Transplantation of autologous differentiated urothelium in an experimental model of composite cystoplasty

Prolonged ischemia of the ileum and colon after surgical mucosectomy explains contraction and failure of "mucus free" bladder augmentation

INTRODUCTION

Mucus production by the intestinal segment used in bladder augmentation results in long term concerns especially stones and UTI. Bladder augmentation with demucosalized intestinal flap is a potential promising approach for mucus-free bladder augmentation, however the contraction of the flap remains a major concern. Mucosectomy has been shown to result in abrupt and immediate cessation of microcirculation in the ileum. However, assessment of microcirculation shortly after mucosectomy may miss a gradual recovery of micro-circulation over a longer period of time. Previous studies have not assessed the colon response to mucosectomy.

OBJECTIVE

Our aim was to assess the effect of mucosectomy on the microcirculation of the colon and ileum beyond the known warm ischemia time.

STUDY DESIGN

Ileum and colon segments were detubularised and mucosectomy was performed in (n = 8) anesthetised minipigs. Group A: sero-musculo-submucosal flaps were created with removal of the mucosa and preserving the submucosal layer Group B: sero-muscular flaps were created with the removal of submucosal-mucosal layer. The Microvascular Flow Index (MFI), the velocity of the circulating red blood cells (RBCV) was measured using Intravital Dark Field (IDF) side stream videomicroscopy (Cytoscan Braedius, The Netherlands) after mucosectomy, for up to 180 min.

RESULTS

Both the MFI and RBCV showed an abrupt reduction of microcirculation, on both surfaces of the remaining intestinal flap, in the ileum as well as in the colon. Slightly better values were seen in Group A of the colon, but even these values remain far below the preoperative (control) results. Some, tendency of recovery of the microcirculation was noted after 60-90 min, but this remained significantly lower than the preoperative control values at 180 min.

CONCLUSION

Both the ileal and the colonic flap remains in severe ischemia after mucosectomy beyond the warm ischemia time.

DISCUSSION

This study shows that surgical mucosectomy compromises vascular integrity of the intestinal flaps used for bladder augmentation. Partial recovery which occurs within the warm ischemia time is not significant enough to avoid fibrosis therefore flap shrinkage may be inevitable with this technique.

LIMITATION

The gastrointestinal structure of the porcine model is not the same exactly as the human gastrointestinal system. However, although not an exact match it is the closest, readily available animal model to the human gastrointestinal system.

Barrier-Forming Potential of Epithelial Cells from the Exstrophic Bladder

Bladder exstrophy (BEX) is a rare developmental abnormality resulting in an open, exposed bladder plate. Although normal bladder urothelium is a mitotically quiescent barrier epithelium, histologic studies of BEX epithelia report squamous and proliferative changes that can persist beyond surgical closure. The current study examined whether patient-derived BEX epithelial cells in vitro were capable of generating a barrier-forming epithelium under permissive conditions. Epithelial cells isolated from 11 BEX samples, classified histologically as transitional (n = 6) or squamous (n = 5), were propagated in vitro. In conditions conducive to differentiated tight barrier formation by normal human urothelial cell cultures, 8 of 11 BEX lines developed transepithelial electrical resistances of more than 1000 Ω.cm², with 3 squamous lines failing to generate tight barriers. An inverse relationship was found between expression of squamous KRT14 transcript and barrier development. Transcriptional drivers of urothelial differentiation PPARG, GATA3, and FOXA1 showed reduced expression in squamous BEX cultures. These findings implicate developmental interruption of urothelial transcriptional programming in the spectrum of transitional to squamous epithelial phenotypes found in BEX. Assessment of BEX epithelial phenotype may inform management and treatment strategies, for which distinction between reversible versus intractably squamous epithelium could identify patients at risk of medical complications or those who are most appropriate for reconstructive tissue engineering strategies.

Development of a porcine acellular bladder matrix for tissue-engineered bladder reconstruction

PURPOSE

Enterocystoplasty is adopted for patients requiring bladder augmentation, but significant long-term complications highlight need for alternatives. We established a protocol for creating a natural-derived bladder extracellular matrix (BEM) for developing tissue-engineered bladder, and investigated its structural and functional characteristics.

METHODS

Porcine bladders were de-cellularised with a dynamic detergent-enzymatic treatment using peristaltic infusion. Samples and fresh controls were evaluated using histological staining, ultrastructure (electron microscopy), collagen, glycosaminoglycans and DNA quantification and biomechanical testing. Compliance and angiogenic properties (Chicken chorioallantoic membrane [CAM] assay) were evaluated. T test compared stiffness and glycosaminoglycans, collagen and DNA quantity. p value of < 0.05 was regarded as significant.

RESULTS

Histological evaluation demonstrated absence of cells with preservation of tissue matrix architecture (collagen and elastin). DNA was 0.01 μg/mg, significantly reduced compared to fresh tissue 0.13 μg/mg (p < 0.01). BEM had increased tensile strength (0.259 ± 0.022 vs 0.116 ± 0.006, respectively, p < 0.0001) and stiffness (0.00075 ± 0.00016 vs 0.00726 ± 0.00216, p = 0.011). CAM assay showed significantly increased number of convergent allantoic vessels after 6 days compared to day 1 (p < 0.01). Urodynamic studies showed that BEM maintains or increases capacity and compliance.

CONCLUSION

Dynamic detergent-enzymatic treatment produces a BEM which retains structural characteristics, increases strength and stiffness and is more compliant than native tissue. Furthermore, BEM shows angiogenic potential. These data suggest the use of BEM for development of tissue-engineered bladder for patients requiring bladder augmentation.

Surface Shave: Revealing the Apical-Restricted Uroglycome

This study aimed to investigate the highly differentiated urothelial apical surface glycome. The functions of the mammalian urothelium, lining the majority of the urinary tract and providing a barrier against toxins in urine, are dependent on the correct differentiation of urothelial cells, relying on protein expression, modification, and complex assembly to regulate the formation of multiple differentiated cell layers. Protein glycosylation, a poorly studied aspect of urothelial differentiation, contributes to the apical glycome and is implicated in the development of urothelial diseases. To enable surface glycome characterization, we developed a method to collect tissue apical surface N- and O-glycans. A simple, novel device using basic laboratory supplies was developed for enzymatic shaving of the luminal bladder urothelial surface, with subsequent release and mass spectrometric analysis of apical surface O- and N-glycans, the first normal mammalian urothelial N-glycome to be defined. Trypsinization of superficial glycoproteins was tracked using immunolabeling of the apically expressed uroplakin 3a protein to optimize enzymatic release, without compromising the integrity of the superficial urothelial layer. The approach developed for releasing apical tissue surface glycans allowed for comparison with the N-glycome of the total porcine bladder urothelial cells and thus identification of apical surface glycans as candidates implicated in the urothelial barrier function. Data are available in MassIve: MSV000087851.

Bladder augmentation from an insider's perspective: a review of the literature on microcirculatory studies

Augmentation cystoplasty is an exemplary multiorgan intervention in urology which is particularly associated with microvascular damage. Our aim was to review the available intravital imaging techniques and data obtained from clinical and experimental microcirculatory studies involving the most important donor organs applied in bladder augmentation. Although numerous direct or indirect methods are available to assess the condition of microvessels the implementation of microcirculatory diagnostic methods in humans is still challenging and the assessment of organ microcirculation in the operating theatre has limitations. Nevertheless, preclinical studies generally report good internal validity and although prospective human protocols with reduced variability are needed, a possible positive impact of microcirculatory diagnostics on the clinical outcomes of urologic surgery can be anticipated.

Electrospinning: Application and Prospects for Urologic Tissue Engineering

Functional disorders and injuries of urinary bladder, urethra, and ureter may necessitate the application of urologic reconstructive surgeries to recover normal urine passage, prevent progressive damages of these organs and upstream structures, and improve the quality of life of patients. Reconstructive surgeries are generally very invasive procedures that utilize autologous tissues. In addition to imperfect functional outcomes, these procedures are associated with significant complications owing to long-term contact of urine with unspecific tissues, donor site morbidity, and lack of sufficient tissue for vast reconstructions. Thanks to the extensive advancements in tissue engineering strategies, reconstruction of the diseased urologic organs through tissue engineering have provided promising vistas during the last two decades. Several biomaterials and fabrication methods have been utilized for reconstruction of the urinary tract in animal models and human subjects; however, limited success has been reported, which inspires the application of new methods and biomaterials. Electrospinning is the primary method for the production of nanofibers from a broad array of natural and synthetic biomaterials. The biomimetic structure of electrospun scaffolds provides an ECM-like matrix that can modulate cells' function. In addition, electrospinning is a versatile technique for the incorporation of drugs, biomolecules, and living cells into the constructed scaffolds. This method can also be integrated with other fabrication procedures to achieve hybrid smart constructs with improved performance. Herein, we reviewed the application and outcomes of electrospun scaffolds in tissue engineering of bladder, urethra, and ureter. First, we presented the current status of tissue engineering in each organ, then reviewed electrospun scaffolds from the simplest to the most intricate designs, and summarized the outcomes of preclinical (animal) studies in this area.

Mucosectomy disrupting the enteric nervous system causes contraction and shrinkage of gastrointestinal flaps: potential implications for augmentation cystoplasty

INTRODUCTION

Augmenting the bladder with a seromuscular gastrointestinal flap is a promising alternative approach aiming for a mucus-free bladder augmentation; however, the contraction (shrinkage) of the flaps remains a major concern. Enteric nervous system (ENS) abnormalities cause a failure of relaxation of the intestinal muscle layers in motility disorders such as Hirschsprung's disease and intestinal neuronal dysplasia. In mammals, the submucosal enteric nervous plexus contains nitrergic inhibitory motor neurons responsible for muscle relaxation. The authors hypothesize that mucosectomy disconnects the submucosal nervous plexus from the myenteric plexus resulting in flap shrinkage.

STUDY DESIGN

After ethical approval, mucosectomy was performed on vascularized flaps from the ileum, colon, and stomach in five anesthetized pigs. In Group (I), only the mucosa was scraped off with forceps, creating a sero-musculo-submucosal flap, while in Group (II), the mucosa and submucosa were peeled off as one layer, leaving a seromuscular flap. Isolated and detubularized segments served as control. The width of each flap was measured before and after the mucosectomy. The ENS was assessed by neurofilament immunohistochemistry in conventional sections and by acetylcholinesterase and NADPH-diaphorase enzyme histochemistry in whole-mount preparations.

RESULTS

The stomach contracted to a lesser extent of its original width, 92.82 ± 7.86% in Group (I) and 82.24 ± 6.96% in Group (II). The ileum contracted to 81.68 ± 4.25% in Group (I) and to 72.675 ± 5.36% in Group (II). The shrinkage was most noticeable in the colon: 83.89 ± 15.73% in Group (I) and to 57.13 ± 11.51% in Group (II). One-way equal variance test showed significant difference (P < 0,05) between Group (I) and (II), comparing stomach with ileum and ileum with colon. The histochemistry revealed that the submucosal nervous plexus containing nitrergic inhibitory neurons was disconnected from the myenteric plexus in Group (II) of all specimens.

CONCLUSION

Mucosectomy resulted in significant immediate shrinkage of the flaps. This was more expressed when also the submucosa was peeled off, thus fully disrupting the ENS. The shrinkage affected the stomach the least and the colon the greatest. This phenomenon should be taken into consideration when planning mucus-free bladder augmentation.

Hypoxic changes to the urothelium as a bystander of end-stage bladder disease

INTRODUCTION

Urothelial cells harvested from benign diseased bladders have a compromised capacity to propagate or differentiate in vitro, potentially limiting their application in autologous tissue engineering approaches. The causative pathways behind this altered phenotype are unknown. The hypothesis is that hypoxic damage to the urothelium occurs as a bystander to chronic or recurrent episodes of infection and inflammation.

OBJECTIVE

The aim of this study was to assess immunohistochemically detected nuclear hypoxia-inducible factor 1 alpha (HIF-1α) and vascular endothelial growth factor in the urothelium when exposed to hypoxia.

STUDY DESIGN

Human bladder sections from a total of 29 adult and paediatric patients, representing a variety of different pathologies including neuropathy (n = 15), were analysed. Tissues from adults with bladder outlet obstruction secondary to prostatic disease (n = 1), urothelial carcinoma (n = 1) and tonsil (n = 1) were used as positive tissue controls for immunohistochemistry. Hypoxia-inducible factor 1 alpha-labelled sections were scanned using a Zeiss AxioScan Z1 slide scanner. Analysis of urothelial nuclear HIF-1α labelling was performed using HistoQuest image analysis software (TissueGnostics). Comparison of nuclear HIF-1α labelling between neuropathic and non-neuropathic sections was performed using one-way analysis of variance with the post hoc Tukey honestly significant difference (HSD) test. Patient urodynamic studies performed before tissue sample harvest were evaluated and correlated to the HIF-1α intensity using Spearman's rank correlation.

RESULTS

Hypoxia-inducible factor 1 alpha appeared more intense in the urothelial compartment from neuropathic bladder samples (n = 15) than in the control tissues, including non-obstructed samples (n = 9). Image analysis supported this; median nuclear HIF-1α labelling was 29.98 ± 3.10 (standard deviation [SD]) (n = 9) in controls and 74.29 ± 7.55 (SD) in neuropathic samples (n = 15). A statistically significant difference between the control and neuropathic tissue groups was shown (P < 0.05). Of the 15 neuropathic samples, 11 had traceable urodynamic studies. Both initial and maximum detrusor pressures indicated a positive relationship when plotted against HIF-1α labelling. Spearman's rank correlation, with no missing events, confirmed significant correlations between both initial or maximum detrusor pressure and nuclear HIF-1α labelling intensity (median score); P ≤ 0.046 and P ≤ 0.05, respectively. The null hypothesis was accordingly rejected.

CONCLUSIONS

This study indicates that urothelial nuclear HIF-1α may be a biomarker of hypoxia and a common feature in end-stage bladder disease associated with high-pressure systems.

Differential transcription factor expression by human epithelial cells of buccal and urothelial derivation

Identification of transcription factors expressed by differentiated cells is informative not only of tissue-specific pathways, but to help identify master regulators for cellular reprogramming. If applied, such an approach could generate healthy autologous tissue-specific cells for clinical use where cells from the homologous tissue are unavailable due to disease. Normal human epithelial cells of buccal and urothelial derivation maintained in identical culture conditions that lacked significant instructive or permissive signaling cues were found to display inherent similarities and differences of phenotype. Investigation of transcription factors implicated in driving urothelial-type differentiation revealed buccal epithelial cells to have minimal or absent expression of PPARG, GATA3 and FOXA1 genes. Retroviral overexpression of protein coding sequences for GATA3 or PPARy1 in buccal epithelial cells resulted in nuclear immunolocalisation of the respective proteins, with both transductions also inducing expression of the urothelial differentiation-associated claudin 3 tight junction protein. PPARG1 overexpression alone entrained expression of nuclear FOXA1 and GATA3 proteins, providing objective evidence of its upstream positioning in a transcription factor network and identifying it as a candidate factor for urothelial-type transdifferentiation or reprogramming.

Bladder augmentation in children: current problems and experimental strategies for reconstruction

Bladder augmentation is a demanding surgical procedure and exclusively offered for selected children and has only a small spectrum of indications. Paediatric bladder voiding dysfunction occurs either on a basis of neurological dysfunction caused by congenital neural tube defects or on a basis of rare congenital anatomic malformations. Neurogenic bladder dysfunction often responds well to a combination of specific drugs and/or intermittent self-catheterization. However, selected patients with spinal dysraphism and children with congenital malformations like bladder exstrophy and resulting small bladder capacity might require bladder augmentation. Ileocystoplasty is the preferred method of bladder augmentation to date. Because of the substantial long-and short-term morbidity of augmentation cystoplasty, recent studies have tried to incorporate new techniques and technologies, such as the use of biomaterials to overcome or reduce the adverse effects. In this regard, homografts and allografts have been implemented in bladder augmentation with varying results, but recent studies have shown promising data in terms of proliferation of urothelium and muscle cells by using biological silk grafts.

Mucosectomy impairs ileal microcirculation and results in flap contraction after experimental ileocystoplasty

INTRODUCTION

Bladder augmentation with demucosalized ileal flap is a promising alternative approach for mucus free bladder augmentation; however, the contraction of the flap is still a major concern. It has been hypothesized that mucosectomy causes ischemic damage, but no direct histological evidence has been found and attention is now focused on the urothelium cover to prevent the exposure of the denuded surface to urine or the use of balloons to keep the flaps distended.

OBJECTIVE

Our aim was to study the effect of mucosectomy on the microcirculation of ileal flaps during reverse clam ileocystoplasty using direct intraoperative imaging of the ileum. Since the omentum is successfully used to revascularize ischemic tissue, we also examined whether omentopexy can prevent contraction.

STUDY DESIGN

Clam ileocystoplasty was performed in anesthetized minipigs with seromuscular (n = 3), seromusculo-submucosal (n = 3) reverse demucosalized ileal flaps. The velocity of the circulating red blood cells (RBCV) and the perfusion rate (PR) was measured with intravital videomicroscopy (Cytoscan A/R, Cytometrics, Philadelphia, PA, USA) before and after mucosectomy and the denuded surface of the ileum was covered with omentum after the reverse augmentation was complete (Figure). Animals were sacrificed after 8 weeks and the ileal flap dimensions were measured.

RESULTS

Significant reduction in RBCV and PR was detected after mucosectomy in both groups; however, no sign of acute flap necrosis or bladder perforation was seen. The omentum was found firmly attached to the ileal flaps, but contraction of the flaps was significant in both groups.

CONCLUSION

The disturbance in the microcirculation observed after mucosectomy may be responsible for flap contraction in ileocystoplasty with demucosalized ileum. Omentopexy did not help to prevent contraction.

DISCUSSION

Contraction of demucosalized intestinal flaps used for bladder augmentation has been frequently reported. This study provides direct evidence the first time for severely compromised microcirculation of the ileal flaps after mucosectomy. Limitation of the study is the relative low number of animals sacrificed.

Scaffolds for whole organ tissue engineering: Construction and in vitro evaluation of a seamless, spherical and hollow collagen bladder construct with appendices

The field of regenerative medicine has developed promising techniques to improve current neobladder strategies used for radical cystectomies or congenital anomalies. Scaffolds made from molecularly defined biomaterials are instrumental in the regeneration of tissues, but are generally confined to small flat patches and do not comprise the whole organ. We have developed a simple, one-step casting method to produce a seamless large hollow collagen-based scaffold, mimicking the shape of the whole bladder, and with integrated anastomotic sites for ureters and urethra. The hollow bladder scaffold is highly standardized, with uniform wall thickness and a unidirectional pore structure to facilitate cell infiltration in vivo. Human and porcine bladder urothelial and smooth muscle cells were able to attach to the scaffold and maintained their phenotype in vitro. The closed luminal side and the porous outside of the scaffold facilitated the formation of an urothelial lining and infiltration of smooth muscle cells, respectively. The cells aligned according to the provided scaffold template. The technology used is highly adjustable (shape, size, materials) and may be used as a starting point for research to an off-the-shelf medical device suitable for neobladders.

STATEMENT OF SIGNIFICANCE

In this study, we describe the development of a simple, one-step casting method to produce a seamless large hollow collagen-based scaffold mimicking the shape of the whole bladder with integrated anastomotic sites for ureters and urethra. The hollow bladder scaffold is highly standardized with uniform wall thickness and a unidirectional pore structure to facilitate cell infiltration in vivo. The closed luminal surface and the porous exterior of the scaffold facilitated the formation of a urothelial lining and infiltration of smooth muscle cells, respectively. The applied technology is highly adjustable (shape, size, materials) and can be the starting point for research to an off-the-shelf medical device suitable for neobladders.

Epithelial-Mesenchymal Interactions in Urinary Bladder and Small Intestine and How to Apply Them in Tissue Engineering

Reciprocal interactions between the epithelium and mesenchyme are essential for the establishment of proper tissue morphology during organogenesis and tissue regeneration as well as for the maintenance of cell differentiation. With this review, we highlight the importance of epithelial-mesenchymal cross talk in healthy tissue and further discuss its significance in engineering functional tissues in vitro. We focus on the urinary bladder and small intestine, organs that are often compromised by disease and are as such in need of research that would advance effective treatment or tissue replacement. To date, the understanding of epithelial-mesenchymal reciprocal interactions has enabled the development of in vitro biomimetic tissue equivalents that have provided many possibilities in treating defective, damaged, or even cancerous tissues. Although research of the past several years has advanced the field of bladder and small intestine tissue engineering, one must be aware of its current limitations in successfully and above all safely introducing tissue-engineered constructs into clinical practice. Special attention is in particular needed when treating cancerous tissues, as initially successful tumor excision and tissue reconstruction may later on result in cancer recurrence due to oncogenic signals originating from an altered stroma. Recent rather poor outcomes in pioneering clinical trials of bladder reconstructions should serve as a reminder that recreating a functional organ to replace a dysfunctional one is an objective far more difficult to reach than initially foreseen. When considering effective tissue engineering approaches for diseased tissues in humans, it is imperative to introduce animal models with dysfunctional or, even more importantly, cancerous organs, which would greatly contribute to predicting possible complications and, hence, reducing risks when translating to the clinic.

Supportive features of a new hybrid scaffold for urothelium engineering

INTRODUCTION

Different clinical conditions can compromise the urinary bladder function and structure. Routine regenerative practices in urology for bladder augmentation have been associated with diverse side effects. The internal lining of the bladder, the urothelium, plays an integral role in normal bladder function. Tissue engineering has provided novel therapeutic strategies through scaffolding and cell transplantation. Nano-scale surface features of scaffolds are valuable parameters for enhancement of cell behavior and function.

MATERIAL AND METHODS

We fabricated a new hybrid scaffold of poly ɛ-caprolactone (PCL) and poly-L-lactide acid (PLLA) using an electrospinning system to exploit each polymer's advantages at nano-scale in the same scaffold. Dog urothelial cells were isolated, characterized by immunocytochemistry, and expanded for loading on the scaffold. Cell viability and proliferation on the scaffold surface were assessed by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Furthermore, cytoarchitecture, distribution and detailed morphology of cells, and expression of cell specific markers were examined using hematoxylin and eosin (H + E) staining, scanning electron microscopy (SEM), and immunohistochemistry, respectively.

RESULTS

According to MTT results, the scaffold did not exert any cytotoxic effect, and also supported cell proliferation and viability for 14 days of culture, which led to a significant increase in the number of cells. Scanning electron microscopy images revealed evenly distributed and normal appearing colonies of urothelial cells. A well-defined layer of cells was observed using H + E staining, which preserved their markers (pan-cytokeratin and uroplakin III) while growing on the scaffold.

CONCLUSIONS

Our findings confirmed favorable properties of PCL/PLLA regarding biocompatibility and applicability for upcoming new methods of bladder augmentation and engineering.

Urethral reconstruction using bone marrow mesenchymal stem cell- and smooth muscle cell-seeded bladder acellular matrix

BACKGROUND

Congenital or acquired abnormalities may lead to a urethral defect that often requires surgical reconstruction. The traditional methods often lead to complications, including urethrocutaneous fistulae and strictures. In this study, we proposed to construct a tissue-engineered sheet graft (TESG) using a bone marrow mesenchymal stem cell (BMSC)- and smooth muscle cell (SMC)-seeded bladder acellular matrix (BAM) for urethral reconstruction.

METHODS

Rabbit BMSCs and SMCs were isolated, expanded, and identified in vitro before seeding into BAM as the experimental group, whereas BAM-only was the control group. The graft was used to construct TESG for implantation into the rabbit omentum for 2 weeks before urethral reconstruction. We divided 24 male rabbits into four experimental groups six each, and six other were the control group. Histological analysis was performed at 2 weeks, 4 weeks, 8 weeks, and 16 weeks postoperatively. Retrograde urethrography was performed at 16 weeks postoperatively.

RESULTS

All experimental rabbits survived to they were humanly killed. At 8 weeks, there was no difference between the graft and the normal urethra with no severe shrinkage. At 8 and 16 weeks after TESG grafting in vivo, multilayer urothelium covered the graft, neovascularization was visible within the center of TESG, and organized smooth muscle bundles were present. Retrograde urethrography failed to demonstrate diverticula formation or urethral stricture. Three control rabbits died within 4 weeks postoperatively. Autopsy showed their urethras to be almost completely blocked whereas another three hosts displays urethral strictures.

CONCLUSION

A TESG was constructed using a BMSC- and SMC-seeded BAM for urethral reconstruction.

The human tissue-biomaterial interface: a role for PPARγ-dependent glucocorticoid receptor activation in regulating the CD163+ M2 macrophage phenotype

In vivo studies of implanted acellular biological scaffolds in experimental animals have shown constructive remodeling mediated by anti-inflammatory macrophages. Little is known about the human macrophage response to such biomaterials, or the nature of the signaling mechanisms that govern the macrophage phenotype in this environment. The cellular events at the interface of a tissue and implanted decellularized biomaterial were examined by establishing a novel ex vivo tissue culture model in which surgically excised human urinary tract tissue was combined with porcine acellular bladder matrix (PABM). Evaluation of the tissue-biomaterial interface showed a time-dependent infiltration of the biomaterial by CD68(+) CD80(-) macrophages. The migration of CD68(+) cells from the tissue to the interface was accompanied by maturation to a CD163(hi) phenotype, suggesting that factor(s) associated with the biomaterial or the wound edge was/were responsible for the active recruitment and polarization of local macrophages. Glucocorticoid receptor (GR) and peroxisome proliferator activated receptor gamma (PPARγ) signaling was investigated as candidate pathways for integrating inflammatory responses; both showed intense nuclear labeling in interface macrophages. GR and PPARγ activation polarized peripheral blood-derived macrophages from a default M1 (CD80(+)) toward an M2 (CD163(+)) phenotype, but PPARγ signaling predominated, as its antagonism blocked any GR-mediated effect. Seeding on PABM was effective at polarizing peripheral blood-derived macrophages from a default CD80(+) phenotype on glass to a CD80(-) phenotype, with intense nuclear localization of PPARγ. These results endorse in vivo observations that the infiltration of decellularized biological scaffolds, exemplified here by PABM, is pioneered by macrophages. Thus, it appears that natural factors present in PABM are involved in the active recruitment and polarization of macrophages to a CD163(+) phenotype, with activation of PPARγ identified as the candidate pathway. The harnessing of these natural matrix-associated factors may be useful in enhancing the integration of synthetic and other natural biomaterials by polarizing macrophage activation toward an M2 regulatory phenotype.

Biomimetic urothelial tissue models for the in vitro evaluation of barrier physiology and bladder drug efficacy

The bladder is an important tissue in which to evaluate xenobiotic drug interactions and toxicities due to the concentration of parent drug and hepatic/enteric-derived metabolites in the urine as a result of renal excretion. Breaching of the barrier provided by the bladder epithelial lining (the urothelium) can expose the underlying tissues to urine and cause harmful effects (e.g., cystitis or cancer). Human urothelium is most commonly represented in vitro as immortalized or established cancer-derived cell lines, but the compromised ability of such cells to undergo differentiation and barrier formation means that nonimmortalized, normal human urothelial (NHU) cells provide a more relevant cell culture system. The impressive capacity for urothelial self-renewal in vivo can be harnessed in vitro to generate experimentally-useful quantities of NHU cells, which can subsequently be differentiated to form a functional or "biomimetic" urothelium. When seeded onto permeable membranes, these barrier-forming human urothelial tissue models enable the modeling of serum and luminal (intravesical) exposure to drugs and metabolites, thus supporting efficacy/toxicity assessments. Biomimetic human urothelial constructs provide a potential step along the preclinical trail and may support the extrapolation from rodent in vivo data to determine human relevance. Early evidence is beginning to demonstrate that human urothelium in vitro can provide information that supersedes conventional rodent studies, but further validation is needed to support widespread adoption.

Use of donor bladder tissues for in vitro research

OBJECTIVES

To evaluate deceased non-heart beating (DNHB) donors and deceased heart beating (DHB) brain-stem dead donors, as sources of viable urological tissue for use in biomedical research. To identify sources of viable human bladder tissue as an essential resource for cell biological research aimed at understanding human diseases of the bladder and for developing new tissue engineering and regenerative medicine strategies for bladder reconstruction. Typically, normal human urinary tract tissue is obtained from adult or paediatric surgical patients with benign urological conditions, but few surgical procedures yield useful quantities of healthy bladder tissue for research.

PATIENTS AND METHODS

Research ethics committee approval was obtained for collection of donor bladder tissue. Consent for DHB donors was undertaken by the Donor Transplant Coordinators. Tissue Donor Coordinators were responsible for consent for DNHB donors and the retrieval of bladders was coordinated through the National Blood Service Tissue Banking Service. All retrievals were performed by practicing urologists and care was taken to maintain sterility and to minimise bacterial contamination. Two bladders were retrieved from DNHB donors and four were retrieved from DHB donors.

RESULTS

By histology, DNHB donor bladder tissue exhibited marked urothelial tissue damage and necrosis, with major loss or absence of urothelium. No cell cultures could be established from these specimens, as the urothelial cells were not viable in primary culture. Bladder urothelium from DHB donors was intact, but showed some damage, including loss of superficial cells and variable separation from the basement membrane. All four DHB bladder specimens yielded viable urothelial cells that attached in primary culture, but cell growth was slow to establish and cultures showed a limited capacity to form a functional barrier epithelium and a propensity to senesce early.

CONCLUSIONS

We have shown that normal human bladder urothelial cell cultures can be established and serially propagated from DHB donor bladders. However, our study suggests that rapid post-mortem changes to the bladder affect the quality and viability of the urothelium, rendering tissue from DNHB donors an inadequate source for urothelial cell culture. Our experience is that whereas patients are willing to donate surgical tissue for research, there is a barrier to obtaining consent from next of kin for retrieved tissues to be used for research purposes.

Plasticity of in vitro-generated urothelial cells for functional tissue formation

Tissue-engineering and regenerative medicine strategies for the bladder and urinary tract are dependent on the ability to generate adequate numbers of differentiation-competent uro-epithelial cells. In situ, urothelium is a mitotically quiescent, but highly regenerative epithelium. Although evidence supports a resident, basally located urothelial progenitor population, no specific stem cell has been identified. Our aim was to isolate basal and suprabasal urothelial subpopulations and characterize their regenerative and differentiation potentials in vitro. We showed that the low-affinity nerve growth factor receptor (NGFR) is a cell surface-expressed marker that is restricted to basal cells in normal human and porcine urothelia in situ. We used NGFR immunoseparation and differential adherence to collagen to isolate subpopulations of urothelial cells for culture. Isolated basal-derived porcine NGFR⁺ urothelial cells initially showed a higher proliferative and clonogenic phenotype than their suprabasal NGFR⁻ counterparts in vitro. However, after a short period of adaptation to culture, both NGFR⁺ and NGFR⁻ subpopulations became indistinguishable and displayed similar long-term growth and differentiation potentials. Both populations generated hierarchically organized, differentiated tissue equivalents similar to native urothelium, including a fully reconstituted NGFR⁺ basal cell layer by the NGFR⁻ suprabasal-derived population. Similarly, slow collagen-adherent human urothelial cells initially displayed a longer lag phase than rapid-adherent cultures, but after adaptation, both populations showed similar long-term proliferation, exponential growth rates, and capacity to form a functional barrier urothelium. Our results support a model where urothelial cell phenotype is plastic and determined by the niche or local environment. This has direct implications for tissue-engineering strategies requiring urothelial cell expansion and provides a new perspective toward understanding urothelial regeneration and differentiated tissue hierarchy.

Alternatives to conventional enterocystoplasty in children: a critical review of urodynamic outcomes

Alternatives to conventional enterocystoplasty have been developed in order to avoid the most common complications derived from contact of the urine with intestinal mucosa. In this article critically we review the literature on the topics: ureterocystoplasty, detrusorectomy, detrusorotomy, seromuscular gastroenterocystoplasty, use of off the shelf biomaterials, and bladder augmentation by bioengineering. Recognizing the difficulty of deciding when a child with a history of posterior urethral valves requires and augmentation and that the development of a large megaureter in cases of neurogenic dysfunction represents a failure of initial treatment, we conclude that ureterocystoplasty can be useful in selected cases when a large dilated ureter is available. Seromuscular colocystoplasty lined with urothelium (SCLU) has been urodynamically effective in several series when the outlet resistance is high and no additional intravesical procedures are necessary. Seromuscular gastrocystoplasty lined with urothelium seems to offer no distinct advantages and involves a much more involved operation. The use of seromuscular segments without urothelial preservation, with or without the use of an intravesical balloon has been reported as successful in two centers but strict urodynamic evidence of its effectiveness is lacking. The published evidence argues strongly against the use of detrusorectomy or detrusorotomy alone because of the lack of significant urodynamic benefits. Two recent reports discourage the use of small intestinal submucosa patches because of a high failure rate. Finally, research into the development of a bioengineered bladder constructed with cell harvested from the same patient continues but is fraught with technical and conceptual problems. In conclusion of the methods reviewed, only ureterocystoplasty and SCLU have been proven urodynamically effective and reproducible.

Regenerative medicine as a new therapeutic strategy for lower urinary tract dysfunction

The use of regenerative medicine for the treatment of organic and functional disorders intractable to conventional treatment has increased worldwide. This innovative medical field might particularly hold promise for the treatment of life-threatening diseases or healing of irreplaceable organs, such as the heart, liver and brain. Dysfunction of the urogenital tract and associated organs other than the kidney might not have immediate life-threatening implications; furthermore, the effectiveness of alternative therapy, such as enterocystoplasty for bladder cancer, has been shown. Therefore, most physicians or scientists do not give much importance to these disorders. However, urological disease has increased in developed societies in recent years. Furthermore, medical costs have also escalated. Disorders of the lower urinary tract, such as urinary disturbance or incontinence, can lead to other complications, impairing quality of life and ultimately increasing short- and long-term medical expenses. Regenerative medicine might hold potential solutions to these problems. Recent advances in urogenital regenerative medicine are reviewed in the present article, with particular reference to lower urinary tract reconstruction. The potential of regenerative medicine for the treatment of intractable lower urinary tract dysfunction compared with conventional treatment is also discussed.

Cell-seeded extracellular matrices for bladder reconstruction: an ex vivo comparative study of their biomechanical properties

PURPOSE

Autogenous ileal tissue remains the gold-standard biomaterial for bladder replacement purposes; however, cell-seeded extracellular matrix (ECM) scaffolds have shown promise. Although the biological advantages of cell-seeded ECMs in urological settings are well documented, there is a paucity of data available on their biomechanical properties. In this study, the biomechanical properties of cell-seeded ECMs are compared with autogenous ileal tissue.

METHODS

Human urothelial cells (UCs) and smooth muscle cells (SMCs) were obtained by bladder biopsy and cultured onto porcine urinary bladder matrix (UBM) scaffolds under dynamic and static growth conditions for 14 days. The biomechanical properties of cell-seeded UBM (n = 12), and porcine ileum (n = 12) were determined with uni-axial tensile testing protocols and compared with stress-strain curves. In addition, their biomechanical properties were compared with porcine bladder tissue (n = 12) and unseeded UBM (n = 12).

RESULTS

There were significant differences in the biomechanical properties of each biomaterial assessed. Strain to failure occurred at 92 ± 24% for dynamically cultured cell-seeded UBM compared to 42.2 ± 5.20% for ileal tissue (p<0.01). Values for linear stiffness at 30% strain were significantly lower in dynamically cultured cell-seeded UBM compared to ileal tissue (0.36 ± 0.14 MPa versus 0.67 ± 0.32 MPa respectively, p<0.01). Bladder tissue remained the most distensible biomaterial throughout, with linear stiffness measuring 0.066 ± 0.034 MPa at 30% strain.

CONCLUSIONS

Dynamically cultured cell-seeded ECMs are biomechanically superior to ileal tissue for bladder replacement purposes. Additional comparative in vivo studies will be necessary before their role as a reliable alternative is clearly established.

Seromuscular grafts for bladder reconstruction: extra-luminal demucosalisation of the bowel

Objective

To develop a robust sterile, fully demucosalized and vascularized seromuscular patch for use as an adjunct to novel bioengineering techniques aimed at augmenting, reconstructing, or replacing the bladder because of endstage disease. To eliminate deep colonic epithelial crypts to prevent the possibility of colonocyte regrowth. To maintain sterility by excluding the possibility of contamination from the bowel contents.

Methods

Pilot studies were performed on euthanized pigs to optimize the technique, with tissue samples examined by immunohistochemistry. In vivo, vascularized seromuscular colonic flaps were created from the bowel exterior in 7 large white hybrid pigs. The dissection was facilitated by placing an inflated Foley catheter within the colonic lumen. The seromuscular ends were approximated with 5/0 Vicryl sutures and excess mucosa intussuscepted within the lumen. Demucosalized flaps were used to augment the bladder by composite cystoplasty and were examined immunohistochemically at 3 months.

Results

Pilot studies showed that the technique was successful in creating seromuscular segments with no epithelial remnants. When applied surgically, the seromuscular flaps survived and showed no evidence of colonocyte regrowth at 3 months.

Conclusion

Extraluminal dissection creates robust seromuscular flaps and prevents both regrowth by colonic epithelial cells and contamination of the tissue by exposure to the bowel contents. This technique should find application in a range of bladder reconstruction techniques, including composite cystoplasty and autoaugmentation.

An examination of regenerative medicine-based strategies for the urinary bladder

Patients that are afflicted with dysfunctional urinary bladders due to developmental defect, trauma or malignant transformation have limited treatment options that would allow for complete recapitulation of the urinary bladder. Hence, novel tissue engineering techniques that are successful in regenerating functional urinary bladder tissue for replacement therapy would be invaluable. Current tissue engineering techniques are hampered by several problems including choice of appropriate cell type, inadequate development of new blood vessels to the regenerated tissue, tissue innervation and primitive bioscaffold design. This article describes the recent advances in stem cell biology and the material sciences to address these problems, and attempts to improve upon current tissue engineering techniques to make successful regeneration of urinary bladder tissue a reality.

Re-epithelialization of demucosalized stomach patch with tissue-engineered urothelial mucosa combined with Botox A in bladder augmentation

Re-epithelialization demucosa stomach patch is important to prevent the patch being exposed to urine that might cause patch shrinkage and fibrosis formation due to urine-derived chemical irritation. Additionally, Botox A acts by blocking the transmission of nerve impulses to smooth muscles and so paralysing the muscles, which is commonly used to relax muscle for treatment of oesophageal achalasia due to overactive smooth muscle and sphincters of gastrointestinal tract. We fabricated in vitro tissue engineered urothelial mucosa with multi-layers of urothelium and smooth muscle layers seeded on SIS scaffold and then used this cell-scaffold construct to cover nuke gastro patch combining with Botox A for gastrocystoplasty in a canine model.

OBJECTIVE

To evaluate the demucosalized stomach patch covered with tissue-engineered urothelium for gastrocystoplasty and to determine whether or not injections of Botox A into the re-epithelialized stomach patch can protect the graft from contraction in a canine bladder reconstruction model.

MATERIALS AND METHODS

Gastrocystoplasty was performed in 10 adult beagles after hemi-cystectomy using five types of stomach patch (n = 2 per group): entire stomach patches (group I); demucosalized patches (group II); demucosalized patches covered with cell-free small intestinal submucosa (SIS) (group III); demucosalized patches with urothelial and smooth muscle cell-seeded SIS (group IV); and demucosalized patches with the cell-seeded SIS combined with injections of Botox A (group V). The bladder volume/pressure and the graft sizes were measured before surgery and again 10 weeks after bladder augmentation. The graft tissues were examined both histologically and using immunohistochemistry.

RESULTS

All dogs survived and their gastric grafts were all vital with a good blood supply. Gastric metaplasia of urothelium appeared on the top of stomach mucosa patches in two animals in group I. There was calcification formation at the centre of the graft in one animal in group II. As compared with urothelium that was partially covered over with stomach patches in groups II and III, stratified urothelium completely covered the demucosalized gastric patches in groups IV and V. There was less shrinkage of the stomach grafts in groups I and V, which shrank to half of their original size, than of the stomach grafts in groups II, III, and IV, which shrank significantly to one-quarter of their original sizes.

CONCLUSIONS

Botox A injections appear to protect the graft contraction in the re-epithelialized stomach flaps. The gastrocystoplasty using demucosalized patches covered with tissue-engineered urothelial mucosa combined with an injection of Botox A could have clinical potential for use in bladder reconstruction.

The future of regenerative medicine: urinary system

Regeneration of tissues and organs is now within the technological reach of modern medicine. With such advancements, substantial improvements to existing standards-of-care are very real possibilities. This review will focus on regenerative medicine approaches to treating specific maladies of the bladder and kidney, including the biological basis of regeneration and the history of regenerative medicine in the urinary system. Current clinical management approaches will be presented within the context of future directions including cell-based regenerative therapies.

The past, present and future of augmentation cystoplasty

What's known on the subject? And what does the study add? There is a wealth of evidence on the development, indications, outcomes and complications of augmentation cystoplasty (AC). Over the last decade, new evidence has been emerging to influence our clinical practice and application of this technique. AC is indicated as part of the treatment pathway for both neurogenic and idiopathic detrusor overactivity, usually where other interventions have failed or are inappropriate. The most commonly used technique remains augmentation with a detubularised patch of ileum (ileocystoplasty). Controversy persists over the role of routine surveillance following ileocystoplasty for the detection of subsequent bladder carcinoma; however the indication for surveillance after gastrocystoplasty is clearer due to a rising incidence of malignancy in this group. Despite a reduction in the overall numbers of AC operations being performed, it clearly still has a role to play, which we re-examine with contemporary studies from the last decade.

Tissue engineering potential of urothelial cells from diseased bladders

PURPOSE

We examined the suitability of urothelium from patients with abnormal bladders for use in surgical reconstruction using a tissue engineering approach that would require autologous urothelium to be expanded by propagation in cell culture.

MATERIALS AND METHODS

Resection specimens from 8 children (median age 9.8 years) with abnormal bladders (neuropathic in 4, posterior urethral valves in 2, epispadias in 1, nonneurogenic in 1) were collected with informed parental consent during planned urological procedures. Six patients had recurrent urinary tract infections and 7 underwent frequent intermittent catheterization. A representative sample was immunohistologically processed to assess urothelial proliferation and differentiation status, and the remaining 7 cases were processed for urothelial cell culture. Five normal adult urothelial samples were included as controls.

RESULTS

Immunohistological assessment indicated that 3 of 8 samples lacked urothelial differentiation associated expression of UPK3a or CK20. Four of 7 samples resulted in successful primary culture, with 1 sample lost to underlying infection and 2 not surviving in culture. All 4 cultures grew beyond passage 3 before senescence but all showed reduced proliferation capacity and a compromised ability to form a barrier urothelium compared to controls.

CONCLUSIONS

While normal human urothelium is highly regenerative and derived cells are highly proliferative in culture, our results with urothelium from abnormal pediatric bladders indicate a reduced capacity for proliferation and differentiation in vitro. This finding may indicate a need to identify alternative cell sources for engineered bladder reconstruction.

Regenerative medicine in urology

The term 'regenerative medicine' encompasses strategies for restoring or renewing tissue or organ function by: (i) in vivo tissue repair by in-growth of host cells into an acellular natural or synthetic biomaterial, (ii) implantation of tissue 'engineered'in vitro by seeding cultured cells into a biomaterial scaffold, and (iii) therapeutic cloning and stem cell-based tissue regeneration. In this article, we review recent developments underpinning the emerging science of regenerative medicine and critically assess where successful implementation of novel regenerative medicine approaches into urology practice might genuinely transform the quality of life of affected individuals. We advocate the need for an evidence-based approach supported by strong science and clinical objectivity.