The Roles of Vitamin A for Cytoplasmic Maturation of Bovine Oocytes

Abstract

Abstract. Vitamin A is one of the micronutrients which have been implicated in cattle reproduction.In cattle, ingested vitamin A, mainly as β-carotene (BC) from forages and retinol ester from formula feed, is metabolized and transported to the oocytes and cumulus-granulosa cells in ovarian follicles through binding to various interacting molecules. The active form of vitamin A, retinoic acid (RA), functions as a regulator of gene expression in these targets. Early research showed the positive effects of vitamin A supplementation on bovine fertility in artificial insemination, and several studies on effects of vitamin A metabolites used in other artificial reproductive techniques (ART), including superovulation, ovum pick up, and in vitro maturation culture have provided evidence for the specific roles of vitamin A in oocyte cytoplasmic maturation (acquisition of developmental competence of oocytes during their meiotic maturation period for the embryonic development after fertilization). BC may enhance cytoplasmic maturation by its antioxidant properties which cannot be replaced by RA. Furthermore, RA may promote cytoplasmic maturation of bovine oocytes via its modulatory effects on the gene expression of gonadotrophin receptors, midkine, cyclooxygenase-2, and nitric oxide synthase in cumulus-granulosa cells. Key words: Vitamin A, Cattle, Oocyte, Cytoplasmic maturation (J. Reprod. Dev. 51: [23][24][25][26][27][28][29][30][31][32][33][34][35] 2005) itamin A is one of the fat-soluble vitamins and is well known to regulate development, cellular growth and differentiation, and tissue function [1,2]. Since the earliest research into vitamin A function in cattle reproduction [3,4], vitamin A and its metabolites (Fig. 1) have been tested in various artificial reproduction techniques (ART) in cattle. It has been found so far that vitamin A and its metabolites affect ovarian follicular growth [5] and steroidogenesis [6], oviductal and uterine environments [7,8], immune functions [9-11], oocyte maturation, and embryo and conceptus development [12].Oocytes are formed during fetal life and are arrested at the prophase stage of the first meiotic division. After puberty, the fully grown oocyte arrested at the first meiotic prophase, the germinal vesicle stage, in the last folliclular wave [13] within the estrous cycle resumes meiosis in response to a preovulatory luteinizing hormone (LH) surge and reaches the metaphase stage of the second meiotic division. This process is called oocyte maturation [14] and is considered to involve not only the resumption of meiosis (nuclear maturation) but also the acquisition of developmental competence ( c y t o p l a s m i c m a t u r a t i o n ) f o r e m b r y o n i c d e v e l o p m e n t a f t e r f e r t i l i z a t i o n [ 1 5 , 1 6 ] .

Effect of all-trans retinol on in vitro development of preimplantation buffalo embryos

“…Ligand-bound RARs and RXRs function as transcription factors by binding to cis-acting DNA sequences called retinoic acid response elements (RAREs), located within the transcriptional regulation of genes (Xiao et al, 1995). More over the role of retinoids in assisted reproductive technology has been demonstrated through their effect on cytoplasmic maturation and antioxidant property (Cetica et al, 2001;Ikeda et al, 2005). Hence, an attempt has been made to assess the role of all-trans retinol in in vitro production of buffalo embryos through its supplementation in maturation and embryo culture medium.…”

Effect of Ubiquinol on Serum Reproductive Hormones of Amenorrhic Patients

“…The report shows that enhancement of ability to conceive was remarkably increased with higher antioxidants in follicular fluid with successful IVF [26]. The antioxidants promote embryonic germ cell proliferation, cytoplasmic maturation of meiosis II oocytes, induces thecal interstitial cell proliferation, corpus luteal collagen formation, dominant follicle selection, and aid in meiotic spindle formation in mature meiosis II oocytes [27][28][29][30][31][32]. Antioxidant supplements vitamin C and E, improved the embryo development in aging mouse model and Nitric Oxide (NO) may aid in antiplatelet action during implantation [33,34].…”

Effects of retinoic acid on maturation of immature mouse oocytes in the presence and absence of a granulosa cell co-culture system

“…Bagavandoss and Midgeley [28] have suggested that RA may stimulate FSH for the induction of LH receptors and also encourage progesterone production and decrease cAMP levels. Cortical granule migration as a maturation clue could be affected by RA since RA improves granular migration [29,30]. Expression of several antioxidant enzymes during in vitro oocyte maturation activates several internal defense mechanisms that protect oocytes against reactive oxygen species (ROS) [25].…”