Smooth muscle metaplasia and innervation in interstitium of endometriotic lesions related to pain.

OBJECTIVE

To investigate the pathogenesis of endometriotic pain.

DESIGN

Retrospective nonrandomized immunohistochemical study.

SETTING

A university hospital, Department of Gynecology.

PATIENT(S): Twenty human endometriotic specimens were selected from different lesions including ovarian endometrioma, peritoneal lesion, and deep infiltrating lesion. Premenopausal women with histologically diagnosed endometriosis were selected (mean age 39 years; range, 25-53 years). The chief complaint was dysmenorrhea, dyschezia, and dyspareunia. A rat endometriosis model was induced in 10 SLC-Sprague-Dawley rats (8 weeks old) by surgical autotransplantation of the uterus.

INTERVENTION(S): Immunohistochemical staining of endometriotic specimens for alpha-smooth muscle actin (ASMA), neural cell adhesion molecule (NCAM), and nerve growth factor (NGF) expression.

MAIN OUTCOME MEASURE(S): Comparison of the immunoreactive staining of ASMA, NCAM, and NGF expression in human endometriosis and a rat endometriosis model.

RESULT(S): Morphological analysis revealed thick interstitium in both human and rat endometriotic lesions. The major components of fibrotic interstitium are smooth muscle cells, stained by anti-ASMA antibody, and nerve cells, stained by anti-NCAM antibody. Inflammatory cells are also present (e.g., macrophages and lymphocytes) as revealed by anti-NGF antibody staining.

CONCLUSION(S): These results suggest that the contraction of smooth muscle cells and the hyperalgia derived from innervation in the interstitial area is related to pain in endometriosis.