Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. Hypoxia has been shown to be a major inducer of VEGF gene transcription. The tyrosine kinases Flt-1 (VEGFR-1) and Flk-1/KDR (VEGFR-2) are high-affinity VEGF receptors. The role of VEGF in developmental angiogenesis is emphasized by the finding that loss of a single VEGF allele results in defective vascularization and early embryonic lethality. VEGF is critical also for reproductive and bone angiogenesis. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with various VEGF inhibitors in a variety of malignancies are ongoing. Very recently, an anti-VEGF monoclonal antibody (bevacizumab; Avastin) has been approved by the Food and Drug Administration as a first-line treatment for metastatic colorectal cancer in combination with chemotherapy. Furthermore, VEGF is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.

/pdf/vascular-endothelial-growth-factor-basic-science-and-17gyy6h97s.pdf

Vascular endothelial growth factor: basic science and clinical progress.

Werner, Sabine, and Richard Grose. Regulation of Wound Healing by Growth Factors and Cytokines. Physiol Rev 83: 835–870, 2003; 10.1152/physrev.00032.2002.—Cutaneous wound healing is a complex proce...

/pdf/regulation-of-wound-healing-by-growth-factors-and-cytokines-2zk7orhjdk.pdf

Regulation of Wound Healing by Growth Factors and Cytokines

Mouse bone marrow hematopoietic stem cells were isolated with the use of a variety of phenotypic markers. These cells can proliferate and differentiate with approximately unit efficiency into myelomonocytic cells, B cells, or T cells. Thirty of these cells are sufficient to save 50 percent of lethally irradiated mice, and to reconstitute all blood cell types in the survivors.

https://science.sciencemag.org/content/sci/241/4861/58.full.pdf

Purification and Characterization of Mouse Hematopoietic Stem Cells

Fibroblast growth factors (FGFs) make up a large family of polypeptide growth factors that are found in organisms ranging from nematodes to humans. In vertebrates, the 22 members of the FGF family range in molecular mass from 17 to 34 kDa and share 13-71% amino acid identity. Between vertebrate species, FGFs are highly conserved in both gene structure and amino-acid sequence. FGFs have a high affinity for heparan sulfate proteoglycans and require heparan sulfate to activate one of four cell-surface FGF receptors. During embryonic development, FGFs have diverse roles in regulating cell proliferation, migration and differentiation. In the adult organism, FGFs are homeostatic factors and function in tissue repair and response to injury. When inappropriately expressed, some FGFs can contribute to the pathogenesis of cancer. A subset of the FGF family, expressed in adult tissue, is important for neuronal signal transduction in the central and peripheral nervous systems.

/pdf/fibroblast-growth-factors-10fhny1vm8.pdf

Fibroblast growth factors

The most debilitating human lymphoid deficiency disease, known as severe combined immunodeficiency (SCID), impairs the differentiation of both T and B lymphocytes. Affected infants are highly susceptible to recurring infections of viruses, fungi and bacteria and invariably die within 2 yr of birth. Inheritance of this congenital syndrome may show X-linked or autosomal recessive control. To date autosomal recessive inheritance of SCID has been observed in Arabian foals which represent the only known animal model of this disease syndrome but here we report an autosomal recessive mutation in mice that severely impairs lymphopoiesis. Mice homozygous for this mutation have few if any lymphocytes; consequently they are hypogammaglobulinaemic and deficient for immune functions mediated by T and B lymphocytes. These mice, therefore, represent a new model for investigating how lymphoid differentiation may be impaired in the disease state and regulated in the normal state.

A severe combined immunodeficiency mutation in the mouse

Fibroblast growth factor 1 (FGF1) and FGF2, the prototypic members of the FGF family of growth factors, have been implicated in a variety of physiological and pathological processes. Unlike most other FGFs, FGF1 and FGF2 are ubiquitously expressed and are not efficiently secreted. Gene knockouts in mice have previously demonstrated a role for FGF2 in brain development, blood pressure regulation, and wound healing. The relatively mild phenotypic defects associated with FGF2 deletion led to the hypothesis that the continued expression of other FGFs partially compensated for the absence of FGF2 in these mice. We now report our generation of mice lacking FGF1 and their use, in combination with our previously described FGF2 null mice, to produce mice lacking both FGF1 and FGF2. FGF1-FGF2 double-knockout mice are viable and fertile and do not display any gross phenotypic defects. In the double-knockout mice we observed defects that were similar in extent to those previously described for the FGF2 null mice. Differences in the organization of neurons of the frontal motor cortex and in the rates of wound healing were observed. We also observed in FGF2−/− mice and in FGF1-FGF2 double-knockout mice novel impairments in hematopoiesis that were similar in severity. Essentially no abnormalities were found in mice lacking only FGF1. Our results suggest that the relatively mild defects in FGF2 knockout animals are not a consequence of compensation by FGF1 and suggest highly restricted roles for both factors under normal developmental and physiological conditions.

Compensation by Fibroblast Growth Factor 1 (FGF1) Does Not Account for the Mild Phenotypic Defects Observed in FGF2 Null Mice

A quantitative assay for the hematopoietic precursor of thymocytes has been developed. Using this assay the kinetics of appearance of the progeny of transfused bone marrow and spleen cells in the thymus of irradiated (760 R) mice has been studied. Precursor cells are seven to eightfold more common in bone marrow than in spleen and are absent from peripheral lymph nodes. They decline in number as the animals age. When hematopoietic cells are injected immediately after lethal irradiation only a small number of cells actually enter the gland. Their progeny are not detectable in the thymus for 8-12 days. The time of their detection depends both upon the size of the residual endogenous thymocyte population and the number of progenitor cells injected. Evidence has been presented that excludes thymic injury as the basis for the delay in the appearance of donor type cells and indicates that neither the production of a "homing" signal in the irradiated animal nor the development of precursor cells are limiting factors in the rate of thymic repopulation. These studies indicate that only an exceedingly small number (less than 100) of prothymocytes are required to repopulate the thymus of an irradiated mouse. This restricted number of progenitors must produce the entire repertory of T-cell immunologic responsiveness seen in the first weeks after repopulation.

/pdf/hematopoietic-thymocyte-precursors-i-assay-and-kinetics-of-3xl7ac29gg.pdf

Hematopoietic thymocyte precursors. I. Assay and kinetics of the appearance of progeny.

In an attempt to analyze the cellular and molecular basis of the capacity of bone marrow stromal cells to support hematopoiesis in culture, we developed a series of murine stromal cell lines from a single long-term bone marrow culture (BMC). The cytokines produced by these cells were analyzed using immunohistochemical techniques, ribonuclease protection assays (RPA) and RT-PCR. We examined the capacity of these cloned cell lines to replace primary bone marrow-derived stromal cells in long-term bone marrow cultures (LT-BMC) and sought correlations between the capacity to support hematopoiesis in culture with the production of known cytokines. These immortalized lines replicate many of the functions of the hematopoietic microenvironment. They express cytokines known to play a role in hematopoiesis. All of the lines constitutively express mRNA for PBSF (SDF-1), macrophage colony-stimulating factor (M-CSF), stem cell factor (SCF), FLT-3, thrombopoietin (TPO), interleukin 7 (IL-7), leukemia inhibitory factor (LIF), tumor necrosis factor-beta (TNF-beta), and interferon-gamma (IFN-gamma). Most lines also express granulocyte-macrophage colony-stimulating factor (GM-CSF) and G-CSF. They vary in their expression of IL-6, tumor growth factor-beta1 (TGF-beta1), TGF-beta2, and TNF-alpha. Growing these lines in the presence of cytokines that influence hematopoiesis alters the levels of cytokine message. The most striking effects were produced by TNF-alpha. In addition to the cytokine mRNAs, the cell lines express factors associated with bone formation such as osteoblast-specific factor-2 (OSF-2) and bone morphogenetic protein-1 (BMP-1). They also express the neural cell-adhesion molecule neuropilin and neurotrophic factors including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Several of the lines can maintain hematopoiesis in culture, as measured by the continuous production of myeloid colony-forming cells (CFU-c), for months. This capacity to support hematopoiesis does not correlate with any pattern of cytokine expression. Several of these lines also support the growth of human hematopoietic cells, and human CFU-c can be detected in the cultures in which CD34(+) bone marrow cells (BMC) are cultured on murine stromal cells. No correlation between the production of any of the known cytokines and the ability to support murine hematopoiesis was detected. In addition, there was no correlation between the capacity to support murine hematopoiesis and the capacity to maintain human HSC. Despite repeated cloning, the lines remain heterogeneous and are capable of producing cells with the properties of fibroblasts, osteoblasts, adipocytes, and myoblasts. In addition to the cytokine mRNAs, the cell lines express factors associated with bone formation such as OSF-2 and BMP-1. They also express the neural cell-adhesion molecule neuropilin and neurotrophic factors including NGF and BDNF.

Immortalized multipotential mesenchymal cells and the hematopoietic microenvironment.

Blood platelets contain angiopoietin-1, a growth factor essential for blood vessel development via stabilization of proliferating endothelial cells. It has recently been reported that angiopoietin-1 can act as a vascular stability factor (Nature Medicine 6:460, 2000). In investigating the normal tissue distribution of angiopoietin-1 from surgically-removed frozen specimens by RT-PCR, we found it consistently present in platelets and megakaryocytes, usually absent in relatively non-vascular tissue: breast, colon, lung, skin, kidney, thyroid, testicle, cervix and occasionally present in tissue enriched with vasculature: prostate, endometrium, ovary, under conditions in which mRNA stability was verified by the positive detection of internal control, actin mRNA. The consistent distribution in platelets and relatively absent distribution in non-vascular normal tissue suggested that the well-known role of platelets in maintaining vascular stability, may in part be due to platelet release of angiopoietin-1 following platelet activation. In this communication we report the incidence of Ang-1 in various normal tissues and demonstrate that thrombin-treated human platelets release angiopoietin-1 in vitro.

Thrombin induces the release of angiopoietin-1 from platelets.

Thymin, a purified polypeptide isolated from bovine thymus, was shown to induce the expression of differentiation antigens characteristic of thymocytes [TL and Thy-1 (θ)] when incubated in vitro with mouse bone marrow or spleen cells This induction occurred in 5-10% of the cells from bone marrow after a 2-hr incubation with subnanogram concentrations of thymin The induced cells expressed more TL and Thy-1 (θ) antigens than average normal thymocytes

Ross S. Basch

Papers

Compensation by Fibroblast Growth Factor 1 (FGF1) Does Not Account for the Mild Phenotypic Defects Observed in FGF2 Null Mice

Hematopoietic thymocyte precursors. I. Assay and kinetics of the appearance of progeny.

Immortalized multipotential mesenchymal cells and the hematopoietic microenvironment.

Thrombin induces the release of angiopoietin-1 from platelets.

Induction of T-cell differentiation in vitro by thymin, a purified polypeptide hormone of the thymus.