Fabrication of a Completely Biological and Anisotropic Human Mesenchymal Stem Cell-Based Vascular Graft

Self-Organization of Long-Lasting Human Endothelial Capillary-Like Networks Guided by DLP Bioprinting

Tissue engineering holds great promise for regenerative medicine, drug discovery, and as an alternative to animal models. However, as soon as the dimensions of engineered tissue exceed the diffusion limit of oxygen and nutriments, a necrotic core forms leading to irreversible damage. To overcome this constraint, the establishment of a functional perfusion network is essential. In this work, digital light processing bioprinting is used to encapsulate endothelial progenitor cells (EPCs) in 3D light-cured hydrogel scaffolds to guide them toward vascular network formation. In these scaffolds, EPCs proliferate and self-organize within a few days into branched tubular structures with predefined geometry, forming capillary-like vascular tubes or trees of diameters in the range of 10 to 100 µm. Presenting a confluent monolayer wall of cells strongly connect by tight junctions around a central lumen-like space, these structures can be microinjected with a fluorescent dye and are stable for several weeks in vitro. These endothelial structures can be recovered and manipulated in an alginate patch without altering their shape or viability. This approach opens new opportunities for future applications, such as stacking with other cell sheets or multicellular constructs to yield bioengineered tissue with higher complexity and functionality.

Engineering Organ-on-a-Chip Systems for Vascular Diseases

Vascular diseases, such as atherosclerosis and thrombosis, are major causes of morbidity and mortality worldwide. Traditional in vitro models for studying vascular diseases have limitations, as they do not fully recapitulate the complexity of the in vivo microenvironment. Organ-on-a-chip systems have emerged as a promising approach for modeling vascular diseases by incorporating multiple cell types, mechanical and biochemical cues, and fluid flow in a microscale platform. This review provides an overview of recent advancements in engineering organ-on-a-chip systems for modeling vascular diseases, including the use of microfluidic channels, ECM (extracellular matrix) scaffolds, and patient-specific cells. We also discuss the limitations and future perspectives of organ-on-a-chip for modeling vascular diseases.

Construction of spider silk protein small-caliber tissue engineering vascular grafts based on dynamic culture and its performance evaluation

Tissue engineering is an alternative method for preparing small-caliber (<6 mm) vascular grafts. Dynamic mechanical conditioning is being researched as a method to improve mechanical properties of tissue engineered blood vessels. This method attempts to induce unique reaction in implanted cells that regenerate the matrix around them, thereby improving the overall mechanical stability of the grafts. In this study, we used a bioreactor to seed endothelial cells and smooth muscle cells into the inner and outer layers of the electrospun spider silk protein scaffold respectively to construct vascular grafts. The cell proliferation, mechanical properties, blood compatibility and other indicators of the vascular grafts were characterized in vitro. Furthermore, the vascular grafts were implanted in Sprague Dawley rats, and the vascular grafts' patency, extracellular matrix formation, and inflammatory response were evaluated in vivo. We aimed to construct spider silk protein vascular grafts with the potential for in vivo implantation by using a pulsating flow bioreactor. The results showed that, when compared with the static culture condition, the dynamic culture condition improved cell proliferation on vascular scaffolds and enhanced mechanical function of vascular scaffolds. In vivo experiments also showed that the dynamic culture of vascular grafts was more beneficial for the extracellular matrix deposition and anti-thrombogenesis, as well as reducing the inflammatory response of vascular grafts. In conclusion, dynamic mechanical conditioning aid in the resolution of challenges impeding the application of electrospun scaffolds and have the potential to construct small-caliber blood vessels with regenerative function for cardiovascular tissue repair.