Expression of Smad4 during rat ovarian development.
OBJECTIVE
To clarify the signal transduction pathway of transforming growth factor-betasuperfamily (TGF-betas) in the regulation of follicle growth by investigating the expressions of Smad4 protein and mRNA in rat ovaries in different developmental stages.


METHODS
Rat ovaries of different developmental stages were obtained to determine the expression of Smad4 protein by immunohistochemistry and image analysis system, with Smad4 mRNA measured by semi-quantitative RT-PCR. Specific primers of Smad4 and GAPDH (internal control) were used for amplification by RT-PCR, and the ratios of their integrated optical densities were calculated to estimate the relative quantity of Smad4 mRNA expression.


RESULTS
Smad4 protein was widely expressed in the ovary, mainly in the follicles, and the location and intensity of Smad4 expression varied with the degree of maturation of the ovary. In the early developmental stages, Smad4 protein expressed mainly in the primordial and preantral follicles, but little in the stromal cells, and its expression intensity in the stroma increased gradually in the course of ovarian maturation. After sexual maturity, Smad4 expression intensity varied only insignificantly among the granulosa cells, theca cells and stromal cells of the antral and mature follicles (P>0.05). The staining intensity of Smad4 in the follicles also underwent changes in relation with their development, being less intense in the oocytes of the antral and matured follicles as compared to the preantral follicles (P<0.05 and P<0.01, respectively) but markedly greater in the theca cells of the antral and matured follicles than in the preantral follicles (P<0.01). No significant difference in Smad4 expression was found in the granulosa cells of different developmental stages (P>0.05). RT-PCR demonstrated that Smad4 mRNA was expressed in all the developmental stages of the rat ovary; and from the 3rd week on, the integrated optical density of Smad4 and GAPDH was significantly higher than that in 1-day-old neonatal rats.


CONCLUSIONS
The expression patterns of Smad4 protein and mRNA in rat ovary in the course of its development indicate that Smad signal transduction may play a role in the folliculogenesis.
Miao
Zhu-Lin
ZL
Department of Obstetrics and Gynecology, First Affiliated Hospital of Ji'nan University, Ji'nan University, Guangzhou 510632, China. miaozhulinchn@136.com
Wang
Zi-Neng
ZN
Cheng
Long-Qiu
LQ
Zhang
Yun
Y
D000818:Animals; D005260:Female; D006080:Ovarian Follicle / Q000254:growth & development*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051901:Smad4 Protein / Q000096:biosynthesis* / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000502:physiology*
D012333:RNA, Messenger; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta