Ovarian Stem Cells and Progenitors and Their Regenerative Capabilities

The existence of ovarian germline stem cells (GSCs) has been challenged by various research groups. The hypothesis that mammalian ovaries contain germ cells with regenerative potential continues to be tested. Recent advancements in stem cell science have led to new information in the area, leaving the question open. Anatomically, cells purported to be undifferentiated ovarian GSCs are located near the surface epithelium and express the markers for undifferentiated stem cells. Various studies have proposed the presence of specific immunological markers for ovarian GSCs but this topic is highly contentious. The mainstay of the studies performed on ovarian GSCs has demonstrated that their transplantation into otherwise sterile postnatal mice facilitated the mice to produce embryos and offspring. In another study, ovarian GCSs were identified in reproductive-age women, which put to test the established dogma of a fixed reserve pool of oocytes before birth in humans as well. If proliferative ovarian GSCs are indeed present, their impact upon the timing of menopause needs to be better understood. Last, ovarian GSCs have also been implicated in ovarian cancers. Several studies have explored a relationship between cancer stem cells (CSCs) and putative ovarian GSCs. All of these intriguing accomplishments and open questions about the prospects of using ovarian GSCs in this field are discussed in detail in this chapter.