The rhesus macaque as an animal model for pelvic organ prolapse

OBJECTIVE: The purpose of this study was to characterize the pelvic floor of the rhesus macaque as an experimental model for human pelvic organ prolapse and to initiate an evaluation of the effects of estradiol and progesterone on the rhesus paravaginal attachment. STUDY DESIGN: Histologic specimens were prepared from the paravaginal attachment of 13 oophorectomized rhesus macaques. Three animals were treated with estradiol; 6 animals were treated with estradiol and progesterone, and 4 animals were untreated (hormone deprived). Immunocytochemistry was used to localize steroid receptors in the paravaginal attachment. RESULTS: Spontaneous pelvic organ prolapse was observed in rhesus macaques. The paravaginal attachment is comprised of dense collagen and elastic fibers that infiltrate the levator ani muscle. The fibroblasts of this attachment are estrogen and progesterone receptor positive, and the receptors are hormone responsive. CONCLUSION: The rhesus macaque has pelvic floor anatomy that is similar to women and makes an excellent experimental model for the study of prolapse. The rhesus paravaginal attachment is ligamentous and hormone sensitive. Its fibroblast activity may be modified by estrogen treatment in a manner similar to that reported in human pelvic connective tissue. The connective tissue of the paravaginal attachment interdigitates with the levator ani muscle cells, which suggests that this muscle plays a critical role in pelvic floor support.