gms | German Medical Science

Loss of vision in AMD is mainly due to the development of choroidal neovascularization (CNV), which is partly driven by macrophages and microglia that both carry VEGFR1 (flt-1) receptors specific for VEGF-A and PlGF. A switch from a pure anti- VEGF-A to an anti-PLGF+VEGF-A treatment is beneficial for some patients. We hypothesize a regulation of microglia activity in the retina by PlGF that contributes to the pathophysiology of CNV. We used the model of laser-induced CNV in MacGreen (Csf1r-EGFP) mice, creating 5 laser spots around the optic nerve (argon laser, 120mW, 50µm, 100ms). Microglia was visualized in vivo by scanning laser ophthalmoscope autofluorescence (AF) and ex vivo by using Iba-1. Differential expression of several angiogenic factors and macrophage markers was analyzed 1h and 1, 4 and 10 days after laser by qPCR. Protein expression of PlGF and VEGF-A was detected both in sagittal sections and in whole-mounts of the retina. We found a substantial up-regulation of PlGF mRNA expression at D1 that decreased back to normal levels at D4. However, VEGF-A expression did not increase during the early phase (D1) and even decreased at D4. sFlt-1 mRNA expression showed an instant increase 1h after laser. At D14, in sagittal sections or retina whole-mounts, we observed that up-regulation of VEGF-A expression in response to laser impact is limited to the scar area, while PlGF shows a more homogenous distribution. Additionally, comparable to PlGF expression, activated microglia cells were also present in distant areas from the laser-spots. Among macrophages, we found an increase of M1 (pro-inflammatory) markers (CD68 and CD86) until D4 whereas the M2 marker IL4R did not show significant changes. Thus we show first hints that a combined action of PlGF and microglia plays an important role in the initial phase of CNV after laser.