Abstract
Study question
Is the interaction between intrafollicular cells in PCOS, impaired by the change of vesicular fusion and/or exocytosis in granulosa cells (GCs)?
Summary answer
StxBP1 expression leves impared in GCs of PCOS.
What is known already
PCOS characterised as follicular arrest on antral follicles, cystic follicle formation, and follicular development failure. GCs secretes wide variety of factors via exocytosis, and plays critical role during folliculogenesis. Secretory vesicles are transported to cellular membrane. This process requires local concentrations of SNAREs consisting of tSNARE, vSNARE, and other vesicle fusion associated proteins. SNARE proteins are involved in vesicle fusion, exocytosis, and intracellular trafficking. GCs secretes KITL which provides follicular activation and growth. Syntaxins are one of the members of SNARE complex. StxBP1 is a protein which has a crucial role in secretory vesicle fusion that provides fusion of syntaxins.
Study design, size, duration
Granulosa cells (GCs) were collected for primary cell culture, since 2019 from both PCOS (n = 10) and healthy (male factor infertility) (n = 10) women undergoing ART. Each GCs from participant divided into two groups as in-vitro stimulated group and in-vitro nonstimulated group.
Participants/materials, setting, methods
GCs have been isolated from follicular fluid taken from patients during oocyte pick-up at Hacettepe University In-Vitro Fertilization Unit. nGCs were cultured at most secod subcultures after the isolation. The stimulated groups of both PCOS and control groups were stimulated by hCG(10IU/ml) ve FSH(0.5IU/ml) for 24 hours. Vesicle fusion proteins (Stx6, StxBP1, and SNAP25), KITL, and FSHr expressions were analyzed on granulosa cells from each group via immunofluorescent (IF) labeling and cyto-ELISA.
Main results and the role of chance
FSHr were compared in both control and PCOS before and after stimulation. There was no difference between FSHr expression levels in both groups. Indirect IF is widely considered for SNAP25, Stx6, StxBP1 proteins in all groups of GCs screening with/without stimulation. Expression of SNAP25, StxBP1 mainly scattered through all cytoplasmic area,s and membranous localization was observed. Stx6 expressions were particularly distinguished at perinuclear area of cytoplasm. However, stimulated cells of control appeared more peripherally Stx6 expression. This pattern caused by stimulation wasn’t observed in PCOS. Expressions of SNAP25, Stx6, StxBP1 were observed with less expression in PCOS. Also, the response to stimulation was lower than the control group. The differences in Stx6, SNAP25, StxBP1 and KITL levels before and after stimulation was evaluated for both control and PCOS in Cyto-ELISA. However, both SNAP25 and Stx6 expressions in GCs of both groups were similar in response to stimulation. The expression levels of StxBP1 in response to stimulation were significantly lesser than control at PCOS. KITL expressions were lower in the PCOS as expected furthermore similar to StxBP1 in response to stimulation. According to our findings, the highest response to stimulation in GCs occurred for StxBP1 and KITL in the control.
Limitations, reasons for caution
Since human cells were used in the study and the cells of each patient do not exhibit the same characteristics, the lowest number of patient samples identified in the statistical power analysis were included in the study.
Wider implications of the findings: Our view to the disruption in the secretion of signal molecules in terms of vesicle dynamics will offer a new perspective in female infertility or cross-talks in folliclar cells of the ovary.
Trial registration number
TSA–2019–18196
Inositol pyrophosphates inhibit synaptotagmin-dependent exocytosis
