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.

Novel Three-Dimensional Bladder Reconstruction Model from B-Mode Ultrasound Image to Improve the Accuracy of Bladder Volume Measurement

Traditional bladder volume measurement from B-mode (two-dimensional) ultrasound has been found to produce inaccurate results, and thus in this work we aim to improve the accuracy of measurement from B-mode ultrasound. A total of 75 electronic medical records including ultrasonic images were reviewed retrospectively from 64 patients. We put forward a novel bladder volume measurement method, in which a three-dimensional (3D) reconstruction model was established from conventional two-dimensional (2D) ultrasonic images to estimate the bladder volume. The differences and relationships were analyzed among the actual volume, the traditional estimated volume, and the new reconstruction model estimated volume. We also compared the data in different volume groups from small volume to high volume. The mean actual volume is 531.8 mL and the standard deviation is 268.7 mL; the mean percentage error of traditional estimation is −28%. In our new bladder measurement method, the mean percentage error is −10.18% (N = 2), −4.72% (N = 3), −0.33% (N = 4), and 2.58% (N = 5). There is no significant difference between the actual volume and our new bladder measurement method (N = 4) in all data or the divided four groups. The estimated volumes from the traditional method or our new method are highly correlated with the actual volume. Our data show that the three-dimensional bladder reconstruction model provides an accurate measurement from conventional B-mode ultrasonic images compared with the traditional method. The accuracy is seen across different groups of volume, and thus we can conclude that this is a reliable and economical volume measurement model that can be applied in general software or in apps on mobile devices.

Current Applications and Future Directions of Bioengineering Approaches for Bladder Augmentation and Reconstruction

End-stage neurogenic bladder usually results in the insufficiency of upper urinary tract, requiring bladder augmentation with intestinal tissue. To avoid complications of augmentation cystoplasty, tissue-engineering technique could offer a new approach to bladder reconstruction. This work reviews the current state of bioengineering progress and barriers in bladder augmentation or reconstruction and proposes an innovative method to address the obstacles of bladder augmentation. The ideal tissue-engineered bladder has the characteristics of high biocompatibility, compliance, and specialized urothelium to protect the upper urinary tract and prevent extravasation of urine. Despite that many reports have demonstrated that bioengineered bladder possessed a similar structure to native bladder, few large animal experiments, and clinical applications have been performed successfully. The lack of satisfactory outcomes over the past decades may have become an important factor hindering the development in this field. More studies should be warranted to promote the use of tissue-engineered bladders in clinical practice.

Bovine tunica albuginea conserved in honey as xenograft for cystoplasty in rats

ABSTRACT: Urinary bladder damages leading to few viable bladder tissue available might demand a challenging reconstructive surgery. In this context, biomaterials are valid alternatives for bladder reconstruction. This study evaluated the bovine tunica albuginea fragment as graft material for cystoplasty in rats and honey-preserved implant viability.Thirty Wistar rats were assigned to two groups: (1) a test group (T) with a circular 1.0-cm-diameterbovine tunica albuginea graft application in the apex region by a continuous absorbable (Polyglactin 910 5-0) suture with stitching of all bladder layers and (2) a simulation group (S) in which animals underwent only partial cystectomy. In addition, each of these groups was further divided into three subgroups according to euthanasia period on post-surgery day 7, 15 and 30.Two animals had self-limiting hematuria at postsurgical period. At necropsy, frequent crystals and adhesion to the peritoneum were observed. At the histopathological evaluation, animals from the T group euthanized by 15th postoperative day had layers disorganization and initial muscle development, while T group rats euthanized by 30th postoperative day showed complete urothelization. Urothelization pattern was similar in both groups. Moreover, the muscular layer formation was present in both groups, but more evident in S group animals. Nevertheless, inflammatory infiltrate and neovascularization were remarkably more intense in T group rats.It might be concluded that bovine tunica albuginea graft was successful in repairing rats’ bladder, being a good biomaterial option in reconstructive urinary vesicle surgery.

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

The scaffold, constructed by the bi-layer silk fibroin skeleton (BSFS) and the bladder acellular matrix hydrogel (BAMH) encapsulated with the adipose-derived stem cells (ASCs), was performed for the bladder augmentation...

Tissue-engineered autologous peritoneal grafts for bladder reconstruction in a porcine model

Ileal neobladder construction is a common treatment for patients with bladder cancer after radical cystectomy. However, metabolic disorders caused by transposed bowel segments occur frequently. Bladder tissue engineering is a promising alternative approach. Although numerous studies have reported bladder reconstruction using acellular and cellular scaffolds, there are also disadvantages associated with these methods, such as immunogenicity of synthetic grafts and incompatible mechanical properties of the biomaterials. Here, we engineered an autologous peritoneal graft consisting of a peritoneal sheet and the seromuscular layer from the ileum. Three months after the surgery, compared with the neobladder made from the ileum, the reconstructed neobladder using our new method showed normal function and better gross morphological characteristics. Moreover, histopathological and transcriptomic analysis revealed urothelium-like cells expressing urothelial biomarkers appeared in the neobladder, while no such changes were observed in the control group. Overall, our study provides a new strategy for bladder tissue engineering and informs a variety of future research prospects.