Pelvic Floor Biomechanics from Animal Models

Pelvic organ prolapse (POP) is characterized by the failure of vaginal wall support and protrusion of the pelvic organs through the vaginal orifice. The exact etiology of POP remains elusive to date, and one of the primary hurdles is the limited availability of animal models, which provide a means to better understand the weakening of supportive tissues in POP and the mechanisms of treatment failures. Each animal model has its own set of advantages and disadvantages. In this chapter, we review the various animal models of POP and provide an indepth analysis of sheep as a robust large animal model for urogynecological research. The ease of handling, short lifespan, and relatively low costs are major advantages of rodent models, which have been used extensively to investigate connective tissue physiology and pathophysiology as it relates to POP. However, sheep have supporting structures for pelvic organs, as well as structural and mechanical properties more similar to humans. Many of the risk factors for sheep prolapse have close analogues in humans, including high fetal weight, obesity, dystocia, parity, and family history of prolapse. In addition, large animal models, such as sheep, are likely more appropriate for evaluation of novel therapeutic strategies for treatment. Future research using sheep and other animal models will illuminate the pathophysiology of POP as well as provide essential information on pelvic floor biomechanics and treatment efficacy.