The purpose of this study is to determine the efficacy and molecular mechanism of intraovarian platelet-rich plasma (PRP) administration before controlled ovarian hyperstimulation protocol (COH) in the premature ovarian insufficiency(POI) in vivo rat model. In order to assess the efficacy of intraovarian PRP injection both alone and before the COH treatment in the experimental groups of the POI model, 50 female Spraque-Dawley rats were divided into ten groups (Control group, POI group, POI+Saline group, POI+PRP group, POI+Saline+COH group POI+PRP+COH group, POI+Saline+Mating group, POI+PRP+Mating group, POI+Saline+COH+Mating group, POI+PRP+COH+Mating group). The experimental model of POI was composed by 4-Vinylcyclohexene diepoxide (VCD) injections (160mg/kg/day for 15 days). Intraovarian PRP or saline injections were conducted after VCD. After approximately 30 days (follicular activation period in rats) to PRP or saline injections, the subjects underwent the COH protocol. In ovarian tissues, PTEN and pAKT concentrations were measured by ELISA and ovarian follicle count were performed by hematoxylin-eosin staining. The number of the offspring per live birth were assessed after mating protocol. It was determined that after VCD injections, there were fewer primordial and primary follicles, more atretic follicles with a decreased ovarian weight (p<0.05). Moreover, a decreased PTEN concentration, an increased pAKT concentration, and a decreased serum AMH level were observed in POI group (p<0.05). In comparison to POI group, an increase in the number of primary follicles, an increase in PTEN concentration, and a decrease in pAKT concentration were detected in POI+PRP and POI+Saline. After intraovarian injections, it was revealed that the follicle counts, PTEN and pAKT concentrations were comparable with in POI+PRP and POI+Saline groups. The similarity of PTEN and pAKT concentrations and follicle counts in the POI+PRP and POI+Saline groups support that intraovarian PRP injection does not affect the PTEN/PI3K signaling pathway but rather the injection-induced Hippo signaling pathway. Due to the small sample size of live birth, it was not possible to determine the number of offspring. injection-induced Hippo signaling pathway on follicular development should be assessed more comprehensively since the effectiveness of intraovarian saline or PRP injection in follicular development is similar to but different from POI group. [ABSTRACT FROM AUTHOR]