Osteopontin is induced by TGF-β2 and regulates metabolic cell activity in cultured human optic nerve head astrocytes.
The aqueous humor (AH) component transforming growth factor (TGF)-β2 is strongly correlated to primary open-angle glaucoma (POAG), and was shown to up-regulate glaucoma-associated extracellular matrix (ECM) components, members of the ECM degradation system and heat shock proteins (HSP) in primary ocular cells. Here we present osteopontin (OPN) as a new TGF-β2 responsive factor in cultured human optic nerve head (ONH) astrocytes. Activation was initially demonstrated by Oligo GEArray microarray and confirmed by semiquantitative (sq) RT-PCR, realtime RT-PCR and western blot. Expressions of most prevalent OPN receptors CD44 and integrin receptor subunits αV, α4, α 5, α6, α9, β1, β3 and β5 by ONH astrocytes were shown by sqRT-PCR and immunofluorescence labeling. TGF-β2 treatment did not affect their expression levels. OPN did not regulate gene expression of described TGF-β2 targets shown by sqRT-PCR. In MTS-assays, OPN had a time- and dose-dependent stimulating effect on the metabolic activity of ONH astrocytes, whereas TGF-β2 significantly reduced metabolism. OPN signaling via CD44 mediated a repressive outcome on metabolic activity, whereas signaling via integrin receptors resulted in a pro-metabolic effect. In summary, our findings characterize OPN as a TGF-β2 responsive factor that is not involved in TGF-β2 mediated ECM and HSP modulation, but affects the metabolic activity of astrocytes. A potential involvement in a protective response to TGF-β2 triggered damage is indicated, but requires further investigation.
Department of Anatomy II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Carolin
C
Neumann
Department of Anatomy II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Fabian
F
Garreis
Department of Anatomy II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Friedrich
F
Paulsen
Department of Anatomy II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Christian M
CM
Hammer
Department of Ophthalmology, Tufts University, Boston, Massachusetts, United States of America.
Marco T
MT
Birke
Department of Anatomy II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
Michael
M
Scholz
D000293:Adolescent; D000328:Adult; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D005901:Glaucoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D009898:Optic Disk / Q000166:cytology*; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D053781:Transforming Growth Factor beta2 / Q000494:pharmacology*; D055815:Young Adult
D053781:Transforming Growth Factor beta2; D053495:Osteopontin