Effects of cyclic mechanical stretch on extracellular matrix synthesis by human scleral fibroblasts.
In order to understand the effect of mechanical strain on scleral extracellular matrix remodeling, human scleral fibroblasts were subjected to equibiaxial stretch in vitro and the expression of proteoglycans, metalloproteinases (MMPs) and tissue inhibitor of metalloproteinase-2 (TIMP-2) were evaluated. Isolated human scleral fibroblasts were seeded onto flexible bottom culture plates, and subjected to a cyclic stretch regimen of 15% equibiaxial stretch for 45 s followed by 15s of rest for 6-48 h in the presence of 35SO4. Newly synthesized proteoglycans were measured in the medium by CPC precipitation of radiolabelled glycosaminoglycans. MMP-2 activity and expression levels were measured in the medium by, Western blot, gel zymography and real-time PCR. Steady state levels of TIMP-2 mRNA and membrane-type MMP, MT1-MMP (MMP-14) mRNA were measured in the cell layer using real-time PCR. The predominant gelatinolytic enzyme secreted by scleral fibroblasts was the pro-enzyme form of MMP-2 (ProMMP-2). Mechanical stretch resulted in a significant increase of ProMMP-2 after 12 and 48 h (+76.28%, p<0.05; +19.56%, p<0.01, respectively). Mechanical stretch significantly increased the production of the active form of MMP-2 (ActiveMMP-2) after 48 h (+59.72%, p<0.05) and decreased levels of TIMP-2 mRNA (-22%, p<0.05). The rate of scleral proteoglycan synthesis and the steady state levels of MMP-2 and MMP-14 mRNA were not significantly affected by mechanical stretch. These results suggest that mechanical strain stimulates the activation of MMP-2 by scleral fibroblasts, possibly through increased levels of ProMMP-2 and reduced levels of TIMP-2. Increased levels of ActiveMMP-2 in the sclera would be expected to contribute to scleral extracellular matrix degradation, scleral thinning and possible ocular ectasia.
Shelton
Lilian
L
Department of Cell Biology, University of Oklahoma Health Science Center, 940 Stanton L. Young Boulevard, BMSB, Room 553, Oklahoma City, OK 73103, USA. setareh-shelton@ouhsc.edu
Rada
Jody Summers
JS
D000328:Adult; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism / Q000502:physiology*; D005136:Eye Proteins / Q000096:biosynthesis / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D053511:Matrix Metalloproteinase 14 / Q000096:biosynthesis / Q000235:genetics; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D011509:Proteoglycans / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012590:Sclera / Q000166:cytology / Q000502:physiology*; D013314:Stress, Mechanical; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000096:biosynthesis / Q000235:genetics
D005136:Eye Proteins; D011509:Proteoglycans; D012333:RNA, Messenger; D019716:Tissue Inhibitor of Metalloproteinase-2; D020778:Matrix Metalloproteinase 2; D053511:Matrix Metalloproteinase 14