Changing concepts of bladder regeneration

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

A Lipid-Nanosphere-Small MyoD Activating RNA-Bladder Acellular Matrix Graft Scaffold [NP(saMyoD)/BAMG] Facilitates Rat Injured Bladder Muscle Repair and Regeneration [NP(saMyoD)/BAMG]

Background

Bladder tissue engineering is an excellent alternative to conventional gastrointestinal bladder enlargement in the treatment of various acquired and congenital bladder abnormalities. We constructed a nanosphere-small MyoD activating RNA-bladder acellular matrix graft scaffold NP(saMyoD)/BAMG inoculated with adipose-derived stem cells (ADSC) to explore its effect on smooth muscle regeneration and bladder repair function in a rat augmentation model.

Methods

We performed many biotechniques, such as reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, MTT assay, HE staining, masson staining, and immunohistochemistry in our study. Lipid nanospheres were transfected into rat ADSCs after encapsulate saRNA-MyoD as an introduction vector. Lipid nanospheres encapsulated with saRNA-MyoD were transfected into rat ADSCs. The functional transfected rat ADSCs were called ADSC-NP(saMyoD). Then, Rat models were divided into four groups: sham group, ADSC-BAMG group, ADSC-NP(saMyoD)/BAMG group, and ADSC-NP(saMyoD)/SF(VEGF)/BAMG group. Finally, we compared the bladder function of different models by detecting the bladder histology, bladder capacity, smooth muscle function in each group.

Results

RT-PCR and Western blot results showed that ADSCs transfected with NP(saMyoD) could induce high expression of α-SMA, SM22α, and Desmin. At the same time, MTT analysis showed that NP(saMyoD) did not affect the activity of ADSC cells, suggesting little toxicity. HE staining and immunohistochemistry indicated that the rat bladder repair effect (smooth muscle function, bladder capacities) was better in the ADSC-NP(saMyoD)/BAMG group, ADSC-NP(saMyoD)/SF(VEGF)/BAMG group than in the control group.

Conclusions

Taken together, our results demonstrate that the NP(saMyoD)/SF(VEGF)/BAMG scaffold seeded with ADSCs could promote bladder morphological regeneration and improved bladder urinary function. This strategy of ADSC-NP(saMyoD)/SF(VEGF)/BAMG may has a potential to repair bladder defects in the future.

Regenerative medicine for urological tissues: Updated review 2018

The focus of the present review on regenerative medicine is limited; first, on a few human clinical trials carried out thus far in the urology field, and second, on more basic but important biological progress that regenerative medicine has brought us. Clinical trials for the bladder, urethra and urethral sphincter have been carried out thus far. Reconstruction with autologous cell-seeded biomaterial failed in patients in need of bladder augmentation. The strategy succeeded for urethral reconstruction in patients who might not have required this approach. Sphincter function improvement was attained by cell therapy, but did not equal the conventional standard therapy - the artificial sphincter. The radical progress in regenerative medicine is reported in more basic stem cell technology. The strategy to induce therapeutic cells from inducible pluripotent stem cells has shed novel light on developmental biology. In vitro creation of novel kidney tissue from inducible pluripotent stem cells has been attained. Other kinds of therapeutic cells could also be induced from the inducible pluripotent stem cells. Research should be encouraged to fill the gap between patient needs and what current regenerative medicine can attain.

Translational Research for Pediatric Lower Urinary Tract Dysfunction

This review provides a comprehensive view of translational research aimed at elucidating the pathophysiology of pediatric lower urinary tract dysfunction (LUTD). A web search was conducted according to combinations of keywords, and the significance of each article was defined by the author. The dramatic evolution of the mass analysis method of genomes, transcripts, and proteins has enabled a comprehensive analysis of molecular events underlying diseases, and these methodologies have also been applied to pediatric LUTD. In genetic analyses of syndromes underlying daytime incontinence, urofacial (Ochoa) syndrome may be creating a prototype of a new research approach. Nocturnal enuresis has long been studied genetically, and several candidate loci have been reported. However, the pursuit for enuresis genes has been abandoned partly because genetic association and enuresis phenotype (bladder or renal type) could not be linked. Enuresis associated with diabetes insipidus has provided new insights into the etiology of the diseases. A chronobiological approach may shed new light on this area. Posterior urethral valves and neurogenic bladders have attracted the interest of pediatric urologists to the smooth muscle biology of the bladder. Bladder exstrophy and cloacal anomalies are rare but major anomalies caused by defective urorectal development and have recently been studied from a genetic standpoint. Translational studies for pediatric LUTD may be extended to adult bladder disease, or to application of precision medicine for diseased children.

Co-delivery of VEGF and bFGF via a PLGA nanoparticle-modified BAM for effective contracture inhibition of regenerated bladder tissue in rabbits

Graft contracture is a common problem associated with the regeneration processes of tissue-engineered bladders. Currently, most strategies used for incorporating bioactive molecules into biomaterial designs do not work during all phases of tissue regeneration. In this study, we used a growth factor-PLGA nanoparticle thermo-sensitive gel system (i.e., BAM with incorporated VEGF and bFGF-loaded PLGA nanoparticles and mixed with a hydrophilic gel) to promote bladder tissue regeneration in a rabbit model. At 4 and 12 weeks after surgery, contracture rate assessment and histological examination were conducted to evaluate bladder tissue regeneration. The results indicated that the functional composite scaffold continuously and effectively released VEGF and bFGF and promoted bladder reconstruction with a significant decrease in graft contracture. In addition, the number and arrangement of regenerated urothelial cells and smooth muscle cells as well as microvascular density and maturity were improved in the VEGF/bFGF nanoparticle group compared with the single factor VEGF or bFGF nanoparticle group and BAM alone. The nanoparticle thermo-sensitive gel system, which exhibited favourable performance, may effectively inhibit graft contracture and promote bladder tissue regeneration in rabbits.

Human urinary bladder regeneration through tissue engineering - an analysis of 131 clinical cases

Replacement of urinary bladder tissue with functional equivalents remains one of the most challenging problems of reconstructive urology over the last several decades. The gold standard treatment for urinary diversion after radical cystectomy is the ileal conduit or neobladder; however, this technique is associated with numerous complications including electrolyte imbalances, mucus production, and the potential for malignant transformation. Tissue engineering techniques provide the impetus to construct functional bladder substitutes de novo. Within this review, we have thoroughly perused the literature utilizing PubMed in order to identify clinical studies involving bladder reconstruction utilizing tissue engineering methodologies. The idea of urinary bladder regeneration through tissue engineering dates back to the 1950s. Many natural and synthetic biomaterials such as plastic mold, gelatin sponge, Japanese paper, preserved dog bladder, lyophilized human dura, bovine pericardium, small intestinal submucosa, bladder acellular matrix, or composite of collagen and polyglycolic acid were used for urinary bladder regeneration with a wide range of outcomes. Recent progress in the tissue engineering field suggest that in vitro engineered bladder wall substitutes may have expanded clinical applicability in near future but preclinical investigations on large animal models with defective bladders are necessary to optimize the methods of bladder reconstruction by tissue engineering in humans.

Age-related alterations in regeneration of the urinary bladder after subtotal cystectomy

Prior work documented that surgical removal of approximately 70% of the bladder (subtotal cystectomy) in 12-week-old female rats induced complete functional regeneration of the bladder within 8 weeks. To determine whether animal age affects bladder regeneration, female F344 rats aged 12 weeks (young) and 12 months (old) underwent subtotal cystectomy, and then were evaluated from 1 to 26 weeks after subtotal cystectomy. At 26 weeks after subtotal cystectomy, bladder capacity in young animals was indistinguishable from that in age-matched controls, but bladder capacity in old animals was only approximately 56% of that in age-matched controls. There was no detectable difference in residual volume among treatment groups, but the diminished regeneration in old animals was associated with a corresponding increase in the ratio of residual volume to micturition volume. The majority of old animals exhibited evidence of chronic kidney damage after subtotal cystectomy. Maximal contraction of bladder strips to electrical field stimulation, as well as activation with carbachol, phenylephrine, and KCl, were lower in old than in young animals at 26 weeks after subtotal cystectomy. Immunostaining with proliferating cell nuclear antigen and Von Willebrand factor revealed delayed and/or diminished proliferative and angiogenic responses, respectively, in old animals. These results confirm prior work and suggest that multiple mechanisms may contribute to an age-related decline in the regenerative capacity of the bladder.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Coadministration of platelet-derived growth factor-BB and vascular endothelial growth factor with bladder acellular matrix enhances smooth muscle regeneration and vascularization for bladder augmentation in a rabbit model

Tissue-engineering techniques have brought a great hope for bladder repair and reconstruction. The crucial requirements of a tissue-engineered bladder are bladder smooth muscle regeneration and vascularization. In this study, partial rabbit bladder (4×5 cm) was removed and replaced with a porcine bladder acellular matrix (BAM) that was equal in size. BAM was incorporated with platelet-derived growth factor-BB (PDGF-BB) and vascular endothelial growth factor (VEGF) in the experimental group while with no bioactive factors in the control group. The bladder tissue strip contractility in the experimental rabbits was better than that in the control ones postoperation. Histological evaluation revealed that smooth muscle regeneration and vascularization in the experimental group were significantly improved compared with those in the control group (p<0.05), while multilayered urothelium was formed in both groups. Muscle strip contractility of neobladder in the experimental group exhibited significantly better than that in the control (p<0.05) assessed with electrical field stimulation and carbachol interference. The activity of matrix metalloproteinase-2 (MMP-2) and MMP-9 in the native bladder tissue around tissue-engineered neobladder in the experimental group was significantly higher than that in the control (p<0.05). This work suggests that smooth muscle regeneration and vascularization in tissue-engineered neobladder and recovery of bladder function could be enhanced by PDGF-BB and VEGF incorporated within BAM, which promoted the upregulation of the activity of MMP-2 and MMP-9 of native bladder tissue around the tissue-engineered neobladder.

Hair follicle stem cells can be driven into a urothelial-like phenotype: an experimental study

The aim of this study was to show that conditioned medium might induce transdifferentiation of hair follicle stem cells into urothelial-like cells. Several conditioned media and culture conditions (skeletal muscle cell conditioned medium, smooth muscle cell conditioned medium, fibroblast conditioned medium, transforming growth factor-conditioned medium, urothelial cell conditioned medium, and co-culture of hair follicle stem cells and urothelial cells) were used. The hair follicle stem cells phenotype from rat whisker hair follicles was checked by using flow cytometry and immunofluorescence. Cytokeratins 7, 8, 15 and 18 were used as markers. Urothelial cell conditioned medium increased the expression of urothelial markers (cytokeratin 7, cytokeratin 8, cytokeratin 18), whereas it decreased a hair follicle stem cells marker (cytokeratin 15) after 2 weeks of culture. This process depended on the time of cultivation. This medium was able to sustain the epithelial phenotype of the culture. Other media including a co-culture system failed to induce similar changes. Smooth muscle conditioned medium resulted in a loss of cells in culture. Hair follicle stem cells are capable of differentiating into urothelial-like cells in vitro when exposed to a bladder-specific microenvironment.

Tissue engineering for the oncologic urinary bladder

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

Bladder expression of CD cell surface antigens and cell-type-specific transcriptomes

Many cell types have no known functional attributes. In the bladder and prostate, basal epithelial and stromal cells appear similar in cytomorphology and share several cell surface markers. Their total gene expression (transcriptome) should provide a clear measure of the extent to which they are alike functionally. Since urologic stromal cells are known to mediate organ-specific tissue formation, these cells in cancers might exhibit aberrant gene expression affecting their function. For transcriptomes, cluster designation (CD) antigens have been identified for cell sorting. The sorted cell populations can be analyzed by DNA microarrays. Various bladder cell types have unique complements of CD molecules. CD9(+) urothelial, CD104(+) basal and CD13(+) stromal cells of the lamina propria were therefore analyzed, as were CD9(+) cancer and CD13(+) cancer-associated stromal cells. The transcriptome datasets were compared by principal components analysis for relatedness between cell types; those with similarity in gene expression indicated similar function. Although bladder and prostate basal cells shared CD markers such as CD104, CD44 and CD49f, they differed in overall gene expression. Basal cells also lacked stem cell gene expression. The bladder luminal and stromal transcriptomes were distinct from their prostate counterparts. In bladder cancer, not only the urothelial but also the stromal cells showed gene expression alteration. The cancer process in both might thus involve defective stromal signaling. These cell-type transcriptomes provide a means to monitor in vitro models in which various CD-isolated cell types can be combined to study bladder differentiation and bladder tumor development based on cell-cell interaction.

Regeneration of native-like neo-urinary tissue from nonbladder cell sources

Urinary pathology requiring urinary diversion, partial or full bladder replacement, is a significant clinical problem affecting ~14,000 individuals annually in the United States alone. The use of gastrointestinal tissue for urinary diversion or bladder reconstruction/replacement surgeries is frequently associated with complications. To try and alleviate or reduce the frequency of these complications, tissue engineering and regenerative medicine strategies have been developed using bio-absorbable materials seeded with cells derived from the bladder. However, bladder-sourced cells may not always be suitable for such applications, especially in patients with bladder cancer. In this study, we describe the isolation and characterization of smooth muscle cells (SMCs) from porcine adipose and peripheral blood that are phenotypically and functionally indistinguishable from bladder-derived SMCs. In a preclinical Good Laboratory Practice study, we demonstrate that autologous adipose- and peripheral blood-derived SMCs may be used to seed synthetic, biodegradable tubular scaffold structures and that implantation of these seeded scaffolds into a porcine cystectomy model leads to successful de novo regeneration of a tubular neo-organ composed of urinary-like neo-tissue that is histologically identical to native bladder. The ability to create urologic structures de novo from scaffolds seeded by autologous adipose- or peripheral blood-derived SMCs will greatly facilitate the translation of urologic tissue engineering technologies into clinical practice.

Comparison of the Effects by Obybutynin and Tolterodine on Spina Bifida Patients: A Pilot Crossover Study

OBJECTIVES

To compare the effects of obybutynin and tolterodine in neurogenic bladder patients with spina bifida in a crossover study.

METHODS

Seven myelomeningocele and one spinal lipoma cases, maintained with obybutynin and clean intermittent catheterization for more than 60 months, were enrolled. Age ranged from 8 to 23 years (mean 12.0, male/ female = 2/6). After 2 weeks of washout period, obybutynin (0.3 mg/kg, maximum 12 mg) or tolterodine (0.12 mg/kg, maximum 4 mg) was administered for 4 weeks, and then switched to the other drug for 4 weeks. At the end of the three periods, the patients and/or parents documented urinary storage status and adverse effects, and urodynamic study was performed.

RESULTS

In seven cases undergoing sequential urodynamic study, the baseline compliance of the patients (6.81 ± 1.83) increased to 9.98 ± 4.97 by obybutynin and 10.16 ± 2.53 by tolterodine (P < 0.05 for each). Better compliance was noted in two cases with tolterodine and in two cases with obybutynin. Stronger adverse effects were reported in three out of eight patients (37.5%) by obybutynin and three out of eight patients (37.5%) by tolterodine. Although storage effect and side effects were equivalent for total patients, markedly diverse response was noted for each patient, with five choosing tolterodine and three choosing obybutynin.

CONCLUSIONS

Individualized evaluation is required for optimal choice of anticholinergics.

Development of a porcine bladder acellular matrix with well-preserved extracellular bioactive factors for tissue engineering

In this study, we compared four decellularization protocols and finally developed an optimized one through which a porcine bladder acellular matrix (BAM) with well-preserved extracellular bioactive factors had been prepared. In this protocol, the intact bladder was treated with trypsin/ethylenediaminetetraacetic acid to remove the urothelium, then with hypotonic buffer and Triton X-100 in hypertonic buffer to remove the membranous and cytoplasmic materials, and finally with nuclease to degrade the cellular nuclear components. Bladder distention and mechanical agitation were simultaneously used to facilitate cell removal. Meanwhile, several preservative techniques, including limitation of wash time, supplement with inhibitors of proteinase, control of the pH value and temperature of the wash buffer, ethylene oxide sterilization, and lyophilization of the scaffold for storage, were used to protect the extracellular bioactive factors. This decellularization protocol had completely removed the cellular materials and well preserved the extracellular collagen, sulfated glycosaminoglycan (GAG), and bioactive factors. The preserved bioactive factors had a great potential of promoting the proliferation and migration of both human bladder smooth muscle cell and human umbilical vein endothelial cell. It was also found that the amount of two representative bioactive factors, platelet-derived growth factor BB and vascular endothelial growth factor, was positively correlated with the sulfated GAG content in the porcine BAM, implying that the amount of sulfated GAG might be a determinant for preservation of bioactive factors in the decellularized tissues. In conclusion, the porcine BAM with well-preserved extracellular bioactive factors might be a favorable scaffold for tissue engineering applications.

Early stages of in situ bladder regeneration in a rodent model

Surgical removal of approximately 70% of the bladder (subtotal cystectomy [STC]) was used as a model system to gain insight into the normal regenerative process in adult mammals in vivo. Female F344 rats underwent STC, and at 2, 4, and 8 weeks post-STC, bladder regeneration was monitored via microcomputed tomography scans, urodynamic (bladder function studies) pharmacologic studies, and immunohistochemistry. Computed tomography imaging revealed a time-dependent increase in bladder size at 2, 4, and 8 weeks post-STC, which positively correlated with restoration of bladder function. Bladders emptied completely at all time points studied. The maximal contractile response to pharmacological activation and electrical field stimulation increased over time in isolated tissue strips from regenerating bladders, but remained lower at all time points compared with strips from age-matched control bladders. Immunostaining of the bladder wall of STC rats suggested a role for progenitor cells and cellular proliferation in the regenerative response. Immunostaining and the presence of electrical field stimulation-induced contractile responses verified innervation of the regenerated bladder. These initial studies establish the utility of the present model system for studying de novo tissue regeneration in vivo and may provide guidance with respect to optimization of intrinsic regenerative capacity for clinical applications.

In vitro evaluation of the bioactive factors preserved in porcine small intestinal submucosa through cellular biological approaches

The objective of this study was to develop cellular biological approaches to evaluate the potential effect of bioactive factors in porcine small intestinal submucosa (SIS) on bladder regeneration and angiogenesis. For this purpose, we cultured human bladder smooth muscle cell (HBSMC) and human umbilical vein endothelial cell (HUVEC), and then used cellular biological techniques to characterize in vitro biological effect of SIS components on HBSMC and HUVEC. Our results indicated that the SIS components had stimulated the attachment, proliferation, and migration of HBSMC and HUVEC, as well as tube formation by HUVEC on Matrigel. These results implied that the SIS might have preserved a mixture of bioactive factors including cell adhesion factors, mitogenic factors, chemotactic cytokines, and angiogenic factors, and these bioactive factors would have the potential of promoting bladder regeneration and angiogenesis. In conclusion, these cellular biological approaches might be helpful and effective for evaluation of the bioactive factors preserved in porcine SIS before it is used for bladder augmentation in humans.

Hair stem cells for bladder regeneration in rats: preliminary results

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Nerve growth factor combined with vascular endothelial growth factor enhances regeneration of bladder acellular matrix graft in spinal cord injury-induced neurogenic rat bladder

OBJECTIVE

To determine the combined effects of nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) on regeneration of the bladder acellular matrix graft (BAMG) in spinal cord injury (SCI)-mediated neurogenic bladder in rats.

MATERIALS AND METHODS

In all, 40 female Sprague-Dawley rats were used. At 8 weeks after spinalization surgery (neurogenic bladder), they were divided into five groups consisting of untreated controls and those whose bladders were injected with either no growth factor, NGF (2 microg/rat), VEGF (2 microg/rat) or both at partial BAMG replacement surgery. After 8 weeks, bladder function was assessed by urodynamic studies and the bladders were harvested for histological examination. Smooth muscle induction, collagen and nerve fibre regeneration were assessed immunohistochemically using antibodies to smooth muscle actin (alpha-actin), Masson's trichrome and protein gene product 9.5, respectively.

RESULTS

Bladder capacity and compliance were significantly increased in all BAMG groups 8 weeks after surgery compared with that before bladder replacement surgery. Bladder capacity and compliance were much higher in the VEGF and NGF combined group than in the control, or NGF and VEGF alone groups. There was no significant difference in the residual volume ratio among all groups.

CONCLUSIONS

This is the first report showing that NGF has a significant synergistic effect on the development, differentiation and functional restoration of the BAMG when administered with VEGF in neurogenic bladder. Our results indicate that NGF may be a useful cytokine for enhancing the regeneration of a functional bladder following acellular matrix grafting in a neurogenic rat model.

Bladder tissue engineering through nanotechnology

The field of tissue engineering has developed in phases: initially researchers searched for "inert" biomaterials to act solely as replacement structures in the body. Then, they explored biodegradable scaffolds--both naturally derived and synthetic--for the temporary support of growing tissues. Now, a third phase of tissue engineering has developed, through the subcategory of "regenerative medicine." This renewed focus toward control over tissue morphology and cell phenotype requires proportional advances in scaffold design. Discoveries in nanotechnology have driven both our understanding of cell-substrate interactions, and our ability to influence them. By operating at the size regime of proteins themselves, nanotechnology gives us the opportunity to directly speak the language of cells, through reliable, repeatable creation of nanoscale features. Understanding the synthesis of nanoscale materials, via "top-down" and "bottom-up" strategies, allows researchers to assess the capabilities and limits inherent in both techniques. Urology research as a whole, and bladder regeneration in particular, are well-positioned to benefit from such advances, since our present technology has yet to reach the end goal of functional bladder restoration. In this article, we discuss the current applications of nanoscale materials to bladder tissue engineering, and encourage researchers to explore these interdisciplinary technologies now, or risk playing catch-up in the future.