High-resolution ultrasound imaging: a novel technique for the noninvasive in vivo analysis of endometriotic lesion and cyst formation in small animal models.

Endometriosis, the presence of endometrial tissue at ectopic sites, is a highly prevalent gynecological disease severely affecting a patient's quality of life. To analyze the mechanisms involved in the disease and to identify new molecular targets for effective therapies, small animal models are an important approach. Herein, we report the first use of high-resolution ultrasound imaging for the in vivo analysis of intraperitoneal endometriotic lesions in mice. This noninvasive technology allows for the repetitive quantitative analysis of growth, cyst development, and adhesion formation of endometriotic lesions with a low intra- and interobserver variability. Moreover, it enables one to easily differentiate between endometrial cysts and stroma. Accordingly, volume measurements of both endometrial cysts and stroma indicated that the initial establishment of endometriotic lesions is associated with enhanced cellular proliferation, followed by a phase of increased secretory activity of endometrial glands. Results of ultrasound analysis correlated well with measurements of lesion volumes by caliper and histology. Importantly, ultrasound imaging could be performed repetitively and noninvasively and reflected best the in vivo situation. The technique could further be demonstrated to successfully monitor the significant inhibition of growth of endometriotic lesions after specific estrogen receptor destabilizator treatment. Thus, high-resolution ultrasound imaging represents an important tool for future preclinical small animal studies, which address the pathophysiology of endometriosis and the development of new treatment strategies.