Despite the donor's age, human adipose-derived stem cells enhance the maturation and development rates of porcine oocytes in a co-culture system

The paracrine interactions between cumulus-oocyte complexes (COCs) and follicular somatic cells during in vitro maturation (IVM) were investigated. To optimize IVM conditions, many studies have applied exogenous growth factors and cell feeding/co-culture systems using various cell types to replicate the natural follicular microenvironment during IVM. A potential candidate as cell feeders is adipose-derived stem cells (ASCs) which secrete high levels of growth factors that have roles in oocyte maturation. However, the cell donor's age should be considered because biological aging also occurs in stem cells. In the present study, the contributions of ASCs from young and old donors on an IVM co-culture system were analyzed by comparing the oocyte maturation rate, cumulus expansion index, preimplantation development after parthenogenetic activation (PA), and expression of growth factor signaling genes related to oocyte maturation in ASCs, oocytes and cumulus cells under the same culture conditions. Our study demonstrated that the confluence, viability and cell size of ASCs between young and old donors were not significantly different and only the Fibroblast Growth Factor 2 (FGF2) signaling gene showed higher expression in ASCs from young donors. The oocyte maturation rate in the young donor group (87.8 ± 1.2%) was significantly higher than in the old donor (81.1 ± 2.1%) and control (73.8 ± 2.1%) groups. After IVM, most gene expression levels in oocytes and cumulus cells in the co-culture groups were higher than in the control but the apoptotic ratios were reduced. The blastocyst development rates were not different between the young and old donor groups (23.9 ± 1.3% and 20.7 ± 0.8%, respectively) but the percentages were higher in both groups compared to the control group (16.4 ± 1.2%). A similar pattern was also found for blastocyst total cell numbers in that the young donor group (87.5 ± 5.2 cells) was not different than the old donor group (77.5 ± 3.4 cells) but both groups exhibited higher number of cells compared with the control group (57.9 ± 6.0 cells, p < .05). Our study strongly suggested that the co-culture IVM system with ASCs greatly improved the maturation and development rates of porcine oocytes. Moreover, ASCs from young donors more effectively supported porcine oocyte maturation than those from old donors although this difference did not translate into improved developmental competence.