Intra-arterial photodynamic therapy using 5-ALA in a swine model

Abstract

To test the hypothesis that intravascular light could be delivered via a balloon catheter for arterial photodynamic therapy (PDT). Pig non-injury model. Clinical catheter equipment. Large White pigs (15-20 micrograms) were photosensitised with 5-aminolaevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) at a concentration of 120 mg/kg. Arterial biopsies were taken at intervals between 30 mins and 24 h and frozen sections analysed using a CCD camera to give a temporal profile of fluorescence in each arterial layer. PDT was given to normal arterial segments via a 4 mm transparent PTA balloon inflated so as to occlude flow, but not distend the artery. Animals were culled at 3 and 14 days and the above segments harvested. Fluorescence peaked in the adventitia, intima and medial layers at 1.5, 4 and 6 h respectively. PDT at all time points produced VSMC depletion compared with controls. The degree of depletion mirrored the fluorescence profile of PpIX. PDT can be delivered via a standard PTA balloon with a transparent channel. This depletes the VSMC population within the arterial wall without complications. Intra-arterial PDT is therefore a potential therapy to reduce the incidence of restenosis post-angioplasty.