An essential role for platelet-derived growth factor in neointima formation in human saphenous vein in vitro

The role of platelet-derived growth factor (PDGF), a potent vascular smooth muscle cells (SMC) mitogen and chemoattractant, was investigated during neointima formation in human saphenous vein organ culture. PDGFA and B messenger ribonucleic acid (mRNA) expression was detected by RNase protection assay and in situ hybridisation and PDGF protein by immunocytochemistry. The expression of PDGFA and B mRNA was low in veins before culture while PDGF protein was detected in all cell types. A neointima consisting of densely packed SMC developed after 14 days of culture. The dense packing and high expression of PDGFA and B mRNA in neointimal SMC led to higher PDGF protein concentrations in the neointima, the role of which was examined by culturing with neutralising anti-(human PDGF) antibodies. The anti-PDGF antibodies significantly reduced neointimal thickness by ˜ 66% and the number of neointimal cells by ˜ 50%, without affecting neointimal or medial proliferation indices or cell viability. These results suggest that PDGF played an essential role in SMC migration into the neointima in human saphenous vein.     

Ikaros expression in human hematopoietic lineages

The Ikaros gene has been implicated in lymphoid development and proliferation from the results of gene targeting studies in mice. Recently we reported that the Ikaros gene may be involved in the disease progression of chronic myelogenous leukemia (CML). In this report, we investigated Ikaros isoforms in human non-lymphoid leukemia cell lines and normal granulocyte/macrophage (CFU-GM) and erythroid (BFU-E)-derived colonies.We evaluated Ikaros gene expression by RT-PCR, Southern blotting, sequencing analysis, Northern blotting, and immunoblotting.Ikaros isoforms Ik-1 and Ik-2, 3 were predominantly expressed in human non-lymphoid leukemia cell lines. Ik-4 and Ik-8 were also detectable as a minor population. In contrast to the previous report in mice, multiple Ikaros isoforms were expressed in human CFU-GM and BFU-E-derived colonies, and the dominant-negative isoform Ik-6 was not detectable. We also showed that human Ikaros isoforms contained an additional coding sequence in the N-terminal region, which was highly homologous to the sequence reported in mice.These observations suggest that the Ikaros gene may play some role in the development of human non-lymphoid lineage hematopoiesis. Moreover, the finding that the dominant-negative isoform Ik-6, which was overexpressed in patients with blast crisis of CML, was rarely detectable in non-lymphoid lineages supports its pathogenetic role in human hematologic malignancies.     

The role of growth hormone-releasing factor and somatostatin on somatic growth in rats

The role of GH-releasing factor (GRF) in regulating somatic growth was studied in rats by passively immunizing animals with antisera raised against rat GRF. GRF antiserum (GRF-ab) treatment significantly inhibited the normal increase in body weight observed in both young male and female rats. Similar studies conducted in neonatal rats (days 1-23 of age) also demonstrated that GRF is critical in regulating neonatal growth. The biological half-life of the GRF-ab was determined to be between 2.5 and 3.5 days in these animals. The effects of GRF-ab and somatostatin antiserum (SRIF-ab) treatment on serum GH concentrations were also studied in neonatal rats. Between 1 and 20 days of age, GRF-ab treatment significantly decreased serum GH concentrations compared to those in control animals. From days 1-10 of age, SRIF-ab treatment had no effect on GH concentrations, whereas on days 15 and 20 of age, SRIF-ab treatment significantly increased GH concentrations. The results demonstrate that hypothalamic GRF is critical in regulating serum GH concentrations and somatic growth in neonatal and young animals. They also suggest that the role of SRIF in regulating GH concentrations is not established until sometime after 10 days of age.     

A hematopoietic growth factor, thrombopoietin, has a proapoptotic role in the brain

Central nervous and hematopoietic systems share developmental features. We report that thrombopoietin (TPO), a stimulator of platelet formation, acts in the brain as a counterpart of erythropoietin (EPO), a hematopoietic growth factor with neuroprotective properties. TPO is most prominent in postnatal brain, whereas EPO is abundant in embryonic brain and decreases postnatally. Upon hypoxia, EPO and its receptor are rapidly reexpressed, whereas neuronal TPO and its receptor are down-regulated. Unexpectedly, TPO is strongly proapoptotic in the brain, causing death of newly generated neurons through the Ras-extracellular signal-regulated kinase 1/2 pathway. This effect is not only inhibited by EPO but also by neurotrophins. We suggest that the proapoptotic function of TPO helps to select for neurons that have acquired target-derived neurotrophic support.     

An essential regulatory role for macrophage migration inhibitory factor in T-cell activation.

The protein known as macrophage migration inhibitory factor (MIF) was one of the first cytokines to be discovered and was described 30 years ago to be a T-cell-derived factor that inhibited the random migration of macrophages in vitro. A much broader role for MIF has emerged recently as a result of studies that have demonstrated it to be released from the anterior pituitary gland in vivo. MIF also is the first protein that has been identified to be secreted from monocytes/macrophages upon glucocorticoid stimulation. Once released, MIF acts to "override" or counter-regulate the suppressive effects of glucocorticoids on macrophage cytokine production. We report herein that MIF plays an important regulatory role in the activation of T cells induced by mitogenic or antigenic stimuli. Activated T cells produce MIF and neutralizing anti-MIF antibodies inhibit T-cell proliferation and interleukin 2 production in vitro, and suppress antigen-driven T-cell activation and antibody production in vivo. T cells also release MIF in response to glucocorticoid stimulation and MIF acts to override glucocorticoid inhibition of T-cell proliferation and interleukin 2 and interferon gamma production. These studies indicate that MIF acts in concert with glucocorticoids to control T-cell activation and assign a previously unsuspected but critical role for MIF in antigen-specific immune responses.     

Hepatocyte growth factor is a synergistic factor for the growth of hematopoietic progenitor cells.

Bone marrow (BM) stromal cells, which include macrophages, fibroblasts, endothelial cells, and adipocytes, have been shown to produce several factors that modulate the growth of BM progenitors. Hepatocyte growth factor (HGF) is a fibroblast-derived factor and has recently been shown to be a ligand for the c-met proto-oncogene, a member of the receptor class of tyrosine kinases. c-met messenger RNA (mRNA) is predominantly expressed in epithelial cells, but has been detected in several murine hematopoietic progenitor cell lines, suggesting that HGF and met might function during hematopoiesis. Here, BM cells were found to express both met mRNA and protein. Moreover, HGF was shown to synergize with interleukin-3 and granulocyte-macrophage colony-stimulating factor to stimulate colony formation of hematopoietic progenitor cells in vitro. These results show that, in addition to its activity on epithelial cells, HGF is a new member of the functionally related group of factors that modulate hematopoiesis.     

A role for the transcription intermediary factor 2 in zebrafish myelopoiesis

OBJECTIVE: TIF2 is fused with MOZ in the inv(8)(p11q13) acute myeloid leukemia. TIF2, member of the p160 family, is a histone acetyl transferase (HAT). Deletion of p160 genes were performed in mice. Some observations suggest that p160 family members may perform overlapping functions in mice. Therefore, we decided to choose the zebrafish model to study TIF2. The aim of this study was to characterize the role of this HAT during embryonic development. MATERIAL AND METHODS: We use antisense, morpholino-modified oligomers to transiently knockdown tif2 gene, thus determining whether TIF2 plays a role in zebrafish early development. RESULTS: We show that tif2 is involved in embryogenesis and in primitive hematopoiesis. tif2-knockdown zebrafish embryos are smaller than controls, they demonstrate shorter tails, they display notochord deformation and they exhibit U-shaped tail somites. A synthetic RNA encoding human TIF2 rescues the tif2-knockdown phenotype. Analysis of fli1 expression by whole-mount in situ hybridization indicates normal angioblast specification, but altered localization of intersomitic vessels. The posterior intermediate cell mass, in which a part of primitive hematopoiesis occurs, is altered in tif2 morphants and whole-mount in situ hybridization analyses of l-plastin and mpx expression suggest a specific inhibition of granulocytic and macrophagic differentiation at late stages. CONCLUSION: These data indicate an important role for TIF2 in zebrafish primitive myelopoiesis.     

造血细胞生长因子FL变化在胚胎期造血中的临床意义

目的　检测胎盘绒毛组织及脐血中造血细胞生长因子酪氨酸激酶受体 3(Flt3)配体 (FL )开始出现的时间及其随胎龄增长的含量变化 ,探讨其在胚胎期造血中的意义。方法　分别取妊娠早期 (6～ 8周 )、妊娠中期(16～ 2 2周 )、妊娠晚期 (37～ 4 2周 )胎盘绒毛组织 2 g各 30份、脐血清 30份 ,采用酶联免疫吸附法测定上清液中的 FL 含量。结果　 1早期妊娠开始 FL 已产生 ;其含量随着胎龄增加而逐渐增加 ,各胎龄组间比较有显著性差异(P<0 .0 1)。2 FL 在胎盘和脐动静脉血中的含量有显著性差异 (P<0 .0 1)。结论　 FL 来源于胎盘 ,在整个胚胎期造血过程中发挥重要作用