Ovarian Stem Cell Niche and Follicular Renewal in Mammals

Abstract

Stem cell niche consists of perivascular compartment, which connects the stem cells to the immune and vascular systems. During embryonic period, extragonadal primordial germ cells colonize coelomic epithelium of developing gonads. Subsequently, ovarian stem cells (OSC) produce secondary germ cells under the influence of OSC niche, including immune system-related cells and hormonal signaling. The OSC in fetal and adult human ovaries serve as a source of germ and granulosa cells. Lack of either granulosa or germ cell niche will result in premature ovarian failure in spite of the presence of OSC. During perinatal period, the OSC transdifferentiate into fibroblast-like cells forming the ovarian tunica albuginea resistant to environmental threats. They represent mesenchymal precursors of epithelial OSC during adulthood. The follicular renewal during the prime reproductive period (PRP) ensures that there are fresh eggs available for a healthy progeny. End of PRP is followed by exponentially growing fetal genetic abnormalities. The OSC are present in adult, aging, and postmenopausal ovaries, and differentiate in vitro into new oocytes. During in vitro development of large isolated oocytes reaching 200 lm in diameter, an ancestral mechanism of premeiotic nurse cells, which operates during oogenesis in developing ovaries from invertebrates to mammalian species, is utilized. In vitro developed eggs could be used for autologous IVF treatment of premature ovarian failure. Such eggs are also capable to produce parthenogenetic embryos like some cultured follicular oocytes. The parthenotes produce embryonic stem cells derived from inner cell mass, and these cells can serve as autologous pluripotent stem cells. Anat Rec, 294:1284Rec, 294: -1306Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.

Mechanism for the Decision of Ovarian Surface Epithelial Stem Cells to Undergo Neo-Oogenesis or Ovarian Tumorigenesis

“…The OSE cell layer is considered to be "germinal epithelium" and has characteristics of embryonic stem cells. There are still scholars skeptical of the existence of ovarian germline stem cells in mammals [42], but Bukovsky [43] and Tilly [44] assert that this does not take into account samples of ovarian function and different experimental methods. More persuasive is a finding from Wu Ji with OGCs showing that they make infertile mice produce offspring.…”

Plasticity of granulosa cells: on the crossroad of stemness and transdifferentiation potential

“…It should be highlighted that they decided not to carry out any purification step based on the presence of FSHR or some other factor, but considered the isolated GCs as a homogeneous cell population in terms of their stemness. This is an interesting approach since all ovarian somatic cells coexist in the common ovarian niche [8], which can play an important role in maintaining of their stemness.…”

Ovarian Stem Cell Nests in Reproduction and Ovarian Aging

“…2). Bukovsky [26] observed that the ovarian stem cell nest has been formed in the early embryonic development period and is composed of non-site specific ovarian Monocyte-derived cells (MDCs), T cells and vascular endothelial cells whereas the adult ovarian reproduction stem cell nest is made up of primary MDCs (CD14+ MDC), activated MDCs (HLA-DR+ MDC), T cells, etc.…”