Effects of TGF-β2, BMP-4, and gremlin in the trabecular meshwork: Implications for glaucoma

Robert J. Wordinger, Debra L. Fleenor, Peggy E. Hellberg, Iok Hou Pang, Tara O. Tovar, Gulab S. Zode, John A. Fuller, Abbot F. Clark

Research output: Contribution to journalArticle

140 Citations (Scopus)

Abstract

PURPOSE. The primary causative factor of primary open-angle glaucoma (POAG) is elevated intraocular pressure (IOP) due to increased aqueous humor (AH) outflow resistance, which is associated with morphologic and biochemical changes in the trabecular meshwork (TM). Patients with glaucoma have elevated levels of transforming growth factor (TGF)-β2 in their AH, and TGF-β has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-β signaling in several different tissues, and a prior study demonstrated that TM cells and tissues express members of the BMP gene family. The purpose of this study was to determine whether BMPs can alter TGF-β2 signaling in the TM and whether there are defects in BMP signaling in glaucoma. METHODS. ELISA, Western immunoblot analysis, and immunohistochemistry were used to evaluate the expression of BMP proteins in TM cells and tissues. ELISA was used to determine the effects of TGF-β2 and BMPs on TM fibronectin (FN) secretion. Gene expression was determined by gene microarrays and quantitative (q)PCR. Perfusion-cultured human anterior segments were used to study the effects of altered BMP signaling on IOP. RESULTS. The human TM synthesized and secreted BMP-4 as well as expressed BMP receptor subtypes BMPRI and BMPRII. TM cells responded to exogenous BMP-4 by phosphorylating Smad signaling proteins. Cultured human TM cells treated with TGF-β2 significantly increased FN levels, and BMP-4 blocked this FN induction. The expression of BMP family genes in normal and glaucomatous TM cells was profiled and significant elevation of mRNA and protein levels of the BMP antagonist gremlin were found in glaucomatous TM cells. In addition, Gremlin was present in human aqueous humor and in the perfusate medium of perfusion-cultured human eyes. Gremlin blocked the negative effect of BMP-4 on TGF-β-induction of FN. Recombinant Gremlin added to the medium of ex vivo perfusion-cultured human eye anterior segments caused the glaucoma phenotype of elevated IOP. CONCLUSIONS. These results are consistent with the hypothesis that, in POAG, elevated expression of Gremlin by TM cells inhibits BMP-4 antagonism of TGF-β2 and leads to increased ECM deposition and elevated IOP.

Original languageEnglish
Pages (from-to)1191-1200
Number of pages10
JournalInvestigative Ophthalmology and Visual Science
Volume48
Issue number3
DOIs
StatePublished - 1 Mar 2007

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Bone Morphogenetic Protein 4
Trabecular Meshwork
Transforming Growth Factors
Glaucoma
Bone Morphogenetic Proteins
Intraocular Pressure
Fibronectins
Aqueous Humor
Perfusion
Extracellular Matrix
Enzyme-Linked Immunosorbent Assay
Bone Morphogenetic Protein Receptors
Smad Proteins
Anterior Eye Segment
Genes

Cite this

@article{86e1360139c24c8da7d75a53c77f3fab,
title = "Effects of TGF-β2, BMP-4, and gremlin in the trabecular meshwork: Implications for glaucoma",
abstract = "PURPOSE. The primary causative factor of primary open-angle glaucoma (POAG) is elevated intraocular pressure (IOP) due to increased aqueous humor (AH) outflow resistance, which is associated with morphologic and biochemical changes in the trabecular meshwork (TM). Patients with glaucoma have elevated levels of transforming growth factor (TGF)-β2 in their AH, and TGF-β has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-β signaling in several different tissues, and a prior study demonstrated that TM cells and tissues express members of the BMP gene family. The purpose of this study was to determine whether BMPs can alter TGF-β2 signaling in the TM and whether there are defects in BMP signaling in glaucoma. METHODS. ELISA, Western immunoblot analysis, and immunohistochemistry were used to evaluate the expression of BMP proteins in TM cells and tissues. ELISA was used to determine the effects of TGF-β2 and BMPs on TM fibronectin (FN) secretion. Gene expression was determined by gene microarrays and quantitative (q)PCR. Perfusion-cultured human anterior segments were used to study the effects of altered BMP signaling on IOP. RESULTS. The human TM synthesized and secreted BMP-4 as well as expressed BMP receptor subtypes BMPRI and BMPRII. TM cells responded to exogenous BMP-4 by phosphorylating Smad signaling proteins. Cultured human TM cells treated with TGF-β2 significantly increased FN levels, and BMP-4 blocked this FN induction. The expression of BMP family genes in normal and glaucomatous TM cells was profiled and significant elevation of mRNA and protein levels of the BMP antagonist gremlin were found in glaucomatous TM cells. In addition, Gremlin was present in human aqueous humor and in the perfusate medium of perfusion-cultured human eyes. Gremlin blocked the negative effect of BMP-4 on TGF-β-induction of FN. Recombinant Gremlin added to the medium of ex vivo perfusion-cultured human eye anterior segments caused the glaucoma phenotype of elevated IOP. CONCLUSIONS. These results are consistent with the hypothesis that, in POAG, elevated expression of Gremlin by TM cells inhibits BMP-4 antagonism of TGF-β2 and leads to increased ECM deposition and elevated IOP.",
author = "Wordinger, {Robert J.} and Fleenor, {Debra L.} and Hellberg, {Peggy E.} and Pang, {Iok Hou} and Tovar, {Tara O.} and Zode, {Gulab S.} and Fuller, {John A.} and Clark, {Abbot F.}",
year = "2007",
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doi = "10.1167/iovs.06-0296",
language = "English",
volume = "48",
pages = "1191--1200",
journal = "Investigative Ophthalmology and Visual Science",
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Effects of TGF-β2, BMP-4, and gremlin in the trabecular meshwork : Implications for glaucoma. / Wordinger, Robert J.; Fleenor, Debra L.; Hellberg, Peggy E.; Pang, Iok Hou; Tovar, Tara O.; Zode, Gulab S.; Fuller, John A.; Clark, Abbot F.

In: Investigative Ophthalmology and Visual Science, Vol. 48, No. 3, 01.03.2007, p. 1191-1200.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effects of TGF-β2, BMP-4, and gremlin in the trabecular meshwork

T2 - Implications for glaucoma

AU - Wordinger, Robert J.

AU - Fleenor, Debra L.

AU - Hellberg, Peggy E.

AU - Pang, Iok Hou

AU - Tovar, Tara O.

AU - Zode, Gulab S.

AU - Fuller, John A.

AU - Clark, Abbot F.

PY - 2007/3/1

Y1 - 2007/3/1

N2 - PURPOSE. The primary causative factor of primary open-angle glaucoma (POAG) is elevated intraocular pressure (IOP) due to increased aqueous humor (AH) outflow resistance, which is associated with morphologic and biochemical changes in the trabecular meshwork (TM). Patients with glaucoma have elevated levels of transforming growth factor (TGF)-β2 in their AH, and TGF-β has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-β signaling in several different tissues, and a prior study demonstrated that TM cells and tissues express members of the BMP gene family. The purpose of this study was to determine whether BMPs can alter TGF-β2 signaling in the TM and whether there are defects in BMP signaling in glaucoma. METHODS. ELISA, Western immunoblot analysis, and immunohistochemistry were used to evaluate the expression of BMP proteins in TM cells and tissues. ELISA was used to determine the effects of TGF-β2 and BMPs on TM fibronectin (FN) secretion. Gene expression was determined by gene microarrays and quantitative (q)PCR. Perfusion-cultured human anterior segments were used to study the effects of altered BMP signaling on IOP. RESULTS. The human TM synthesized and secreted BMP-4 as well as expressed BMP receptor subtypes BMPRI and BMPRII. TM cells responded to exogenous BMP-4 by phosphorylating Smad signaling proteins. Cultured human TM cells treated with TGF-β2 significantly increased FN levels, and BMP-4 blocked this FN induction. The expression of BMP family genes in normal and glaucomatous TM cells was profiled and significant elevation of mRNA and protein levels of the BMP antagonist gremlin were found in glaucomatous TM cells. In addition, Gremlin was present in human aqueous humor and in the perfusate medium of perfusion-cultured human eyes. Gremlin blocked the negative effect of BMP-4 on TGF-β-induction of FN. Recombinant Gremlin added to the medium of ex vivo perfusion-cultured human eye anterior segments caused the glaucoma phenotype of elevated IOP. CONCLUSIONS. These results are consistent with the hypothesis that, in POAG, elevated expression of Gremlin by TM cells inhibits BMP-4 antagonism of TGF-β2 and leads to increased ECM deposition and elevated IOP.

AB - PURPOSE. The primary causative factor of primary open-angle glaucoma (POAG) is elevated intraocular pressure (IOP) due to increased aqueous humor (AH) outflow resistance, which is associated with morphologic and biochemical changes in the trabecular meshwork (TM). Patients with glaucoma have elevated levels of transforming growth factor (TGF)-β2 in their AH, and TGF-β has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-β signaling in several different tissues, and a prior study demonstrated that TM cells and tissues express members of the BMP gene family. The purpose of this study was to determine whether BMPs can alter TGF-β2 signaling in the TM and whether there are defects in BMP signaling in glaucoma. METHODS. ELISA, Western immunoblot analysis, and immunohistochemistry were used to evaluate the expression of BMP proteins in TM cells and tissues. ELISA was used to determine the effects of TGF-β2 and BMPs on TM fibronectin (FN) secretion. Gene expression was determined by gene microarrays and quantitative (q)PCR. Perfusion-cultured human anterior segments were used to study the effects of altered BMP signaling on IOP. RESULTS. The human TM synthesized and secreted BMP-4 as well as expressed BMP receptor subtypes BMPRI and BMPRII. TM cells responded to exogenous BMP-4 by phosphorylating Smad signaling proteins. Cultured human TM cells treated with TGF-β2 significantly increased FN levels, and BMP-4 blocked this FN induction. The expression of BMP family genes in normal and glaucomatous TM cells was profiled and significant elevation of mRNA and protein levels of the BMP antagonist gremlin were found in glaucomatous TM cells. In addition, Gremlin was present in human aqueous humor and in the perfusate medium of perfusion-cultured human eyes. Gremlin blocked the negative effect of BMP-4 on TGF-β-induction of FN. Recombinant Gremlin added to the medium of ex vivo perfusion-cultured human eye anterior segments caused the glaucoma phenotype of elevated IOP. CONCLUSIONS. These results are consistent with the hypothesis that, in POAG, elevated expression of Gremlin by TM cells inhibits BMP-4 antagonism of TGF-β2 and leads to increased ECM deposition and elevated IOP.

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U2 - 10.1167/iovs.06-0296

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SN - 0146-0404

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