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Claudia Brockmann, Sabrina Dege, Norbert Kociok, Tobias Brockmann, Olaf Strauss, Antonia M Joussen; Influence of systemic C5a on CD11b positive cells and their activation during oxygen-induced retinopathy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2050. doi: https://doi.org/.
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The complement system is known to be involved in pathological retinal neovascularization as it occurs in oxygen-induced retinopathy (OIR). Thereby, the VEGF-stimulating anaphylatoxin C5a is of special interest. The aim of our study was to investigate the influence of systemic C5a on retinal neovascularization and CD11b positive cells with regard to their activation status.
C57BL/6 mice were exposed to 75% oxygen from postnatal (P) day 7 to 12 for OIR induction. Daily intraperitoneal injections of C5a were given from P12 to P16, equal volumes of phosphate buffered saline (PBS) were used for controls. Retinal vascularization and distribution of CD11b positive cells was investigated on retinal flatmounts at P14, P17 and P21 (n = 6-8 eyes per group and analyzed time point) using isolectin B4 staining and CD11b antibodies. Cells were quantified in predefined areas and compared between the injection groups separately for each area of vascularization. In addition, the amount of morphologically activated CD11b positive cells was determined and analyzed likewise.
The vascular area was significant reduced by one third in the C5a group at P17 (p < 0.05), no differences were found at P14 and P21. Thereby, the total number of CD11b positive cells was significantly reduced by one third in avascular and tuft areas at P17 (p < 0.01) and by a quarter in tuft areas at P21 (p < 0.05). Regarding the activated CD11b cells after C5a-treatment, the number was significantly reduced by a half in avascular areas at P14 and by one third in tuft areas at P17 compared to PBS controls (p < 0.01, respectively).
Systemic C5a influences the distribution of CD11b positive cells and their activated proportion in pathological retinal vascularization in the OIR model. Therefore, we presume an interaction between C5a and activation status of CD11b positive cells that is relevant for oxygen-induced retinopathy. The clarification of this mechanism is matter of further investigations.
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