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Vaginal thread formation in the healthy offspring of untreated Long-Evans rats
Citation:
LaRue, M., D. Hill, AND N. Chernoff. Vaginal thread formation in the healthy offspring of untreated Long-Evans rats. Triangle Consortium for Reproductive Biology, Research Triangle Park, NC, March 14, 2015.
Impact/Purpose:
Will be presented at the Triangle Consortium for Reproductive Biology (TCRB) Conference, at National Institute of Environmental Health Sciences (NIEHS), 111 TW Alexander Dr., RTP, NC 27711, March 14, 2015 Paper part of program to assess effects of undernutrition on postnatal development
Description:
Vaginal threads are characterized as cords of mesenchymal tissue that cross the vaginal opening. They are sometimes apparent in rats after weaning, and typically disappear within 1-2 days as the female reaches puberty. If persistent, they can increase uncertainty in assessing reproductive system maturity and vaginal opening, and may also interfere with parturition. The occurrence of vaginal threads has been associated with prenatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but there is evidence that other pesticides such as vinclozolin, androgens such as testosterone and trenbolone, and anti-androgenic compounds including polychlorinated biphenyls (PCBs) can cause thread formation from in-utero exposures. During a multigenerational study investigating the influence of undernutrition on postnatal development, we observed vaginal threads in two generations of Long-Evans rats. The generation treatments were as follows: FO - control or restricted diet throughout pregnancy; F1 -control or restricted diet pre-weaning, control diet during pregnancy; F2- control diet. Persistent threads were observed at nearly equal frequency (=30%) in control and food restricted FO offspring (F1), and noted in 67% of control and 80% of restricted diet F1 offspring (F2). The discovery of these threads was surprising since the mothers of both affected generations were not exposed to xenobiotics, and their appearance and viability was normal. These findings highlight the uncertainty of vaginal thread determinants, and emphasize the need for further research and enhanced reporting of vaginal thread occurrence, as called for by the Environmental Protection Agency's Endocrine Disruptor Screening Program (EDSP). Due to the importance of invivo rodent assays in assessing the maturation of the reproductive system, causalfactors involved in vaginal thread formation need to be identified, and controlled if possible, to ensure proper interpretation of studies evaluating potential adverse effects of chemicals on reproductive system maturation.