Expression of Cell Adhesion Molecules at the Collapse and Recovery of Haematopoiesis in Bone Marrow of Mouse

Abstract

After bone marrow transplantation (BMT) and lethal irradiation, vascular endothelial cells play an important role in the homing of haematopoietic cells and recovery of haematopoiesis. We investigated the expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1), vascular cell adhesion molecule-1 (VCAM-1) and fibronectin in the endothelial cells of bone marrow in a collapsed state after lethal irradiation and in a recovery state after BMT in mice. After lethal irradiation, the expression of MAdCAM-1, VCAM-1 and fibronectin increased on the luminal surface of endothelial cells. In the recovery state, the expression of MAdCAM-1 and VCAM-1 was increased from 2 to 4 days after BMT, but fibronectin levels remained constant, except for a temporary increase at 4 days after BMT. The number of homing cells, however, was markedly decreased in parallel with the reduction in the haematopoietic compartment at 2 and 4 days after lethal irradiation. Next, to analyse the influence of fibronectin expression after BMT on homing activity, we performed double BMT experiment. The number of homing cells in double BMT experiment maintained high level from 2 h to 2 days after secondary BMT. Our data suggest that homing of bone marrow cells is activated until fibronectin-mediated endothelial cell repair and that transplanted haematopoietic stem/progenitor cells inhibit fibronectin expression for endothelial cell repair until the homing is completed. Therefore, the homing of haematopoietic cells in bone marrow depends on the condition of the bone marrow endothelial cells, as well as the cell adhesion molecules.