Embryology III autumn 2024 Zuzana Holubcová Department of Histology and Embryology zholub@med.muni.cz Interspecies differences in reproductive biology Sperm reservoirs - sperm deposition in female tract for 3-5 days (most mammals), weeks (birds), moths (bats) , or even years (snakes) - documented in mice, rats, hamsters, pigs, sheep, cows, horses - anticipated to exist in humans, but no evidence in vivo - binding of sperm head to the cilia of Fallopian tube epithelium (isthmus and ampula) while preserving their motility and fertilizing capacity - sperm binding mediated by carbohydrate moieties on the cillia - glycoproteins and mucopolysaccharides secreted by tubal cells maintain cell motility - extracellular vesicles promote sperm survival, capacitation and hyperactivation Kölle et al 2021 Sperm reservoirs Camara Pirez et al 2020 - digital live cell imaging Sabine Kölle Major et al, 2022 Oviparous animals External fertilization Internal fertilization Viviparous animals Female reproductive tract development Reproductive tract development ❖Birds (avian species) - right ovary does not form cortex and regresses - only left oviduct developes - ismus secrete egg shell membrane - shell gland („uterus“) lays down calcificated shell Sexual differentiation - in reptile species - gonadal differentiation and sex of the embryo is not determined by heterologous chromosomes but the incubation temperature during early and middle incubatinon period - expression of sex-determining factors are subjected to temperature-dependent regulation (e.g. truncated gene products are dysfunctional) - global warming can lead to overproduction of one sex ❖Temperature-dependent sex differentiation Lockey and Eizaguirre 2021 Sexual differentiation - gonadal androgen independent female masculinization → male-like external genitalia („pseudopenis“) → aggressive behaviour - placenta converts androstendione from adrenal glands to testosterone before gonadal differentiation - shorter gonadal androgen-free window during female prenatal development - swolled phallus-like clitoris retracted during mating ❖Spotted hyena - difficult labour (60% of firstborn cubs are stillborn!) Oogenesis - eusocial colony forming animals - division to reproductive and working groups - long life span, aging- and hypoxia resistance, rare cancer - workers have the potential to become reproductively active if queen dies or new colony is formed - large ovarian reserve, switch from anovulatory to ovulatory phenotype - model of postnatal oogenesis ❖Naked mole rat - large germ cell nests in adult ovaries - detection of putative germ line stem cells Place et al 2021 Brieňo-Enríquez 2023 Oogenesis - constitutive presence of female germ cells (leptotene and diplotene) connected by intercellular bridges - model for investigating female meiosis and cyst break down process during folliculogenesis ❖Armadillo (Chetopthractus villosus) - germ cell nests (cysts) present in the adult ovary Lepto-zygotene Pachytene Reproductive cyclicity ❖Menstruating species Spiny mouse (Acomys cahirinus) the only known rodent exhibiting menstruation! Elephant shew (Rhynchocyon petersi) Insectivorous mammal Bats (Chiroptera) Humans and Old Wold Monkeys Reproductive cyclicity Menstruation cycle Oestrous (Estrous) cycle Endometrium fate in non-conception cycles shedded reabsorbed Vaginal bleeding yes no/very few Sexual receptivity uniform strong sexual urge Duration fixed (~28 days) variable (7-21 days) Follicular phase Long (50%) Short (20%) Ovulation Middle of cycle Beginning/end of cycle Luteal phase 50% 80% Luteolysis Ovarian PGF2a Uterine PGF2a Fertile period up to 6 days 24 hours P4 effect on sexual receptivity P4 → ↓GnRH inhibits sexual receptivity P4 → ↓GnRH does not inhibit sexual receptivity Menopause occurs not described Bellofiore et al 2018 Reproductive cyclicity ❖Estrous cycle ➢ Proestrus (before desire) - ↑E2 - preparation for mating ➢ Estrus (desire) - ↑↑ E2 - ovulation, sexual receptivity ➢ Metestrus (after desire) - ↓ E2, P4↑ - preparation for pregnancy ➢ Diestrus (between desire) - P4↑↑ - quiescent stage before P4 regresses and next cycle starts Follicular phase Luteal phase Reproductive cyclicity ❖Estrous cycle ANESTRUS = acyclicity - Prolonged period of sexual rest ← pregnancy ← lactation ← presence of offspring ← stress ← pathology ← season Melatonin Reproductive cyclicity ❖Induced ovulation - ovulation occurs only after stimulus (e.g. presence of male, mating behaviour, copulation) ❖Spontaneous ovulation - endogenous ovulation trigger Cat (Felis catus) Mare (Equus) Ovarian tissue organisation and embryo motility Benammar at al 2021 „inside-out“ ovaries - germinal epithelium is in the inside of the ovary - ovulated oocytes must pass through the ovulation fossa - embryo motility and delayed implantation Ginther 2021 Preimplantation conceptus elongation - occurs in post-hatching embryos in Ungulates Turenne et al 2012 - failure to elongate (~30%) contribute to high high embryonic loss 150 mm → 30 cm-100 cm - transformation form spherical to filamentous shape Davenport et al 2023 Pérez-Gómez et al. 2021 - massive proliferation of extraembryonic tissues (TE + hypoblast) - in contrast to mouse and humans, epiblast in ungulates does not cavitate but form flat embryonic disc and anterio-posterior axis in established polar TE removed and epiblast exposed prior attachment Embryonic disc Preimplantation conceptus elongation Pérez-Gómez et al. 2021 - 3 germ layers and germ line are specified before implantation - development of epiblast is more vulnarable process than development of TE and hypoblast - different expression of lineage specific markers than in mouse Jia et al. 2023 Tveden-Nyborg et al 2005 ED = embryonic disc Preimplantation conceptus elongation Embryo implantation - invaginations of endometrial luminal epithelium - enable engulfing of the embryo after apposition and facilitate proper embryo orientation - disorganisation of luminal foldings can compromise implantation efficiency ❖ Architecture of luminal epithelium = „luminal folds“„implantation chambers“, „uterine crypts“ ? Embryonic diapause - reversible pause of early embryonic development - switching to (near) dormant state - uncoupling mating and birth time - common in non-mammalian species and documented in > 130 mammalian species - can last from days to months - obligate/facultative - lactational/seasonal (photoperiod-dependent) - the delivery is timed to favourable conditions → survival advantage to the offspring and mother van der Weijden and Aydan Bulut-Karslioglu 2021 Embryonic diapause - mammalian embryo development arrests in blastocyst stage („paused pluripotency“) - prior/after hatching occasional reports of implantation delay in humans BUT embryonic diapause is not a common reproductive strategy ? Renfree et al 2017 Embryonic diapause - under maternal control (non-receptive endometrium, endometrium signalling, uterine milieu) - dormant state characterized by reduction of mitotic activity (and metabolism - quiescence (exist of cell cycle G1 → G0 in ~17% cells ) van der Weijden and Aydan Bulut-Karslioglu 2021 ↓E2, ↑P4 , AK, Glc - inducible in non-diapause species - sheep embryos can enter diapause under diapause conditions (Ptak et al 2012) (EGF, HB-EGF) Lypolysis ↓c-Myc) Embryonic diapause - endometrial tissue-derived extracellular vesicles contain microRNA let-7 that suppress mTORC1 and thus inhibit proliferation van der Weijden et al 2021 van der Weijden et al 2021 Liu et al 2020 Ye et al 2024 - aminoacid starvation leads to mTORC1 inhibition diapause - overexpression of let-7 delayed mouse embryo development and slightly prologed survival of human blastocysts in vitro Embryonic diapause mTOR inhibitor Human blastoids mTOR inhibitor Mouse embryos Can reversible arrest in development be induced in human embryos? Embryonic diapause Nicolas Rivron Embryonic diapause Improve efficiency of ES lines derivation Cancer research (dormancy/reactivation clues) Promoting survival of IVF embryos (extending time for, cell specification, DNA repair and/or autophagy) A time window for PGT ? proliferation diapause van der Weijden and Aydan Bulut-Karslioglu 2021 Embryonic diapause ❖ Superfetation - pregnancy with embryos from more than one ovulation - pregnancy with the offspring fathered by more than one male Placentation MATERNAL-FETAL INTERFACE EPITHELIOCHORIAL SYNDESMOCHORIAL ENDOTHELIOCHORIAL HEMOCHORIAL MATERNALFETAL Placentation DISTRUBUTION OF CHORIONIC VILLI Placentation Maltepe et al 2010 junctional zone Conserving endangered species https://ivfmeeting.com/products/copy-of-session-26-assisted- reproductive-technology-in-endangered-species-conservation https://safaripark.cz/en/conservation/northern-white- rhinos/colossal-biosciences-joins-biorescue-on-its-mission-to- save-the-northern-white-rhino-from-extinction