Regional biomechanical and histological characterisation of the passive porcine urinary bladder: Implications for augmentation and tissue engineering strategies.

The aim of this study was to identify and quantify potential regional and directional variations in the quasistatic uniaxial mechanical properties of the passive urinary bladder wall. Overall, the lower body and trigone regions demonstrated the highest degree of directional anisotropy, whereas the ventral region demonstrated the least directional anisotropy. Significant regional anisotropy was found only along the apex-to-base direction. The dorsal and ventral regions demonstrated a significantly increased distensibility along the apex-to-base direction compared to the other bladder regions, whereas the trigone and lower body regions demonstrated the least distensibility. The trigone, lower body and lateral regions also demonstrated the highest tensile strength both at regional and directional levels. The study detected significant regional and directional anisotropy in the mechanical properties of the bladder and correlated this anisotropy to the distended and non-distended tissue histioarchitecture and whole organ mechanics. By elucidating the inhomogeneous nature of the bladder, the results from this study will aid the regional differentiation of bladder treatments in terms of partial bladder replacement with suitable natural or synthetic biomaterials, as well as the development of more realistic constitutive models of bladder wall biomechanics and improved computational simulations to predict deformations in the natural and augmented bladder.

Bio-engineering urothelial cells for bladder tissue transplant.

BACKGROUND: The past decade has seen a surge of interest in bladder tissue engineering research, with the anticipation that it will influence future urological practice by providing functional tissue substitutes to replace diseased or dysfunctional tissues. OBJECTIVE: To describe bladder tissue engineering strategies being investigated, with emphasis on urothelial cell biology and to discuss some of the challenges that must be addressed to ensure that this technique will find a niche in urological practice. METHODS: A review of published literature. RESULTS/CONCLUSION: In vitro-propagated urothelial cells have been incorporated into a number of bladder engineering strategies, including reconstructions using natural or synthetic biomaterials and cell-engineering approaches, where the urothelium is combined with reconfigured, vascularised host smooth muscle grafts. Although results and quality of reporting are mixed, the consensus is of progress being made towards bio-engineered bladders becoming a clinical reality once unresolved research and translational issues have been addressed.

Development and characterisation of a full-thickness acellular porcine bladder matrix for tissue engineering.

The aim of this study was to produce a natural, acellular matrix from porcine bladder tissue for use as a scaffold in developing a tissue-engineered bladder replacement. Full-thickness, intact porcine bladders were decellularised by distention and immersion in hypotonic buffer containing 0.1% (w/v) SDS and nuclease enzymes. Histological analysis of the resultant matrices showed they were completely acellular; that the major structural proteins had been retained and that there were some residual poorly soluble intracellular proteins. The amount of DNA per mg dry weight of fresh porcine bladder was 2.8 (+/-0.1) microg/mg compared to 0.1 (+/-0.1) microg/mg in decellularised bladder and biochemical analysis showed proportional differences in the hydroxyproline and glycosaminoglycan content of the tissue before and after decellularisation. Uniaxial tensile testing indicated that decellularisation did not significantly compromise the ultimate tensile strength of the tissue. There was, however, an increase in the collagen and elastin phase slopes indicating decreased extensibility. Cytotoxicity assays using porcine smooth muscle cell cultures excluded the presence of soluble toxins in the biomaterial. In summary, a full-thickness natural acellular matrix retaining the major structural components and strength of the urinary bladder has been successfully developed. The matrix is biocompatible with bladder-derived cells and has potential for use in urological surgery and tissue-engineering applications.

Bone morphogenetic protein-4 enhances cardiomyocyte differentiation of cynomolgus monkey ESCs in knockout serum replacement medium.

Despite extensive research in the differentiation of rodent ESCs into cardiomyocytes, there have been few studies of this process in primates. In this study, we examined the role of bone morphogenic protein-4 (BMP-4) to induce cardiomyocyte differentiation of cynomolgus monkey ESCs. To study the role of BMP-4, EBs were formed and cultured in Knockout Serum Replacement (KSR) medium containing BMP-4 for 8 days and subsequently seeded in gelatin-coated dishes for 20 days. It was found that ESCs differentiated into cardiomyocytes upon stimulation with BMP-4 in KSR medium, which resulted in a large fraction of beating EBs ( approximately 16%) and the upregulation of cardiac-specific proteins in a dose and time-dependent manner. In contrast, the addition of BMP-4 in FBS-containing medium resulted in a lower fraction of beating EBs ( approximately 6%). BMP-4 acted principally between mesendodermal and mesoderm progenitors and subsequently enhanced their expression. Ultrastructural observation revealed that beating EBs contained mature cardiomyocytes with sarcomeric structures. In addition, immunostaining, reverse transcription-polymerase chain reaction, and Western blotting for cardiac markers confirmed the increased differentiation of cardiomyocytes in these cultures. Moreover, electrophysiological studies demonstrated that the differentiated cardiomyocytes were electrically activated. These findings may be useful in developing effective culture conditions to differentiate cynomolgus monkey ESCs into cardiomyocytes for studying developmental biology and for regenerative medicine.

Review: tissue engineering of the urinary bladder: considering structure-function relationships and the role of mechanotransduction.

A variety of conditions encountered in urology result in bladder dysfunction and the need for bioengineered tissue substitutes. Traditionally, a number of synthetic materials and natural matrices have been used in experimental and clinical settings. However, the production of functional bladder tissue replacements remains elusive. The urinary bladder sustains considerable structural deformation during its normal function and represents an ideal model tissue in which to study the effects of biomechanical simulation on tissue morphogenesis, differentiation, and function. However, the actual role of mechanical forces within the bladder has received little attention. A strategy in which in vitro-generated tissue constructs are conditioned by exposure to the same mechanical forces as they would encounter in vivo could potentially be used both in the development of functional tissue replacements and to further study the role of biomechanical signalling. The purpose of this review is to examine the role and structure-function relationship of the urinary bladder and, through consultation of the literature available on mechanotransduction and tissue engineering of alternative tissues, to determine the factors that need to be considered when biomechanically engineering a functional bladder.