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

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.

Procyanidins-crosslinked small intestine submucosa: A bladder patch promotes smooth muscle regeneration and bladder function restoration in a rabbit model

Currently the standard surgical treatment for bladder defects is augmentation cystoplasty with autologous tissues, which has many side effects. Biomaterials such as small intestine submucosa (SIS) can provide an alternative scaffold for the repair as bladder patches. Previous studies have shown that SIS could enhance the capacity and compliance of the bladder, but its application is hindered by issues like limited smooth muscle regeneration and stone formation since the fast degradation and poor mechanical properties of the SIS. Procyanidins (PC), a natural bio-crosslinking agent, has shown anti-calcification, anti-inflammatory and anti-oxidation properties. More importantly, PC and SIS can crosslink through hydrogen bonds, which may endow the material with enhanced mechanical property and stabilized functionalities. In this study, various concentrations of PC-crosslinked SIS (PC-SIS) were prepared to repair the full-thickness bladder defects, with an aim to reduce complications and enhance bladder functions. In vitro assays showed that the crosslinking has conferred the biomaterial with superior mechanical property and anti-calcification property, ability to promote smooth muscle cell adhesion and upregulate functional genes expression. Using a rabbit model with bladder defects, we demonstrated that the PC-SIS scaffold can rapidly promote in situ tissue regrowth and regeneration, in particular smooth muscle remodeling and improvement of urinary functions. The PC-SIS scaffold has therefore provided a promising material for the reconstruction of a functional bladder.

Construction of a vascularized bladder with autologous adipose-derived stromal vascular fraction cells combined with bladder acellular matrix via tissue engineering

The formation of an effective vascular network can promote peripheral angiogenesis, ensuring an effective supply of blood, oxygen, and nutrients to an engineered bladder, which is important for bladder tissue engineering. Stromal vascular fraction cells (SVFs) promote vascularization and improve the function of injured tissues. In this study, adipose tissue-derived SVFs were introduced as an angiogenic cell source and seeded into the bladder acellular matrix (BAM) to generate a SVF-BAM complex for bladder reconstruction. The morphological regeneration and functional restoration of the engineered bladder were evaluated. In addition, we also explored the role of the Wnt5a/sFlt-1 noncanonical Wnt signaling pathway in regulating the angiogenesis of SVFs, and in maintaining the rational capability of SVFs to differentiate into vasculature in regenerated tissues. Histological assessment indicated that the SVF-BAM complex was more effective in promoting smooth muscle, vascular, and nerve regeneration than BAM alone and subsequently led to the restoration of bladder volume and bladder compliance. Moreover, exogenous Wnt5a was able to enhance angiogenesis by increasing the activity of MMP2, MMP9, and VEGFR2. Simultaneously, the expression of sFlt-1 was also increased, which enhanced the stability of the SVFs angiogenic capability. SVFs may be a potential cell source for tissue-engineered bladders. The Wnt5a/sFlt-1 pathway is involved in the regulation of autologous vascular formation by SVFs. The rational regulation of this pathway can promote neo-microvascularization in tissue-engineered bladders.

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.

Linearized texture of three-dimensional extracellular matrix is mandatory for bladder cancer cell invasion

In the fields of biomaterials and tissue engineering simulating the native microenvironment is of utmost importance. As a major component of the microenvironment, the extracellular matrix (ECM) contributes to tissue homeostasis, whereas modifications of native features are associated with pathological conditions. Furthermore, three-dimensional (3D) geometry is an important feature of synthetic scaffolds favoring cell stemness, maintenance and differentiation. We analyzed the 3D structure, geometrical measurements and anisotropy of the ECM isolated from (i) human bladder mucosa (basal lamina and lamina propria) and muscularis propria; and, (ii) bladder carcinoma (BC). Next, binding and invasion of bladder metastatic cell line was observed on synthetic scaffold recapitulating anisotropy of tumoral ECM, but not on scaffold with disorganized texture typical of non-neoplastic lamina propria. This study provided information regarding the ultrastructure and geometry of healthy human bladder and BC ECMs. Likewise, using synthetic scaffolds we identified linearization of the texture as a mandatory feature for BC cell invasion. Integrating microstructure and geometry with biochemical and mechanical factors could support the development of an innovative synthetic bladder substitute or a tumoral scaffold predictive of chemotherapy outcomes.