Biomarkers of Optic Nerve Head Glial Cell Activation Following Biomechanical Insult
Glaucoma is a leading cause of irreversible blindness worldwide. Primary Open Angle Glaucoma is the most common form of the disease and can be characterized by the slow and irreversible apoptotic death of retinal ganglion cells, a unique optic nerve neuropathy resulting in loss of vision. Increased intra-ocular pressure is known to be a leading risk-factor for glaucoma, and lowering IOP is currently the only evidence based method for the clinical management of the disease. However the exact mechanism by which an elevated IOP leads to the death of the retinal ganglion cells is still poorly understood. By using previous finite element models of glaucoma to quantify the biomechanical environment within the optic nerve head we have built human primary cell culture models in an attempt to replicate aspects of early glaucomatous optic neuropathy. In these models we mimic the in vivo biomechanical environment in the lamina cribrosa by growing human optic nerve head astrocytes and lamina cribrosa cells on compliant substrates and subjecting the cells to deformation. Specifically, a global protein scan using isobaric tags for relative and absolute quantitation (iTRAQ) was performed on all the experiments to identify potential biomarkers for glaucoma. A secondary analysis using enzyme-linked immunosorbent assay (ELISA) identified extracellular proteins of interest. Over 520 proteins were identified in response to biomechnical strain from both cell types. Many of these proteins centred on TGF-, p53 and TNF, which have previously been shown to play a role in the pathogenesis of glaucoma. Proteins found in astrocytes were astrocytic phosphoprotein (PEA15), UDP-glucose dehydrogenase (UGDH), and annexin A4 (ANXA4). LC proteins were bcl-2-associated athanogene 5 (BAG5), nucleolar protein 66 (NO66) and Eukaryotic translation initiation factor 5A (eIF-5A). These proteomic results will enable a series of functional studies looking into the role select markers play in ONH glial cell activation, a process still not well understood. Candidates for this work will be prioritized based on novelty and relevance to mechanisms of cellular stress and death. We hypothesize that study of these molecular pathways will provide insight into this process, as well as improve our understanding of how glial activation contributes to the development of glaucomatous optic neuropathy.
Biomarker, Glial Cells, Astrocyte, Lamina Cribrosa Cells, Optic Nerve Head, Glaucoma, Proteomics, iTRAQ
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