Scaffold Seeded With Cells Is Essential in Urothelium Regeneration and Tissue Remodeling In Vivo After Bladder Augmentation Using in Vitro Engineered Graft

Urinary Bladder Patch Made with Decellularized Vein Scaffold Seeded with Adipose-Derived Mesenchymal Stem Cells: Model in Rabbits

BACKGROUND

To evaluate tissue regeneration of the urinary bladder after the implantation of a decellularized vein sown with autologous adipose-derived mesenchymal stem cells (ASC) on luminal surfaces.

METHODS

New Zealand rabbits (n = 10) were distributed in two groups: Group Bioscaffold alone (G1)-decellularized vena cava (1 cm2) was implanted, and Group Bioscaffold plus ACSs (G2)-decellularized vena cava (1 cm2) containing ASCs were implanted. ASCs were expanded, characterized, and maintained for one week in culture with a decellularized vein scaffold. The implants were performed under general anesthesia using a continuous suture pattern. Afterward, 21 d (day) specimens were collected and analyzed by hematoxylin and eosin (HE) histology and scanning electron microscopy (SEM).

RESULTS

The integrity of the urinary bladder was maintained in both groups. A superior regenerative process was observed in the G2 group, compared to the G1 group. We observed a greater urothelial epithelialization and maturity of the mucosa and submucosa fibroblasts. Furthermore, SEM demonstrated a notable amount of urothelial villus in the G2 group.

CONCLUSION

Decellularized vena cava scaffolds were able to maintain the integrity of the urinary bladder in the proposed model. In addition, ASCs accelerated the regenerative process development, observed primarily by the new urothelial epithelization and the maturity of mucosa and submucosa fibroblasts.

Bladder Substitution: The Role of Tissue Engineering and Biomaterials

Tissue engineering could play a major role in the setting of urinary diversion. Several conditions cause the functional or anatomic loss of urinary bladder, requiring reconstructive procedures on the urinary tract. Three main approaches are possible: (i) incontinent cutaneous diversion, such as ureterocutaneostomy, colonic or ileal conduit, (ii) continent pouch created using different segments of the gastrointestinal system and a cutaneous stoma, and (iii) orthotopic urinary diversion with an intestinal segment with spherical configuration and anastomosis to the urethra (neobladder, orthotopic bladder substitution). However, urinary diversions are associated with numerous complications, such as mucus production, electrolyte imbalances and increased malignant transformation potential. In this context, tissue engineering would have the fundamental role of creating a suitable material for urinary diversion, avoiding the use of bowel segments, and reducing complications. Materials used for the purpose of urinary substitution are biological in case of acellular tissue matrices and naturally derived materials, or artificial in case of synthetic polymers. However, only limited success has been achieved so far. The aim of this review is to present the ideal properties of a urinary tissue engineered scaffold and to examine the results achieved so far. The most promising studies have been highlighted in order to guide the choice of scaffolds and cells type for further evolutions.

Incorporation of Smooth Muscle Cells Derived from Human Adipose Stem Cells on Poly(Lactic-co-Glycolic Acid) Scaffold for the Reconstruction of Subtotally Resected Urinary Bladder in Athymic Rats

BACKGROUND

The urinary tract can be affected by both congenital abnormalities as well as acquired disorders, such as cancer, trauma, infection, inflammation, and iatrogenic injuries, all of which may lead to organ damage requiring eventual reconstruction. As a gold standard, gastrointestinal segment is used for urinary bladder reconstruction. However, one major problem is that while bladder tissue prevents reabsorption of specific solutes, gastrointestinal tissue actually absorbs them. Therefore, tissue engineering approach had been attempted to provide an alternative tissue graft for urinary bladder reconstruction.

METHODS

Human adipose-derived stem cells isolated from fat tissues were differentiated into smooth muscle cells and then seeded onto a triple-layered PLGA sheet to form a bladder construct. Adult athymic rats underwent subtotal urinary bladder resection and were divided into three treatment groups (n = 3): Group 1 ("sham") underwent anastomosis of the remaining basal region, Group 2 underwent reconstruction with the cell-free scaffold, and Group 3 underwent reconstruction with the tissue-engineered bladder construct. Animals were monitored on a daily basis and euthanisation was performed whenever a decline in animal health was detected.

RESULTS

All animals in Groups 1, 2 and 3 survived for at least 7 days and were followed up to a maximum of 12 weeks post-operation. It was found that by Day 14, substantial ingrowth of smooth muscle and urothelial cells had occurred in Group 2 and 3. In the long-term follow up of group 3 (tissue-engineered bladder construct group), it was found that the urinary bladder wall was completely regenerated and bladder function was fully restored. Urodynamic and radiological evaluations of the reconstructed bladder showed a return to normal bladder volume and function.Histological analysis revealed the presence of three muscular layers and a urothelium similar to that of a normal bladder. Immunohistochemical staining using human-specific myocyte markers (myosin heavy chain and smoothelin) confirmed the incorporation of the seeded cells in the newly regenerated muscular layers.

CONCLUSION

Implantation of PLGA construct seeded with smooth muscle cells derived from human adipose stem cells can lead to regeneration of the muscular layers and urothelial ingrowth, leading to formation of a completely functional urinary bladder.

Poly-phosphate increases SMC differentiation of mesenchymal stem cells on PLGA-polyurethane nanofibrous scaffold

The use of bioactive scaffolds in tissue engineering has a significant effect on the damaged tissue healing by an increase in speed and quality of the process. Herein, electrospinning was applied to fabricate composite nanofibrous scaffolds by Poly lactic-co-glycolic acid (PLGA) and Polyurethane (PU) with and without poly-phosphate (poly-P). Scaffolds were characterized morphologically by scanning electron microscope (SEM), and their biocompatibility was also investigated by SEM, protein adsorption, cell attachment and survival assays. The applicability of the scaffolds for bladder tissue engineering was also evaluated by culturing mesenchymal stem cells (MSCs) on the scaffolds and their differentiation into smooth muscle cell (SMC) was studied at the gene and protein levels. The results demonstrated that scaffold biocompatibility was increased significantly by loading poly-P. SMC related gene and protein expression level in MSCs cultured on poly-P-loaded scaffold was also increased significantly compared to those cells cultured on empty scaffold. It can be concluded that poly-P hasn’t also increased scaffold biocompatibility, but also SMC differentiation potential of MSCs was also increased while cultured on the poly-P containing scaffold compared to the empty scaffold. Taken together, our study showed that PLGA–PU–poly-P alone and in combination with MSCs has a promising potential for support urinary bladder smooth muscle tissue engineering.

Dynamic reciprocity in cell-scaffold interactions

Tissue engineering in urology has shown considerable promise. However, there is still much to understand, particularly regarding the interactions between scaffolds and their host environment, how these interactions regulate regeneration and how they may be enhanced for optimal tissue repair. In this review, we discuss the concept of dynamic reciprocity as applied to tissue engineering, i.e. how bi-directional signaling between implanted scaffolds and host tissues such as the bladder drives the process of constructive remodeling to ensure successful graft integration and tissue repair. The impact of scaffold content and configuration, the contribution of endogenous and exogenous bioactive factors, the influence of the host immune response and the functional interaction with mechanical stimulation are all considered. In addition, the temporal relationships of host tissue ingrowth, bioactive factor mobilization, scaffold degradation and immune cell infiltration, as well as the reciprocal signaling between discrete cell types and scaffolds are discussed. Improved understanding of these aspects of tissue repair will identify opportunities for optimization of repair that could be exploited to enhance regenerative medicine strategies for urology in future studies.

Biomatrices for bladder reconstruction

There is a demand for tissue engineering of the bladder needed by patients who experience a neurogenic bladder or idiopathic detrusor overactivity. To avoid complications from augmentation cystoplasty, the field of tissue engineering seeks optimal scaffolds for bladder reconstruction. Naturally derived biomaterials as well as synthetic and natural polymers have been explored as bladder substitutes. To improve regenerative properties, these biomaterials have been conjugated with functional molecules, combined with nanotechology, or seeded with exogenous cells. Although most studies reported complete and functional bladder regeneration in small-animal models, results from large-animal models and human clinical trials varied. For functional bladder regeneration, procedures for biomaterial fabrication, incorporation of biologically active agents, introduction of nanotechnology, and application of stem-cell technology need to be standardized. Advanced molecular and medical technologies such as next generation sequencing and magnetic resonance imaging can be introduced for mechanistic understanding and non-invasive monitoring of regeneration processes, respectively.

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.

Tissue engineering in animal models for urinary diversion: a systematic review

Tissue engineering and regenerative medicine (TERM) approaches may provide alternatives for gastrointestinal tissue in urinary diversion. To continue to clinically translatable studies, TERM alternatives need to be evaluated in (large) controlled and standardized animal studies. Here, we investigated all evidence for the efficacy of tissue engineered constructs in animal models for urinary diversion. Studies investigating this subject were identified through a systematic search of three different databases (PubMed, Embase and Web of Science). From each study, animal characteristics, study characteristics and experimental outcomes for meta-analyses were tabulated. Furthermore, the reporting of items vital for study replication was assessed. The retrieved studies (8 in total) showed extreme heterogeneity in study design, including animal models, biomaterials and type of urinary diversion. All studies were feasibility studies, indicating the novelty of this field. None of the studies included appropriate control groups, i.e. a comparison with the classical treatment using GI tissue. The meta-analysis showed a trend towards successful experimentation in larger animals although no specific animal species could be identified as the most suitable model. Larger animals appear to allow a better translation to the human situation, with respect to anatomy and surgical approaches. It was unclear whether the use of cells benefits the formation of a neo urinary conduit. The reporting of the methodology and data according to standardized guidelines was insufficient and should be improved to increase the value of such publications. In conclusion, animal models in the field of TERM for urinary diversion have probably been chosen for reasons other than their predictive value. Controlled and comparative long term animal studies, with adequate methodological reporting are needed to proceed to clinical translatable studies. This will aid in good quality research with the reduction in the use of animals and an increase in empirical evidence of biomedical research.

Tissue-engineered cholecyst-derived extracellular matrix: a biomaterial for in vivo autologous bladder muscular wall regeneration

PURPOSE

To compare the biocompatibility and histological aspects of cholecyst-derived extra cellular matrix (CDECM) graft, either alone or with application of autologous detrusor muscles small fragments (ADMSF) on rabbit bladder mucosa for bladder augmentation.

METHODS

The gallbladders were acellularized and evaluated for preserved acellular matrix scaffold and biophysical properties. Thirty rabbits were divided into five groups. Rabbits in the control group underwent partial detrusorectomy followed by perivesical fat coverage. Groups I and II underwent the same procedure and bladder mucosa was covered either by acellular rabbit gallbladder (ARG) (group I) or acellular sheep gallbladder (ASG) (group II). Groups III and IV underwent detrusorectomy and the bladder mucosal was seeded by ADMSF and covered by ARG (group III), or ASG (group IV). Biopsies were taken at 4, 12, and 24 weeks postoperatively.

RESULTS

Higher expression of CD34 endothelial progenitor cells, CD31 microvessels, α-smooth muscle actin, S100, and cytokeratin with more organized muscular wall generation was demonstrated in groups III and IV. Expression of IHC markers was higher in groups III and IV compared with groups I and II in all the time points.

CONCLUSION

The current study confirmed that autologous fragment-seeded CDECM can be considered as a reliable natural collagen scaffold for bladder augmentation.

3D reconstitution of nerve-blood vessel networks using skeletal muscle-derived multipotent stem cell sheet pellets

AIM

To cover the large tissue deficits associated with significant loss of function following surgery, a 3D gel-patch-like nerve-vascular reconstitution system was developed using the skeletal muscle-derived multipotent stem cell (Sk-MSC) sheet pellet.

MATERIALS & METHODS

The Sk-MSC sheet pellet was prepared from GFP transgenic mice by the collagenase extraction and 7 days expansion cell culture, and transplanted into a severe muscle damage model with large disruptions to muscle fibers, blood vessels and peripheral nerves.

RESULTS

At 4 weeks after transplantation, engrafted cells contributed to nerve-vascular regeneration associated with cellular differentiation into Schwann cells, perineurial/endoneurial cells, vascular endothelial cells and pericytes. However, skeletal myogenic differentiation was scarcely observed. Paracrine effects regarding donor cells/tissues could also be expected, because of the active expression of neurogenic and vasculogenic factor mRNAs in the sheet pellet.

CONCLUSION

These results indicate that the vigorous skeletal myogenic potential of Sk-MSCs was clearly reduced in the sheet pellet preparation and this method may be a useful adjuvant for nerve-vascular regeneration in various tissue engineering applications.

Morphological and urodynamic evaluation of urinary bladder wall regeneration: muscles guarantee contraction but not proper function--a rat model research study

BACKGROUND

Numerous studies are ungoing to develop a substitute for the native urinary bladder wall. The principals of tissue engineering approaches to urinary bladder wall augmentation require a favorable environment for smooth muscle regeneration, which is crucial for bladder function. This study was performed to evaluate bone marrow mesenchymal stem cells (BMSC) seeded on to amniotic membranes fixed to Tachosil sponges as grafts for urinary bladder muscle layer augmentation in a syngenic rat model.

MATERIALS AND METHODS

Amniotic membranes seeded with BMSC and covered by Tachosil sponges were implanted as multilayer grafts into nine rats to regenerate the urinary bladder wall. The control group consisted of 12 healthy rats. Urodynamic examinations included contraction, elasticity, compliance, and urinary bladder motor activity. Hematocylin and eosin and Masson's trichrome stains were used to evaluate muscle regeneration; histological data were digitally analyzed with the ImageJ tool.

RESULTS

The area of muscle bundles ranged from 5% to 25% or 32% to 41% in control versus reconstructed bladders, respectively. Among nine animals with reconstructed urinary bladders, urodynamic evaluation revealed bladder motor hyperactivity with regular (n = 4) or irregular (n = 1) storage and voiding phases, as well as proper bladder motor activity with a large bladder capacity (n = 1). No bladder contractility was recorded in one case and large stones developed in two animals, which made functional studies impossible.

CONCLUSIONS

Regenerated smooth muscle cells created an autonomic cell population that was poorly assimilated to the rest of the urinary bladder wall. The histological presence of a regenerated muscle layer did not guarantee proper urinary bladder function.

Urine is a highly cytotoxic agent: does it influence stem cell therapies in urology?

The state of art of stem cell therapies in urologic regenerative medicine is still under development. There are still many issues before advances in tissue engineering can be introduced for clinical application. The essential question is whether stem cells should be seeded on the urinary tract lumen side. The present experiment, using Real-Time Cell Analyzer (RTCA) DP (Dual Plate) of the xCellligence system (Roche Applied Science, Mannheim, Germany), allowed us to monitor cellular events in real time. In this study we examined the influence of urine on bone marrow-derived mesenchymal stem cells (MSC). Cells were exposed to medium mixed with urine (1:1), medium mix with PBS (Phosphate Buffered Saline) (1:1), only urine, and whole medium without cells as background. The cell number was significantly lower in all groups exposed on medium mixed with urine and urine alone. The results showed that urine is a highly cytotoxic agent whose role in urologic regenerative medicine is underestimated.

Tissue engineering for the oncologic urinary bladder

Urinary diversion after radical cystectomy in patients with bladder cancer normally takes the form of an ileal conduit or neobladder. However, such diversions are associated with a number of complications including increased risk of infection. A plausible alternative is the construction of a neobladder (or bladder tissue) in vitro using autologous cells harvested from the patient. Biomaterials can be used as a scaffold for naturally occurring regenerative stem cells to latch onto to regrow the bladder smooth muscle and epithelium. Such engineered tissues show great promise in urologic tissue regeneration, but are faced with a number of challenges. For example, the differentiation mesenchymal stem cells from various sources can be difficult and the smooth muscle cells formed do not precisely mimic the natural cells.

Stem cells for urinary tract regeneration

Regeneration of the urinary bladder is a complicated task, due to organ dimensions and diseases (cancer, interstitial cystitis) when autologous bladder cells cannot be used. Cancer is the most frequent indication for bladder removal (cystectomy). Stem cells can be used with the guarantee of the sufficient cell number for the in vitro construction of the urinary bladder wall. Tissue engineering techniques hold great promise for regeneration of dysfunctional urinary sphincter. Denervation following surgical procedures or injuries results in weakness of the urethral sphincter and stress urinary incontinence. Injectable therapies and the potential of stem cells for sphincter restoration was presented in this review. The aim of this review was to present possibilities of urinary bladder regeneration with the use of stem cells and tissue engineering techniques.

Application of different scaffolds for bladder wall regeneration: the bladder as a natural bioreactor

OBJECTIVES

We investigated the potential of different scaffolds for in vivo construction of bladder muscular and urothelial wall. Bladder wall was used as a bioreactor to create a model of the natural environment for cellular interactions, growth, and differentiation.

METHODS

Forty rabbits were divided into 10 groups. Different scaffolds were implanted between bladder mucosa and seromuscular layer. Scaffolds used in each group were one layer or a three-layered combination of tissue-engineered pericardium (TEP), biofilm, and polyglycolic acid (PGA). In all groups, a biopsy of full thickness of bladder was dissected. Muscular and urothelial layers were separated and minced into small fragments. Fragments were seeded above the urothelial layer and urothelial fragments were placed on the scaffold under the seromuscular layer. One group served as control and no scaffold was inserted between the separated bladder layers. After 2 and 6 weeks, biopsies were performed for histologic examinations (trichrome, smooth muscle α-actin, and pancytokeratin AE1/AE3, CD34, CD31).

RESULTS

Histopathological examinations showed granulomatous reaction and severe inflammation in biofilm-containing groups. Samples with TEP alone and with PGA-coated TEP as scaffolds revealed more organized bladder wall in two different layers with mature urothelial and smooth muscle cells. The number of CD34+ cells and CD31+ microvessels increased continuously during 6 weeks.

CONCLUSIONS

Our results demonstrated the effective role of PGA-coated TEP as a potential scaffold for muscular and urothelial fragment seeding in bladder wall acting as a natural bioreactor. Biodegradable scaffolds could be helpful in association with acellular matrices to optimize the cell attachment and in vivo bladder wall construction.

Histerocystoplasty: a novel surgical procedure in the rat

BACKGROUND

Enterocystoplasties are associated to complications. To avoid them, different types of tissue templates have been used to augment the bladder and induce native bladder regeneration.

MATERIALS AND METHODS

A novel surgical technique for bladder reconstruction using autologous uterine tissue was evaluated in a rat model. Forty-two female Wistar rats were randomly allocated into three groups: sham-operation hysterocystorrhaphy (n = 12), hysterocystoplasty (n = 18), and control (n = 12). Two weeks after surgery, ultrasound examination of the bladder was performed. At 2, 4, or 6 mo after surgery, the rats were anesthetized and blood and urine samples were taken. They were then euthanized and post-mortem and histologic examination were performed. Ultrasound examination, analytical parameters and weight control, as well as gross and histologic examination were performed in all the operated animals. The statistical analysis was performed using Kruskal-Wallis and the extension of Fisher's exact tests. Significance was set at 5% (P < 0.05).

RESULTS

Serum chemistry, blood count and peripheral blood smears, electrolytes, and urinary parameters were all within the normal range for the rat. Histologic sections of the surgically augmented zone between the bladder and uterine horn demonstrated urothelial epithelization, providing adequate coverage of the transition area in 72.22% of the rats that underwent hysterocystoplasty.

CONCLUSIONS

The hysterocystoplasty was technically viable in all the cases and proved to be an easy and safe surgical model for bladder reconstruction. All animals were healthy after surgery and all systemic parameters analyzed were within normal physiologic range for the rat.

Will tissue-engineered urinary bladders change indications for a laparoscopic cystectomy?

Radical open cystectomy is a treatment of choice for muscle invasive urinary bladder cancer. Laparoscopic radical cystectomy (LapRC) is surgically advanced and is an extremely difficult technique but presents many advantages. Urinary diversion (conduit, pouch or neobladder) when performed during laparoscopy necessitates a conversion to open procedure. Urinary diversion using an autologous bowel is associated with longer operative times and complications. The authors have analyzed the LapRC procedure and its 2 main parts--that is, bladder resection and urinary diversion. The emphasis was on the operative time and complications related to the urinary diversion procedure. A urinary diversion created in vitro could make the LapRC totally intracorporeal, and it could be completed within an acceptable time. Tissue engineering techniques used for urinary diversion after cystectomy shorten the operative time and help avoid serious complications related to bowel surgery. LapRC with tissue-engineered urinary diversion could become a management of choice for muscle invasive bladder cancer.

Hair stem cells for bladder regeneration in rats: preliminary results

BACKGROUND

A variety of tissue engineering techniques are currently under development or investigation for bladder augmentation, but so far no approach is clearly superior. The aim of this study was to compare the suitability for cystoplasty augmentation in rats of in vivo implanted acellular bladder matrices (BAM) previously seeded with hair follicle stem cells and that of matrices implanted without the cells.

MATERIALS AND METHODS

The rat hair follicle stem cell line was positive for CD34, p63, and Ki-67. 1 x 10(6) cells from 34 to 40 passages seeded onto nine BAM scaffolds were cultured for one week. Nine other scaffolds were left unseeded. Scaffolds were grafted into a surgically created defect within the anterior bladder wall: nine rats with acellular matrices and nine with cell-seeded BAM. Rats observed for six months were killed in monthly intervals. We performed gross examination, X-ray cystography, and hematoxylin-eosin, cytokine (CK)-7, CK-20, myoglobin, and desmin staining of the excised bladders.

RESULTS

Minimal adhesions were observed and urinary leakage was noted in one case. Two animals died in the acellular group. Rats developed stone disease in bladders reconstructed with acellular BAM. Bladder capacity was similar, but the shape was regular and characteristically oval only in bladders grafted with cell-seeded BAM. Muscle layers in the apical parts of the reconstructed bladder walls were extremely thin in the cases of acellular grafts and thicker in bladders reconstructed with cell-seeded grafts. Muscle layer regeneration was better in the cell-seeded group. Urothelium regenerated in all animals.

CONCLUSIONS

We have shown that hair follicle stem cells may be used for rat bladder wall regeneration.

Stem cell bioprocessing: fundamentals and principles

In recent years, the potential of stem cell research for tissue engineering-based therapies and regenerative medicine clinical applications has become well established. In 2006, Chung pioneered the first entire organ transplant using adult stem cells and a scaffold for clinical evaluation. With this a new milestone was achieved, with seven patients with myelomeningocele receiving stem cell-derived bladder transplants resulting in substantial improvements in their quality of life. While a bladder is a relatively simple organ, the breakthrough highlights the incredible benefits that can be gained from the cross-disciplinary nature of tissue engineering and regenerative medicine (TERM) that encompasses stem cell research and stem cell bioprocessing. Unquestionably, the development of bioprocess technologies for the transfer of the current laboratory-based practice of stem cell tissue culture to the clinic as therapeutics necessitates the application of engineering principles and practices to achieve control, reproducibility, automation, validation and safety of the process and the product. The successful translation will require contributions from fundamental research (from developmental biology to the 'omics' technologies and advances in immunology) and from existing industrial practice (biologics), especially on automation, quality assurance and regulation. The timely development, integration and execution of various components will be critical-failures of the past (such as in the commercialization of skin equivalents) on marketing, pricing, production and advertising should not be repeated. This review aims to address the principles required for successful stem cell bioprocessing so that they can be applied deftly to 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.

Using hair-follicle stem cells for urinary bladder-wall regeneration

There are many diseases in which autologous urothelial and muscle cells cannot be used for in vitro construction of the urinary bladder wall for augmentation (cystoplasty). These diseases are the most frequent indications for bladder augmentation. The present paper focuses on the idea of harvesting potentially multipotent stem cells out of hair follicles in order to use them for regeneration of the urinary bladder wall. Current clinical practice suggests the use of cultures enriched with progenitors. The hair follicle stem cell niche gives an opportunity to reduce the invasiveness of harvesting these cells. Both epithelial and dermal multipotent stem cells populations within hair follicles raise new possibilities for tissue engineering of the urinary bladder. The hypothesis is that hair-follicle stem cells can be used, with the guarantee of the sufficient cell number, for a construction in vitro of the urinary bladder wall replacement.

The Artificial Conduit for Urinary Diversion in Rats: A Preliminary Study

OBJECTIVES

Small intestinal submucosa forms a scaffold for tubular construction. The aim of this study was to build the artificial conduit using small intestinal submucosa (SIS) and 3T3 fibroblasts for urinary diversion in rats.

MATERIALS AND METHODS

3T3 fibroblasts were multiplied to a total of 10(9). Two groups consisted of three Wistar rats each. The left ureters were separated from the bladder and anastomosed to the proximal end of the tubular scaffold. No splitting of the ureteral junction or drainage was done. The distal end of the scaffold was implanted into a previously performed channel in the abdominal wall. Cell-seeded grafts were used in the first group and acellular SIS scaffolds in the second group. Rats were sacrificed after 2 and 4 weeks. X-ray pyelography was performed. Hematoxylin and eosin staining was prepared from conduit cross sections.

RESULTS

All animals survived the observation. An inflammatory reaction was observed within the peritoneal cavity in both groups. It was difficult to dissect the adhesions in the cell-seeded group. The ureteral-conduit anastomoses were tight in five cases, except there was leakage and pseudocyst formation after 14 days in one cell-seeded graft. No ureterohydronephrosis was observed in two acellular conduits after 14 or 30 days, and in one case of a cell-seeded graft. A neovascularisation process was observed in the acellular conduit after a month. Multilayered epithelium covered the conduit lumen near the anastomosis at the distal end of acellular conduit, a small islet-forming epithelial layer was observed after a month.

CONCLUSIONS

3T3 fibroblasts cannot serve as a "feeder layer" for ureteral augmentation. It seems that there is no need to split the ureteral-conduit junction. An SIS scaffold was used for tubular construction for urinary diversion in an animal model.