Designing an innovative bioreactor destined to improve the endothelial viability of stored corneas

Abstract

Purpose: Corneal physiology is highly dependent on the intraocular pressure (IOP) and endothelial functions. Loss of IOP after death and after corneo-scleral procurement triggers a vicious circle with stromal swelling causing posterior folds in which endothelial mortality is increased resulting in impaired barrier functions that accentuate stromal swelling. We hypothesized that restoration of IOP after procurement will be key in creating a favourable environment for long-term corneal storage with preserved endothelial functions necessary for research works as well as for eye banking

Methods: Using machining of PMMA and polycarbonate, 3D printing and mecatronic technologies, we designed two bioreactors (BR) (for human and porcine corneas) and their control units. Contrary to previous perfusion chambers or artificial anterior chambers destined for physiology or toxicology studies, we designed a closed-loop system with transparent windows allowing observation for both the epithelial and endothelial sides. Sterile sampling sites were added in the circuit for monitoring physiochemical parameters as well as sterility without risk of contamination

Results: The BR presented as a sterile disposable cassette comprising a corneal chamber surrounded by the fluidic system comprising the storage medium tank (sufficient for 5 weeks), tubing, a pressure sensor, a micro valve, and a waste. After insertion of the corneo-scleral rim, the system was closed and the cassette connected to its control unit, comprising a peristaltic pump driven by a microcontroller. The first version could drive 3 to 5 BR. The medium flow could be adjusted (typically 0.16 mL/hour for human corneas) and the IOP could be individually adjusted between 10 to 40 mmHg (for research works). If necessary (for instance when using a storage medium requiring 5% CO₂ to ensure pH stability) the BR could be installed in a classical CO₂ incubator. If necessary, the epithelial chamber could be filled with air while keeping the IOP

Conclusions: The innovative BR restores IOP while ensuring a continuous medium renewal in a fully transparent chamber. A closed, sterile, nearly physiologic environment is actively controlled. The BR will be available for eye banks, research laboratories, contract research organizations, and cosmetic industry.<br /> Grants: EFS, ANSM