Effects of mechanical stretching on trabecular matrix metalloproteinases

J. M B Bradley, Mary Kelley, X. Zhu, A. M. Anderssohn, J. P. Alexander, Ted Acott

Research output: Contribution to journalArticle

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Abstract

Purpose. The homeostatic mechanisms responsible for intraocular pressure (IOP) regulation are not understood. Studies were conducted to evaluate the hypothesis that trabecular meshwork (TM) cells sense increases in IOP as stretching or distortion of their extracellular matrix (ECM) and respond by increasing ECM turnover enzymes. Methods. Flow rates were increased in perfused human anterior segment organ cultures and the matrix metalloproteinase (MMP) levels and IOP were evaluated. Human TMs in stationary anterior segment organ culture were mechanically stretched, and MMP levels were analyzed. TM cells were grown on membranes, which were then stretched, and MMP levels were evaluated. Western immunoblots, zymography, and confocal immunohistochemistry were used to evaluate changes in MMPs and their tissue inhibitors, the TIMPs. Results. Doubling the flow rate in perfused human organ cultures increased gelatinase A levels in the perfusate by 30% to 50% without affecting gelatinase B or stromelysin levels. Immediately after doubling the flow rate, the measured IOP doubled. However, over the next few days the IOP gradually returned to the initial level, although the flow rate was maintained at double the initial value. Stretching stationary organ cultures or stretching TM cells grown on membranes resulted in similar increases in gelatinase A without changes in gelatinase B or stromelysin levels. The gelatinase A increases occurred between 24 and 72 hours and were approximately proportional to the degree of stretching. Although coating the membranes with different ECM molecule affected the gelatinase A response, the optimum response occurred when the cells had been grown long enough to produce their own ECM. By Western immunoblot and confocal immunohistochemistry, the stretch-induced increases in gelatinase A were accompanied by strong decreases in TIMP-2 levels and moderate increases in one membrane type MMP, MT1-MMP. After mechanical stretching of the membrane, gelatinase A, MT1-MMP and TIMP-2 all exhibited a similar punctate immunostaining pattern over the TM cell surface. Conclusions. These results are compatible with the hypothesis that elevations in IOP are sensed by TM cells as ECM stretch/ distortion. TM cells respond by increasing gelatinase A and MT1-MMP, while decreasing TIMP-2 levels. This will increase ECM turnover rates, reduce the trabecular resistance to aqueous humor outflow, and restore normal IOP levels. This hypothesis provides a regulatory feedback mechanism for IOP homeostasis.

Original languageEnglish (US)
Pages (from-to)1505-1513
Number of pages9
JournalInvestigative Ophthalmology and Visual Science
Volume42
Issue number7
StatePublished - 2001

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Matrix Metalloproteinase 2
Matrix Metalloproteinases
Intraocular Pressure
Trabecular Meshwork
Extracellular Matrix
Organ Culture Techniques
Matrix Metalloproteinase 14
Tissue Inhibitor of Metalloproteinase-2
Matrix Metalloproteinase 3
Membranes
Matrix Metalloproteinase 9
Membrane-Associated Matrix Metalloproteinases
Western Blotting
Immunohistochemistry
Aqueous Humor
Homeostasis
Enzymes

ASJC Scopus subject areas

  • Ophthalmology

Cite this

Effects of mechanical stretching on trabecular matrix metalloproteinases. / Bradley, J. M B; Kelley, Mary; Zhu, X.; Anderssohn, A. M.; Alexander, J. P.; Acott, Ted.

In: Investigative Ophthalmology and Visual Science, Vol. 42, No. 7, 2001, p. 1505-1513.

Research output: Contribution to journalArticle

Bradley, JMB, Kelley, M, Zhu, X, Anderssohn, AM, Alexander, JP & Acott, T 2001, 'Effects of mechanical stretching on trabecular matrix metalloproteinases', Investigative Ophthalmology and Visual Science, vol. 42, no. 7, pp. 1505-1513.
Bradley, J. M B ; Kelley, Mary ; Zhu, X. ; Anderssohn, A. M. ; Alexander, J. P. ; Acott, Ted. / Effects of mechanical stretching on trabecular matrix metalloproteinases. In: Investigative Ophthalmology and Visual Science. 2001 ; Vol. 42, No. 7. pp. 1505-1513.
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abstract = "Purpose. The homeostatic mechanisms responsible for intraocular pressure (IOP) regulation are not understood. Studies were conducted to evaluate the hypothesis that trabecular meshwork (TM) cells sense increases in IOP as stretching or distortion of their extracellular matrix (ECM) and respond by increasing ECM turnover enzymes. Methods. Flow rates were increased in perfused human anterior segment organ cultures and the matrix metalloproteinase (MMP) levels and IOP were evaluated. Human TMs in stationary anterior segment organ culture were mechanically stretched, and MMP levels were analyzed. TM cells were grown on membranes, which were then stretched, and MMP levels were evaluated. Western immunoblots, zymography, and confocal immunohistochemistry were used to evaluate changes in MMPs and their tissue inhibitors, the TIMPs. Results. Doubling the flow rate in perfused human organ cultures increased gelatinase A levels in the perfusate by 30{\%} to 50{\%} without affecting gelatinase B or stromelysin levels. Immediately after doubling the flow rate, the measured IOP doubled. However, over the next few days the IOP gradually returned to the initial level, although the flow rate was maintained at double the initial value. Stretching stationary organ cultures or stretching TM cells grown on membranes resulted in similar increases in gelatinase A without changes in gelatinase B or stromelysin levels. The gelatinase A increases occurred between 24 and 72 hours and were approximately proportional to the degree of stretching. Although coating the membranes with different ECM molecule affected the gelatinase A response, the optimum response occurred when the cells had been grown long enough to produce their own ECM. By Western immunoblot and confocal immunohistochemistry, the stretch-induced increases in gelatinase A were accompanied by strong decreases in TIMP-2 levels and moderate increases in one membrane type MMP, MT1-MMP. After mechanical stretching of the membrane, gelatinase A, MT1-MMP and TIMP-2 all exhibited a similar punctate immunostaining pattern over the TM cell surface. Conclusions. These results are compatible with the hypothesis that elevations in IOP are sensed by TM cells as ECM stretch/ distortion. TM cells respond by increasing gelatinase A and MT1-MMP, while decreasing TIMP-2 levels. This will increase ECM turnover rates, reduce the trabecular resistance to aqueous humor outflow, and restore normal IOP levels. This hypothesis provides a regulatory feedback mechanism for IOP homeostasis.",
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T1 - Effects of mechanical stretching on trabecular matrix metalloproteinases

AU - Bradley, J. M B

AU - Kelley, Mary

AU - Zhu, X.

AU - Anderssohn, A. M.

AU - Alexander, J. P.

AU - Acott, Ted

PY - 2001

Y1 - 2001

N2 - Purpose. The homeostatic mechanisms responsible for intraocular pressure (IOP) regulation are not understood. Studies were conducted to evaluate the hypothesis that trabecular meshwork (TM) cells sense increases in IOP as stretching or distortion of their extracellular matrix (ECM) and respond by increasing ECM turnover enzymes. Methods. Flow rates were increased in perfused human anterior segment organ cultures and the matrix metalloproteinase (MMP) levels and IOP were evaluated. Human TMs in stationary anterior segment organ culture were mechanically stretched, and MMP levels were analyzed. TM cells were grown on membranes, which were then stretched, and MMP levels were evaluated. Western immunoblots, zymography, and confocal immunohistochemistry were used to evaluate changes in MMPs and their tissue inhibitors, the TIMPs. Results. Doubling the flow rate in perfused human organ cultures increased gelatinase A levels in the perfusate by 30% to 50% without affecting gelatinase B or stromelysin levels. Immediately after doubling the flow rate, the measured IOP doubled. However, over the next few days the IOP gradually returned to the initial level, although the flow rate was maintained at double the initial value. Stretching stationary organ cultures or stretching TM cells grown on membranes resulted in similar increases in gelatinase A without changes in gelatinase B or stromelysin levels. The gelatinase A increases occurred between 24 and 72 hours and were approximately proportional to the degree of stretching. Although coating the membranes with different ECM molecule affected the gelatinase A response, the optimum response occurred when the cells had been grown long enough to produce their own ECM. By Western immunoblot and confocal immunohistochemistry, the stretch-induced increases in gelatinase A were accompanied by strong decreases in TIMP-2 levels and moderate increases in one membrane type MMP, MT1-MMP. After mechanical stretching of the membrane, gelatinase A, MT1-MMP and TIMP-2 all exhibited a similar punctate immunostaining pattern over the TM cell surface. Conclusions. These results are compatible with the hypothesis that elevations in IOP are sensed by TM cells as ECM stretch/ distortion. TM cells respond by increasing gelatinase A and MT1-MMP, while decreasing TIMP-2 levels. This will increase ECM turnover rates, reduce the trabecular resistance to aqueous humor outflow, and restore normal IOP levels. This hypothesis provides a regulatory feedback mechanism for IOP homeostasis.

AB - Purpose. The homeostatic mechanisms responsible for intraocular pressure (IOP) regulation are not understood. Studies were conducted to evaluate the hypothesis that trabecular meshwork (TM) cells sense increases in IOP as stretching or distortion of their extracellular matrix (ECM) and respond by increasing ECM turnover enzymes. Methods. Flow rates were increased in perfused human anterior segment organ cultures and the matrix metalloproteinase (MMP) levels and IOP were evaluated. Human TMs in stationary anterior segment organ culture were mechanically stretched, and MMP levels were analyzed. TM cells were grown on membranes, which were then stretched, and MMP levels were evaluated. Western immunoblots, zymography, and confocal immunohistochemistry were used to evaluate changes in MMPs and their tissue inhibitors, the TIMPs. Results. Doubling the flow rate in perfused human organ cultures increased gelatinase A levels in the perfusate by 30% to 50% without affecting gelatinase B or stromelysin levels. Immediately after doubling the flow rate, the measured IOP doubled. However, over the next few days the IOP gradually returned to the initial level, although the flow rate was maintained at double the initial value. Stretching stationary organ cultures or stretching TM cells grown on membranes resulted in similar increases in gelatinase A without changes in gelatinase B or stromelysin levels. The gelatinase A increases occurred between 24 and 72 hours and were approximately proportional to the degree of stretching. Although coating the membranes with different ECM molecule affected the gelatinase A response, the optimum response occurred when the cells had been grown long enough to produce their own ECM. By Western immunoblot and confocal immunohistochemistry, the stretch-induced increases in gelatinase A were accompanied by strong decreases in TIMP-2 levels and moderate increases in one membrane type MMP, MT1-MMP. After mechanical stretching of the membrane, gelatinase A, MT1-MMP and TIMP-2 all exhibited a similar punctate immunostaining pattern over the TM cell surface. Conclusions. These results are compatible with the hypothesis that elevations in IOP are sensed by TM cells as ECM stretch/ distortion. TM cells respond by increasing gelatinase A and MT1-MMP, while decreasing TIMP-2 levels. This will increase ECM turnover rates, reduce the trabecular resistance to aqueous humor outflow, and restore normal IOP levels. This hypothesis provides a regulatory feedback mechanism for IOP homeostasis.

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