Direct comparison of distinct naive pluripotent states in human embryonic stem cells

Stem cells & developmental biolog

Parthenogenic Blastocysts Derived from Cumulus-Free In Vitro Matured Human Oocytes

Approximately 20% of oocytes are classified as immature and discarded following intracytoplasmic sperm injection (ICSI) procedures. These oocytes are obtained from gonadotropin-stimulated patients, and are routinely removed from the cumulus cells which normally would mature the oocytes. Given the ready access to these human oocytes, they represent a potential resource for both clinical and basic science application. However culture conditions for the maturation of cumulus-free oocytes have not been optimized. We aimed to improve maturation conditions for cumulus-free oocytes via culture with ovarian paracrine/autocrine factors identified by single cell analysis..Human cumulus-free oocytes from hormone-stimulated cycles are capable of developing to blastocysts when cultured with ovarian factor supplementation. Our improved IVM culture conditions may be used for obtaining mature oocytes for clinical purposes and/or for derivation of embryonic stem cells following parthenogenesis or nuclear transfer

Oocyte activation, phospholipase C zeta and human infertility.

BACKGROUND: Mammalian oocytes are activated by intracellular calcium (Ca(2+)) oscillations following gamete fusion. Recent evidence implicates a sperm-specific phospholipase C zeta, PLCζ, which is introduced into the oocyte following membrane fusion, as the responsible factor. This review summarizes the current understanding of human oocyte activation failure and describes recent discoveries linking certain cases of male infertility with defects in PLCζ expression and activity. How these latest findings may influence future diagnosis and treatment options are also discussed. METHODS: Systematic literature searches were performed using PubMed, ISI-Web of Knowledge and The Cochrane Library. We also scrutinized material from the United Nations and World Health Organization databases (UNWHO) and the Human Fertilization and Embryology Authority (HFEA). RESULTS AND CONCLUSIONS: Although ICSI results in average fertilization rates of 70%, complete or virtually complete fertilization failure still occurs in 1-5% of ICSI cycles. While oocyte activation failure can, in some cases, be overcome by artificial oocyte activators such as calcium ionophores, a more physiological oocyte activation agent might release Ca(2+) within the oocyte in a more efficient and controlled manner. As PLCζ is now widely considered to be the physiological agent responsible for activating mammalian oocytes, it represents both a novel diagnostic biomarker of oocyte activation capability and a possible mode of treatment for certain types of male infertility