Characteristics of Female Germline Stem Cells from Porcine Ovaries at Sexual Maturity

Abstract

Pigs share many anatomical and physiological features with humans, offering a unique and viable model for biomedical research. Although porcine female germline stem cells (FGSCs) were identified in the juvenile ovary, no reports described the isolation and purification of FGSCs from the pig at sexual maturity. Here, we isolated, purified, and cultured FGSCs from porcine ovaries at sexual maturity. Furthermore, we established and characterized the porcine FGSC (pFGSC) lines. In addition, we found that pFGSC lines could differentiate into oocytes when injection into tissue grafts, including human ovarian tissues. The results show that FGSCs exist in ovaries of Banna mini-pigs at juvenile and sexually maturity. These findings have implications in animal biotechnology applications and regeneration medicine.

Implications and Current Limitations of Oogenesis from Female Germline or Oogonial Stem Cells in Adult Mammalian Ovaries

“…Nonetheless, against a backdrop of continued debate and scattered reports claiming from negative data to refute the existence of OSCs and the ability of adult mouse ovaries to generate new oocytes ([61,62,63,64,65]; see also [66,67,68,69]), studies of OSCs in rodent models continued to populate the scientific literature, with nearly 30 published primary studies now available reporting on the characteristic features and functional properties of these cells in the context of postnatal oogenesis in mice and rats [37,41,49,53,66,67,68,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92]. These efforts have recently been paralleled by similar studies of OSCs in adult ovaries of cows [93,94], non-human primates [64,69] and pigs [95,96], underscoring the evolutionary conservation of the findings across diverse mammalian species. Importantly, the use of intragonadal transplantation-based approaches to establish the functional capacity of rodent OSCs to generate eggs that fertilize to produce embryos and offspring [53,67,72,73,78,80,84,85] was recently extended by inducible suicide gene-based targeted ablation and inducible genetic fate-mapping studies in mice [81,84].…”

Female Fertility Preservation through Stem Cell-based Ovarian Tissue Reconstitution In Vitro and Ovarian Regeneration In Vivo

“…Amid debate, continued studies on this topic from multiple laboratories around the world eventually produced a now large body of evidence substantiating the occurrence of postnatal oogenesis in mammals, 69–76 as well as the characteristic features and functional properties of the germ cells responsible for continued oocyte formation. 77 These cells, termed female germline or oogonial stem cells (OSCs), have been identified in, and isolated for study from, adult ovarian tissue of mice, 75,76,78–102 rats, 103 cows, 104 pigs, 105,106 nonhuman primates, 107 and women. 82,85,102,108–111 In evaluating OSCs from a functional perspective, the identity of these cells as bona-fide oocyte-producing germ cells has been independently verified by several groups using intragonadal transplantation-based approaches in rodent models, 76,78,80,82,90,94,103 which are universally considered the litmus test for functional identity testing of the male-equivalent spermatogonial stem cells (SSCs) in the tes...…”

<p>Role of stem cells in fertility preservation: current insights</p>

“…21 Indeed, it was demonstrated that FGSCs isolated from mice ovaries maintained proliferative activity in vitro and led to offspring after transplantation to sterile mice. 21,[141][142][143][144][145] Their presence was also demonstrated in prepubertal rat 146 and pig 147 and adult pig 148 and human 149 ovaries. Indeed, when FGSCs isolated from adult minipig ovaries were infected by an EGFP lentivirus and injected into human ovarian cortex pieces, EGFP + oocytes were observed after 3 weeks in ovarian cortical xenografts.…”

“…Indeed, when FGSCs isolated from adult minipig ovaries were infected by an EGFP lentivirus and injected into human ovarian cortex pieces, EGFP + oocytes were observed after 3 weeks in ovarian cortical xenografts. 148 In addition, FGSCs isolated from human cortical tissue (based on DDX4 expression) and transduced with a GFP-expression vector were shown to reform structures resembling follicles in culture with dispersed adult ovarian cells and to differentiate into oocytes when injected into human cortical tissue before xenotransplantation to nude mice. 149 In that study, the authors attributed FGSCs not being detected earlier by other teams to their smallness size (5-8 μm) and proportion (0.014±0.002%) of total ovarian cells.…”