Erythroid failure in Diamond-Blackfan anemia is characterized by apoptosis.

Programmed cell death, also known as apoptosis, is frequently initiated when cells are deprived of specific trophic factors. To investigate if accelerated apoptosis contributes to the pathogenesis of Diamond-Blackfan anemia (DBA), a rare pure red blood cell aplasia of childhood, we studied the effect of erythropoietin (epo) deprivation on erythroid progenitors and precursors from the bone marrow of DBA patients as compared with hematologically normal controls. Apoptosis in response to epo deprivation was evaluated by enumeration of colony-forming unit-erythroid (CFU-E)- and burst-forming unit-erythroid (BFU-E)-derived colonies in plasma clot semisolid culture and by the identification of typical DNA oligosomes by gel electrophoresis from marrow mononuclear cells in liquid culture.

Expression of intercellular adhesion molecule-1 (CD54) on hematopoietic progenitors.

The distribution of intercellular adhesion molecule-1 (ICAM-1), a ligand for lymphocyte function antigen-1, on hematopoietic tissue was determined using the anti-ICAM-1 monoclonal antibody CL203.4 with flow cytometry and short-term semi-solid hematopoietic progenitor cultures. After timed incubation in media with fetal bovine serum, 29% of erythroid burst-forming units (BFU-E), 24% of erythroid colony-forming units (CFU-E), and 52% of granulocyte-macrophage colony-forming units (CFU-GM) bone marrow progenitors expressed ICAM-1.

Migration of neutrophils across monolayers of cultured microvascular endothelial cells. An in vitro model of leucocyte extravasation.

Monolayers of bovine microvascular endothelial cells (BMECs) grown on connective tissue derived from human amniotic membrane were used to examine the transendothelial migration of human neutrophils in vitro. Neutrophils placed above these cultures migrated in response to a chemotactic gradient generated by placing 10(-7) M-formyl-methionyl-leucyl-phenyl-alanine (fMLP) below the cultures. Under these conditions, an average of 29 +/- 12% of the total population of neutrophils migrated beneath the endothelium after 1 or 2 h of incubation.

Cultured endothelial cell monolayers that restrict the transendothelial passage of macromolecules and electrical current.

Bovine microvascular endothelial cells (BMECs) proliferated to confluence on the stromal surface of human amniotic membrane that had been denuded of its natural epithelium. The resulting cultures had the following characteristics: (a) The endothelial cells formed a thin, continuous monolayer and, like their in vivo counterparts, contained basal adhesion plaques and large numbers of cytoplasmic vesicles and 10-nm filaments. In addition, the endothelial cells elaborated a basement membrane-like structure.