic insufficiency. A new extended release formula of tolterodine has been launched that may improve patients' compliance.

Phosphodiesterase 1 inhibition in the treatment of lower urinary tract dysfunction: from bench to bedside.

Anticholinergic drugs are currently the therapy of choice to treat urgency and urge incontinence. However, muscarinergic receptor blockers with adequate selectivity for detrusor smooth muscle are not available. Also, in contrast to the normal detrusor, the unstable detrusor neurotransmission seems to be at least partially regulated by non-cholinergic (NANC) pathways. These factors may explain the common side effects and the limited clinical efficacy of these compounds. Specific modulation of intracellular second messenger pathways offers the possibility of organ selective manipulation of tissue function, specifically contraction and relaxation of smooth musculature. Because of their central role in the intracellular regulation of smooth muscle tone phosphodiesterases (PDEs) are an attractive pharmacological targets. The PDE 5 specific inhibitor sildenafil (Viagra) has revolutionized the treatment of patients with erectile dysfunction. Numerous other PDE inhibitors are currently under investigation for the treatment of various disorders. We investigated the role of PDEs in human detrusor smooth muscle. Our data demonstrate the presence of five PDE isoenzymes in human detrusor and suggest, for the first time, that the cAMP pathway and the calcium/calmodulin-stimulated PDE (PDE 1) are of functional importance in the intracellular regulation in this tissue in vitro. In addition. initial clinical data with the PDE 1 inhibitor vinpocetine in patients not responding to standard anticholinergic therapy indicate a possible role for vinpocetine in the treatment of urgency, urge incontinence and, possibly, low compliance bladder and interstitial cystitis. The results of a larger randomized, double-blind, placebo-controlled, multicenter trial with vinpocetine show a tendency in favor of vinpocetine over placebo; however, statistically significant results were documented for one parameter only. This might be due to the rather low dosage chosen and the small sample size. Further studies are necessary and currently underway to delineate the optimal dosage, indications and patient population. Modulation of intracellular key enzymes effecting second messenger metabolism, i.e. isoenzyme-selective PDE inhibition is a novel approach which possibly avoids the limitations of anticholinergic therapy in patients with lower urinary tract dysfunction.

[Healing of autologous cancellous bone transplants and hydroxylapatite ceramics in tibial segment defects. Value of ultrasonic follow up]. / Einheilung von autologen Spongiosatransplantaten und Hydroxylapatitkeramiken im Tibiasegmentdefekt. Wert der sonographischen Verlaufskontrolle.

The aim of this study was to develop and test a scoring system based on real-time ultrasonography (US), which is able to predict the healing of a bone defect filled with a bone graft substitute or cancellous bone graft. We implanted porous hydroxy-apatite (HA) ceramic blocks into a segmental defect in the tibia of 51 sheep; 14 sheep received autologous bone graft from the iliac crest. Follow-up times were 3, 6 and 12 months. With the exception of the 12-month animals, there was a minimum of 6 animals in each group. At the end of follow-up the tibiae were tested in torsion to failure. These results were correlated with radiographic and ultrasound scores measured on the same specimens. With the scoring system it was possible to describe the osseous integration of the HA ceramic or mineralisation of the cancellous bone graft. Sheep with ceramic implant that developed non-unions showed a significantly lower score than sheep with a sufficient implant integration. A significant correlation between these scores and the biomechanical results was found. We were able to define a cut-off within the scoring system which made the prediction of instability/non-union possible. In our model we were able to predict the osseous integration of HA ceramics and autologous cancellous bone grafts with the use of real-time ultrasound.

Sextant localization of prostate cancer: comparison of sextant biopsy, magnetic resonance imaging and magnetic resonance spectroscopic imaging with step section histology.

PURPOSE: We compared the accuracy of endorectal magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging with that of sextant biopsy for the sextant localization of prostate cancer. MATERIALS AND METHODS: Sextant biopsy, MRI, magnetic resonance spectroscopic imaging and radical prostatectomy with step section histology were done in 47 patients with prostate cancer. For each sextant we categorized biopsy and imaging results as positive or negative for cancer. Step section histology was used as the standard of reference. RESULTS: For sextant localization of prostate cancer MRI and magnetic resonance spectroscopic imaging were more sensitive but less specific than biopsy (67% and 76% versus 50%, and 69% and 68% versus 82%, respectively). The sensitivity of sextant biopsy was significantly less in the prostate apex than in the mid prostate or prostate base (38% versus 52% and 62%, respectively). MRI and magnetic resonance spectroscopic imaging had similar efficacy throughout the prostate compared with biopsy only as well as better sensitivity and specificity in the prostate apex (60% and 75%, and 86% and 68%, respectively). A positive biopsy or imaging result had 94% sensitivity for cancer and concordant positivity by all 3 tests was highly specific at 98%. CONCLUSIONS: Overall MRI and magnetic resonance spectroscopic imaging have accuracy similar to biopsy for intraprostatic localization of cancer and they are more accurate than biopsy in the prostate apex. These 2 imaging modalities may supplement biopsy results by increasing physician confidence when evaluating intraprostatic tumor location, which may be important for planning disease targeted therapy.

Tissue engineering from Adam to the zygote: historical reflections.

Tissue engineering, long a matter of myth and dream throughout the history of medicine, is now a practical reality. A wide spectrum of biological materials are used in the field of urology to treat disease and to overcome human disabilities, including tissue grafts and organ transplantation. Laboratory-engineered bioproducts for the off-the-shelf replacement and reconstruction of tissue is now almost at hand. This article presents a glimpse into the past by highlighting a number of early pioneering works in the field of tissue transplantation and cell culture technologies.