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Published on: April 24, 2020
Transcorneal Freezing in Aged Rabbits as a Platform for Evaluating Corneal Endothelial Cell Therapeutics
Lauren E Cornell1, Eric J Snider1, Jennifer S McDaniel1
1Sensory Trauma Research Division, United States Army Institute of Surgical Research, Fort Sam Houston, TX.
Purpose:
Transcorneal freezing is a common technique used in rabbits to induce damage to the corneal endothelium. Previous studies have been performed with a range of freezing temperatures, times, and rabbit ages. Here, we aimed to characterize the aged rabbit endothelium after transcorneal freezing to establish an innate corneal endothelial cell regrowth rate and propose it as a mechanism for evaluation of therapeutic efficacy in rabbit models.
Methods:
Central corneas of anesthetized New Zealand White rabbits (n=3) aged 18-24 months were exposed to nitrous oxide cooled probes for 30 seconds. Animals were assessed by in vivo confocal microscopy, applanation tonometry, specular microscopy, optical coherence tomography, and histology. The contralateral eye acted as a control. Images were taken immediately before and after injury and on days 2, 4, 7, 11, and 14.
Results:
Following transcorneal freezing, there was a significant decrease in corneal endothelium density and a temporary increase in corneal thickness. Endothelial density decreased by 95% immediately after injury compared to controls and showed linear recovery over 14 days, reaching a 38% reduction by day 14. There was a significant increase in pleomorphism across all time points post-injury. Conversely, corneal thickness increased two days post injury but recovered at all later time points. Intraocular pressure was not affected throughout.
Conclusions:
This corneal endothelium injury platform is ideal for injury and therapeutic research as it can be rapidly performed, and has minimal impact on corneal thickness and intraocular pressure. Due to innate rabbit endothelial regrowth, it is vital to establish corneal endothelial recovery rate before evaluating therapeutics for efficacy in this model system.
Insights
Transcorneal freezing in aged rabbits causes significant corneal endothelium damage but shows innate cell regrowth. Establishing this recovery rate is crucial for evaluating new eye injury therapies.
Area of Science:
- Ophthalmology
- Regenerative Medicine
- Animal Models
Background:
- Transcorneal freezing is a standard method for inducing corneal endothelium damage in rabbits.
- Previous research has explored various freezing parameters and rabbit ages.
Purpose of the Study:
- To characterize the aged rabbit corneal endothelium response to transcorneal freezing.
- To establish the innate corneal endothelial cell regrowth rate in aged rabbits.
- To propose this model for evaluating therapeutic efficacy.
Main Methods:
- Aged New Zealand White rabbits (18-24 months) underwent transcorneal freezing using nitrous oxide cooled probes for 30 seconds.
- Corneal assessments included in vivo confocal microscopy, specular microscopy, OCT, tonometry, and histology.
- Contralateral eyes served as controls, with imaging at multiple time points post-injury.
Main Results:
- A 95% decrease in corneal endothelium density was observed immediately post-injury, with 38% reduction by day 14, indicating linear recovery.
- Corneal thickness temporarily increased but normalized by day 14.
- Increased endothelial pleomorphism was noted throughout the study period; intraocular pressure remained unaffected.
Conclusions:
- The transcorneal freezing model in aged rabbits is suitable for corneal endothelium injury and therapeutic research.
- The model demonstrates rapid injury induction with minimal impact on corneal thickness and intraocular pressure.
- Understanding the innate corneal endothelial cell regrowth rate is essential for accurate therapeutic efficacy assessment in this model.
