Apart from the functioning of the ovary in the female reproductive cycle, many sex steroids are secreted that are vital in the menstrual cycle. Humans are exposed to a large variety of chemicals in their lifetime. A major health challenge today is molecules present in the environment and from natural sources that mimic or inhibit components of the endocrine system. Such endocrine disrupting compounds (EDCs) include molecules we encounter almost every day such as bisphenol A (BPA) from plastic bottles, triclosan present in household and personal care products, polycyclic aromatic hydrocarbons (PAHs) from industrial pollution, as well as, alkyl phenol from paints and cosmetics.
A 2013 published Royal College of Obstetricians and Gynaecologists (RCOG) report highlighted these molecules can target germ cells in the developing ovary in the foetus whose effects can be seen in the F2 generations! This becomes a huge issue as the effects can be seen only after years. A toxicant that targets the female reproductive system not only can affect the ovary but also cause changes at the epigenetic level.
Studies of follicle development and toxicology have been assisted by the use of in vitro cultures of ovaries or follicles. According to a 2014 published article in Reproductive Toxicology by Stefansdottir and team, the parameters of ovary culture can be controlled precisely to permit an in-detail analysis of the toxic effects of a molecule. The way a molecule targets the follicles or chromosomes or signalling can be highlighted. The approach to culture depends on the species of study and media used. The direct effects of toxins can be studied using embryonic culture or pre-meiotic germ cell culture.
Many studies have shown that the effects of compounds are highly similar for in vitro and in vivo studies though the study designs can be different.
Few examples are listed:
A 2002 published Toxicology and Applied Pharmacology article by Devine and colleagues showed that 4-vinylcyclohexene diepoxide increased apoptosis in both in vitro ovarian culture and rat models. Similarly, the plasticizer present in food wraps and children’s toys, mono-(2-ethylhexyl) phthalate (MEHP) was found to lower estradiol and ovulation in both rats and cultured rat ovarian follicles. These are from separate reports: the study in rats dates back to 1994 in Toxicology and Applied Pharmacology by Davis and team while the in vitro ovary culture study was published in 2012 by Inada and colleagues in The Journal of Toxicological Sciences.
A 2011 published article in Aging by Soleimani and colleagues reported that the commonly used chemotherapy agent called doxorubicin increased apoptosis in oocytes and caused damage to the stroma in both ovary culture and animal models.
Thus, reproductive toxicology is assisted to a great extent by in vitro ovarian culture. Culture can highlight whether a compound can directly or indirectly target the reproductive system to hence function as a screening protocol to assist in vivo studies. This becomes extremely relevant today given that most of the molecules discussed above are encountered almost daily.
Bellingham, M. and Sharpe, R. M. (2013) Chemical Exposures During Pregnancy: Dealing with Potential, but Unproven, Risks to Child Health. Other. Royal College of Obstetricians and Gynaecologists, London.
Agnes Stefansdottir, Paul A. Fowler, Nicola Powles-Glover, Richard A. Anderson, Norah Spears (2014) Use of ovary culture techniques in reproductive toxicology. Reproductive Toxicology 49: 117-135.
J.P. Devine, G. Sipes, M.K. Skinner, P.B. Hoyer (2002) Characterization of a rat in vitro ovarian culture system to study to ovarian toxicant 4-vinylcyclohexene diepoxide. Toxicology and Applied Pharmacology 184 (2): 107-115.
B.J. Davis, R.R. Maronpot, J.J. Heindel (1994) Di-(2-ethylhexyl)phthalate suppresses estradiol and ovulation in cycling rats. Toxicology and Applied Pharmacology, 128: 216-223.
H. Inada, K. Chihara, A. Yamashita, I. Miyawaki, C. Fukuda, Y. Tateishi, et al (2012) Evaluation of ovarian toxicity of mono-(2-ethylhexyl) phthalate (MEHP) using cultured rat ovarian follicles. The Journal of Toxicological Sciences 37 (3) : 483-490.
R. Soleimani, E. Heytens, Z. Darzynkiewicz, K. Oktay (2011) Mechanisms of chemotherapy-induced human ovarian aging: double-strand DNA breaks and microvascular compromise Aging, 3 (8) : 782-793