Production of granulocyte-macrophage colony-stimulating factor by primary cultures of unstimulated rat microvascular endothelial cells

Small vessel (microvascular) endothelial cells are in close contact with hematopoietic progenitor cells in the bone marrow and therefore may have an important role in hematopoiesis. Although other studies have shown that endothelial cells produce various colony-stimulating factors (CSFs), these studies examined large vessel endothelial cells, which are different in many respects from microvascular endothelial cells and which do not contact cells in the bone marrow. We show in this study that primary cultures of unstimulated rat fat capillary endothelial cells grown in serum-free medium produce a substantial amount of granulocyte-macrophage CSF (GM-CSF). The medium conditioned by these cells stimulated proliferation of two different lines of GM- CSF-responsive cells--PT-18 mast cells and FDC-P1 cells--and supported the growth of cells of the granulocyte and macrophage lines in cultures of rat bone marrow cells. The factor responsible for this activity had physical properties consistent with those of GM-CSF, namely, a similar apparent mol wt by gel filtration, resistance to repeated freeze-thaws, resistance to boiling for ten minutes but not for 30 minutes, and resistance to heating to 56 degrees C for one hour. The factor causing target cell stimulation was not B cell-stimulating factor-1 (BSF-1, or IL 4), since it failed to stimulate a BSF-1-responsive cell line HT2- JH, and target cells (PT-18) did not respond appreciably to recombinant BSF-1. Northern blot analysis of mRNA from rat fat capillary endothelial cells showed high levels of expression of GM-CSF, confirming that this factor is produced by microvascular endothelial cells. This is the first report of CSF production by unstimulated microvascular endothelial cells, demonstrating that these ubiquitous cells are capable of producing sizable amounts of at least one growth factor for hematopoietic progenitor cells.     

Irradiation induces release of von Willebrand protein from endothelial cells in culture

Human umbilical vein endothelial cells in tissue culture were irradiated with doses between 0 and 40 Gy, and the released von Willebrand (vW) protein and that which remained associated with the cells was quantitated. Doses of 20 Gy and higher produced a statistically significant increase in amount of vW protein secreted. This release was present whether the cells were labeled continuously throughout the experiment or just prelabeled before irradiation. An increase in fibronectin secretion was not observed. The release response to radiation was slow, reaching significance close to 24 hours after irradiation. The release of vW protein was not due to cell lysis, because the secreted vW protein contained very little of the large 260- kilodalton vW precursor subunit present in cell lysates and the cells appeared intact by immunofluorescence staining.     

High-dose therapy and autologous peripheral blood stem cell transplantation for patients with lymphoma

Forty patients with refractory Hodgkin's disease (24 patients) or non- Hodgkin's lymphoma (16 patients) who were considered for high-dose therapy but not for autologous bone marrow transplantation (ABMT) due to BM metastases, previous pelvic irradiation, a history of marrow involvement by tumor or hypocellular marrow in conventional harvest sites received high-dose therapy and autologous peripheral blood (PB) hematopoietic stem cell transplantation. Disappearance of circulating neutrophils and development of RBC and platelet transfusion-dependence was followed, in the evaluable patients, by reappearance of 0.5 x 10(9)/L circulating granulocytes and sufficient platelets to obviate the need for platelet transfusions at a median of 25 days after transplantation. Twenty-three patients experienced a clinical complete remission (CR). The projected 2-year event-free survival was 24% for all 40 patients and 49% for the non-Hodgkin's lymphoma patients. The projected 18-month event-free survival for the Hodgkin's disease patients was 15%. PB stem cell transplantation provided an opportunity to administer high-dose salvage therapy to patients with refractory lymphoma who otherwise were not candidates for such therapy. For some of those patients, the high-dose therapy produced prolonged survival, free of tumor progression.     

Autologous peripheral hematopoietic stem cell transplantation restores hematopoietic function following marrow ablative therapy

From ten patients with advanced malignant disease involving the bone marrow, autologous hematopoietic stem cells were collected from the peripheral blood during eight four-hour pheresis procedures and cryopreserved. No manipulations to increase the number of stem cells circulating in the blood were used during the collections. Following marrow ablative chemotherapy or chemoradiotherapy, the autologous cells were thawed and infused intravenously (IV). WBCs reappeared in the circulation at a median of eight days (range seven to 11 days) after stem cell infusion. Two patients died early, whereas the other eight reached normal numbers of circulating granulocytes that have persisted for up to greater than 20 months. These eight patients became independent of RBC transfusions (hemoglobin concentration greater than 10 g/dL) at a median of 27 days (range 11 to 58 days) after transplantation. One patient received platelet transfusions for counts less than 50 x 109)/L, one patient developed a clinical picture of idiopathic thrombocytopenic purpura, and six patients maintained a platelet count greater than 20 x 10(9)/L at a median of 23 days (range 14 to 25 days) following stem cell infusion. This technique allows patients ineligible for autologous bone marrow transplantation due to unacceptable anesthetic risks, prior pelvic irradiation, or bone marrow metastases to receive marrow ablative therapy.     

Blood cell dynamics in P-selectin-deficient mice

P-selectin is expressed on the surfaces of activated platelets and endothelium where it mediates binding to leukocytes. P-selectin- deficient mice were shown to exhibit peripheral neutrophilia (Mayadas et al: Cell 74:541, 1993). We now show that this is not caused by changes in bone marrow precursors nor by a lack of neutrophil margination. Both P-selectin-positive and -negative animals displayed similar increases in peripheral blood neutrophil numbers after injection of epinephrine. However, clearance of 51Chromium-labeled neutrophils is delayed in mice deficient for P-selectin, indicating that the neutrophilia is at least in part the result of delayed removal. We detected no obvious alterations in lymphocyte differentiation, distribution, or adhesion to high endothelial venules in peripheral lymph nodes. Through intravital microscopy, we examined the impact of P-selectin deficiency on leukocyte/endothelial interaction beyond the initial stages of inflammation. Four hours after the administration of an inflammatory irritant, leukocyte rolling was observed even in the absence of P-selectin. There were significantly fewer rolling cells relative to wild-type mice, and their velocity was reduced. Moreover, in the peritonitis model, the number of peritoneal macrophages in wild-type mice increased threefold at 48 hours, whereas the macrophages in the mutant mice remained near baseline levels. Thus, whereas P-selectin is known to be involved in early stages of an inflammatory response, our results indicate that it is additionally responsible for leukocyte rolling and macrophage recruitment in more prolonged tissue injury.     

Dysregulated bcl-2 expression inhibits apoptosis but not differentiation of retinoic acid-induced HL-60 granulocytes

The bcl-2-proto-oncogene appears to contribute to the development of certain malignancies by inhibiting programmed cell death (apoptosis). Mature granulocytes show a markedly limited life span and rapidly undergo apoptosis. To further define the relationship between apoptosis and granulocyte differentiation, we used retroviral vector-mediated gene transduction to introduce the normal bcl-2 gene into the HL-60 myeloid leukemia cell line and determined the response of these bcl-2- transduced HL-60 cells to the induction of granulocyte differentiation by retinoic acid (RA). Although the bcl-2-transduced HL-60 cells showed the same differentiative response to RA as did the parental HL-60 cells, the life span of the RA-induced, bcl-2-transduced HL-60 granulocytes was markedly prolonged compared with that of the RA- induced parental HL-60 granulocytes. DNA fragmentation studies indicate that this prolonged life span resulted from diminished apoptosis in the bcl-2-transduced cells. These studies indicate that bcl-2 is involved in regulating apoptosis in maturing granulocytes. Because bcl-2 over- expression did not interfere with RA-induced granulocyte differentiation, it appears that granulocyte differentiation and apoptosis are under distinct and separate regulatory controls.     

Lymphocyte predominance Hodgkin's disease: lineage and clonality determination using a single-cell assay

Lymphocyte predominance Hodgkin's disease (LPHD) is a clinically indolent condition. Although there is evidence that the putative neoplastic cell in this disease, the "L&H" cell, is of B-cell lineage, there is conflicting data concerning the clonality of these cells. Our study was aimed at clarifying the issue of lineage and clonality of the L&H cells of LPHD using a single-cell assay. Four cases of LPHD were studied. To circumvent the difficulties of obtaining fresh tissue and to be able to study representative cases, a new method was developed to obtain single-cell suspensions of L&H cells from archival formalin- fixed paraffin-embedded tissue. Single L&H cells were identified by morphology and immunostaining for epithelial membrane antigen, isolated using a micropipette, and subjected to polymerase chain reaction (PCR) amplification of the complematarity determining region 3 (CDR3) of the Ig heavy chain (IgH) gene, which is B-cell clone-specific. The PCR products were size-fractionated by polyacrylamide gel electrophoresis and representative products were directly sequenced. Single T cells and small B cells were also isolated from the tissues and used as negative and positive controls, respectively. In all four cases of LPHD, the IgH CDR3 of single L&H cells could be amplified. Within each case, the IgH CDR3 of single L&H cells was found to be of different length or of different sequence. Therefore, our results provide strong evidence for the B-cell origin of the L&H cells and the polyclonal nature of LPHD.     

Biochemical, immunological, and in vivo functional characterization of B-domain-deleted factor VIII

Coagulation factor VIII (FVIII) is a cofactor in the intrinsic pathway of blood coagulation for which deficiency results in the bleeding disorder hemophilia A. FVIII contains a domain structure of A1-A2-B-A3- C1-C2 of which the B domain is dispensable for procoagulant activity in vitro. In this report, we compare the properties of B-domain-deleted FVIII (residues 760 through 1639, designated LA-VIII) to wildtype recombinant FVIII. In transfected Chinese hamster ovary (CHO) cells, LA- VIII was expressed at a 10- to 20-fold greater level compared with wildtype FVIII. The specific activity of purified LA-VIII was indistinguishable from wild-type recombinant FVIII and both exhibited similar thrombin activation coefficients. Wildtype recombinant-derived FVIII and LA-VIII also displayed similar timecourses of thrombin activation and heavy chain cleavage. However, compared with wildtype recombinant-derived FVIII, the light chain of LA-VIII was cleaved fivefold more rapidly by thrombin. Addition of purified von Willebrand factor (vWF) did not alter the kinetics of thrombin cleavage or activation of either wildtype recombinant-derived FVIII or LA-VIII. The immunogenicity of LA-VIII was compared with wildtype FVIII in a novel model of neonatal tolerance induction in mice. The results did not detect any immunologic differences between wildtype FVIII and LA-VIII, suggesting that LA-VIII does not contain significant new epitopes that are absent in wildtype FVIII. LA-VIII was tolerated well on infusion into FVIII-deficient dogs and was able to correct the cuticle bleeding time similar to wildtype recombinant factor VIII. In vivo, LA-VIII was bound to canine vWF and exhibited a half-life similar to wildtype recombinant FVIII. These studies support that B-domain-deleted FVIII may be efficacious in treatment of hemophilia A in humans.