Comparative study of three vascular grafts produced by electrospinning in vitro and in vivo

Objective. The study focused on the production and evaluation of small-diameter vascular grafts (less than 6 mm) by using an electrospinning approach. Methods. The protocols of vascular grafts (VG) to be produced from the solutions of synthetic polymers and their blends with gelatin including those with a semipermeable inner layer were developed. The comparative study of the grafts in vitro and in vivo was carried out. The resistance of VG to displacement, suture retention, layers snagging and compatibility with native artery walls were studied. Also assessed was the time of hemostasis when implanting the grafts consisting of various mixes of polymers, as well as their biocompatibility at different stages of observation. Results. VG produced by electrospinning and containing a semipermeable inner layer possess satisfactory mechanical properties, such as suture retention, resistance to displacement, stability during long term pulsatile stress, do not snag during implantation and form a tight contact with native artery walls. A histological study demonstrates active remodeling of VG including the growth of inner structure typical of a vessel, medium collagen/elastin layer with smooth muscle cells and synthetic fibers and an outer connective tissue capsule without any signature of inflammation. An immunohistochemical study demonstrates more efficient accumulation of smooth muscle cells in VG produced from polycaprolactone (PCL) as compared to other VG tested. VG produced from the PCL-gelatin blend and containing an inner semipermeable layer, as well as similar VG containing polylactic-co-glycolic acid (PLGA) in the inner semipermeable layer tended to produce an endothelial inner layer faster as compared to VG from PCL. However, VG with PLGA acid had a tendency to loose endothelial cells, possibly due to PLGA degradation. VG produced from PCL-gelatin blend and containing the inner semipermeable layer demonstrate limited accumulation of smooth muscle cells and progressive settlement with endothelial cells. Conclusion. A comparative study of different VG produced by electrospinning enables to select variants of polymeric composition and structure of the implant that provide the best bio- and hemocompatibility. VG produced by electrospinning from PCL-gelatin blend and supplied with a semipermeable layer can be recommended for subsequent clinical approbation.