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Naomi Bennett, Lisa J Hill, Ghazala Begum, Liam Grover; Novel calcium chelating agent for the treatment of corneal mineralisation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2093.
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© ARVO (1962-2015); The Authors (2016-present)
Current treatments to remove mineral build-up in the cornea associated with band keratopathy involve removing the epithelial layer and dousing the affected area with 1% EDTA solution. This is normally performed as an out-patient procedure. Although this method has shown high efficacy, there is considerable trauma to the epithelial layer. If other chelating agents with enhanced penetrative ability could be used to remove the mineralisation, without the associated trauma to the epithelial layer, the invasiveness of the treatment could be reduced. In this study, we investigated the capacity of sodium hexametaphosphate to mediate this de-mineralisation process.
The influence of solutions of sodium hexametaphosphate and EDTA on the surface of the cornea were compared using in vitro and ex vivo models. The concentrations tested were clinically relevent. In vitro cell toxicity of both solutions on primary human corneal fibroblasts and epithelial cells were investigated using cell proliferation (CyQuant) and cell metabolism (MTT) assays. For the ex vivo assessment of corneal penetration and tissue damage, both chelating agents were applied to the anterior surface of porcine corneal samples. Hemotoxylin and eosin (H+E) and DAPI stains were used to assess the health and structure of the cell layers and compare to chemical damage (sodium hydroxide) controls. Corneal penetration was assessed using fluorescein staining and compared to untreated controls. The demineralising effect of both chelating agents was assessed in vitro using a nanohydroxyapatite sol.
HMP was shown not to compromise the viability of human corneal fibroblasts at concentrations of up to 2mM as determined using the MTT assays. This concentration did not change the pH value of the media sufficiently to modify its colour, whilst still enabling demineralisation of the HA sol. Importantly, the HMP was shown to have superior and safer corneal penetration compared to EDTA, with EDTA causing chemical insults to the epithelial layers.
HMP demonstrated suitable hydroxyapatite demineralisation, corneal penetration and superior cell and tissue viability compared to EDTA. HMP presents as a possible alternative chelating agent to EDTA in the treatment of corneal calcification, which may prevent epithelial trauma whilst still maintaining effective levels of demineralisation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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