Abstract
Purpose: :
Matrix modifications contribute to Posterior Capsular Opacification (PCO) leading to secondary visual loss. This develops in a significant number of patients who have undergone cataract extraction surgery. Transforming Growth Factor Beta (TGFβ) is a key regulator of PCO progression and can modulate Matrix metalloproteinase (MMPs) expression. The current study therefore aimed to elucidate the role of specific MMP family members in TGFβ mediated events.
Methods: :
Cells from the human lens line FHL-124 were employed. Gene expression of all MMP family members was determined using Real-time PCR. MMP2 protein was determined by gelatin zymography. MT1-MMP was determined using western blot methods. These methods were also used to validate SiRNA efficiency. A patch assay was used to assess contraction. Following fixation and cell staining with Coomassie Blue, imaging techniques were employed to measure all areas covered by cells. Subsequent to serum starvation for 24hrs, cells were maintained in the following conditions for 1-3 days. Control medium ± GM6001 (25µM); 10ng/ml TGFβ2 ± GM6001; Control medium ± SiRNA MMP2; 10ng/ml TGFβ2 ± SiRNA MMP2; Control medium ± SiRNA-MT1-MMP; 10ng/ml TGFβ2 ± SiRNA-MT1-MMP.
Results: :
FHL-124 cells exposed to 10ng/ml TGFβ2 demonstrated increased MMP2 and MT1-MMP gene expression. MMP2 protein expression was significantly elevated in response to TGFβ2; MT1-MMP level was also increased, but not significantly. MMP2 and MT1-MMP were significantly inhibited by specific SiRNA leading to significant reduction of both message and protein levels, in the presence and absence of TGFβ2. A significant degree of matrix contraction was observed in patch assays cultured for 3 days in the presence of TGFβ. Using the non-selective MMP inhibitor GM6001 (25µM) TGFβ-induced matrix contraction was prevented. Specific inhibition of MMP2 using SiRNA methods also prevented TGFβ-induced matrix contraction. However, specific inhibition of MT1-MMP did not suppress the observed TGFβ-induced matrix contraction.
Conclusions: :
MMP2 plays a critical role in TGFβ mediated matrix contraction, which appears to be independent of MT1-MMP. MMP2, therefore, provides a specific target for the treatment of PCO and other fibrotic disorders.
Keywords: posterior capsular opacification (PCO) • growth factors/growth factor receptors • wound healing