Electrospun Small‐Diameter Polyurethane Vascular Grafts: Ingrowth and Differentiation of Vascular‐Specific Host Cells

Abstract

No small-diameter synthetic graft has yet shown comparable performance to autologous vessels. Synthetic conduits fail due to their inherent surface thrombogenicity and the development of intimal hyperplasia. In addressing these shortcomings, electrospinning offers an interesting alternative to other nanostructured, cardiovascular substitutes because of the close match of electrospun materials to the biomechanical and structural properties of native vessels. In this study, we investigated the in vivo behavior of electrospun, small-diameter conduits in a rat model. Vascular grafts composed of polyurethane were fabricated by electrospinning. Prostheses were implanted into the abdominal aorta in 40 rats for either 7 days, 4 weeks, 3 months, or 6 months. Retrieved specimens were evaluated by histology, immunohistochemical staining, confocal laser scanning microscopy, and scanning electron microscopy. At all time points, we found no evidence of foreign body reaction or graft degradation. The overall patency rate of the intravascular implants was 95%. Within 7 days, grafts revealed ingrowth of host cells. CD34+ cells increased significantly from 7 days up to 6 months of implantation (P < 0.05). Myofibroblasts and myocytes showed increasing cell numbers up to 3 months (P < 0.05). Ki67 staining indicated unaltered cell proliferation during the whole follow-up period. Besides biomechanical benefits, electrospun polyurethane grafts exhibit excellent biocompatibility in vivo. Cell immigration and differentiation seems to be promoted by the nanostructured artificial matrix.

Healing characteristics of electrospun polyurethane grafts with various porosities

“…In previous studies using electrospun grafts with median pore sizes of $2 lm and a void fraction of 71% we have seen infiltration of vascular-specific cells into the graft wall [15]. We observed by TEM that cells change their shapes to cleave to the fibrous mats.…”

“…However, the majority of cells remained at the outer half of the prosthesis. After long-term implantation, these grafts revealed decreased numbers of myofibroblasts and myocytes, and changes in morphological features of the host cells were evident [15].…”

Nanotechnologies in tissue engineering

“…Bergmeister et al evaluated vascular grafts composed of PU with an inner diameter of 1.5 mm and a mean wall thickness of 70 mm [60] . They used the rat abdominal aorta model to investigate their in vivo biocompatibility after 1 week, 1, 3, and 6 months.…”

Electrospinning of aligned fibers with adjustable orientation using auxiliary electrodes

“…Pellethane R 2363 80-A polyurethane is a thermoplastic copolymeric elastomer that is commonly used for medical devices and electrospinning experiments [30,31]. It is physically crosslinked by extensive hydrogen bonding involving a soft block and hard block, where the former is poly(tetramethylene ether)glycol while the latter is an urethane comprised of tetramethylene ether glycol and diphenylmethan-4,4 -diisocyanat [30,32].…”