Increased vitronectin production by complement-stimulated human retinal pigment epithelial cells.

PURPOSE

A variation in the complement factor H gene was associated with an enhanced risk to develop especially early age-related macular degeneration. Drusen and basal laminar deposits are hallmarks of this AMD manifestation that contain vitronectin as a major component. In this study, the correlation between complement stimulation and vitronectin production of retinal pigment epithelial (RPE) cells was investigated.

METHODS

ARPE-19 cells, a permanent cell line of human RPE cells, were supplemented with and without human complement competent serum in medium with and without heat inactivated fetal calf serum. The cells were examined in situ for their vitronectin production as an effective inhibitor of alternatively activated complement by immunohistochemistry. Semi-quantitative RT-PCR and Western blots were performed to analyze vitronectin mRNA and protein.

RESULTS

A strong immunohistochemical staining for vitronectin was observed after complement supplementation. The enhanced production of this complement inactivator by ARPE-19 cells was confirmed by Western blot, whereas the expression analysis revealed unaltered mRNA amounts.

CONCLUSIONS

A stimulation of RPE cells with complement resulted in an upregulated production of vitronectin. This may support the concept of a protective mechanism, since vitronectin is the major inhibitor of complement activated by the alternative pathway. On the other hand, this increased vitronectin production after complement stimulation may contribute to focal or diffuse deposits in Bruch's membrane, as observed in early AMD.