Preservation of connexin 43 and transzonal projections in isolated bovine pre-antral follicles before and following vitrification.
PURPOSE
Gap junctions and transzonal projections play a crucial role in intercellular communication between different follicular components and are necessary for follicle development. We aimed to demonstrate gap junction protein connexin 43 (Cx43) and transzonal projections (TZPs) in viable, category 1, isolated bovine pre-antral follicles (PAFs) during short-term culture and after vitrification and warming.


METHODS
This study involved four experimental groups: fresh control, 2-day culture, 4-day culture, and vitrified secondary PAFs. Isolated PAFs were vitrified using a simple and efficient cryopreservation method by means of mini cell strainers.


RESULTS
Cx43 and TZPs were detected in pre-antral follicles of all stages, as well as in every experimental group. The group fresh follicles showed a higher percentage of follicles that were positive for Cx43 (91.7%) than the follicles that were vitrified (77.4%). All follicles that were cultured for 2 days were Cx43-positive (100%). Follicles cultured for 4 days (65.8%) (P = 0.002) showed the lowest percentage of follicles that were Cx43-positive. The percentages of the presence or (partial) absence of the TZP network were shown to be very heterogeneous between follicles in different treatment groups.


CONCLUSIONS
These results suggest the maintenance of communication between the oocyte and the somatic companion cells after vitrification and warming. The varying percentages of the expression of the TZP network within groups suggests that it will be of interest to investigate whether this is truly due to variability in TZP integrity and follicle quality or due to methodological limitations.
['Bus|Anniek|A|https://orcid.org/0000-0003-4898-7249', 'Szymanska|Katarzyna|K|', 'Pintelon|Isabel|I|', 'Leroy|Jo L M R|JLMR|', 'Leybaert|Luc|L|', 'Bols|Peter E J|PEJ|']
D000818:Animals D002417:Cattle D018031:Connexin 43 D015925:Cryopreservation D005260:Female D015571:Follicular Fluid D017629:Gap Junctions D018507:Gene Expression Regulation, Developmental D009865:Oocytes D006080:Ovarian Follicle D058989:Vitrification
Connexins Transzonal projections Bovine Pre-antral follicles Vitrification Mini cell strainers