Abstract
Purpose::
Bruch’s membrane is a complex extracellular matrix (ECM) structure consisting of basement membrane proteins which becomes abnormal in several diseases, including age-related macular degeneration (AMD). Disturbed interaction of RPE cells with their ECM and age-related regression of the ECM adhesion molecules could play a role in this process. The exact molecular composition of basement membrane proteins that form Bruch’s membrane was not investigated till now.
Methods::
Laser photocoagulation-induced rupture of the Bruch’s membrane in C57BL/6J mice was used as an experimental model of AMD. We used a panel of antibodies against the basement membrane proteins (laminins, nidogens, collagen IV and perlecan) to determine their expression in Bruch’s membrane and in other ocular basement membranes in normal and injured choroid/retina.
Results::
Laminin-1 was expressed in Bruch’s membrane and in all basement membranes. In contrast, immunoreactivity for laminins containing alpha-4 chains (Laminin-8,-9,-14) and laminins containing alpha-5 chains (Laminin-10,-11,-15) was located predominantly to the vascular basement membranes. After laser-induced rupture of the Bruch’s membrane, both laminin families containing alpha-4 and alpha-5 chains, as well as, laminin-1 were expressed in the vascular basement membranes of newly formed pathological vessels within the laser burns. Laminin-5 staining was observed only in the cornea (Bowmann’s membrane) but not in choroid/retina. Nidogen-1 and -2 were expressed in Bruch’s membrane and in the vascular basement membranes of the blood vessels, including newly formed pathological vessels within the laser burns. Immunoreactivity to perlecan an collagen-IV was also located to the Bruch’s membrane and other basement membranes including vascular walls.
Conclusions::
This data give evidence about the molecular composition of the ocular basement membranes and especially Bruch’s membrane. The blood vessels (old and also newly formed) can be readily identified by immunohistochemical staining with almost all tested basement membrane proteins.The staining was comparable to this with the classical endothelial cell marker vWF and CD-31. This provide additionally a useful tool for the visualization of ocular blood vessels on paraffin sections.
Keywords: age-related macular degeneration • Bruch's membrane • choroid: neovascularization