Potential Role Of Growth Factors Research Articles

The use of growth factors in clinical practice.

The first in a two-part article reviewing the current and potential role of growth factors

A quantitative histometric murine in vivo model of radiation-induced oral mucositis

Gastrointestinal toxicity is a limiting factor in the effectiveness of cancer therapy. This toxicity is most visible in the mouth. There is considerable interest in developing strategies involving growth-factor manipulation of the epithelial stem cells to afford protection to these cells during treatment and/or to speed up the regenerative process following treatment. In order for this to be achieved, studies have to be undertaken in animal systems to demonstrate the proof of principle and determine optimal protocols. Here, a murine model for oral mucositis based on measurements of tissue cellularity at various times after exposure to radiation was used to investigate cytotoxicity. Several sites in the mouth were analysed and the pronounced circadian rhythm in these various epithelial sites determined. The circadian rhythm is important in that it would determine the timing of administration of growth factors. A microscope with an interactive computer was used to define areas of epithelium and lengths of basal layer, within which, and along which, the total number of cell nuclei was determined over a range of times following exposure to 10, 20 and 30 Gy of X-rays. For various practical reasons, the ventral surface of the tongue was identified as the most appropriate tissue to analyse. Here, measurements of cellularity reached minimum values between 6 and 8 days following 20 Gy. Labelling of S-phase cells demonstrated foci of regeneration and a burst of proliferative regeneration that commenced at about 5 days and reached peak values at 8 days after irradiation. This burst of regenerative proliferation was coincident with the minimum in tissue cellularity on about day 8. The lower dose of radiation (10 Gy) had minimal effects on cellularity; after the higher dose (30 Gy), there was clearly a more severe level of cellular depletion. This quantitative model of oral mucositis could be used to study the effects of other cytotoxics, including combinations of agents, and the potential role of growth factors to reduce the severity of the cellular depletion and to speed up the kinetics of regeneration.

Endothelial regrowth after arterial injury: from vascular repair to therapeutics.

Time for primary review 32 days. Interventional strategies for patients with coronary artery disease such as percutaneous transluminal coronary angioplasty or coronary stent implantation invariably result in a marked degree of vascular injury (deendothelialization, mechanical damage to the medial and adventitial layers) [1–3]. The loss of the endothelial monolayer is associated with a variety of deleterious consequences such as thrombus formation, neointimal thickening, and abnormal responses to endothelium-dependent agonists [3–5]. These effects may contribute to each of the known limitations of these techniques (vessel occlusion, restenosis, coronary spasm). The objective of the present review will be to present applied reendothelialization as a possible treatment for patients with coronary artery disease undergoing mechanical revascularization. Our aim will be twofold: first, to summarize current knowledge on the beneficial effect of endothelial regrowth after arterial injury; second, to discuss the potential role of growth factors or other compounds to accelerate reendothelialization. Occupying a strategically important location between circulating blood and tissues and having the ability to respond to changes in its physical, chemical, and humoral environment by the production of bioactive substances, the normal endothelium controls the tone and the proliferative state of the underlying vascular smooth muscle cells (VSMCs) and maintains a non-adhesive luminal surface. Modulation of VSMC tone is mediated by the synthesis and release of endothelium-derived relaxing and contracting factors. The proliferative state of VSMCs is controlled through these endothelium-derived factors and through the secretion of matrix proteins. Anticoagulant, fibrinolytic, and antithrombotic properties of the endothelium contribute to the maintenance of the fluidity of the blood. ### 1.1 Endothelium-dependent vasomotion #### 1.1.1 Relaxing factors Prostacyclin (PGI2), a potent vasorelaxant and platelet-inhibitory metabolite of arachidonic acid was the first endothelium-derived vasoactive factor discovered [6]. After the seminal observation of Furchgott and Zawadski in 1980 [7]that an intact endothelial layer was required for acetylcholine-induced vasorelaxation, … * Corresponding author. Service de Cardiologie B, Hopital Cardiologique, Boulevard du Professeur J. Leclercq, 59037 Lille Cedex, France. Tel. (+33-3) 2044 5302; Fax (+33-3) 2053 5874; E-mail: cbauters@chru-lille.fr

Multiple extracellular signals promote osteoblast survival and apoptosis.

Programed cell death (PCD) or apoptosis is a naturally occurring cell suicide pathway induced in a variety of cell types. In many cases, PCD apparently arises as a result of competition for limiting amounts of survival signals. In this study, we have investigated the potential role of growth factors (GF), cytokines, and osteotropic hormones on osteoblast survival in vitro. Our results indicate that in the absence of any of these factors, osteoblasts rapidly undergo PCD, as determined by cell morphology, mitochondrial function, and nuclei fragmentation. Osteoblast survival was promoted by insulin-like growth factor I (IGF-I), IGF-II, insulin, and basic fibroblast growth factor (bFGF). Platelet-derived growth factor had no effect on osteoblast survival, but this GF potentiated the survival-promoting effects of IGF-I, IGF-II, and insulin. A similar effect occurred when bFGF was added in combination with either of the IGFs or insulin. The effects of the IGFs were blocked by alphaIR-3, an antibody to the type I IGF receptor, whereas the effects of insulin were only partially blocked. This antibody blocked the potentiating effects of platelet-derived growth factor on IGF-I-mediated osteoblast survival, but only partially blocked those of bFGF. Although a 100% survival of osteoblasts was seen in the presence of 2% FCS, the highest level attained by any of the above GF combinations was approximately 75%. The monocyte-derived factor, tumor necrosis factor-alpha (TNF alpha) was the only agent that enhanced PCD in this study. These results suggest that osteoblast survival is promoted by those GFs sequestrated in bone matrix and that the type I, but not the type II, IGF receptor is involved in the response. Our data also indicate that other unidentified GFs or components of the extracellular matrix may be involved in promoting osteoblast survival and that TNF alpha may abrogate their effects in vivo. We propose that these GFs may be released from bone matrix during phases of bone resorption and promote osteoblast survival, thereby playing an important role in bone remodeling, and that PCD induced by TNF alpha may contribute to the bone loss in inflammatory bone disease.

Multiple Extracellular Signals Promote Osteoblast Survival and Apoptosis

Programed cell death (PCD) or apoptosis is a naturally occurring cell suicide pathway induced in a variety of cell types. In many cases, PCD apparently arises as a result of competition for limiting amounts of survival signals. In this study, we have investigated the potential role of growth factors (GF), cytokines, and osteotropic hormones on osteoblast survival in vitro. Our results indicate that in the absence of any of these factors, osteoblasts rapidly undergo PCD, as determined by cell morphology, mitochondrial function, and nuclei fragmentation. Osteoblast survival was promoted by insulin-like growth factor I (IGF-I), IGF-II, insulin, and basic fibroblast growth factor (bFGF). Platelet-derived growth factor had no effect on osteoblast survival, but this GF potentiated the survival-promoting effects of IGF-I, IGF-II, and insulin. A similar effect occurred when bFGF was added in combination with either of the IGFs or insulin. The effects of the IGFs were blocked by αIR-3, an antibody to the type I IGF receptor, whereas the effects of insulin were only partially blocked. This antibody blocked the potentiating effects of platelet-derived growth factor on IGF-I-mediated osteoblast survival, but only partially blocked those of bFGF. Although a 100% survival of osteoblasts was seen in the presence of 2% FCS, the highest level attained by any of the above GF combinations was ∼75%. The monocyte-derived factor, tumor necrosis factor-α (TNFα) was the only agent that enhanced PCD in this study. These results suggest that osteoblast survival is promoted by those GFs sequestrated in bone matrix and that the type I, but not the type II, IGF receptor is involved in the response. Our data also indicate that other unidentified GFs or components of the extracellular matrix may be involved in promoting osteoblast survival and that TNFα may abrogate their effects in vivo. We propose that these GFs may be released from bone matrix during phases of bone resorption and promote osteoblast survival, thereby playing an important role in bone remodeling, and that PCD induced by TNFα may contribute to the bone loss in inflammatory bone disease.

Cellular and molecular mechanisms in the pathogenesis of severe pulmonary hypertension

Chronic pulmonary hypertension leads to structural alterations of the lung vessels. The pathophysiology of this remodelling process is still poorly understood. Furthermore, the structural damage of the lung vessels limits the clinical success of vasodilator treatment. Given a genetic susceptibility, shear stress and inflammation are the principal pathogenetic factors involved in lung vessel remodelling. In this overview, we compared the lung vascular histology of patients with unexplained pulmonary hypertension, scleroderma, or acquired immune deficiency syndrome (AIDS)-associated pulmonary hypertension. We demonstrate the presence of inflammatory cells (T- and B-lymphocytes and macrophages) in plexiform lesions and discuss the potential role of growth factors (platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF) in pulmonary hypertensive remodelling. Ultimately, we need to develop an in-depth understanding of the key mechanisms of gene expression and signalling pathways, which transduce signals generated from increased chronic shear stress (or from chronic hypoxia) and lead to vascular injury and repair.

Growth factors in monoclonal light-chain-related renal diseases

The immunomorphological expressions of monoclonal light-chain-related renal diseases (MLCRRD) are extremely varied but have a common pathogenetic feature: monoclonal light-chain deposition. The underlying cellular events involved in these processes are likely a reflection of interactions of a complex cascade of inciting and modulating factors. This study explored the potential role of growth factors in MLCRRD by examining the expression of insulin-like growth factor (IGF-I), fibroblast growth factor (FGF), transforming growth factor-beta (TGF-β), and platelet-derived growth factor A chain (PDGF-A) and B chain (PDGF-B) in 36 cases of MLCRRD. All growth factors examined were expressed in tubules, primarily proximal, but to varying extent. Intensity of IGF-I and TGF-β tubular staining correlated with tubular injury and interstitial fibrosis. Intensity of tubular staining with antibodies to FGF also correlated with interstitial fibrosis. Platelet-derived growth factor B chain was strongly detected in glomeruli and, in some cases, in vascular structures. Transforming growth factor-beta was detected only in glomeruli of three patients with nodular glomerulopathy associated with light-chain-deposition disease. Insulin-like growth factor, FGF, and PDGF-A were not detected in glomeruli or vessels in any of the cases. Proliferating cell nuclear antigen (PCNA) staining in tubules and glomeruli was markedly increased in light-chain-deposition disease and less but still significantly increased above control values in the other variants of MLCRRD. These results suggested: (1) a correlation between IGF-I and TGF-β staining in the tubular interstitium and tubular damage; (2) a correlation between IGF-I, TGF-β, and FGF staining in the tubular interstitium and interstitial fibrosis; (3) a likeyly important role for PDGF-B activation in certain glomerular alterations that occur in MLCRRD; (4) a role for TGF-β in light-chain-deposition disease; and (5) the presence of a significant proliferation signal in all cases of MLCRRD but most notably in light-chain-deposition disease in glomerular and tubular compartments. A cascade of events related to growth factor activation appears to play a fundamental role in the pathophysiological processes governing MLCRRD.

PROTEASES AND INVASION BY METASTATIC TUMOR-CELLS - CLINICAL IMPLICATIONS FOR PROSTATE-CANCER

Proteases have been widely implicated in tumor invasion and metastases. Likewise, receptors for MMP-2, alpha(2)M, UA and tPA may play a critical regulatory role in modulation protease activity and invasion. These studies have been largely based on in vitro assays with various tumor lines. More recently in situ studies have indicated that metalloproteinases (e.g. MMP-2, UA, tPA) may serve as useful diagnostic or prognostic indicators of tumor progression and metastatic potential. The development of in vitro diagnostic procedures utilizing primary epithelial prostate cultures is considered. Also the potential role of growth factors (PDGF, EGF, TGFB) in the regulation of metalloprotease production is considered. Finally, approaches to drug design and development of chemotherapy regimens are considered which selectively block invasive behavior of metastatically aggressive tumors.

Potential role of growth factors in global brain ischemia and reperfusion. Observation of insulin-driven tyrosine phosphorylation of a 90-kDa protein during reperfusion.

Potential role of growth factors in global brain ischemia and reperfusion. Observation of insulin-driven tyrosine phosphorylation of a 90-kDa protein during reperfusion.

Activation of the cytotactin promoter by the homeobox-containing gene Evx-1.

Cytotactin is a morphoregulatory molecule of the extracellular matrix affecting cell shape, division, and migration that appears in a characteristic and complex site-restricted pattern during embryogenesis. The promoter region of the gene that encodes chicken cytotactin contains a variety of potential regulatory sequences. These include putative binding sites for homeodomain proteins and a phorbol 12-O-tetradecanoate 13-acetate response element (TRE)/AP-1 element, a potential target for transcription factors thought to be involved in growth-factor signal transduction. To determine the effects of homeobox-containing genes on cytotactin promoter activity, we conducted a series of cotransfection experiments on NIH 3T3 cells using cytotactin promoter-chloramphenicol acetyltransferase (CAT) reporter gene constructs and plasmids driving the expression of mouse homeobox genes Evx-1 and Hox-1.3. cotransfection with Evx-1 stimulated cytotactin promoter activity whereas cotransfection in control experiments with Hox-1.3 had no effect. To localize the sequences required for Evx-1 activation, we tested a series of deletions in the cytotactin promoter. An 89-base-pair region containing a consensus TRE/AP-1 element was found to be required for activation. An oligonucleotide segment containing this TRE/AP-1 site was found to confer Evx-1 inducibility on a simian virus 40 minimal promoter; mutation of the TRE/AP-1 site abolished this activity. To explore the potential role of growth factors in cytotactin promoter activation, chicken embryo fibroblasts, which are known to synthesize cytotactin, were first transfected with cytotactin promoter constructs and cultured under minimal conditions in 1% fetal bovine serum. Although the cells exhibited only low levels of CAT activity under these conditions, cells exposed for 12 h to 10% (vol/vol) fetal bovine serum showed a marked increase in CAT activity. Cotransfection with Evx-1 and cytotactin promoter constructs of cells cultured in 1% fetal bovine serum was sufficient, however, to produce high levels of CAT activity. These findings are consistent with the hypothesis that Evx-1, a homeobox-containing gene, may activate the cytotactin promoter by a mechanism involving a growth-factor signal transduction pathway. More generally, the results support the hypothesis that the place-dependent expression of morphoregulatory molecules may depend upon local cues provided by homeobox genes and their encoded proteins.

Obligatory action of polypeptide growth factors for the IL-1-mediated prostaglandin E2 production in fibroblasts: potential role of growth factors in modulation of tissue response to IL-1.

Obligatory action of polypeptide growth factors for the IL-1-mediated prostaglandin E2 production in fibroblasts: potential role of growth factors in modulation of tissue response to IL-1.

Expression of growth factors during the differentiation of embryonic stem cells in monolayer

Embryonic stem (ES) cells, derived in culture directly from the inner cells mass (ICM) of blastocysts, more closely resemble their embryonic counterparts than the more commonly used embryonal carcinoma (EC) cells derived from teratocarcinomas. In view of the potential role of growth factors in early development, we have now followed changes in the expression of transforming growth factor β (in particular TGFβ 1, β 3, β 4), platelet-derived growth factor (PDGF-A, PDGF-B) and insulin-like growth factor (IGF II) during the differentiation of ES cells in monolayer. When maintained in medium conditioned by Buffalo rat liver cells (BRL-CM) to inhibit differentiation, ES cells expressed 2.5 and 1.8 kb transcripts for TGFβ 1, as well as transcripts for TGFβ 4, PDGF-A, and low levels of PDGF-B, but not TGFβ 3 or IGF II. After formation of parietal endoderm-like cells by addition of retinoic acid (RA) to BRL-CM, the 1.8-kb transcript of TGFβ 1 and PDGF-A expression were reduced, IGF II mRNA and a single TGFβ 3 transcript of 3.8 kb were induced while PDGF-B and TGFβ 4 remained virtually unchanged. By contrast, in ES cells induced to differentiate by the absence of BRL-CM, unusual transcripts for TGFβ 3 of 3.0 and 6.0 kb became detectable and PDGF-B expression increased. The changes in growth factor expression in ES cells are compared with those in F9 and P19 EC cells induced to differentiate in monolayer by RA.

Obligatory action of polypeptide growth factors for the IL-1-mediated prostaglandin E2 production in fibroblasts. Potential role of growth factors in modulation of tissue response to IL-1.

Our studies show that in connective tissue cells, induction of PGE2 synthesis in response to IL-1 requires costimulation with platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF). In cells incubated in medium containing fresh serum, IL-1 induced a dose-dependent synthesis of PGE2. However, when the cells were incubated in medium containing low serum or platelet poor plasma (lacking PDGF), IL-1 alone failed to induce PGE2 synthesis. PGE2 synthesis was restored when platelet poor plasma was supplemented with PDGF. Addition of PDGF or FGF together with IL-1 resulted in a 14- and 66-fold stimulation of PGE2 synthesis, respectively. Stimulation was dependent on the concentration of both IL-1 and the growth factor. PGE2 synthesis was also dependent on the synthesis of new proteins. In cells simultaneously treated with IL-1 and PDGF, PGE2 synthesis was initiated after a lag of 2 to 3 h, proceeded first with a rapid rate for 6 h, and then with a slower rate through 24 h. PGE2 synthesis during the latter, slower phase was greatly enhanced by pretreatment with PDGF, but not by pretreatment with IL-1. PDGF pretreatment also resulted in maintenance of 10- to 12-fold higher cell surface IL-1-binding during this phase. These data provide evidence for potentially novel interactions between PDGF and IL-1 activities, one of which is the modulation of IL-1 receptors by PDGF. Furthermore, these studies suggest that by virtue of their effect on IL-1 activities, PDGF and FGF may play additional roles in connective tissues, including an indirect role in inflammatory processes.

Lymphohematopoiesis: Role of Growth Factors in Leukemogenesis and Therapy

The interrelationship between proliferation, differentiation, and activation responses of hematopoietic progenitor cells and mature blood cells is complex. Therefore, we are only now learning what role colony-stimulating factors play in the regulation of normal hematopoiesis in vivo and in the dysregulation of hematopoiesis in leukemia. Recent advantages in molecular hematology have opened the door to the therapeutic administration of recombinant growth factors. Through continued preclinical trials in animals and by clinical trials in humans, a better understanding of the precise target cells and mechanisms of action of hematopoietic growth factors will improve the therapeutic index of administering colony-stimulating factors. Better understanding of hematopoietic growth factors will, in turn, suggest novel approaches to therapy of acute lymphoblastic leukemia.

Editorial: the potential role of growth factors in clinical medicine

Editorial: the potential role of growth factors in clinical medicine