Progressional Construction of Freestanding Perfusable Microvasculature

Microvasculature is essential to connect main blood vessels to smaller capillary networks throughout the body. As with all vasculature, these structures can be impaired due to disease or injury, and their reconstruction is imperative to ensure the patient’s health. However, most regeneration studies to date have focused on inducing or engineering either small capillary beds or large arteries and veins. Previously we developed a system to study microvasculature development guided on electrospun fibrin hydrogel microfibers. The focus of this work was to utilize this biomaterial to develop freestanding perfusable microvascular structures, a feat that has not been achieved to date. Progenitor endothelial cells and vascular smooth muscle cells were seeded onto microfibers to create a robust cell layer before applying a degradation treatment to remove the microfiber core, creating a perusable structure. We used this seeding protocol on three different set ups throughout the study to create our microvascular structures. The first set up relied on the scaffold using a frame for support. The scaffolds on frames were used to test if the cell layers would be damaged by the degradation treatments, which were then used to achieve luminal formation. When lumen formation was created without damage to the cell layers, we conducted the second set of experiments in two different devices. These devices allowed the scaffold to be freestanding and to support the growth of a robust cell layer. However, full degradation of the scaffold could not be obtained on cellularized microfibers due to a thick cell layer that prevented plasmin diffusion. Therefore, the shape of the microfibers was altered to allow direct perfusion via a hollow structure. With the use of direct perfusion, the hollow microfibers allowed for a cellular structure to grow with a distinct lumen. This engineered microvasculature has the potential of creating patient specific perusable structures for cell therapy and drug delivery testing