Fig. 1

Expression of MMP-2 in the healthy adult mouse retina. a Immunostaining with ab1 revealed a macroglial staining pattern for MMP-2 on retinal sections. b A double staining for glutamine synthetase (GS) disclosed strong MMP-2 expression in the Müller glia end feet (arrow 1), in their somata (arrow 3) and radial processes spanning the inner retina (arrow 2), as well as a more faint expression in the radial processes spanning the outer retina (arrow 4) and in the Müller glia villi (arrow 5). c Immunostaining with ab2 was predominantly observed in Müller glia end feet (arrow 1), in their radial processes in the inner retinal layers (arrow 2), and in synaptic sheets in the OPL (arrow 6). Scale bars, 20 μm. d-e Immunostaining with ab1 on retinal flatmounts revealed that MMP-2 is not expressed by astrocytes, as staining patterns of MMP-2 and GFAP (for astrocytes) were clearly divergent. Rather, MMP-2 expression at the inner retinal surface was seen in a punctuate organization, suggestive of Müller glia end feet. Scale bars, 50 μm. f Western blotting on naive retinal tissue lysates (R) with ab1 and ab2 showed that both antibodies recognize the bands corresponding to pro-MMP-2 (72 kDa) and active MMP-2 (63 kDa), as well as an active MMP-2 fragment (42 kDa) and a 110 kDa band. The 36 kDa band visualized by ab2 might represent an autocatalytic cleavage fragment of MMP-2. Recombinant human MMP-2 (rh) was loaded as a positive control. g Gelatin zymography on naive mouse retinal tissue lysates (R) revealed pro-MMP-2 (72 kDa) and pro-MMP-9 (102 kDa), yet no active gelatinases. Culture medium from HT1080 human firbosarcoma cells (c), containing pro-MMP-9 (92 kDa), active MMP-9 (82 kDa), pro-MMP-2 (72 kDa) and active MMP-2 (63 kDa), was loaded as a positive control.