posted on 2022-11-16, 11:42authored byDaniel Nicholas Martin Coakley
Existing synthetic vascular grafts have unacceptably high failure rates when
replacing below knee arteries. In vitro endothelialisation is an emerging procedure
that has been shown to enhance the patency rates of below knee synthetic vascular
grafts. Here autologous endothelial cells are harvested and cultured on the lining of
the graft prior to implantation. The technique is limited by the narrow time frame
availalble for culture and the finite cells obtainable following harvest. As well as
this, existing synthetic materials are poor cellular substrates and must be combined
with coatings to promote cellular growth and attachment. The most common coated
graft used clinically is fibrin-coated polytetrafluoroethylene (ePTFE).
The study aim was to compare the endothelialisation of fibrin-coated ePTFE
with emerging novel extracellular matrix (ECM) scaffolds, which we hypothesise
will provide a superior substrate for cell growth by mimicking the in vivo
environment more closely. We also construct and verify a novel subatmospheric
bioreactor in order to enhance the proliferation of cultured cells. Finally, we examine
the culturing of endothelial cells inside the lumen of small diameter ECM vascular
grafts.
Our Results showed that cells remained viable and produced von Willebrand
factor on all substrates tested. There was no difference in adhesion rates between
ECM scaffolds and fibrin-coated ePTFE (p = 1.00). Endothelial cells proliferated
fastest on ECM scaffolds when compared to all other materials tested (p <0.001).
When seeded scaffolds were exposed to subatmospheric pressures in a closed
bioreactor a mechanical strain was exerted on the construct. This was shown to alter
cellular morphology and enhance cellular proliferation. We found we could rapidly
form a confluent endothelial lining on the luminal surface of small diameter ECM
grafts.
In conclusion, ECM bioscaffolds offer a superior substrate for promoting rapid
endothelialisation compared to existing fibrin-coated ePTFE by combining firm
cellular anchorage and rapid cell expansion. Proliferation rates were positively
influenced by a subatmospheric bioreactor. This work suggests that ECM materials
are promising scaffolds for use in small vessel tissue engineering.