To demonstrate that specific distributions of integrin-based focal mechanoreceptors exist in primate optic nerve heads, suitable for translating stress and strain into the cellular responses of glaucomatous optic neuropathy.
Normal human (N = 20) and rhesus monkey (N = 14) optic nerve heads and 32 glaucomatous optic nerve heads were processed for immunohistochemistry to determine the structural distribution of integrin subunits α1, α2, α3, α4, α5, α6, αv, β1, β2, β3, and β4. Labeling patterns in glaucoma specimens were compared with those of normal eyes.
In all specimens, cells within collagenous laminar beams and sclera failed to label with any integrin antibodies. In normal eyes, α2, α3, α6, β1, and β4 antibodies localized to astrocytes along the margins of laminar beams and within glial columns. α3, α5, α6, αv, β1, and β4 labeled vascular endothelial cells. In severely damaged glaucoma specimens, cells anterior to the compressed lamina cribrosa displayed persistent label for α2, α3, β1, and β4, whereas label for α4 increased and α6 was decreased.
Integrins α2β1, α3β1, α6β1, and α6β4 may provide attachment for astrocytes to basement membranes via laminin, providing opportunities to sense changes in stress and strain within and anterior to the lamina cribrosa. Vascular endothelial cell stress may be mediated by integrins α3β1, α6β1, and α6β4, along with α5β1 and αvβ1. In advanced damage, reduced α6 label and variable label for ββ 4 anterior to the lamina cribrosa suggests astrocyte migration. Increased label for α4 subunits suggests activation of microglia.