More than 80,000 chemicals are registered for commercial use in the U.S. Many of them are endocrine disruptors and pose major risks to human health, hence the need for efficient evaluation of their developmental toxicity. Fetal organogenesis is a period of increased vulnerability to toxicants, in particular to those that interfere with hormone action. The fetal mammary gland is considered particularly vulnerable to hormonal disruption; exposure to xenoestrogens like diethylstilbestrol (DES) increased breast cancer incidence in women. Despite this finding, there is no data reporting the effects of DES during fetal MG development (to be examined in S.
Aim 1). Likewise, fetal exposure to bisphenol A (BPA) and its replacements led to the development of pre- neoplastic and neoplastic lesions that manifested postnatally, long after the end of exposure (effect on fetal MG development will be examined in S.
Aim 2). There is currently no reproducible system that allows for the observation of the direct effects of hormones and endocrine disruptors on the developing mammary gland while bypassing the effect of endogenous hormones and the estrogen-trapping effect of alphafetoprotein (AFP). Using an ex-vivo culture assay in which the mammary bud completes fetal morphogenesis in-vitro, allowed us to observe this process in real time. Validation of the ex-vivo method requires comparing the effects of selected chemicals that do not bind to AFP in the ex-vivo and in-vivo assays. In this regard, we observed that ethinyl estradiol, a steroidal estrogen that does not bind to AFP inhibited ductal growth both ex-vivo and in-vivo. In contrast, low BPA concentrations increased ductal development both in-vivo and in this ex-vivo explant method.
Aim 1 : To examine the ex-vivo and in-vivo effects of DES on fetal mammary gland development.
Aim 2 : To compare the ex-vivo and in-vivo fetal MG phenotype caused by exposure to endocrine disruptors known to induce proliferative lesions and/or cancer in rodents. We will use the BPA replacements BPS and BPAF. A validated ex-vivo culture assay of the developing MG will greatly facilitate mechanistic and morphometric studies of mammary gland development and provide toxicologists with a reliable, faster method to test chemicals for potential developmental toxicity.
Fetal exposure to endocrine disruptors induce deleterious effects in rodents including pathologies that have increased in human populations such as obesity, metabolic disease, infertility and mammary neoplasms suggesting a link between endocrine disruptors and these outcomes. We have developed an ex-vivo culture assay of mammary gland organogenesis that reproduces the effects of bisphenol-A observed in animals exposed in utero, and that makes it possible to observe development in real time. The proposed studies aim to validate this assay so that it can be used for mechanistic studies and for the screening of developmental toxicants which are suspected to induce breast cancer and thus would provide guidance for preventive regulations.
