Activated Macrophages Induce Neovascularization Through Upregulation of MMP-9 and VEGF in Rat Corneas

Purpose: To explore the mechanisms of activated macrophages (A-Mu) involved in corneal angiogenesis. Methods: Activated macrophages were elicited by mineral oil lumbar injection and implanted into corneal micropockets in rats for the treatment group, A-Mu, and phosphate-buffered saline group as control. Corneal changes were observed with a slit lamp microscope, and histopathological features were evaluated by immunofluorescence. Reverse transcription-polymerase chain reaction was used to detect the relative expression of angiogenesis-associated factors and inflammatory mediators in the activated macrophages and corneal tissue after implantation. Results: Immunofluorescence showed that peritoneal cells expressed antigens of cluster of differentiation 68 (CD68, ED1), matrix metalloproteinases-9 (MMP-9), and vascular endothelial growth factor (VEGF). Activated macrophages significantly induced corneal neovascularization (CNV), which peaked on day 5, whereas the control group and normal corneas showed less CNV. The activated macrophages and corneal tissue after implantation expressed the angiogenesis-related factors, such as cyclooxygenase-2, platelet-derived growth factor, transforming growth factor beta, interleukin-1 alpha, MMP-9, and VEGF in messenger RNA (mRNA). However, mRNA expression of MMP-9 and VEGF differed significantly only in the cornea between the A-Mu group and phosphate-buffered saline group 5 days after the implantation. MMP-9 and VEGF expression of mRNA and protein was higher in the A-Mu group than that in the control group and normal corneas. Conclusions: Activated macrophages induce obvious CNV and related mechanisms, which may be correlated with MMP-9 and VEGF autocrine in activated macrophages and upregulation of MMP-9 and VEGF in corneal tissue.