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Anne Bukowiecki, Claus Cursiefen, Sabine A. Eming, Deniz Hos; Phase-specific functions of macrophages in inflammatory corneal angiogenesis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3335. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Macrophages have been identified as essential mediators of inflammatory corneal hemangiogenesis (HA) and lymphangiogenesis (LA). However, it is unknown if these cells exert different hem- or lymphangiogenic potency during diverse phases of corneal inflammation and repair. Macrophages might not only take part in the induction of vascular sprouts but promote the maintenance of existing corneal vascular structures and neovessels. We therefore performed stage-specific depletion of macrophages (in early, midstage or late stage of the corneal vascular response after injury) to better characterize the functional relationship between macrophages and corneal vascular growth.
Six to eight week-old female Balb/c mice underwent intrastromal corneal suture placement. Sutures were left in place for 14 days. Macrophages were depleted by subconjunctival injections of clodronate liposomes, while control animals received PBS liposomes every 2 days. Depletion was performed in different phases after injury, either in early stage (day 0-7), midstage (day 7-14) or after suture removal in late stage (day 14-21) or advanced stage (day 28-35). To quantify corneal neovascularization, corneas were immunohistochemically stained for blood vessels (BV) and lymphatic vessels (LV) using the vascular markers CD31 and LYVE1. The percentage of corneal area covered by BV/LV was evaluated by digital image analysis.
Ablation of macrophages had different outcome regarding corneal HA and LA: Depletion of early stage macrophages strongly reduced the extent of inflammatory HA (28.14 % vs. 9.92 % p=0.079), while mid- (23.27 % vs. 18.08 % p=0.01) and late stage (17.40 % vs. 14.63 % p=0.04) depletion decreased HA to a lesser extent. In advanced stage, regression of BV was not accelerated in macrophage depleted corneas (13.20 % vs. 12.89 %). Overall the effect of macrophage depletion on LA was more pronounced. Early stage (6.18 % vs. 1.51 %, p=0.079) and midstage depletion (6.8 % vs. 2.37 % p= <0.0001) markedly reduced the progression of corneal LV, while late (6.48 % vs. 4.56 % p=0.008) and advanced stage (4.76 % vs. 3.42 % p=0.005) macrophage depletion led to a faster regression of corneal LV.
Early and midstage macrophages are required for BV and LV progression in intrastromal suture placement, while late stage macrophages appear to be involved in maintenance of corneal LV but not BV.
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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