Hormonal contraceptives, e.g., the pill, the patch, and the vaginal ring, contain synthetic hormones that prevent pregnancy by either stopping ovulation, changing the cervical mucus to stop sperm from passing through the cervix and finding an egg, or changing the womb's lining to prevent a fertilized egg from being implanted in it. The main component of hormonal contraceptives are progestins, which, mimic the female sex hormone progesterone. Progesterone is involved in a number of biological processes, including the menstrual cycle, pregnancy, and various aspects of foetal development, like brain programming.

Now, a team of scientists led by Professor Cathrin Brisken at EPFL's School of Life Sciences, have taken a thorough and close look at the different biological effects that different progestins in hormonal contraceptives have on the breast tissue—the mammary epithelium. The work is published in EMBO Molecular Medicine.

"Although we know how different contraceptive formulations affect the cardiovascular system, we know little about their effects on the breast," says Brisken. So, we developed new approaches to compare the most commonly used progestins in different hormonal contraceptives and were surprised to find that some of them stimulate cell proliferation in the breast—while others do not.

The researchers tested the effects of prolonged exposure to different progestins on human breast epithelial cells or HBECs, which line the inner layer of the breast. To do this, they developed "humanized" mouse mammary glands by grafting breast epithelial cells from donated human breast tissue from reduction mammoplasty samples into the animals' milk ducts and monitoring their growth in vivo.

We found that HBECs engraft and proliferate in mouse milk ducts, maintaining hormone receptor expression and hormone responsiveness, which are crucial factors for establishing a relevant preclinical model and thereby to foster translational research.

Regards

John
Editorial Assistant
Immunogenetics Open Access