Ureteral Reconstruction in Goats Using Tissue-Engineered Templates and Subcutaneous Preimplantation.

Repair of long ureteral defects often requires long graft tissues and extensive surgery. This is associated with complications, including a lack of suitable tissue and graft site morbidity. Tissue engineering may provide an attractive alternative to the autologous graft tissues. In this study, ureteral repair using (preimplanted) tubular collagen-Vicryl templates was evaluated in a new goat model. Tubular templates were prepared from tubularized Vicryl meshes and 0.7% type-I collagen (length = 6 cm, inner diameter = 6 mm, wall thickness = 3 mm). In total, twelve goats were used and evaluated after 3 months. Eight goats were implanted with the collagen-Vicryl templates and in four goats the templates were first preimplanted in the subcutis and subsequently used as ureteral graft. Template implantation was successful in 92% of the goats(11/12). During follow-up, 82% of the animals (9/11) survived without signs of discomfort. Two animals were sacrificed prematurely due to kidney perforation by the stent and urine leakage. Two other animals presented with stenosis of the neoureter due to stent migration. After preimplantation, the templates were remodeled mostly to autologous tissue with similar mechanical characteristics as the native ureter. Goats grafted with preimplanted templates presented with predominantly healthy kidneys, whereas the goats grafted with the collagen-Vicryl templates presented with fibrotic and inflamed regions in the kidneys. The use of preimplanted tissue templates showed favorable results compared with direct functional implantation of the templates. Partial remodeling toward autologous tissue and similar mechanical characteristics likely improved the integration in the ureteral tissue. Preimplantation of tissue-engineered templates should therefore be considered when two-stage procedures using a nephrostomy catheter are indicated or when planning allows for additional time to treatment.

Tissue Engineering of the Urethra: A Systematic Review and Meta-analysis of Preclinical and Clinical Studies.

CONTEXT: Urethra repair by tissue engineering has been extensively studied in laboratory animals and patients, but is not routinely used in clinical practice. OBJECTIVE: To systematically investigate preclinical and clinical evidence of the efficacy of tissue engineering for urethra repair in order to stimulate translation of preclinical studies to the clinic. EVIDENCE ACQUISITION: A systematic search strategy was applied in PubMed and EMBASE. Studies were independently screened for relevance by two reviewers, resulting in 80 preclinical and 23 clinical studies of which 63 and 13 were selected for meta-analysis to assess side effects, functionality, and study completion. Analyses for preclinical and clinical studies were performed separately. Full circumferential and inlay procedures were assessed independently. Evaluated parameters included seeding of cells and type of biomaterial. EVIDENCE SYNTHESIS: Meta-analysis revealed that cell seeding significantly reduced the probability of encountering side effects in preclinical studies. Remarkably though, cells were only sparsely used in the clinic (4/23 studies) and showed no significant reduction of side effects. ln 21 out of 23 clinical studies, decellularized templates were used, while in preclinical studies other biomaterials showed promising outcomes as well. No direct comparison to current clinical practice could be made due to the limited number of randomized controlled studies. CONCLUSIONS: Due to a lack of controlled (pre)clinical studies, the efficacy of tissue engineering for urethra repair could not be determined. Meta-analysis outcome measures were similar to current treatment options described in literature. Surprisingly, it appeared that favorable preclinical results, that is inclusion of cells, were not translated to the clinic. Improved (pre)clinical study designs may enhance clinical translation. PATIENT SUMMARY: We reviewed all available literature on urethral tissue engineering to assess the efficacy in preclinical and clinical studies. We show that improvements to (pre)clinical study design is required to improve clinical translation of tissue engineering technologies.

Enhanced cellular uptake of albumin-based lyophilisomes when functionalized with cell-penetrating peptide TAT in HeLa cells.

Lyophilisomes are a novel class of biodegradable proteinaceous nano/micrometer capsules with potential use as drug delivery carrier. Cell-penetrating peptides (CPPs) including the TAT peptide have been successfully implemented for intracellular delivery of a broad variety of cargos including various nanoparticulate pharmaceutical carriers. In the present study, lyophilisomes were modified using CPPs in order to achieve enhanced cellular uptake. Lyophilisomes were prepared by a freezing, annealing, and lyophilization method and a cystein-elongated TAT peptide was conjugated to the lyophilisomes using a heterobifunctional linker. Fluorescent-activated cell sorting (FACS) was utilized to acquire a lyophilisome population with a particle diameter smaller than 1000 nm. Cultured HeLa, OVCAR-3, Caco-2 and SKOV-3 cells were exposed to unmodified lyophilisomes and TAT-conjugated lyophilisomes and examined with FACS. HeLa cells were investigated in more detail using a trypan blue quenching assay, confocal microscopy, and transmission electron microscopy. TAT-conjugation strongly increased binding and cellular uptake of lyophilisomes in a time-dependent manner in vitro, as assessed by FACS. These results were confirmed by confocal microscopy. Transmission electron microscopy indicated rapid cellular uptake of TAT-conjugated lyophilisomes via phagocytosis and/or macropinocytosis. In conclusion, TAT-peptides conjugated to albumin-based lyophilisomes are able to enhance cellular uptake of lyophilisomes in HeLa cells.