Interrelationships between ovarian follicles grown in culture and possible mediators

Dominance or cooperation between ovarian follicles can determine the number of ovulations and fecundity, but interrelationships between follicles in mono-and poly-ovulatory species and their mechanisms are poorly understood. The goals of this work were to determine the existence and compare the character of mutual influence of cultured ovarian follicles from a mono-ovulatory species (cow) with established follicular dominance with those from a poly-ovulatory species (pig), in which interrelationship between follicles remain unknown, and to examine the role of ovarian cell proliferation, the insulin like growth factor I (IGF-I)-oxytocin (OT) system, and steroid hormones in mediating interrelationships among ovarian follicles. Bovine and porcine ovarian follicles were isolated and cultured alone and in pairs, and the percentage of growing follicles was calculated. Porcine follicles were cultured alone and in pairs after addition of exogenous OT and IGF-I (100 ngmL(-1)) or inactivation of endogenous OT and IGF-I by antisera against these hormones (1%). Proliferation of porcine follicular cells was assessed by SDS PAGE-Western immunoblotting, the release of IGF-I, progesterone, androstenedione and estradiol by cultured porcine ovarian follicles was analyzed by RIA/EIA. Overall, our observations suggest (1) competition/dominance (mutual suppression of growth) in bovine ovarian follicles, (2) cooperation (mutual support of growth) in porcine ovarian follicles, (3) that this mutual growth of porcine ovarian follicles was caused by the promotion of cell proliferation, (4) that this mechanism was probably not involved in bovine follicular dominance, (5) that communication between both porcine and bovine follicles affects their secretory activity, and (6) that both follicular dominance in cows and cooperation of follicles in pigs can be mediated by either down-or up-regulation of the IGF-I-OT system, which in turn affects follicular steroidogenesis and promotes follicular cell proliferation and follicular growth. (C) 2017 Society for Biology of Reproduction & the Institute of Animal Reproduction and Food Research of Polish Academy of Sciences in Olsztyn. Published by Elsevier Sp. z o.o. All rights reserved

The Influence of Interspecies Somatic Cell Nuclear Transfer on Epigenetic Enzymes Transcription in Early Embryos

One of the main reason for the incorrect development of embryos derived from somatic cell nuclear transfer is caused by insufficient demethylation of injected somatic chromatin to a state comparable with an early embryonic nucleus. It is already known that the epigenetic enzymes transcription in oocytes and early embryos of several species including bovine and porcine zygotes is species-dependent process and the incomplete DNA methylation correlates with the nuclear transfer failure rate in mammals. In this study the transcription of DNA methyltransferase 1 and 3a (DNMT1, DNMT3a) genes in early embryonic stages of interspecies (bovine, porcine) nuclear transfer embryos (iSCNT) by RT-PCR were analyzed. Coming out from the diverse timing of embryonic genome activation (EGA) in porcine and bovine preimplantation embryos, the intense effect of ooplasm on transferred somatic cell nucleus was expected. In spite of the detection of ooplasmic DNA methyltransferases, the somatic genes for DNMT1 and DNMT3a enzymes were not expressed and the development of intergeneric embryos stopped at the 4-cell stage. Our results indicate that the epigenetic reprogramming during early mammalian development is strongly infl uenced by the ooplasmic environment

Nucleologenesis and nucleolotransfer in mammalian oocytes: A review

An effort to improve development potential of early embryos is one of the main goals of biotechnology in the area of reproductive biology with application in veterinary or human medicine. Recent observations of the function of nucleolus or rather its forms before, during and after the fertilisation or parthenogenetic activation show the key role(s) of nucleolus in the processes of early genome activation. The nucleolus is a subnuclear structure (organelle) mainly involved in regulation of transcription and translation. This organelle has been characterized in detail by immunofluorescence, cell transfection and proteomics. This data was, however, mostly obtained in nucleoli of differentiated eukaryotic cells. Much less is known about the nucleolar structural changes and related functional processes in growing and fully grown mammalian oocytes, zygotes and early cleavage stage embryos, especially in the context of embryonic genome activation. It has been shown, that nucleoli in mammalian oocytes and early embryos have several forms and functions, which vary during the oocyte growth and embryonic development. Certain functions have not been fully described or explained, yet. The method of enucleolation, which allows to remove nucleoli from the oocytes or to exchange nucleoli between oocytes or zygotes, together with their proteomic and structural analyses brought new information about functions of nucleoli in oocytes and early cleavage-stage embryos and allowed to explain some new key roles of nucleoli during oocyte maturation and early embryonic development

Improving the Quality of Oocytes with the Help of Nucleolotransfer Therapy

International audienceThe nucleolus is an important nucleus sub-organelle found in almost all eukaryotic cells. On the one hand, it is known as a differentiated active site of ribosome biogenesis in somatic cells, but on the other hand, in fully grown oocytes, zygotes, and early embryos (up to the major embryonic genome activation), it is in the form of a particular homogenous and compact structure called a fibrillar sphere. Nowadays, thanks to recent studies, we know many important functions of this, no doubt, interesting membraneless nucleus sub-organelle involved in oocyte maturation, embryonic genome activation, rRNA synthesis, etc. However, many questions are still unexplained and remain a mystery. Our aim is to create a comprehensive overview of the recent knowledge on the fibrillar sphere and envision how this knowledge could be utilized in further research in the field of biotechnology and nucleolotransfer therapy