The presence of midkine and its possible implication in human ovarian follicles.
OBJECTIVE
Ovarian follicles undergo a dynamic change to provide a mature ovum, and the process involves angiogenesis, follicular cell proliferation and leukocyte recruitment. Midkine (MK) is a heparin-binding growth factor that has angiogenic, mitogenic, and chemotactic activities. In the present study, we investigated the presence of MK and its possible role in human ovarian follicles.


METHODS
Follicular fluid (FF) and luteinized granulosa cells (LGC) were collected from women undergoing in vitro fertilization and embryo transfer. Expression of MK protein in FF was examined by Western blotting. Concentrations of MK, estradiol and oxygen in FF were measured. 5-bromo-2'-deoxyuridine (BrdU) incorporation assay was performed in LGC. Normal ovarian tissues were obtained surgically and used in in-situ hybridization of MK mRNA.


RESULTS
The presence of MK protein was verified in FF. MK mRNA was expressed in both granulosa cells and theca cells of large follicles. There is a significant negative correlation between the concentrations of MK and oxygen in FF, and a significant positive correlation between the concentrations of MK and estradiol. MK promoted BrdU uptake in LGC.


CONCLUSIONS
The present findings imply that hypoxic condition, a characteristic of growing follicles, associates with the production of MK. Given that MK is involved in granulosa cell proliferation and estradiol production in developing follicles, MK may play a role as a local regulator in the human ovary.
Hirota
Yasushi
Y
Department of Obstetrics and Gynecology, Faculty of Medicine, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan.
Osuga
Yutaka
Y
Nose
Emi
E
Koga
Kaori
K
Yoshino
Osamu
O
Hirata
Tetsuya
T
Yano
Tetsu
T
Tsutsumi
Osamu
O
Sakuma
Sadatoshi
S
Muramatsu
Takashi
T
Taketani
Yuji
Y
D000328:Adult; D049109:Cell Proliferation; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism; D005260:Female; D005307:Fertilization in Vitro; D015571:Follicular Fluid / Q000378:metabolism; D006107:Granulosa Cells / Q000378:metabolism; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000235:genetics / Q000378:metabolism; D000078792:Midkine; D006080:Ovarian Follicle / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D013799:Theca Cells / Q000378:metabolism
D016207:Cytokines; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D012333:RNA, Messenger; D000078792:Midkine; D004958:Estradiol; D010100:Oxygen