THE CONTRASTING MECHANISMS OF COLONIC COLLAGEN DAMAGE BETWEEN PHOTODYNAMIC THERAPY and THERMAL INJURY

Abstract

Abstract The colon is protected from disruption and bursting pressures by the submucosal collagen layer. Photodynamic therapy with aluminium sulphonated phthalocyanine (AlSPc) does not cause perforation or reduction in the bursting strength of the rodent colon despite causing full thickness damage. Thermal injury also produces full thickness necrosis but causes perforation and considerably reduces the bursting strength of the colon. The differing mechanisms of damage were examined. Using transmission electron microscopy we examined collagen from undamaged normal rodent colon, colon damaged by photodynamic therapy and thermally injured colon. Following photodynamic therapy collagen maintained its architecture and periodicity. Thermally damaged collagen became grossly swollen and lost its fibrillary architecture. We have concluded that photodynamic therapy with AlSPc is collagen sparing.