Background: When chemically defined media are used for in vitro maturation (IVM), fetal calf serum (FCS) and bovine serum albumin (BSA) are often replaced with synthetic macromolecules such as polyvinyl alcohol (PVA). However, the developmental competence of oocytes under these conditions is typically reduced, with lower blastocyst formation rates. This study aimed to quantify the transcripts of GDF9, BMP15, and OOSP1 in oocytes, and GREM1, PTGS2, PFKP, AREG, EREG, HAS2, VCAN, PTX3, ADAM10, and ADAM17 in cumulus cells. Methods: Oocytes were divided into three groups: immature oocytes at the germinal vesicle stage (GV), in vivo matured oocytes (IVMO), and oocytes matured in vitro in IVM medium supplemented with 10% FCS, 4 mg/mL BSA, or 1 mg/mL PVA. For the IVMO group, ten donor cows were superovulated with follicle-stimulating hormone (FSH), and cumulus–oocyte complexes (COCs) were recovered by ovum pick-up (OPU) 19-20 hours after gonadorelin administration. Gene expression was evaluated in oocytes and cumulus cells using quantitative real-time PCR. Results: The relative transcript levels of GREM1, PTGS2, PFKP , and AREG were significantly higher (p < 0.05) in cumulus cells from IVMO compared with those from GV or IVM oocytes. Additionally, oocytes matured in vitro in medium supplemented with FCS showed increased (p < 0.05) expression of GREM1 and AREG compared with those cultured with BSA or PVA. Conclusions: FCS supplementation during IVM positively influenced the transcription of GREM1 and AREG. However, the superior expression profile observed in cumulus cells from in vivo matured oocytes highlights the need for improved IVM media and culture conditions to enhance oocyte competence.

ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
    Experimental groups
    IVM
    IVMO
    Gene expression analysis
    Developmental competence assessment
    Statistical analysis
RESULTS
    expression in oocytes
DISCUSSION
CONCLUSION
REFERENCES

• Diego Gouvêa de Souza(Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-681, Brazil)
• Fernanda Nunes Marqui(Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-681, Brazil)
• Ana Carolina Monteirinho Lobo(Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-681, Brazil)
• Claudio Willian de Oliveira Delfes-Camargo(Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-681, Brazil)
• Luan Sitó-Silva(Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-681, Brazil)
• Eunice Oba(Department of Veterinary Surgery and Animal Reproduction, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu 18618-681, Brazil) Corresponding author
• Sabrina Cruz Tfaile Frasnelli(Department of Diagnosis and Surgery, School of Dentistry, São Paulo State University (UNESP), Araraquara 14801-903, Brazil)
• Andressa Vilas Boas Nogueira(Department of Periodontology and Operative Dentistry, University Medical Center of the Johannes Gutenberg University, Mainz 55131, Germany)
• Alicio Martins Jr.(Department of Clinical Surgery and Animal Reproduction, School of Veterinary Medicine, São Paulo State University (UNESP), Araçatuba 16050-680, Brazil)