The Controversy Around Callous JNK inhibitor-Methods

However they have not fared better, due in part to the need for a co-culture system that mimics the microenvironment of testicular niche. Perhaps for this reason neither fertilization nor healthy offspring have been reported to date with gametes generated by this mechanism (Table 1) [13,14,15,45,46,47,48,49,50,51,52,53,54,55,56,57,58]. Table 1 Human germ cell-like cells in vitro derivation In the female counterpart, it is generally accepted that human ovaries contain a fixed number of non-growing follicles established before birth that decreases with female age and is depleted in menopause [59,60,61,62,63,64,65,66,67,68]. Some researchers very early on struggled against the growing dogma about the finite number of follicles and oocytes at birth [69]. In the mouse model, the existence of ovarian stem cells leading to viable offspring was first reported by Zou et al. [70] in 2009. In spite of the fact that there is no evidence of persistence of oogonia in adult human ovaries, a new idea about germinal (oogonial) stem cells in adult ovaries has been developed [71,72,73,74]. The existence of stem cells in the human ovary has been surrounded by controversy. Some works in mouse and human have described a population of rare ovarian stem cells able to generate oocytes in vitro [55,75], representing an invaluable promise in regenerative medicine to treat infertile women. However, these works have been widely refuted, and some other authors consider that the presence of ovarian stem cells has been overestimated [76,77,78,79]. The ovarian stem cells are the most interesting population of cells for potential autologous de novo oogenesis and regeneration of non-functional ovaries in infertile women. In the human adult ovaries, putative ovarian stem cells (OSC) can be isolated by Fluorescence-activated cell sorting (FACS) as small rounded VASA positive-cells from the ovarian check details surface epithelium. These cells can grow and develop into oocyte-like cells in vivo and in vitro [55,80,81,82]. Interestingly there appears to be more positive results for the in vitro generation of female gametes rather to sperm (Table 1). This may be due to the greater ease to perform co-culture of OSC with the surrounding somatic cells; because follicle-like structure is easier to reproduce in vitro [55]. However, this starting material is limited or even absent in infertile patients so they do not seem to be the best option for regenerative medicine purposes on female infertile patients. For this reason pluripotent stem cells (PSCs) seem to be a better option, according to its greater availability in those kind of patients. 2.