Effects of Midkine on Adrenocortical Cells: Differential Responses in Primary Cells And a Cell Line

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 72-87-HPA Axis
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-73
Hitoshi Ishimoto*1, Kazuhiro Minegishi2, Osamu Nishimura1, Shigeru Sato1, Kanako Mitsuzuka1, Atsuko Togo1 and Robert B Jaffe3
1Tokai Univ School of Medicine, Isehara, Kanagawa, Japan, 2Keio Univ. School of Medicine, Tokyo, Japan, 3Univ CA - San Francisco, San Francisco, CA
Rapid growth of the human fetal adrenal gland (HFA) at midgestation is supported by an active proliferative drive observed in the outer, definitive zone (DZ). The HFA produces large amounts of dehydroepiandrosterone sulfate but does not synthesize significant amounts of cortisol until late in gestation (1). Midkine (MK) is a multifunctional heparin-binding growth factor and its expression is strictly regulated in temporal sequence; it is highly expressed during midgestation. We previously showed that MK expression is the highest in the HFA among human fetal tissues examined, and identified MK as a novel mitogen for DZ cells, but not for cells isolated from the inner fetal zone (FZ) (2). Additionally, MK has been shown to down-regulate expression of 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2), a key enzyme for cortisol synthesis. However, the mechanisms whereby MK exerts its effects on fetal adrenocortical cells remain elusive. To address this issue, we used the human adrenocortical cell line NCI-H295A that shares several phenotypical characteristics with HFA cortical cells, and compared its response to MK and expression of putative MK receptors with those of primary culture cells from midgestation HFAs (14-23 wks). In MTS/PMS assay, recombinant human MK (rhMK) exerted significant proliferative effects in a dose-dependent manner on NCI-H295A cells, as well as on isolated DZ cells. In contrast, rhMK treatment for 24h decreased HSD3B2 mRNA in a dose-dependent manner in isolated DZ and FZ cells, but not in NCI-H295A cells. RT-PCR demonstrated that, among putative receptors for MK, anaplastic lymphoma kinase was not expressed in both NCI-295A cells and isolated HFA cells. Low-density lipoprotein receptor-related protein-1 was expressed in both cell types. Versican and α4-integrin were expressed in isolated HFA cells but not in NCI-H295A cells, which was further confirmed by Taqman realtime RT-PCR. Collectively, results indicate that NCI-H295A cells can be a useful model for studying the proliferative effects of MK. Further, the differential responses to MK in isolated HFA cells and the cell line likely reflect different cellular MK signaling pathways that include MK receptors, providing a clue to understanding the underlying signaling mechanism for each MK function.

(1) Ishimoto H and Jaffe RB. Endocrine Reviews 2011; 32: 317-355. (2) Ishimoto H et al. J Clin Endocrinol Metab 2006; 91: 4050-4056.

Nothing to Disclose: HI, KM, ON, SS, KM, AT, RBJ

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science #21591423 awarded to HI.