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Thang Luong PHAM, Azucena H Kakazu, Jiucheng He, Haydee E P Bazan; Nerve regeneration in mouse corneas correlates with stimulation of specific neurotrophins and semaphorin 7A. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4914. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies in our laboratory have shown that pigment epithelial derived factor (PEDF) and the 44-mer PEDF peptide in association with docosahexaenoic acid (DHA) stimulates nerve regeneration in rabbit cornea. However, the mechanism of axonal regeneration is not completely understood. Here, using the mouse cornea as a model, we investigated what neurotrophins and related genes could be targets for treatment using (1) PEDF + DHA, (2) 44-mer of PEDF + DHA and (3) neuroprotectin D1 (NPD1), a downstream derivative of DHA.
Mouse corneas were topically anesthetized and injured by rotating a 2 mm trephine to cut the nerves at the stromal level. After injury, topical treatment with 5 µl of 50 ng/ml PEDF + 50 nM DHA, 5 ng/ml 44-mer PEDF + DHA, 50 nM NPD1 or vehicle was applied every 30 min for 3 hours. Total RNA from dissected corneas was extracted and quantified by real time-PCR using specific primers designed in our laboratory. To investigate the secretion of neurotrophins, injured corneas were incubated in organ culture DMEM/F12 medium supplement with treating compounds for 24 and 48 hours. Expression level was analyzed by Western blot.
There were five neurotrophins, one neurotrophin receptor and one semaphorin highly elevated by all the treatments, in comparison to the vehicle control. The genes were increased as follows: Corticotropin releasing hormone binding protein (Crhbp), 3.6 fold; Fibroblast growth factor 2 (Fgf2), 2.4 fold; Glial cell line-derived neurotrophic factor (Gdnf), 2.5 fold; Neuregulin 1 (Nrg1), 8.8 fold; and Nerve growth factor (Ngf), 2.5 fold. In parallel, a higher secretion ability of these neurotrophins was observed in the corneal tissue culture in a similar manner. Although semaphorin 7A was the most activated gene (more than ten times fold), its secretion was about two times higher.
The increase at the transcriptional and translational level of these neurotrophins (CRHBP, FGF2, GDNF, NGF and NRG1) and semaphorin 7A correlates with nerve regeneration stimulated by PEDF, 44-mer PEDF plus DHA, and NPD1. Our results suggest that they are important factors in the axonal regenerative action in the mouse cornea.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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