Abstract
Purpose :
Corneal nerves are known for their ability to regenerate following ocular surface injury; however, the underlying mechanism of peripheral neuronal regeneration are not fully understood. Recently, our laboratory has demonstrated that ocular surface injury results in a reduction in the levels of Dicer1, an RNA-processing enzyme, with subsequent elevation of non-coding Alu-RNA levels in the trigeminal ganglion (TG). Here, we sought to investigate the role of Alu-RNAs in corneal nerve regeneration.
Methods :
To test the effects of overabundance of non-coding Alu-RNAs on axonal regeneration, Dicer1 dysmorphic (Dicer1 dys) mice, which have lower than normal levels of Dicer1, were studied. Ocular surface injury was induced by applying a 2mm-diameter circular filter paper soaked in 2N NaOH solution to the cornea. The whole-corneas were harvested 4 days post injury, and then corneal nerves were visualized via immunofluorescence. In addition, the effects of non-coding Alu-RNAs on primary TG satellite glial cells (SGCs) were studied in terms of NLRP3 inflammasome activation and expression of neurotrophic factors, using western blotting and quantitative PCR.
Results :
In the absence of ocular surface injury, Dicer1 dys mice and their litter mates have similar corneal nerve density and length. However, 4 days after ocular surface injury, Dicer1 dys mice showed a more robust re-innervation response with longer corneal nerves, indicating faster axonal regeneration in Dicer1 dys mice compared to their litter-mate controls. Interestingly, in vitro studies showed that Alu-RNAs stimulate SGCs to produce neurotrophic factors via activation of the NLRP3 inflammasome.
Conclusions :
These findings suggest that non-coding Alu-RNAs play an important role in peripheral nerve regeneration after ocular injury. In particular, these non-coding RNAs stimulate SGCs to produce neurotrophic factors via activation of the NLRP3 inflammasome. Whether accelerated nerve regeneration would be beneficial for functional recovery still needs to be understood; however, manipulating non-coding Alu-RNAs may be a potential therapeutic strategy to delay or speed up axonal regeneration.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.