Transforming growth factor type beta induces monocyte chemotaxis and growth factor production

Active and latent forms of transforming growth factor beta activity in synovial effusions

We have evaluated the possible involvement of TGF-beta in rheumatoid arthritis by assay of 16 cell-free synovial fluids for the presence of its active and "latent" forms. Evidence has been obtained for TGF-beta-like activity in synovial effusions by four criteria: (a) TGF-beta receptor competition, (b) soft-agar colony formation of AKR-2B and NRK-49F indicator cells, (c) immunological neutralization of the biological activity, and (d) biochemical activation of a latent form.

The effects of TGF beta on haemopoietic cells

Transforming growth factor beta (TGF beta) suppresses the growth of differentiation inducible, murine IL-3-dependent multipotential cell lines but has no growth inhibitory effect upon an IL-3-independent (leukaemic) cell line arising from one of them, nor on IL-3-dependent cell lines that are unable to undergo differentiation. TGF beta inhibits in vitro colony formation by normal multipotential haemopoietic progenitor cells. Bipotential progenitors recruited by GM-CSF are, however, more resistant to the inhibitory effects of TGF beta, whereas progenitors recruited by the lineage restricted factor, M-CSF, are sensitive to the inhibitory effects. These data indicate that responsiveness to TGF beta is differentiation linked and studies with the cell lines suggest that response (or lack of response is not determined solely by levels of expression of TGF beta receptors. Furthermore, the effects of TGF beta 2 on haemopoietic progenitors are very similar to those induced by TGF beta.

Molecular cloning of the chicken myelomonocytic growth factor (cMGF) reveals relationship to interleukin 6 and granulocyte colony stimulating factor

Normal as well as retrovirally transformed avian myeloid precursor cells require the colony stimulating factor cMGF for their survival, proliferation and colony formation in vitro. cMGF has been shown to be a glycoprotein which is active in the picomolar concentration range. Co-expression of kinase type oncogenes in v-myb or v-myc transformed myeloid cells induces cMGF expression and confers factor independence via an autocrine mechanism. Here we describe the molecular cloning of cMGF from a myeloblast cDNA library and show that it is a 201 amino acid residue secretory protein which is modified by signal peptide cleavage and glycosylation during translocation into the lumen of membrane vesicles. A bacterially expressed trpE-cMGF fusion protein induces proliferation of E26 transformed myeloblasts in a cMGF bioassay suggesting that glycosylation is not absolutely necessary for biological activity. Sequence comparison reveals that cMGF is distantly related to G-CSF and IL-6.

Mitogenic regulation of normal and malignant breast epithelium

The multiple roles of both estrogenic and polypeptide regulators of mammary epithelial cell growth are reviewed in this article. Effects of both steroidal and peptide hormones are complex and involve multiple interactions with malignant cells and non-malignant host components. Initial carcinogenesis and progression of mammary epithelium to cancer probably require both proliferative stimuli (estrogen, polypeptide growth factors) and genetic damage. This condition may lead to qualitatively different hormonal responses (hormone-responsive cancer). Estrogens can be shown to induce growth-regulatory polypeptide growth factors and interact with them in hormone-dependent breast cancer. Progression of hormone-dependent (estrogen-responsive) breast cancer to hormone independence probably involves multiple mechanisms, including oncogene activation, loss of the estrogen receptor, or loss of hormone responsivity of other gene products. One direction for further therapies may be blockade of hormonal stimulation and interference with necessary activated or induced components of malignant progression such as oncogenes or polypeptide growth factor-receptor systems.

Bacterial cell wall-induced immunosuppression. Role of transforming growth factor beta

Group A streptococcal cell wall (SCW)-injected rats exhibit a profound immunosuppression that persists for months after the initial intraperitoneal injection of SCW. The goal of this study was to determine the mechanisms for the suppressed T lymphocyte proliferative responses in this experimental model of chronic inflammation. When spleen cell preparations were depleted of adherent cells, restoration of T cell proliferative responses to Con A and PHA occurred, implicating adherent macrophages in the regulation of immunosuppression. Furthermore, macrophages from SCW-treated animals, when cocultured with normal spleen cells in the presence of Con A or PHA, effectively inhibited the proliferative response. Supernatants from suppressed spleen cell cultures were found to inhibit normal T cell mitogenesis. Taken together, these results implicated a soluble macrophage-derived suppressor factor in the down regulation of T cell proliferation after exposure to SCW in vivo. Subsequent in vitro studies to identify this suppressor molecule(s) revealed the activity to be indistinguishable from the polypeptide transforming growth factor beta (TGF-beta). Furthermore, TGF-beta was identified by immunolocalization within the spleens of SCW-injected animals. The cells within the spleen that stained positively for TGF-beta were phagocytic cells that had ingested, and were presumably activated by, the SCW. These studies document that TGF-beta, previously shown to be a potent immunosuppressive agent in vitro, also effectively inhibits immune function in chronic inflammatory lesions in vivo.

Effects of type beta transforming growth factors on haematopoietic progenitor cells

The effects of type beta transforming growth factors (TGF-beta s) on normal human and murine haematopoietic progenitor cells were examined using bone marrow colony assays. In erythroid colony assays, TGF-beta 1 inhibited human CFU-E derived colony formation, BFU-E derived burst formation, and murine BFU-E derived burst formation in a dose dependent manner between 0.1 and 5.0 ng/ml. However, murine CFU-E derived colony formation was unaffected even at a concentration of 5.0 ng/ml TGF-beta 1. In myeloid colony assays, different sensitivity of progenitor cells to the inhibitory effects of TGF-beta s was observed between both species. TGF-beta 1 inhibited murine granulocyte-macrophage colony (GM-colony) formation and granulocyte colony (G-colony) formation in a dose dependent manner between 0.1 and 5.0 ng/ml, but had no remarkable effects on human GM-colony and G-colony formation. TGF-beta 2 also had similar inhibitory effects on haematopoietic progenitor cells, while its inhibitory effect was less potent than that of TGF-beta 1. Thus our data suggest that TGF-beta may be involved in negative regulation of haematopoiesis and that its inhibitory action may be restricted in lineage and/or species specific manner.

Wound macrophages express TGF-alpha and other growth factors in vivo: analysis by mRNA phenotyping

The presence of macrophages is required for the regeneration of many cell types during wound healing. Macrophages have been reported to express a wide range of mitogenic factors and cytokines, but none of these factors has been shown in vivo to sustain all the wound-healing processes. It has been suggested that transforming growth factor-alpha (TGF-alpha) may mediate angiogenesis, epidermal regrowth, and formation of granulation tissue in vivo. Macrophages isolated from a wound site, and not exposed to cell culture conditions, expressed messenger RNA transcripts for TGF-alpha, TGF-beta, platelet-derived growth factor A-chain, and insulin-like growth factor-1. The expression of these transcripts was determined by a novel method for RNA analysis in which low numbers of mouse macrophages were isolated from wound cylinders, their RNA was purified and reverse-transcribed, and the complementary DNA was amplified in a polymerase chain reaction primed with growth factor sequence-specific primers. This single-cell RNA phenotyping procedure is rapid and has the potential for quantification, and mRNA transcripts from a single cell or a few cells can be unambiguously demonstrated, with the simultaneous analysis of several mRNA species. Macrophages from wounds expressed TGF-alpha antigen, and wound fluids contained TGF-alpha. Elicited macrophages in culture also expressed TGF-alpha transcripts and polypeptide in a time-dependent manner after stimulation with modified low-density lipoproteins and lipopolysaccharide endotoxin, which are characteristic of the activators found in injured tissues.

Developmental expression of transforming growth factors alpha and beta in mouse fetus

Expression of mRNA for transforming growth factor alpha (TGF-alpha) and TGF-beta 1 during the fetal development of mice was evaluated by in situ hybridization. TGF-alpha mRNA was detected in 9- and 10-day fetuses but was absent in older fetuses. TGF-alpha mRNA-containing cells were found in the placenta, otic vesicle, oral cavity, pharyngeal pouch, first and second branchial arches, and developing kidneys. mRNA for TGF-beta 1 was present in hematopoietic cells of blood islands and capillaries and in the liver as it began to bud off on day 10 and function as a hematopoietic organ.

Clinical applications of heparin-binding growth factors

The family of HBGFs represents one of the most important families of mediators yet described, capable of inducing mesenchymal cell proliferation and differentiation, tissue regeneration, morphogenesis, and neovascularization, and it is clear their clinical potential is enormous. While some obvious applications of HBGFs, such as in wound healing and seeding of vascular prostheses, are already being examined in detail, the realization of their full clinical potential will require the co-ordinated efforts of many laboratories in a wide spectrum of fields. A better understanding is needed of the pathophysiological roles of HBGFs in vivo. For example, if abnormal expression of HBGFs is the cause of certain pathologies characterized by abnormal vascularization, the clinical potential of HBGF antagonists as inhibitors of angiogenesis will be considerable. A better understanding is also needed of the relationship between HBGF structure and function, susceptibility to proteolysis, in-vivo stability, and synergism with other biological response modifiers. In addition, many clinical applications will be limited by our ability to target HBGFs to selected sites in the body, while others will be limited by undesirable side-effects. Indeed, the minimization of such side-effects may rapidly become a central issue in the in-vivo use of HBGFs. For example, the presence of HBGFs in ocular tissues, their role in phototransduction, their ability to induce neovascularization, and the clear link between abnormal ocular neovascularization and blindness, suggest that the eye may be an organ particularly sensitive to local changes in HBGF levels. Finally, HBGFs will almost certainly have extremely potent immunoregulatory effects. Nevertheless, the application of HBGFs in a variety of clinical situations should lead to many innovative therapeutic advances.

Deactivation of macrophages by transforming growth factor-beta

Macrophage activation--enhanced capacity to kill, in a cell that otherwise mostly scavenges--is essential for host survival from infection and contributes to containment of tumours. Both microbes and tumour cells, therefore, may be under pressure to inhibit or reverse the activation of macrophages. This reasoning led to the demonstration of macrophage deactivating factors from both microbes and tumour cells. In some circumstances the host itself probably requires the ability to deactivate macrophages. Macrophages are essential to the healing of wounds and repair of tissues damaged by inflammation. Yet the cytotoxic products of the activated macrophages can damage endothelium, fibroblasts, smooth muscle and parenchymal cells (reviewed in ref. 6). Thus, after an inflammatory site has been sterilized, the impact of macrophage activation on the host might shift from benefit to detriment. These concepts led us to search for macrophage deactivating effects among polypeptide growth factors that regulate angiogenesis, fibrogenesis and other aspects of tissue repair. Among 11 such factors, two proteins that are 71% similar proved to be potent macrophage deactivators: these are transforming growth factor-beta 1 (TGF-beta 1) and TGF-beta 2.

Transforming growth factor beta (TGF-beta) induces fibrosis in a fetal wound model

The adult cellular response to tissue injury is characterized by acute inflammation followed eventually by fibroblast proliferation and collagen synthesis. Fetal tissue responses to injury differ markedly from those of the adult; an early acute inflammatory response is absent, few fibroblasts participate, and no collagen is deposited. The object of the present study was to analyze the effects of transforming growth factor beta (TGF-beta), an important regulatory molecule in adult healing events, on the fetal tissue response following wounding. Fetal cellular and extracellular matrix responses to injury were evaluated by placing subcutaneous wound implants containing TGF-beta (0.01 to 10 ng) in fetal rabbits at 24 days gestation (term = 31 days). Histologic responses one to seven days later were compared with fetal and adult control implants without TGF-beta. The histology of the adult implant was characterized by an early acute inflammatory response: by day 7 fibroblasts and collagen were predominant. In contrast, control implants removed from fetal rabbits had no histologic evidence of acute inflammation or fibroblast penetration and no collagen was deposited. When implants containing 1.0 ng TGF-beta were removed from fetal rabbits at seven days, a grossly fibrotic reaction was observed: histology confirmed marked fibroblast penetration with collagen deposition. Fetal implants containing 0.01 ng or 10 ng TGF-beta showed few fibroblasts but had increased numbers of inflammatory cells compared with controls. These observations demonstrate that the fetal response becomes adultlike with fibroblast proliferation and collagen accumulation when TGF-beta is added, thus documenting the responsiveness of the fetal system to adult repair signals.(ABSTRACT TRUNCATED AT 250 WORDS)

Transforming growth factor beta stimulates collagen-matrix contraction by fibroblasts: implications for wound healing

An important event during wound healing is the contraction of newly formed connective tissue (granulation tissue) by fibroblasts. The role of polypeptide growth factors in the process of wound contraction was investigated by analyzing the influence of transforming growth factor beta (TGF-beta), platelet-derived growth factor on the ability of fibroblasts to contract a collagen matrix in an in vitro system. TGF-beta, but not the other growth factors tested, markedly enhanced the ability of BHK-21,3T3-L1, and human foreskin fibroblasts to contract collagen gels. These results suggest that TGF-beta released from platelets and inflammatory cells at sites of tissue injury stimulates fibroblasts to contract the provisional wound matrix and that this effect contributes to the ability of TGF-beta to accelerate wound healing.

Transforming growth factor-beta: possible roles in carcinogenesis

TGF-beta is the prototype of a large family of multifunctional regulatory proteins. The principal sources of the peptide, platelets and bone, suggest that it plays a role in healing and remodeling processes. In vitro, TGF-beta is chemotactic for monocytes and fibroblasts and can greatly enhance accumulation of extracellular matrix components by fibroblasts. Its ability to stimulate the formation of granulation tissue locally and the demonstration of specific time- and tissue-dependent expression in embryogenesis suggest that similar mechanisms are operative in vivo. By analogy to its effects in wound healing and embryogenesis, it is proposed that TGF-beta, secreted by tumour cells, can augment tumour growth indirectly by effects on the stromal elements. These effects include suppression of the immune response, and enhancement of both angiogenesis and formation of connective tissue. Many tumour cells have escaped from direct growth inhibitory effects of TGF-beta by a variety of mechanisms including inability to activate the latent form of the peptide, loss of cellular receptors for TGF-beta, and loss of functional intracellular signal transduction pathways.

Cytokines: molecular and biological characteristics

Cytokines are soluble molecules with many cells as the source of their origin and as targets for their actions. They are pleiotropic in their biological functions. Some cytokines are distinct with respect to their molecular structure yet they have overlapping biological properties (Interleukin 1 and tumor necrosis factors). Others are structurally distinct and often have contrasting biological activities (e.g. tumor necrosis factors and transforming growth factor-beta). In this article I have briefly reviewed the molecular and biological properties of four cytokines that appears to play an important role in the pathogenesis of certain immunoinflammatory disorders. It is also to be stressed that there are additional cytokines (e.g. granulocyte-monocyte colony stimulating factors, interleukin 2, interferons etc.) that could also play a role in the pathogenesis of immunoinflammatory disorders.

Role of transforming growth factor-beta in the development of the mouse embryo

Using immunohistochemical methods, we have investigated the role of transforming growth factor-beta (TGF-beta) in the development of the mouse embryo. For detection of TGF-beta in 11-18-d-old embryos, we have used a polyclonal antibody specific for TGF-beta type 1 and the peroxidase-antiperoxidase technique. Staining of TGF-beta is closely associated with mesenchyme per se or with tissues derived from mesenchyme, such as connective tissue, cartilage, and bone. TGF-beta is conspicuous in tissues derived from neural crest mesenchyme, such as the palate, larynx, facial mesenchyme, nasal sinuses, meninges, and teeth. Staining of all of these tissues is greatest during periods of morphogenesis. In many instances, intense staining is seen in mesenchyme when critical interactions with adjacent epithelium occur, as in the development of hair follicles, teeth, and the submandibular gland. Marked staining is also seen when remodeling of mesenchyme or mesoderm occurs, as during formation of digits from limb buds, formation of the palate, and formation of the heart valves. The presence of TGF-beta is often coupled with pronounced angiogenic activity. The histochemical results are discussed in terms of the known biochemical actions of TGF-beta, especially its ability to control both synthesis and degradation of both structural and adhesion molecules of the extracellular matrix.

Effects of growth factors in vivo. I. Cell ingrowth into porous subcutaneous chambers

Growth factors secreted by platelets and macrophages may play roles in atherogenesis and in wound repair. The multiple biologic effects of these factors are being studied extensively in vitro, but their roles in vivo are relatively unexplored. The cellular responses to platelet-derived growth factor (PDGF), transforming growth factor beta (TGF beta), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) were examined in a wound chamber model in rats. Growth factors were emulsified in bovine dermal collagen suspensions, placed in 1 X 30-mm porous polytetrafluoroethylene tubes, inserted subcutaneously, and removed after 10 days. The presence of PDGF (400 ng), TGF beta (200 ng), or bFGF (100 ng) increased the DNA content of the chambers two- to sixfold, compared with controls. Regardless of dose, EGF (100-800 ng) did not affect the DNA content. The increases in DNA observed for PDGF, TGF beta, or bFGF resulted from accumulations of varying numbers of fibroblasts, capillaries, macrophages, and leukocytes in 10-day chambers. The addition of 250 micrograms/ml heparin to the collagen suspension potentiated the response to PDGF and bFGF, but not to TGF beta or EGF. The clearance of 125I-labeled growth factors from the chambers was biphasic. After an initial rapid phase, the remaining growth factor was slowly cleared. The half-life of the initial phase was rapid for PDGF (12 hours) and bFGF (9 hours) and somewhat slower for TGF beta (22 hours). There was no difference in the rate of clearance between collagen and collagen/heparin matrices for any of the growth factors examined. These studies demonstrate that PDGF, bFGF, and TGF beta can induce granulation tissue development in normal animals. The similarity in cellular responses to three peptides with differing in vitro actions suggests that the responses observed at 10 days reflect a secondary process, possibly mediated by effector cells such as macrophages, lymphocytes, or granulocytes that are attracted into the chamber by each growth factor, rather than a direct effect of the factors themselves.

Transforming growth factor-beta: potential common mechanisms mediating its effects on embryogenesis, inflammation-repair, and carcinogenesis

In conclusion, we have demonstrated that a single growth factor, TGF-beta, can act in either an autocrine or paracrine mode to bring about, either directly or indirectly, all of the complex events which together lead to the formation of granulation tissue and tumor stroma. All of the participating cell types, lymphocytes, macrophages, endothelial cells, and fibroblasts have receptors for TGF-beta and many of them secrete TGF-beta as well. Although other growth factors such as platelet-derived growth factor and fibroblast growth factor clearly also participate in these processes, we have shown that TGF-beta, alone, is sufficient to initiate the cascade of events, probably through its ability to chemoattract and to activate macrophages and fibroblasts. Without question, neovascularization and appropriately timed matrix synthesis and degradation are central to embryogenesis as well. Fibronectin, in particular, has been shown to promote cell adhesion and cell migration throughout embryogenesis (Hynes and Yamada, 1982; Rovasio et al., 1983). We propose that TGF-beta will be found to be an important mediator of embryonic development, not only by control of angiogenesis and matrix synthesis, but also by exerting direct local effects on cellular growth and differentiation (reviewed in Roberts and Sporn, 1987).