Abstract
Purpose: :
Myocilin (MYOC) is the protein product of a glaucoma–causing gene. In conditioned media from human trabecular meshwork (TM) cells in culture, MYOC associates with extracellular vesicles called exosomes, which function in the transport of lipid–associated ligands between cells. The goal of the present study was to determine the prevalence of MYOC–containing exosomes in human samples.
Methods: :
Aqueous humor obtained from patients undergoing cataract or glaucoma filtering surgery, aqueous humor from cadaver eyes, effluent from perfused anterior segments and conditioned media from trabecular meshwork cells were analyzed for exosome/MYOC content. Samples were centrifuged to remove cellular debris prior to centrifugation at 100,000g to pellet the exosome fraction. Proteins in exosome and soluble fractions were separated by SDS–PAGE and analyzed for MYOC content by western blotting.
Results: :
MYOC was detected in the exosome fraction of all human samples tested. MYOC–associated exosomes were found in conditioned media from TM cells (n=8), effluent from perfused anterior segments (n=2), and aqueous humor (cadaveric, n=4; pooled patient samples, n=6). Interestingly, the amount of MYOC in the exosome fraction per unit volume of sample was greater in aqueous humor (ten–fold) and effluent (three–fold) compared to conditioned medium from TM cells.
Conclusions: :
Exosomes are present in human samples and due to their association with MYOC likely participate in the regulation of aqueous humor drainage through the conventional pathway.
Keywords: aqueous • trabecular meshwork • anterior segment