O-310 PARP inhibitors have no toxic effect on follicle reserve, mitotic and steroidogenic function of granulosa cells in human ovary
Authors: Iltumur E , Esmaeilian Y , Oktem O 
Published: July 2024

Abstract

Study question
Do the PARP inhibitors have gonadotoxic effects on human ovary?

Summary answer
No. The PARP inhibitor drugs Olaparib and Niraparib do not appear to have any toxic effects on the human ovary.

What is known already
The Poly (ADP-ribose) polymerase (PARP) family has many essential functions in cellular processes, including the regulation of transcription, apoptosis, and the DNA damage response. PARP has Poly (ADP-ribose) activity, which facilitates the recruitment of other repair proteins to promote the repair of DNA single-strand breaks when DNA damage occurs. PARP inhibitors are approved for the treatment of BRCA1/2 mutated breast and ovarian cancers. No data is available regarding the gonadotoxic potentials, if any, of these drugs on the human ovary. We aimed to address this issue in the current study.

Study design, size, duration
A clinical translational research study that utilizes ex-vivo and in-vitro experimental models on human ovarian cortical samples, primary luteinized non-mitotic granulosa cells, and immortalized human granulosa cells.

Participants/materials, setting, methods
Ovarian cortical samples were obtained from young women undergoing laparoscopic surgery for benign ovarian cysts (n = 5). Human non-mitotic luteinized granulosa cells (HLGCs) obtained from 10 IVF patients during the oocyte retrieval procedure and immortalized mitotic non-luteinized granulosa cell line (HGrC1), and immortalized granulosa cell tumor cell line (COV434) were used for the experiments. Cell/tissue culture, confocal imaging, flow cytometry, immunoblotting, cell viability/proliferation and hormone assays were applied.

Main results and the role of chance
Treatment of ovarian tissue samples and granulosa cells with PARP inhibitors at five different therapeutic concentrations (1, 5, 10, 20, and 40 µM/mL) up to 96 hours in culture resulted in resulted in the cleavage of PARP, validating in vitro activity of the drugs. The primordial follicle reserve and steroidogenic activity of the tissue samples remained stable at the end of culture period. Similar results were obtained in the granulosa cells, which retained their viability and steroidogenic functions after exposure to the PARP inhibitors. Real-time impedance-based cell proliferation assay with xCelligence system revealed that granulosa cells continued to proliferate normally and reached log phase in the presence of PARP inhibitors without any discernible cytotoxic effect. In immunoblot analysis, the expression of steroidogenic enzymes (StAR, aromatase, 3B-HSD and 17B-HSD) was comparable to control cells and cleaved caspase-3 expression was absent in the granulosa cells exposed to PARP inhibitors.

Limitations, reasons for caution
Caution should be exercised before extrapolating our data because these findings were obtained in ex-vivo and in-vitro models. They need to be confirmed using in-vivo experimental models such as human ovarian tissue xenografting in nude mice.

Wider implications of the findings
This study provides the first reassuring molecular evidence that PARP inhibitor drugs do not appear to have a significant gonadotoxic effect on human ovary.

Trial registration number
not applicable