Developmental competence of parthenogenetic mouse and human embryos after chemical or electrical activation

Abstract

Parthenogenetic reconstruction is one major strategy to create patient-specific stem cells. The aim of this study was to find the best artificial activation protocol for parthenogenetic activation of mouse and human oocytes comparing different methods. In a first set of experiments, in-vivo matured mouse oocytes and human failed-fertilized, in-vitro and in-vivo matured oocytes were artificially activated by a chemical (ionomycin) or electrical stimulus. In a second set of experiments, a combination of activating agents (electrical pulses followed by ionomycin or SrCl(2)) was applied in an aim to improve developmental competence. All embryos were evaluated daily until day 6 after activation. Mouse blastocysts were differentially stained to evaluate blastocyst quality. For mouse oocytes and human failed-fertilized oocytes, blastocyst development was significantly higher after electrical activation (P<0.05). For human in-vitro and in-vivo matured oocytes, blastocyst formation was only obtained after electrical activation of in-vitro matured oocytes. After combining activating agents, no differences in development could be observed. In conclusion, this study revealed that for both mouse and human oocytes development to the blastocyst stage was significantly better after electrical activation compared with chemical activation. Combining activating agents had no further positive effect on developmental potential.

Single Ca2+ transients vs oscillatory Ca2+ signaling for assisted oocyte activation: limitations and benefits

“…In this way, the Ca 2+ introduced from the extracellular medium is sufficient to restore the fertilization rates to normal, generally assumed as >70% oocytes showing two pronuclei (Tesarik & Sousa 1995, Tesarik et al 2002. Electrostimulation involves the application of a pulsed high-voltage electrical field, which modifies the plasma membrane lipid bilayer leading to the formation of pores, and therefore, allowing Ca 2+ entry from the extracellular medium (Versieren et al 2010 , resulting from Ca 2+ influx as well as from Ca 2+ release from the intracellular stores, particularly the ER, as described in starfish (Vasilev et al 2012); no data specific to mouse and human oocytes are currently available. …”

Early epigenetic reprogramming in fertilized, cloned, and parthenogenetic embryos

“…Parthenogenetic activation is 240 another valuable model to produce embryos in the absence of sperm fertilization through the 241 artificial activation of a metaphase II oocyte (Fig. 1) [87]. In some species (such as various 242 fishes, ants, snakes, or amphibians) parthenogenesis is a common method of asexual 243 reproduction in which an unfertilized oocyte is able to develop into a whole new individual.…”

“…Nonetheless, in mammals, parthenogenesis does not occur naturally, and if it does, it is only a 245 consequence of erroneous oocyte maturation and embryos never develop to term [87]. In conformation at very early stages, at least in mouse and rabbit embryos (Fig.…”

Assisted Reproduction

“…7 In some species, the oocyte is totipotent; once stimulated by artificial means, it can give rise to an entire adult organism. Such an artifical stimulus can occur by mechanical activation or chemical stimulation 8 and is called parthenogenesis.…”