Abstract
Purpose :
The presence of a physical barrier to extracellular space molecular diffusion in the lens has been confirmed in multiple species including rat, bovine and human. This extracellular diffusion barrier has been proposed to restrict the movement of solutes into the lens and act to direct nutrients into the lens core via the sutures at both poles. The purpose of this study is to characterize the molecular components that could contribute to the formation of this barrier.
Methods :
Three distinct regions of the lens cortex of bovine lenses were captured by laser capture microdissection guided by dye penetration. Mass spectrometry-based quantitative proteomic analysis was performed to determine protein changes. Imaging mass spectrometry was also employed to visualized protein distribution differences in the barrier region. Gene ontology enrichment analysis and protein-protein interaction network analysis were also carried out.
Results :
Dye penetration showed that lens fiber cells shrink the extracellular spaces of the broad sides of fiber cells first followed by closing the extracellular spaces at the short sides at normalized lens distance (r/a) of 0.9 in the bovine lens. Accompanying the closing of the extracellular spaces and fiber cell morphologic changes, dramatic proteomic changes were detected. Label free quantification, gene ontology enrichment analysis, and protein-protein interaction network analysis revealed potential proteins that could be involved in formation of the extracellular diffusion barrier include some junction proteins and cytoskeletal proteins. Imaging mass spectrometry also revealed a sharp intermediate filament transition from vimentin to lens-specific beaded filament proteins at this normalized lens distance. AQP0 and its interacting partners, ERM proteins, were among a few proteins that were upregulated in the barrier regions suggesting a particularly important role of the major lens membrane protein AQP0 in controlling the narrowing of the extracellular spaces in lens fiber cells.
Conclusions :
The formation of lens extracellular diffusion barrier is accompanied by significant membrane and cytoskeletal protein remodeling.
This is a 2021 ARVO Annual Meeting abstract.