Abstract
Purpose :
Recently, our laboratory discovered a novel stereospecific Resolvin D6-isomer (RvD6si) released in tears that is activated by pigment epithelium-derived factor (PEDF) plus docosahexaenoic acid (DHA) upon corneal injury. RvD6si promotes corneal functional recovery by restoring the high-density innervation. Here, we explored the stimulation by RvD6si of the transcriptome of the trigeminal ganglion (TG) to elucidate the mechanism that fosters corneal nerve regeneration.
Methods :
Eight-week-old male CD1 mice were used. Corneal epithelium from the right eye was removed from a 2mm diameter surface under anesthesia. Then, corneas were treated topically with vehicle, RvD6, and RvD6si three times per day. Two weeks after treatment, the ipsilateral TG was dissected and analyzed for gene expression using RNA-sequencing. Differential gene expression analysis was done using DESeq2 and significantly changed genes were subjected to Ingenuity Pathway Analysis (IPA).
Results :
Among treatment conditions, the RvD6 and RvD6si shared 58 upregulated genes and 36 downregulated genes compared to vehicle-treated corneas. The upstream predicted results from IPA software unraveled a strong induction by RvD6si of a transcriptional factor named Rictor, a key component of the rapamycin-insensitive complex 2 of mTOR (mTORC2). There were 39 genes modulated by RICTOR significantly changed by the treatment. Among those genes, 37 (95%) genes matched the IPA knowledge collected from published data. Additionally, the RNA-seq also demonstrated that RvD6 treatment (both RvD6 and RvD6si) reduced the gene expression of two major neuropeptides, tachykinin precursor 1 and calcitonin-related polypeptide beta, that were regarded as major pain-induced mediators in migraines and other primary headaches and increased the expression of transient receptor potential melastatin 8 (TRPM8), a cold receptor important to maintaining tear secretion and control neuropathic pain after surgery.
Conclusions :
This study unraveled the role of Rictor signaling in the cell bodies of TG to foster the nerve innervation in the cornea after injury and treatment with RvD6si. Furthermore, the expression of genes related to neuropathic pain are decreased while TRPM8 is increased. The new RvD6si uncovers new therapeutic avenues for corneal pathologies that affect tissue innervation.
This is a 2020 ARVO Annual Meeting abstract.