Localization of laminin to retinal vessels of the rat and mouse using whole mounts.

Using a whole mount procedure in adult and neonatal mice and adult rats, we have developed an immunohistochemical method for the localization of laminin-like immunoreactivity (LLIR) to the retinal vessels. LLIR was localized to the vascular basement membrane, permitting a clear three-dimensional view of the retinal vasculature. Positive stain was seen in the inner limiting membrane, in retracted capillaries, encasing pericytes, and in a banding pattern on retinal arterioles. The major findings with the whole mount preparations were confirmed using paraffin-embedded material, with the additional observation of LLIR in the lens capsule. In whole mounts of retinas from neonatal mice, LLIR was present from the earliest stages of capillary growth, indicating that laminin is likely to be secreted by endothelial cells during retinal angiogenesis. LLIR within the retinal nerve fiber layer does not precede capillary ingrowth, so no evidence was found that laminin acts as a tracker signal for retinal angiogenesis.