CHANGES IN MORPHOLOGY AND GLYCAN EXPRESSION IN THE BABOON Papio hamadryas OVIDUCTAL EPITHELIUM DURING THE MENSTRUAL CYCLE

The mammalian oviduct is a highly specialized structure where fertilization and early embryonic development take piace. Its mucosa! epithelium is involved in maintaining and modulating a dynamic intralwuinal fluid via secretory activity. The mucosa! epithelium ofthe oviduct consists of ciliated and non-ciliated (secretory cells). The oviductal glycoproteins (OGPs) are involved in pre-and post-fertilization events [1]. As regards baboons, reports exist on the cyclic changes of the oviductal epitheliwu and the localization of OGP in Papio anubis [2], whereas studi es on the oviduct of ba bo on Papi o hamadryas are absent. In this study, we investigated for the first time the morphology and glycan composition of baboon Papio hamadryas oviductal epitheliwu during the menstmal cycle. Oviducts were laparoscopically removed from 14 healthy adult female Papio hamadryas at the Zoo Safari (Fasano, Italy). The stage of the menstrual cycle was based on the sex honuone levels and the vagina! cytology features. Histological investigations were carried out on fuubriae, infundibulum, ampulla, and isthmus separately fixed in 4% ( v /v) paraformaldehyde, embedded in paraffin wax, and stained with hematoxylin-eosin for morphological analyses and by means of a pane! of 9 fluorescent lectins for glycoconju.gate characterization. During the menstrual cycle, the morphometric analysis revealed a s ignificant change in the epitheliwu height of ali oviductal segments with an increase from the follicular phase to the preovulatory phas:e and a decrease in the lutea! phase. However, the oviducts of the lutea! and follicular phases showed similar values of the epitheliwu height in the fimbriae, whereas the isthmus epitheliwu height was significant (P<0.01) lower in the lutea! phase. The apical protn1sions were a charactetistic feature of non-ciliated cells in the preovulato1y phase oviducts. Lectin histochemistry detected the presence of OGPs mainly in the apical zone and the luminal surface ofthe epithelium with a clear presence of 1) highly ma1mose N-linked glycans (Con A) in the oviducts during the entire menstn1al cycle, 2) a2,6-linked s ialic acids (MAL II) in the preovulatory phase oviducts, 3) a2,3-linked sialic acids (SNA) in the preovulatory and lutea! phases oviducts, 4) GalNAc terminating glycans (HPA) from the infundibulum to the istluuus of preovulatory and lutea! phases, 5) GalNAc-DBA binding sites in the infundibulwu of the lutea! phase, 6) al,3-linked fucosylated glycans (LTA) in the ampulla ofpreovulatory phase, and 7) al,2-linked fucosylated glycans (UEA I) in the fimbriae of the lutea! phase. Apical protn1sions of preovulatory non-ciliated cells displayed binding sites for MAL II in the fuubtiae and infundibuhuu, and for Con A and LTA in the amptùla. Non-ciliated celi apical protrusions of lutea! oviducts showed UEA positivity in the fimbriae and HPA reactivity from the infundibulum to the isthmus. These restùts demonstrated for the first time regional morphological and chemical differences in the baboon Papio hamad1yas oviductal epithelium as well as that glycosylation pattem varies during the menstn1al cycle. The observed changes cotùd be related to the oviductal region-specific functions. These findings add new data on the baboons which due to their size and anatomica! s imilatity to humans, make an excellent model for female reproduction studies [3]. [1) Barton et al et al. Roles of steroid honnones in oviductal function. Reproduction 159:R125-R137. 2020. [2) Verhage et al. The baboon oviduct: characteristics of an oestradiol-dependent oviduct-specific glycoprotein. Hum Reprod Update 3:541-552. 1997. [3] Bauer C. The baboon (Papio sp.) as a model for female reproduction studies. Contraception 92:120-123, 2015.