Tissue engineering for the replacement of organ function in the genitourinary system

Densified collagen tubular grafts for human tissue replacement and disease modelling applications

There is a significant need across multiple indications for an off-the-shelf bioengineered tubular graft which fulfils the mechanical and biological requirements for implantation and function but does not necessarily require cells for manufacture or deployment. Herein, we present a tissue-like tubular construct using a cell-free, materials-based method of manufacture, utilizing densified collagen hydrogel. Our tubular grafts are seamless, mechanically strong, customizable in terms of lumen diameter and wall thickness, and display a uniform fibril density across the wall thickness and along the tube length. While the method enables acellular grafts to be generated rapidly, inexpensively, and to a wide range of specifications, the cell-compatible densification process also enables a high density of cells to be incorporated uniformly into the walls of the tubes, which we show can be maintained under perfusion culture. Additionally, the method enables tubes consisting of distinct cell domains with cellular configurations at the boundaries which may be useful for modelling aortic disease. Further, we demonstrate additional steps which allow for luminal surface patterning. These results highlight the universality of this approach and its potential for developing the next generation of bioengineered grafts.

Biofabrication of a Tubular Model of Human Urothelial Mucosa Using Human Wharton Jelly Mesenchymal Stromal Cells

Several models of bioartificial human urothelial mucosa (UM) have been described recently. In this study, we generated novel tubularized UM substitutes using alternative sources of cells. Nanostructured fibrin-agarose biomaterials containing fibroblasts isolated from the human ureter were used as stroma substitutes. Then, human Wharton jelly mesenchymal stromal cells (HWJSC) were used to generate an epithelial-like layer on top. Three differentiation media were used for 7 and 14 days. Results showed that the biofabrication methods used here succeeded in generating a tubular structure consisting of a stromal substitute with a stratified epithelial-like layer on top, especially using a medium containing epithelial growth and differentiation factors (EM), although differentiation was not complete. At the functional level, UM substitutes were able to synthesize collagen fibers, proteoglycans and glycosaminoglycans, although the levels of control UM were not reached ex vivo. Epithelial differentiation was partially achieved, especially with EM after 14 days of development, with expression of keratins 7, 8, and 13 and pancytokeratin, desmoplakin, tight-junction protein-1, and uroplakin 2, although at lower levels than controls. These results confirm the partial urothelial differentiative potential of HWJSC and suggest that the biofabrication methods explored here were able to generate a potential substitute of the human UM for future clinical use.

Regenerative and engineered options for urethroplasty

Surgical correction of urethral strictures by substitution urethroplasty - the use of grafts or flaps to correct the urethral narrowing - remains one of the most challenging procedures in urology and is frequently associated with complications, restenosis and poor quality of life for the affected individual. Tissue engineering using different cell types and tissue scaffolds offers a promising alternative for tissue repair and replacement. The past 30 years of tissue engineering has resulted in the development of several therapies that are now in use in the clinic, especially in treating cutaneous, bone and cartilage defects. Advances in tissue engineering for urethral replacement have resulted in several clinical applications that have shown promise but have not yet become the standard of care.

Effect of Human Amniotic Fluid Stem Cells on Kidney Function in a Model of Chronic Kidney Disease

Kidney disease is a major medical problem globally. Chronic kidney disease (CKD) is a progressive loss of kidney function. It causes accumulation of waste and fluid in the body, eventually resulting in kidney failure as well as damaging other organs. Although dialysis and kidney transplantation have been used as primary treatments for renal disease, dialysis does not restore full renal function, and there is a shortage of donor kidneys for transplantation. Recent advances in cell-based therapies have offered a means to augment and restore renal function. Various types of cells have been tested to evaluate their therapeutic effects on injured kidneys. Among various types of cells, amniotic fluid stem cells (AFSCs) share advantages of both embryonic and adult stem cells, such as pluripotent activity, remarkable plasticity, and immunomodulatory effects, which may allow their future therapeutic use as an "off-the-shelf" cell source. AFSC presents advantages of both conventional pluripotent and adult stem cells, such as pluripotent activity, remarkable plasticity, and immunomodulatory effects. This study demonstrates that administration of human-derived AFSC facilitates functional and structural improvement in a rat model of CKD, and suggests that cell therapy with AFSC has potential as a therapeutic strategy to recover renal function in patients with CKD. Impact Statement Patients with chronic kidney disease (CKD) have limited treatment options, and renal transplantation is the only definitive treatment method that restores kidney function. However, challenges associated with transplantation, including donor organ shortage, rejection, and life-long immunosuppression, remain a problem. Recently, stem cell-based therapies have been proposed as an alternative approach to augment and restore renal function. In this study, we used human-derived amniotic fluid stem cells (AFSCs) to treat CKD in a rat model and demonstrated that AFSC treatment facilitated positive effects in terms of improvements of renal function.

Tissue engineering strategies for the induction of angiogenesis using biomaterials

Angiogenesis is touted as a fundamental procedure in the regeneration and restoration of different tissues. The induction of de novo blood vessels seems to be vital to yield a successful cell transplantation rate loaded on various scaffolds. Scaffolds are natural or artificial substances that are considered as one of the means for delivering, aligning, maintaining cell connection in a favor of angiogenesis. In addition to the potential role of distinct scaffold type on vascularization, the application of some strategies such as genetic manipulation, and conjugation of pro-angiogenic factors could intensify angiogenesis potential. In the current review, we focused on the status of numerous scaffolds applicable in the field of vascular biology. Also, different strategies and priming approaches useful for the induction of pro-angiogenic signaling pathways were highlighted.

Potential Use of Autologous Renal Cells from Diseased Kidneys for the Treatment of Renal Failure

Chronic kidney disease (CKD) occurs when certain conditions cause the kidneys to gradually lose function. For patients with CKD, renal transplantation is the only treatment option that restores kidney function. In this study, we evaluated primary renal cells obtained from diseased kidneys to determine whether their normal phenotypic and functional characteristics are retained, and could be used for cell therapy. Primary renal cells isolated from both normal kidneys (NK) and diseased kidneys (CKD) showed similar phenotypic characteristics and growth kinetics. The expression levels of renal tubular cell markers, Aquaporin-1 and E-Cadherin, and podocyte-specific markers, WT-1 and Nephrin, were similar in both NK and CKD kidney derived cells. Using fluorescence- activated cell sorting (FACS), specific renal cell populations were identified and included proximal tubular cells (83.1% from NK and 80.3% from CKD kidneys); distal tubular cells (11.03% from NK and 10.9% from CKD kidneys); and podocytes (1.91% from NK and 1.78% from CKD kidneys). Ultra-structural analysis using scanning electron microscopy (SEM) revealed microvilli on the apical surface of cultured cells from NK and CKD samples. Moreover, transmission electron microscopy (TEM) analysis showed a similar organization of tight junctions, desmosomes, and other intracellular structures. The Na⁺ uptake characteristics of NK and CKD derived renal cells were also similar (24.4 mmol/L and 25 mmol/L, respectively) and no significant differences were observed in the protein uptake and transport characteristics of these two cell isolates. These results show that primary renal cells derived from diseased kidneys such as CKD have similar structural and functional characteristics to their counterparts from a normal healthy kidney (NK) when grown in vitro. This study suggests that cells derived from diseased kidney may be used as an autologous cell source for renal cell therapy, particularly in patients with CKD or end-stage renal disease (ESRD).

Regeneration of rat corpora cavernosa tissue by transplantation of CD133+ cells derived from human bone marrow and placement of biodegradable gel sponge sheet

The objective is to develop an easier technique for regenerating corpora cavernosa tissue through transplantation of human bone marrow-derived CD133 + cells into a rat corpora cavernosa defect model. We excised 2 mm × 2 mm squares of the right corpora cavernosa of twenty-three 8-week-old male nude rats. Alginate gel sponge sheets supplemented with 1 × 10 4 CD133 + cells were then placed over the excised area of nine rats. Functional and histological evaluations were carried out 8 weeks later. The mean intracavernous pressure/mean arterial pressure ratio for the nine rats (0.34258 ± 0.0831) was significantly higher than that for eight rats with only the excision (0.0580 ± 0.0831, P = 0.0238) and similar to that for five rats for which the penis was exposed, and there was no excision (0.37228 ± 0.1051, P = 0.8266). Immunohistochemical analysis revealed that the nine fully treated rats had venous sinus-like structures and quantitative reverse transcription polymerase chain reaction analysis of extracts from their alginate gel sponge sheets revealed that the amounts of mRNA encoding the nerve growth factor (NGF), and vascular endothelial growth factor (VEGF) were significantly higher than those for rats treated with alginate gel sheets without cell supplementation (NGF: P = 0.0309; VEGF: P < 0.0001). These findings show that transplantation of CD133 + cells accelerates functional and histological recovery in the corpora cavernosa defect model.

Magnetization Transfer MR Imaging to Monitor Muscle Tissue Formation during Myogenic in Vivo Differentiation of Muscle Precursor Cells

Purpose To determine whether magnetization transfer (MT) magnetic resonance (MR) imaging may serve as a quantitative measure of the degree of fiber formation during differentiation of muscle precursor cells into engineered muscle tissue as a potential noninvasive monitoring tool in mice. Materials and Methods The study was approved by the local ethics committee (no. StV 01/2008) and the local Veterinary Office (license no. 99/2013). Human muscle progenitor cells (hMPCs) derived from rectus abdominis muscles were subcutaneously injected into CD-1 nude mice (CD-1 nude mice, Crl:CD1-Foxn1^nu; Charles River Laboratories, Wilmington, Mass) for development of muscle tissue. The mice underwent MR imaging examinations at 4.7 T at days 1, 3, 7, 14, 21, and 28 after cell transplantation by using a gradient-echo sequence with an MT prepulse and systematic variation of the off-resonance frequency (50-37 500 Hz) at an amplitude of 800°. Direct saturation was estimated from a Bloch equation simulation. The MT ratio (MTR) was correlated to immunohistochemistry findings, Western blot results, and results of myography. Data were analyzed by using one-way or two-way analysis of variance with the Sidak or Tukey multiple comparisons test. Results In the reference skeletal muscle, highest MT was found for 2500 Hz off-resonance frequency with an MTR ± standard deviation of 57.5% ± 3.5. The developing muscle tissue exhibited increasing MT values during the 28 days of myogenic in vivo differentiation and did not reach the values of native skeletal muscle. Mean values of MTR (2500 Hz) for hMPCs were 27.6% ± 6.3 (day 1), 24.7% ± 8.7 (day 3), 28.2% ± 5.7 (day 7), 35.9% ± 5.0 (day 14), 37.0% ± 7.9 (day 21), and 39.9% ± 8.1 (day 28). The results from MT MR imaging correlated qualitatively well with muscle tissue expression of specific skeletal markers, as well as muscle contractility. Conclusion MT MR imaging may be used to noninvasively monitor the process of myogenic in vivo differentiation of hMPCs as a biomarker of the quantity and quality of muscle fiber formation. ^© RSNA, 2016 Online supplemental material is available for this article.

The potential role of tissue-engineered urethral substitution: clinical and preclinical studies

Urethral strictures and anomalies remain among the difficult problems in urology, with urethroplasty procedures being the most effective treatment options. The two major types of urethroplasty are anastomotic urethroplasty and widening the urethral lumen using flaps or grafts (i.e. substitution urethroplasty). However, no ideal material for the latter has been found so far. Designing and selecting such a material is a necessary and challenging endeavour, driving the need for further bioengineered urethral tissue research. This article reviews currently available studies on the potentialities of tissue engineering in urethral reconstruction, in particular those describing the use of both acellular and recellularized tissue-engineered constructs in animal and human models. Possible future developments in this field are also discussed. Copyright © 2015 John Wiley & Sons, Ltd.

Organ bioengineering for the newborn

Regenerative medicine has recently been established as an emerging interdisciplinary field focused on the repair; replacement or regeneration of cells, tissues and organs. It involves various disciplines, which are focused on different aspects of the regeneration process such as cell biology, gene therapy, bioengineering, material science and pharmacology. In this article, we will outline progress on tissue engineering of specific tissues and organs relevant to paediatric surgery.

Tissue engineered scaffolds for an effective healing and regeneration: reviewing orthotopic studies

It is commonly stated that tissue engineering is the most promising approach to treat or replace failing tissues/organs. For this aim, a specific strategy should be planned including proper selection of biomaterials, fabrication techniques, cell lines, and signaling cues. A great effort has been pursued to develop suitable scaffolds for the restoration of a variety of tissues and a huge number of protocols ranging from in vitro to in vivo studies, the latter further differentiating into several procedures depending on the type of implantation (i.e., subcutaneous or orthotopic) and the model adopted (i.e., animal or human), have been developed. All together, the published reports demonstrate that the proposed tissue engineering approaches spread toward multiple directions. The critical review of this scenario might suggest, at the same time, that a limited number of studies gave a real improvement to the field, especially referring to in vivo investigations. In this regard, the present paper aims to review the results of in vivo tissue engineering experimentations, focusing on the role of the scaffold and its specificity with respect to the tissue to be regenerated, in order to verify whether an extracellular matrix-like device, as usually stated, could promote an expected positive outcome.

Prevention of stricture recurrence following urethral endoscopic management: what do we have?

OBJECTIVE

Strictures of the urethra are the most common cause of obstructed micturition in younger men and there is frequent recurrence after initial treatment. This review was performed to determine the best strategy for stricture recurrence prevention following urethral endoscopic management.

METHODS

We reviewed the published literature in PubMed, the Cochrane Library, and Google Scholar focusing on this intractable problem regardless of language restrictions. Outcomes of interest included the study methods and the applied strategy's efficacy. The level of evidence and grade of recommendations of included studies were appraised with an Oxford Centre for Evidence-Based Medicine Scale.

RESULTS

Currently, numerous techniques, including catheterization, repeated dilation, brachytherapy, and intraurethral use of various antifibrosis agents, have been employed to oppose the process of wound contraction or regulate the extracellular matrix. But unfortunately, none of these techniques or agents have demonstrated efficacy with enough evidence.

CONCLUSIONS

Although lots of strategies are available, still, we do not have a suitable, single optimum solution for all the conditions. The clinical decision of stricture-recurrence-prevention techniques should be carefully tailored to every individual patient. As the studies are not sufficient, more efforts are warranted to address this interesting but challenging issue.

Integration of collagen matrices into the urethra when implanted as onlay graft

OBJECTIVE

To assess the integration of decellularized heterologous collagen matrices into the urethra, when implanted with no cells or when seeded with autologous smooth muscle cells.

MATERIALS AND METHODS

Eighteen New Zealand rabbits were randomly assigned to two groups: Group I (n = 9) - animals undergoing urethral segment resection with interposition of a patch of heterologous collagen matrix seeded with autologous smooth muscle cells; Group II (n = 9) - animals undergoing resection of a urethral segment with interposition of a decellularized heterologous collagen matrix patch. Two animals from each group were sacrificed on postoperative days seven, fourteen and twenty-eight; three animals from each group were sacrificed at the end of three postoperative months. At the end of the third month one animal from each group underwent urethroscopy for urethral integrity assessment and one animal from each group had its microcirculation image captured by a SDF device (Side-stream Dark Field - Microscan Analysis Software). One animal from each group in each euthanasia period underwent cystourethrography so as the urethra could be viewed at flow time. The matrices integration was assessed through histological examination using hematoxylin and eosin (H & E), Masson trichrome (MT), Picrosirius red and Von Willebrand staining. In a blind study with two pathologists all the slides were studied.

RESULTS

The matrices whether seeded or not with autologous muscle cells were able to restore the architecture of the urethra, but were eliminated from the first week on, before incorporation. Microcirculation of the neourethra, at the end of the third month, showed the same characteristics as a normal urethra in both groups of animals.

CONCLUSION

Natural heterologous matrices implanted in the urethra as onlay graft were not incorporated into its walls but were able to fully restore the cell architecture of the organ, regardless of being seeded or not with autologous muscle cells.

Epithelial-differentiated adipose-derived stem cells seeded bladder acellular matrix grafts for urethral reconstruction: an animal model

The limited amount of available epithelial tissue is considered a main cause of the high rate of urethral reconstruction failures. The aim of this study was to investigate whether epithelial-differentiated rabbit adipose-derived stem cells (Epith-rASCs) could play a role of epithelium in vivo functionally and be a potential substitute of urothelium. Substitution urethroplasty was performed to repair an anterior urethral defect in male New Zealand rabbits using Epith-rASCs seeded bladder acellular matrix grafts (BAMGs) after 5-bromo-2'-deoxyuridine (BrdU) labeling, based on the in vitro epithelial induction system we previously described. Urethroplasty with cell-free BAMGs and with undifferentiated rASCs (Und-rASCs) seeded BAMGs were performed as controls. After surgery, a notable amelioration of graft contracture and recovery of urethral continuity were observed in the Epith-rASCs/BAMG group by retrograde urethrograms and macroscopic inspection. Immunofluorescence revealed that the BrdU-labeled Epith-rASCs/Und-rASCs colocalized with cytokeratin 13 or myosin. Consistent with the results of western blotting, at early postimplantation stage, the continuous epithelial layer with local multilayered structure was observed in the Epith-rASCs/BAMG group, whereas no significant growth and local monolayer growth profile of epithelial cells were observed in the BAMG and Und-rASCs/BAMG group, respectively. The results showed that Epith-rASCs could serve as a potential substitute of urothelium for urethral tissue engineering and be available to prevent lumen contracture and subsequent complications including recurrent stricture.

Evaluation of electrospun bioresorbable scaffolds for tissue-engineered urinary bladder augmentation

Tissue engineering represents a potential and valuable approach for the treatment of urologic pathologies. Bioresorbable polymeric scaffolds can be regarded as effective platforms to surgically treat bladder diseases and subsequently guide the formation of novel tissue after implantation. To this aim, the evaluation of electrospun scaffolds made up of poly(ε-caprolactone) blended with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is presented here. Firstly, the microstructure and the viscoelastic/mechanical properties of the electrospun fabrics were investigated. Then, the in vivo response was assessed by performing a urinary bladder augmentation using female Wistar rats as an animal model. 15 days after the surgical procedure, the scaffolds were covered by regenerative urothelium up to 50%, which increased to 50-100% after 30 days. These encouraging results, collected in the 90-day follow-up, clearly showed the potential applications of tissue engineering in the urologic field. A longer in vivo evaluation is currently underway.

Collagen--emerging collagen based therapies hit the patient

The choice of biomaterials available for regenerative medicine continues to grow rapidly, with new materials often claiming advantages over the short-comings of those already in existence. Going back to nature, collagen is one of the most abundant proteins in mammals and its role is essential to our way of life. It can therefore be obtained from many sources including porcine, bovine, equine or human and offer a great promise as a biomimetic scaffold for regenerative medicine. Using naturally derived collagen, extracellular matrices (ECMs), as surgical materials have become established practice for a number of years. For clinical use the goal has been to preserve as much of the composition and structure of the ECM as possible without adverse effects to the recipient. This review will therefore cover in-depth both naturally and synthetically produced collagen matrices. Furthermore the production of more sophisticated three dimensional collagen scaffolds that provide cues at nano-, micro- and meso-scale for molecules, cells, proteins and bulk fluids by inducing fibrils alignments, embossing and layered configuration through the application of plastic compression technology will be discussed in details. This review will also shed light on both naturally and synthetically derived collagen products that have been available in the market for several purposes including neural repair, as cosmetic for the treatment of dermatologic defects, haemostatic agents, mucosal wound dressing and guided bone regeneration membrane. There are other several potential applications of collagen still under investigations and they are also covered in this review.

Urethral reconstruction with tissue engineering and RNA interference techniques in rabbits

OBJECTIVE

To investigate the feasibility of replacing urinary epithelial cells with oral keratinocytes and transforming growth factor β (TGF-β)1 siRNA transfected fibroblasts seeded on bladder acellular matrix graft (BAMG) to reconstruct urethra.

METHODS

Autologous oral keratinocytes and TGF-β1 siRNA transfected fibroblasts were seeded onto BAMGs to obtain a tissue-engineered mucosa. The tissue-engineered mucosa was assessed using morphology and scanning electron microscopy. In 27 male rabbits, a ventral urethral mucosal defect was created. Urethroplasty was performed with autogenic oral keratinocyte and TGF-β1 siRNA transfected fibroblast-seeded BAMGs (9 rabbits, group 1), with autogenic oral keratinocyte-seeded BAMGs (9 rabbits, group 2) or with BAMGs with no cell seeding (9 rabbits, group 3). Retrograde urethrography and histological analyses were performed to evaluate the results of urethroplasty.

RESULTS

In vitro, oral keratinocytes and TGF-β1 siRNA transfected fibroblasts had good biocompatibility with BAMGs. In vivo, the urethra kept a wide caliber in groups 1 and 2. Strictures were observed in group 3. Histologically, the retrieved urethra in group 3 showed fibrosis and inflammation during 6 months. Stratified epithelial layer regenerated in group 2, whereas there was no evidence of formation of capillary in the epithelial lower layer during the study period. Stratified epithelial layer and formation of capillary in the epithelial lower layer were evident after 6 months in group 1.

CONCLUSION

Our study suggested that oral keratinocytes and TGF-β1 siRNA transfected fibroblasts could be used as a source of seed cells for urethral tissue engineering.

Bladder Bioengineering: Our Experience

Background

Tissue engineering techniques aim to substitute or restore the structure and function of organs and systems. The bladder has been recently considered as a promising organ for tissue engineering regeneration for augmentation or substitution. We present our experience on an experimental model and a pilot clinical study.

Methods

The experimental model: 10 minipigs underwent 50% volume cystectomy and bladder wall substitution using a 5 × 4 cm acellular intestinal submucosa membrane as graft, covered by omentum. In 4 pigs, autologous stem cells, bone marrow-derived, were injected into the scaffold. The animals were sacrificed at 5 weeks, and 3 months from grafting. The clinical study: 5 exstrophic patients, 8–17 years old (mean 10.4 years), presenting poor bladder capacity and compliance after bladder closure and urethra-genitalia reconstruction, who refused enterocystoplasty received intestinal submucosa membrane (cm 5 × 4) bladder grafting. Follow-up lasted 3 years.

Results

All animals but 1 survived. The regenerated bladders had normal capacity. The newly developed wall was lined by normal looking mucosa. At histology, 3 layers were well defined: urothelium (inner), fibrocells and muscular cells within rich connective tissue (intermediate) and a well vascularized adventitial coat. No residual scaffold was observed at 3 months. The muscular component was 28% in the engineered bladder wall, versus 44% in the native wall (p<0.05). In the clinical study at 6 months' follow-up, bladder capacity increased from 102 mls to 136 mls (mean). The difference was significant (p<0.05). At biopsy, the newly generated bladder wall appeared similar to the animal model histology. No complications occurred, but 2 patients required enterocystoplasty at 3 years' follow-up.

Conclusions

Bladder regeneration is feasible by tissue engineering techniques in animal models and in humans. Functional and histological results are not as with normal bladder wall. Further improvements are necessary before any extensive clinical application.

Bladder augmentation using acellular collagen biomatrix: a pilot experience in exstrophic patients

PURPOSE

A preliminary experience on in vivo bladder wall regeneration in a subset of patients born with exstrophy-epispadias complex is reported. The objective was to improve bladder capacity and compliance without bowel augmentation.

METHODS

Five patients (3 males, 2 females), mean age 10.4 years, presenting poor bladder capacity and compliance after complete exstrophy repair, underwent bladder augmentation using small intestinal submucosa (SIS) scaffold. Ultrasonography, cystoscopy with cystogram, assessment of bladder volume and compliance and bladder biopsy were performed before surgery (T0), at 6 (T1) and 18 months (T2) follow-up. Histology was compared with normal bladder specimens. Wilcoxon test was adopted for statistics.

RESULTS

Bladder capacity and compliance resulted increased (+30%) at T1 (p < 0.05) and remained stable at T2, despite dry intervals did not changed significantly. Bladder biopsy at T1 showed no evidence of SIS, but normal transitional mucosa and sero-muscular layer containing smooth muscle fascicles, small nerve trunks and vessels within abundant type-3 collagen. Muscle/collagen ratio was decreased compared with controls at T1 and T2 (p < 0.05). No kidney damage, bladder diverticula, or stones were observed at 3 years follow-up.

CONCLUSIONS

Bladder regeneration was feasible in these patients, but bladder capacity and compliance was poorly increased to obtain significant clinical benefit. Histology showed poor muscle components. The acellular matrix grafting failed to provide long-term effective results in terms of continence achievement.

Tissue engineering and stem cell application of urethroplasty: from bench to bedside

OBJECTIVE

To review the advances in the basic research and clinical application of tissue engineering and stem cell technology in urethral reconstruction. Urethral defects resulting from congenital malformations, trauma, inflammation, or cancer are a common urologic issue. Traditional urethral reconstruction is associated with various complications. Tissue engineering and stem cell technology hold novel therapeutic promise for urethral reconstruction.

METHODS

One of us searched the PubMed database (January 1999 to January 2011) using the English search terms "tissue engineering," "stem cells," "urethral reconstruction," and "urethra." A total of 86 reports were retrieved. After the repetitive and irrelevant reports were excluded, 40 were included in the final analysis. The review outlined and evaluated the advances in basic research and clinical application and the current status and prospects of tissue engineering and stem cell technology in urinary reconstruction.

RESULTS

Two therapeutic strategies are available for urethral reconstruction using tissue engineering: the acellular matrix bioscaffold model and the cell-seeded bioscaffold model. The acellular matrix bioscaffold model has been successfully used in the clinic and the cell-seeded bioscaffold model is making its transition from bench to bedside.

CONCLUSION

Stem cells can provide the seed cells for urologic tissue engineering, but much basic research is still needed before their clinical use is possible.

Adult human CD133/1(+) kidney cells isolated from papilla integrate into developing kidney tubules

Approximately 60,000 patients in the United States are waiting for a kidney transplant due to genetic, immunologic and environmentally caused kidney failure. Adult human renal stem cells could offer opportunities for autologous transplant and repair of damaged organs. Current data suggest that there are multiple progenitor types in the kidney with distinct localizations. In the present study, we characterize cells derived from human kidney papilla and show their capacity for tubulogenesis. In situ, nestin(+) and CD133/1(+) cells were found extensively intercalated between tubular epithelia in the loops of Henle of renal papilla, but not of the cortex. Populations of primary cells from the renal cortex and renal papilla were isolated by enzymatic digestion from human kidneys unsuited for transplant and immuno-enriched for CD133/1(+) cells. Isolated CD133/1(+) papillary cells were positive for nestin, as well as several human embryonic stem cell markers (SSEA4, Nanog, SOX2, and OCT4/POU5F1) and could be triggered to adopt tubular epithelial and neuronal-like phenotypes. Isolated papillary cells exhibited morphologic plasticity upon modulation of culture conditions and inhibition of asymmetric cell division. Labeled papillary cells readily associated with cortical tubular epithelia in co-culture and 3-dimensional collagen gel cultures. Heterologous organ culture demonstrated that CD133/1(+) progenitors from the papilla and cortex became integrated into developing kidney tubules. Tubular epithelia did not participate in tubulogenesis. Human renal papilla harbor cells with the hallmarks of adult kidney stem/progenitor cells that can be amplified and phenotypically modulated in culture while retaining the capacity to form new kidney tubules. This article is part of a Special Issue entitled: Polycystic Kidney Disease.

Bladder regeneration by collagen scaffolds with collagen binding human basic fibroblast growth factor

PURPOSE

Studies show that basic fibroblast growth factor can promote bladder regeneration. However, the lack of targeting delivery approaches limits its clinical application. We investigated a collagen based targeting system for bladder regeneration. A collagen binding domain was added to the native basic fibroblast growth factor N-terminal to allow it to bind to collagen.

MATERIALS AND METHODS

Sprague-Dawley rats underwent partial cystectomy. Collagen scaffolds loaded with collagen binding domain basic fibroblast growth factor, native basic fibroblast growth factor or phosphate buffered saline were grafted to the remaining host bladders, respectively. At days 30 and 90 reconstructed bladders were evaluated by histological analysis and urodynamics.

RESULTS

This targeting basic fibroblast growth factor delivery system induced satisfying bladder histological structures. It promoted more vascularization and smooth muscle cell ingrowth. Urodynamics revealed well accommodated bladder tissue with volume capacity and compliance.

CONCLUSIONS

Results show that the targeting delivery system consisting of collagen binding domain basic fibroblast growth factor and collagen membranes induced better bladder regeneration at the injury site. Thus, this targeting delivery system may be an effective strategy for bladder regeneration with potential clinical applications.

Urinary bladder smooth muscle engineered from adipose stem cells and a three dimensional synthetic composite

Human adipose stem cells were cultured in smooth muscle inductive media and seeded into synthetic bladder composites to tissue engineer bladder smooth muscle. 85:15 Poly-lactic-glycolic acid bladder dome composites were cast using an electropulled microfiber luminal surface combined with an outer porous sponge. Cell-seeded bladders expressed smooth muscle actin, myosin heavy chain, calponinin, and caldesmon via RT-PCR and immunoflourescence. Nude rats (n=45) underwent removal of half their bladder and repair using: (i) augmentation with the adipose stem cell-seeded composites, (ii) augmentation with a matched acellular composite, or (iii) suture closure. Animals were followed for 12 weeks post-implantation and bladders were explanted serially. Results showed that bladder capacity and compliance were maintained in the cell-seeded group throughout the 12 weeks, but deteriorated in the acellular scaffold group sequentially with time. Control animals repaired with sutures regained their baseline bladder capacities by week 12, demonstrating a long-term limitation of this model. Histological analysis of explanted materials demonstrated viable adipose stem cells and increasing smooth muscle mass in the cell-seeded scaffolds with time. Tissue bath stimulation demonstrated smooth muscle contraction of the seeded implants but not the acellular implants after 12 weeks in vivo. Our study demonstrates the feasibility and short term physical properties of bladder tissue engineered from adipose stem cells.

The role of polymer nanosurface roughness and submicron pores in improving bladder urothelial cell density and inhibiting calcium oxalate stone formation

Synthetic polymers have been proposed for replacing resected cancerous bladder tissue. However, conventional (or nanosmooth) polymers used in such applications (such as poly(ether) urethane (PU) and poly-lactic-co-glycolic acid (PLGA)) often fail clinically due to poor bladder tissue regeneration, low cytocompatibility properties, and excessive calcium stone formation. For the successful reconstruction of bladder tissue, polymer surfaces should be modified to combat these common problems. Along these lines, implementing nanoscale surface features that mimic the natural roughness of bladder tissue on polymer surfaces can promote appropriate cell growth, accelerate bladder tissue regeneration and inhibit bladder calcium stone formation. To test this hypothesis, in this study, the cytocompatibility properties of both a non-biodegradable polymer (PU) and a biodegradable polymer (PLGA) were investigated after etching in chemicals (HNO(3) and NaOH, respectively) to create nanoscale surface features. After chemical etching, PU possessed submicron sized pores and numerous nanometer surface features while PLGA possessed few pores and large amounts of nanometer surface roughness. Results from this study strongly supported the assertion that nanometer scale surface roughness produced on PU and PLGA promoted the density of urothelial cells (cells that line the interior of the bladder), with the greatest urothelial cell densities observed on nanorough PLGA. In addition, compared to respective conventional polymers, the results provided evidence that nanorough PU and PLGA inhibited calcium oxalate stone formation; submicron pored nanorough PU inhibited calcium oxalate stone formation the most. Thus, results from the present study suggest the importance of nanometer topographical cues for designing better materials for bladder tissue engineering applications.

Urethral reconstruction using oral keratinocyte seeded bladder acellular matrix grafts

PURPOSE

We investigated the feasibility of urethral reconstruction using oral keratinocyte seeded bladder acellular matrix grafts.

MATERIALS AND METHODS

Autologous oral keratinocytes were isolated, expanded and seeded onto bladder acellular matrix grafts to obtain a tissue engineered mucosa. The tissue engineered mucosa was assessed using morphology and scanning electron microscopy. In 24 male rabbits a ventral urethral mucosal defect was created. Urethroplasty was performed with autogenic oral keratinocyte seeded bladder acellular matrix grafts in 12 rabbits in the experimental group or with bladder acellular matrix grafts with no cell seeding in 12 in the control group. Retrograde urethrography was performed 1, 2 and 6 months after grafting. The urethral grafts were analyzed grossly and histologically.

RESULTS

Oral keratinocytes had good biocompatibility with bladder acellular matrix grafts. Rabbits implanted with oral keratinocyte seeded bladder acellular matrix grafts voided without difficulty. Retrograde urethrography revealed no sign of strictures at 1, 2 and 6 months. In the control group the urethra with repaired defects was accompanied by strictures. Histological examination showed that grafts seeded with oral keratinocytes formed a 1-layer structure by 1 month, and at 2 and 6 months the keratinocytes had formed multiple layers. There was an evident margin between graft oral keratinocytes and host epithelium. The oral keratinocytes at basilar layers of the grafts expressed P63, as shown by immunocytochemistry. In the control group histopathological evaluation revealed that no 1-layer or stratified epithelium cells had developed at the repaired defect sites, whereas an inflammatory reaction was found in 2 rabbits.

CONCLUSIONS

Oral keratinocytes had good biocompatibility with bladder acellular matrix grafts. Urethral reconstruction with these grafts was better than with bladder acellular matrix grafts alone.

Curative effect and histocompatibility evaluation of reconstruction of traumatic defect of rabbit urethra using extracellular matrix

OBJECTIVE

To investigate the curative effect and histocompatibility of reconstruction of traumatic urethral defect of rabbit using urethral extracellular matrix (ECM).

METHODS

Urethral ECM was obtained by excision of the urethra in 20 donor rabbits. In experimental group, 20 rabbits were resected a 1.0 cm-1.5 cm segment of the urethra and artificially made a model of traumatic urethral defect, then reconstructed by the urethral extracellular matrix of the same length. The rabbit immunity response was assessed by lymphocyte transformation test and serum TNF-alpha level. The reconstructed urethral segments were stained with hematoxylin-eosin and Van Gieson stain and observed by histological examination postoperatively. The urethrography, urethroscopy and urodynamic examinations were performed.

RESULTS

There was no significant difference in stimulative index of lymphocyte transformation between ECM group and control group. The serum TNF-alpha levels of ECM group slightly rose, but the increase was not significant as compared with control group. On postoperative day 10, epithelial cell had migrated from each side and small vessels were found in the extracellular matrix. In the 3rd week, several layers of urothelium covered the whole surface of the matrix tube. In the 6th week, the disorganized arrangements of smooth muscle fibers were firstly observed by Van Gieson staining. In the 24th week, the smooth muscle cells increased and the matrix tube appeared fairly similar to normal urethral wall components. The urethroscopy and urodynamic evaluation revealed that the surface of reconstructed urethra was smooth and emiction was unobstructed.

CONCLUSION

The urethral extracellular matrix might be an ideal and safe biomaterial for the reconstruction of urethral traumatic defect.

Stem cells and tissue engineering applications of the genitourinary tract

The field of regenerative medicine continues to make substantial advancements in therapeutic strategies addressing urologic diseases. Tissue engineering borrows principles from the fields of cell biology, materials science, transplantation and engineering in an effort to repair or replace damaged tissues. This review is intended to provide a current overview of the use of stem cells and tissue engineering technologies specifically in the treatment of genitourinary diseases. Current themes in the field include the use of adult stem cells seeded onto biocompatible resorbable matrices for implantation as tissue substitutes, which is conducive to host tissue in-growth. Injection therapy of adult stem cells for organ rehabilitation is also making strong headway toward the restoration of organ structure and function. With new data describing the molecular mechanisms for differentiation, work has begun on targeting tissues for regeneration by genetic modification methods. Promising laboratory discoveries portend the emergence of a new class of clinical therapies for regenerative medicine applications in the genitourinary tract.

Laparoscopic and robotic assisted radical cystectomy for bladder cancer: a critical analysis

CONTEXT AND OBJECTIVES

Interest in laparoscopic assisted radical cystectomy (LRC) and robotic assisted radical cystectomy (RRC) is increasing at select centers worldwide. In this update we present the recent worldwide experience and critically evaluate the role of minimally invasive radical surgery for patients with bladder cancer.

EVIDENCE ACQUISITION

English-language literature between 1992 and 2007 was reviewed using the National Library of Medicine database and the following key words: laparoscopic, laparoscopic-assisted, robotic, robotic-assisted, and radical cystectomy. Over 102 papers were identified, 48 of which were selected for this review on the basis of their contribution to advancing the field with regard to three criteria: (1) evolution of concepts, (2) development and refinement of techniques, and (3) intermediate- and long-term clinical outcomes. These were evaluated with respect to current techniques and perioperative, functional, and oncological outcomes. Our initial experience is also reported.

EVIDENCE SYNTHESIS

Minimally invasive techniques can adequately achieve the extirpative aspects of LRC and extended template lymphadenectomy. At most institutions the reconstructive urinary diversion is now typically being performed extracorporeally through a minilaparotomy. Perioperative data indicate that minimally invasive techniques are associated with reduced blood loss, slightly increased operating time, and shorter hospital stay without any significant difference in postoperative complications compared with open surgery. Intermediate-term oncological outcomes appear to be comparable with the open approach. Worldwide experience continues to increase; >700 surgeries have already been performed.

CONCLUSION

LRC or RRC with extracorporeally constructed urinary diversion is a safe and effective operation for appropriate patients with bladder cancer. Perioperative and functional outcomes are comparable with open surgery. More focus on extended lymphadenectomy is necessary to routinely achieve higher node yields. Surrogate and intermediate oncological outcomes are encouraging, and long-term assessment is ongoing.

Tissue Engineering for the Lower Urinary Tract: A Review of a State of the Art Approach

OBJECTIVES

Tissue engineering (TE) has become synonymous with physiological and functional reconstructive approaches in medicine. Although the goals of TE are ambitious and have not yet been attained, significant milestones have been achieved and future possibilities are great. To examine these possibilities with a special emphasis on the lower urinary tract, we provide a review of the development of TE techniques and a high-level overview of related regulatory and legal issues.

METHODS

Current trends in the field of TE, including the use of stem cells, scaffold optimization, and acellular tissue and growth factors, were reviewed and critically assessed through a comprehensive literature review using the PubMed database. Because of the rapid development of new TE approaches, recent abstracts from international urology conventions were included. A review of 2007 European Medicines Agency and Commission for Advanced Therapies legal regulations was also performed.

RESULTS

Although several clinical TE approaches have been developed, most lack objective validation. A variety of TE techniques are currently under development or investigation, but thus far, no one approach is clearly superior on the basis of significant long-term studies. A medical product based on TE and stem cells can be successfully developed only with careful consideration of legal and ethical regulations.

CONCLUSIONS

TE holds the promise for a tremendous impact on reconstructive urology. However, research must be focused and intensified for the full potential clinical benefits to be made widely available. Because the product development is affected by legal regulations, consensus must be achieved.

Bladder Augmentation With Acellular Dermal Biomatrix in a Diseased Animal Model

PURPOSE

The use of bowel for bladder augmentation is associated with many complications. We have reported that acellular dermal biomatrix can be used successfully for directing the regeneration of each key bladder wall element in healthy domestic pigs. Before proposing that this material should be used in the human setting a final set of experiments using this scaffold to replace diseased bladder wall is necessary. We determined if acellular dermal biomatrix can be used to replace diseased bladder wall. We compared our findings to our previous results.

MATERIALS AND METHODS

Six domestic male pigs underwent urethral ligation and suprapubic tube placement. Five female pigs served as controls for bladder dynamics. Machined resistance valves of 5 and 10 cm H(2)O pressure were placed into the lumen of the cystostomy catheter for a mean of 3.3 weeks (range 3 to 4). Obstruction was then relieved and partial cystectomy was performed, followed by augmentation with a 4 x 4 cm segment of acellular dermal biomatrix of the markedly thickened and poorly compliant bladder. Animals were sacrificed 3 months following augmentation. Standard urodynamic studies were performed. Contractility and compliance were measured in freshly isolated regenerated and native bladder tissues. Histological evaluation was performed on hematoxylin and eosin, and Masson's trichrome stained sections.

RESULTS

Bladder compliance was markedly decreased after 3.3 weeks of obstruction. Mean compliance +/- SEM before obstruction was 16.28 +/- 9.21 cm H(2)O. After 3.3 weeks of obstruction average compliance was 4.13 +/- 0.98 cm H(2)O. One pig died 2 weeks following augmentation due to graft separation and sepsis. Gross examination of augmented bladders revealed the complete replacement of acellular dermal biomatrix with bladder tissue. Histological evaluation revealed extensive fibrosis with small islands of poorly organized muscle in contrast to the complete regeneration of mucosa, smooth muscle and serosa seen in augmentations previously performed in healthy animal bladders. Maximum contractile tension of the patch tissue was not different than that in the native tissue from the obstructed hypertrophied bladder but it was only approximately 10% of the tension produced by healthy tissue from nonobstructed augmented bladders. The obstructed bladder patch and native tissue was approximately 14 times stiffer than healthy bladder tissue.

CONCLUSIONS

While augmentation of healthy porcine bladder with acellular dermal biomatrix results in excellent functional bladder tissue regeneration, similar experiments in a porcine model of obstructed bladder disease failed to show favorable results. Therefore, acellular dermal biomatrix cannot be recommended at this time for human bladder dysfunction. Results support the contention that matrices designed for human bladder augmentation should be tested in a disease animal model before recommending them for human bladder dysfunction.