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Effects of midkine during in vitro maturation of bovine oocytes on subsequent developmental competence
S Ikeda1, K Ichihara-Tanaka, T Azuma
1Laboratory of Reproductive Physiology, Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Abstract:
Midkine (MK) is known to be a member of a new family of heparin-binding growth/differentiation factors, together with pleiotrophin, and to be quite rich in bovine follicular fluid. To examine whether treatment with MK during in vitro maturation (IVM) of bovine granulosa-enclosed oocytes affects their nuclear maturation and postfertilization development to the blastocyst stage, bovine granulosa-enclosed oocytes obtained from slaughterhouse-derived ovaries were cultured for 24 h in IVM medium without (control) or with various concentrations (1-500 ng/ml) of MK, followed by in vitro fertilization (IVF) and culturing. Although the MK treatment during IVM did not affect the rate of nuclear maturation or the postfertilization cleavage of oocytes, MK at > or = 10 ng/ml significantly (P: < 0.05) increased the blastocyst yields per tested and per cleaved oocyte compared with the case of the control. Next, the effects of various glycosaminoglycans (heparin, heparan sulfate, chondroitin sulfate A and C, and hyaluronic acid) preincubated with MK at 50 ng/ml were examined. The enhancing activity of MK was completely suppressed by heparin at 600 ng/ml but not by the other compounds. The effects of MK during IVM were also tested on oocytes freed from granulosa cells (GCs). When the denuded oocytes were cultured in IVM medium, no blastocyst formation after IVF was observed, regardless of MK supplementation. However, coculture of the denuded oocytes with isolated GC pellets enhanced the cleavage rates and the blastocyst yield, and these effects were more pronounced with MK supplementation. These results indicate that the presence of MK during IVM of bovine granulosa-enclosed oocytes can enhance their developmental competence to the blastocyst stage after IVF and suggest that the enhancing effects might be mainly mediated by GCs.
Insights
Midkine (MK) enhances bovine oocyte developmental competence to the blastocyst stage during in vitro maturation (IVM). This effect is mediated by granulosa cells and suppressed by heparin, suggesting MK
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cell Biology
Background:
- Midkine (MK) is a heparin-binding growth factor found in bovine follicular fluid.
- Understanding factors influencing oocyte developmental competence is crucial for assisted reproductive technologies.
Purpose of the Study:
- To investigate the effect of Midkine (MK) on the in vitro maturation (IVM) of bovine oocytes.
- To determine if MK influences nuclear maturation, postfertilization development, and blastocyst formation.
- To elucidate the role of granulosa cells and glycosaminoglycans in MK's effects.
Main Methods:
- Bovine oocytes were cultured in IVM medium with varying concentrations of MK.
- Oocytes underwent in vitro fertilization (IVF) and subsequent culture.
- The impact of heparin and other glycosaminoglycans on MK activity was assessed.
- Experiments involved both granulosa-enclosed and denuded oocytes, with and without granulosa cell co-culture.
Main Results:
- MK treatment (≥10 ng/ml) significantly increased blastocyst yields without affecting nuclear maturation or cleavage rates.
- Heparin (600 ng/ml) completely suppressed MK's enhancing activity, while other glycosaminoglycans did not.
- Granulosa cells were essential for MK's positive effects; co-culture enhanced development, especially with MK supplementation.
Conclusions:
- Midkine (MK) enhances the developmental competence of bovine oocytes to the blastocyst stage during IVM.
- Granulosa cells play a key role in mediating MK's beneficial effects.
- MK's action may involve interactions with heparin or heparin-like molecules within the follicular environment.