Monocyte activation in patients with age-related macular degeneration - A biomarker of risk for choroidal neovascularization?

Objective: To evaluate the activation state of macrophage function in patients with age-related macular degeneration (AMD) by quantifying the production of the proinflammatory and angiogenic factor tumor necrosis factor alpha (TNF-alpha) and by correlating its expression with dry and wet AMD. Methods: Circulating monocytes were obtained from the blood of patients with AMD or age-matched control subjects by gradient centrifugation. The monocytes were then analyzed for either TNF-alpha release from cultured macrophages in response to retinal pigment epithelium-derived blebs and cytokines or TNF-alpha. messenger RNA content by reverse transcriptase-polymerase chain reaction. Results: In human monocytes obtained from controls and AMD patients, TNF-alpha was expressed by freshly isolated monocytes and produced by macrophages in culture after stimulation with retinal pigment epithelium-derived blebs. However, wide variability in TNF-alpha expression was observed among different patients. Patients with monocytes that expressed the greatest amount of TNF-alpha demonstrated higher prevalence of choroidal neovascularization. Conclusions: Both controls and AMD patients vary in the activation state (defined as TNF-alpha expression) of circulating monocytes. Partially active monocytes, defined as high TNF-alpha expression, may be a biomarker to identify patients at risk for formation of choroidal neovascularization. Clinical Relevance: Early diagnostic testing may prove useful to detect those patients who will progress to the more severe complications of the disease.