Abstract
Purpose: :
The molecular weight of hyaluronic acid (HA) is known to vary as a function of development, maturation and aging. Although the concentration of HA is known to decrease in primary open-angle glaucoma (POAG), the molecular weight distribution profile of HA is not known. The purpose of this study is to determine the concentration and molecular weight profile of HA in POAG patients with well-defined clinical status.
Methods: :
Aqueous humor samples of pooled moderate-severity POAG (n=6) and age-matched control subjects (n=6) were analyzed for HA using highly sensitive mini-slab 15% Tris/borate/EDTA gels with pulsed electrophoresis, and stained with 0.05% Stains-All (3,3’-Diethyl-9-methyl-4,5,4’,5’-dibenzothiacarbocyanine; 1-Ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl]naphtho[1,2-d]thiazolium bromide). Bromophenol blue (0.005% in Tris/borate/EDTA buffer containing 0.3 M sucrose) was used as a tracking dye. A standard curve of HA concentration (y=1934.5x, R=0.9911) was generated using known concentrations of HA (Sigma), and a standard curve of molecular size vs. distance migrated (y=14187*x^-1.0861, R=0.9884) was generated using a low molecular weight HA ladder (492, 310, 213, 110 and 30 kDa respectively). Using these standard curves, aqueous samples were analyzed with MetaMorph® Version 7.5.6.0 (MDS Analytic Technologies) image analysis software to determine the amount and molecular size of aqueous HA.
Results: :
The HA concentration in pooled POAG aqueous was 0.54 ng/ul and the average molecular weight was 159 kDa. In contrast, the HA concentration in normal aqueous was considerably higher at 3.18 ng/ul and the average molecular weight was 194 kDa. The distribution profile of HA molecular weight in POAG samples showed the majority of HA was less than 110 kDa (60%) whereas normal aqueous had less low molecular weight HA.
Conclusions: :
POAG aqueous has less HA, smaller average molecular weight HA and more low molecular weight HA than normal aqueous. Since low molecular weight HA is known to be pro-inflammatory, the higher amount of low molecular weight HA in POAG aqueous may influence cellular and extracellular matrix activity of the POAG TM leading towards reduced aqueous outflow facility.
Keywords: aqueous • glycoconjugates/glycoproteins • trabecular meshwork