Electrospun Fibrous Mats With Plasmid Loadings As Potential Scaffolds For Vascular Tissue Engineering

Electrospinning has become the most popular technique in recent years by the use of static electricity to draw fibers from a polymer solution or melt. Electrospinning generates uniform and continuous fibers with diameters down to a nanoscale dimension, which closely mimic the size scale of fibrous proteins found in natural extracellular matrix (ECM), and have a very high fraction of surface available to interact with cells. Therefore, electrospun fibers have gained popularity with the tissue engineering community as potential scaffolds for regeneration of cartilage, bone, skin, and blood vessels.As for the tissue engineering scaffolds, the fiber degradation is essential to enhance the ingrowth of new tissue, while the degradation rates should be matched with the rate of neo-tissue formation so as to provide a smooth transition of the load from the scaffold to the tissue. Therefore, the biodegradability should be individually tailored to meet the requirements of specific application when considering using electrospun fibers in biomedical areas. The present study aims to comprehensively investigate the effects that cells and in vivo implantation have on the degradation behaviors, compared with commonly processed degradation in buffer solutions. During the investigational time period, there was no significant difference in the degradation behaviors after incubation fibrous mats into phosphate buffer saline, simulated body fluid and cell culture media. However, significantly higher mass loss of fibrous mats, lower molecular weight reduction and less significant increase in the molecular weight polydispersity were found after inoculation of cells into degradation environment. After cell seeding on the fibrous mats, the tight attachment of cells on fibers further enhanced the degradation process. Compared with in vitro cell-free degradation medium, the subcutaneous implantation of fibrous mats led to significantly higher degradation rate at the initial stage, but slower degradation at the later stage. It was indicated that the degradation behaviors after in vivo implantation was close to those after cell culture on fibrous mats, thus providing an effective in vitro tool to predict in vivo degradation profiles of electrospun fibers, and helping researchers match them with specific purposes.One of the most important issues for engineered tissues is the vascularization of the constructs, since a tissue that is more than a few millimeters in size generally cannot survive by only the diffusion of nutrients and metabolic products. Hence, acceleration of the angiogenesis rate is urgently required.Core-shell structured fibers encapsulated pDNA encoding vascular-endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) or both of them were prepared by emulsion electrospining. In vitro release study indicated that the core-shell structure inhibited the burst elease and prvide a sustained release of pDNA for around 1 month. Human umbilical vein endothelial cells (HUVEC) were seeded on pDNA-loaded firbousscaffolds, indicating the capabilities of promoting endothelial cell proliferation and ECM secretion by the autocrine of growth factors, compared with pDNA-infiltrared fibrous mats. An effective cell transfection and target protein expression proceeded for over 28 d. The pDNA-loaded fibrous scaffolds were subcutaneously implanted into rats to study their angiogenesis via macroscopic observation, hematoxylin-eosin staining and immunohistochemical staining. The results demonstrated that the incorporation of pDNA polyplexes could effectively enhance the angiogenesis of the implanted fibrous mats, demonstrating the potential application as scaffolds in vascular tissue engineering.