Effect of growth hormone (GH) on in vitro nuclear and cytoplasmic oocyte maturation, cumulus expansion, hyaluronan synthases, and connexins 32 and 43 expression, and GH receptor messenger RNA expression in equine and porcine species.

The research study investigates how growth hormone (GH) affects the maturation and expansion of cumulus-oocyte complexes (COCs), which are crucial for reproduction, in horse and pig species. The findings suggest GH has a positive impact on nuclear maturation in both species but improves cumulus expansion only in horses.

Objective and Methodology

• The primary goal of the study was to explore the role of GH on the in vitro expansion and maturation of oocytes in equine and porcine COCs and to ascertain its mode of action.
• In an experiment, equine and porcine COCs were exposed to different concentrations of their respective species’ GH in specific culture mediums.
• Post culturing, researchers evaluated the degree of cumulus expansion and the nuclear stage.
• For porcine oocytes, they assessed their cytoplasmic maturation through in vitro fertilization and a seven-day development period.

Investigations into Protein Expression

• They also analyzed the changes in the expression of proteins implicated in cumulus expansion in equine COCs using antibodies against connexins 32 and 43 and hyaluronan synthases (Has) 1, 2, and 3.
• The presence of GH receptor mRNA in oocytes and cumulus cells of both species was investigated using reverse transcription-polymerase chain reaction with specific primers.

Findings of the Study

• The study found that the GH in maturation medium triggered cumulus expansion in equine COCs but had no effect on porcine COCs.
• However, it did enhance nuclear maturation in both equine and porcine COCs.
• No significant impact of GH was observed on porcine fertilization and embryo development post GH exposure.
• GH receptor mRNA was detected in both equine and porcine oocytes and cumulus cells, indicating a possibility of direct effect to GH.
• The research concluded that GH does not alter the expression of Has 1, Has 3, and connexin 43, proteins crucial for cumulus expansion, in equine cumulus cells.