mTOR kinase inhibition results in oocyte loss characterized by empty follicles in human ovarian cortical strips cultured in vitro.
OBJECTIVE
To determine whether oocyte loss is induced by mTOR kinase inhibition in human cortical strips as seen in model organisms in vivo and in vitro.


METHODS
Ovarian cortex was collected at two centers and cut into small strips. Strips were cultured for 6 days with or without the mTOR inhibitor rapamycin (RAP; 100 nM). Strips were then embedded in paraffin, and serial sections were prepared.


METHODS
Samples were collected in general obstetric (Edinburgh), gynecologic surgery (New Haven), and fertility preservation assisted reproductive technology (ART) (New Haven) practices.


METHODS
Ovarian cortex collected from patients (15-34 years of age) during cesarean section (donated tissue) was removed for the purposes of fertility preservation or was prepared after oophorectomy.


METHODS
Tissue was used for research purposes only, with no subsequent patient intervention.


METHODS
Follicles were counted and assessed in each serial section. Caspase activity was monitored to determine whether mTOR inhibition activated apoptosis.


RESULTS
The RAP inclusion in cultures results in significantly fewer follicles compared with ethanol vehicle-treated controls. Furthermore, RAP treatment resulted in the induction of follicles that lacked an oocyte in any serial section (30/161 follicles vs. 1/347 ethanol vehicle-treated follicles). Caspase activity was not elevated by RAP treatment.


CONCLUSIONS
mTOR inhibition results in a conserved destruction of the oocyte by adjacent granulosa cells (GC) in the absence of increased caspase activity. This model of oocyte loss is not consistent with classic apoptosis/atresia.
Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom.
Marie
M
McLaughlin
Pasquale
P
Patrizio
Umit
U
Kayisli
Janelle
J
Luk
Travis C
TC
Thomson
Richard A
RA
Anderson
Evelyn E
EE
Telfer
Joshua
J
Johnson
D000293:Adolescent; D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D009865:Oocytes / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D006080:Ovarian Follicle / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010053:Ovary / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010587:Phagocytosis / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000633:toxicity*; D020123:Sirolimus / Q000633:toxicity*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors; D046509:Tissue Culture Techniques; D055815:Young Adult
D047428:Protein Kinase Inhibitors; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020169:Caspases; D020123:Sirolimus