In middle-aged (MA) female rats, we have demonstrated that intrahypothalamic gene therapy for insulin-like growth factor-I (IGF-I) extends the regular cyclicity of the animals beyond 10 months (the age at which MA rats stop ovulating). Here, we implemented long-term OSKM gene therapy in the hypothalamus of young female rats. The main goal was to extend fertility in the treated animals. We constructed an adenovector that harbors the GFP gene as well as 4 Yamanaka genes. An adenovector that only carries the gene for GFP or DsRed was used as control. At 4 months of age 12 female rats received an intrahypothalamic injection of our OSKM vector (treated rats); 12 control rats a vector expressing the marker gene (control rats). At 9.3 months of age control and treated rats were mated with young males. A group of 12 young intact female rats was also mated. The rate of pregnancy recorded was 83%, 8.3 and 25% for young, MA control and MA treated animals, respectively. Pup BW at weaning was significantly higher in the MA OSKM rats than in MA controls. At the age of estropause (10 mo), OSKM treated females still showed regular estrous cycles. The particular significance of the present results is that, for the first time, it is shown that long-term OSKM gene therapy in the hypothalamus is able to extend the functionality of such a complex system as the hypothalamopituitary-ovarian axis.