MMP inhibition prevents human lens epithelial cell migration and contraction of the lens capsule

Abstract

Purpose: The development of posterior capsule contraction following cataract surgery is caused by the activity of residual lens epithelial cells. Matrix metalloproteinases (MMPs) are a group of proteolytic enzymes, which are essential for cell migration and cell mediated contraction following wound healing. The authors investigated whether inhibiting MMP activity can reduce lens epithelial cell migration and as a result, lead to a reduction in cell mediated capsule contraction.

Methods: Human donor lens capsules were cultured and treated with a broad spectrum MMP inhibitor, Ilomastat (GM6001). MMP-2 and MMP-9 production were determined by ELISA. Cell migration onto the posterior capsule and capsule contraction were digitally measured.

Results: MMP inhibition significantly reduced lens epithelial cell migration onto the posterior capsule (p<0.05), and a reduction in capsule contraction was observed (p<0.05).

Conclusions: Ilomastat significantly reduced lens epithelial cell migration onto the posterior capsule surface and inhibited capsule contraction. MMP inhibition may have a role in the therapeutic treatment of posterior capsule opacification.

Figure 1

Total MMP-2 and MMP-9 protein production collected in the culture medium was quantified by ELISA. MMP levels were reduced by Ilomastat in a dose dependent manner compared with control (day 5, day 10, day 15; p<0.05).

Figure 2

Serial digital photographs were taken of the lens capsules. The capsule diameters between the pins were measured using UTHSCSA (University of Texas Health Science Center in San Antonio) Imagetool Software, and the average diameter for each lens capsule was calculated from six repeated measurements from vertical and horizontal axes. All images were taken at the same marked area at 10× magnification. Three capsules were measured at each treatment group. The graph illustrates the mean distance travelled by the cells and the error bars represent a 95% confidence interval.

Figure 3

(A) Negative control treated lens capsule at day 15 demonstrating typical capsule wrinkling. The anterior capsule had also adhered onto the posterior capsule, which is not visible in the photograph. (B) Lens capsule that has been treated with 100 μM Ilomastat at day 15. The capsule remains round with minimal capsule wrinkling compared with (A). At higher magnification of the boxed area of (A), the lens epithelial cells have clearly migrated over the posterior capsule to form a confluent layer (C). This contrasts with the marked area of (B), which shows virtually no lens epithelial cell migration onto the posterior capsule (D). (A and B, ×2.5 magnification; C and D, ×10 magnification.)

Figure 4

Cultured lens capsules were photographed at regular intervals and the average capsule diameters were digitally measured. The graph illustrates the effect of Ilomastat on capsule contraction. MMP inhibition resulted in a decrease in capsule contraction and therefore capsule diameter compared with control. Error bars indicating 95% confidence interval have been included but fall within the data points.

Figure 5

Viable LEC number measured with the WST assay. Cell proliferation in the presence of negative control, 1 μM, 10 μM, and 100 μM Ilomastat was quantified. No significant difference was found between proliferation rates in the different treatment groups. Error bars represent standard error of the mean.