α2-Macroglobulin levels in normal human and keratoconus corneas

Purpose. To compare the levels of α2-macroglobulin, one of the major proteinase inhibitors, in corneas with keratoconus to those in normal human corneas and corneas with other diseases. Methods. An immunoperoxidase technique was used to visualize the presence of α2-macroglobulin in the corneas. Western blot analysis was performed, and the levels of this inhibitor in extracts of keratoconus and normal human corneas were subsequently analyzed by a dot blot assay. Results. α2-Macroglobulin was demonstrated immunohistochemically in the epithelium, stroma, and endothelium of all corneal sections. Compared with normal human control specimens, the staining intensity in the epithelium of keratoconus corneas was markedly reduced. The majority of scarred and other diseased corneas exhibited normal staining intensity for α2-macroglobulin. Dot blot assays showed that the α2-macroglobulin levels in the epithelial and stromal extracts of keratoconus corneas were lower than those found in normal human control counterparts. Conclusion. Keratoconus corneas contained a reduced level of α2-macroglobulin. This result lends further support to the hypothesis that degradation processes may be aberrant in keratoconus.