Canine carotid allograft changes after photochemotherapy and external polyester sheathing

The purpose of this study is to define and refine the changes in canine carotid allografts after photochemotherapy and polyester sheathing. Photochemotherapy with 8-methoxy psoralen (8MOP) and UVA (PUVA) was given alone or combined with intraluminal visible light (VL) 450 nm in proper dosages to speed the depopulation of endothelial (EC) and smooth muscle cells (SMC) and to modulate the immune response.

Novel apparati were made for photochemotherapy of 19 right canine carotid arterial allografts with 19 paired untreated controls in the left carotid. External UVA and internal visible light (VL 450 nm) were used with 8-methoxy psoralen (8-MOP) as a sensitizer.

With moderate dosage of 8-MOP (1 microg/cc) and 2-4 J/cm2 of external UVA (PUVA), smooth muscle cells (SMC) disappeared faster from the media and fibroblasts (FB) appeared earlier in the adventitia of the treated right allografts, reducing but not eliminating the immune response. Intraluminal VL did not enhance the PUVA effect. At 68 days, treated and control allografts showed similar dimensions with subsided immune reactions. The media thickness was reduced from 0.38 mm to 0.18 mm and the host adventitia increased from 0.22 to 0.60 mm. Variable reactions peaked between two and three weeks and subsided after one month. All allografts remained open with canine carotid i.d.s of 2-3 mm and 80 to 100 cc/ minute arterial flows. Although the UVA dosage was moderate) similar doses sterilized log 7 of staph aureus cultures in saline. The allografts without smooth muscle showed moderate but stable cylindrical dilatation without spasm or stenosis and with an adequate adventitial buttress for a small vessel. A polyester sleeve around four treated grafts was inseparable from the allograft in less than 3 weeks and tolerated well over a 70-day period.

Biodegradable graft sheaths with bioerodible hydrogels with growth factors (FGF) for local delivery may provide a faster and more complete matrix remodeling for a superior conduit in the future.