Permeability of Porcine Ocular Tissues at Different Stages of Development

Abstract

 

Purpose

 

Investigation of the permeability of ocular tissues at different stages of development is important for understanding physiological conditions of the eye and developing strategies to enhance drug permeability across these tissues for treating many ocular diseases. The objective of this study is to study the permeability along with corresponding morphology of the porcine sclera and the cornea at different stages of development.

 

Methods

 

Sclera and cornea tissues were isolated from fresh eyeballs of 28 week preterm and 1 week old normal term. The thicknesses of the tissues were measured. The tissues were placed in the spherical joints of Valia-Chien Cell apparatuses. Fluorescein isothiocyanate (FITC) labeled 4k-dextran was dissolved in respective media for the ocular tissues and added to the donor chamber at 1 mg/mL. Passive transport of the FITC-dextran across the sclera and cornea tissues was carried out at 34°C over 4 hour period of time. Samples were taken out from the receptor chamber as a function of time. The fluorescence intensities in the solutions sampled from the donor and receptor chambers were quantified using a fluorescence microplate reader. The permeability (P0) of the FITC-dextran across the sclera and cornea tissues was calculated. The TER values of the ocular tissues were monitored through the whole permeability studies. Currently, we are measuring the permeability of the FITC-dextran across adult pig sclera and cornea tissues, and the morphologies of all the above mentioned ocular tissues at different development stages using a scanning electron microscope.

 

Results

 

The thickness of the preterm sclera was thinner than that of the normal term sclera; while there was no difference between the thicknesses of the preterm and normal term corneas. The transsceleral permeability across the preterm sclera was significantly higher than that of the normal term sclera (Figure 1). However, the transcorneal permeability across the preterm and normal term piglet corneas showed no significant difference (Figure 2).

 

Conclusions

 

The development stages of pigs affect the permeability of ocular tissues depending on the tissue types. These studies provide insight on how to design drug delivery systems to enhance drug permeability across ocular tissues at different development stages.

 

 

Figure 1. Permeability of 4k FITC-dextran across the sclera.

 

 

Figure 2. Permeability of 4k FITC-dextran across the cornea.

 

Keywords: 708 sclera • 480 cornea: basic science