Optimizing the efficiency of assisted reproduction procedures in the common marmoset (Callithrix jacchus) improved IVF outcomes

The marmoset has emerged as a model species for genetic studies of complex neurodevelopmental conditions because of their brain development, behavior, communication, and compact size. IVF has been used to generate wild-type and transgenic marmoset embryos, but inefficiency of IVF in the marmoset compared to other primates poses challenges for genetic manipulation. To address this limitation, we analyzed the association between variables of age, number of cycles, and progesterone levels for IVF and embryology outcomes. Longitudinal data collected over 2 years indicated that the progesterone levels 24 hours after Cloprostenol sodium (Estrumate) administration, the number of days of ovarian stimulation during an IVF cycle, and the number of oocyte retrievals that an animal had undergone all influenced IVF cycle outcomes. Higher serum progesterone levels at cycle start were negatively correlated with the likelihood of fertilized eggs progressing to the cleavage stage of embryo development. Additionally, a shorter duration of ovarian stimulation (ranging 7 to 14 days of medication) coupled with a GnRH antagonist correlated with an increased percentage of fertilized eggs. We observed a trend that a shorter hormonal stimulation cycle length was associated with a higher percentage of embryos reaching the cleavage stage. The optimization of stimulation cycle protocol and embryology has led to a high percentage of implantation after embryo transfer regardless of whether the embryo was fresh or cryopreserved. These findings suggest that shorter IVF cycles and a progesterone level <10 ng/mL at cycle start were correlated with an increased likelihood of a cleavage stage embryo development.