A New Technique for Ureteral Defect Lesion Reconstruction Using an Autologous Vein Graft and a Biodegradable Endoluminal Stent

Mechanical characterization of porcine ureter for the evaluation of tissue-engineering applications

Introduction: Clinics increasingly require readily deployable tubular substitutes to restore the functionality of structures like ureters and blood vessels. Despite extensive exploration of various materials, both synthetic and biological, the optimal solution remains elusive. Drawing on abundant literature experiences, there is a pressing demand for a substitute that not only emulates native tissue by providing requisite signals and growth factors but also exhibits appropriate mechanical resilience and behaviour. Methods: This study aims to assess the potential of porcine ureters by characterizing their biomechanical properties in their native configuration through ring and membrane flexion tests. In order to assess the tissue morphology before and after mechanical tests and the eventual alteration of tissue microstructure that would be inserted in material constitutive description, histological staining was performed on samples. Corresponding computational analyses were performed to mimic the experimental campaign to identify the constitutive material parameters. Results: The absence of any damages to muscle and collagen fibres, which only compacted after mechanical tests, was demonstrated. The experimental tests (ring and membrane flexion tests) showed non-linearity for material and geometry and the viscoelastic behaviour of the native porcine ureter. Computational models were descriptive of the mechanical behaviour ureteral tissue, and the material model feasible. Discussion: This analysis will be useful for future comparison with decellularized tissue for the evaluation of the aggression of cell removal and its effect on microstructure. The computational model could lay the basis for a reliable tool for the prediction of solicitation in the case of tubular substitutions in subsequent simulations.

Open ureteroplasty with buccal mucosa graft for long proximal strictures: A good option for a rare problem

Purpose

To report a single surgeon experience with one year follow-up after open ureteroplasty with buccal mucosa graft (OUBMG) in the rare situation of long segment proximal ureteral strictures.

Materials and Methods

Four patients with long segment proximal ureteral stricture underwent OU-BMG between February and July 2017. Functional outcome was assessed by pre- and postoperative serum creatinine, ultrasound and renal scintigraphy as well as patient reported outcomes.

Results

Four patients with an average stricture length of 4 cm underwent OU-BMG between February and July 2017. No major postoperative complications occurred. Retrograde uretero-pyelography 6 weeks postoperatively revealed a watertight anastomosis followed by immediate emptying of the renal pelvis and ureter in all four patients. Ureteroscopy at this time showed a wide lumen with well-vascularized pink mucosa. After a mean follow-up time of 12.5 (12–14) months, postoperative serum creatinine was unimpaired. Renal scintigraphy revealed no signs of renal obstruction. With regard to intraoral surgery, no difficulties with mouth opening or intraoral dryness or numbness were reported.

Conclusions

For patients with long segment ureteral strictures OU-BMG is a safe technique with excellent surgical and functional outcomes. Hence, the application of this technique should be encouraged and regarded as one of the standard options in case of this rare problem.

RUG technique: replacement of the ureter with gonadal vein. A cadaveric study

BACKGROUND

Ureteral defect lesions may result from retroperitoneal fibrosis, radiation damage, tumors, or surgical procedures; the management of long-segment ureteral defects is a challenge for urologists. Total or partial replacement of the ureter is sometimes required, with consequent ileal interposition, but this technique may lead to several complications, such as severe urinary infections. In a few cases, nephrectomy may be required. Starting from the above considerations, we can postulate the RUG technique (replacement of the ureter with gonadal vein), using the gonadal vein (GoV) as an autologous graft to substitute the ureter. For this reason, we decided to test this novel idea on an experimental model.

METHODS

We tested the above technique on a cadaveric model, performing complete procedure (RUG #1), segmental replacement of the ureter (RUG #2), and ureteroplasty with a GoV patch (RUG #3). All the procedures involved an open approach. After RUG #3, the treated segment of the ureter was sampled for histologic analysis.

RESULTS

Four RUGs were performed (two RUG #1, one RUG #2, one RUG #3). All anatomic structures were easily identified, and all procedures were completed successfully. The dimensions of the ureters were comparable to those of the GoV in all cases, as usual. Histologic analysis demonstrated perfect adherence of the two anastomosed structures.

CONCLUSIONS

The RUG technique resulted in an adequate, safe and easy-to-perform surgical alternative.

Precursor miR-499a Variant but not miR-196a2 is Associated with Rheumatoid Arthritis Susceptibility in an Egyptian Population

INTRODUCTION

Rheumatoid arthritis (RA) has a complex component induced by several genes that interact together with environmental and hormonal factors. We aimed to investigate the association of miR-196a2 rs11614913 (C/T) and miR-499a rs3746444 (A/G) polymorphisms and their combination with RA susceptibility and disease activity in an Egyptian population, and to evaluate their impact on methotrexate drug response and toxicity.

MATERIALS AND METHODS

Bioinformatics databases were searched to select potential micro RNA (miRNA)-messenger RNA (mRNA) interactions involved in RA pathogenesis. Ninety-five RA patients diagnosed according to the American College of Rheumatology and 200 healthy controls were genotyped using real-time polymerase chain reaction technology.

RESULTS

In overall and stratified analysis, miR-499a, but not miR-196a2, was associated with RA risk. Heterozygote carriers with rs3746444*A/G displayed protection against developing RA (p = 0.005) with an odds ratio of 0.2 (95 % confidence interval 0.17-0.62). The carriage of the combinations (miR499a*AG + miR196a2*CC) and (miR499a*AA + miR196a2*TT) were 3 and 7.5 times more likely to develop RA, respectively, while the combinations (miR499a*GG + miR196a2*CC), (miR499a*AG + miR196a2*TT) and (miR499a*AA + miR196a2*CT) show less susceptibility to have RA disease (all p < 0.05). rs3746444*AA genotype had a higher disease activity score (DAS28) [p = 0.023], tender joint count (TJC) (p = 0.007), and methotrexate-induced gastrointestinal toxicity (p = 0.043) compared with both AG/GG genotypes. rs11614913*C carriers were associated with higher DAS28 activity (p = 0.021). Homozygote male patients (CC and TT) had higher TJC (p = 0.046) and higher rheumatoid factor levels (p = 0.026), whereas, TT homozygote females had higher levels of ALT (p = 0.022).

CONCLUSIONS

Different genotypes of miR-499a rs3746444 single nucleotide polymorphisms (SNPs) are associated with RA risk, disease activity, and methotrexate toxicity in our population. In combination with specific miR-196a2 rs11614913 genotypes, this risk could increase or decrease according to the type of combination. Further functional analysis of the SNP and its impact on mRNA targets is required to confirm the relationship between genotype and phenotype.

Ureteral strictures revisited…trying to see the light at the end of the tunnel: a comprehensive review

A ureteral stricture is a rather rare urological event defined as a narrowing of the ureter causing a functional obstruction and renal failure, if left untreated. The aim of this review article is to summarize and discuss current knowledge on the incidence, pathogenesis, management, and follow up of proximal, mid, and distal ureteral strictures.

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.

Pig kidney transplantation: an up-to-date guideline

BACKGROUND

Swine and human beings have many aspects in common that make swine a well-characterized large animal model for kidney transplantation (KTx). However, pigs have some peculiar anatomical characteristics that standardized techniques must adapt to. The aim of this study was to prepare an up-to-date guideline for porcine KTx.

METHODS

To achieve this goal, we performed a Medline search using the terminology 'kidney' or 'renal' and 'transplantation' and 'pig' or 'swine' or 'porcine'. We found over 1,300 published articles since 1963. Only 13 studies focused on the surgical aspect. Furthermore, we reviewed related books and articles about swine anatomical characteristics and surgery. Finally, our experimental experiences of KTx during the last few decades were added to this collection.

RESULTS

Proper hosting, fasting, anesthesia, medical therapy and monitoring can prevent postoperative complications. Explantation with a Carrel patch of the aorta facilitates the implantation and prevents future stenosis. Native nephrectomy makes the follow-up of the implanted organ more precise. KTx in the infrarenal fossa via end-to-side anastomosis to the aorta and inferior vena cava followed by ureteroureterostomy are the recommended options for KTx in pigs compared to other possible methods.

CONCLUSION

Pigs, with respect to their characterizations, constitute one of the best large animal models for KTx. Preoperative preparations are as important as the intra- and postoperative management. Using the most adaptable methods of surgery with respect to the specific anatomical characteristics of pigs can prevent undermining the studies and avoid preventable complications and pitfalls.

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.

New ureteral scaffold constructed with composite poly(L-lactic acid)-collagen and urothelial cells by new centrifugal seeding system

A tissue-engineered ureteral scaffold was constructed with composited poly L-lactic acid (PLLA)-collagen endoluminal stent and uroepithelial cells (UECs) using a new seeding system. The electrospun PLLA-collagen nanofibrous mesh was seeded efficiently with human ureteral epithelial cells using a modified centrifugal seeding device. The cellular nanofibrous mesh was then wound around a spiral endoluminal stent to form a cellular composited PLLA-collagen ureteral scaffold. The cellular ureteral scaffold was subcutaneously implanted into nude mice. Cell attachment, distribution, and viability in vitro were investigated along with the cell fate in vivo. (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed that scaffolds seeded with centrifugal method had higher cellular activity than scaffolds seeded with static method (p < 0.05), and the metabolic activity per cell had no significant differences between the two methods (p > 0.05). Histologic analysis showed that the entrapped UECs remained in the scaffolds after 2 wk of implantation. The results of the study indicated that the composited PLLA-collagen endoluminal stent could serve as alternative cell carrier for tissue engineering ureter. In addition, the new modified centrifugal seeding system allowed rapid homogeneous distribution of cells onto the nanofibrous mesh, which will be useful to ureteral reconstruction.