Integration of transepithelial electrical resistance (TEER) measurement in the corneal bioreactor

Purpose The corneal bioreactor (BR) patented by our laboratory allows to restore a physiological epithelium of porcine or human corneas. The measurement of the transepithelial electrical resistance (TEER), correlated with the presence of tight junctions, is a robust parameter for assessing the integrity of the corneal epithelium. Aim To integrate the measurement of TEER with BR and to evaluate its relevance on porcine corneas. Methods Two Ag/AgCl electrodes (WPI, Saratosa, FL) were placed, one in an endothelial chamber filled with Corneamax storage medium (Eurobio, Les Ulis, France), the other in an epithelial chamber and under 3 conditions: immersed in the conservation medium; immersed in the conservation medium while isolating the cornea from the sclera thanks to an applicator cone usually used for iontophoresis (Opia Technologies, Paris, France); in direct contact with the epithelium with interposition of Gel‐larmes (Théa, Clermont‐Ferrand, France). The electric current frequencies tested ranged from 50 Hz to 1 MHz. Three fresh pig corneas (with and without epithelium) were placed in BR and the TEER measured in the 3 conditions, with and without epithelium. Controls: Fresh pig sclera and Corneamax alone in BR. Results Results are expressed as median. TEER of controls: 302 Ω (sclera) and 266 Ω (Corneamax alone) TEER of corneas without epithelium: 321 Ω, in the 3 experimental conditions, thus close to the control. TEER of corneas with epithelium: 397 Ω with electrode immersed in the medium, thus close to the sclera (397 Ω). In the other 2 conditions, the TEER was higher, with a greater variability, depending on the current frequency: from 1456 Ω to 143 Ω with the applicator cone and from 2335 Ω to 242 Ω with the Gel‐Larmes. Conclusions The sclera placed in BR is a conductive tissue. It is possible to determine the TEER of a cornea ex vivo in the BR, if the cornea is isolated from the sclera and the epithelium present on the cornea is healthy.