Impact of human ovarian tissue manipulation on follicles: evidence of a potential first wave of follicle activation during fertility preservation procedures

Purpose The aim of this study was to investigate the impact of processing human ovarian tissue on follicle activation dynamics. Methods Fresh ovarian tissue was retrieved from 9 women undergoing laparoscopic surgery for benign conditions. Biopsies from each patient were divided into 3 fragments, the first of which was immediately fixed in the operating room (T0) and the second and third just after processing at 25 (T25) and (T90) 90 min. To evaluate follicle activation, markers of the PI3K and Hippo signaling pathways were immunolabeled at each time point, targeting phospho-Akt (p-Akt) by immunohistochemistry and yes-associated protein (YAP) cellular localization in the granulosa cell layer by immunofluorescence. Results Four hundred forty primordial follicles were evaluated for p-Akt and 420 for YAP. Significantly stronger p-Akt expression was observed at T25 (23.01 +/- 13.45%; p=0.04) and T90 (38.99 +/- 25.21%; p<0.001) than at T0 (2.72 +/- 3.35%). A significant nucleus- to-cytoplasm shift in YAP was detected at T25 (1.21 +/- 0.25; p=0.015 compared to T0 (0.95 +/- 0.09), while T90 (1.10 +/- 0.16) values were similar to T25. Conclusion Our data prove that ovarian tissue manipulation significantly impacts follicle dynamics by stimulating the PI3K and Hippo signaling pathways involved in primordial follicle activation. Further experimental evidence must nevertheless be gathered to understand and gain control of follicle activation mechanisms in non-physiological conditions (like ovarian tissue manipulation), in order to optimize fertility preservation and restoration strategies.