Adrenocorticotropin preferentially up-regulates angiopoietin 2 in the human fetal adrenal gland: implications for coordinated adrenal organ growth and angiogenesis.
BACKGROUND
ACTH is the key tropic hormone for the human fetal adrenal (HFA). Because vascular development must be coordinated with organ growth, ACTH may regulate local angiogenic factors, thereby influencing HFA angiogenesis. We previously demonstrated that ACTH up-regulates vascular endothelial growth factor in HFA cortical cells. A newer angiogenic factor family, the angiopoietins (Angs), also plays critical roles. Ang1 stabilizes, whereas Ang2 destabilizes vessels, increasing responsiveness to angiogenic stimuli.


OBJECTIVE
The objective of this study was to investigate expression and ACTH regulation of Angs and their receptor Tie2 in the HFA.


METHODS
Studies were conducted involving RNA, frozen sections, and primary cell cultures from HFAs (14-24 wk) and human adult adrenal RNA.


METHODS
Angs and Tie2 mRNA levels were determined by real-time quantitative RT-PCR, Ang2 and Tie2 were localized by immunostaining, and ACTH regulation of Angs was investigated by real-time quantitative RT-PCR, Western blot, and ELISA.


RESULTS
Mean HFA Ang2 to Ang1 mRNA ratio was 6.3-fold higher than adult adrenals (P < 0.001). Ang2 was localized predominantly in the HFA periphery, whereas Tie2 demonstrated endothelial localization. In isolated HFA cortical cells, ACTH up-regulated Ang mRNA levels in a time- and dose-dependent manner, with the balance favoring Ang2. Ang2 protein levels were elevated in ACTH-stimulated HFA cortical cells and conditioned medium. 8-Bromoadenosine cAMP and forskolin mimicked ACTH effects on the Angs.


CONCLUSIONS
Higher HFA Ang2 to Ang1 ratios may reflect greater vascular remodeling than in the adult. Angs, particularly Ang2, in concert with vascular endothelial growth factor, may mediate ACTH tropic action, ensuring coordination of HFA growth, steroidogenesis, and angiogenesis.
Ishimoto
Hitoshi
H
Center for Reproductive Sciences, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, California 94143-0556, USA.
Ginzinger
David G
DG
Jaffe
Robert B
RB
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000311:Adrenal Glands / Q000196:embryology* / Q000254:growth & development / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000328:Adult; D042702:Angiopoietin-2 / Q000096:biosynthesis*; D015153:Blotting, Western; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007150:Immunohistochemistry; D007202:Indicators and Reagents; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D042787:Receptor, TIE-2 / Q000096:biosynthesis; D015854:Up-Regulation / Q000187:drug effects
D042702:Angiopoietin-2; D007202:Indicators and Reagents; D012333:RNA, Messenger; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000324:Adrenocorticotropic Hormone; D042787:Receptor, TIE-2