Evidence of lasting functional destruction of the rat endometrium after 5-aminolevulinic acid-induced photodynamic ablation: prevention of implantation.

Abstract

We evaluated disruption of endometrial function after treatment with 5-aminolevulinic acid with or without light exposure. In a conventional laboratory setting adult Sprague-Dawley female rats were treated with various doses of 5-aminolevulinic acid in one uterine horn and saline in the contralateral horn. Three hours after treatment both uterine horns were exposed to light, and the rats were bred to a fertile male 10 or 60 days later. Ablation of endometrium was evaluated by both rate of implantation and histologic features. In the absence of light exposure 5-aminolevulinic acid had no significant effect on the rate of implantation, compared with saline (76% vs 92%, n = 25, p > 0.05). In contrast, 5-aminolevulinic acid treatment plus light exposure profoundly decreased the rate of implantation in the 5-aminolevulinic acid-treated uterine horns of rats bred 10 days (3.8% vs 100%, n = 26, p < 0.001) or 60 days after treatment (16.7% vs 100%, n = 24, p < 0.001). Histologic examination revealed that the 5-aminolevulinic acid plus light-treated uterine horns were completely devoid of endometrium. Photodynamic treatment with 5-aminolevulinic acid resulted in a persistent disruption of rat endometrial function and was consistent with the histologic evidence of complete endometrial ablation. In addition, a partial destruction of myometrium adjacent to endometrium was observed. The myometrial damage may be through a nonphotodynamic mechanism because myometrium is unable to synthesize protoporphyrin IX from 5-aminolevulinic acid.