Our aim was to identify ovarian mesenchymal stem cells (MSCs) associated with primordial follicle activation in the ovine model as a first step in determining their role in the catastrophic loss of follicles before birth and in girls. The second aim was to determine the role of MSCs in the activation and growth of follicles to aid our development of a tissue engineering application to preserve the fertility of girls prior to cancer therapy.
CD271+cells (MSC marker) in ovarian tissue from 11 ewes, three new-born and four premature lambs was measured by flow cytometry FACS sorted CD271+cells were cultured for 10 days. Localization of CD271+cells used confocal microscopy. Clonogenicity was assayed on CD271+ cells.
In premature lambs, 84+/-3% of viable ovarian cells were CD271+, 60+/-6% in lambs and 36+/-4% in ewes; and were much higher than premature lamb bone marrow (7%), endometrium (30%), and ewe adipose tissue (1%).
In premature lambs, the majority of primordial follicles had CD271+cells adjacent to pre-granulosa cells, and absent in dormant primordial follicles in ewes. In ewes, CD271+cells were associated with the cumulus granulosa cells of large antral follicles, and not the granulosa cells.
In the thecal region and surrounding capillaries CD271+ cells colocalised with smooth-muscle-actin (αSMA) and von Willebrand Factor (vWF) indicating pericytes and perivascular cells, typical of MSCs in other tissues.
Our pilot data indicate that cumulus cells of the adult ovine ovary express CD271, but the significance of this finding is unknown. It also suggests that ovarian CD271+ MSCs influence activation of primordial follicles by their close association and the known ability of MSC to secrete growth factors. A concentrated source of CD271+ MSCs could be incorporated into a tissue engineered scaffold to activate dormant primordial follicle in cryopreserved ovarian tissue.