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C. Yabuta, Y. Takayama, T. Nakajima, Y. Minagawa, T.R. Shearer, M. Azuma; Neurite Outgrowth of Cultured Trigeminal Nerve Cells and Reinnervation After Corneal Flap Creation in Rabbit by PACAP27 . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5576.
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Innervation by trigeminal nerves maintains normal function and architecture of sensitive tissue cornea. Laser in situ keratomileusis (LASIK) refractive surgery has been well used in therapy for myopia. During LASIK surgery, however, flap creation causes nerve amputation, and sensory function is disrupted in cornea. This disruption is thought to cause tear film alteration and dry eye, which are common complications of LASIK surgery. Pituitary adenylate cyclase–activating peptide (PACAP), which is a member of the VIP super family, induces neurite outgrowth and protects against neurotoxicity. The purpose of the present experiment was to determine if PACAP could induce neurite outgrowth in cultured trigeminal nerve cells and lead to recovery of innervation after creation of a corneal flap in the rabbit.
Trigeminal nerve cells isolated from rabbits were cultured for 48 hours with or without a 27–amino acid form of PACAP (PACAP27). Cells with neurite outgrowth were counted after cells were fixed with 4% paraformaldehyde and immunolabeled with anti–neurofilament antibody, and data were expressed as percent of total cells. A microkeratome produced 130 µm–thick by 8.5 mm–wide hinged, corneal flaps in rabbits. PACAP27 eye drops were applied 4 times a day for 8 weeks. As a marker for innervation, corneal sensitivity was measured by a Cochet–Bonnet esthesiometer. Corneal neurons were also observed under the microscope. RT–PCR was performed to detect PACAP receptors in the trigeminal nerve from rabbits.
One micromole of PACAP27 induced neurite outgrowth in primary cultured trigeminal nerve cells. Administration of 0.003% PACAP27 eye drops accelerated recovery of corneal sensitivity after corneal surgery. Elongation of trigeminal neurite in cornea was also confirmed. Receptors of PACAP such as PAC1, VPAC1 and VPAC2 were expressed in trigeminal nerve from rabbit.
These results suggest that PACAP27 is a potential candidate drug for improvement of dry eye following LASIK surgery.
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