Andrea Wilke

G-CSF treatment after myocardial infarction: impact on bone marrow-derived vs cardiac progenitor cells.

OBJECTIVE Besides its classical function in the field of autologous and allogenic stem cell transplantation, granulocyte colony-stimulating factor (G-CSF) was shown to have protective effects after myocardial infarction (MI) by mobilization of bone marrow-derived progenitor cells (BMCs) and in addition by activation of multiple signaling pathways. In the present study, we focused on the impact of G-CSF on migration of BMCs and the impact on resident cardiac cells after MI. MATERIALS AND METHODS Mice (C57BL/6J) were sublethally irradiated, and BM from green fluorescent protein (GFP)-transgenic mice was transplanted. Coronary artery ligation was performed 10 weeks later. G-CSF (100 microg/kg) was daily injected for 6 days. Subpopulations of enhanced GFP(+) cells in peripheral blood, bone marrow, and heart were characterized by flow cytometry. Growth factor expression in the heart was analyzed by quantitative real-time polymerase chain reaction. Perfusion was investigated in vivo by gated single photon emission computed tomography (SPECT). RESULTS G-CSF-treated animals revealed a reduced migration of c-kit(+) and CXCR-4(+) BMCs associated with decreased expression levels of the corresponding growth factors, namely stem cell factor and stromal-derived factor-1 alpha in ischemic myocardium. In contrast, the number of resident cardiac Sca-1(+) cells was significantly increased. However, SPECT-perfusion showed no differences in infarct size between G-CSF-treated and control animals 6 days after MI. CONCLUSION Our study shows that G-CSF treatment after MI reduces migration capacity of BMCs into ischemic tissue, but increases the number of resident cardiac cells. To optimize homing capacity a combination of G-CSF with other agents may optimize cytokine therapy after MI.

Expression of Heme Oxygenase-1 Protects Endothelial Cells from Irradiation-Induced Apoptosis

A common side effect of therapeutic use of ionizing irradiation is endothelial cell damage resulting in a variety of clinical complications. Thus, preservation of endothelial function after irradiation could potentially limit toxicity. Using the murine endothelioma cell line bEnd2 we show here that induction of heme oxygenase-1 (HO-1) by cobalt protoporphyrine IX (CoPP) inhibits irradiation-induced apoptosis. In contrast, HO-1 induction by tin protoporphyrine IX (SnPP), a HO-1 inhibitor, does not affect survival after irradiation. The protective effects of CoPP could be partially reversed by blockade of HO-1 function with SnPP after induction by CoPP. Vice versa, blockade of HO-1 function by SnPP was reversible using CoPP. Treatment with CoPP inhibited cytochrome c release induced by irradiation. These results demonstrate that HO-1 induction and activation prior to irradiation inhibits endothelial apoptosis and might be used for possible cell protection in vivo.

A role for CD54 (intercellular adhesion molecule-1) in leukocyte recruitment to the lung during the development of experimental idiopathic pneumonia syndrome

Background. Idiopathic pneumonia syndrome (IPS) is a frequently fatal complication of allogeneic bone marrow transplantation (BMT). IPS is associated with elevated bronchoalveolar lavage (BAL) fluid levels of tumor necrosis factor-&agr; and lipopolysaccharide, both of which are potent activators of endothelial cells (ECs). EC expression of the adhesion molecule CD54 (intercellular adhesion molecule [ICAM]-1) has been shown to be a major regulator of pulmonary inflammation in various experimental models. Methods. Using a well-established murine BMT system in which lung injury and graft-versus-host disease (GvHD) are induced by minor histocompatibility antigenic differences between donor and host, the RNase Protection Assay, mice deficient in ICAM-1 expression, and a monoclonal blocking antibody to ICAM, we evaluated the role of the pulmonary vascular expression of CD54 in the development of IPS. Results. Enhanced pulmonary vascular expression of ICAM-1 coincided with the development of IPS. When ICAM-1 −/− mice were used as allogeneic BMT recipients, IPS severity (measured by lung histopathology, BAL cellularity, and cytokine expression) was significantly reduced compared with wild-type controls. Similar results were also observed when wild-type recipients were treated with a monoclonal blocking antibody to ICAM-1. Surprisingly, ICAM-1 had differential effects on leukocyte infiltration into GvHD target organs; ICAM-1 deficiency had no impact on intestinal histopathology, whereas ICAM-1 −/− BMT recipients had significantly enhanced hepatic injury. Conclusions. These data demonstrate that although the expression of ICAM-1 is critical for the development of IPS, different mechanisms of leukocyte recruitment are operative in other GvHD target organs.