HAS2 and Hyperglycemia: In addition, a recent study on rat retinal microvascular endothelial cells (rrmec) showed that hyperglycemia in rrmec leads to significantly elevated mRNA levels of GAG biosynthetic enzymes (including extl -1,2,3, ext -1,2, chsy -1,3, and has2,3), and that these elevations may be a compensatory response to overall glycocalyx loss45.