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xiaodan huang, Maria J Lopez, Pedram Hamrah; Effects of Sensory and Sympathetic Innervation on the Corneolimbal Neurovascular Complex. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4499.
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The exact mechanisms of the interactions between corneal nerves and vasculature remain unknown. This study assessed the corneolimbal neurovascular complex and the specific effects of the sensory and sympathetic innervation on the corneolimbal vasculature.
Naïve corneas,including the limbus,of BALB/c mouse were excised, and whole-mounts were immunostained with anti-b-III tubulin, CD31, and Lyve-1 to evaluate the neurovascular anatomy of blood and lymphatic vessels, as well as nerves in the limbal areas by confocal microscopy. Substance P (SP) and tyrosine hydroxylase (TH) antibodies were used to stain sensory and sympathetic nerve respectively. Imaris software (Bitplane) was used to reconstruct the 3D structure of corneolimbal neurovascular complex. After unilateral trigeminal axotomy or superior cervical ganglionectomy (sympathectomy; SCGx), clinical changes in corneal transparency and neovascularization were evaluated by slit-lamp biomicroscopy. Axotomized, SCGx, contralateral, and sham-treated corneas were excised on postoperative days 1, 3, 7 and 14 and immunofluorescence was performed with anti-b-III tubulin, CD31, Lyve-1, SP, or TH. Analysis was performed with Neuron J to quantitify nerve density.
Sensory and sympathetic nerves were observed crossing, encircling, and running in parallel to blood and lymphatic vessels in the corneolimbal area. Trigeminal axotomy resulted in near complete loss of corneal nerves in the limbal area compared to sham controls and contralateral corneas (p<0.0001). After unilateral SCGx, loss of sympathetic nerves were shown in limbal area (p<0.0001). Unilateral trigeminal axotomy resulted in bilateral neovascularization in 100% of axotomy eyes (p<0.001) and 17% of contralateral eyes (p=0.47), which corresponded with 1.7 fold enlarged vascular caliper in axotomized eyes (p<0.0001). Interestingly, unilateral SCGx resulted in neovascularization in 50% sympathectomized eyes (p=0.009) and in 40% of contralateral eyes (p=0.02).
The current study demonstrates the spatial features of murine corneolimbal neurovascular complex. Unilateral trigeminal axotomy and sympathectomy led to loss of nerves in the limbal area and resulted in significant corneal neovascularization in both affected and unaffected eyes. Thus, sensory and sympathetic innervation may directly modulate blood flow and immune cells trafficking through regulation of the vasculature.
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