Impact Of Photodynamic Therapy On The Normal Vocal Cord Injury

ObjectTo investigate the reactive characteristics of normal vocal cord tissues to photodynamic therapy(PDT) and the damage effects of different concentration of photosensitizer and different light on normal rabbit vocal cord.Photodynamic Therapy application for safe dose on the vocal cord,and making the preliminary research of PDT in clinical treatment of chronic inflammation of the vocal cords and precancerous lesions. Method25 healthy Japanese big ear experimental rabbits were randomly divided into 5 groups: low work rate low concentration group A(100 mW,10%5-ALA), high work rate low concentration group B(200 mW,10%5-ALA), high work rate high concentration group C(200 mW,20%5-ALA), low work rate high concentration group D(100 mW,20%5-ALA) and normal control group E.The issue damage and wound recovery were observed in 1 d, 3 d, 7 d, 14 d, 28 d after intervention. Histomorphology changes of the sampled vocal cords were observed using light microscope and transmission electron microscopy. and the changes of collagenous fiber, hyaluronic acid and fibronectin of ECM(extra cellular matrix, ECM) were observed using Masson staining, immunohistochemical staining, Alican blue staining to observe the vocal cord injury and repair. ResultsA severe inflammation reaction was observed in group A, B, C, D after intervened with PDT compared to normal group. The reaction of A group was lighter, and the reaction of C group was the most serious. The content of collagenous fiber, hyaluronic acid and fibronectin in vocal fold lamina layer was significantly higher than that in normal group(P<0.05). Different degrees of fiber proliferation were observed in all groups. The content of each component of vocal fold lamina layer tended to be normal slightly higher level in 28 d. Observation by electron microscope showed that there were no significant differences in A, B, C, D, E in 28 d after intervention. ConclusionsRecoverable damage repair process can be detected in rabbit vocal cord after intervened with PDT, which began in 7d and basically completed in 28 d. In a certain concentration(10%-20%) and dose range(100-200 mW).The higher of photodynamic dose, the more serious of the damage. And the damage was basically reversible.