In Vivo Observation of Endothelial Cell-Assisted Vascularization in Pancreatic Cancer Xenograft Engineering

In this study, for better understanding of patient-derived xenograft (PDX) generation, angiogenic characteristics during PDX cancerous tissue generation was investigated with different initial cell seeding conditions in the hydrogel. We monitored the angiogenic changes during the formation of in vivo cancer cell line xenografts induced by endothelial cells. Our in vivo cancer tissue formation system was designed with the assistance of tissue engineering technology to mimic patient-derived xenograft formation. Endothelial cells and MIA PaCa-2 pancreatic carcinoma cells were encapsulated in fibrin gel at different mixing configurations and subcutaneously implanted into nude mice. To investigate the effect of the initial cancerous cell distribution in the fibrin gel, MIA PaCa-2 cells were encapsulated as a homogeneous cell distribution or as a cell aggregate, with endothelial cells homogeneously distributed in the fibrin gel. Histological observation of the explanted tissues after different implantation periods revealed three different stages: isolated vascular tubes, leaky blood vessels, and mature cancerous tissue formation. The in vivo engineered cancerous tissues had leaky blood vessels with low expression of the vascular tight junction marker CD31. Under our experimental conditions, complex cancer-like tissue formation was most successful when tumorous cells and endothelial cells were homogeneously mixed in the fibrin gel. The present study implies that tumorous xenograft tissue formation can be achieved with a low number of initial cells and that effective vascularization conditions can be attained with a limited volume of patient-derived cancer tissue. Endothelial cell-assisted vascularization can be a potent choice for the effective development of vascularized cancerous tissues for studying patient-derived xenografts, cancer angiogenesis, cancer metastasis, and anticancer drugs.

In Vitro Quantification of the Radiopacity of Onyx during Embolization / 신경중재치료의학

PURPOSE: Onyx has been successfully applied in the treatment of various neurovascular lesions. However, some experience is required to get accustomed to its unpredictable fluoroscopic visibility during injection. This in vitro study aimed to evaluate the characteristics of radiopacity change in a simulated embolization procedure. MATERIALS AND METHODS: Using a bench-top Onyx injection experiment simulating a typical brain arteriovenous malformation embolization, nine cycles of casting modes (continuous injection) and plugging modes (injection with intermittent pauses) were performed. Radiodensity of Onyx droplets collected from the microcatheter tip and the distal head portion of the microcatheter were measured as time lapsed. Distribution of droplet radiodensity (radiodensity) and distribution of radiographic grade (grade) were analyzed and compared by repeated measurements. RESULTS: Within-group analysis revealed no significant radiodensity change with time (P>0.05). The radiodensity was significantly higher in the casting mode than in the plugging mode (P<0.01). The lateral radiograph of the microcatheter showed higher radiopacity (P<0.01) and better evenness (P<0.01) in the casting mode than in the plugging mode. A significant difference in microcatheter attenuation (both radiographic grade mean and SD; P<0.01) was noted between the two modes. Radiodensity had a significant influence on the radiopacity and radiopacity evenness of the microcatheter. CONCLUSION: The radiopacity of the Onyx can vary significantly over time because of early precipitation of tantalum powder. Radiopacity decreased significantly during plugging modes, characterized by pauses between injections.

Multilayered Engineered Tissue Sheets for Vascularized Tissue Regeneration

A major hurdle in engineering thick and laminated tissues such as skin is how to vascularize the tissue. This study introduces a promising strategy for generatingmulti-layering engineered tissue sheets consisting of fibroblasts and endothelial cells co-seeded on highly micro-fibrous, biodegradable polycaprolactone membrane. Analysis of the conditions for induction of the vessels in vivo showed that addition of endothelial cell sheets into the laminated structure increases the number of incorporated cells and promotes primitive endothelial vessel growth. In vivo analysis of 11-layered constructs showed that seeding a high number of endothelial cells resulted in better cell survival and vascularization 4 weeks after implantation.Within one week after implantation in vivo, red blood cells were detected in the middle section of three-layered engineered tissue sheets composed of polycaprolactone/ collagen membranes. Our engineered tissue sheets have several advantages, such as easy handling for cell seeding, manipulation by stacking each layer, a flexible number of cells for next-step applications and versatile tissue regeneration, and automated thick tissue generation with proper vascularization.