Stimulation of the chemotactic migration of human fibroblasts by transforming growth factor beta

Platelet-derived growth factor in combination with collagen promotes the migration of human skin fibroblasts into a denuded area of a cell monolayer

Since we have found previously that adult donor skin fibroblasts (TIG-114) migrated more slowly in serum-depleted medium than in medium supplemented with 10% FBS, we tried to identify a factor(s) which promotes fibroblast migration from the edge of a denuded area in a monolayer. In medium supplemented with 10% FBS, the effects of both suramin, a competitor of growth factors at the receptor level, and monensin, an inhibitor of the secretion of extracellular matrix, were examined. Both substances suppressed cell migration, suggesting that growth factors and matrix substances are important for cell migration. Then, we examined the effects of growth factors and extracellular matrix on fibroblast migration in serum-free medium. Platelet-derived growth factor (PDGF), basic fibroblast growth factor, acidic fibroblast growth factor, and transforming growth factor-beta did not stimulate cell migration. Type I collagen, plasma fibronectin, and heparin also did not promote cell migration. However, the combination of PDGF and type I collagen did promote cell migration. Addition of anti-PDGF antibody reduced the stimulatory effect induced by the combination of PDGF and type I collagen. These results suggest that the copresence of growth factors and extracellular matrix regulates fibroblast migration into a denuded area in a monolayer.

The neurogenic locus brainiac cooperates with the Drosophila EGF receptor to establish the ovarian follicle and to determine its dorsal-ventral polarity

We have characterized the function of a new neurogenic locus, brainiac (brn), during oogenesis. Homozygous brn females lay eggs with fused dorsal appendages, a phenotype associated with torpedo (top) alleles of the Drosophila EGF receptor (DER) locus. By constructing double mutant females for both brn and top, we have found that brn is required for determining the dorsal-ventral polarity of the ovarian follicle. However, embryos from mature brn eggs develop a neurogenic phenotype which can be zygotically rescued if a wild-type sperm fertilizes the egg. This is the first instance of a Drosophila gene required for determination of dorsal-ventral follicle cell fates that is not required for determination of embryonic dorsal-ventral cell fates. The temperature-sensitive period for brn dorsal-ventral patterning begins at the inception of vitellogenesis. The interaction between brn and DER is also required for at least two earlier follicle cell activities which are necessary to establish the ovarian follicle. Prefollicular cells fail to migrate between each oocyte/nurse cell complex, resulting in follicles with multiple sets of oocytes and nurse cells. brn and DER function is also required for establishing and/or maintaining a continuous follicular epithelium around each oocyte/nurse cell complex. These brn functions as well as the brn requirement for determination of dorsal-ventral polarity appear to be genetically separable functions of the brn locus. Genetic mosaic experiments show that brn is required in the germline during these processes whereas the DER is required in the follicle cells. We propose that brn may be part of a germline signaling pathway differentially regulating successive DER-dependent follicle cell activities of migration, division and/or adhesion and determination during oogenesis. These experiments indicate that brn is required in both tyrosine kinase and neurogenic intercellular signaling pathways. Moreover, the functions of brn in oogenesis are distinct from those of Notch and Delta, two other neurogenic loci that are known to be required for follicular development.

Enhanced expression of transforming growth factor beta 1 in the rat brain after a localized cerebral injury

It is becoming clear that transforming growth factor beta (TGF beta) may be a key factor regulating inflammatory and tissue specific wound responses. Because the formation of a glial-collagen scar at CNS lesion sites is thought to contribute to the pathology associated with penetrating CNS injuries, and because in the periphery TGF beta 1 stimulates fibroblast deposition of scar tissue, we used in situ hybridization and immunohistochemistry to investigate the effect of a defined cerebral lesion on the local expression of TGF beta 1. Induction of TGF beta 1 mRNA and protein is relatively diffuse in the neuropile around the margins of the lesion at 1, 2 and 3 days, but becomes localized to the region of the glial scar at 7 and 14 days. The signal intensity for TGF beta 1 mRNA and protein is maximal between 2 and 3 days and decreases between 7 and 14 days after lesion. The predominant cell types in the neuropile localizing TGF beta 1 mRNA and protein have the morphological characteristics of astrocytes, although macrophages are also detected. An induction of TGF beta 1 mRNA was also observed in endothelial cells of the meninges, hippocampal fissure and choroid plexus, at 2 and 3 days. However, this is dramatically reduced by 7 days and has disappeared by 14 days. These results suggest a role for TGF beta 1, not only in inflammation, but also in the tissue-specific glial scar formation that occurs in the CNS. Furthermore, they suggest a potential therapeutic use of TGF beta 1 antagonists in the CNS to help limit the pathogenesis associated with matrix deposition in the wound.

Vascular smooth muscle cell hypertrophy vs. hyperplasia. Autocrine transforming growth factor-beta 1 expression determines growth response to angiotensin II

Recent observations in our laboratory suggest that angiotensin II (Ang II) is a bifunctional vascular smooth muscle cell (VSMC) growth modulator capable of inducing hypertrophy or inhibiting mitogen-stimulated DNA synthesis. Because transforming growth factor-beta 1 (TGF beta 1) has similar bifunctional effects on VSMC growth, we hypothesized that autocrine production of TGF beta 1 may mediate the growth modulatory effects of Ang II. Indeed, this study demonstrates that Ang II induces a severalfold increase in TGF beta 1 mRNA levels within 4 h that is dependent on de novo protein synthesis and appears to be mediated by activation of protein kinase C (PKC). Ang II not only stimulates the synthesis of latent TGF beta 1, but also promotes its conversion to the biologically active form as measured by bioassay. The coincubation of VSMCs with Ang II and control IgG has no significant mitogenic effect. However, the co-administration of Ang II and the anti-TGF beta 1 antibody stimulates significantly DNA synthesis and cell proliferation. We conclude that: (a) Ang II induces increased TGF beta 1 gene expression via a PKC dependent pathway involving de novo protein synthesis; (b) Ang II promotes the conversion of latent TGF beta 1 to its biologically active form; (c) Ang II modulates VSMC growth by activating both proliferative and antiproliferative pathways; and (d) Autocrine active TGF beta 1 appears to be an important determinant of VSMC growth by hypertrophy or hyperplasia.

Enhanced production of plasminogen activator activity in human and murine keratinocytes by transforming growth factor-beta 1

Transforming growth factor-beta (TGF beta) is the most potent known inhibitor of keratinocyte growth. Pericellular proteolytic activity is usually high in proliferating and malignant cells and decreased in resting or growth-arrested cells. We have therefore analyzed the effects of TGF beta 1 on the production of plasminogen activator activity by normal human keratinocytes and a mouse keratinocyte cell line under serum-free conditions. The plasminogen activator activity of the culture medium was analyzed using caseinolysis-in-agar and zymography assays, immunoblotting, and Northern hybridization analysis for the plasminogen activators (PA) and PA inhibitor-1 (PAI-1). Alterations of radiolabeled polypeptides were observed in fluorograms of gels. It was found that like in human epidermoid carcinoma cells picomolar concentrations of TGF beta 1 (0.2-20 ng/ml) enhanced total plasminogen activator activity in both keratinocyte cell systems. Zymographic and immunoblotting analyses of the medium indicated that the activator was of the urokinase type (u-PA). Immunoprecipitation and Concanavalin A affinity chromatography of the culture medium indicated that the cells also started to produce PAI-1. Analysis of the pericellular matrix preparations of the keratinocytes showed that PAI-1 is deposited to the pericellular space. Evidently due to elevated u-PA activity PAI-1 was removed from the extracellular matrix more rapidly in TGF beta 1-treated cells than from control cultures. Northern hybridization analysis of human keratinocytes showed that TGF beta 1 rapidly elevated both u-PA and PAI-1 mRNA levels. Comparison of the temporal induction profiles indicated that the mRNA for u-PA increased more slowly but was more persistent than that of PAI-1. Actinomycin D inhibited the induction of both u-PA and PAI-1 mRNA, suggesting that the induction was due to increased transcription. The results suggest that enhanced plasminogen activator activity can be associated with growth inhibition also in nonmalignant cells like cultured human or murine keratinocytes.

Transforming growth factor-beta in disease: the dark side of tissue repair

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Cell density dependent effects of TGF-beta demonstrated by a plasminogen activator-based assay for TGF-beta

Transforming growth factor-beta 1 (TGF-beta 1) induces a decrease in plasminogen activator (PA) expression in confluent cultures of bovine aortic endothelial (BAE) cells. We describe an assay using the suppression of PA expression in confluent BAE cells by TGF-beta 1 which detects concentrations of the growth factor ranging from 5 to 200 pg/ml and has an ED50 of 15-20 pg/ml. The assay can be performed in 96-well plates and requires a minimum of 35 ul of solution per sample, thereby limiting the amount of reagents required and allowing many samples to be tested in a single assay. Here we demonstrate that the effect of TGF-beta 1 on PA expression in BAE cells depends on the length of time the cells are exposed to the growth factor and the density at which the cells are plated. In cells plated at a high density (3.5 x 10(5) cells/cm2), both 4 h and 24 h exposures to TGF-beta 1 suppress PA expression. However, with cells plated sparsely (3.5 x 10(4) cells/cm2), a 4 h exposure to TGF-beta 1 increases PA expression 2-fold, whereas a 24 h exposure results in an 85% inhibition of basal PA expression. The paradoxical stimulation of PA expression in cells at a sparse density upon 4 h exposure to TGF-beta 1 occurs in a dose-dependent manner with an ED50 of 15-20 pg/ml. This bifunctional response of PA production in cells exposed to TGF-beta 1 may have implications with regard to the role of TGF-beta 1 in angiogenesis.

Sequential induction of syndecan, tenascin and cell proliferation associated with mesenchymal cell condensation during early tooth development

The cell surface proteoglycan, syndecan, and the extracellular matrix glycoprotein, tenascin, are expressed in the mesenchyme during early development of many organs. We have studied the expression patterns of syndecan and tenascin during initiation of tooth development and in association with mesenchymal cell condensation and compared these with cell proliferation. Syndecan, tenascin and bromodeoxyuridine (BrdU) incorporation were localized by triple-labelling immunohistochemistry in serial sections of molar tooth germs of mouse embryos. Prior to formation of the epithelial tooth bud, syndecan accumulated in the mesenchymal cells which underlie the presumptive dental epithelium, but tenascin was not detected at this stage. Tenascin appeared during initiation of the epithelial down-growth at the lingual aspect of the tooth germ. During subsequent formation of the epithelial bud, at the late bud stage, syndecan and tenascin became exactly colocalized in the condensed mesenchyme which was clearly demarcated from other jaw mesenchyme. The expression of syndecan and tenascin was accompanied by rapid cell proliferation as indicated by marked BrdU incorporation. When development advanced to the cap stage, syndecan staining intensity in the dental papilla mesenchyme increased further whereas tenascin became reduced. In conclusion, the results demonstrate that the expression patterns of syndecan and tenascin overlap transiently during the period of mesenchymal cell condensation and that this is accompanied by cell proliferation. Syndecan and tenascin may play a role in growth control and in compartmentalization of the dental mesenchymal cells in the condensate.

Cytokine abnormalities in inflammatory arthritis

Cytokines are soluble molecules which control communication between cells of the immune and non-immune systems. Studies on their role in the pathogenesis of inflammatory arthritis have been increased with the discovery of new cytokines and the development of assays for their detection. Conditions such as rheumatoid arthritis are characterized by increased production of proinflammatory cytokines in association with reduced control by regulatory cytokines produced by T lymphocytes. The inadequate inhibition of proinflammatory cytokines by anti-inflammatory cytokines and other regulatory mechanisms contributes to this cytokine imbalance. This situation is responsible for the enhanced degradation, without sufficient repair activity. These results have provided the rationale for the use of cytokines as well as for drug targeting of the cytokine network in rheumatoid arthritis. This also includes the modulation of the cytokine network by targeting the level of the receptors as well as the effects and/or the responding cells.

Induction of swelling, synovial hyperplasia and cartilage proteoglycan loss upon intra-articular injection of transforming growth factor beta-2 in the rabbit

Transforming growth factor beta (TGF-beta) is a multifunctional homodimeric polypeptide with potent actions upon many target cells, including those of mesenchymal and haemopoietic lineage. The recent reports of high levels of the cytokine in rheumatoid synovium and synovial fluid, prompted this study into the effect of intra-articular injection of TGF beta-2 into rabbit knee-joints. Four daily injections of 1 microgram caused swelling, probably as a consequence of prostaglandin E2 production, synovial fibroblastic hyperplasia and a striking loss of femoral condyle proteoglycan. Using the polymerase chain reaction, no evidence could be obtained for the induction of interleukin-1 alpha gene expression in either synovial tissue or synovial fluid cells. These findings suggest that the TGF-beta present in the rheumatoid joint may contribute directly to the pathogenesis of rheumatoid arthritis.

Eosinophils in chronically inflamed human upper airway tissues express transforming growth factor beta 1 gene (TGF beta 1)

Transforming growth factor beta (TGF beta) is a multifunctional protein which has been suggested to play a central role in the pathogenesis of chronic inflammation and fibrosis. Nasal polyposis is a condition affecting the upper airways characterized by the presence of chronic inflammation and varying degrees of fibrosis. To examine the potential role of TGF beta in the pathogenesis of this condition, we investigated gene expression and cytokine production in nasal polyp tissues as well as in the normal nasal mucosa. By Northern blot analysis using a porcine TGF beta 1 cDNA probe, we detected TGF beta 1-specific mRNA in nasal polyp tissues, as well as in the tissue from a patient with allergic rhinitis, but not in the normal nasal mucosa. By the combination of tissue section staining with chromotrope 2R with in situ hybridization using the same TGF beta 1 probe, we found that approximately 50% of the eosinophils infiltrating the polyp tissue express the TGF beta 1 gene. In addition, immunohistochemical localization of TGF beta 1 was detected associated with extracellular matrix as well as in cells in the stroma. These results suggest that in nasal polyposis where eosinophils are the most prevalent inflammatory cell, TGF beta 1 synthesized by these cells may contribute to the structural abnormalities such as stromal fibrosis and basement membrane thickening which characterize this disease.

Localization of the cytoadhesin integrins in the human cornea. An immunohistochemical study using monoclonal antibodies

Cell-matrix interactions play a fundamental role in normal and pathological conditions. They can be mediated by the cytoadhesin subgroup of the integrin superfamily of adhesion molecules. Its members include the vitronectin receptor (VNR) and the platelet glycoprotein IIb/IIIa (GP IIb/IIIa). Both receptors are composed of an alpha-chain (alpha v and alpha IIb, respectively) coupled to a beta 3-chain. Using in situ immunohistochemistry and monoclonal antibodies, the authors studied the distribution of GP IIIa (common beta 3-chain), GP IIb/IIIa (alpha IIb-chain) and VNR (alpha v-chain) in normal and pathological corneal tissues. In the normal cornea, the limbal vascular endothelium was weakly alpha v-positive. Occasionally, faint and granular staining was seen in the epithelium. In the pathological samples, an upregulated expression of the alpha v-chain was noticed on the corneal epithelium as well as on fibroblasts and corneal endothelium. The alpha IIb and beta 3-chains were consistently absent. These data suggest that expression of the VNR-alpha v-chain in the human cornea is modulated by soluble factors released during inflammation and wound healing. Dissociation of expression of the alpha v and beta 3-chains suggests usage of an alternative beta-chain by the VNR-alpha v-chain.

Role of Kupffer cells in developing streptococcal cell wall granulomas. Streptococcal cell wall induction of inflammatory cytokines and mediators

Hepatic granulomas are induced by intraperitoneal injection of streptococcal cell walls (SCW) into Lewis rats. Kupffer cells rapidly clear SCW from the blood, and the authors examined Kupffer cells further for a role in SCW-hepatic inflammation. Isolated Kupffer cells cultured with SCW secreted high levels of tumor necrosis factor alpha (TNF alpha), interleukin-1 (IL-1), transforming growth factor beta (TGF beta), and prostaglandin E2 (PGE2). SCW transiently induced increased steady-state levels of IL-1 beta and TNF alpha mRNA; in contrast, constitutive expression of TGF beta 1 mRNA in Kupffer cells was not affected by SCW. Low concentrations of SCW induced the accumulation of intracellular IL-1 and TGF beta bioactivity, with intracellular IL-1 bioactivity remaining high through at least 72 hours of culture. Kupffer cells isolated 1, 7, and 21 days after SCW injection did not express IL-1 beta or TNF alpha mRNA greater than control levels and exhibited marked hyporesponsiveness to secondary in vitro stimulation with SCW or LPS. SCW transiently induces Kupffer cells to secrete a variety of soluble mediators that contribute to hepatic inflammation by inducing leukocyte recruitment and activation and fibroproliferation. The transient nature of the Kupffer cell response and the hyporesponsiveness to secondary stimulation may be a mechanism by which the hepatic inflammation is negatively regulated.

The Potential Role of Cytokines in the Pathogenesis of Systemic Sclerosis (Scleroderma)

Systemic sclerosis (scleroderma) is characterized by excessive fibroblastic activity taking place through mechanisms largely unknown. It has been speculated that soluble factors, collectively categorized as lymphokines or monokines, and released by inflammatory or other differentiated cells, may modulate fibroblast multiple functions including migration, chemotaxis and protein synthesis. Vascular endothelium itself, which is deeply injured in systemic sclerosis, is acting as a target for the action of cytokines and is an important producer of polypeptide mediators that contribute to the inflammatory reaction and to the establishment of fibrosis. Thus, interactions through soluble mediators between fibroblasts, endothelial cells and immunocompetent cells appear crucial for the development of systemic sclerosis lesions. The aim of the present study is to evaluate the available information on the role of cytokines and to discuss their potential influence in the pathogenesis of systemic sclerosis.

Hypoxia-ischemia induces transforming growth factor beta 1 mRNA in the infant rat brain

Transforming growth factor beta 1 (TGF beta 1) mRNA expression was examined after hypoxia-ischemia in rat brains using in situ hybridization. Twenty-one-day-old Wistar rats had unilateral ligation of the right carotid artery followed by either 15 or 90 min inhalational hypoxia. Fifteen min of hypoxia resulted in moderate damage with selective neuronal loss in cortical layer 3 and in the hippocampus of the ligated hemisphere. Seventy-two hours after hypoxia TGF beta 1 expression was markedly increased above control levels in those sites. Levels were normal after 120 h. Ninety min of hypoxia led to an infarction of the lateral cerebral cortex and hippocampus of the ligated hemisphere. One hour after hypoxia TGF beta 1 mRNA was expressed in the hippocampus of the damaged side. Seventy-two and 120 h after hypoxia, expressing cells were found throughout the cerebral cortex, piriform cortex, striatum, thalamus and hippocampus of the infarcted side. These data show that TGF beta 1 mRNA expression is induced after a hypoxic-ischemic insult in the brain. TGF beta 1 may be involved in post-asphyxial repair mechanisms.

Transforming growth factor beta (TGF-beta) in inflammation: a cause and a cure

As we continue to explore the biology of TGF-beta in the network of cells and mediators contributing to host defense, the mechanisms controlling whether the pro- or antiinflammatory effects of this peptide prevail will be unraveled. Understanding these basic mechanisms may offer new approaches for identifying agonists and/or antagonists and in which circumstances their use might be appropriate. The striking differences between local and systemic administration of this cytokine reaffirm that the functional consequences of any biologic mediator must be considered in context (9) and, furthermore, suggest avenues of therapeutic application (Table III). In summary, the central role of TGF-beta in normal and aberrant host defense has become indisputable.

Spontaneous increase of transforming growth factor beta production by bronchoalveolar mononuclear cells of patients with systemic autoimmune diseases affecting the lung

The spontaneous increase in the transcription of the transforming growth factor beta (TGF beta) gene in bronchoalveolar mononuclear cells of patients with autoimmune diseases affecting the lung has been shown by northern blot assay and a nuclear run on transcription assay. Transcription of the TGF beta gene in bronchoalveolar mononuclear cells of patients with autoimmune diseases affecting the lung was increased 10 times compared with normal healthy subjects or patients with bronchial asthma as controls. This observation, confirmed by protein data, suggests that TGF beta, a potent mitogen for fibroblasts, may be produced in bronchoalveolar mononuclear cells during an active immune response in such patients and may be involved in autoimmune related changes of the pathophysiology of cytokine networks when the lung is affected, such as in lung fibrosis.

Growth factors in retinal diseases: proliferative vitreoretinopathy, proliferative diabetic retinopathy, and retinal degeneration

The goal of this review is to present the current knowledge on specific growth factor involvement in posterior segment eye disease. Growth factors can be defined as multifunctional signals which modify cell growth or proliferation, alone or in concert, by binding to specific cell surface receptors. Their biological effects on cells include cell adhesion, migration, survival, differentiation, extracellular matrix secretion, protease and protease inhibitor release, production of other growth activities, and angiogenesis. Growth factors couple the cell to the microenvironment. As some growth factors are soluble mediators of wound repair and angiogenesis, it seems possible that proliferative vitreoretinopathy and proliferative diabetic retinopathy are caused or aggravated by these factors. Other factors act as survival factors and can possibly prevent retinal degeneration. The multifunctional nature of growth factors makes it probable that practical uses will be found for these agents in the future.

Isolation and sequence of the granulin precursor cDNA from human bone marrow reveals tandem cysteine-rich granulin domains

Granulins are candidate growth factors recently discovered in human and rat inflammatory leukocytes and bone marrow. Two granulin homologs, epithelin 1 and 2, occur in the rat kidney. Epithelin 1, which is probably identical to rat leukocyte granulin, exhibits proliferative and antiproliferative effects on epithelial cells in vitro. Here we show by cDNA analysis that the prepropeptide for the human granulins is a 593-residue glycoprotein, containing seven tandem repeats of the 12-cysteine granulin domain. By Northern blot analysis, gene expression was seen in myelogenous leukemic cell lines of promonocytic, promyelocytic, and proerythroid lineage, in fibroblasts and was seen very strongly in epithelial cell lines. Some epithelial cell lines respond to the mature peptide and express the gene. Among tissues examined, the kidney had the highest levels of granulin mRNA.

Kupffer cells express type I TGF-beta receptors, migrate to TGF-beta and participate in streptococcal cell wall induced hepatic granuloma formation

Intraperitoneal injection of Group A streptococcal cell wall (SCW) fragments into female Lewis rats results in the induction of an acute hepatic inflammation that progresses to granulomatous lesions. Kupffer cells have been shown to rapidly clear circulating SCW which triggers production of TGF-beta. In this study, we examined Kupffer cells for the expression of TGF-beta receptors to determine if these cells might be modulated in an autocrine/paracrine fashion by TGF-beta during SCW-hepatic inflammation. By receptor crosslinking and subsequent SDS-PAGE analysis we demonstrate that Kupffer cells express Type I TGF-beta receptors, but not Types II and III. Scatchard analysis indicated a receptor density of approximately 1100 receptors per cell. Functionally, TGF-beta was found to be chemotactic for Kupffer cells in vitro and this chemotactic response was higher in cells isolated from rats 1-21 days post SCW-injection. Although TGF-beta 1 mRNA is constitutively expressed by Kupffer cells, in vitro stimulation of the cultures with purified TGF-beta augments the expression of TGF-beta 1 mRNA and protein synthesis suggesting autocrine/paracrine regulation. These results indicate that TGF beta secreted by Kupffer cells during SCW-induced hepatic inflammation may amplify its own expression and regulate Kupffer cell functions relevant to the formation of granulomatous lesions within the liver.

RGD-albumin conjugate: expression of tissue regeneration activity

Albumin conjugated with Arg-Gly-Asp (RGD) has cellular adhesive activity comparable to that of fibronectin in vitro. This study examined whether RGD-albumin conjugate (RGD-ALB) can promote soft tissue ingrowth into a porous matrix in vivo. Polyurethane sponges with 150-500 microns pore size adsorbed with RGD-ALB, fibronectin and albumin were implanted in the subcutaneous tissue of rats. The RGD-ALB-adsorbed sponge exhibited tissue ingrowth comparable to that of the fibronectin-adsorbed sponge at the early period of implantation. On the other hand, the tissue ingrowth was markedly retarded for non-adsorbed and albumin-adsorbed sponges. The enhanced tissue ingrowth found for RGD-ALB and fibronectin was deduced to be mainly a result of its cell-adhesion activity. It is concluded that RGD-ALB exhibits tissue ingrowth-promoting activity at the initial stage of wound healing as effectively as fibronectin.

Effect of transforming growth factor beta on postoperative adhesion formation and intact peritoneum

Transforming growth factor beta (TGF beta) is an extremely potent chemoattractant for macrophages, mononuclear leukocytes, and fibroblasts. It also acts as a potent stimulant for collagen and fibronectin synthesis and inhibits epithelial cell growth. TGF beta plays an important role in healing many types of wounds, but its role in peritoneal adhesion formation is not known. These studies were performed to determine if TGF beta could affect postoperative wound healing in a rat model. In the first experiment, 20 rats were divided into two groups and received either 2 micrograms TGF beta or control diluent IP daily for 5 days after surgical injury to the uterine horns. The severity of the adhesions were graded 2 weeks postoperatively using a score of 0-3. The TGF beta group showed a higher adhesion score at 2 weeks compared to control, 2.9 +/- 0.34 and 1.6 +/- 0.61, respectively (P less than 0.001). On H&E stained sections of the adhesions, there was an increase in the number of both inflammatory cells and fibroblasts in the TGF beta-treated animals. A comparison trial of bone-derived TGF beta (a gift from Collagen Corporation, Palo Alto, CA) versus recombinant TGF beta (a gift from Oncogen, Seattle, WA) versus control using the same protocol as above showed that both sources of TGF beta were more effective in promoting postoperative adhesions when compared to controls, and there was no difference between TGF beta groups, 3.0 +/- 0 for both TGF beta groups, and 2.2 +/- 0.91 for control (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of transforming growth factor beta and basic fibroblast growth factor on steroid-impaired healing intestinal wounds

A longitudinal intestinal wound model in the pig was used to assess the effect of parenteral steroids (betamethasone 12 mg 50 kg-1 intramuscularly twice daily) on breaking load. Steroid treatment significantly decreased the breaking load of wounds in the ileum and colon in comparison with wounds from saline-treated animals. In a further group of animals receiving steroids, paired longitudinal wounds were constructed. One wound of a pair was treated with a local application of transforming growth factor beta (TGF-beta) (5 micrograms per wound) or basic fibroblast growth factor (5 micrograms per wound) in a collagen suspension. The other wound was treated with a collagen suspension alone. Ileal wounds treated with TGF-beta were significantly stronger than collagen-treated controls at 7 days. The steroid-induced impairment of breaking load in intestinal wounds is partially reversed by a local application of TGF-beta in a collagen suspension at the time of surgery.

Migration of a human keratinocyte cell line (HACAT) to interstitial collagen type I is mediated by the alpha 2 beta 1-integrin receptor

The migratory response of the human keratinocyte cell line HaCaT to collagen type I and the molecular mechanism underlying collagen-mediated migration have been analyzed. The migratory response of HaCaT cells to collagen type I consisted of a dose-dependent migration to insoluble step gradients of substratum-bound collagen (haptotaxis) and to gradients of soluble collagen (chemotaxis). Checkerboard analysis demonstrated a minor chemokinetic component. Denatured collagen type I was less chemoattractive than the native triple-helical form. Pre-treatment of cells with 25-250 micrograms/ml of synthetic peptides containing the fibronectin cell-recognition sequence RGD (Arg-Gly-Asp) resulted in a concentration-dependent inhibition of fibronectin-mediated chemotaxis, whereas chemotaxis to collagen was not affected. We then investigated the role of VLA/collagen-receptors for collagen type I-induced chemotaxis. Monoclonal antibody (MoAb) 5E8, which selectively blocks function of the alpha 2 subunit of the VLA-2/collagen receptor, dose-dependently inhibited the chemotactic response of HaCaT cells to collagen. This effect was specific for collagen-mediated chemotaxis because the chemotactic response to fibronectin remained unaffected. In contrast, a function blocking MoAb directed to the alpha 3 subunit of the coexpressed VLA-3 receptor, which is also capable of binding collagen, had no effect. However, function blocking MoAb directed to the beta 1-chain of integrins completely inhibited chemotaxis to collagen type I. Based on our results, we propose that the chemotactic migration of the human keratinocyte cell line (HaCaT) to collagen type I is specifically mediated by the RGD independent VLA-2/collagen receptor (alpha 2 beta 1) of the integrin family.

Sequence of structural changes and elastin peptide release during vascular remodelling in sheep with chronic pulmonary hypertension induced by air embolization

The progression of structural changes in the pulmonary arterial bed were followed in a model of chronic pulmonary hypertension. Chronically instrumented awake sheep received continuous air embolization for 0 (controls), 1, 4, 8, or 12 days (n = 5-6/group). After the period of embolization, the lungs were removed, the pulmonary arteries were distended with barium-gelatin, and the lungs were fixed via the airways with formal-saline. Quantitative techniques were applied to sections from random blocks from the lungs of each animal. One day of embolization resulted in granulocyte sequestration in the lung interstitium and in small vessels; additionally, intraalveolar and perivascular edema was present. By 4 days, increased medial thickness, appearance of muscle in smaller arteries than normal (e.g., muscular arteries at alveolar duct level: control = 1.2 +/- 1.2%; day 4 = 22.7 +/- 7.7) and reduction in number of barium-filled intraacinar arteries was found. The arterial changes progressed in severity to day 8 and were similar at day 12. Since arterial remodelling involves increased elastin deposition, the concentration of elastin peptides was measured in lung lymph. Increased flux of elastin peptides was apparent from day 2 of embolization and continued to increase to a level 20 x baseline by day 12 (baseline 351 +/- 86 micrograms/15 min; day 12 = 6338 +/- 2999). Comparison of the onset of the structural changes with previous findings shows that the arterial remodelling parallels the onset of sustained pulmonary hypertension. The increase in lung-lymph elastin peptides by day 2 provides evidence that vascular remodelling is initiated before day 4 of embolization. The early sequestration of granulocytes and appearance of edema suggest that these may be part of the trigger to the development of the structural changes.

Pathogenesis of interstitial fibrosis in chronic purine aminonucleoside nephrosis

A cellular and molecular approach was used to gain new insight into the pathogenesis of interstitial fibrosis in chronic purine aminonucleoside nephrosis (PAN) nephrosis. Thirty experimental rats (PAN rats) were given 15 mg/100 g body wt of i.p. PAN at time 0, followed by 4.3 mg/100 g body wt i.p. on days 20, 27 and 34; 25 control rats received i.p. saline at the same time intervals. All rats had a right unilateral nephrectomy within the first four days. Groups of control and PAN rats were killed at 21, 37, 52, 72 and 91 days. Renal sections were studied by immunofluorescence to quantitate interstitial macrophages, T lymphocytes and fibroblasts, and to characterize the deposition of the extracellular matrix (ECM) proteins (collagens I, III and IV, fibronectin and laminin) and the tissue inhibitor of the metalloproteinases (TIMP). Steady state concentrations of mRNA from the whole kidney for these ECM proteins, the metalloproteinases, TIMP, and transforming growth factor beta (TGF-beta 1) were quantitated by Northern blot analysis. Significant increases in the number of interstitial macrophages and T lymphocytes were found in the PAN rat groups compared to that in controls. All ECM proteins examined were quantitatively increased in the tubulo-interstitium of PAN rats. The pattern of distribution of some ECM proteins was also modified in experimental animals. TIMP was increased in the interstitium of PAN rats; at later times, TIMP was most prominent in sclerotic regions of the glomeruli and in tubular protein droplets. Northern blot analysis revealed increased steady-state mRNA levels for components of each of the ECM proteins, no change for the metalloproteinases--stromelysin or collagenase--and a marked increase for TIMP and TGF-beta 1 in PAN animals. The results of this study suggest that the diffuse interstitial fibrosis found in chronic PAN nephrosis results from both increased production of ECM proteins and decreased matrix degradation.

The role of growth factors in the embryogenesis and differentiation of the eye

The vertebrate eye is composed of a variety of tissues that, embryonically, have their derivation from surface ectoderm, neural ectoderm, neural crest, and mesodermal mesenchyme. During development, these different types of cells are subjected to complex processes of induction and suppressive interactions that bring about their final differentiation and arrangement in the fully formed eye. With the changing concept of ocular development, we present a new perspective on the control of morphogenesis at the cellular and molecular levels by growth factors that include fibroblast growth factors, epidermal growth factor, nerve growth factor, platelet-derived growth factor, transforming growth factors, mesodermal growth factors, transferrin, tumor necrosis factor, neuronotrophic factors, angiogenic factors, and antiangiogenic factors. Growth factors, especially transforming growth factor-beta, have a crucial role in directing the migration and developmental patterns of the cranial neural-crest cells that contribute extensively to the structures of the eye. Some growth factors also exert an effect on the developing ocular tissues by influencing the synthesis and degradation of the extracellular matrix. The mRNAs for the growth factors that are involved in the earliest aspects of the growth and differentiation of the fertilized egg are supplied from maternal sources until embryonic tissues are able to synthesize them. Subsequently, the developing eye tissues are exposed to both endogenous and exogenous growth factors that are derived from nonocular tissues as well as from embryonic fluids and the systemic circulation. The early interaction between the surface head ectoderm and the underlying chordamesoderm confers a lens-forming bias on the ectoderm; later, the optic vesicle elicits the final phase of determination and enhances differentiation by the lens. After the blood-ocular barrier is established, the internal milieu of the eye is controlled by the interactions among the intraocular tissues; only those growth factors that selectively cross the barrier or that are synthesized by the ocular tissues can influence further development and differentiation of the cells. An understanding of the tissue interactions that are regulated by growth factors could clarify the precise mechanism of normal and abnormal ocular development.

Transforming growth factor-beta 1 in rheumatoid synovial membrane and cartilage/pannus junction

Transforming growth factor (TGF)-beta has been shown to promote tissue repair and have immunosuppressive actions, and has been proposed to have a role in rheumatoid arthritis (RA). Using immunohistochemical techniques with rabbit F(ab')2 antibodies raised against recombinant human TGF-beta 1, we have detected TGF-beta 1 in the synovial tissue and cartilage/pannus junction (CPJ) from 18/18 patients with RA. TGF-beta 1 was found predominantly in the thickened synovial lining layer in RA, but also detected in a perivascular pattern in the synovial interstitium as well as in occasional cells in the lymphoid aggregates. At the CPJ it was found both in cells at the distinct junction as well as in the transitional region of the diffuse fibroblastic zone. The cells staining for TGF-beta 1 were identified by double immunofluorescence staining as being from the monocyte/macrophage series as well as the type B synovial lining cells. TGF-beta 1 was also detected in the synovial membrane sections from 4/4 patients with systemic lupus erythematosus/mixed connective tissue disease and 5/8 patients with osteoarthritis, in a similar distribution to that seen in RA, and in the lining layer of 1/7 normal synovial membranes. These results add to histological evidence confirming that TGF-beta 1 is present in RA synovial cells and those from other arthritides. The distributions of TGF-beta 1 in RA synovial membrane reflects its known actions, as it can be detected at the CPJ, where it could induce repair, and close to activated cells upon which it may exert an immunosuppressive action.

Spontaneous activation of transforming growth factor-beta gene transcription in broncho-alveolar mononuclear cells of individuals with systemic autoimmune diseases with lung involvement

The spontaneous elevation of the transcription of the transforming growth factor-beta (TGF-beta) gene in broncho-alveolar mononuclear cells (BMC) of individuals with autoimmune diseases with lung involvement, by nuclear run-on transcription assay, is shown in this study. In quantification analysis of TGF-beta gene transcription, we found more than 10 times the enhanced transcription of the TGF-beta gene in BMC of individuals with autoimmune diseases with lung involvement, in comparison to normal healthy subjects or patients with bronchial asthma used as controls. Our observation suggests that TGF-beta, a potent mitogen for fibroblasts, may be produced in BMC during an active immune response in individuals with systemic autoimmune diseases with lung involvement, and may be involved in autoimmune-related pathophysiological changes of cytokine networks in lung involvement such as lung fibrosis.

Kupffer cells from carbon tetrachloride-injured rat livers produce chemotactic factors for fibroblasts and monocytes: the role of tumor necrosis factor-alpha

Conditioned media from cultured Kupffer and mononuclear macrophagic cells obtained 48 hr after CCl4 administration to rats contains chemotactic factors for human skin fibroblasts and human monocytes. The chemotactic mediator for fibroblasts was approximately 17 kD and was more prominent at early stages of culture. It induced a dose-dependent chemotactic response in fibroblasts. Although the conditioned medium from cultured Kupffer cells of normal rats also contained detectable biological activity, it was significantly less than that in conditioned medium from cultured Kupffer cells from CCl4-treated rats. The activity obtained after purification by high-performance liquid chromatography was completely ablated by incubation with tumor necrosis factor-alpha antibody. Transforming growth factor-beta antibody diminished biological activity by 20%. Human recombinant tumor necrosis factor-alpha and transforming growth factor-beta used in the assay as control showed significant chemotactic activity. The chemotactic activity present in whole normal conditioned medium was only present after 24 and 48 hr of culture. Furthermore, this activity was not neutralized by human recombinant tumor necrosis factor-alpha or transforming growth factor-beta antibodies. Incubation of whole 6-hr conditioned medium with human recombinant tumor necrosis factor-alpha and transforming growth factor-beta antibodies demonstrated and confirmed that tumor necrosis factor-alpha plays a major role in inducing the chemotactic response. On acidification of this supernatant, we found a notable increase in the biological response that could be neutralized by transforming growth factor-beta antibody. Thus tumor necrosis factor-alpha and transforming growth factor-beta may sequentially provide important signals for fibroblast and monocyte recruitment in vivo at initial stages of liver injury.

TGF-beta-like activity produced during regression of exacerbations in multiple sclerosis

Samples representative of different stages of disease from a longitudinal study of multiple sclerosis patients were tested in the anchorage-independent growth assay for TGF-beta and an increased activity was detected in the supernatants from 2-day blood cell cultures from patients with active disease compared to patients without active disease and healthy donors. Within the group of patients with active disease, the TGF-beta like activity was significantly increased in the subgroup of patients tested during the period of regression of the symptoms where it appeared in 86.9% of the samples. These results suggest that TGF-beta or a TGF-beta like factor may play a role in regeneration processes in multiple sclerosis.

Peptide growth factors and wound healing

Growth factors and cytokines are important signal transducers in wound microenvironments. Experimental data are accumulating rapidly which demonstrate their ability to influence populations of polymorphs and macrophages to migrate to the wound, subsequently to be replaced by synthetic cells which produce collagen and matrix; these events are controlled sequentially at cell receptor level by a variety of locally delivered (paracrine and autocrine) peptides. Preliminary results from clinical trials using recombinant human growth factors to improve cutaneous healing are encouraging. Current research aims to produce growth preparations which can be applied to a wound to accelerate healing.

Cloning of a growth arrest-specific and transforming growth factor beta-regulated gene, TI 1, from an epithelial cell line

By cDNA cloning and differential screening, five genes that are regulated by transforming growth factor beta (TGF beta) in mink lung epithelial cells were identified. A novel membrane protein gene, TI 1, was identified which was downregulated by TGF beta and serum in quiescent cells. In actively growing cells, the TI 1 gene is rapidly and transiently induced by TGF beta, and it is overexpressed in the presence of protein synthesis inhibitors. It appears to be related to a family of transmembrane glycoproteins that are expressed on lymphocytes and tumor cells. The four other genes were all induced by TGF beta and correspond to the genes of collagen alpha type I, fibronectin, plasminogen activator inhibitor 1, and the monocyte chemotactic cell-activating factor (JE gene) previously shown to be TGF beta regulated.

Effect of topical recombinant TGF-beta on healing of partial thickness injuries

Peptide growth factors produced by platelets, macrophages, epidermal, and dermal cells may play key roles in regulating healing of partial-thickness skin wounds. We examined the effects of recombinant transforming growth factor beta (TGF-beta) on cultures of epidermal and dermal cells in vitro and on healing of partial-thickness injuries in vivo. Increasing concentrations of TGF-beta (0.1, 1, and 10 ng/ml) progressively inhibited serum-stimulated DNA synthesis by up to 95% in cultures of adult human keratinocytes during 48 hr of exposure to TGF-beta. In contrast, TGF-beta (10 and 100 ng/ml) in serum-free media stimulated DNA synthesis by up to 80% compared to serum-free control cultures of adult human dermal fibroblasts. To evaluate the effects of TGF-beta on healing of partial-thickness injuries in vivo, wounds (20 x 20 x 0.6 mm) were created on the dorsal thoracolumbar region of adult pigs by an electrokeratome and were treated daily for 5 days after injury with vehicle or vehicle containing 0.1 or 1 microgram/ml TGF-beta and covered with occlusive dressing. Computerized planimetry of wound photographs demonstrated that TGF-beta treatment stimulated statistically significantly increases in the area of regenerated epidermis compared to wounds treated with saline vehicle on Days 3, 4, 5, and 7 after injury probably due to TGF-beta increasing the rate of epidermal cell migration. In addition, morphometry of biopsy specimens showed that TGF-beta treatment stimulated statistically significant increases in the cross-sectional depths of regenerated dermis compared to wounds treated with saline or Silvadene vehicles on Days 5, 6, and 8 after injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning of a growth arrest-specific and transforming growth factor beta-regulated gene, TI 1, from an epithelial cell line

By cDNA cloning and differential screening, five genes that are regulated by transforming growth factor beta (TGF beta) in mink lung epithelial cells were identified. A novel membrane protein gene, TI 1, was identified which was downregulated by TGF beta and serum in quiescent cells. In actively growing cells, the TI 1 gene is rapidly and transiently induced by TGF beta, and it is overexpressed in the presence of protein synthesis inhibitors. It appears to be related to a family of transmembrane glycoproteins that are expressed on lymphocytes and tumor cells. The four other genes were all induced by TGF beta and correspond to the genes of collagen alpha type I, fibronectin, plasminogen activator inhibitor 1, and the monocyte chemotactic cell-activating factor (JE gene) previously shown to be TGF beta regulated.

Transforming growth factor-beta improves healing of radiation-impaired wounds

Exogenously applied TGF-beta 1 has been shown to increase wound strength in incisional wounds early in the healing process. An impaired wound healing model was first established in guinea pigs by isolating flaps of skin and irradiating the flaps to 15 Gray in one fraction using a 4-MeV linear accelerator. Incisions made 2 d after irradiation were excised 7 d later, and showed decreased linear wound bursting strength (WBS) as compared to non-irradiated control wounds on the contralateral side of each animal (p = 0.001). The effect of TGF-beta on healing of radiation-impaired wounds was studied using this model. Skin on both left and right sides of guinea pigs was irradiated as above. A linear incision was made in each side. Collagen with either 1, 5, or 20 micrograms of TGF-beta was applied to one side prior to closure with staples, whereas the contralateral side received saline in collagen. Wounds given either 1 or 5 micrograms of TGF-beta were found to be stronger than controls at 7 d (p less than 0.05), whereas those receiving the higher 20-micrograms dose were weaker than controls (p less than 0.05). Thus, TGF-beta in lower doses improved healing at 7 d but very large amounts of the growth factor actually impaired healing. In situ hybridization done on wound samples showed increased type I collagen gene expression by fibroblasts in wounds treated with 1 micrograms TGF-beta over control wounds. These results indicate that TGF-beta improved wound healing as demonstrated by increased WBS. This improvement is accompanied by an up-regulation of collagen gene expression by resident fibroblasts.

Mesothelial cells produce a chemoattractant for lung fibroblasts: role of fibronectin

Pleural fibrosis may complicate several types of non-exudative pleural injury. Although the pathogenesis of such lesions is poorly understood, it is conceivable that mesothelial cells may recruit fibroblasts to sites of pleural damage. In order to test this possibility, conditioned medium from cultured rat mesothelial cells was tested for chemoattractant activity towards RL-87 rat lung fibroblasts. For this purpose, rat pleural or pericardial mesothelial cells were maintained in vitro for 6 to 96 h. Conditioned medium from each source was obtained at defined culture times and tested for chemotactic activity in a 48-well microchemotaxis assembly. A progressive, time-dependent increase in fibroblast chemoattractant activity was detected in both pleural and pericardial mesothelial cell conditioned medium samples. This effect was maximal in 96-h cultures. Checkerboard analysis revealed that the conditioned medium was truly chemotactic for lung fibroblasts. Characterization of the chemoattractant demonstrated that it was a nondialyzable (greater than 16 kD), thermolabile (100 degrees C for 15 min), acid-stable (pH 2.5), trypsin-sensitive, and pepsin-sensitive protein. The chemotaxin was shown to be fibronectin, since activity was abolished, in a dose-dependent manner, by treatment with anti-rat fibronectin antiserum as well as by passage through a gelatin agarose affinity column. This product consisted of two bands on sodium dodecyl sulfate polyacrylamide gel electrophoresis of apparent molecular masses 250 and 220 kD. The secretion of a mesothelial cell-derived fibroblast chemoattractant may play a role in the response of the pleura to injury and in the pathogenesis of pleural fibrosis.

In vivo induction of bone by recombinant human transforming growth factor beta 1

A single application of recombinant human transforming growth factor beta 1 (rhTGF-beta 1) adjacent to cartilage was found to induce bone formation in rabbit ear full-thickness skin wounds. At doses that optimally promote soft tissue healing, 25-100 ng rhTGF-beta 1 per wound caused osseous tissue formation starting 21 days after wounding to reach a peak incidence and area of bone formation at day 42. Bone formation was followed by active remodeling, resulting in lower incidence and area of bone formation at days 56 and 70. The early phase of bone formation was located overlying the cartilage and involved perichondrial cells that appeared to differentiate directly into osteoblasts forming bone matrix without a cartilage precursor. Cartilage was replaced with bone at later time points. rhTGF-beta 1 was able to increase the ratio of osteoblasts to osteoclasts lining the trabecular surface of bone and thus increase the net amount of bone formation. The present studies suggest a potential therapeutic role for rhTGF-beta 1 in hard tissue repair.

Transforming growth factor beta 1, a potent chemoattractant for human neutrophils, bypasses classic signal-transduction pathways

Transforming growth factor beta 1 (TGF-beta 1), a homodimeric polypeptide (Mr 25,000), derives from inflammatory cells and acts as a chemoattractant for monocytes and fibroblasts. We report here that TGF-beta 1 is also the most potent chemoattractant yet described for human peripheral blood neutrophils. Recombinant TGF-beta 1 elicited dose-dependent directed migration of neutrophils under agarose that was inhibited in the presence of a neutralizing antibody to TGF-beta 1. Maximal chemotaxis was evoked by TGF-beta 1 at femtomolar concentrations, whereas conventional chemoattractants act at nanomolar concentrations: on a molar basis, TGF-beta 1 was 150,000 times more potent than fMet-Leu-Phe. In contrast, TGF-beta 1 provoked neither exocytosis nor the production of superoxide by neutrophils. We further analyzed the mechanism by which TGF-beta 1 elicits chemotaxis (GTPase activity, [Ca2+], and actin polymerization). In contrast to the conventional chemoattractant fMet-Leu-Phe, TGF-beta neither activated classic heterotrimeric guanine nucleotide-binding proteins nor provoked global mobilization of intracellular Ca2+. Chemoattraction by both fMet-Leu-Phe and TGF-beta 1 was inhibited by cycloheximide and actinomycin D. Moreover, chemotaxis in response to TGF-beta 1 was associated with the polymerization of actin. The selectivity and potency of TGF-beta 1 as a chemoattractant suggest that it elicits directed cell migration by means of a pathway that depends not on classic intracellular signals but on protein synthesis.

Increased production and immunohistochemical localization of transforming growth factor-beta in idiopathic pulmonary fibrosis

Transforming growth factor-beta (TGF-beta) can regulate cell growth and differentiation as well as production of extracellular matrix proteins. Elevated production of TGF-beta has been associated with human and rodent chronic inflammatory and fibrotic diseases. Using immunohistochemical staining, we have examined lung sections of patients with advanced idiopathic pulmonary fibrosis (IPF), a disease characterized by chronic inflammation and fibrosis and demonstrated a marked and consistent increase in TGF-beta production in epithelial cells and macrophages when compared to patients with nonspecific inflammation and those with no inflammation or fibrosis. In patients with advanced IPF, intracellular staining with anti-LC (1-30) TGF-beta antibody was seen prominently in bronchiolar epithelial cells. In addition, epithelial cells of honeycomb cysts and hyperplastic type II pneumocytes stained intensely. Anti-CC (1-30) TGF-beta antibody, which reacts with extracellular TGF-beta, was localized in the lamina propria of bronchioles and in subepithelial regions of honeycomb cysts in areas of dense fibroconnective tissue deposition. The close association of subepithelial TGF-beta to the intracellular form in advanced IPF suggests that TGF-beta was produced and secreted primarily by epithelial cells. Because of the well-known effects of TGF-beta on extracellular matrix formation and on epithelial cell differentiation, the increased production of TGF-beta in advanced IPF may be pathogenic to the pulmonary fibrotic and regenerative responses seen in this disease.

Immunologic aspects of pneumoconiosis

This review summarizes recent research bearing on the role played by cells of the immune system in the development of pneumoconiosis. Findings related to the cellular and humoral immune responses to silica and asbestos are highlighted. Experimental results from humans and animal models are integrated into our current understandings of cellular and cytokine-mediated pathways leading to the generation of immune responses that may contribute to fibrogenesis and fibrosis. Potential mechanisms leading to the generation of an immune response by particulates are discussed, together with the indirect effects of particulates on fibroblasts by way of the cytokine network in the lung. Finally, suggestions are given for future research to help further elucidate the relationships between the cellular components of the immune system of the lung and the fibroblast that lead to fibrosis.

Fibroblast chemotaxis induction by human recombinant interleukin-4. Identification by synthetic peptide analysis of two chemotactic domains residing in amino acid sequences 70-88 and 89-122

Interleukin-4 is a T lymphocyte- and mast cell-derived cytokine with pleiotropic properties with biological effects on a variety of target cells including B and T lymphocytes, macrophages, hematopoietic cells, mast cells, and fibroblasts. In addition to the proliferation effect of IL-4 on fibroblasts, which has been previously described, in this report the chemotactic properties of IL-4 for fibroblasts is described. Human recombinant IL-4 induced the chemotactic migration of dermal fibroblasts in vitro in modified Boyden-type chambers at concentrations between 10(-12) and 10(-11) M. The chemotactic activity of IL-4 was neutralized by anti-human recombinant IL-4 IgG antibodies. Oligopeptides representing the complete deduced amino acid sequence of human IL-4 were synthesized by the Merrifield technique and tested for their ability to induce fibroblast chemotaxis. Two peptides representing residues 70-88 and 89-122 induced fibroblast migration. Peptide 70-88 was the more potent of the two causing chemotaxis of fibroblasts at 10(-8)-10(-6) M while peptide 89-129 induced migration at 10(-7)-10(-5) M. Although the mechanism by which IL-4 and these two peptides induce fibroblast chemotaxis is unknown, each of these three compounds were able to chemotactically desensitize fibroblasts to the chemotactic effects of the other two but not to a structurally unrelated chemotactic cytokine, transforming growth factor beta-1. These studies suggest that IL-4 might function in vivo to induce the accumulation of fibroblasts at sites of tissue injury, inflammatory and immune reactions in which T lymphocytes and mast cells participate.

Transforming growth factor beta 1 (TGF-beta 1) induced neutrophil recruitment to synovial tissues: implications for TGF-beta-driven synovial inflammation and hyperplasia

We have studied the consequences of introducing human recombinant transforming growth factor beta 1 (hrTGF-beta 1) into synovial tissue of the rat, to begin to better understand the significance of the fact that biologically active TGF-beta is found in human arthritic synovial effusions. Within 4-6 h after the intra-articular injection of 1 microgram of hrTGF-beta 1 into rat knee joints, extensive recruitment of polymorphonuclear leukocytes (PMNs) was observed. Cytochemistry and high resolution histological techniques were used to quantitate the influx of PMNs, which peaked 6 h post-injection. In a Boyden chamber assay, hrTGF-beta 1 at 1-10 fg/ml elicited a chemotactic response from PMNs greater in magnitude than that evoked by FMLP, establishing that TGF-beta 1 is an effective chemotactic agent for PMNs in vitro as well as in vivo. That PMNs may represent an important source of TGF-beta in inflammatory infiltrates was strongly suggested by a demonstration that stored TGF-beta 1 was secreted during phorbol myristate acetate-stimulated degranulation in vitro. Acid/ethanol extracts of human PMNs assayed by ELISA contained an average of 355 ng of TGF/beta 1 per 10(9) cells potentially available for secretion during degranulation of PMNs. [3H]Thymidine incorporation in vivo and autoradiography of tissue sections revealed that widespread cell proliferation was triggered by TGF-beta 1 injection. Synovial lining cells and cells located deep within the subsynovial connective tissue were identified as sources of at least some of the new cells that contribute to TGF-beta 1-induced hyperplasia. Our results demonstrate that TGF-beta is capable of exerting pathogenic effects on synovial tissue and that PMNs may represent a significant source of the TGF-beta present in synovial effusions.

Inhibiting and stimulating effects of TGF-beta 1 on osteoclastic bone resorption in fetal mouse bone organ cultures

The effects of TGF-beta 1 on osteoclastic resorption of fetal mouse calvaria and long bones at various stages of development was studied in organ culture. In resorbing calvariae and long bones with an established marrow cavity TGF-beta 1 (4-10 ng/ml) had a stimulating effect on 45Ca release that was partially inhibited by indomethacin. In primitive long bones, however, which were explanted before osteoclast invasion and excavation of a marrow cavity had started, TGF-beta 1 (1-4 ng/ml) inhibited 45Ca release by an indomethacin-insensitive mechanism. Histomorphometry of long bones after staining for tartrate-resistant acid phosphatase (TRAP) revealed that TGF-beta 1 treatment inhibited the migration of TRAP-positive cells from periosteum to developing marrow cavity and inhibited cell fusion. However, the formation of (mononuclear) TRAP-positive cells in the periosteum-perichondrium was strongly enhanced. These data suggest that TGF-beta 1 modulates various steps in the cascade of osteoclast development, recruitment, and activation in different ways, involving both prostaglandin-mediated and prostaglandin-independent pathways. Therefore the net effect of exogenous TGF-beta 1 on osteoclastic resorption in bone organ cultures depends on the relative prevalence of osteoclast progenitors, precursors, and mature osteoclasts in the tissue under study.

Glomerular mesangial cell migration. Response to platelet secretory products

Glomerular mesangial cells migrate in response to platelet-derived growth factor (PDGF), but to date these cells have not been examined for migratory behavior in response to other platelet secretory products. Because migration might provide an additional mode of cell redistribution and local mesangial hypercellularity in certain forms of glomerular disease, we examined, in vitro, the potential of isolated rat mesangial cells to migrate toward gradients of platelet releasate and selected platelet secretory proteins. Chemotaxis assays were performed in two compartment blind well chambers, each compartment separated by a porous membrane. Releasate of activated platelets was added in incremental concentrations (25, 50, and 100 micrograms/ml) to lower compartments, and mesangial cells were placed in upper compartments. The chambers were then incubated at 37 degrees C for 4 hours. Mesangial cell migration through the membranes was quantitated by scanning electron microscopy. Mesangial cells migrated toward platelet releasate in a linear dose-response, achieving cell numbers of approximately 40 times those of controls. Examination of specific platelet alpha granule secretory proteins disclosed a potent mesangial cell migratory response to platelet-released fibronectin (Fn), but not to transforming growth factor-alpha (TGF-alpha), -beta (TGF-beta), epidermal growth factor (EGF), or platelet factor 4 (PF4). Secretory levels of platelet Fn (1 to 25 micrograms/ml) induced a maximum migratory response of approximately 60-fold over controls. Mesangial cell migration in response to both platelet Fn and platelet releasate was abrogated by blocking the integrin receptor for Fn with RGDS tetrapeptide. Thus, platelet Fn appears to be a prominent component of platelet releasate responsible for mesangial cell migration.