Expression of stabilin-2, a novel fasciclin-like hyaluronan receptor protein, in murine sinusoidal endothelia, avascular tissues, and at solid/liquid interfaces

Stabilin-2, the hepatic hyaluronan receptor, has recently been cloned by us. Together with stabilin-1, stabilin-2 constitutes a novel family of fasciclin-like hyaluronan receptor homologues. Here, we analyzed expression of stabilin-2 (mStab-2) in a broad array of C57BL/6 mouse organs and tissues. While northern blot analysis showed positive expression of mStab-2 mRNA confined to liver and spleen, immunohistochemistry demonstrated mStab-2 protein expression in the endothelial sinuses of liver, lymph nodes, spleen, and bone marrow, and in specialized structures of eye, heart, brain, and kidney. Expression of mStab-2 was detected in corneal and lens epithelium, in mesenchymal cells of the heart valves, in the ependymal cells lining the ventricles in the brain, and in the prismatic epithelial cells covering the renal papillae. In pathological conditions, such as tumor growth or wound healing processes, mStab-2 was not expressed in the newly formed vasculature or other tissue components. Based on these results, we suggest that mStab-2 might be involved in the clearance of hyaluronan from the lymph or the blood circulation via the network of endothelial sinuses. At the other mStab-2-positive tissues sites that are either avascular and/or demarcate a solid/liquid interface, mStab-2 may serve to maintain tissue integrity by supporting extracellular matrix turnover or it may contribute to maintaining fluidity of bodily liquids by resorption of hyaluronan.