Abstract
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.
Highlights
Glaucoma is a generic term for a heterogeneous group of ocular neuropathies generally defined as progressive degeneration of retinal ganglion cells (RGCs) and loss of optic nerve axons
In an initial experiment we screened for novel transforming growth factor (TGF)-b2 responsive factors in cultured human optic nerve head (ONH) astrocytes
Seven putative TGF-b2 responsive genes were identified in ONH astrocytes treated with 1 ng/ml TGF-b2 compared with untreated cells (Figure 1B)
Summary
Glaucoma is a generic term for a heterogeneous group of ocular neuropathies generally defined as progressive degeneration of retinal ganglion cells (RGCs) and loss of optic nerve axons. Without therapeutic intervention, this will lead to a confined visual field and to complete blindness. The molecular pathophysiology of glaucoma is poorly understood, reflecting its complex multifactorial etiology [2] In regard to their etiology, glaucomas can be sub grouped into primary and secondary glaucomas. An estimated 4.5 million people are blind due to a POAG, which represents more than twelve percent of all global causes for blindness [1]. We already demonstrated that cultured human ONH astrocytes respond with a strong increase of ECM protein secretion and produce high levels of the inhibitor of ECM degradation, PAI-1, when exposed to TGF-b2 [7,8,9,10,11], the most frequently increased aqueous humor (AH) factor in POAG patients [12,13]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
