Effect of delivery of MMP inhibitors from PDMS as a model IOL material on PCO markers

Abstract

Posterior capsule opacification (PCO) or secondary cataract formation, following intraocular lens implantation, is a significant complication affecting an estimated 28% of cataract patients. Matrix metalloproteinases (MMPs) have been demonstrated to play a role in the formation of anterior subcapsular cataracts and it has been shown that the presence of MMP inhibitors (MMPI) decreases subcapsular cataract formation ex vivo. Since the mechanisms responsible for anterior subcapsular cataract formation and posterior capsule opacification are similar, it is reasonable to suggest that MMP inhibitors may also mitigate PCO. One of the most effective ways of delivering the inhibitors may be from the implanted intraocular lens (IOL) material itself. In the current work, delivery of three different MMP inhibitors from silicone rubber as a model IOL material was examined. Loading methods were developed which allowed continuous release of active MMPI for periods of over 5 months in some cases. Reduced migration rates were observed in human lens epithelial cells in vitro, suggesting that an effect on PCO may be possible. While further studies are necessary to tune the systems to achieve the desired rates of release, this work demonstrates that delivery of MMPI from silicone IOL materials has the potential to decrease the incidence of PCO.

Fig. 1

Light transmittance through PDMS materials at wavelengths within visual range. The values for transmittance are very high similar to those of the crystalline lens of a 4–5 year old child [50]. This indicates material is suitable as an IOL device.

Fig. 2

Release profiles of MMP inhibitors from PDMS. GM6001 release profiles reveal that HC and SOAK formulations have a similar high burst and constant release, while no visible difference is noted for the LC batch, when released in either TBS or PBS (A). In contrast, panel B shows that MMP 2/9 Inhibitor II shows a high burst only in the HC formulation, while the SOAK batch is releasing similarly to the LC formulation.

Fig. 3

Percentage release profiles of MMP 2/9 Inhibitor I, MMP 2/9 Inhibitor II and GM6001 outline the possible longevity of the drug-releasing IOL device. The HC formulations show the longest constant release, lasting over 145 days, while the LC formulations release all drug in 35–52 days. Notably, only the release profile of MMP 2/9 Inhibitor II LC is visibly affected by the release buffer, showing a potential longer release in TBS, compared to PBS. Also of interest, the MMP 2/9 Inhibitor I release profile has the longest expected lifetime, however, the current loading capacity of the device might not be sufficient, as this drug is needed in higher concentrations to have the same effect as its counterparts on the target enzymes.

Fig. 4

MMP inhibitors show little or no toxic effect on neighboring ocular cell types. There were slight decreases in the viability of FHL 124 cells remains unchanged with inhibitor treatment while only MMP 2/9 Inhibitor had a significant effect on the viability of B3 cells. While slight but significant decreases in viability were observed in HCE and RPE cells with inhibitor treatment, the corneal stromal fibroblasts were unaffected by even the relatively high concentrations of inhibitor used. Error bars represent standard deviation.

Fig. 5

The MMP inhibitors have the potential to significantly alter the expression of fibrotic markers. A) Treatment of the cells with TGFβ2 results in a significant increase in the expression of α-smooth muscle actin. However, presumably due to the relatively high basal production of this marker, only MMP 2/9 Inhibitor II was found to decrease expression in FHL 124 cells. Both inhibitors tested resulted in a significant reduction in expression in the B3 cells. B) The inhibitors were also able to reduce the amount of collagen I/III produced by B3 HLE in vitro after 48 h exposure to both drugs and TGFβ2. While TGFβ2 is capable of increasing the amount of collagen production, as expected, co-treatment with MMPIs reduce the amount of collagen even in comparison to untreated controls. Error bars represent standard deviation. * Indicates p < 0.0008; ○ indicates p < 0.009; • indicates p < 0.05.

Fig. 6

FHL 124 cell migration is significantly reduced with all prepared disk treatments. A 90 nm solution of GM6001 inhibitor does not significantly reduce migration, while a 90 nm solution of MMP 2/9 Inhibitor II has a very pronounced effect. Error bars represent standard deviation. * Indicates p < 0.0008; ○ indicates p < 0.009; • indicates p < 0.05.