Peritoneal pre-conditioning impacts long-term vascular graft patency and remodeling.

There are questions about how well small-animal models for tissue-engineered vascular grafts (TEVGs) translate to clinical patients. Most TEVG studies used grafting times ≤6 months where conduits from generally biocompatible materials like poly(ε-caprolactone) (PCL) perform well. However, longer grafting times can result in significant intimal hyperplasia and calcification. This study tests the hypothesis that differences in pro-inflammatory response from pure PCL conduits will be consequential after long-term grafting. It also tests the long-term benefits of a peritoneal pre-implantation strategy on rodent outcomes. Electrospun conduits with and without peritoneal pre-implantation, and with 0 % and 10 % (w/w) collagen/PCL, were grafted into abdominal aortae of rats for 10 months. This study found that viability of control grafts without pre-implantation was reduced unlike prior studies with shorter grafting times, confirming the relevance of this model. Importantly, pre-implanted grafts had a 100 % patency rate. Further, pre-implantation reduced intimal hyperplasia within the graft. Differences in response between pure PCL and collagen/PCL conduits were observed (e.g., fewer CD80+ and CD3+ cells for collagen/PCL), but only pre-implantation had an effect on the overall graft viability. This study demonstrates how long-term grafting in rodent models can better evaluate viability of different TEVGs, and the benefits of the peritoneal pre-implantation step.

Identification of Prognostic Biomarker Candidates Associated With Melanoma Using High-Dimensional Genomic Data.

Survival of patients with metastatic melanoma varies widely. Melanoma is a highly proliferative, chemo-resistant disease. With the recent availability of immunotherapies such as checkpoint inhibitors, durable response rates have improved but are often still limited to 2-3 years. Response rates to treatment range from 30 to 45% with combination therapy however no improvement in overall survival is frequently observed. Of the available therapies, many have targeted the BRAFV600E mutation that results in abnormal MAPK pathway activation which is important for regulating cell proliferation. Immune checkpoint inhibitors such as anti-PD-1 and anti-PD-L1 offer better success but response rates are still low. Identifying biomarkers to better target those who will respond and identify the right combination of treatment is the best approach. In this study, we utilize data from the Cancer Cell Line Encyclopedia (CCLE), including 62 samples, to examine features of gene expression (19K+) and copy number (20K+) in the melanoma cell lines. We perform a clustering analysis on the feature set to assess genetically similarity among the cell lines. We then discover which specific genes and combinations thereof maximize cluster density. We design a feature selection approach for high-dimensional datasets that integrates multiple disparate machine learning techniques into one cohesive pipeline. Our approach provides a small subset of genes that can accurately distinguish between the clusters of melanoma cell lines across multiple types of classifiers. In particular, we find only the 15 highest ranked genes among the original 19 K are necessary to achieve perfect or near-perfect test split classification performance. Of these 15 genes, some are known to be linked to melanoma or other cancer progressions, while others have not previously been linked to melanoma and are of interest for further examination.

Peritoneal pre-conditioning reduces macrophage marker expression in collagen-containing engineered vascular grafts.

Engineered vascular grafts have shown promise as arteriovenous shunts, but they have not yet progressed to clinical trials for coronary arteries <4 mm in diameter such as the coronary arteries. Control over initial biomaterial properties and remodeling are necessary to generate viable grafts. In this study, we blended collagen with a synthetic material, poly(ε-caprolactone), to modulate the post-grafting inflammatory response while avoiding aneurysmal-like dilation and failure that can occur with pure collagen grafts. We also used pre-implantation in an "in vivo bioreactor" to recruit autologous cells and improve patency after grafting. Electrospun conduits were pre-implanted within rat peritoneal cavities and then grafted autologously into abdominal aortae. Conduit collagen percentages and pre-implantation were tested for their impact on graft remodeling and patency. Burst pressures >2000 mmHg, reproducible expansion with systole/diastole, and maintenance of mechanical integrity were observed. More importantly, peritoneal pre-implantation reduced overall lipid oxidation, intimal layer thickness, and expression of an M1 macrophage marker. The condition with the most collagen, 25%, exhibited the lowest expression of macrophage markers but also resulted in a thicker intimal layer. Overall, the 10% collagen/PCL with peritoneal pre-implantation condition appeared to exhibit the best combination of responses, and may result in improved clinical graft viability. STATEMENT OF SIGNIFICANCE: This manuscript describes a rodent study to systematically determine the benefits of both pre-implantation in the peritoneal cavity and specific ratios of collagen on engineered vascular graft viability. We show that pre-implantation had a significant benefit, including decreasing the expression of macrophage markers and reducing lipid oxidation after grafting. This study is the first time that the benefits of peritoneal pre-implantation have been compared to an "off the shelf," directly grafted control condition. We also demonstrated the importance of specific collagen ratio on the response after grafting. Overall, we feel that this article will be of interest to the field and it has the potential to address a significant clinical need: a graft for coronary arteries <4 mm in diameter.