Short-term hypertonic exposure enhances in vitro follicle growth and meiotic competence of enclosed oocytes while modestly affecting mRNA expression of aquaporin and steroidogenic genes in the domestic cat model

• Published in: Theriogenology 2017-03, Vol.90, p.228-236
• Main Authors: Songsasen, N., Thongkittidilok, C., Yamamizu, K., Wildt, D.E., Comizzoli, P.
• Format: Article
• Language: English
• Subjects: Animals; Aquaporins - genetics; Aquaporins - metabolism; Aromatase - genetics; Aromatase - metabolism; Cat; Cats; Cell Culture Techniques - veterinary; Cytochrome P450 Family 17 - genetics; Cytochrome P450 Family 17 - metabolism; Female; Gene Expression; Hypertonic exposure; Hypertonic Solutions - pharmacology; In vitro follicle culture; Meiotic maturation; Oocytes - drug effects; Oocytes - growth & development; Oocytes - metabolism; Ovarian Follicle - drug effects; Ovarian Follicle - growth & development; Receptors, FSH - genetics; Receptors, FSH - metabolism; RNA, Messenger - metabolism
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2016.12.006

Using the domestic cat as a non-rodent, larger animal model, the objective was to determine the impact of a brief incubation in a hypertonic microenvironment on (1) ovarian follicle and oocyte growth in vitro, (2) developmental capacity of the resident oocyte, and (3) expression of aquaporin (AQP) genes in parallel with genes involved in regulation of folliculogenesis. In Study 1: Secondary or early antral follicles encapsulated in 0.5% alginate were allocated to one of three treatment groups: 1) culture in standard medium at 290 mOsm for 15 d (Control); 2) incubation in 350 mOsm medium for 1 h followed by culture in standard medium for 15 d (Hypertonic-1h); or 3) incubation in 350 mOsm medium for 24 h followed by incubation in standard medium for additional 14 d (Hypertonic-24h). After measuring follicle and oocyte diameters on Day 15, in vitro-grown oocytes were incubated for 24 h before assessing nuclear status. In Study 2: secondary or early antral follicles were subjected to one of the three treatments: 1) culture in standard medium at 290 mOsm for 48 h; 2) incubation in 350 mOsm medium for 1 h followed by culture in standard medium for additional 47 h; or 3) incubation in 350 mOsm medium for 24 h followed by culture in standard medium for additional 24 h. At the end of the culture period, all follicles were assessed for mRNA level of Cyp17a1, Cyp19a1, Star, Aqp1, 3, 5, 7 and 8 as well as Fshr using qPCR. Freshly collected follicles also were subjected to gene expression analysis and served as the ‘Non-cultured control’. Hypertonic-24h follicles grew larger (P