Understanding regulators of folliculogenesis remains limited in the domestic dog (Canis familiaris), which challenges our ability to develop in vitro follicle culture systems for canid genome rescue efforts. Here, we investigated the influence of activin on dog follicle development and survival, oocyte quality, and FSH receptor expression in culture. Preantral (150 - 330-550 mu m) stage follicles were encapsulated in a fibrin-alginate hydrogel with 0, 100, or 200 ng/ml rhActivin plus 0, 0.1, 1, or 10 mu g/ml FSH for 12 or 21 d of in vitro culture. All follicle groups increased in diameter (P 330-550 mu m) stage follicles were encapsulated in a fibrin-alginate hydrogel with 0, 100, or 200 ng/ml rhActivin plus 0, 0.1, 1, or 10 mu g/ml FSH for 12 or 21 d of in vitro culture. All follicle groups increased in diameter (P 630 mu m) in early antral and antral cohorts. This complementary effect was not linked to changes in FSHR mRNA expression (P> 0.05). Although not influencing (P> 0.05) follicle survival or transzonal projection (TZP) density in shorter term 12 d culture, activin in the presence of 1 ng/ml FSH maintained TZP density from the 12-21 d interval. Activin also increased oocyte diameter and improved nuclear integrity compared to un-supplemented controls. These results indicate that activin acts synergistically with FSH to promote growth and antral cavity expansion of the dog follicle in vitro, information useful to formulating an effective culture microenvironment for this species. (C) 2019 Elsevier Inc. All rights reserved.
