Establishment of Culture System for In Vitro Culture of Mouse Pre-antral Follicles: Effect on In Vitro Growth by Thecal-Stromal Cells in Culture Medium without Hormones

Lee, Ki Hwan; Kim, Ju Hwan; Seo, Young Seok; Song, Hai Bum; Kang, Kil Chun

Abstract

OBJECTIVE
This present study was conducted to examine the effects on in vitro growth of pre-antral mouse follicles by thecal-stromal cells attached to around the follicular membrane in culture medium without hormones.
METHODS
Pre-antral follicles (100-130 micro meter) used in our studies were isolated mechanically by fine 30 G needles attached to 1 ml insulin syringe from mice ovaries of 20-25 days old female ICR strain. Isolated pre-antral follicles were divided into three groups by attached status of thecal-stromal cell layers to follicular membrane. Follicular Initial diameters of group I was 112.5 (mean) +/- 6.2 (SD) micro meter (n=31), group II was 112.8 +/- 7.8 micro meter (n=23), and group III was 115.1 +/- 6.5 micro meter (n=27). Divided pre-antral follicles were washed in fresh Ham's F-10 medium and cultured in 20 micro liter droplets of DMEM with glutamine, glucose and pyruvate under mineral oil on the 60 mm culture dish. All experimental media were supplemented with 10% FBS without hormones. Media were exchanged wholly by fresh media every 2 days in culture. Diameters of intrafollicular oocytes and cultured pre-antral follicles were measured using an precalibrated cross ocular micrometer at X200 every day during 6 days in vitro culture. Results were considered statistically significant when p value was less than 0.05 using Student's t-test.
RESULTS
The mean and standard deviation (SD) of initial diameters of pre-antral follicles was 113.5 +/- 2.2 micro meter in three groups. Follicular growth rate of group III was significantly (p<0.05) higher in whole culture periods than group I and group II. Rate of follicular growth between group I and group II were not significant difference in culture for 1 to 3 days. However, group II was significantly higher than group I in culture for 4 days. Diameters of grown follicles for 6 days was 155.2 +/- 18.7 micro meter, 196.9 +/- 24.1 micro meter and 284.2 +/- 47.6 micro meter in group I, group II and group III, respectively. Growth rate of intrafollicular oocytes between three groups were not difference and revealed to continuous growth patterns in whole culture periods. Follicular diameter after culture for 7 days were not measured because of disruption of follicular structure or outgrowth of granulosa cells.
CONCLUSION
Pre-antral follicles were grown very well in DMEM medium without hormones. Thecal- stromal cells attached to the surface of follicular membrane has acted effectively in vitro growth of follicles.