Quantitative elemental analysis of bovine ovarian follicles using X-ray fluorescence imaging.

The X-ray Fluorescence Micro-spectroscopy (XFM) beamline at the Australian Synchrotron was used to image 97 follicle histological sections from 45 different bovine ovaries focusing on healthy antral follicles ranging from small (<4 mm) up to preovulatory sizes (>16 mm) and on antral follicles undergoing atresia. This analysis identified five elements (Cu, Fe, Zn, Se and Br) consistently present within the ovarian tissue with Fe, Zn and Se localised to specific structures. GeoPIXE v6.4g was subsequently used to extract quantitative information pertaining to the elemental concentrations surrounding each of these follicles. Statistical analysis suggested that significant elemental differences were evident between follicle groups sorted according to their health status (Fe and Br), and their size (Se). Se appeared to be the element which most greatly distinguished large antral follicles from smaller counterparts. The ability to use synchrotron radiation to measure trace element distributions in bovine follicles at such high resolutions could have a significant impact on understanding the mechanisms of follicular development. This research is intended to form a baseline study of healthy cycling ovaries which could later be extended to disease states, thereby improving our current understanding of infertility and endocrine diseases involving the ovary.

X-Ray fluorescence imaging and other analyses identify selenium and GPX1 as important in female reproductive function.

Studies of selenium (Se) status indicate that Se is necessary for fertility but how precisely is not known. We aimed to show that Se was important in bovine female reproductive function. The elemental distribution in the bovine ovary (n = 45 sections) was identified by X-ray fluorescence (XRF) imaging. Se was consistently localized to the granulosa cell layer of large (>10 mm) healthy follicles. Inductively Coupled Plasma - Mass Spectrometry revealed tenfold higher Se in the bovine follicle wall compared to corpora lutea. Gene expression analysis of selenoprotein genes GPX1, GPX3, VIMP and SELM in bovine granulosa cells revealed that only GPX1 was significantly up-regulated in large healthy follicles compared to the small healthy or atretic follicles (P < 0.05). Western immunoblotting identified GPX1 protein in bovine granulosa cells of large healthy follicles, but not of small healthy follicles. To assess if GPX1 was important in human follicles, cumulus cells from women undergoing IVF/ICSI with single embryo transfer were collected. Oocytes and embryos were cultured and transferred independently in 30 patients undergoing elective single embryo transfer. Gene expression of GPX1 was significantly higher in human cumulus cells from cumulus-oocyte complexes yielding a pregnancy (P < 0.05). We present the first XRF imaging of mammalian ovaries showing that Se is consistently localized to the granulosa cells of large healthy follicles. We conclude that Se and selenoproteins are elevated in large healthy follicles and may play a critical role as an antioxidant during late follicular development.