Transient expression of laminin α1 chain in regenerating murine liver:: Restricted localization of laminin chains and nidogen-1

Most interstitia between epithelial and endothelial cells contain basal laminae (BLs), as defined by electron microscopy. However, in liver, the sinusoidal interstitium (called space of Disse) between hepatocytes and sinusoidal endothelial cells (SECs) lacks BLs. Because laminins are major components of BLs throughout the body, whether laminins exist in sinusoids has been a controversial issue. Despite recent advances, the distribution and expression of laminin chains have not been well defined in mammalian liver. Here, using a panel of antibodies, we examined laminins in normal and regenerating mouse livers. Of alpha chains, alpha 5 was widely observed in all BLs except for sinusoids, while the other alpha chains were variously expressed in Glisson's sheath and central veins. Laminin gamma 1 was also distributed to all BLs except for sirmsoids. Although the beta 2 chain was observed in all BLs and sinusoids, the expression of beta 1 chain was restricted to Glisson's sheath. Detailed analysis of regenerating liver revealed that alpha 1 and gamma 1 chains appeared in sinusoids and were produced by stellate cells. The staining of alpha 1 and gamma 1 chains reached its maximum intensity at 6 days after two-thirds partial hepatectomy (PHx). Moreover, in vitro studies showed that alpha 1-containing laminin promoted spreading of sinusoidal endothelial cells (SECs) isolated from normal liver, but not other hepatic cells. In addition, SECs isolated from regenerating liver elongated pseudopodia on alpha 1-containing larninin more so than did cells from normal liver. The transient expression of laminin alpha 1 may promote formation of sinusoids after PHx. (c) 2005 Elsevier Inc. All rights reserved.