Tissue engineering, stem cells, and cloning for the regeneration of urologic organs

What's in the Pipeline about Bladder Reconstructive Surgery? Some Remarks on the State of the Art

The fusion of engineering with cell biology and advances in biomaterials may lead to de novo construction of implantable organs. Engineering of neobladder from autologous urothelial and smooth muscle cells cultured on biocompatible, either synthetic or naturally-derived substrates, is now feasible in preclinical studies and may have clinical applicability in the near future. The development of a bioartificial bladder would warrant the prevention of both the metabolic and neoplastic shortcomings of the intestinal neobladder. Two tissue-engineering techniques for bladder reconstruction have been tested on animals: 1) the in vivo technique involves the use of naturally-derived biomaterials for functional native bladder regeneration 2) the in vitro technique involves the establishment of autologous urothelial and smooth muscle cell culture from the host's urinary tract, after which the cells are seeded on the biodegradable matrix-scaffold to create a composite graft that is implanted into the same host for complete histotectonic regeneration. Waiting for the creation of a complete tissue-engineered bladder with a trigone-shaped base, we suggest, in surgical oncology after radical cystectomy, the realization of conduit or continent pouch using tissue-engineered material.

Optical spectroscopic imaging for cell therapy and tissue engineering

Cell-based therapies hold great potential to treat a wide range of human diseases, yet the mechanisms responsible for cell migration and homing are not fully understood. Emerging molecular imaging technology enables in vivo tracking of transplanted cells and their therapeutic efficacy, which together will improve the clinical outcome of cell-based therapy. Particularly, optical imaging provides highly sensitive, safe (non-radioactive), cost-effective, and fast solutions for real-time cellular trafficking compared to other conventional molecular imaging modalities. This review provides a comprehensive overview of current advances in optical imaging for cell-based therapy and tissue engineering. We discuss different types of fluorescent probes and their labeling methods with a special focus on cardiovascular disease, cancer immunotherapy, and tissue regeneration. In addition, advantages and limitations of optical imaging-based cell tracking strategies along with the future perspectives to translate this imaging technique for a clinical realm are discussed.

Construction and characterization of human oral mucosa equivalent using hyper-dry amniotic membrane as a matrix

BACKGROUND

Human amniotic membrane(HAM) as a graft material has been used in various fields. Hyper-dry amniotic membrane (HD-AM) is a novel dried amniotic membrane that is easy to handle and can be preserved at room temperature without time limitation. The purpose of this study was to investigate the useful properties of HD-AM in reconstruction of the oral mucosa.

METHODS

Human oral keratinocytes were isolated and seeded on HD-AM in serum-free culture system. Oral mucosa equivalent (OME) was developed and transplanted onto full-thickness wound on athymic mice. The wound healing was analyzed and the OME both before and after transplantation was analyzed with hematoxylin-eosin staining and immunohistochemical staining for Cytokines 10 (CK10), Cytokines 16 (CK16), and Ivolucrin (IVL).

RESULTS

Oral keratinocytes spread and proliferated well on HD-AM. Two weeks after air-lifting, OME had formed with good differentiation and morphology. We confirmed immunohistochemically that the expression of CK10 was positive in all suprabasal layers, as was CK16 in the upper layers, while IVL was present in all cell layers. Three weeks after transplantation to athymic mice, the newly generated tissue had survived well with the smallest contraction. The epithelial cells of newly generated tissue expressed CK10 throughout in all suprabasal layers, IVL was mainly in the granular layer, and CK16 positive cells were observed in all spinous layer and granular layer but were not expressed in the mouse skin, all of which were similar to native gingival mucosa.

CONCLUSIONS

The OME with HD-AM as a matrix revealed a good morphology and stable wound healing. This study demonstrates that HD-AM is a useful and feasible biomaterial for oral mucosa reconstruction.

Mesenchymal stromal cells for sphincter regeneration

Stress urinary incontinence (SUI), defined as the involuntary loss of considerable amounts of urine during increased abdominal pressure (exertion, effort, sneezing, coughing, etc.), is a severe problem to the individuals affected and a significant medical, social and economic challenge. SUI is associated with pelvic floor debility, absence of detrusor contraction, or a loss of control over the sphincter muscle apparatus. The pathology includes an increasing loss of muscle cells, replacement of muscular tissue with fibrous tissue, and general aging associated processes of the sphincter complex. When current therapies fail to cure or improve SUI, application of regeneration-competent cells may be an alternative therapeutic option. Here we discuss different aspects of the biology of mesenchymal stromal cells, which are relevant to their clinical applications and for regenerating the sphincter complex. However, there are reports in favor of and against cell-based therapies. We therefore summarize the potential and the risks of cell-based therapies for the treatment of SUI.

A bilayered hybrid microfibrous PLGA--acellular matrix scaffold for hollow organ tissue engineering

Various synthetic and natural biomaterials have been used for regeneration of tissues and hollow organs. However, clinical outcome of reconstructive procedures remained challenging due to the lack of appropriate scaffold materials, supporting the needs of various cell types and providing a barrier function required in hollow organs. To address these problems, we have developed a bilayered hybrid scaffold comprising unique traits of polymeric microfibers and naturally derived acellular matrices and tested its potential for hollow organ regeneration in a rat bladder model. Hybrid scaffolds were fabricated by electrospinning of PLGA microfibers directly onto the abluminal surface of a bladder acellular matrix. Stability of this bilayered construct was established using modified spinning technique. The resulting 3-dimensional framework provided good support for growth, attachment and proliferation of primary bladder smooth muscle cells. Histological analysis in vivo at 4 and 8 weeks post implantation, revealed regeneration of bladder tissue structures consisting of urothelium, smooth muscle and collagen rich layers infiltrated with host cells and micro vessels. Furthermore, hybrid scaffolds maintained normal bladder capacity, whereas BAM recipients showed a significant distension of the bladder. These results demonstrate that this adaptable hybrid scaffold supports bladder regeneration and holds potential for engineering of bladder and other hollow organs.

Regenerative medicine strategies for treating neurogenic bladder

Neurogenic bladder is a general term encompassing various neurologic dysfunctions of the bladder and the external urethral sphincter. These can be caused by damage or disease. Therapeutic management options can be conservative, minimally invasive, or surgical. The current standard for surgical management is bladder augmentation using intestinal segments. However, because intestinal tissue possesses different functional characteristics than bladder tissue, numerous complications can ensue, including excess mucus production, urinary stone formation, and malignancy. As a result, investigators have sought after alternative solutions. Tissue engineering is a scientific field that uses combinations of cells and biomaterials to encourage regeneration of new, healthy tissue and offers an alternative approach for the replacement of lost or deficient organs, including the bladder. Promising results using tissue-engineered bladder have already been obtained in children with neurogenic bladder caused by myelomeningocele. Human clinical trials, governed by the Food and Drug Administration, are ongoing in the United States in both children and adults to further evaluate the safety and efficacy of this technology. This review will introduce the principles of tissue engineering and discuss how it can be used to treat refractory cases of neurogenic bladder.

Tissue engineering of human bladder

There are a number of conditions of the bladder that can lead to loss of function. Many of these require reconstructive procedures. However, current techniques may lead to a number of complications. Replacement of bladder tissues with functionally equivalent ones created in the laboratory could improve the outcome of reconstructive surgery. A review of the literature was conducted using PubMed to identify studies that provide evidence that tissue engineering techniques may be useful in the development of alternatives to current methods of bladder reconstruction. A number of animal studies and several clinical experiences show that it is possible to reconstruct the bladder using tissues and neo-organs produced in the laboratory. Materials that could be used to create functionally equivalent urologic tissues in the laboratory, especially non-autologous cells that have the potential to reject have many technical limitations. Current research suggests that the use of biomaterial-based, bladder-shaped scaffolds seeded with autologous urothelial and smooth muscle cells is currently the best option for bladder tissue engineering. Further research to develop novel biomaterials and cell sources, as well as information gained from developmental biology, signal transduction studies and studies of the wound healing response would be beneficial.

Regenerative medicine strategies for treatment of neurogenic bladder

Neurogenic bladder is a general term encompassing various neurologic dysfunctions in the bladder and external urethral sphincter caused by damage or disease. Therapeutic management options fall into the categories of conservative, minimally invasive or surgical. The current standard for surgical management is bladder augmentation using intestinal segments. However, because intestinal tissue possesses different functional characteristics to bladder tissue, numerous complications can ensue. Regenerative medicine uses combinations of cells and/or biomaterials to encourage regeneration of healthy tissue and offers an alternative approach for the replacement of lost or deficient organs, including the bladder. Promising results using the principles of regenerative medicine have already been obtained in children with neurogenic bladder caused by myelomeningocele. Human clinical trials, governed by the US FDA, are ongoing in the USA in both children and adults to further evaluate the safety and efficacy of this technology for regenerating bladders. More studies are in progress and additional advances in this field can be anticipated.

Composite scaffolds for the engineering of hollow organs and tissues

Several types of synthetic and naturally derived biomaterials have been used for augmenting hollow organs and tissues. However, each has desirable traits which were exclusive of the other. We fabricated a composite scaffold and tested its potential for the engineering of hollow organs in a bladder tissue model. The composite scaffolds were configured to accommodate a large number of cells on one side and were designed to serve as a barrier on the opposite side. The scaffolds were fabricated by bonding a collagen matrix to PGA polymers with threaded collagen fiber stitches. Urothelial and bladder smooth muscle cells were seeded on the composite scaffolds, and implanted in mice for up to 4 weeks and analyzed. Both cell types readily attached and proliferated on the scaffolds and formed bladder tissue-like structures in vivo. These structures consisted of a luminal urothelial layer, a collagen rich compartment and a peripheral smooth muscle layer. Biomechanical studies demonstrated that the tissues were readily elastic while maintaining their pre-configured structures. This study demonstrates that a composite scaffold can be fabricated with two completely different polymer systems for the engineering of hollow organs. The composite scaffolds are biocompatible, possess adequate physical and structural characteristics for bladder tissue engineering, and are able to form tissues in vivo. This scaffold system may be useful in patients requiring hollow organ replacement.

Management of urethrovaginal fistulae

PURPOSE OF REVIEW

Urethrovaginal fistulae are a rare condition. It is a conceptual mistake to consider urethrovaginal fistulae to be synonymous with vesicovaginal fistulae. Urethrovaginal fistulae are a different entity requiring special attention and treatment. Due to the wide variety and individuality of the clinical manifestations of these injuries, it is practically impossible to find and create common guidelines for treatment. Taking into account the difficulty of urethrovaginal fistula treatment, we decided to conduct a review of the current literature on this subject.

RECENT FINDINGS

Due to advances in obstetric care, urologists in the developed world encounter urethrovaginal fistulae rarely, and many of the fistulae seen are secondary to vaginal surgery. Surgical treatment procedures include direct primary anatomical repair and interpositional tissue restorations, mainly by Martius flap. Successful direct anatomical repair alone may result in the development of stress urinary incontinence or obstructed voiding in up to 50% of patients. Synthetic tape should be removed during fistula repair, which may lead to the resumption of stress incontinence.

SUMMARY

Prevention of urethrovaginal fistulae can be achieved through both improvements in obstetric care and adequate training in vaginal surgery. The success of any surgical treatment depends on careful patient selection, and assumes knowledge of all possible treatment options. Potential work needs to be directed towards the application of the newest molecular technologies.

Bioengineered tissues for urogenital repair in children

The most common congenital abnormalities involve the genitourinary system. These include hypospadias, in which the urethral opening develops in an improper position, and bladder exstrophy, in which the bladder develops on the outer surface of the abdomen. Children with these conditions will require immediate and multiple reconstructive surgeries. Currently, reconstruction may be performed with native nonurologic tissues (skin, gastrointestinal segments, or mucosa), homologous tissues from a donor (cadaver or living donor kidney), heterologous tissues or substances (bovine collagen), or artificial materials (silicone, polyurethane, teflon). However, these materials often lead to complications after reconstruction, either because the implanted tissue is rejected, or because inherently different functional parameters cause a mismatch in the system. For example, replacement of bladder tissue with gastrointestinal segments can be problematic due to the opposite ways in which these two tissues handle solutes-urologic tissue normally excretes material, and gastrointestinal tissue generally absorbs the same materials. This mismatched state can lead to metabolic complications as well as infection and other issues. The replacement of lost or deficient urologic tissues with functionally equivalent ones would improve the outcome of reconstructive surgery in the genitourinary system. This goal may soon be attainable with the use of tissue engineering techniques.

Management of urethrovaginal fistulas

OBJECTIVES

Despite the apparent similarity, urethrovaginal fistulas (UVFs) are not identical to vesicovaginal defects. Obstetric trauma and vaginal surgery are the causes of a majority of urethrovaginal fistulas.

METHODS

Careful preoperative evaluation is essential for identifying small UVFs or associated vesicovaginal fistulas and includes physical examination, cystourethroscopy, intravenous pyelography, ultrasonography, and urinalysis, but sometimes the final surgical plan can only be decided on after the patient is examined under anaesthesia with a metal sound in the urethra. Significant tissue deficit is the main characteristic of UVF repair and the minimal space present often does not allow placing any additional tissue between the urethral and vaginal walls.

RESULTS

Seventy-one women (mean age, 43 yr) with UVFs have been treated in our clinic. Our results have shown successful closure of the fistula in 90.14% of patients after primary surgery and 98.59% after a second operation. Postoperative stress urinary incontinence developed in 37 patients (52.11%). We used both synthetic and autologous slings for their management. Twenty-two patients (59.46%) were cured, 12 (32.43%) were improved, and 3 remained incontinent (8.11%). The long-term results of 21 patients with mean follow-up time of 99.6 mo show no fistula recurrence. Postoperative bladder outlet obstruction (5.63%) was successfully managed by urethral dilation or urethrotomy.

CONCLUSIONS

This article gives a detailed description of UVF surgical treatment. An attached DVD demonstrates one case that includes UVF primary repair, recurrent fistula repair, and surgery for continence restoration.

[Current status of tissue engineering in urology. Review of the literature]

In the eighties a new field of the medicine appears wich applies the principles of cellular cultivation to synthetic biodegradable polymers scaffolds with the purpose of creating autologous biological substitutes that could improve, maintain or restore the function of organs or damaged tissues. The Tissue Engineering constitutes a new discipline in full phase of development especially in USA, with multiple potential applications in several medical specialities. Our speciality can't remain indifferent to interest and encouraging future originated by this new science. In this work we have made a wide bibliographical revision in the Medline to know the antecedents, current state and the possible future applications of Tissue Engineering in Urology.

Adult stem cells in renal injury and repair (Review Article)

There has been considerable focus on the ability of bone marrow-derived cells to differentiate into non-haematopoietic cells of various tissue lineages, including cells of the kidney. This growing evidence has led to a reconsideration of the source of cells contributing to renal repair following injury. The kidney has an inherent ability for recovery and regeneration following acute damage. It is thought that dedifferentiation of glomerular and tubular cells to a more embryonic/mesenchymal phenotype represent key processes for recovery in response to damage. However, there has been much contention as to the source of regenerating renal cells. The present review focuses on new aspects of the plasticity of intrinsic renal cells and their role in renal remodelling and scarring. Growing support also suggests that bone marrow-derived cells have the ability to contribute to structural and functional repair following acute renal failure. Evidence for bone marrow cell engraftment in the repairing kidney leading to incorporation into a variety of tissue types is discussed. Because cell death and fibrosis is a common end-point in a variety of acute and chronic renal nephropathies, the paradigm of stem cell plasticity may have important implications in the cellular and pathological mechanisms of renal injury and repair. A better understanding of the processes controlling extra-renal cell engraftment and intrinsic renal cell differentiation may provide important clues for the development of new cell-based therapies in the field of renal reparative medicine.

Stem cell bioengineering for regenerative medicine

Stem cells can be used to treat a variety of diseases and several recent studies in animal models demonstrate the potential of bioengineering strategies targeting adult and embryonic stem cells. In order to obtain the desired cells for transplantation, stem cell bioengineering approaches entail the manipulation of environmental signals influencing cell survival, proliferation, self-renewal and differentiation. In that regard, multivariate analytical approaches have been used with success to optimise different stem cell culture processes. The genetic or molecular enhancement of stem cells is also a powerful means to control their proliferation or differentiation or to correct genetic defects in recipients. In the future, systems-level approaches have the potential to revolutionise the field of stem cell bioengineering by improving our understanding of regulatory networks controlling cellular behaviour. This advance in basic biology will be instrumental for the implementation of many stem cell-based regenerative therapies at the clinical level, as treatment accessibility will depend on the development of robust technologies to produce sufficient cell numbers.

[Experimental study about viability of autologous free graft in vitro cultivated urinary epithelium]

OBJECTIVE

The purpose of this study is to apply the in vitro keratinocyte culture techniques and the tissue engineering principles to urothelium, to obtain a three-dimensional autologous tissue suitable for grafting. We also showed the viability of free graft cultured urothelium in an experimental model.

MATERIAL AND METHODS

An animal experimental model was designed to apply the techniques of cellular culture and tissue engineering. Biopsy specimens of bladder mucosa were obtained, in vitro cultured and posteriorly implanted in each animal. We established three groups based on different follow-up periods (7, 14 and 30 days), and made a final histomorphological study to demonstrate the viability of the graft at the end of its respective follow-up period.

RESULTS

A three-dimensional in vitro tissue was obtained, composed of a bio-artificial submucosa (fibrin gel and fibroblast) where the uroepithelial cells were seeding; a biodegradable polyglycolic acid mesh was used to facilitate the tissue manipulation and implantation. In the morphological study all the implants appeared viable, but the grafts with longer implantations periods were better conformed, showing a tisular structure with multiple cellular layers.

CONCLUSIONS

In vitro keratinocyte culture techniques could be applied to other epithelial tissues as the urothelium. We obtained a three-dimensional in vitro tissue suitable for grafting in a relatively short time. The histological study demonstrated that free autologous urothelial graft is totally viable, opening future clinics applications.

Stem cells: Implications for urology

Stem cells are characterized by their potential immortality and are capable of self-renewal and differentiation. Stem cells are proposed to provide the potential to cure degenerative diseases and to give important clues regarding human development and aging. However, stem cell research has evoked enthusiasm and passionate debate regarding the ethics of their use in medicine and reproduction. In this article, the current understanding of the biology of stem cells, their application in urology, and some of the controversies regarding their use are discussed. Although the clinical application of stem cell technologies to urologic practice is likely to be well in the future, advances in this field hold great promise for the correction of a number of illnesses. Nevertheless, scientists and ethicists will continue to struggle with their ethical responsibilities to the patient and society.

Dynamic Gd-DTPA enhanced MRI as a surrogate marker of angiogenesis in tissue-engineered bladder constructs: A feasibility study in rabbits

PURPOSE

To evaluate the potential of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to assess angiogenesis in tissue-engineered bladder constructs in a blinded animal study, and compare different analysis approaches and their correlation with microvessel density (MVD).

MATERIALS AND METHODS

Constructs fortified with vascular endothelial growth factor (VEGF) for enhanced vascularity were grafted onto the bladder in nine rabbits. DCE-MRI of Gd-DTPA uptake was performed and analyzed using Tofts' model, the area under the concentration time curve (AUC), and the uptake slope. DCE-MRI parameters were compared to MVD determined with CD31 immunohistochemistry.

RESULTS

Significantly increased MVD was found in the high VEGF group (20 ng/g of tissue) but not at low VEGF (10 ng/g) (2.3x increase, P = 0.035 vs. 1.1x over control). Enhanced permeability at low VEGF was suggested by elevated K(trans), but overall correlation to MVD was poor. Significant correlation to MVD was obtained with AUC(8min) (r = 0.705, P = 0.034). Furthermore, AUC(8min) provided the most precise discrimination between different VEGF preparations and was the only parameter to show a significant increase (P = 0.0058) consistent with MVD changes at high VEGF.

CONCLUSION

Findings support DCE-MRI for evaluating angiogenesis in bladder constructs and suggest vessel changes other than density. Future studies should incorporate larger contrast agents and permeability assessment to devise an optimal DCE-MRI strategy.