Theophylline derivatives promote the activation of primordial follicles and ameliorate fertility deficits in naturally aged mice

The residual dormant primordial follicles in aged women and patients with premature ovarian insufficiency (POI) are difficult to activate in vivo. In this study, we found that PDE1A, PDE2A and PDE6D were expressed mainly in mouse primordial follicle oocytes and that PDE1A and PDE2A levels were significantly decreased during the activation of primordial follicles. The specific inhibitors of PDE1 (nimodipine), PDE2 (EHNA) and PDE5/6 (zaprinast) and the nonspecific PDE inhibitors theophylline derivatives (including aminophylline, dyphylline, enprofylline, choline theophyllinate, doxofylline, arofylline and lisofylline) activated mouse primordial follicles. These inhibitors also increased the levels of cyclic adenosine monophosphate (cAMP) and phosphorylated protein kinase B (p-Akt) in cultured mouse ovaries. Moreover, the administration of aminophylline, dyphylline and enprofylline to neonatal mice by intraperitoneal injection and to adolescent mice by oral treatment increased the number of growing follicle and the levels of p-Akt in the ovaries. Importantly, the oral administration of aminophylline increased the quantity and quality of ovulated oocytes and the number of offspring in naturally aged mice. In addition, aminophylline, dyphylline and enprofylline activated human primordial follicles and increased p-Akt levels. Thus, theophylline derivatives activate primordial follicles by increasing cAMP levels and activating the PI3K/Akt pathway, and the oral administration of aminophylline increases fertility in naturally aged female mice. As oral medications, theophylline derivatives may be used to increase fertility in aged women and patients with POI.