Nuclear transfer methods to study aging

Diminished ovarian reserve causes adverse ART outcomes attributed to effects on oxygen metabolism function in cumulus cells

BACKGROUND

Declining oocyte quality in women with advanced age has been a major impediment to assisted reproductive treatments' (ART) success rate. However, aging is often accompanied by a diminished ovarian reserve (DOR). Cumulus cells (CCs) are known to play an important role in the development and maturation of oocytes, and the quality of CCs actually reflects the quality of the oocyte. In this study, CCs were used to investigate the real reasons for the decline in oocyte quality in older women.

METHODS

Ninety-nine CC samples were subdivided into 4 different groups according to the different age and ovarian reserve status. Other than clinical ART results, transcriptional expression profiles were performed in CCs to detect the differences.

RESULTS

The results were that DOR, no matter in young or advanced age group, was found to be significantly associated with adverse ART outcomes. Of note, there were no statistically significant changes in ART outcomes in the group at advanced age with normal ovarian reserve (NOR), compared to the young with NOR. DOR induced a series of transcriptional variations in CCs commonly enriched in oxygen metabolism.

CONCLUSION

Our results revealed that the ART outcomes in advanced patients were attributable to the DOR. The oxygen metabolic changes may interfere with CCs' function of supporting oocytes. This study can provide guidance for ART practice that not age but ovarian reserve status is the main predictor for ART outcomes, and ovarian reserve status should be timely assessed when the clinical manifestations are still mild in elderly women.

Maternal spindle transfer overcomes embryo developmental arrest caused by ooplasmic defects in mice

The developmental potential of early embryos is mainly dictated by the quality of the oocyte. Here, we explore the utility of the maternal spindle transfer (MST) technique as a reproductive approach to enhance oocyte developmental competence. Our proof-of-concept experiments show that replacement of the entire cytoplasm of oocytes from a sensitive mouse strain overcomes massive embryo developmental arrest characteristic of non-manipulated oocytes. Genetic analysis confirmed minimal carryover of mtDNA following MST. Resulting mice showed low heteroplasmy levels in multiple organs at adult age, normal histology and fertility. Mice were followed for five generations (F5), revealing that heteroplasmy was reduced in F2 mice and was undetectable in the subsequent generations. This pre-clinical model demonstrates the high efficiency and potential of the MST technique, not only to prevent the transmission of mtDNA mutations, but also as a new potential treatment for patients with certain forms of infertility refractory to current clinical strategies.

Isolation and culture of bovine embryonic stem cells

Isolation and culture of primary embryonic stem (ES) cell colonies are the first critical step towards establishment of stable ES cell lines. Here we introduce a novel method designated as "Separate and Seed" that contributes remarkably to efficient derivation of bovine primary ES cell colonies from blastocysts. The bovine ES cell colonies can self-renew to passage 10 with the growth factors bFGF and BIO. The bovine ES cells exhibit morphology typical of ES cells and express pluripotent molecular markers including Oct4, Nanog, SSEA1, SSEA4, and alkaline phosphatase (AP). These pluripotent markers may be used for the characterization of authentic bovine ES cell lines. Although continued efforts are required for improving long-term culture of bovine ES cells, this novel "Separate and Seed" method plus the growth factors bFGF and BIO provides an initial effective step that may eventually lead to the derivation of authentic bovine ES cells.