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Ying-Bo Shui, Benjamen Filas, Qianru Zhang, Shaili Sharma, Alyssa Panitch, David Beebe; Restoration of vitreous structure after degradation. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3152.
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Age-related vitreous degeneration leads to several sight-threatening diseases, including retinal detachment, macular hole, and pre-retinal membranes. Delaying degeneration or restoring the structure of the vitreous gel would prevent these diseases. Recently, synthetic proteoglycan mimics that bind to hyaluronic acid or collagen have been shown to increase the compressive strength of cartilage and protect other components of the extracellular matrix from proteolytic degradation, thereby replicating the functions of the cartilage proteoglycan, aggrecan. Since the vitreous is essentially “dilute cartilage,” we tested the ability of three proteoglycan mimics to restore the physical properties and structure of trypsin-treated bovine vitreous.
A core of fresh bovine vitreous is carefully removed with a trephine and injected with PBS (sham), purified trypsin, trypsin (TRYP) plus mimics , or mimics alone. The mimics were designed to bind hyaluronan (GAH), collagen type II (WYR) or both hyaluronan and collagen type II (WYR/GAH). Samples are incubated at 4 degree overnight and their viscoelastic properties measured using a rheometer. Morphological analysis is performed by deep-etch electron microscopy (DEEM).
Trypsin-treated vitreous had a significant, 50% decrease in storage modulus (stiffness) relative to untreated and PBS--sham samples. The stiffness of vitreous samples pre-treated with trypsin is completely restored by addition of each of the three proteoglycan mimics. Vitreous treated with proteoglycan mimics alone also shows a tendency toward increased storage modulus but this was not statistically significant (figure 1). In trypsin-treated vitreous DEEM showed thinner, more discontinuous fibrils, decreased “knobby” projections and increased open space. Analysis by DEEM of trypsin- and mimic-treated vitreous is in process.
Synthetic proteoglycan mimics restore the physical properties of degraded vitreous and may have clinical applications for prevention of age-related retinal damage. In vivo examination of the safety and stability the mimics in the vitreous is warranted.
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