Influence of follicle stage on artificial ovary outcome using fibrin as a matrix

Abstract

Study question: Do primordial-primary versus secondary follicles embedded inside a fibrin matrix have different capabilities to survive and grow after isolation and transplantation?

Summary answer: Mouse primordial-primary follicles showed a lower recovery rate than secondary follicles, but both were able to grow.

What is known already: Fresh isolated mouse follicles and ovarian stromal cells embedded in a fibrin matrix are capable of surviving and developing after short-term autografting.

Study design, size, duration: In vivo experimental model using 11 donor Naval Medical Research Institute (NMRI) mice and 11 recipient severe combined immunodeficiency (SCID) mice. Both ovaries from all NMRI mice were mechanically disrupted and primordial-primary and secondary follicles were isolated with ovarian stromal cells. They were then encapsulated in a fibrin matrix composed of 12.5 mg/ml of fibrinogen (F12.5) and 1 IU/ml of thrombin (T1) (F12.5/T1), and grafted to the inner part of the peritoneum of SCID mice for 2 and 7 days.

Participants/materials, setting, methods: This study was conducted at the Gynecology Research Unit, Université Catholique de Louvain. All materials were used to conduct histological (H-E staining) and immunohistochemical (Ki67, TUNEL) analyses.

Main results and the role of chance: Although all grafted fibrin clots were recovered, the follicle recovery rate on day 2 was 16 and 40% for primordial-primary and secondary follicles respectively, while on day 7, it was 6 and 28%. The secondary group showed a significantly higher recovery rate than the primordial-primary group (23%, P-value <0.001). Follicles found in both groups were viable, as demonstrated by live/dead assays, and no difference was observed in the apoptosis rate between groups, as evidenced by TUNEL. Their growth to further stages was confirmed by Ki67 immunostaining.

Limitations, reasons for caution: As demonstrated by our results, secondary follicles appear to be more likely to survive and develop than primordial-primary follicles in a fibrin matrix after both periods of grafting. These findings may also be attributed to the specific features of the fibrin matrix, which could benefit larger follicles, but not smaller follicles.

Wider implications of the findings: This study is essential to understanding possible impairment caused by factors such as the isolation procedure or fibrin matrix composition to the survival and development of different follicle stages. It therefore provides the basis for further investigations with longer periods of grafting.

Study funding/competing interests: This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (grant Télévie No. 7.4578.14 and 7.4627.13, grant 5/4/150/5 awarded to Marie-Madeleine Dolmans), Fonds Spéciaux de Recherche, Fondation St Luc, the Foundation Against Cancer, and the Region Wallone (Convention N°6519-OVART) and donations from Mr Pietro Ferrero, Baron Frère and Viscount Philippe de Spoelberch. None of the authors have any competing interests to declare.

Keywords: allografting; artificial ovary; fibrin matrix; isolated pre-antral follicles; mouse.