Effect of Threonine on the Proliferation and Viability of Porcine Granulosa Cells

The proliferation and viability of granulosa cells directly affects the development and function of follicles. The current study examined the effect of threonine on cell morphology and cell cycle of porcine granulosa cells. It would help to understand hormone secretion, reproductive health, and disease prevention and treatment in females. Granulosa cells were isolated from pig ovaries, and different passages of cells were stained and identified by FSHR antibody. Threonine was added to the culture medium, and cells were stained with HE to examine the changes in granulosa cell morphology. Cell viability was measured using the CCK-8 assay, and cell cycle phase was determined by flow cytometry. Immunofluorescence staining showed >98% FSHR-positive cells demonstrating that the isolated granulosa cells were >95% pure. HE-staining of different passages of granulosa cells showed that cells from the second to fourth passage have stable morphology, whereas those from the fifth and subsequent passages began to degenerate and degrade. CCK-8 results showed that =0.5 mM threonine can significantly enhance granulosa cell viability after 0.5, 1 and 2 h of treatment, and cells treated with 1 mM threonine for 4 h had the highest cell viability. In contrast, 5 and 10 mM threonine significantly reduced cell viability, indicating that only a certain amount of threonine can enhance granulosa cell viability. Flow cytometry results demonstrated that the percentage of G1 phase cells was higher in the 0.1, 0.5 and 1 mM groups than in the control group, but lower in the 10 mM group than in control group. While the 5 mM group had the highest percentage of S phase cells, the 10 mM group had no S phase cells. In contrast, the percentage of G2 phase cells was much higher in the 10 mM group than in the control group and other dose groups, indicating that an appropriate amount of threonine can promote granulosa cell proliferation, but excessive threonine can inhibit cell proliferation.