MMP9 Differentially Regulates Proteins Involved in Actin Polymerization and Cell Migration during TGF-β-Induced EMT in the Lens.

Zi Zhen (Ginny) Liu,Judith A West-Mays,Aftab Taiyab

doi:10.3390/ijms222111988

Zi Zhen (Ginny) Liu, Judith A West-Mays + Show 1 more

Open Access

https://doi.org/10.3390/ijms222111988

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Abstract

Fibrotic cataracts have been attributed to transforming growth factor-beta (TGF-β)-induced epithelial-to-mesenchymal transition (EMT). Using mouse knockout (KO) models, our laboratory has identified MMP9 as a crucial protein in the TGF-β-induced EMT process. In this study, we further revealed an absence of alpha-smooth muscle actin (αSMA) and filamentous-actin (F-actin) stress fibers in MMP9KO mouse lens epithelial cell explants (LECs). Expression analysis using NanoString revealed no marked differences in αSMA (ACTA2) and beta-actin (β-actin) (ACTB) mRNA between the lenses of TGF-β-overexpressing (TGF-βtg) mice and TGF-βtg mice on a MMP9KO background. We subsequently conducted a protein array that revealed differential regulation of proteins known to be involved in actin polymerization and cell migration in TGF-β-treated MMP9KO mouse LECs when compared to untreated controls. Immunofluorescence analyses using rat LECs and the novel MMP9-specific inhibitor, JNJ0966, revealed similar differential regulation of cortactin, FAK, LIMK1 and MLC2 as observed in the array. Finally, a reduction in the nuclear localization of MRTF-A, a master regulator of cytoskeletal remodeling during EMT, was observed in rat LECs co-treated with JNJ0966 and TGF-β. In conclusion, MMP9 deficiency results in differential regulation of proteins involved in actin polymerization and cell migration, and this in turn prevents TGF-β-induced EMT in the lens.

Highlights

Cataract is the leading cause of blindness, affecting 94 million people around the world [1], and the most common resolution is cataract surgery [2]
We examined whether lens epithelial cell explants (LECs) lacking MMP9 showed an inability to polymerize filamentous actin (F-actin) as well when stimulated with TGF-β
Ex vivo experiments using mouse LECs from our laboratory have shown that the absence of MMP9 can prevent TGF-β-induced epithelial-to-mesenchymal transition (EMT) [12]

Summary

Introduction

Cataract is the leading cause of blindness, affecting 94 million people around the world [1], and the most common resolution is cataract surgery [2] This procedure is generally deemed safe, posterior capsular opacification (PCO), a fibrotic cataract, can develop in up to 50% of patients post-surgery [3]. TGF-β is a group of multifunctional cytokines that play key roles in embryogenesis, cell differentiation, wound healing, cell adhesion and apoptosis [7,8] It is a potent inducer of pathological conditions including fibrosis and cancer [9,10]. As true in other systems such as the kidney and the lung, the lens shows the transdifferentiation of cuboidal epithelial cells into mesenchymal myofibroblasts during TGF-β-induced EMT [9]. This process involves the loss of epithelial characteristics such as marginalized epithelial cadherin (E-cadherin) and the gain of mesenchymal characteristics such as alpha-smooth muscle actin (αSMA) and filamentous actin (F-actin) stress fibers [9,12,13]

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