Laparoscopy in Ureteral Engineering: A Feasibility Study

Grafting of CAG peptides and (polyethylene glycol) on unsaturated polyurethane films to promote selective adhesion and migration of urethral epithelial cells

Selective adhesion and migration of urethral epithelial cells (HUCs) over fibroblasts (FIBs) are very important in the reconstruction of the urethral epithelial layer and prevention of ureteral scarring and stenosis. In this study, unsaturated polyurethane (PPFU-CO-SS) films were co-grafted with a cell-resisting poly(ethylene glycol) (PEG) layer and HUC-selective Cys-Ala-Gly (CAG) peptides, whose physicochemical changes were confirmed by X-ray photon spectroscopy, fluorescence spectroscopy and water contact angle measurements. The adhesion and activation of platelets on the PEG/CAG grafted surface were significantly reduced compared to those on the PPFU-CO-SS, resulting in a similar status as that on a PEG-grafted surface. The HUC-selective material could obviously promote the adhesion and migration of HUCs. The ratio of the urethral epithelial cells to fibroblasts on the PEG/CAG grafted surface was nearly 3-fold that on the unmodified PPFU-CO-SS in a co-culture competitive environment. The urethral epithelial cells cultured on the PEG/CAG grafted surface also had the highest migration rate, which was 2.24-fold compared to that on the PPFU-CO-SS control.

Adult iatrogenic ureteral injury and stricture-incidence and treatment strategies

Iatrogenic ureteral injuries and strictures are relatively common complication of pelvic surgery and radiation treatment. Left untreated they are associated with severe short- and long-term complications such as urinoma, septic state, renal failure, and loss of a renal unit. Treatment depends on timing of diagnosis, as well as extent of injury, and ranges from simple endoscopic management to complex surgical reconstruction under usage of pedicled grafts. While recent advances in ureteral tissue engineering are promising the topic is still underreported. Historically a domain of open surgery, laparoscopic and robotic-assisted approaches have proven their feasibility in small case series, and are increasingly being utilized as means of reconstructive surgery. This review aims to give an outline of incidence and treatment of ureteral injuries and strictures in light of the latest advances.

Construction of ureteral grafts by seeding bone marrow mesenchymal stem cells and smooth muscle cells into bladder acellular matrix

BACKGROUND

Congenital or acquired abnormalities may cause an ureteral injury or defect. The main methods to reconstruct a long ureter often cause serious complications. In this study, we sought to construct a tissue-engineered graft by seeding bone marrow mesenchymal stem cells (MSCs) and smooth muscle cells (SMCs) into a bladder acellular matrix (BAM) for ureteral reconstruction.

METHODS

Isolated, proliferated, and in vitro identified rabbit bone marrow MSCs and SMCs were seeded into BAM as the experimental group. Grafts only seeding SMCs were the control group. Cell-seeded grafts were used to construct tissue-engineered tubular grafts (TETG) for transplantation into the rabbit's omentum for 2 weeks before ureteral reconstruction. Evolutionary histology was performed at 2, 4, 8, and 16 weeks postoperatively. Renal function and ureteral obstruction were evaluated using intravenous urography at 16 weeks.

RESULTS

Flow cytometry demonstrated bone marrow MSCs to express CD29, CD44, CD90, but not CD34. Histological examination revealed consistent regeneration of TETG urothelium in the experimental group. At 8 and 16 weeks after TETG grafting in vivo, multilayer urothelium covered the entire lumen with visible neovascularization within the center. Organized smooth muscle bundles were observed. Intravenous urography demonstrated no ureteral stricture or hydronephrosis. The 5 rabbits were dead within 4 weeks postoperatively. Autopsy showed scar formation inside the graft with severe hydronephrosis.

CONCLUSION

We successfully constructed a TETG by seeding bone marrow MSCs and SMCs into BAM for ureteral reconstruction. Thus bone marrow MSCs can potentially promote urothelial regeneration to achieve a tissue-engineered ureter.

Tissue engineering and ureter regeneration: is it possible?

Large ureter damages are difficult to reconstruct. Current techniques are complicated, difficult to perform, and often associated with failures. The ureter has never been regenerated thus far. Therefore the use of tissue engineering techniques for ureter reconstruction and regeneration seems to be a promising way to resolve these problems. For proper ureter regeneration the following problems must be considered: the physiological aspects of the tissue, the type and shape of the scaffold, the type of cells, and the specific environment (urine). 
This review presents tissue engineering achievements in the field of ureter regeneration focusing on the scaffold, the cells, and ureter healing.

Autologous urothelial cells transplantation onto a prefabricated capsular stent for tissue engineered ureteral reconstruction

In this study, we have fabricated an artificial ureter by transplantation of in vitro-expanded urothelial cells onto an in vivo-prefabricated capsular stent using tissue engineering methods. Spiral poly (L-lactic acid) (PLLA) stents were transplanted into the subcutaneous of Wistar rats for a period of 1, 2 or 3 weeks to induce the formation of connective tissue capsules on their surfaces. The capsular PLLA stents were then decellularized and further recellularized with bladder epithelial cells to fabricate artificial ureters. The results showed that the entrapped cells in all capsules remained continuously proliferation and lined up in continuous layers. In addition, the urothelial cells on the capsular stents with an embedding period of 2 or 3 weeks showed higher proliferative viability compared with the cells on the stents with an embedding time of 1 week (P < 0.05). The results of the study indicated that the prefabricated capsular stents could serve as alternative cell carriers for tissue engineered ureters, especially with embedding time from 2 to 3 weeks.

Differentiation of adipose-derived stem cells promotes regeneration of smooth muscle for ureteral tissue engineering

BACKGROUND

The purpose of the present study was to assess the differentiation potential of adipose-derived stem cells (ASCs) into smooth muscle cells (SMCs) and their potential for promoting regeneration of smooth muscle for ureteral tissue engineering.

METHODS

ASCs were isolated, proliferated, and identified in vitro. SMC differentiation was induced using SMC induction medium. Gene expression was evaluated by quantitative polymerase chain reaction, immunofluorescence, and Western blotting. Vessel extracellular matrix was obtained by a decellularization process. The induced cells were seeded onto vessel extracellular matrix for ureter reconstitution. Grafts were obtained for evolutionary histologic studies. Renal function and ureteral patency was evaluated by intravenous urography at 16 wk.

RESULTS

Flow cytometry demonstrated that the ASCs expressed CD90, but did not express CD45 or CD34. After 6 wk of induction, upregulation of α-smooth muscle actin expression was determined by quantitative polymerase chain reaction, and smooth muscle myosin heavy chain expression was confirmed by immunofluorescence and Western blotting in the induced cells. Vessel extracellular matrix exhibited a nontoxic and bioactive effect on the induced cells. Histologically, stratified urothelium and organized muscle bundles were observed in the grafts at 16 wk. Intravenous urography demonstrated no ureteral stricture or hydroureteronephrosis.

CONCLUSIONS

These results have demonstrated that ASCs can be differentiated into SMCs and this potential promoted smooth muscle regeneration for ureteral tissue engineering.