Evaluation of 2 ex vivo Bovine Cornea Storage Protocols for Drug Delivery Applications

Abstract

The use of corneal tissue for ex vivo therapeutic evaluations is limited due to its rapid loss of viability after excision. Optimization of storage conditions may allow prolonged retention of physical tissue properties. In this study, we evaluated how storage in optimized organ culture (OC) medium at 37°C or phosphate-buffered saline (PBS) at 2–8°C impacted physical properties of bovine corneas. Tissue hydration, permeability and histology were monitored at baseline and following 1, 4 and 7 days of storage. Corneas stored in OC demonstrated significantly higher hydration and permeability when compared to those stored in PBS. Histology revealed that storage in OC consistently caused detachment of the epithelial layer by day 4 of storage, whereas both storage conditions caused a significant increase in stromal thickness and tissue vacuolation. This study highlights the limitations of currently available corneal tissue storage approaches for ex vivo drug permeation studies.

Ex vivo evaluation of the stability, safety and antibacterial efficacy of an extemporaneous povidone‐iodine preparation for ophthalmic applications

“…All corneal tissue samples were immersed in tissue freezing medium and snap frozen using liquid nitrogen. Sections of 20 μm were obtained using a cryostat microtome (Cryostar NX50, Thermo Fisher Scientific) and mounted on Menzel‐Gläser Superfrost Plus slides (Thermo Fisher Scientific) before staining with haematoxylin and eosin as previously described . Sections were viewed under a light microscope (NIS‐Elements BR software, Nikon Instruments, Inc., Melville, New York, USA) and evaluated for signs of tissue damage.…”

In Vitro and Ex Vivo Models for Assessing Drug Permeation across the Cornea

“…Hans Ussing initially developed the Ussing chamber to measure the transport of nutrients and ions across various epithelial membranes . More recently, modified Ussing chambers such as the Navicyte/Harvard Ussing system have been used in corneal drug diffusion studies. − It is designed in such a way that each side of the cornea faces another chamber-half, with the cornea being positioned between the chamber halves using a series of pins surrounding the opening (Figure B). The addition of electrodes allows for the performance of electrophysiological measurements, such as the measurement of corneal transepithelial electrical resistance.…”

“…161 Unfortunately, ex vivo corneas lose their integrity quickly, limiting their use to a few hours post-mortem. 146 To overcome this limitation, Rousou et al developed an arterially perfused ex vivo porcine model, in which the eye can be kept "alive". This model is based on ophthalmic artery cannulation, which allows for total eye perfusion.…”