Novel structure of hepatic extracellular matrices containing arylsulfatase A.

Arylsulfatase A (ArsA) has been regarded as a lysosomal enzyme involved in the degradation of sulfolipids. We previously reported the colocalization of non-enzymatic ArsA with heparan sulfate proteoglycan on cell surfaces in the mouse liver using tissues processed with phosphate-buffered saline containing Ca2+ and Mg2+. In vitro analysis also revealed the tight binding of ArsA to heparin. These results suggest that ArsA functions as a component of the extracellular matrix (ECM). To characterize ArsA as a component of ECMs, we extended our comparison to the distribution patterns of ArsA and the major hepatic ECM components (types I, III, IV and V collagen, fibronectin, and laminin) in the mouse liver at the ultrastructural level under the same conditions that allow the detection of ArsA. Here, we show that ArsA is distributed not only on the cell surfaces of endothelial cells and hepatocytes, but also on the collagen fibrils in the space of Disse. ArsA is additionally colocalized with these major hepatic ECM components on both the luminal and abluminal sides of sinusoidal endothelial cells as well as in the space of Disse. These findings reveal a novel structure of hepatic ECMs containing ArsA.