Fig. 2

Tetrahydrobiopterin (BH4) deficiency is associated with retinal microvascular degeneration. a Representative images of whole-mounted retinas labeled with TRITC-conjugated lectin endothelial cell marker Bandeiraea simplicifolia showing microvascular degeneration in the superficial and deep retinal vascular complexes particularly noted in the central retina from hph-1 animals at P22. Scale bar = 400 μm. b Representative confocal images of retinal cryosections labeled with TRITC-conjugated lectin (red) and DAPI (blue) showing the anatomic localization of the vascular complexes in the retinas from hph-1 and WT mice. The vascular networks in the retina were grouped into superficial and deep vascular complexes (SVC and DVC) according to the current nomenclature [62]. NFL nerve fiber layer, GCL ganglion cell layer, IPL inner plexiform layer, OPL outer plexiform layer, and ONL outer nuclear layer. Scale bar = 50 μm. c The quantification of the vascular density in both superficial and deep retinal vascular complexes was significantly minor in hph-1 mice compared to the WT control. Results showed in the histograms are expressed as means ± SEM of n = 3–4 retinas for each group. **p < 0.005, ****p < 0.0001 compared to the control