Application of bladder acellular matrix in urinary bladder regeneration: the state of the art and future directions. Biomed Res Int. 2015;2015:613439. [PMID: 25793199 PMCID: PMC4352424 DOI: 10.1155/2015/613439]

Bladder Reconstruction in Cats Using In-Body Tissue Architecture (iBTA)-Induced Biosheet

Urinary tract diseases are common in cats, and often require surgical reconstruction. Here, to explore the possibility of urinary tract reconstruction in cats using in-body tissue architecture (iBTA), biosheets fabricated using iBTA technology were implanted into the feline bladder and the regeneration process was histologically evaluated. The biosheets were prepared by embedding molds into the dorsal subcutaneous pouches of six cats for 2 months. A section of the bladder wall was removed, and the biosheets were sutured to the excision site. After 1 and 3 months of implantation, the biosheets were harvested and evaluated histologically. Implantable biosheets were formed with a success rate of 67%. There were no major complications following implantation, including tissue rejection, severe inflammation, or infection. Urinary incontinence was also not observed. Histological evaluation revealed the bladder lumen was almost entirely covered by urothelium after 1 month, with myofibroblast infiltration into the biosheets. After 3 months, the urothelium became multilayered, and mature myocytes and nerve fibers were observed at the implantation site. In conclusion, this study showed that tissue reconstruction using iBTA can be applied to cats, and that biosheets have the potential to be useful in both the structural and functional regeneration of the feline urinary tract.

Porous gelatin microspheres implanted with adipose mesenchymal stromal cells promote angiogenesis via protein kinase B/endothelial nitric oxide synthase signaling pathway in bladder reconstruction

BACKGROUND AIMS

Cell failure and angiogenesis are the key to bladder wall regeneration. Three-dimensional (3D) culture using porous gelatin microspheres (GMs) as a vehicle promotes stem cell proliferation and improves the paracrine capacity of cells. This study aimed to evaluate the therapeutic potential of GMs constructed from adipose-derived mesenchymal stromal cells (ADSCs) (ADSC-GMs) combined with bladder acellular matrix (BAM) in tissue-engineered bladders.

METHODS

Isolation of ADSCs, flow cytometry, scanning electron microscopy and cell counting kit-8, β-galactosidase and enzyme-linked immunosorbent assays were performed in vitro to compare two-dimensional (2D) and 3D cultures. In the in vivo study, male Sprague-Dawley rats were randomly divided into three groups: the BAM replacement alone (BAM) group, ADSCs grown on BAM in replacement (ADSC) group and ADSC-GMs combined with BAM followed by replacement (ADSC-GM) group. Bladder function assessed by urodynamics after 12 weeks of bladder replacement, and the rats were sacrificed at 4 and 12 weeks for further experiments.

RESULTS

The in vitro results showed that GM culture promoted ADSC proliferation, inhibited apoptosis and delayed senescence compared with those in the 2D culture. In addition, ADSC-GMs increased the secretion of the angiogenic factors vascular endothelial growth factor, platelet-derived growth factor-BB, and basal fibroblast growth factor. In vivo experiments revealed that ADSC-GMs adhered to the BAM for longer than ADSCs. Moreover, ADSC-GMs significantly promoted the regeneration of bladder vessels and smooth muscle, thereby facilitating the recovery of bladder function. The expression of phosphorylated protein kinase B (AKT) and phosphorylated endothelial nitric oxide synthase (eNOS) was significantly greater in the ADSC-GMs group compared with the BAM and ADSCs groups.

CONCLUSIONS

ADSC-GMs increased retention of ADSCs on the BAM, thereby promoting the regeneration and functional recovery of the bladder tissue. ADSC-GMs promoted angiogenesis by activating the AKT/eNOS pathway.

Development of Enzymatic-Resistant and Compliant Decellularized Extracellular Matrixes via Aliphatic Chain Modification for Bladder Tissue Engineering

Here, we report the design and development of highly stretchable, compliant, and enzymatic-resistant transiently cross-linked decellularized extracellular matrixes (dECMs) (e.g., porcine small intestine submucosa/dSIS, urinary bladder matrix/dUBM, bovine pericardium/dBP, bovine dermis/dBD, and human dermis/dHD). Specifically, these dECMs were modified with long aliphatic chains (C9, C14, and C18). Upon modification, dECMs became significantly resistant to enzymatic degradation for extended periods, showed increased water contact angle (>20%-90%), and stretched >200% than their control counterparts. Modified dECMs are compliant, undergoing 100% elongation at only 0.3-0.5 MPa of applied tensile stress (∼10%-25% of their control counterparts), similar to the control bladder tissue. Furthermore, modified dECMs remain structurally stable at the physiological temperature with increased storage and loss modulus values but decreased tan δ values compared to their control counterparts. Although modification reduces cell adhesion, the gene expressions in polarized macrophages remain unchanged (e.g., TGFβ, CD163, and CD86), except for the modified bovine pericardium (dBP) where a significant decrease in TNFα gene expression is observed. When implanted in the rat subcutaneous model, modified dECMs degraded relatively slowly and did not cause significant fibrotic tissue formation. The numbers of pro-regenerative macrophages increased to several folds in a later time point of evaluation. Modified dECM also supported the bladder wall regeneration with formations of the urothelium, lamina propria, blood vessels, and muscle bundles and reduced the occurrence of calculi formation by 50% in a rat bladder augmentation model. We anticipate that the enhanced stretchability, compliance, and physiological stability of dECMs indicate their suitability for urologic tissue regeneration.

Construction of Tissue-Engineered Bladder Scaffolds with Composite Biomaterials

Various congenital and acquired urinary system abnormalities can cause structural damage to patients’ bladders. This study aimed to construct and evaluate a novel surgical patch encapsulated with adipose-derived stem cells (ADSCs) for bladder tissue regeneration. The surgical patch consists of multiple biomaterials, including bladder acellular matrix (BAM), collagen type I from rat tail, microparticle emulsion cross-linking polylactic-co-glycolic acid (PLGA)-chitosan (CS) with PLGA-sodium alginate (SA), and growth factors. ADSCs were seeded on the surgical patch. Approximately 50% of the bladder was excised and replaced with a surgical patch. Histological, immunohistochemical and urodynamic analyses were performed at the 2nd, 4th, and 8th weeks after surgery, respectively. The PLGA-CS, PLGA-SA or surgical patch showed no cytotoxicity to ADSCs. PLGA-CS cross-linked with PLGA-SA at a ratio of 5:5 exhibited a loose microporous structure and was chosen as the candidate for ADSC seeding. We conducted bladder repair surgery in rats using the patch, successfully presenting urothelium layers, muscle bundles, and vessel regeneration and replacing 50% of the rat’s natural bladder in vivo. Experiments through qualitative and quantitative evaluation demonstrate the application potential of the composite biomaterials in promoting the repair and reconstruction of bladder tissue.

Bladder Acellular Matrix Prepared by a Self-Designed Perfusion System and Adipose-Derived Stem Cells to Promote Bladder Tissue Regeneration

The bladder patch constructed with the bladder acellular matrix (BAM) and adipose-derived stem cells (ASCs) was incubated with the omentum for bladder reconstruction in a rat model of bladder augmentation cystoplasty. A self-designed perfusion system and five different decellularization protocols were used to prepare the BAM. Finally, an optimal protocol (group C) was screened out by comparing the cell nucleus residue, collagen structure preservation and biologically active components retention of the prepared BAM. ASCs-seeded (BAM-ASCs group) and unseeded BAM (BAM group) were incubated with the omentum for 7 days to promote neovascularization and then perform bladder reconstruction. Hematoxylin and eosin and Masson’s trichrome staining indicated that the bladder patches in the BAM-ASCs group could better regenerate the bladder wall structure compared to the BAM group. Moreover, immunofluorescence analyses demonstrated that the ASCs could promote the regeneration of smooth muscle, neurons and blood vessels, and the physiological function (maximal bladder capacity, max pressure prior to voiding and bladder compliance) restoration in the BAM-ASCs group. The results demonstrated that the self-designed perfusion system could quickly and efficiently prepare the whole bladder scaffold and confirmed that the prepared BAM could be used as the scaffold material for functional bladder tissue engineering applications.

An overview of post transplantation events of decellularized scaffolds

Regenerative medicine and tissue engineering are reasonable techniques for repairing failed tissues and could be a suitable alternative to organ transplantation. One of the most widely used methods for preparing bioscaffolds is the decellularization procedure. Although cell debris and DNA are removed from the decellularized tissues, important compositions of the extracellular matrix including proteins, proteoglycans, and glycoproteins are nearly preserved. Moreover, the obtained scaffolds have a 3-dimensional (3D) structure, appropriate naïve mechanical properties, and good biocompatibility. After transplantation, different types of host cells migrate to the decellularized tissues. Histological and immunohistochemical assessment of the different bioscaffolds after implantation reveals the migration of parenchymal cells, angiogenesis, as well as the invasion of inflammatory and giant foreign cells. In this review, the events after transplantation including angiogenesis, scaffold degradation, and the presence of immune and tissue-specific progenitor cells in the decellularized scaffolds in various hosts, are discussed.

Application of biomaterials and tissue engineering in bladder regeneration

The primary functions of the bladder are storing urine under low and stable pressure and micturition. Various forms of trauma, tumors, and iatrogenic injuries can cause the loss of or reduce bladder function or capacity. If such damage is not treated in time, it will eventually lead to kidney damage and can even be life-threatening in severe cases. The emergence of tissue engineering technology has led to the development of more possibilities for bladder repair and reconstruction, in which the selection of scaffolds is crucial. In recent years, a growing number of tissue-engineered bladder scaffolds have been constructed. Therefore, this paper will discuss the development of tissue-engineered bladder scaffolds and will further analyze the limitations of and challenges encountered in bladder reconstruction.

Tissue engineering in reconstructive urology-The current status and critical insights to set future directions-critical review

Advanced techniques of reconstructive urology are gradually reaching their limits in terms of their ability to restore urinary tract function and patients' quality of life. A tissue engineering-based approach to urinary tract reconstruction, utilizing cells and biomaterials, offers an opportunity to overcome current limitations. Although tissue engineering studies have been heralding the imminent introduction of this method into clinics for over a decade, tissue engineering is only marginally applied. In this review, we discuss the role of tissue engineering in reconstructive urology and try to answer the question of why such a promising technology has not proven its clinical usability so far.

The Significance of Biomechanics and Scaffold Structure for Bladder Tissue Engineering

Current approaches for bladder reconstruction surgery are associated with many morbidities. Tissue engineering is considered an ideal approach to create constructs capable of restoring the function of the bladder wall. However, many constructs to date have failed to create a sufficient improvement in bladder capacity due to insufficient neobladder compliance. This review evaluates the biomechanical properties of the bladder wall and how the current reconstructive materials aim to meet this need. To date, limited data from mechanical testing and tissue anisotropy make it challenging to reach a consensus on the native properties of the bladder wall. Many of the materials whose mechanical properties have been quantified do not fall within the range of mechanical properties measured for native bladder wall tissue. Many promising new materials have yet to be mechanically quantified, which makes it difficult to ascertain their likely effectiveness. The impact of scaffold structures and the long-term effect of implanting these materials on their inherent mechanical properties are areas yet to be widely investigated that could provide important insight into the likely longevity of the neobladder construct. In conclusion, there are many opportunities for further investigation into novel materials for bladder reconstruction. Currently, the field would benefit from a consensus on the target values of key mechanical parameters for bladder wall scaffolds.

Translation of mechanical strain to a scalable biomanufacturing process for acellular matrix production from full thickness porcine bladders

Bladder acellular matrix has promising applications in urological and other reconstructive surgery as it represents a naturally compliant, non-immunogenic and highly tissue-integrative material. As the bladder fills and distends, the loosely-coiled bundles of collagen fibres in the wall become extended and orientate parallel to the lumen, resulting in a physical thinning of the muscular wall. This accommodating property can be exploited to achieve complete decellularisation of the full-thickness bladder wall by immersing the distended bladder through a series of hypotonic buffers, detergents and nucleases, but the process is empirical, idiosyncratic and does not lend itself to manufacturing scale up. In this study we have taken a mechanical engineering approach to determine the relationship between porcine bladder size and capacity, to define the biaxial deformation state of the tissue during decellularisation and to apply these principles to the design and testing of a scalable novel laser-printed flat-bed apparatus in order to achieve reproducible and full-thickness bladder tissue decellularisation. We demonstrate how the procedure can be applied reproducibly to fresh, frozen or twice-frozen bladders to render8×8 cm²patches of DNA-free acellular matrix suitable for surgical applications.

Tissue engineering to treat pelvic organ prolapse

Pelvic organ prolapse (POP) is a frequent chronic illness, which seriously affects women's living quality. In recent years, tissue engineering has made superior progress in POP treatment, and biological scaffolds have received considerable attention. Nevertheless, pelvic floor reconstruction still faces severe challenges, including the construction of ideal scaffolds, the selection of optimal seed cells, and growth factors. This paper summarizes the recent progress of pelvic floor reconstruction in tissue engineering, and discusses the problems that need to be further considered and solved to provide references for the further development of this field.

Bi-layer silk fibroin skeleton and bladder acellular matrix hydrogel encapsulating adipose-derived stem cells for bladder reconstruction

A scaffold, constructed from a bi-layer silk fibroin skeleton (BSFS) and a bladder acellular matrix hydrogel (BAMH) encapsulated with adipose-derived stem cells (ASCs), was developed for bladder augmentation in a rat model. The BSFS, prepared from silk fibroin (SF), had good mechanical properties that allowed it to maintain the scaffold shape and be used for stitching. The prepared BAM was digested by pepsin and the pH was adjusted to harvest the BAMH that provided an extracellular environment for the ASCs. The constructed BSFS-BAMH-ASCs and BSFS-BAMH scaffolds were wrapped in the omentum to promote neovascularization and then used for bladder augmentation; at the same time, a cystotomy was used as the condition for the control group. Histological staining and immunohistochemical analysis confirmed that the omentum incubation could promote scaffold vascularization. Hematoxylin and eosin and Masson's trichrome staining indicated that the BSFS-BAMH-ASCs scaffold regenerated the bladder wall structure. In addition, immunofluorescence analyses confirmed that the ASCs could promote the regeneration of smooth muscle, neurons and blood vessels and the restoration of physiological function. These results demonstrated that the BSFS-BAMH-ASCs may be a promising scaffold for promoting bladder wall regeneration and the restoration of physiological function of the bladder in a rat bladder augmentation model.

Urinary bladder augmentation with acellular biologic scaffold-A preclinical study in a large animal model

Current strategies in urinary bladder augmentation include use of gastrointestinal segments, however, the technique is associated with inevitable complications. An acellular biologic scaffold seems to be a promising option for urinary bladder augmentation. The aim of this study was to evaluate the utility of bladder acellular matrix (BAM) for reconstruction of clinically significant large urinary bladder wall defects in a long-term porcine model. Urinary bladders were harvested from 10 pig donors. Biological scaffolds were prepared by chemically removing all cellular components from urinary bladder tissue. A total of 10 female pigs underwent hemicystectomy and subsequent bladder reconstruction with BAM. The follow-up study was 6 months. Reconstructed bladders were subjected to radiological, macroscopic, histological, immunohistochemical, and molecular evaluations. Six out of ten animals survived the 6-month follow-up period. Four pigs died during observation due to mechanical failure of the scaffold, anastomotic dehiscence between the scaffold and native bladder tissue, or occluded catheter. Tissue engineered bladder function was normal without any signs of postvoid residual urine in the bladder or upper urinary tracts. Macroscopically, graft shrinkage was observed. Urothelium completely covered the luminal surface of the graft. Smooth muscle regeneration was observed mainly in the peripheral graft region and gradually decreased toward the center of the graft. Expression of urothelial, smooth muscle, blood vessel, and nerve markers were lower in the reconstructed bladder wall compared to the native bladder. BAM seems to be a promising biomaterial for reconstruction of large urinary bladder wall defects. Further research on cell-seeded BAM to enhance urinary bladder regeneration is required.

Research progress in decellularized extracellular matrix-derived hydrogels

Decellularized extracellular matrix (dECM) is widely used in regenerative medicine as a scaffold material due to its unique biological activity and good biocompatibility. Hydrogel is a three-dimensional network structure polymer with high water content and high swelling that can simulate the water environment of human tissues, has good biocompatibility, and can exchange nutrients, oxygen, and waste with cells. At present, hydrogel is the ideal biological material for tissue engineering. In recent years, rapid development of the hydrogel theory and technology and progress in the use of dECM to form hydrogels have attracted considerable attention to dECM hydrogels as an innovative method for tissue engineering and regenerative medicine. This article introduces the classification of hydrogels, and focuses on the history and formation of dECM hydrogels, the source of dECM, the application of dECM hydrogels in tissue engineering and the commercial application of dECM materials.

The development of marine biomaterial derived from decellularized squid mantle for potential application as tissue engineered urinary conduit

Tissue engineering is focusing research effort on search for new biomaterials that might be applied to create artificial urinary conduit. Nevertheless, the demanding biomechanical characteristics necessary for proper conduit function is difficult to be replicated. In this study, we are introducing novel marine biomaterial obtained by decellularization of squid mantle derived from Loligo vulgaris. Squid mantles underwent decellularization according to developed dynamic flow two-staged procedure. Efficacy of the method was confirmed by computational dynamic flow analysis. Subsequently Decellularized Squid Mantle (DSM) underwent extensive histological analysis and mechanical evaluation. Based on gained biomechanical data the computational modelling using finite element method was utilized to simulate behavior of DSM used as a urinary conduit. Taking into account potential application in reconstructive urology, the DSM was then evaluated as a scaffold for urothelial and smooth muscle cells derived from porcine urinary bladder. Conducted analysis showed that DSM created favorable environment for cells growth. In addition, due to polarized structure and natural external polysaccharide layer, it protected seeded cells from urine.

Extracellular matrix-derived biomaterials in engineering cell function

Extracellular matrix (ECM) derived components are emerging sources for the engineering of biomaterials that are capable of inducing desirable cell-specific responses. This review explores the use of biomaterials derived from naturally occurring ECM proteins and their derivatives in approaches that aim to regulate cell function. Biomaterials addressed are grouped into six categories: purified single ECM proteins, combinations of purified ECM proteins, cell-derived ECM, tissue-derived ECM, diseased and modified ECM, and ECM-polymer coupled biomaterials. Purified ECM proteins serve as a material coating for enhanced cell adhesion and biocompatibility. Cell-derived and tissue-derived ECM, generated by cell isolation and decellularization technologies, can capture the native state of the ECM environment and guide cell migration and alignment patterns as well as stem cell differentiation. We focus primarily on recent advances in the fields of soft tissue, cardiac, and dermal repair, and explore the utilization of ECM proteins as biomaterials to engineer cell responses.

Tissue engineered ultra-thin descemet stripping corneal endothelial layers using porcine cornea and stem cells

Due to their very poor proliferative capacity, the dysfunction of corneal endothelial cells can sometimes lead to incurable eye diseases that require corneal transplantation. Although many studies have been performed to reconstruct corneal endothelial cells, corneal transplantation is still considered to be the established approach. In this study, we developed bio-engineered Descemet stripping endothelial (DSE) layers, using porcine cornea and induced pluripotent stem cell (iPSC)-derived corneal endothelial cells (iCECs). First, we optimized a protocol to prepare an ultra-thin and decellularized Descemet stripping (DS) scaffold from porcine cornea. Our DS layers show over 90% transparency compared to the control. Porcine-derived cells and xenogenic antigens disappeared, whereas the collagen matrix remained in the graft. Next, corneal endothelial cell lines or iCECs were seeded on the decellularized DS graft and cultured for 7 days. The drying method reduced graft rolling and edema, and increased transparency during culture. The reseeded cells were evenly distributed over the graft, and most of the cells survived. Although future clinical studies are warranted, engineered DSE tissues using xenogenic tissues and stem cells will be useful tools for the treatment of incurable corneal diseases.

Decellularized adipose matrix provides an inductive microenvironment for stem cells in tissue regeneration

Stem cells play a key role in tissue regeneration due to their self-renewal and multidirectional differentiation, which are continuously regulated by signals from the extracellular matrix (ECM) microenvironment. Therefore, the unique biological and physical characteristics of the ECM are important determinants of stem cell behavior. Although the acellular ECM of specific tissues and organs (such as the skin, heart, cartilage, and lung) can mimic the natural microenvironment required for stem cell differentiation, the lack of donor sources restricts their development. With the rapid development of adipose tissue engineering, decellularized adipose matrix (DAM) has attracted much attention due to its wide range of sources and good regeneration capacity. Protocols for DAM preparation involve various physical, chemical, and biological methods. Different combinations of these methods may have different impacts on the structure and composition of DAM, which in turn interfere with the growth and differentiation of stem cells. This is a narrative review about DAM. We summarize the methods for decellularizing and sterilizing adipose tissue, and the impact of these methods on the biological and physical properties of DAM. In addition, we also analyze the application of different forms of DAM with or without stem cells in tissue regeneration (such as adipose tissue), repair (such as wounds, cartilage, bone, and nerves), in vitro bionic systems, clinical trials, and other disease research.

Human adipose-derived mesenchymal stem cells accelerate decellularized neobladder regeneration

Decellularized natural bladder matrices (neobladders) represent an exciting means to regenerate the bladder following bladder cancer-associated cystectomy. In this study, we compare the evolution of decellularized matrices with recellularized matrices by seeding it with human adipose-derived mesenchymal stem cells (ADSC) after implantation following partial cystectomy in rats. We discovered significant anatomical differences since 10 days after neobladder implantation with the ADSC-containing matrices promoting a significant recovery of mature p63- and cytokeratin 7-positive urothelium. We also discovered significantly induced expression of the vimentin mesoderm marker in the submucosal layer in ADSC-seeded matrices. Interestingly, we found a higher expression of smooth muscle actin in transversal and longitudinal smooth muscle layers with ADSC-seeded matrices. Furthermore, ADSC also showed increased vascularization and nerve innervation of the neobladder as determined by the distribution of CD31 and S100β reactivity, respectively. We believe that ADSC and their paracrine-acting pro-regenerative secretome within decellularized matrices represent an efficient bladder substitution strategy; however, we require a fuller understanding of the mechanisms involved before clinical studies can begin.

Use of the extracellular matrix from the porcine esophagus as a graft for bladder enlargement

INTRODUCTION

Some patients with diseases that involve increased bladder pressure or low-capacity bladders may need bladder enlargement surgery. In current techniques for bladder enlargement, autologous tissue such as small intestine or colon tissue is used to perform cystoplasties, which is far from ideal for these patients. In search of biomaterials with appropriate regeneration and safety profiles, tissue engineering has resulted in preclinical studies with acellular matrices in animal models that have yielded positive preliminary results with respect to the urothelial cell and smooth muscle repopulation; these studies have primarily been performed with matrices originating from the bladder or intestinal submucosa.

OBJECTIVE

The aim of the study was to assess an extracellular matrix device derived from the porcine esophagus for augmentation cystoplasty in an animal model.

STUDY DESIGN

Seven male Wistar rats weighing 357-390 g were subjected to augmentation cystoplasty with a circular segment of the acellular matrix from the porcine esophagus. Daily postoperative follow-up was performed with evaluation of changes in body weight, behavior, and wound status.

RESULTS

During follow-up, there were no complications associated with the process. Three specimens were sacrificed at day 30, and three, at day 60. Necropsy was performed, with a description of the macroscopic findings and a morphological study. Epithelialization was observed, with different stages of mucosal development in all specimens analyzed. Repopulation of smooth muscle cells, mixed inflammatory infiltrate, and vascular neoformation were identified in the matrices.

DISCUSSION

The urothelium and fibers of the smooth muscle were observed inside the implanted matrix. Additional investigations in larger animal models that allow urodynamic evaluation of the bladder with the matrix implanted are needed. However, to compare the results of this study model with those reported in the literature, a matrix derived from an organ different from the bladder was used because it could prevent the use of an intestinal segment in augmentation cystoplasty.

CONCLUSION

The acellular porcine esophagus matrix offers positive results regarding the repopulation of the urothelium and smooth muscle when used in augmentation cystoplasty in a murine model.

Tissue-Engineered Grafts from Human Decellularized Extracellular Matrices: A Systematic Review and Future Perspectives

Tissue engineering and regenerative medicine involve many different artificial and biologic materials, frequently integrated in composite scaffolds, which can be repopulated with various cell types. One of the most promising scaffolds is decellularized allogeneic extracellular matrix (ECM) then recellularized by autologous or stem cells, in order to develop fully personalized clinical approaches. Decellularization protocols have to efficiently remove immunogenic cellular materials, maintaining the nonimmunogenic ECM, which is endowed with specific inductive/differentiating actions due to its architecture and bioactive factors. In the present paper, we review the available literature about the development of grafts from decellularized human tissues/organs. Human tissues may be obtained not only from surgery but also from cadavers, suggesting possible development of Human Tissue BioBanks from body donation programs. Many human tissues/organs have been decellularized for tissue engineering purposes, such as cartilage, bone, skeletal muscle, tendons, adipose tissue, heart, vessels, lung, dental pulp, intestine, liver, pancreas, kidney, gonads, uterus, childbirth products, cornea, and peripheral nerves. In vitro recellularizations have been reported with various cell types and procedures (seeding, injection, and perfusion). Conversely, studies about in vivo behaviour are poorly represented. Actually, the future challenge will be the development of human grafts to be implanted fully restored in all their structural/functional aspects.

Understanding the role of mesenchymal stem cells in urinary bladder regeneration-a preclinical study on a porcine model

BACKGROUND

The tissue engineering of urinary bladder advances rapidly reflecting clinical need for a new kind of therapeutic solution for patients requiring urinary bladder replacement. Majority of the bladder augmentation studies have been performed in small rodent or rabbit models. Insufficient number of studies examining regenerative capacity of tissue-engineered graft in urinary bladder augmentation in a large animal model does not allow for successful translation of this technology to the clinical setting. The aim of this study was to evaluate the role of adipose-derived stem cells (ADSCs) in regeneration of clinically significant urinary bladder wall defect in a large animal model.

METHODS

ADSCs isolated from a superficial abdominal Camper's fascia were labeled with PKH-26 tracking dye and subsequently seeded into bladder acellular matrix (BAM) grafts. Pigs underwent hemicystectomy followed by augmentation cystoplasty with BAM only (n = 10) or BAM seeded with autologous ADSCs (n = 10). Reconstructed bladders were subjected to macroscopic, histological, immunofluoresence, molecular, and radiological evaluations at 3 months post-augmentation.

RESULTS

Sixteen animals (n = 8 for each group) survived the 3-month follow-up without serious complications. Tissue-engineered bladder function was normal without any signs of post-voiding urine residual in bladders and in the upper urinary tracts. ADSCs enhanced regeneration of tissue-engineered urinary bladder but the process was incomplete in the central graft region. Only a small percentage of implanted ADSCs survived and differentiated into smooth muscle and endothelial cells.

CONCLUSIONS

The data demonstrate that ADSCs support regeneration of large defects of the urinary bladder wall but the process is incomplete in the central graft region. Stem cells enhance urinary bladder regeneration indirectly through paracrine effect.

Evaluation of the bioactivity about anti-sca-1/basic fibroblast growth factor-urinary bladder matrix scaffold for pelvic reconstruction

Introduction and hypothesis: Pelvic support structure injury is the major cause of pelvic organ prolapse. At present, polypropylene-based filler material has been suggested as a common method to treat pelvic organ prolapse. However, it cannot functionally rehabilitate the pelvic support structure. In addition to its poor long-term efficiency, the urinary bladder matrix was the most suitable biological scaffold material for pelvic floor repair. Here, we hypothesize that anti-sca-1 monoclonal antibody and basic fibroblast growth factor were cross-linked to urinary bladder matrix to construct a two-factor bioscaffold for pelvic reconstruction.

METHODS

Through a bispecific cross-linking reagent, sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-smcc) immobilized anti-sca-1 and basic fibroblast growth factor to urinary bladder matrix. Then scanning electron microscope and plate reader were used to detect whether the anti-sca-1/basic fibroblast growth factor-urinary bladder matrix scaffold was built successfully. After that, the capacity of enriching sca-1 positive cells was measured both in vitro and in vivo. In addition, we evaluated the differentiation capacity and biocompatibility of the scaffold. Finally, western blotting was used to detect the level of fibulin-5 protein.

RESULTS

The scanning electron microscope and plate reader revealed that the double-factor biological scaffold was built successfully. The scaffold could significantly enrich a large number of sca-1 positive cells both in vitro and in vivo, and obviously accelerate cells and differentiate functional tissue with good biocompatibility. Moreover, the western blotting showed that the scaffold could improve the expression of fibulin-5 protein.

CONCLUSION

The anti-sca-1/basic fibroblast growth factor-urinary bladder matrix scaffold revealed good biological properties and might serve as an ideal scaffold for pelvic reconstruction.

Use of an acellular collagen-elastin matrix to support bladder regeneration in a porcine model of peritoneocystoplasty

Introduction

Bladder reconstruction without using the intestine remains a challenge to this day despite the development of new biomaterials and cell cultures. Human bladder engineering is merely anecdotic, and mostly in vitro and animal studies have been conducted.

Material and methods

In our study using a porcine model, we performed a bladder augmentation using an autologous parietal peritoneum graft (peritoneocystoplasty) and determined whether the attachment of an acellular collagen-elastin matrix (Group 1) or lack of (Group 2) had better histologic and functional results. Thus far, peritoneocystoplasty has rarely been performed or combined with a biomaterial.

Results

After 6 weeks, we observed different degrees of retraction of the new bladder wall in both groups, although the retraction was lower and the histological analysis showed more signs of regeneration (neoangiogenesis and less fibrosis) in Group 1 than when compared with Group 2. No transitional cells were found in the new bladder wall in any of the groups, and no differences were observed in the functional test results.

Conclusions

Performing a peritoneocystoplasty is an easy and safe procedure. The data supports the benefit of an acellular collagen–elastin matrix to reinforce bladder regeneration. However, in our study we observed too much retraction of the new wall and the histologic results were not acceptable to consider it an appropriate cystoplasty technique.

Current status of tissue engineering applied to bladder reconstruction in humans

CONTEXT AND OBJECTIVE

Bladder reconstruction is performed to replace or expand the bladder. The intestine is used in standard clinical practice for tissue in this procedure. The complications of bladder reconstruction range from those of intestinal resection to those resulting from the continuous contact of urine with tissue not prepared for this contact. In this article, we describe and classify the various biomaterials and cell cultures used in bladder tissue engineering and reviews the studies performed with humans.

ACQUISITION OF EVIDENCE

We conducted a review of literature published in the PubMed database between 1950 and 2017, following the principles of the PRISM declaration.

SYNTHESIS OF THE EVIDENCE

Numerous in vitro and animal model studies have been conducted, but only 18 experiments have been performed with humans, with a total of 169 patients. The current evidence suggests that an acellular matrix, a synthetic polymer with urothelial and autologous smooth muscle cells attached in vitro or stem cells would be the most practical approach for experimental bladder reconstruction.

CONCLUSIONS

Bladder replacement or expansion without using intestinal tissue is still a challenge, despite progress in the manufacture of biomaterials and the development of cell therapy. Well-designed studies with large numbers of patients and long follow-up times are needed to establish an effective clinical translation and standardisation of the check-up functional tests.

Urological technology: where will we be in 20 years' time?

Since prehistoric times, our understanding of urology has rapidly expanded. Whilst primitive urologists began by using urine as a therapeutic substance, modern urologists may find themselves removing a kidney remotely by driving a robotic arm, with seven degrees of movement, while using image overlay-augmented reality. This review provides an insight into the potential status of urological technology in 20 years' time, assessed through an analysis of developments in imaging, diagnostics, robotics and further technologies. A particular emphasis is given to the promising fields of minimally invasive techniques, nanotechnology and tissue engineering, which likely hold the key to a new era for urology.

Stem cell in urology-are we at the cusp of a new era?

Stem cell therapy can potentially disrupt conventional medicine as we practice it today. Stem cells can self-renew and differentiate and by this, repair and in certain conditions regenerate damaged tissue. In the past two decades, there has been significant research into its value in several chronic urological conditions for which conventional therapy is unsatisfactory. Stem cell therapy has been tried on animal models of bladder dysfunction, stress urinary incontinence (SUI), erectile dysfunction and urethral injury and certain preclinical studies have had very encouraging results. Yet despite this explosion of knowledge about the nature and value of stem cells, translation of research into the clinical domain has been slow. In addition, lack of regulation of stem cell therapy has resulted in indiscriminate, unscientific administration of stem cell therapy to patients. This review looks into the advances in the use of stem cells in urological practice, the recent regulatory guidelines that have been introduced and what the future holds for this exciting branch.

Bladder regeneration in a canine model using a bladder acellular matrix loaded with a collagen-binding bFGF

Bladder reconstruction remains challenging for urological surgery due to lack of suitable regenerative scaffolds. In a previous study, we had used a collagen-binding basic fibroblast growth factor (CBD-bFGF) to bind bFGF to the collagen scaffold, which could promote bladder regeneration in rats. However, the limited graft size in rodent models cannot provide enough evidence to demonstrate the repair capabilities of this method for severely damaged bladders in humans or large animals. In this study, the CBD-bFGF was used to activate a bladder acellular matrix (BAM) scaffold, and the CBD-bFGF/BAM functional scaffold was assessed in a canine model with a large segment defect (half of the entire bladder was resected). The results demonstrated that the functional biomaterials could promote bladder smooth muscle, vascular, and nerve regeneration and improve the function of neobladders. Thus, the CBD-bFGF/BAM functional scaffold may be a promising biomaterial for bladder reconstruction.

The enhanced angiogenesis effect of VEGF-silk fibroin nanospheres-BAMG scaffold composited with adipose derived stem cells in a rabbit model

We report a study to determine whether a vascular endothelial growth factor (VEGF)-silk fibroin (SF) nanospheres-bladder acellular matrix graft (BAMG) scaffold composited with adipose derived stem cells (ADSCs) could enhance angiogenesis in bladder regeneration in rabbits. Rabbit ADSCs were isolated and identified by flow cytometry. The morphology and release behaviour of VEGF-SF nanospheres were detected. After the composite scaffolds were successfully used in bladder reconstruction, the bladder capacity, H&E staining and immunohistochemical staining were studied at different time points. ADSCs exerts high expression rates of CD29, CD90, and CD44, accompanied with low expression rates of CD34 and CD45. SF nanospheres with diameters of 200–1000 nm were prepared to load VEGF, and they contributed to maintain the release of VEGF. The reconstructed bladder with VEGF-SF nanospheres-BAMG plus ADSCs had more regular smooth muscle tissue and blood vessels. Moreover, instead of differentiating into epithelial or vascular endothelial cells, ADSCs may be more likely to provide additional cytokines to enhance angiogenesis in the bladder regeneration process. The tissue engineered bladder constructed by BAMG modified by VEGF-SF nanospheres possessed high bio-compatibility and an enhanced angiogenesis effect, and could be used as an ideal biological material to repair bladder defects after being composited with ADSCs.

The adipose derived stem cells (ADSCs) was composited with vascular endothelial growth factor (VEGF)-silk fibroin (SF) nanospheres-bladder acellular matrix graft (BAMG) scaffold to repair bladder defect in rabbits.

Urinary Tissue Engineering: Challenges and Opportunities

INTRODUCTION

In this review, we discuss major advancements and common challenges in constructing and regenerating a neo-urinary conduit (NUC). First, we focus on the need for regenerating the urothelium, the hallmark the urine barrier, unique to urinary tissues. Second, we focus on clinically feasible scaffolds based on decellularized matrices and molded collagen that are currently of great research interest.

AIM

To discuss the major advancements in constructing a tissue-engineered NUC (TE-NUC) and the challenges involved in their successful clinical translation.

METHODS

A comprehensive search of peer-reviewed literature from PubMed and Google Scholar on subjects related to urothelium regeneration, decellularized tissue matrices, and collagen scaffolds was conducted.

MAIN OUTCOME MEASURE

We evaluated the main biological and mechanical functions of urinary tissues, the need for TE implants to create a urinary diversion, the reasons for their failures in clinical settings, and the applications of decellularized tissue matrices and collagen-based molded scaffolds in their regeneration.

RESULTS

It is necessary to create a urine barrier that prevents urine leakage into the stroma that can cause failure of the graft. Despite the regeneration potential of the urothelium, the limited supply of healthy urothelial cells in patients with bladder cancer remains a major challenge. In this context, alternative strategies, such as transdifferentiation of cells into urothelium or engineered scaffolds based on decellularized tissues and molded collagen with robust urine barrier properties, are active areas of research.

CONCLUSION

There is an immediate need for developing a functional TE-NUC that can improve the quality of life of patients with bladder cancer. It is possible to achieve a TE-NUC by bioengineering an implant that has appropriate biological and mechanical properties to store and transport urine. We anticipate that future advancements in urothelium regeneration and material design will lead us closer to successful neo-urinary tissue constructs. Singh A, Bivalacqua TJ, Sopko N. Urinary Tissue Engineering: Challenges and Opportunities. Sex Med Rev 2018;6:35-44.

Layer-dependent role of collagen recruitment during loading of the rat bladder wall

In this work, we re-evaluated long-standing conjectures as to the source of the exceptionally large compliance of the bladder wall. Whereas these conjectures were based on indirect measures of loading mechanisms, in this work we take advantage of advances in bioimaging to directly assess collagen fibers and wall architecture during biaxial loading. A custom biaxial mechanical testing system compatible with multiphoton microscopy was used to directly measure the layer-dependent collagen fiber recruitment in bladder tissue from 9 male Fischer rats (4 adult and 5 aged). As for other soft tissues, the bladder loading curve was exponential in shape and could be divided into toe, transition and high stress regimes. The relationship between collagen recruitment and loading curves was evaluated in the context of the inner (lamina propria) and outer (detrusor smooth muscle) layers. The large extensibility of the bladder was found to be possible due to folds in the wall (rugae) that provide a mechanism for low resistance flattening without any discernible recruitment of collagen fibers throughout the toe regime. For more extensible bladders, as the loading extended into the transition regime, a gradual coordinated recruitment of collagen fibers between the lamina propria layer and detrusor smooth muscle layer was found. A second important finding was that wall extensibility could be lost by premature recruitment of collagen in the outer wall that cut short the toe region. This change was correlated with age. This work provides, for the first time, a mechanistic understanding of the role of collagen recruitment in determining bladder extensibility and capacitance.

Tissue engineered extracellular matrices (ECMs) in urology: Evolution and future directions

Autologous gastrointestinal tissue has remained the gold-standard reconstructive biomaterial in urology for >100 years. Mucus-secreting epithelium is associated with lifelong metabolic and neuromechanical complications when implanted into the urinary tract. Therefore, the availability of biocompatible tissue-engineered biomaterials such as extracellular matrix (ECM) scaffolds may provide an attractive alternative for urologists. ECMs are decellularised, biodegradable membranes that have shown promise for repairing defective urinary tract segments in vitro and in vivo by inducing a host-derived tissue remodelling response after implantation. In urology, porcine small intestinal submucosa (SIS) and porcine urinary bladder matrix (UBM) are commonly selected as ECMs for tissue regeneration. Both ECMs support ingrowth of native tissue and differentiation of multi-layered urothelial and smooth muscle cells layers while providing mechanical support in vivo. In their native acellular state, ECM scaffolds can repair small urinary tract defects. Larger urinary tract segments can be repaired when ECMs are manipulated by seeding them with various cell types prior to in vivo implantation. In the present review, we evaluate and summarise the clinical potential of tissue engineered ECMs in reconstructive urology with emphasis on their long-term outcomes in urological clinical trials.

Whyever bladder tissue engineering clinical applications still remain unusual even though many intriguing technological advances have been reached?

To prevent problematic outcomes of bowel-based bladder reconstructive surgery, such as prosthetic tumors and systemic metabolic complications, research works, to either regenerate and strengthen failing organ or build organ replacement biosubstitute, have been turned, from 90s of the last century, to both regenerative medicine and tissue engineering.Various types of acellular matrices, naturally-derived materials, synthetic polymers have been used for either "unseeded" (cell free) or autologous "cell seeded" tissue engineering scaffolds. Different categories of cell sources - from autologous differentiated urothelial and smooth muscle cells to natural or laboratory procedure-derived stem cells - have been taken into consideration to reach the construction of suitable "cell seeded" templates. Current clinically validated bladder tissue engineering approaches essentially consist of augmentation cystoplasty in patients suffering from poorly compliant neuropathic bladder. No clinical applications of wholly tissue engineered neobladder have been carried out to radical-reconstructive surgical treatment of bladder malignancies or chronic inflammation-due vesical coarctation. Reliable reasons why bladder tissue engineering clinical applications so far remain unusual, particularly imply the risk of graft ischemia, hence its both fibrous contraction and even worse perforation. Therefore, the achievement of graft vascular network (vasculogenesis) could allow, together with the promotion of host surrounding vessel sprouting (angiogenesis), an effective graft blood supply, so avoiding the ischemia-related serious complications.

Biomaterial Scaffolds for Reproductive Tissue Engineering

The reproductive system usually involves gamete producing gonads, a series of specialized ducts, accessory glands and the external genitalia. Despite there are many traditional methods such as hormonal and surgical approaches, at present no effective treatments exist to help patients suffering from serious diseases of reproductive system, including congenital and acquired abnormalities, malignant tumor, traumatic, infectious etiologies, inflammation and iatrogenic injuries. Tissue engineering holds promise for reproductive medicine through the development of biological alternative. Till now, a diverse range of biomaterials have been utilized as suitable substrates to match both the mechanical and biological context of reproductive tissues. The current review will focus mainly on the applications of biomaterial scaffolds and their major achievements in each region of reproductive systems.

Tissue-engineering acellular scaffolds-The significant influence of physical and procedural decellularization factors

The importance of decellularized medical products has significantly increased during the last years. In this paper, we evaluated the effects of selected physical and procedural decellularization (DC) factors with the aim to systematically assess their influence on DC results. 72 porcine aortic walls (AW) were divided into three groups and exposed to a DC solution for 4 h and 8 h, either continuously or in repeated cycles. The AW were rocked (90bpm), whirled (10 l/min), sonicated (120W, 45 kHz) or exposed to a combination of these treatments, followed by 10 washing cycles. Defining successful DC as removal of nuclei while keeping an intact extracellular matrix (ECM), we equalized the efficiency to the penetration depth (PD), obtained by DAPI fluorescence and H&E staining. Additionally, we performed scanning electron microscopy (SEM), Pentachrome and Picrosirius-Red staining. Results showed that significantly higher DC depths are achieved on outer compared to inner surfaces (61 ± 7%; p < 0.001). Furthermore, the PD showed a high time dependency for all samples. Compared to continuous rocking, we achieved a significant increase in the DC efficiency through cyclic treatments ( ∼ 43%), whirling ( ∼ 19%) and sonication ( ∼ 49%). The combined treatment supported these results. In all procedures, a skeletonized but intact Collagen fibrous network was obtained as confirmed by SEM analysis. In conclusion, we systematically identified essential factors to significantly enhance DC procedures. We highly recommend considering these factors in future DC protocols. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 153-162, 2018.

The histocompatibility research of hair follicle stem cells with bladder acellular matrix

BACKGROUND

Hair follicle stem cells (HFSCs) were reported to have multidirectional differentiation ability and could be differentiated into melanocytes, keratin cells, smooth muscle cells, and neurons. However, the functionality of HFSCs in bladder tissue regeneration is unknown.

METHODS

This study was conducted to build HFSCs vs bladder acellular matrix (BAM) complexes (HFSCs-BAM complexes) in vitro and evaluated whether HFSCs have well biocompatibility with BAM. HFSCs were separated from SD rats. BAM scaffold was prepared from the submucosa of rabbit bladder tissue. Afterwards, HFSCs were inoculated on BAM.

RESULTS

HFSCs-BAM complexes grew rapidly through inverted microscope observation. Cell growth curve showed the proliferation was in stagnate phase at 7th and 8th day. Cytotoxicity assay showed the toxicity grading of BAM was 0 or 1. Scanning electron microscopy, HE staining, and masson staining showed that cells have germinated on the surface of scaffold.

CONCLUSION

The results provide evidence that HFSCs-BAM complexes have well biocompatibility and accumulate important experimental basis for clinical applying of tissue engineering bladder.

In vitro culture of rat hair follicle stem cells on rabbit bladder acellular matrix

Background

The aim of this work was to create a xenogeneic cell scaffold complex with rabbit bladder acellular matrix and rat hair follicle stem cells, to study the feasibility of construct tissue engineer bladder through biocompatibility of hair follicle stem cells and heterogeneous bladder acellular matrix.

Material and Methods

New Zealand rabbit bladder acellular matrix was prepared. Scanning electron microscope and Masson staining were used to analyse the acellular material. Two-steps precipitation method was used to place the third generation of hair follicle stem cells onto the surface of the bladder acellular matrix. The in vitro cell growth on the scaffold complex was regularly monitored through an inverted microscope. Cell growth curve was established and histological examination and scanning electron microscopic were used to analyse the progresses of the cell growth on the matrix material.

Results

The prepared bladder acellular matrix was white, translucent and membranous. It possessed a fibrous network and collagen structure without any significant cell residues as displayed by the scanning electron microscope, and Masson staining. After 48 h of culture, observation by inverted microscope showed that the hair follicle stem cells grew well around the bladder acellular matrix. After 1 week of culture, scanning electron microscopy showed that the hair follicle stem cells spread and adhered on the surface of the scaffold.

Conclusions

The in vitro culture of rat hair follicle stem cells and the rabbit bladder acellular matrix possessed a good biocompatibility, which provides a good experiment support for hair follicle stem cells to repair the bladder defects disease.

Future Perspectives in Bladder Tissue Engineering

Substantial clinical need persists for improved autologous tissues to augment or replace the urinary bladder and research has begun to address this using tissue engineering techniques. The implantation of both tissue scaffolds which allow for native bladder tissue ingrowth and autologous bladder grafts created from in vitro cellularization of such scaffolds have been tested clinically; however, successful outcomes in both scenarios have been challenged by insufficient vascularity resulting from large graft sizes, which subsequently limits tissue ingrowth and leads to central graft ischemia. Consequently, recent research has focused on developing better methods to produce scaffolds with increased tissue ingrowth and vascularity. This review provides an update on bladder tissue engineering and outlines the challenges that remain to clinical implementation.