Research Projects

Regeneration of functional blood vessels with integrated vascular networks faces major limitations that restrict their clinical translation. Although large-diameter vascular grafts (more than 5 mm) are clinically available, they are typically composed only of endothelial cells, which limits proper cellular alignment, organization, and functional integration. This lack of complexity also restricts their ability to sprout new vessels (angiogenesis) and integrate effectively with host tissue. Small-diameter vascular grafts offer a promising alternative by enabling the creation of vascular networks within engineered tissues for clinical applications. However, the most common fabrication techniques for small-diameter grafts—such as electrospinning and 3D printing present major challenges. It is difficult to fabricate these grafts with single or multiple cell types and seeding cells onto scaffolds often results in poor alignment and organization. This limits cell–cell interactions and reduces the functional performance of the engineered blood vessel. Although 3D bioprinting has advanced the creation of macro-vascular structures with defined geometries, the development of small-diameter vascular grafts that incorporate multiple cell types and precise cell organization remains a significant challenge. For in vitro vascular grafts, it is essential to add multiple cell types and design the extracellular matrix (ECM) composition to regulate cell alignment and organization in response to flow dynamics. Additionally, post-processing of the graft must maintain bioactivity, functionality, strength, degradability, and vascular permeability. To address these challenges, the proposed project aims to develop electrically responsive, ECM-mimicking microtubular scaffolds using co-axial 3D bioprinting. This approach uses a dual-ink system, where the core contains a sacrificial ink (Pluronic F127) that is washed out with multiple PBS rinses to create a hollow microtubular structure. The outer shell, composed of kappa-carrageenan methacrylate (k-CAMA), GelMA (Gelatin methacrylate) and GelMA-polypyrrole (GelMA-PPy), provides structural integrity and stability. Within this polymeric composition, multiple cell types are organized: human umbilical vein endothelial cells (HUVECs) are placed in the core, while adipose-derived stem cells (ADSCs) and C2C12 myoblasts are positioned in the shell, enabling vascular-muscle tissue integration within a single construct. ADSCs will differentiate into muscle cells under the influence of myoblasts cells and electrical stimulation. Electrical stimulation will also modulate mechanotransduction pathways, promote cell alignment, enhance both myogenic and endothelial differentiation, and encourage cell-cell interactions and collagen matrix formation. Additionally, a dynamic culture system that mimics physiological environments will be established by fabricating a PDMS chamber with a gradient of CaO₂ to provide varying oxygen concentrations. At the base, a GelMA hydrogel loaded with NIH-3T3 fibroblast cells will respond to the oxygen gradient by releasing VEGF and collagen, stimulating HUVEC invasion and matrix deposition. The dynamic system will be controlled by an axial rocking mechanism, circulating VEGF and other growth factors to promote vascular network formation. The hypothesis is that a tri-culture system, supported by co-axial spatial cell arrangement, external electrical cues, and biochemical gradients, will result in a functional, small-diameter vascular graft with enhanced cellular alignment, integration, and long-term viability. The expected outcomes are small-diameter vascular grafts with muscle–endothelial cell integration, exhibiting optimal bioactivity, mechanical strength, biodegradability, and vascular permeability. The research goals highlighted with challenges addressed have been added into the illustrative picture as Goal I and Goal II.