Expression of the 67 kDa laminin receptor (67LR) during retinal development: Correlations with angiogenesis

Interaction of vascular cells with the laminin component of basement membra nes is important for normal cell function. Likewise. abnormal interactions may have a critical role in vascular pathology. It has been previously demo nstrated that the 67 kDa laminin receptor (67LR) is expressed at high level s during proliferative retinopathy in a mouse model and in the current stud y we have examined 67LR in the neonatal mouse to determine if this receptor plays a role in aspects of developmental angiogenesis in the developing mu rine retina. Groups of C57/BL6 mice were killed at postnatal day P1, P3, P5 , P7, P9 and P11 to assess the retinal vasculature. A number of mice were p erfused with FITC-dextran and the eyes removed, fixed in 4 % paraformaldehy de (PFA) and flat-mounted for confocal scanning laser microscopy. The eyes from the remaining mice were either placed in 4 % PFA and embedded in paraf fin-wax, or had the neural retina dissected off and total RNA or protein ex tracted. Immunofluorescence, in situ hybridization, quantitative reverse tr anscriptase polymerase chain reaction and Western blotting analysis were em ployed to locate and determine expression levels of 67LR. Both 67LR mRNA an d protein expression showed a characteristic bi-phasic expression pattern w hich correlated with key stages of retinal vascular development in the muri ne retina. 67LR showed high expression levels at P1 (P < 0.05) (correlating with superficial vascular plexus formation) and at P7 (P < 0.05) (correlat ing with deep vascular plexus formation). Conversely, 67LR expression was d ecreased when active angiogenic activity was lowest. Significantly, optical sectioning of retinal flat-mounts revealed high levels of 67LR expression in developing segments of both superficial and deep capillary plexi, a patt ern which co-localized strongly with laminin. 67LR is regulated during post -natal development of the retinal vasculature. High levels of 67LR during t he two well-defined phases of retinal capillary plexus formation suggests t hat this receptor may play an important role in retinal angiogenesis. (C) 2 001 Academic Press.