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Effects of TGF-beta2, BMP-4, and gremlin in the trabecular meshwork: implications for glaucoma.
Invest Ophthalmol Vis Sci. 2007 Mar; 48(3):1191-200.IO

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)-beta2 in their AH, and TGF-beta has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-beta 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-beta2 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-beta2 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-beta2 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-beta-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-beta2 and leads to increased ECM deposition and elevated IOP.

Authors+Show Affiliations

Department of Cell Biology and Genetics, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17325163

Citation

Wordinger, Robert J., et al. "Effects of TGF-beta2, BMP-4, and Gremlin in the Trabecular Meshwork: Implications for Glaucoma." Investigative Ophthalmology & Visual Science, vol. 48, no. 3, 2007, pp. 1191-200.
Wordinger RJ, Fleenor DL, Hellberg PE, et al. Effects of TGF-beta2, BMP-4, and gremlin in the trabecular meshwork: implications for glaucoma. Invest Ophthalmol Vis Sci. 2007;48(3):1191-200.
Wordinger, R. J., Fleenor, D. L., Hellberg, P. E., Pang, I. H., Tovar, T. O., Zode, G. S., Fuller, J. A., & Clark, A. F. (2007). Effects of TGF-beta2, BMP-4, and gremlin in the trabecular meshwork: implications for glaucoma. Investigative Ophthalmology & Visual Science, 48(3), 1191-200.
Wordinger RJ, et al. Effects of TGF-beta2, BMP-4, and Gremlin in the Trabecular Meshwork: Implications for Glaucoma. Invest Ophthalmol Vis Sci. 2007;48(3):1191-200. PubMed PMID: 17325163.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of TGF-beta2, BMP-4, and gremlin in the trabecular meshwork: 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 - 2007/2/28/pubmed PY - 2007/4/10/medline PY - 2007/2/28/entrez SP - 1191 EP - 200 JF - Investigative ophthalmology & visual science JO - Invest Ophthalmol Vis Sci VL - 48 IS - 3 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)-beta2 in their AH, and TGF-beta has been shown to increase TM extracellular matrix (ECM) production. The bone morphogenetic protein (BMP) signaling pathway modifies TGF-beta 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-beta2 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-beta2 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-beta2 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-beta-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-beta2 and leads to increased ECM deposition and elevated IOP. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/17325163/Effects_of_TGF_beta2_BMP_4_and_gremlin_in_the_trabecular_meshwork:_implications_for_glaucoma_ L2 - https://iovs.arvojournals.org/article.aspx?doi=10.1167/iovs.06-0296 DB - PRIME DP - Unbound Medicine ER -