Biodegradable small calibre polydioxanone-based vascular prostheses: Potential as coronary bypass grafts

Aims: Shelf-ready synthetic small calibre prostheses are needed for coronary artery bypass grafting. Biodegradable scaffolds resistant to degradation-induced aneurysm formation in the systemic arterial circulation have been developed for in vivo vascular tissue engineering. Our aim is to evaluate patency, biocompatibility and mechanical properties (remodelling) of 3 electrospun biodegradable random nano-fibre polymer prostheses: polydioxanone (PDO) alone; blended with: poly(lactic-acid) (PDO-PLA); with polycaprolactone (PDO-PCL). Methods: In 30 anaesthetised Sprague Dawley rats, 2mm ePTFE grafts controls (n=9), PDO (n=3), PDO-PLA (n=9) and PDO-PCL (n=9), were interposed in the infrarenal abdominal aorta and followed for 3, 6 and 12 weeks. Digital substraction angiography was performed for patency, stenosis and aneurysmal dilatation before euthanasia. Grafts were then harvested for SEM, histology and computed morphometry for assessment of neoendothelialisation (% of the whole graft length) and intimal hyperplasia (micrometer 2 /micrometer). Results: Patency rates were excellent for all types of grafts (100%) and no relevant stenoses were found. Angiography follow-up showed aneurysmal formation for all PDO-alone grafts at 3 weeks (therefore no further implantations were made) and 1/3 for PDO-PLA at 6 and 12 weeks. No aneurysms were found for PDO-PCL grafts. All PDO-based grafts show slow degradation, a significantly better neoendothelialisation and insignificant neointimal formation compared to ePTFE. Results after 12 weeks implantation: (*p<0.05 vs. ePTFE; Mann Whitney U test) Prostheses Aneurysm Occurrence Endothelialisation (%) Intimal Hyperplasia (µm 2 /µm) ePTFE(Control) 0/3 53±20 16±9 PDO-PLA 1/3 97±4* 86±38 PDO-PCL 0/3 99±1* 91±23 Conclusions: Patency of electrospun biodegradable PDO-based prostheses is excellent. Using slow, biodegrading polymer blends, e.g. PDO-PCL can avoid aneurysm formation and the neoendothelialisation (blood compatibility) of such prostheses is significantly better compared to ePTFE. Therefore, biodegradable, electrospun PDO-based vascular prostheses may be a promising alternative as shelf-ready cardiopulmonary bypass grafts.