Limitations of rat carotid balloon de-endothelialization model in arterial photodynamic therapy: a study using 5-aminolaevulinic acid

Photodynamic therapy (PDT) effectively inhibits fibrocellular intimal hyperplasia (FCIH) two and four weeks after arterial traction balloon injury in rat carotid arteries. The aim of the present study was to assess the long term effects of PDT in this rat model of FCIH. 5- aminolaevulinic acid-induced protoporphyrin IX was used to sensitize rats for PDT after traction balloon arterial injury to the whole of the left common carotid artery. Rats were sacrificed at intervals of six to 26 weeks, and perfusion fixed and H and E stained sections were analyzed using computerized morphometry. PDT inhibition of FCIH was only partial at these late times. The amount of FCIH present increased with increasing time after injury. The late occurrence of FCIH appeared to be due to migration of FCIH from balloon injured areas outside the PDT treated field as a result of the traction injury being applied to the whole carotid. We recommend segmental balloon injury rather than the traction injury of the whole common carotid injury for future studies in this model.