Abstract
Purpose :
Visual corrective surgical procedures (e.g. LASIK) and corneal transplants that cause severance of stromal axons often result in aberrant axonal regeneration with impaired corneal sensation. Corneal Schwann cells (cSCs) were examined for their trophic support of axonal regeneration post injury. We investigated a novel small molecule drug micellar formulation RM4404 that targets cSCs to examine axonal regeneration and sensation recovery in a model of stromal axonopathy.
Methods :
A stromal micropocket was surgically created in mouse corneas to model stromal axonopathy using the transgenic Plp1-egfp line, which genetically marks cSCs. Endogenous GFP fluorescence and immunostaining for beta III-tubulin was used to ascertain the cSC and axonal networks, respectively. Mice were entered into two study arms (A and B). In arm A, injured mice were treated topically with micellar RM4404 or vehicle (Kolliphor HS-15) twice daily from 7 to 14 days post-injury (dpi). In arm B, treatment parameters were kept the same, but mice were subjected to corneal mechanosensory testing with Cochet-Bonnet esthesiometer prior to injury, and at 7, 14, and 30 dpi. Axonal and cSC network images were acquired by epifluorescence microscopy. Tiled images were then quantified using FIJI software with neuroanatomy plugin and statistical analysis (t-test and ANOVA) was performed.
Results :
The cSC network shows a u-shaped curve post injury with maximal degeneration occurring at 7 dpi (P<0.0001) followed by a rapid recovery by 14 dpi (P<0.0001) and stabilizing by 30 dpi. However, the axonal network lags behind the cSC network, remaining significant even at 30 dpi (P<0.0001). At 7 dpi there is also significantly decreased corneal sensation (P<0.0001) which remains attenuated at both 14 and 30 dpi in vehicle-treated corneas (P<0.0001; P=0.002). In contrast, RM4404-treated corneas showed significant recovery of sensation at both 14 and 30 dpi (vehicle vs RM4404; P=0.0007; P=0.0002), achieving levels similar to uninjured mice.
Conclusions :
By defining the kinetics of cSCs and axonal degeneration/regeneration, we have determined the active regenerative phase of cSC growth. We have capitalized on this novel finding to pharmacologically stimulate the restoration of corneal sensory function using the novel drug RM4404 that targets cSCs. This study is the first of its kind to specifically target cSCs and demonstrate a therapeutic benefit in a model of stromal axonopathy.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.