Abstract
Purpose :
Determine the expression and neurogenic potential of axon guidance proteins in the cornea.
Methods :
The expression of axon guidance proteins belonging to the Semaphorins, Ephrins and Netrins families of proteins, and their associated receptors were evaluated by RT-qPCR and immunofluorescense staining (IF) in mouse trigeminal ganglia and cornea tissues. Corneas (n=3 per condition) were subjected to epithelium debridement and the recovery of gene and protein expression was analyzed at 0, 1, 3, 5, 7 and 14 days post injury. Gene expression was evaluated using predesigned mouse TaqMan gene expression assays using validated internal controls. Protein expression was analyzed by immunofluorescence staining, tissue cryosections were incubated with antibodies against different members of axon guidance proteins and imaged under a fluorescent microscope. The epithelium and subabsal nerves regeneration of injured corneas were evaluated in mice treated with axon guidance recombinant proteins and compared to vehicle controls. Slit lamp, Von Frey filaments and B3 tubulin staining were used to determine the epithelium recovery, nerve sensation and nerve regeneration respectively.
Results :
We found that all axon guidance proteins evaluated are expressed in the trigeminal ganglia and cornea epithelium. In the trigeminal ganglia all proteins were found in the neuronal cell body and few of them were expressed in the axons projecting to the cornea. The receptors that are usually associated with these proteins such as Neuropilins, Plexins and VEGFRs were also present in both tissues with certain degree of variation. After corneal epithelium injury there was a fast recovery of axon guidance proteins gene expression. They initially colocalized within the basal cells in the epithelium and remained in the first two epithelial cell layers after two weeks post injury. Two of the axon guidance proteins studied in vivo, significantly enhanced nerve regeneration and may have pleitropic effects since the induce neuronal growth on isolated neurons and accelerate epithelium recovery in scratch assays.
Conclusions :
Axon guidance proteins are crucial for axonal targeting in the eye. In the adult cornea they are highly expressed in the steady state and quickly upregulated after injury. Their trophic and neuro-regenerative effects indicate that they may be essential for cornea repair.
This is a 2021 ARVO Annual Meeting abstract.