One mechanism by which water moves across cell membrane is the facilitated diffusion by water channels called aquaporins (Aqp). Such channels are expressed in different cell types [4], including embryos [20], with several isoforms allowing tissue-specific osmoregulation [16]. Some of these isoforms are also permeated by small organic http://www.selleckchem.com/products/z-vad-fmk.html compounds such as glycerol, and therefore referred as
aquaglyceroporins [16]. Aqp3 is an aquaglyceroporin which can enhance cell permeability to glycerol and other CPAs [8]. Aqp3 can also play a role on cavitation, allowing water movement across the trophectoderm [1], along with Na/K ATPase enzyme. This latter has a role on establishment and maintenance of an ionic gradient across the trophectoderm, contributing to osmotic accumulation of water and blastocyst cavity formation and expansion [39].
Previous study suggested that osmotic challenges can influence Aqp3 gene expression in mammal’s cells. Sugiyama et al. [31] found higher expression of Aqp3 gene in human keratinocytes challenged with sorbitol. Bell et al. [3] reported that exposure of mouse U0126 solubility dmso embryos to sucrose hypertonic solution for 6 and 24 h can also increase Aqp3 gene expression, but no difference was found when mouse embryos were cultured for 40 h in hypertonic medium [19]. To our knowledge, no similar data are available for bovine embryos. In vitro culture can affect the developmental capability of embryos PRKD3 [33]. Synthetic Oviduct Fluid (SOF) and Charles Rosenkrans (CR) are among the base media commonly used for culture of in vitro-fertilized bovine embryos [32], [14], [27] and [6]. Despite those media were designed for somatic cell-free embryo culture, previous studies reported that SOF medium can be used in co-culture system [37] and improve survival and hatching rates and gene
expression of fresh bovine embryos [26] and [25]. CR2aa medium can also be used in a co-culture system as an option to produce bovine embryos with satisfactory results [6]. There are few comparisons between those media [18] and none evaluating their influence on embryo permeability when in a co-culture system, despite the well-known effect of media on embryo cryotolerance [26]. Currently two methods are available for cryopreservation of bovine embryos: slow controlled freezing and vitrification [13]. Both methods can be applied with success to in vivo-produced embryos [36] whereas vitrification seems to be a better alternative for in vitro-produced bovine embryos [34]. Previous studies reported higher survival rate after vitrification for bovine embryos produced in co-culture systems than those produced in cell-free ones [26] and [28]. Vitrification uses high concentration of cryoprotectants to avoid the formation of ice-crystals, but it can also be harmful to embryonic cells [22] and [35]. The toxicity of a CPA is dependent on its permeability to cell membrane.