Oocyte like cells derived from embryonic stem cells (New insight in reproduction and regenerative medicine)

Although the field of stem cell biology has grown rapidly, there exists considerable confusion and disagreement as to the nature of stem cells. As the definitions can be restrictive, they are useful when they provide a basis for understanding and experimental standardization. A multipotent stem cell can generate multiple types of differentiated cells, the latter being cells with distinct morphologies and gene expression patterns. Due to their unlimited source and high differentiation potential, stem cells are considered as potentially new therapeutic agents for the treatment of infertility. Stem cells could be stimulated in vitro to develop various numbers of specialized cells including male and female gametes suggesting their potential use in reproductive medicine. Continuation of mammalian species requires the formation and development of the sexually dimorphic germ cells. Totipotent embryonic stem (ES) cells can readily be recovered from the inner cell mass or the germinal ridge of embryos. ES cells may be ideal for creating new organs through new protocols that will circumvent the current ethical and technical minefields.Some studies show that mouse embryonic stem cells in culture can develop into oogonia that enter meiosis, recruit adjacent cells to form follicle-like structures, and later develop into blastocysts. At the egg cylinder stage of embryonic development (embryonic day (E) 6.5 in mice), a population near the epiblast can be identified as primordial germ cells (PGCs). PGCs migrate to and colonize the genital ridges, where they produce mature germ cells and generate functional adult gametes. PGCs can be isolated either prior or subsequent to their arrival in the genital ridges and, when cultured with appropriate factors in vitro, can generate embryonic germ (EG) cells. EG cells have many of the characteristics of ES cells with respect to their differentiation potential and their contribution to the germ line of chimeric mice. The most notable difference between ES and EG cells is that the latter may display onsiderable imprinting of specific genes. In addition, stem cell-based strategies for ovarian regeneration and oocyte production have been proposed as future clinical therapies for treating infertility in women. In this case, the summarized of current knowledge and future perspectives and challenges regarding the use of stem cells in reproductive medicine is needed to be discussed.