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Tomas Blanco, Arsia Jamali, Maria J Lopez, Hamid-Reza Moein, Pedram Hamrah; Plasmacytoid Dendritic Cells Are Essential for Nerve Repair in a Mouse Model of Corneal Injury. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3327.
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Plasmacytoid dendritic cells (pDCs) play a main role in linking innate and adaptive immune responses. Our group has recently shown that pDCs are essential for corneal homeostasis. Herein we aim to investigate the corneal homing mechanism of pDCs and their role in neuronal repair
Isolated bone marrow pDCs of naïve mice were analyzed by flow cytometry for 12 surface markers. Competitive homing of pDCs was evaluated in inflamed corneas of C57BL/6 mice. Each mouse received 5x106 CFSE-stained donor pDCs blocked by antibodies to α4β7, LFA-1, or CXCR4, as well as 5x106 CMTMR-stained pDCs incubated with respective IgGs. Corneas were imaged 24 hours later for donor pDCs by multiphoton intravital microscopy. Real-time intravascular adhesion of adoptively transferred pDCs, blocked with either anti-a4b7 antibody or IgG, was performed in inflamed pericorneal vessels by using an epi-fluorescent intravital microscopy. Both rolling fraction and sticking efficacy were assessed. Corneal trephination was performed in BDCA2-DTR transgenic mice or wild-type controls. pDCs were depleted by systemic injection of 100ng of diphtheria toxin. No cells or pDCs incubated with either IgG or α4β7 blocking antibody were systemically injected. After 4 weeks, corneal explants were stained with Tuj1-Alexa-568, imaged by confocal microscopy and subbasal nerve density measured using NeuronJ software
α4β7>LFA-1>CXCR4 showed the highest expression from all markers in pDCs. The number of imaged CFSE+ cells were significantly reduced (2.3±0.9 cells/field; p<0.001, α4β7), (3.1±1.9, p<0.001, LFA-1) and (4.5±2.7, p<0.001,CXCR4) in contrast to CMTMR+ cells (12.9± 3.7, IgG). Similarly, rolling fraction was significantly decreased in a4b7-blocked pDCs (5.5%, p<0.001) compared to IgG controls (34%). Sticking efficacy was inhibited by blocking α4β7 (0%) compared to IgG controls (15%). Subbasal nerve density (mm/mm2) was impaired in pDC-depleted mice without transferred pDCs (15.3±2.8, p<0.0001) or with transfer of α4β7-blocked pDCs (28.7±7.4, p<0.0001), but enhanced with transfer of control IgG blocked pDCs (72.1±4.8, p=0.012) compared to naïve cornea (95.5±5.4)
This study demonstrates, for the first time, that pDC expression of α4β7, LFA1 and CXCR4 is essential for their corneal homing and that their blockade impairs nerve outgrowth. Together these results suggest that pDCs are critical for corneal nerve repair
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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