The miR-183/96/182 Cluster Regulates Trigeminal Ganglion Sensory Neurons' Response to

Purpose: To uncover the molecular mechanisms of corneal sensory nerves (CSN)'s involvement in the initiation of Methods: miR-183C conventional knockout (KO) or sensory neuron-specific (SNS) conditional (C)KO mice and their age- and sex-matched wild type (WT) controls were used. TG SN were isolated. Neurite growth and branching were analyzed by neurite tracing. Custom-made microfluidic chambers (MFC) were used to separate the neuronal cell bodies in the soma chamber and their neurites/nerve endings in the axon chamber. TG SN's response to lipopolysaccharide (LPS) or PA infection of the neurites/nerve endings was studied by ELISA assays of CX3CL1 and substance P (sP) in the axon chamber. Target luciferase reporter assays were performed to validate key downstream target genes of miR-183C. Results: The total neurite length and number of branches per TG SN were decreased in the CKO vs WT mice, and in the male vs female WT mice. PA infection, but not LPS alone, induced the production and secretion of CX3CL1 and sP in WT mice; while TG SN of miR-183C KO mice responded to both LPS and PA and were significantly enhanced when compared to WT mice. Antagonists to TLR4 and/or FPR1 inhibited PA-induced responses. Target luciferase reporter assays confirmed that genes encoding NRP1, TAC1- the precursor gene of sP, CX3CL1 and ADAM10, a metalloproteinase involved in the production of soluble CX3CL1, were direct targets of miR-183C. Conclusions: PA directly activates TG SN and induces chemokine and neuropeptide production/secretion through TLR4 and FPR1 receptors, which may contribute to the initiation of PA keratitis. miR-183C regulates TG SN neurite growth, chemokine and neuropeptide production/secretion and the response to PA infection by targeting a collection of key genes involved in axon guidance/projection-, chemokine and neuropeptide biogenesis- and receptors mediating PA-induced activation.