OR04-1 An Ex-Vivo Organ Culture Shows That BPA Directly Affects the Developing Mammary Gland

Program: Abstracts - Orals, Poster Previews, and Posters
Session: OR04-Endocrine Disrupting Chemicals
Friday, April 1, 2016: 11:45 AM-1:15 PM
Presentation Start Time: 11:45 AM
Room 258 (BCEC)
Lucia Speroni*1, Maria Voutilainen2, Marja L Mikkola2, Skylar A Klager1, Cheryl M Schaeberle1, Carlos Sonnenschein1 and Ana M Soto1
1Tufts University, Boston, MA, 2Institute of Biotechnology, University of Helsinki, Helsinki, Finland
Fetal exposure to Bisphenol-A (BPA) causes alterations in mammary gland development increasing the risk of breast cancer later in adulthood (1). At embryonic day (E) 18, the mammary stroma shows increased adipocyte differentiation, altered organization of collagen fibers, decreased deposition of tenascin-C, while the epithelial tree is enlarged and the formation of ductal lumen is delayed (2). Although estrogen receptors are present in the stroma of the fetal mammary gland, it is yet unknown whether these effects are directly mediated by BPA and/or whether BPA is acting indirectly via the hypothalamic-pituitary-ovarian axis.

To address the question of whether BPA acts directly, we utilized an ex vivo culture method of the fetal mammary gland (3). In this method, the direct action of estrogen and estrogen-mimics can be tested during E14 to 19, a critical window of exposure. This method allows for the direct observation of development as it occurs.

Mammary buds of CD1 mice were dissected at E14 and cultured for 5 days. The explants were exposed to BPA or 17β-estradiol (E2). Morphometric analysis was performed on the explant whole-mounts and markers of epithelial and mesenchymal development were detected by immunofluorescence.

We show that BPA exerts a direct effect on the fetal mammary gland. Exposure of the explants to 10-9M BPA significantly increased ductal growth (89711 ± 6836 µm2; p=0.028; n=20) while 10 -6M BPA decreased it (33518 ± 3761 µm2; p=0.006; n=9) compared to controls (67615 ± 8806 µm2; n=15). Epithelial growth was significantly diminished in mammary buds exposed to 10-9 (48337 ± 5200 µm2; p=0.005; n=16), 10-11 (49441 ± 4604 µm2; p=0.000; n=39) and 10-13M (54414 ± 6404 µm2; p=0.031; n=15) E2 compared to controls (76802 ± 6305 µm2; n=43); lower doses had no effect.

Our findings show that fetal mammary gland development is altered by direct action of estrogenic compounds. BPA shows a non-monotonic dose response curve whereby low dose increases ductal development and high doses inhibit it. Moreover, increased ductal development was observed at doses comparable to those producing similar effects in vivo (2). In contrast, estradiol resulted in a monotonic inhibition of ductal growth. Finally, in addition to its usefulness to the understanding of the hormonal regulation of mammary gland development, this ex vivo culture system could serve as a bioassay to test the numerous new chemicals that are synthesized each year and released into the environment without proper assessment of hormonal action on critical targets like the mammary gland.

(1) Paulose T et al., Reprod Toxicol. 2015 Jul; 54:58-65. (2) Vandenberg LN et al., Endocrinology 2007;148:116-27. (3) Voutilainen M et al., J Mammary Gland Biol Neoplasia 2013; 18:239-45.

Nothing to Disclose: LS, MV, MLM, SAK, CMS, CS, AMS

*Please take note of The Endocrine Society's News Embargo Policy at https://www.endocrine.org/news-room/endo-annual-meeting/pr-resources-for-endo

Sources of Research Support: This work was funded by NIH National Institute of Environmental Health Sciences award ES08314 (AMS) and the ArtBeCause Breast Cancer Foundation (LS). The content is solely the responsibility of the authors and does not necessarily represent the official position of the Centers for Disease Control and Prevention, the National Institute of Environmental Health Sciences or the National Institutes of Health.