Endovascular photodynamic therapy inhibits intimal hyperplasia after PTA in a rat model

Background: Vascular restenosis due to intimal hyperplasia (IH) and negative vascular remodeling (shrinkage) attenuates long-term patency of interventions like bypass procedures, endarterectomies and PT(C)As. Endovascular photodynamic therapy (PDT) may be an adjuvant approach based on intracellular photoactivation of 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PP IX) resulting in local cytotoxicity. Aim: To prevent restenosis by inhibiting IH with endovascular PDT. Methods: Male Wistar rats (n equals 33) were subdivided into two groups; one experimental group; the PTA + PDT group (N equals 18), in which illumination with either 0, 12.5, 25 and 50 J/cm diffuser length was applied at 100 mW/cm diffuser length; one control group; the PTA group in which IH was induced after balloon denudation of the right iliacal artery (n equals 15). Results: Morfometric analysis showed that IH developed from 0.02 plus or minus 0.02 mm 2 at 1 week to 0.13 plus or minus 0.04 mm 2 at 4 weeks in the PTA group. In the PTA + PDT-group with 50 J/cm diffuser length still no IH (0.002 plus or minus 0.003 mm 2 ) developed after 4 weeks. Conclusion: Endovascular PDT prevents formation of IH measured 4 weeks post PTA. An optimal light dosimetry of 50 J/cm diffuser length at 3 hours after ALA application was found in this IH model. Therefore, endovascular PDT is a promising therapy to prevent restenosis after vascular interventions.