Longer term assessment of photodynamic therapy for intimal hyperplasia: a pilot study

To determine the potential long term (three or six months) effectiveness of photodynamic therapy (PDT) in reducing intimal hyperplasia in swine.

Intimal hyperplasia in the abdominal aortae of swine was created by a combination of fat-supplemented diet and balloon catheter injury prior to PDT. Swine were randomly allocated into one of three groups which received either: (i) both drug and light (PDT), (ii) drug only, or (iii) light only. Twenty-four hours following administration of the photosensitizer PHOTOFRIN (porfimer sodium) at 2.5 mg/kg, two distinct 1 cm spots on the posterior wall of the abdominal aorta were illuminated by an argon pumped dye laser tuned to 630 nm for an energy fluence of 120 J/cm2. After three or six months, swine were sacrificed, perfusion fixed, and had their aortae removed for light and electron microscopy.

Intimal hyperplasia reduction following PDT persisted for the three or six months follow up period. Experimental vessels receiving PDT showed a 26.0+/-4.5% ( n = 2, ie. four spots) and 30.8+/-5.4% ( n = 1, ie. two spots) smaller percent intimal area after three or six months of recovery, respectively. Control groups receiving either light or drug only showed less than a 6% difference in percent intimal area. Medial and adventitial layers were unaffected in all groups. Electron microscopy demonstrated that the endothelium or endothelial-like cells had regenerated in both the posterior and adjacent areas of the abdominal aortae with no clear difference between them.

These findings suggest that PDT may be beneficial in reducing intimal hyperplasia for up to three or six months in swine.