The effect of mechanical strain on matrix metalloproteinase production by bovine trabecular meshwork cells

Purpose. To evaluate the effects of mechanical stretching of trabecular meshwork cells on matrix metalloproteinase activity. Methods. Cultured bovine trabecular meshwork cells grown on collagen-coated elastomer were subjected to 10% biaxial mechanical stretching. After various time intervals, culture medium was collected from stretched and nonstretched control cells. Matrix metalloproteinase activity was studied by zymography and levels of inhibitors were determined by immunoblotting or immunoassay of the collected medium. Results. Trabecular meshwork cells subjected to mechanical strain showed increased stromelysin and gelatinase A activity at 24 to 72 hours after initial stretching compared to control cells. By 72 hours of strain, stromelysin activity increased to up to 73% (p<0.01) whereas gelatinase A activity increased by 31% (p<0.05). The increased metalloproteinase activity was reversible with relaxation of mechanical stretch. Levels of tissue inhibitor of matrix metalloproteinase-1 and -2 remained unchanged during 72 hours of stretch. Conclusions. Changes in mechanical strain on the trabecular meshwork, which may occur in vivo during changes in intraocular pressure, induce changes in matrix metalloproteinase activity. The resultant alterations in the extracellular matrix may affect outflow resistance through the trabecular meshwork in response to alterations in intraocular pressure.