Modelling oviduct fluid formation in vitro.

Oviduct fluid is the microenvironment that supports early reproductive processes including fertilisation, embryo cleavage, and genome activation. However, the composition and regulation of this critical environment remains rather poorly defined. This study uses an in vitro preparation of the bovine oviduct epithelium, to investigate the formation and composition of in vitro derived oviduct fluid (ivDOF) within a controlled environment. We confirm the presence of oviduct specific glycoprotein 1 in ivDOF and show that the amino acid and carbohydrate content resembles that of previously reported in vivo data. In parallel, using a different culture system, a panel of oviduct epithelial solute carrier genes, and the corresponding flux of amino acids within ivDOF in response to steroid hormones were investigated. We next incorporated fibroblasts directly beneath the epithelium. This dual culture arrangement represents more faithfully the in vivo environment and impacts on ivDOF composition. Lastly, physiological and pathophysiological endocrine states were modelled and their impact on the in vitro oviduct preparation evaluated. These experiments help clarify the dynamic function of the oviduct in vitro and suggest a number of future research avenues, such as investigating epithelial-fibroblast interactions, probing the molecular aetiologies of subfertility, and optimising embryo culture media.