Tissue Engineering For Urethral Reconstruction Research Articles

Tissue engineering of the urethra: where are we in 2019?

PurposeThe purpose of this review is to assess the potential role of tissue engineering for urethral reconstruction. It is well- recognised that urethrotomy remains the first-line therapy in the treatment of urethral stricture. Following on from the randomised study which recommended no difference between urethrotomy and urethral dilation, Steenkamp et al. reported long-term success rates of only 20%. Patients with longer strictures, penile or distal urethral strictures, and extensive periurethral spongiofibrosis typically do not respond well to repeated incisions. This report reviews the potential role of tissue engineering as applied to augmentation urethroplasty, which is the treatment of choice following failed urethrotomy.MethodsA review of the literature was carried out. The principal emphasis was on tissue engineering as applied to augmentation urethroplasty, but an introductory section reviews the use of urethrotomy and the background to contemporary practise with augmentation urethroplasty using oral mucosa.ResultsIt is evident that a cellular matrix which requires the ingrowth of cells is unlikely to be successful except for very short strictures. Other approaches such as injection of stem cells have not been adequately trialled in humans to date. Tissue-engineered substitute for autologous oral mucosa has been used and the results relating to this are reviewed.ConclusionsTissue engineering of autologous tissue for urethroplasty is expensive. It is unnecessary for the majority of cases, but could be potentially useful for very lengthy strictures, for instance, relating to lichen sclerosis. Whilst tissue-engineered oral mucosa has been successfully used, a great deal more work would be necessary to develop an appropriate matrix. Another study has looked at a larger series using an alternative tissue-engineered substitute, but the results have been very disappointing. At present, it has to be concluded that there is no effective and validated tissue engineering solution for the management of urethral stricture disease.

Urethral reconstruction with autologous urine-derived stem cells seeded in three-dimensional porous small intestinal submucosa in a rabbit model

BackgroundUrethral reconstruction is one of the great surgical challenges for urologists. A cell-based tissue-engineered urethra may be an alternative for patients who have complicated long strictures and need urethral reconstruction. Here, we demonstrated the feasibility of using autologous urine-derived stem cells (USCs) seeded on small intestinal submucosa (SIS) to repair a urethral defect in a rabbit model.MethodsAutologous USCs were obtained and characterized, and their capacity to differentiate into urothelial cells (UCs) and smooth muscle cells (SMCs) was tested. Then, USCs were labeled with PKH67, seeded on SIS, and transplanted to repair a urethral defect. The urethral defect model was surgically established in New Zealand white male rabbits. A ventral urethral gap was created, and the urethral mucosa was completely removed, with a mean rabbit penile urethra length of 2 cm. The urethral mucosal defect was repaired with a SIS scaffold (control group: SIS with no USCs; experimental group: autologous USC-seeded SIS; n = 12 for each group). A series of tests, including a retrograde urethrogram, histological analysis, and immunofluorescence, was undertaken 2, 3, 4, and 12 weeks after the operation to evaluate the effect of the autologous USCs on urethral reconstruction.ResultsAutologous USCs could be easily collected and induced to differentiate into UCs and SMCs. In addition, the urethral caliber, speed of urothelial regeneration, content of smooth muscle, and vessel density were significantly improved in the group with autologous USC-seeded SIS. Moreover, inflammatory cell infiltration and fibrosis were found in the control group with only SIS, but not in the experimental autologous USC-seeded SIS group. Furthermore, immunofluorescence staining demonstrated that the transplanted USCs differentiated into UCs and SMCs in vivo.ConclusionsAutologous USCs can be used as an alternative cell source for cell-based tissue engineering for urethral reconstruction.

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

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

MP19-15 COMPARATIVE ASSESSMENT OF ORAL AND URETHRAL MUCOSA CELL CULTURES AND IN VITRO ANALYSIS OF THEIR REGENERATIVE AND PROLIFERATIVE PROPERTIES FOR TISSUE ENGINEERING URETHRAL RECONSTRUCTION

INTRODUCTION AND OBJECTIVES: The success of tissue engineering for urethral reconstruction depends on the quality of the cultures used to prepare the grafts. We investigated the quality and the safety of cultured oral and urethra mucosa cells by comparing them, in order to determine the long-term in vitro regenerative properties, the capability to maintain their differentiation program, the heterogeneity of proliferative cell pool and the differentiation potential clonogenicity. METHODS: Urethral and oral specimens were obtained in accordance with the tenets of the Declaration of Helsinki from 18 patients who underwent urethroplasty with oral mucosal graft. The primary objectives of the analysis were to determine the cell yield and migratory capacity of oral and urethral mucosa cells, to compare the protein expression, to report the clonogenicity and the long-term proliferative potential. Furthermore we characterised stem cells of urethral and oral epithelia by holoclones analysis. Finally we investigated the safety of in vitro models regard cell growth. RESULTS: A statistically significant higher cell yield was obtained from oral mucosa than from urethra (t-test p1⁄40,02419), but no significant differences in the number of epithelial clones. Proximity of replicative senescence boosts cell cycle (faster woundhealing capacity) in oral mucosal more than in urethra. Keratinocytes from urethral and oral mucosa underwent a mean of 79.3 and 84 cell divisions, respectively, before senescence. A similar number of holoclones, meroclones and paraclones were found in oral mucosal and urethral proliferative compartments. It is shown that a single cultured stem cell maintains 100% clonogenicity, can be identified by selected markers and can provide differentiation. Analysis of protein expression suggests maintenance of a sitespecific differentiation programme, even under culture conditions. No tumorigenicity or other abnormal cell growth developed in cultured tissues. CONCLUSIONS: The comparison of all parameters highlighted a wide similarity of the oral and urethral mucosal cells, with better wound healing via oral epithelium. The oral mucosa cells seem to have a faster wound-healing capacity and a longer replicative survival. This data might have a clinical impact regard the current longer life expectancy of our patients.

Tissue engineering for human urethral reconstruction: systematic review of recent literature.

BackgroundTechniques to treat urethral stricture and hypospadias are restricted, as substitution of the unhealthy urethra with tissue from other origins (skin, bladder or buccal mucosa) has some limitations. Therefore, alternative sources of tissue for use in urethral reconstructions are considered, such as ex vivo engineered constructs.PurposeTo review recent literature on tissue engineering for human urethral reconstruction.MethodsA search was made in the PubMed and Embase databases restricted to the last 25 years and the English language.ResultsA total of 45 articles were selected describing the use of tissue engineering in urethral reconstruction. The results are discussed in four groups: autologous cell cultures, matrices/scaffolds, cell-seeded scaffolds, and clinical results of urethral reconstructions using these materials. Different progenitor cells were used, isolated from either urine or adipose tissue, but slightly better results were obtained with in vitro expansion of urothelial cells from bladder washings, tissue biopsies from the bladder (urothelium) or the oral cavity (buccal mucosa). Compared with a synthetic scaffold, a biological scaffold has the advantage of bioactive extracellular matrix proteins on its surface. When applied clinically, a non-seeded matrix only seems suited for use as an onlay graft. When a tubularized substitution is the aim, a cell-seeded construct seems more beneficial.ConclusionsConsiderable experience is available with tissue engineering of urethral tissue in vitro, produced with cells of different origin. Clinical and in vivo experiments show promising results.

Tissue engineering in urethral reconstruction—an update

The field of tissue engineering is rapidly progressing. Much work has gone into developing a tissue engineered urethral graft. Current grafts, when long, can create initial donor site morbidity. In this article, we evaluate the progress made in finding a tissue engineered substitute for the human urethra. Researchers have investigated cell-free and cell-seeded grafts. We discuss different approaches to developing these grafts and review their reported successes in human studies. With further work, tissue engineered grafts may facilitate the management of lengthy urethral strictures requiring oral mucosa substitution urethroplasty.

The Evolution of Urogenital Tissue Engineering

In Boston in 1954, Hartwell Harrison, the chief of urology at Harvard University, harvested a kidney and performed the first ever human organ transplantation [1]. The concept of cell transplantation developed after kidney transplantation and led to the first human bone marrow cell transplantation in the 1970s. At that time, researchers combined the scientific fields of device and material sciences with cell biology and in effect pioneered a new field called [2]. The first use of the term can be traced in the literature to a reference dealing with corneal tissue in 1985 [3]. The discovery of mouse embryonic stem (ES) cells in the early 1980s gave a huge boost to the stem cell field and led to the description of human ES (hES) in 1998 [4]. The creation of the first cloned mammal, a sheep named Dolly, was announced in 1997 [5]. Two years later, the term was coined to describe the unifying goal of cell transplantation, tissue engineering, and nuclear transfer, i.e., the regeneration of living tissues and organs [6]. Over the past decade, the number of patients waiting for transplantation has doubled, while the actual number of transplantations has remained practically unchanged. This disparity is a consequence of our aging population. As time passes, we get older and older, and medicine does a better job of keeping us alive. However, as we age, our organs tend to fail more often. This, then, is our new challenge. Although advanced medicines and treatments have saved many lives, we now face a major shortage of organs. The human body has many organs, each of which has a cell population that is ready to take over at the time of injury. It happens every day of our lives. Thus, our body is constantly regenerating. When challenges occur through an injury or a disease, the human body's first reaction is to seal off the area. Whether it is the organs inside the body or the skin, the development of scar tissue is the immediate response to solve the problem. How can we harness that power? One way is through the use of smart biomaterials. In 1996, the first use of natural biomaterials in humans for tissue regeneration demonstrated that smart biomaterials could be used as a bridge in the treatment of an injured urethra [7]. First, the injured area was closed off from the outside environment. Then, cells that were regenerated in the body crossed the bridge and followed the pathway or channel that connected to the bladder or to outside the body. Tissue engineering for urethral reconstruction may involve matrices alone, wherein the body's natural ability to regenerate is used to orientate or direct new tissue growth, or the use of matrices with cells. Acellular collagen matrices that are derived from donor bladder submucosa have been used both experimentally and clinically for urethral replacement. Urethra successfully regenerates, but only over a limited distance. What if the injury is in a larger organ? What can we do to repair injuries in structures that are much larger than the limited distance of regeneration? Researchers have turned to cells to solve these problems. The strategy is to take a very small piece of tissue from the injured or diseased organ and to tease that tissue apart into its basic components. Then, the patient's own cells are taken and grown outside the body in large quantities. Next, scaffold materials are used. The scaffold acts as a cell delivery vehicle, bringing the cells into the body and allowing them to regenerate into new tissue. Scaffold materials are designed to disintegrate in the body a few months later. Currently, gastrointestinal (GI) segments are commonly being used as tissue for bladder and urethral replacement or repair. However, GI tissue is designed to absorb specific solutes, whereas bladder and urethral tissue are designed for the excretion of solutes. When GI tissue comes in contact with the urinary tract, multiple complications may occur, such as infection, metabolic disturbances, urolithiasis, perforation, increased mucus production, and malignancy [8]. James J. Yoo, the Associate Director of the Wake Forest Institute for Regenerative Medicine, focuses his work on growing and regenerating tissues and organs. His team engineered the first lab-grown organ to be implanted into a human - a bladder. His article 'in this issue of the Journal' [9] will introduce the novel tissue engineering-based regenerative strategies that are being applied to bladder reconstruction and will discuss how these strategies can be used to treat the neurogenic bladder.

Human urine-derived stem cells seeded in a modified 3D porous small intestinal submucosa scaffold for urethral tissue engineering

The goal of this study was to determine whether urothelial cells (UC) and smooth muscle cells (SMC) derived from the differentiation of urine-derived stem cells (USC) could be used to form engineered urethral tissue when seeded on a modified 3-D porous small intestinal submucosa (SIS) scaffold. Cells were obtained from 12 voided urine samples from 4 healthy individuals. USC were isolated, characterized and induced to differentiate into UC and SMC. Fresh SIS derived from pigs was decellularized with 5% peracetic acid (PAA). Differentiated UC and SMC derived from USC were seeded onto SIS scaffolds with highly porous microstructure in a layered co-culture fashion and cultured under dynamic conditions for one week. The seeded cells formed multiple uniform layers on the SIS and penetrated deeper into the porous matrix during dynamic culture. USC that were induced to differentiate also expressed UC markers (Uroplakin-III and AE1/AE3) or SMC markers (α-SM actin, desmin, and myosin) after implantation into athymic mice for one month, and the resulting tissues were similar to those formed when UC and SMC derived from native ureter were used. In conclusion, UC and SMC derived from USC could be maintained on 3-D porous SIS scaffold. The dynamic culture system promoted 3-D cell–matrix ingrowth and development of a multilayer mucosal structure similar to that of native urinary tract tissue. USC may serve as an alternative cell source in cell-based tissue engineering for urethral reconstruction or other urological tissue repair.

Tissue engineering in urethral reconstruction.

Tissue engineering is an exciting and rapidly evolving technology. In this review, we discuss the recent progress made in the field of urethral reconstruction and consider the clinical implications and further advancement of these endeavours.