Adhesive interactions between haemopoietic progenitor cells and bone marrow sinusoidal endothelium are potentially important in the homing of these cells back to the extravascular compartment of the marrow to re-establish haemopoiesis following stem cell transplantation. A simple method for the isolation and culture of human bone marrow endothelial cells is described using bone marrow aspirates obtained from patients undergoing bone marrow harvests for autologous or syngeneic bone marrow transplantation. The method is based on the selective binding of the lectin Ulex europaeus agglutinin-1 (UEA-1) to endothelial cells. Magnetic Dynabeads coupled with UEA-1 were incubated with single cell suspensions of bone marrow following red cell lysis, and bound cells were isolated with a magnet. The isolated cells demonstrated positive immunofluorescence staining for von Willebrand factor. Cells were plated onto tissue culture flasks coated with extracellular matrix derived from human umbilical vein endothelial cells in an endothelial serum-free medium together with 5% fetal calf serum for 24 h. Cells were then cultured in endothelial serum-free growth medium supplemented with 5% fetal calf serum, endothelial cell growth supplement and heparin. After 2-4 weeks in culture, two morphologically different cell populations can be identified. One has a polygonal spindle-shaped morphology with a rapid growth rate, the other a rounded morphology and a slow growth rate. Both populations have a vesiculated cytoplasm. Positive immunostaining of the cells was demonstrated with a number of endothelial cell markers including von Willebrand factor, and antibodies to ICAM-1, VCAM-1, E-selectin, CD31 and BMA120. Weibel-Palade bodies were observed by electron microscopy. Culture of these cells will allow detailed in vitro studies of adhesion mechanisms in the homing of haemopoietic progenitor cells.

This review summarizes the manner in which a variety of agents may induce fibrogenic reactions in the lung. The extent of reaction is dependent on dose, time scale of exposure, and chemical reactivity. The regime of multiple dosing with chemicals or gases with recovery periods is important in disease progression. The means by which biochemists and histopathologists assess fibrosis, the advantages and disadvantages of each of the methods as related to subjectivity, quantitation, and speed of analysis are compared. The mechanisms which control the step from fibrogenesis (a potentially reversible reaction) to fibrosis (irreversible) may be linked to the maturation of collagen, calcification, or the formation of cross-linked protein masses. Attention is given to hydroxylysine cross-links in newly formed “fibrotic” collagen but focusses on γ-glutamyl-∊-lysyl cross-links formed by calcium-dependent transglutaminases. It is suggested that these enzymes, released by replacement epithelial cells, could be responsible for the formation of stabilized protein masses in the lung, thus contributing to a progressive fibrosis.

Summary. We used flow cytometry to characterize cell adhesion molecule expression of the human haemopoietic cell lines KG1a, K562, HL-60, NALM-6 and CEM. A 51 chromium labelling assay was used to study the adhesion of these cell lines to extracellular matrix components and to bone marrow stromal and endothelial cultures. Both adhesion molecule expression and functional binding behaviour varied between cell lines. All five cell lines expressed the integrins a 4 b 1 and a 5 b 1 and all adhered to fibronectin. However, differences in intensity of expression of these integrins failed to correlate with extent of fibronectin adhesion. Inhibition experiments demonstrated that adhesion of KG1a to fibronectin was completely inhibited by divalent cation chelation and partially inhibited by RGDS peptides and chondroitinase ABC, suggesting that both a 4 b 1 and a 5 b 1 as well as CD44 were responsible for this interaction. Adhesion to bone marrow stromal and endothelial layers was superior to that to purified extracellular matrix components and was partially inhibited by divalent cation chelation. RGD peptides and anti-a 4 monoclonal antibody also partially inhibited KG1a adhesion to bone marrow endothelium.Discordance between cell adhesion molecule expression and adhesive behaviour suggest that current phenotypic descriptions remain incomplete and reinforce the need for complementary functional binding studies.

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