The fetal porcine aorta and mesenteric acellular matrix as small-caliber tissue engineering vessels and microvasculature scaffold

Comparison of small-diameter decellularized scaffolds from the aorta and carotid artery of pigs

AIM

Tissue-specific extracellular matrix promotes tissue regeneration and repair. We aimed to identify the optimal decellularized matrices for tissue-engineered vascular graft (TEVG).

METHODS

Decellularized aorta of fetal pigs (DAFP, n = 6, group A), decellularized aorta of adult pigs (DAAP, n = 6, group B), and decellularized carotid artery of adult pigs (DCAP, n = 6, group C) were prepared. Scaffolds were compared using histology and ultrastructure. Endothelial cell (EC) and myofibroblast (MFB) infiltration assessments were performed in vitro. Cell infiltration was measured in vivo. Biomechanical properties were also determined.

RESULTS

Almost original cells were removed by the acellularization procedure, while the construction of the matrix basically remained. In vitro, monolayer ECs and multi-layer MFBs were formed onto the internal surface of the specimens after 3 weeks. In vivo, cell infiltration in group A significantly increased at the 6th and 8th week when compared with groups B and C (p < 0.01). The infiltrated cells were mainly MFBs and a few CD4+ T-lymphocytes/macrophages in the specimens. Groups A and B showed greater axial compliance than group C (p < 0.01).

CONCLUSION

DAFP was the most suitable for use as a small-caliber vascular graft.

Concise Review: Patency of Small-Diameter Tissue-Engineered Vascular Grafts: A Meta-Analysis of Preclinical Trials

Several patient groups undergoing small‐diameter (<6 mm) vessel bypass surgery have limited autologous vessels for use as grafts. Tissue‐engineered vascular grafts (TEVG) have been suggested as an alternative, but the ideal TEVG remains to be generated, and a systematic overview and meta‐analysis of clinically relevant studies is lacking. We systematically searched PubMed and Embase databases for (pre)clinical trials and identified three clinical and 68 preclinical trials ([>rabbit]; 873 TEVGs) meeting the inclusion criteria. Preclinical trials represented low to medium risk of bias, and binary logistic regression revealed that patency was significantly affected by recellularization, TEVG length, TEVG diameter, surface modification, and preconditioning. In contrast, scaffold types were less important. The patency was 63.5%, 89%, and 100% for TEVGs with a median diameter of 3 mm, 4 mm, and 5 mm, respectively. In the group of recellularized TEVGs, patency was not improved by using smooth muscle cells in addition to endothelial cells nor affected by the endothelial origin, but seems to benefit from a long‐term (46–240 hours) recellularization time. Finally, data showed that median TEVG length (5 cm) and median follow‐up (56 days) used in preclinical settings are relatively inadequate for direct clinical translation. In conclusion, our data imply that future studies should consider a TEVG design that at least includes endothelial recellularization and bioreactor preconditioning, and we suggest that more standard guidelines for testing and reporting TEVGs in large animals should be considered to enable interstudy comparisons and favor a robust and reproducible outcome as well as clinical translation.

Development and in vivo validation of tissue-engineered, small-diameter vascular grafts from decellularized aortae of fetal pigs and canine vascular endothelial cells

Background

Tissue engineering has emerged as a promising alternative for small-diameter vascular grafts. The aim of this study was to determine the feasibility of using decellularized aortae of fetal pigs (DAFPs) to construct tissue-engineered, small-diameter vascular grafts and to test the performance and application of DAFPs as vascular tissue-engineered scaffolds in the canine arterial system.

Methods

DAFPs were prepared by continuous enzymatic digestion. Canine vascular endothelial cells (ECs) were seeded onto DAFPs in vitro and then the vascular grafts were cultured in a custom-designed vascular bioreactor system for 7 days of dynamic culture following 3 days of static culture. The grafts were then transplanted into the common carotid artery of the same seven dogs from which ECs had been derived (two grafts were prepared for each dog with one as a backup; therefore, a total of 14 tissue-engineered blood vessels were prepared). At 1, 3, and 6 months post-transplantation, ultrasonography and contrast-enhanced computed tomography (CT) were used to check the patency of the grafts. Additionally, vascular grafts were sampled for histological and electron microscopic examination.

Results

Tissue-engineered, small-diameter vascular grafts can be successfully constructed using DAFPs and canine vascular ECs. Ultrasonographic and CT test results confirmed that implanted vascular grafts displayed good patency with no obvious thrombi. Six months after implantation, the grafts had been remodeled and exhibited a similar structure to normal arteries. Immunohistochemical staining showed that cells had evenly infiltrated the tunica media and were identified as muscular fibroblasts. Scanning electron microscopy showed that the graft possessed a complete cell layer, and the internal cells of the graft were confirmed to be ECs by transmission electron microscopy.

Conclusions

Tissue-engineered, small-diameter vascular grafts constructed using DAFPs and canine vascular ECs can be successfully transplanted to replace the canine common carotid artery. This investigation potentially paves the way for solving a problem of considerable clinical need, i.e., the requirement for small-diameter vascular grafts.

Application of bladder acellular matrix in urinary bladder regeneration: the state of the art and future directions

Construction of the urinary bladder de novo using tissue engineering technologies is the “holy grail” of reconstructive urology. The search for the ideal biomaterial for urinary bladder reconstruction has been ongoing for decades. One of the most promising biomaterials for this purpose seems to be bladder acellular matrix (BAM). In this review we determine the most important factors, which may affect biological and physical properties of BAM and its regeneration potential in tissue engineered urinary bladder. We also point out the directions in modification of BAM, which include incorporation of exogenous growth factors into the BAM structure. Finally, we discuss the results of the urinary bladder regeneration with cell seeded BAM.