Stem cells in the ovary

For decades, scientists have thought that female mammals are born with a lifetime supply of oocytes in the ovary, irreversibly destined to decline after birth. However, in recent years a significant controversy with regard to the potential replenishing effects of cells from the bone marrow and blood on ovarian follicular renewal has been stirred up. Although these claims have been met with harsh skepticism, if they prove to be true, the current understanding of the female reproductive system must be revisited. Although these observations and allusions have been limited to the mouse system only, they have opened new discussions about the potential consequences of bone marrow transplantation and even blood donation to the replenishment of the female genital system in general. Still, these findings have not been replicated in other research laboratories so far and the proof that oogenesis can be renewed after birth from cells originating in the bone marrow is still lacking.
In contrast to the ongoing controversy with regard to the possibility of ongoing renewal of oogenesis in the ovary and the possible existence of adult germ stem cells, the existence of somatic stem cells in the ovary has not been hypothesized for a long time.
The first part of this study has been performed to confirm the presence of pluripotent or multipotent stem cell populations among granulosa cells collected from mature human ovarian follicles. This work includes attempts to promote the growth of GCs over prolonged time periods in vitro. Previous studies have demonstrated that this is not possible with culture media which contain FSH and androgens. We identify the specific markers for mesenchymal stem cells and mature GCs and differentiate luteinizing GCs into other cell types of the mesenchymal lineage.
Graafian ovarian follicles consist of follicular fluid, one single mature oocyte and several hundred thousands of granulosa cells (GC). Until now, luteinizing GCs are considered to be terminally differentiated, destined to undergo death after ovulation. Present concepts of luteal function, endocrine regulation of early pregnancy and the recruitment of new ovarian follicles are all based on the cyclical renewal of the entire population of GC.
The first part of this study has been performed to confirm the presence of pluripotent or multipotent stem cell populations among granulosa cells collected from mature human ovarian follicles. This work includes attempts to promote the growth of GCs over prolonged time periods in vitro. Previous studies have demonstrated that this is not possible with culture media which contain FSH and androgens. We identify the specific markers for mesenchymal stem cells and mature GCs and differentiate luteinizing GCs into other cell types of the mesenchymal lineage.
In the second part we demonstrate a three-dimensional (3D) pellet culture system containing type I collagen, which together with LIF allowed not only the survival and growth of primary human GCs, but supported a significant subpopulation of GCs to maintain their phenotype and functionality for prolonged time periods.