Vascular localization of heparan sulfate proteoglycans in retinas of patients with diabetes mellitus and in VEGF-induced retinopathy using domain-specific antibodies

Purpose. The Steno hypothesis (Deckert et al.)(1) states that in diabetes m ellitus (DM), changes in vascular heparan sulfate proteoglycan (HSPG) expre ssion are involved in systemic endothelial dysfunction and increased capill ary permeability. In diabetes-induced glomerular capillary leakage, loss of HSPG and its side chains has been documented. This study aimed to investig ate whether microvascular leakage in diabetic retinopathy (DR) is also asso ciated with altered expression of HSPG in retinal microvessels. Methods. Serial cryosections of post-mortem eyes of 22 subjects with DM and 7 controls were stained with antibodies against the core proteins of the b asement membrane HSPGs agrin (Abs B131 and JM72) and perlecan (Ab 1948), an d four antibodies against heparan sulfate side chains (HS) (Abs JM403, HepS S1, JM13, 3G10). Moreover, we investigated Cynomolgus monkey eyes injected with vascular endothelial growth factor (VEGF)-A, as a model of retinal mic rovascular leakage. The endothelial antigen PAL-E was used to detect microv ascular leakage. Results. In the retina of all controls and DM cases, agrin and perlecan cor e proteins and HS as recognized by JM403 and 3G10 were expressed in the wal ls of microvessels. Staining for JM13 was variable between cases. but unrel ated to microvascular leakage as determined by PAL-E. Staining for HepSS1 w as absent in all human retinal microvessels. In monkey retinas, HSPG staini ng was identical to that in human retinal tissues, except for the staining for HepSS1, which was found absent in control monkey eyes but which was pos itive in VEGF-injected eyes. Conclusion. Increased microvascular permeability in human DR is not associa ted with changes in expression of the HSPGs studied whereas high amounts of VEGF may induce increased expression of the HS side chain epitope recogniz ed by HepSS1. These results suggest that the mechanism underlying retinal l eakage is different from diabetic glomerular capillary leakage.