Control of transforming growth factor-beta activity: latency vs. activation

Role of certain growth factors and hormones in folliculogenesis

Folliculogenesis is an inextricable process associated with female fertility and infertility cases. This process involves many events at cellular and molecular level in a highly orchestrated fashion which culminates with ovulation. Various factors like hormonal factors, growth factors, role of ovarian micro environment, diseases of reproductive tract etc. influence the process of folliculogenesis in systematic manner. The function and mechano-biology of these growth factors and hormones have been studied by many researchers. This review discusses about those hormonal and growth factors which are involved in folliculogenesis process.

Non-thermal plasma treated solution with potential as a novel therapeutic agent for nasal mucosa regeneration

Adequate and rapid mucosal regeneration is one of the most important factors in the healing process of nasal mucosa after surgery or trauma. In particular, delayed mucosal regeneration after surgery is an important cause of surgical failure. However, no effective treatment is available yet. Non-thermal plasma (NTP) has several medical effects, but the existing probe type is limited to local direct treatment. Therefore, we investigated the various effects using liquid type plasma to overcome this limitation. In addition, the therapeutic effects of non-thermal plasma treated solution (NTS) on nasal mucosa have yet to be determined. Experiments were carried out using BEAS-2B, a human bronchial epithelial cell line similar to nasal mucosa epithelium. NTS had no cytotoxicity to the BEAS-2B cells and enhanced cell proliferation. NTS also promoted migration of BEAS-2B cells. NTS increased cell proliferation and migration via epidermal growth factor receptor (EGFR) activities and epithelial-to-mesenchymal transition (EMT) signaling. Furthermore, NTS enhanced wound healing of nasal mucosa in an animal model. Accordingly, NTS promotes nasal mucosa wound healing by increasing cell proliferation and migration. These findings suggest the therapeutic potential of NTS in nasal mucosa wound healing.

Wound Healing of the Nasal and Paranasal Mucosa: A Review

Background

Wound healing is a highly coordinated process involving clot formation, inflammatory reaction, immune response, and, finally, tissue remodeling and maturation. Only few data regarding the specific healing of the nasal or sinusal mucosa are available.

Methods

After a short summary of the general principles of wound healing, the most important data regarding in vitro or in vivo models of wound healing of the nasal and paranasal mucosa are discussed. Attention is paid to clinical application.

Main Findings

First observations regarding the specific regulation of epithelial regeneration by growth factors have underlined the complex relationship between extracellular matrix and epithelium during the repair process. However, only poor and aspecific correlations can be described between endoscopically and histomorphologically defined postoperative phases.

Effect of a combination of mometasone furoate, levofloxacin, and retinyl palmitate with an in situ gel-forming nasal delivery system on nasal mucosa damage repair in an experimental rabbit model

BACKGROUND

In this study a combination of Mometasone Furoate (MF)+Levofloxacin hemihydrate (LH)+Retinyl palmitate (RP) with an in situ gel-forming delivery system was evaluated at different stages of nasal mucosal damage repair in a rabbit maxillary sinus model.

METHODS

In this study, 28 rabbits were included and assigned randomly to four groups. In all rabbits, a standard ostium was opened in the medial wall of the maxillary sinus by using a drill. Two different subsequently prepared gels with an in situ gel-forming delivery system were used. Of these 14 nasal cavities, combination 1 (active combination) was applied daily to 5, combination 2 (placebo) to 5, while 4 did not receive any pharmaceutical treatment. The diameter of the ostium was measured. Histopathological assessment was performed.

RESULTS

After 2, 3 and 4 weeks, the ostium diameter was significantly wider in the group where gel 1 had been applied compared to both the placebo group and control group. In the group treated with gel 1, after 2, 3 and 4 weeks the presence of superficial cilia was significantly greater, surface epithelium significantly less. In the 4th week, histologic scores for fibroblastic proliferation and vascular proliferation in the group treated with gel 1 were better than in either the control group or the placebo group. With gel 1, chronic inflammation parameters were also significantly lower than in the other groups.

CONCLUSION

The MF+LH+RP mixture with an in situ gel-forming nasal delivery system applied for wound healing after FESS prevents the formation of stenosis and is favorable for proper wound healing.

TGF-β signalling in tumour associated macrophages

Tumour associated macrophages (TAM) represent an important component of tumour stroma. They develop under the influence of tumour microenvironment where transforming growth factor (TGF)β is frequently present. Activities of TAM regulated by TGFβ stimulate proliferation of tumour cells and lead to tumour immune escape. Despite high importance of TGFβ-induction of TAM activities till now our understanding of the mechanism of this induction is limited. We have previously developed a model of type 2 macrophages (M2) resembling certain properties of TAM. We established that in M2 TGFβRII is regulated on the level of subcellular sorting by glucocorticoids. Further studies revealed that in M2 with high levels of TGFβRII on the surface TGFβ activates not only its canonical Smad2/3-mediated signaling, but also Smad1/5-mediated signaling, what is rather typical for bone morphogenetic protein (BMP) stimulation. Complexity of macrophage populations, however, allows assumption that TGFβ signalling may function in different ways depending on the functional state of the cell. To understand the peculiarities of TGFβ signalling in human TAMs experimental systems using primary cells have to be developed and used together with the modern mathematical modelling approaches.

Computational approach to characterize causative factors and molecular indicators of chronic wound inflammation

Chronic inflammation is rapidly becoming recognized as a key contributor to numerous pathologies. Despite detailed investigations, understanding of the molecular mechanisms regulating inflammation is incomplete. Knowledge of such critical regulatory processes and informative indicators of chronic inflammation is necessary for efficacious therapeutic interventions and diagnostic support to clinicians. We used a computational modeling approach to elucidate the critical factors responsible for chronic inflammation and to identify robust molecular indicators of chronic inflammatory conditions. Our kinetic model successfully captured experimentally observed cell and cytokine dynamics for both acute and chronic inflammatory responses. Using sensitivity analysis, we identified macrophage influx and efflux rate modulation as the strongest inducing factor of chronic inflammation for a wide range of scenarios. Moreover, our model predicted that, among all major inflammatory mediators, IL-6, TGF-β, and PDGF may generally be considered the most sensitive and robust indicators of chronic inflammation, which is supported by existing, but limited, experimental evidence.

Cytokines as cellular communicators

Cytokines and their receptors are involved in the pathophysiology of many diseases. Here we present a detailed review on cytokines, receptors and signalling routes, and show that one important lesson from cytokine biology is the complex and diverse regulation of cytokine activity. The activity of cytokines is controlled at the level of transcription, translation, storage, processing, posttranslational modification, trapping, binding by soluble proteins, and receptor number and/or function. Translation of this diverse regulation in strategies aimed at the control of cytokine activity will result in the development of more specific and selective drugs to treat diseases.

Prevention and management of hypertrophic scars and keloids after burns in children

Hypertrophic scars and keloids are challenging to manage, particularly as sequelae of burns in children in whom the psychologic burden and skin characteristics differ substantially from adults. Prevention of hypertrophic scars and keloids after burns is currently the best strategy in their management to avoid permanent functional and aesthetical alterations. Several actions can be taken to prevent their occurrence, including parental and children education regarding handling sources of fire and flammable materials, among others. Combination of therapies is the mainstay of current burn scar management, including surgical reconstruction, pressure therapy, silicon gels and sheets, and temporary garments. Other adjuvant therapies such as topical imiquimod, tacrolimus, and retinoids, as well as intralesional corticosteroids, 5-fluorouracil, interferons, and bleomycin, have been used with relative success. Cryosurgery and lasers have also been reported as alternatives. Newer treatments aimed at molecular targets such as cytokines, growth factors, and gene therapy, currently in developing stages, are considered the future of the treatment of postburn hypertrophic scars and keloids in children.

Controversy surrounding the increased expression of TGF beta 1 in asthma

Asthma is a waxing and waning disease that leads to structural changes in the airways, such as subepithelial fibrosis, increased mass of airway smooth muscle and epithelial metaplasia. Such a remodeling of the airways futher amplifies asthma symptoms, but its etiology is unknown. Transforming growth factor β1 is a pleiotropic cytokine involved in many fibrotic, oncologic and immunologic diseases and is believed to play an essential role in airway remodeling that occurs in asthmatic patients. Since it is secreted in an inactive form, the overall activity of this cytokine is not exclusively determined by its level of expression, but also by extensive and complex post-translational mechanisms, which are all importanin modulating the magnitude of the TGFβ1 response. Even if TGFβ1 upregulation in asthma is considered as a dogma by certain investigators in the field, the overall picture of the published litterature is not that clear and the cellular origin of this cytokine in the airways of asthmatics is still a contemporaneous debate. On the other hand, it is becoming clear that TGFβ1 signaling is increased in the lungs of asthmatics, which testifies the increased activity of this cytokine in asthma pathogenesis. The current work is an impartial and exhaustive compilation of the reported papers regarding the expression of TGFβ1 in human asthmatics. For the sake of comparison, several studies performed in animal models of the disease are also included. Inconsistencies observed in human studies are discussed and conclusions as well as trends from the current state of the litterature on the matter are proposed. Finally, the different points of regulation that can affect the amplitude of the TGFβ1 response are briefly revised and the possibility that TGFβ1 is disregulated at another level in asthma, rather than simply in its expression, is highlighted.

Thrombospondin-1 is a major activator of TGF-beta in fibrotic renal disease in the rat in vivo

BACKGROUND

Transforming growth factor-beta (TGF-beta), a profibrotic cytokine involved in many scarring processes, has to be activated extracellularly before it can bind to its receptors. Thrombospondin 1 (TSP1), a multifunctional matricellular glycoprotein, has been identified as an activator of TGF-beta in in vitro systems and during mouse postnatal development in vivo. TSP1 is expressed de novo in many inflammatory disease processes, including glomerular disease.

METHODS

In this study we investigated whether peptides specifically interfering with the activation process of TGF-beta by TSP1 may be able to block activation of TGF-beta in an in vivo model of mesangial proliferative glomerulonephritis.

RESULTS

Continuous intravenous infusion of blocking peptide by minipumps significantly reduced expression of active TGF-beta in glomeruli on day 7 of disease as indicated by immunohistochemistry, bioassay, and activation of the TGF-beta signal transduction pathway, while total TGF-beta expression was unchanged. Inhibition of glomerular TGF-beta activation was accompanied by a decrease of glomerular extracellular matrix accumulation and proteinuria, but was without effect on mesangial cell proliferation or influx of monocytes/macrophages.

CONCLUSION

TSP1 is a major endogenous activator of TGF-beta in experimental inflammatory glomerular disease. Drugs interfering with the activation of TGF-beta by locally produced TSP1 may be considered as a future specific treatment of scarring kidney disease.

Antisense oligonucleotides against thrombospondin-1 inhibit activation of tgf-beta in fibrotic renal disease in the rat in vivo

Specific treatment of chronic progressive renal disease is very limited. TGF-beta, considered as the major cytokine causing tissue scarring, must be activated extracellularly before it can bind to its receptors. Thrombospondin-1 (TSP1) has been identified as an activator of latent TGF-beta in in vitro systems and in pancreas and lung homeostasis in mouse pups in vivo, but whether this is also true in inflammatory fibrotic disease is unknown. We examined a rat model of mesangial proliferative glomerulonephritis, where TGF-beta has been demonstrated to mediate renal fibrosis. In this study, antisense phosphorothioate oligonucleotides against TSP1 were successfully transferred into almost all glomeruli of perfused diseased kidneys and markedly inhibited de novo synthesis of TSP1. This effect was accompanied by decreased activation but not expression of TGF-beta and by the inhibition of the TGF-beta-dependent smad-signaling pathway, as well as transcription of TGF-beta target genes such as EDA-fibronectin, resulting in a markedly suppressed accumulation of extracellular matrix. In sharp contrast, neither glomerular cell proliferation nor influx of macrophages was affected by this therapy in experimental mesangial proliferative glomerulonephritis. These results demonstrate that TSP1 is the major endogenous activator of TGF-beta in experimental inflammatory kidney disease.

Expression patterns of Tgfbeta1-3 associate with myocardialisation of the outflow tract and the development of the epicardium and the fibrous heart skeleton

Transforming growth factor-beta (Tgfbeta) is essential for normal embryogenesis. The cardiac phenotypes obtained after knockout of each of the three mammalian isoforms suggest different roles during morphogenesis. We studied cardiovascular expression of Tgfbeta1-3 in parallel tissue sections of normal mouse embryos from 9.5 to 15.5 days post coitum (dpc) by using radioactive in situ hybridisation. The Tgfbeta isoforms are differentially expressed in unique and in overlapping patterns during cardiovascular development. In the vessels, Tgfbeta1 is found in the intima, whereas Tgfbeta2 and -beta3 are mainly present in the media and adventitia of the great arteries. Tgfbeta1 is present in the endocardium at all stages examined. The Tgfbeta2 signal in the endocardium of the atrioventricular canal and outflow tract (9.5 dpc) shifts during epithelial-mesenchymal transformation toward the mesenchymal cushions (10.5-11.5 dpc) after which it exhibits a marked spatiotemporal expression pattern as the cushion differentiation progresses (11.5-15.5 dpc). The myocardium underlying the endocardial cushions and the atrial muscular septum are intensely positive for Tgfbeta2 at early stages (9.5-11.5 dpc) and expression decreases at 12.5 days. In contrast to earlier reports, we find marked overlap of Tgfbeta2 and -beta3 expression. Tgfbeta3 expression shows a characteristic distribution in the mesenchymal cushions, suggesting a role in cushion differentiation, possibly additional to Tgfbeta2. From 14.5 dpc onward, a strong Tgfbeta3 signal is found in the fibrous septum primum of the atrium and in the fibrous skeleton of the heart. Special attention was paid to the proepicardial organ and its derivatives. The proepicardial organ strongly expresses Tgfbeta2 as early as 9.5 days, and all isoforms are present in the epicardium from 12.5 dpc onward. The spatiotemporal cardiovascular expression of Tgfbeta1-3 supports both specific and complementary functions during cardiovascular development that might explain functional redundancy between the Tgfbeta-isoforms. The information provided favors novel roles of Tgfbeta1-3 in epicardial development, of Tgfbeta2 in myocardialisation, and of Tgfbeta3 in differentiation of the fibrous structures of the heart.

Transforming growth factor-beta signal transduction and progressive renal disease

Transforming growth factor-beta (TGF-beta) superfamily members are multifunctional growth factors that play pivotal roles in development and tissue homeostasis. Recent studies have underscored the importance of TGF-beta in regulation of cell proliferation and extracellular matrix synthesis and deposition. TGF-beta signaling is initiated by ligand binding to a membrane-associated receptor complex that has serine/threonine kinase activity. This receptor complex phosphorylates specific Smad proteins, which then transduce the ligand-activated signal to the nucleus. Smad complexes regulate target gene transcription either by directly binding DNA sequences, or by complexing with other transcription factors or co-activators. There is extensive crosstalk between the TGF-beta signaling pathway and other signaling systems, including the mitogen-activated protein kinase pathways. The importance of TGF-beta in regulation of cell growth has been emphasized by recent observations that mutations of critical elements of the TGF-beta signaling system are associated with tumor progression in patients with many different types of epithelial neoplasms. TGF-beta has emerged as a predominant mediator of extracellular matrix production and deposition in progressive renal disease and in other forms of chronic tissue injury. In this overview, recent advances in our understanding of TGF-beta signaling, cell cycle regulation by TGF-beta, and the role of TGF-beta in progressive renal injury are highlighted.

TGF-beta1 is an autocrine mediator of renal tubular epithelial cell growth and collagen IV production

Recent studies in cultured cells have provided evidence that a variety of pathobiologic stimuli, including high glucose, angiotensin II, and thromboxane A(2), trigger a signaling pathway leading to autocrine induction of TGF-beta1. TGF-beta1 production through this pathway may profoundly affect cell growth, matrix synthesis, and response to injury. This study examines the role of autocrine versus exogenously added TGF-beta1 in cellular proliferation and collagen IV production, critical targets of TGF-beta1 signaling, using renal cells derived from TGF-beta1 knockout (KO) animals or wild-type (WT) controls. Growth of WT and KO cells was assessed by cell counting and [(3)H]thymidine uptake. Basal and TGF-beta1-stimulated collagen production was assessed by Northern and Western blotting; transcriptional activity of the alpha1(IV) collagen gene was assessed by transient transfection analysis. KO cells grew at a faster rate than WT cells carefully matched for plating density and passage number. This increased growth rate was paralleled by increases in [(3)H]thymidine uptake. KO cells expressed lower levels of the cell cycle inhibitors p21 and p27 than WT cells. KO cells failed to express TGF-beta1, as expected. Basal TGF-beta3 mRNA levels were higher in KO cells than in WT cells. WT cells expressed higher basal levels of TGF-beta2 mRNA than KO cells. Basal alpha1(IV) and alpha2(IV) collagen mRNA and protein expression were significantly lower in KO cells than WT cells. Administration of exogenous TGF-beta1 induced collagen IV production in both KO and WT cells. Although basal transcriptional activity of an alpha1(IV) collagen-CAT construct was lower in KO cells than WT cells, administration of exogenous TGF-beta1 was associated with significant increases in transcriptional activity of this construct in both KO and WT cells. These studies provide evidence that autocrine production of TGF-beta1 may play a critical role in regulation of growth and basal collagen IV production by renal tubular epithelial cells.

TGFbeta2 activation status during cardiac morphogenesis

Transforming growth factor beta (TGFbeta) is secreted as a biologically inactive complex by many cell types in vitro, but little is known of TGFbeta's activation status in vivo. This study examined the in vivo expression of active and total (active + acid-activatable) TGFbeta2 in embryonic chicken hearts during cardiac morphogenesis (Hamburger-Hamilton stage 10-24). The concentration of TGFbeta2 was measured by an enzyme-linked immunoassay that recognized active TGFbeta2. Whole heart homogenates were either left untreated to measure active TGFbeta2 or treated with acid before assay to measure total (active + acid-activatable) TGFbeta2. Total TGFbeta2 concentration increased more than 16-fold between stage 10/11 and stage 24. Active TGFbeta2 concentration was highest at stage 14/15, but overall remained relatively constant varying at most by 2.8-fold. When expressed relative to total TGFbeta2, the amount of active TGFbeta2 progressively declined from 70% in stage 10/11 hearts to 7% in stage 24 hearts. The distribution of active and total TGFbeta2 was examined by immunostaining with an antibody against active TGFbeta2. Before immunostaining, sections were either treated with acid or left untreated to determine the distribution of total and active TGFbeta2, respectively. Active TGFbeta2 immunostaining was first detected in the endothelium, myocardium, and cardiac jelly of stage 14 hearts. Acid treatment had no effect on the distribution or intensity of immunostaining at this stage. Faint, active TGFbeta2 immunostaining was restricted to the ventricular myocardium in stage 18 hearts. Acid treatment resulted in a marked increase in staining intensity in the ventricle, but no staining was observed in the atrium or outflow tract. In stage 24 hearts, faint active TGFbeta2 staining was detected in the ventricle before acid treatment. After acid treatment, patches of intense punctate stain were found in all regions of the embryonic heart. Increases in TGFbeta2 concentration and immunostaining intensity after acidification suggest that a significant amount of TGFbeta2 is in the latent form. Stage-dependent differences in activation status suggest that activation may be a developmentally regulated process in the chick heart and support the notion that activation is an important step in regulating TGFbeta actions in vivo.

Role of TGF-beta in immune-evasion of cancer

One of the major obstacles in tumor-immunology is the outgrowth of malignant tumors despite their immunogenicity and recognition by the immune-system. Multiple mechanisms for this phenomenon have been proposed. We review the possible involvement of transforming growth factor beta (TGF-beta) in this context. TGF-beta is a cytokine with pleiotropic functions, involved in multiple physiologic processes including immunoregulation. Immune elimination of most cancers ultimately depends on cytolytic T cells (CTL). We propose a mechanism of specific suppression of cytolytic T cell (CTL)-responses mediated through immunoglobulin-bound TGF-beta (IgG-TGF-beta), secreted by activated B cells, and a cell of myeloid origin. This mononuclear "Veto" cell presumably binds IgG-TGF-beta through Fc-receptors and activates latent TGF-beta. The suggestion that B cell responses can inhibit tumor rejection is supported by observations in B cell-deficient mice. Ways for enhancing effective cancer immunity by interfering with the network of interactions involving IgG-TGF-beta are discussed.

Overexpression of active TGF-beta-1 in the murine knee joint: evidence for synovial-layer-dependent chondro-osteophyte formation

OBJECTIVE

To investigate the impact of a prolonged and constant active TGF-beta expression by the synovial lining cells on cartilage and ligamentous joint structures in vivo.

DESIGN

An adenoviral vector (AdTGF-beta1(223,225)) was used for the overexpression of active TGF-beta1 in knee joints of C57Bl/6 mice.

RESULTS

It was found that physiological relevant levels of active TGF-beta1 produced by the synovial lining layer resulted in histopathological changes: hyperplasia of synovium and chondro-osteophyte formation at the so-called chondro-synovial junctions. No histological changes were seen after intra-articular injection of an empty control vector (AdDL70-3) or by overexpression of latent TGF-beta1 (AdTGF-beta1). The predominant site of TGF-beta production in osteoarthritis (OA) and rheumatoid arthritis (RA) is the synovial lining layer. To address the question whether the TGF-beta-induced changes were related to the expression site in the synovial lining, the synovial lining layer was depleted by local treatment with liposomes encapsulating clodronate. Depletion of the lining resulted in a dramatic change of TGF-beta1-induced pathology: markedly reduced chondro-osteophyte formation and increased accumulation of extracellular matrix in the synovium.

CONCLUSION

This study shows that overexpression of active TGF-beta1 in the knee joint results in OA-like changes and suggests the synovial lining cells contribute to the chondro-osteophyte formation.

Interaction between angiotensin II and Smad proteins in fibroblasts in failing heart and in vitro

Angiotensin II (angiotensin) and transforming growth factor (TGF)-beta(1) play an important role in cardiac fibrosis. We examined Smad proteins in 8-wk post-myocardial infarction (MI) rat hearts. AT(1) blockade (losartan) attenuated the activation of TGF-beta(1) in target tissues. Losartan administration (8 wk, 15 mg. kg(-1). day(-1)) normalized total Smad 2 overexpression in infarct scar and remnant heart tissue and normalized Smad 4 in infarct scar. Phosphorylated Smad 2 (P-Smad 2) staining decreased in cytosol from failing heart vs. the control, which was normalized by losartan, suggesting augmented P-Smad 2 movement into nuclei in untreated failing hearts. Using adult primary rat fibroblasts treated with angiotensin (10(-6) M), we noted rapid translocation (15 min) of P-Smad 2 into the nuclei from the cytosol. Nuclear P-Smad 2 protein level increased with angiotensin treatment, which was blocked by losartan. We conclude that angiotensin may influence total Smad 2 and 4 expression in post-MI heart failure and that angiotensin treatment is associated with rapid P-Smad 2 nuclear translocation in isolated fibroblasts. This study suggests that cross talk between angiotensin and Smad signaling is associated with fibrotic events in post-MI hearts.

Cellular interactions and signaling in cartilage development

The long bones of the developing skeleton, such as those of the limb, arise from the process of endochondral ossification, where cartilage serves as the initial anlage element and is later replaced by bone. One of the earliest events of embryonic limb development is cellular condensation, whereby pre-cartilage mesenchymal cells aggregate as a result of specific cell-cell interactions, a requisite step in the chondrogenic pathway. In this review an extensive examination of historical and recent literature pertaining to limb development and mesenchymal condensation has been undertaken. Topics reviewed include limb initiation and axial induction, mesenchymal condensation and its regulation by various adhesion molecules, and regulation of chondrocyte differentiation and limb patterning. The complexity of limb development is exemplified by the involvement of multiple growth factors and morphogens such as Wnts, transforming growth factor-beta and fibroblast growth factors, as well as condensation events mediated by both cell-cell (neural cadherin and neural cell adhesion molecule) and cell-matrix adhesion (fibronectin, proteoglycans and collagens), as well as numerous intracellular signaling pathways transduced by integrins, mitogen activated protein kinases, protein kinase C, lipid metabolites and cyclic adenosine monophosphate. Furthermore, information pertaining to limb patterning and the functional importance of Hox genes and various other signaling molecules such as radical fringe, engrailed, Sox-9, and the Hedgehog family is reviewed. The exquisite three-dimensional structure of the vertebrate limb represents the culmination of these highly orchestrated and strictly regulated events. Understanding the development of cartilage should provide insights into mechanisms underlying the biology of both normal and pathologic (e.g. osteoarthritis) adult cartilage.

Equid herpesvirus 1: platelets and alveolar macrophages are potential sources of activated TGF-B1 in the horse

Cell mediated responses to Equid herpesvirus 1 (EHV-1) are of short duration in vivo and require considerable expansion to be detected in vitro. Raised serum levels of active transforming growth factor B (TGF-B1) have been shown to depress proliferative T cell responses in experimental infections with EHV-1 in ponies. The present work indicates that latent transforming growth factor B (TGF-B1) is present in circulating platelets, lymph node, bronchial epithelium and alveolar macrophages. Activation of platelets in vitro by thrombin resulted in the release of latent TGF-B1 from platelets, with a pg level of conversion to active TGF-B1, but virus alone did not activate TGF-B1. Exposure of circulating leucocytes to EHV-1 in vivo or in vitro does not result in detection of active TGF-B1 above residual levels that could be attributed to activation of platelets by manipulation. However, alveolar macrophages obtained by lavage at autopsy yield both latent and active TGF-B1 in ng quantities. Bronchial epithelium, and mesenteric lymph node leucocytes had equivalent levels of latent TGF-B1, but horses varied as to whether these tissues were a source of activated TGF-B1 and as to whether EHV-1 activated TGF-B1.

Transforming growth factor-beta(1) restores antiplatelet function of endothelial cells exposed to anoxia-reoxygenation injury

Transforming growth factor-beta(1) released from platelet alpha-granules may preserve endothelial functions in injured vessels. However, direct evidence is lacking regarding how this cytokine modifies the antithrombotic function of injured endothelial cells. We performed an in vitro study to investigate the effects of transforming growth factor-beta(1) on platelet functions in the presence of cultured endothelial cells exposed to anoxia-reoxygenation injury. Cultured bovine aorta endothelial cells were placed in an anoxic chamber (0.5% O(2), 5% CO(2)) for 60 minutes followed by a 90-minute reoxygenation. Collagen (2 microg/mL)-induced platelet aggregation (10(8) platelets/mL), as determined by impedance aggregometry, was potently inhibited in the presence of control endothelial cells (17.4+/-3.3 Omega) at a concentration of 5x10(4) cells/mL, as compared to their absence (68. 2+/-2.2 Omega). Inhibition of platelet aggregation was attenuated in endothelial cells exposed to anoxia-reoxygenation (54.6+/-2.5 Omega). However, preincubation of endothelial cells with transforming growth factor-beta(1) (1.0 ng/mL) for 16 hours partially recovered the inhibitory capability of platelet aggregation by injured endothelial cells (40.6+/-3.8 Omega). Cell viability, confirmed by a trypan blue dye exclusion test, was similar (93-96%), including control, 1.0 ng/mL transforming growth factor-beta(1)- and/or anoxia-reoxygenation-pretreated cells. The capability of platelet inhibition was restored when the endothelial cells were preincubated for 4 hours or more. Restoration of antiplatelet capacity in endothelial cells by transforming growth factor-beta(1) was suggested to be due to several mechanisms, including an increase in nitric oxide synthase activity, up-regulation of prostacyclin release, and restoration of adenosine triphosphate diphosphohydrolase activity, which was attenuated by anoxia-reoxygenation pretreatment. In summary, transforming growth factor-beta(1) released from activated platelets may play a compensatory role in the preservation of endothelial functions to inhibit platelet activation.

Apoptosis and the liver

Regulation of the homeostatic balance between cell proliferation and programmed cell death, apoptosis, is essential for development and maintenance of multicellular organisms. Apoptosis is a genetically and evolutionarily highly conserved process. Analysis of the molecular mechanisms of apoptosis has led to a better understanding of many human diseases. Notably in cancer, but also in infectious or autoimmune disease, a deficiency in apoptosis is one of the key events in pathophysiology. On the other hand, overefficient apoptosis, as observed in fulminant liver failure, may be equally harmful for the organism indicating that a tight regulation of the apoptotic machinery is essential for survival. The execution of apoptosis may be initiated by many different signals, either from within or outside the cell involving ligand-receptor interactions, as has been shown for Fas/Fas-ligand, TNF-alpha/TNF-receptor or TGF-beta/TGF-receptor, or potentially by more unspecific signals such as ceramide or DNA damage. During the modulation phase of apoptosis many different genes such as p53, c-myc or Bcl-2/Bax have been shown to able to shift the balance either to cell survival or cell death.

Role of transforming growth factor beta-1 in peritonitis-induced adhesions

Peritonitis is a major cause of intra-abdominal adhesion formation. The overexpression of transforming growth factor beta-1 (TGF-Beta1), a potent mitogen, chemoattractant, and stimulant for collagen synthesis by fibroblasts, has been linked to tissue fibrosis at various sites throughout the body including peritoneal adhesion formation. Hence we hypothesized that the mechanism(s) involved in peritonitis-induced adhesion formation may be mediated through the upregulation of TGF-Beta1 expression. Peritonitis was induced in rats by cecal ligation and puncture, while a control group underwent sham operation. Adhesions were scored and harvested from both groups at 0, 6 and 12 hours and at 1, 2, 4, 7, and 28 days. Tissue expression of TGF-Beta1 mRNA was determined by quantitative reverse transcription-polymerase chain reaction and TGF-Beta1 protein was localized by immunohistochemical analysis. Serum and peritoneal fluid TGF-Beta1 concentrations were quantified by enzyme-linked immunosorbent assay. Compared with sham operation, peritonitis was associated with a significantly greater incidence of abdominal adhesions and a significant increase in the levels of TGF-Beta1 mRNA expression at days 2, 4, and 7. Immunostaining intensity of TGF-Beta1 in adhesions from the peritonitis group also steadily rose through day 7. In peritoneal fluid, the ratio of active:total TGF-Beta1 was significantly increased in the peritonitis group on days 1, 2, and 4 compared with the sham group. These results suggest that peritonitis is associated with the upregulation of TGF-Beta1, a mechanism that may exacerbate adhesion formation.

Bidirectional regulation of macrophage function by TGF-beta

The dual role of transforming growth factor-beta (TGF-beta) in modulating macrophage function is an important concept gaining increasing recognition. In addition to its role as a 'macrophage-deactivating' agent, TGF-beta functions as a monocyte activator, inducing cytoke production and mediating host defence. These functions are context-dependent, modulated by the differentiation state of the cell, the local cytokine environment, and the local levels of TGF-beta in itself. In general, during the initial stages of inflammation, TGF-beta locally acts as a proinflammatory agent by recruiting and activating resting monocytes. As these cells differentiate specific immunosuppressive actions of TGF-beta predominate, leading to resolution of the inflammatory response. Increasing our understanding of the bidirectional regulation of macrophage function will facilitate prediction of the ultimate outcome of modulating TGF-beta levels in vivo.

A transforming growth factor-beta antagonist unmasks the neuroprotective role of this endogenous cytokine in excitotoxic and ischemic brain injury

Various studies describe increased concentrations of transforming growth factor-beta (TGF-beta) in brain tissue after acute brain injury. However, the role of endogenously produced TGF-beta after brain damage to the CNS remains to be clearly established. Here, the authors examine the influence of TGF-beta produced after an episode of cerebral ischemia by injecting a soluble TGF-beta type II receptor fused with the Fc region of a human immunoglobulin (TbetaRIIs-Fc). First, this molecular construct was characterized as a selective antagonist of TGF-beta. Then, the authors tested its ability to reverse the effect of TGF-beta1 on excitotoxic cell death in murine cortical cell cultures. The addition of 1 microg/mL of TbetaRIIs-Fc to the exposure medium antagonized the neuroprotective activity of TGF-beta1 in N-methyl-D-aspartate (NMDA)-induced excitotoxic cell death. These results are consistent with the hypothesis that TGF-beta1 exerts a negative modulatory action on NMDA receptor-mediated excitotoxicity. To determine the role of TGF-beta1 produced in response to brain damage, the authors used a model of an excitotoxic lesion induced by the intrastriatal injection of 75 nmol of NMDA in the presence of 1.5 microg of TbetaRIIs-Fc. The intrastriatal injection of NMDA was demonstrated to induce an early upregulation of the expression of TGF-beta1 mRNA. Furthermore, when added to the excitotoxin, TbetaRIIs-Fc increased (by 2.2-fold, P < 0.05) the lesion size. These observations were strengthened by the fact that an intracortical injection of TbetaRIIs-Fc in rats subjected to a 30-minute reversible cerebral focal ischemia aggravated the volume of infarction. In the group injected with the TGF-beta1 antagonist, a 3.5-fold increase was measured in the infarction size (43.3 +/- 9.5 versus 152.8 +/- 46.3 mm3; P < 0.05). In conclusion, by antagonizing the influence of TGF-beta in brain tissue subjected to excitotoxic or ischemic lesion, the authors markedly exacerbated the resulting extent of necrosis. These results suggest that, in response to such insults, brain tissue responds by the synthesis of a neuroprotective cytokine, TGF-beta1, which is involved in the limitation of the extent of the injury. The pharmacologic potentiation of this endogenous defensive mechanism might represent an alternative and novel strategy for the therapy of hypoxic-ischemic cerebral injury.

Smoke extract stimulates lung fibroblasts to release neutrophil and monocyte chemotactic activities

Accumulation of monocytes and neutrophils and fibrous distortion of the airway are characteristics of airway disease secondary to smoking. The presence of inflammatory cells and fibrosis correlate, and, therefore, we postulated that lung fibroblasts might release chemotactic activity for neutrophils and monocytes in response to smoke extract. To test this hypothesis, human fetal lung (HFL1) fibroblasts were cultured, and the supernatant fluid was evaluated for neutrophil (NCA) and monocyte (MCA) chemotactic activities with a blind well chamber technique. HFL1 fibroblasts released chemotactic activity in response to smoke extract in a dose- and time-dependent manner (P < 0.05). Checkerboard analysis showed that the activity was predominantly chemotactic. Partial characterization of the released chemotactic activity revealed that the activity was partly heat labile, trypsin sensitive, and ethyl acetate extractable. Lipoxygenase inhibitors and cycloheximide inhibited the release of both NCA and MCA. Molecular-sieve chromatography revealed that NCA and MCA were heterogeneous. NCA was inhibited by anti-human interleukin (IL)-8 and anti-granulocyte colony-stimulating factor antibodies and a leukotriene (LT) B(4)-receptor antagonist. Anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) and anti-monocyte chemoattractant protein (MCP)-1 antibodies and an LTB(4)-receptor antagonist inhibited MCA. Immunoreactive IL-8, granulocyte colony-stimulating factor, GM-CSF, and MCP-1 significantly increased in culture supernatant fluid in response to smoke extract. Finally, smoke extract augmented the expression of mRNAs of IL-8, GM-CSF, and MCP-1. These data demonstrate that lung fibroblasts release NCA and MCA in response to smoke extract and suggest that lung fibroblasts may modulate the inflammatory cell recruitment into the lung.

Regulation of neuronal K(+) currents by target-derived factors: opposing actions of two different isoforms of TGFbeta

The developmental expression of macroscopic Ca(2+)-activated K(+) currents in chick ciliary ganglion neurons is dependent on an avian ortholog of TGFbeta1, known as TGFbeta4, secreted from target tissues in the eye. Here we report that a different isoform, TGFbeta3, is also expressed in a target tissue of ciliary ganglion neurons. Application of TGFbeta3 inhibits the functional expression of whole-cell Ca(2+)-activated K(+) currents evoked by 12 hour treatment with either TGFbeta1 or beta-neuregulin-1 in ciliary ganglion neurons developing in vitro. TGFbeta3 had no effect on voltage-activated Ca(2+) currents. A neutralizing antiserum specific for TGFbeta3 potentiates stimulation of Ca(2+)-activated K(+) currents evoked by a target tissue (iris) extract in cultured ciliary ganglion neurons, indicating that TGFbeta3 is an inhibitory component of these extracts. Intraocular injection of TGFbeta3 causes a modest but significant inhibition of the expression of Ca(2+)-activated K(+) currents in ciliary ganglion neurons developing in vivo. Further, intraocular injection of a TGFbeta3-neutralizing antiserum stimulates expression of Ca(2+)-activated K(+) currents in ciliary ganglion neurons developing in vivo, indicating that endogenous TGFbeta3 regulates the functional expression of this current. The normal developmental expression of functional Ca(2+)-activated K(+) currents in ciliary ganglion neurons developing in vivo is therefore regulated by two different target-derived isoforms of TGFbeta, which produce opposing effects on the electrophysiological differentiation of these neurons.

BMP signalling in early Xenopus development

Bone morphogenetic proteins (BMPs) are typically members of the transforming growth factor beta (TGF-beta) family with diverse roles in embryonic development. At least five genes with homology to BMPs are expressed during Xenopus development, along with their receptors and intracellular signalling pathways. The evidence suggests that BMPs have roles to play in both mesoderm induction and dorsoventral patterning. Studies in Xenopus have also identified a number of inhibitory binding proteins for the classical BMPs, encoded by genes such as chordin and noggin. These proteins appear to be responsible for establishing a morphogen gradient of BMP4 activity, which specifies different dorsoventral fates in early gastrulae. An emerging theme is that inhibition of BMP signalling is an important mechanism regulating cell fate decisions in early development.

TGF-beta receptor expression in human odontoblasts and pulpal cells

Transforming growth factor-beta (TGF-beta) isoform expression by odontoblasts leads to their sequestration within the dentine matrix, from where they may be released during caries and participate in the reparative processes. Two receptor types for TGF-beta have been implicated in TGF-beta induced signalling. The aim of this study was to characterise immunohistochemically the expression of these receptors in sound and carious human teeth to facilitate our understanding of the ability of these cells to respond to TGF-beta stimulation. Sound and carious human teeth were routinely processed and paraffin sections stained for TGF-beta receptors I and II, using the StrAviGen immunoperoxidase method. Strong specific staining for both receptor types was observed in the odontoblasts of healthy teeth with the greatest intensity seen with receptor I. Staining of weaker intensity was also observed for both receptors in the underlying cell rich area and pulp core. Similar patterns of staining were observed within carious tissues. We conclude that odontoblasts and other cells of the pulp of mature human molar teeth show the presence of both TGF-beta receptors I and II in health and disease with odontoblasts showing the strongest expression. Such findings may be important in the response of these cells to tissue injury.

Seminal transforming growth factor-beta in normal and infertile men

Transforming growth factor-beta (TGFbeta) is a cytokine with autocrine and paracrine action in the testis and potent immunoregulatory and anti-inflammatory activities. In the present study, we examined the concentration of latent (acid-activatable) and free (active) TGFbeta in seminal plasma from normal subjects (n = 23) and infertile (n = 40) patients, by using a TGFbeta specific immunoenzymological assay, and a bioassay (CCL64 cell line growth inhibition) detecting any form of TGFbeta. Free TGFbeta1 was present in normal subjects at a concentration (1.82 +/- 1.06 ng/ml) close to that known to give maximal stimulation in vitro. In pathological groups, the mean concentrations were not significantly different from the normal ones. Latent TGFbeta1 was present in normal seminal plasma at a high concentration (92.4 +/- 29.2 ng/ml). In subjects with pathologies of both testis and genital apparatus, or with epididymal occlusion, mean latent TGFbeta1 concentrations were normal, whereas transferrin concentrations were lower. The concentrations found in the epididymal occlusion group indicate that TGFbeta1 is, for a large part, secreted by the genital tract. In the testicular pathology group, TGFbeta1 concentrations were 130.7 +/- 61.2 ng/ml, a mean not statistically different from normal, although higher. No differences were found between patients with high and normal blood plasma follicle stimulating hormone, and this is consistent with the notion that most TGFbeta1 in seminal plasma is not of testicular origin. The TGFbeta bioassay ensured that immunologically detected TGFbeta was present in a bioactive or bioactivatable form. Furthermore, the values found in normal and pathological seminal plasmas were usually higher than those detected by the immunoassay, suggesting that other forms of TGFbeta might be present. Together, the present data show that very large amounts of TGFbeta are present in human seminal plasma. The TGFbeta ligand assay in the seminal plasma appears to indicate no differences between normal and infertile subjects.

Nasal administration of transforming growth factor-beta1 induces dendritic cells and inhibits protracted-relapsing experimental allergic encephalomyelitis

Cytokines have a crucial role in initiation and perturbation of EAE that represents an animal model of multiple sclerosis (MS). Administration of transforming growth factor-beta1 (TGF-beta1) to EAE mice improves clinical EAE and prevents relapses by unknown mechanisms. Administering low doses of TGF-beta1 nasally, we confirmed that TGF-beta1 inhibited development and relapse of protracted-relapsing EAE (PR-EAE) in DA rats. Infiltration of CD4+ T-cells and macrophages within the central nervous system was clearly reduced, while proliferation and IFN-gamma secretion of mononuclear cells (MNC) was augmented in TGF-beta1-treated EAE rats compared to PBS-treated control EAE rats. TGF-beta1 administered nasally also increased nitric oxide production and CD4+ T cell apoptosis. TGF-beta1 treated rats showed augmented proliferation of dendritic cells (DC) compared to MNC. These data imply that low doses of TGF-beta1 given by the nasal route prevent PR-EAE and upregulate DC functions that may be involved for disease prevention.

TGF-beta1 in liver fibrosis: an inducible transgenic mouse model to study liver fibrogenesis

Transforming growth factor-beta1 (TGF-beta1) is a powerful stimulus for collagen formation in vitro. To determine the in vivo effects of TGF-beta1 on liver fibrogenesis, we generated transgenic mice overexpressing a fusion gene [C-reactive protein (CRP)/TGF-beta1] consisting of the cDNA coding for an activated form of TGF-beta1 under the control of the regulatory elements of the inducible human CRP gene promoter. Two transgenic lines were generated with liver-specific overexpression of mature TGF-beta1. After induction of the acute phase response (15 h) with lipopolysaccharide (100 microgram ip), plasma TGF-beta1 levels reached >600 ng/ml in transgenic animals, which is >100 times above normal plasma levels. Basal plasma levels of uninduced transgenic animals were about two to five times above normal. As a consequence of hepatic TGF-beta1 expression, we could demonstrate marked transient upregulation of procollagen I and procollagen III mRNA in the liver 15 h after the peak of TGF-beta1 expression. Liver histology after repeated induction of transgene expression showed an activation of hepatic stellate cells in both transgenic lines. The fibrotic process was characterized by perisinusoidal deposition of collagen in a linear pattern. This transgenic mouse model gives in vivo evidence for the important role of TGF-beta1 in stellate cell activation and liver fibrogenesis. Due to the ability to control the level of TGF-beta1 expression, this model allows the study of the regulation and kinetics of collagen synthesis and fibrolysis as well as the degree of reversibility of liver fibrosis. The CRP/TGF-beta1 transgenic mouse model may finally serve as a model for the testing of antifibrogenic agents.

M6P/IGFII-receptor complexes urokinase receptor and plasminogen for activation of transforming growth factor-beta1

Transforming growth factor-beta1 (TGF-beta1) is a critical cytokine for cell proliferation and differentiation. It is secreted by many cells in a latent pro-form (LTGF-beta1) from which biologically active TGF-beta1 is released by an in vivo mechanism that is not known. Here we show that the mannose-6-phosphate/insulin-like growth factor II-receptor (M6P/IGFII-R), which binds LTGF-beta1, complexes with urokinase (plasminogen activator)-receptor (uPA-R) on the surface of human monocytes and directly binds plasminogen (Plg). Plasmin generated from Plg in the complex mediates release of TGF-beta1 when M6P/IGFII-R is associated with uPA-R. Thus, this interaction of M6P/IGFII-R and uPA-R suggests a potential mechanism for the generation of TGF-beta1 by cells.

Upregulation and spatial shift in the localization of the mannose 6-phosphate/insulin-like growth factor II receptor during radiation enteropathy development in the rat

BACKGROUND AND PURPOSE

Transforming growth factor beta1 (TGF-beta1) appears to play an important role in the pathogenesis of chronic radiation-induced fibrosis in the intestine and several other organs. TGF-beta1 is secreted as a non-biologically active complex and its function depends on activation. In vitro data suggest that the mannose 6-phosphate/insulin-like growth factor-beta (M6P/IGF-II) receptor is involved in the mechanism of TGF-beta1 activation. Thus, we used a rat model of radiation enteropathy to examine the potential role of the M6P/IGF-II receptor in the in vivo regulation of TGF-beta1 activity and localization.

MATERIALS AND METHODS

A scrotal hernia containing a loop of small intestine was created in male rats. The intestine in the scrotum was exposed to 0, 12, or 21 Gy single dose X-radiation. Groups of rats were euthanized 1 day and 2, 6 and 26 weeks after irradiation. Histopathologic injury was assessed with a radiation injury score (RIS). Computerized image analysis was used to identify M6P/IGF-II receptor-positive cells and to quantify extracellular matrix-associated TGF-beta1 immunoreactivity. Changes in urokinase plasminogen activator (uPA), tissue-like plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) immunoreactivity were also assessed.

RESULTS

In normal (sham-irradiated) intestine, M6P/IGF-II immunoreactivity was confined to relatively weak, but specific epithelial staining. Irradiated intestine exhibited a highly significant time- and dose-dependent increase in the number of M6P/IGF-II receptor-positive cells (P < 0.001). There was a striking spatial shift of M6P/IGF-II receptor immunoreactivity from epithelium during the early post-radiation phase to stromal cells, most notably fibroblasts during the later stages of injury. Irradiated intestine exhibited distinct co-localization of M6P/ IGF-II receptor-positive cells and extracellular matrix-associated TGF-beta1 in areas of histopathologic injury. There were highly significant associations between the number of M6P/IGF-II receptor-positive stromal cells and TGF-beta1 immunoreactivity (P < 0.001), radiation-induced fibrosis (P < 0.001) and RIS (P < 0.001). Endothelial tPA immunoreactivity decreased significantly after irradiation (P < 0.001), whereas uPA and PAI-1 immunoreactivity levels appeared to be unchanged.

CONCLUSIONS

M6P/IGF-II receptor upregulation may be a key factor in the in vivo control of TGF-beta1 activity and responsible for the tissue specificity of TGF-beta1 action after irradiation.

Mechanisms of progression of renal damage in lupus nephritis: pathogenesis of renal scarring

Lupus nephritis results from an acute inflammatory and immunological response to renal immune complex deposition. The acute response is characterized by activation of circulating leukocytes and renal parenchymal cells, triggering the production of pro-inflammatory cytokines and growth factors. In all too many cases, this response is followed by a chronic response, which is characterized by excessive deposition of collagen and other extracellular matrix macromolecules and the development of end-stage renal disease. Mechanisms underlying this chronic response in progressive renal disease are not adequately defined. In this overview, potential roles of reactive oxygen species (ROS) generation and transforming growth factor-beta (TGF-beta) production in the pathogenesis of lupus nephritis are considered. ROS and TGF-beta may be key elements of a pathway leading to persistent and excessive matrix deposition in progressive lupus nephritis. Further studies to define the role of this pathway in lupus nephritis may lead to the development of additional, more specific therapeutic targets to prevent progression of renal disease.

Active transforming growth factor-beta in wound repair: determination using a new assay

Transforming growth factor (TGF)-beta regulates wound repair and scarring in an isoform-specific fashion. TGF-beta is produced in a latent form, and its activation is a critical regulatory step controlling the bioactivity of this growth factor. To date, it has been impossible to determine latent TGF-beta activation in vivo due to a lack of quantitative assays. We describe here a semiquantitative modification of the plasminogen activator inhibitor-1/luciferase bioassay (PAI/L assay) for TGF-beta, which we used to determine active and latent TGF-beta isoforms in frozen sections of rat wound tissue. We found that significant amounts of latent TGF-beta were rapidly activated upon wounding (38% of the total TGF-beta at 1 hour after wounding). A second peak of active TGF-beta (17% of total) occurred at 5 days after wounding. The predominant isoforms were TGF-beta1 and -2 with only minor amounts of TGF-beta3 present. This is the first TGF-beta bioassay allowing semiquantitative determination of active and latent isoforms present in vivo, and our results document the significance and temporal regulation of latent TGF-beta isoform activation in wound repair.

Developmental regulation of neuronal K+ channels by target-derived TGF beta in vivo and in vitro

The functional expression of Ca2+-activated K+ channels (KCa) in developing chick ciliary ganglion (CG) neurons requires interactions with target tissues and preganglionic innervation. Here, we show that the stimulatory effects of target tissues are mediated by an isoform of TGFbeta. Exposure of cultured CG neurons to TGFbeta1, but not TGFbeta2 or TGFbeta3, caused robust stimulation of KCa. The KCa stimulatory effects of target tissue extracts were blocked by a neutralizing pan-TGFbeta antiserum but not by specific TGFbeta2 or TGFbeta3 antisera. Intraocular injection of TGFbeta1 caused robust stimulation of KCa, whereas intraocular injection of pan-TGFbeta antiserum inhibited expression of KCa in CG neurons developing in vivo. The effects of TGFbeta1 were potentiated by beta-neuregulin-1, a differentiation factor expressed in preganglionic neurons.

Contractility, transforming growth factor-beta, and plasmin in fetal skin fibroblasts: role in scarless wound healing

The early fetus responds to cutaneous wounds in a fundamentally different way from the adult; fetal wounds heal without scars. Wound contraction is a vital component of wound healing. The cytokine transforming growth factor (TGF)-beta promotes wound contraction and can be activated by the serine protease plasmin. Herein, we explored whether murine skin fibroblast contractile properties, TGF-beta, and plasmin formation are developmentally regulated. Our results showed that early fetal mouse embryonic day 15 skin fibroblasts contracted a collagen gel less, secreted less active and total TGF-beta, and generated less plasmin than either late fetal (embryonic day 17) or adult skin fibroblasts. Furthermore, there was a slight positive correlation between the formation of plasmin and the level of activation of TGF-beta. We conclude that early fetal mouse skin fibroblasts contract a collagen gel and secrete and activate TGF-beta to a lesser extent than do late fetal and adult skin fibroblasts. We speculate that the fetal skin fibroblast undergoes a developmental transition that causes wounds in mouse to contract at or after embryonic day 17. Further, this developmental transition is influenced by growth factor-fibroblast interactions and coincides with the emergence of the skin fibroblast's ability to generate plasmin and activate TGF-beta.

Circulating transforming growth factor beta 1 (TGF-beta1) in Guillain-Barré syndrome: decreased concentrations in the early course and increase with motor function

OBJECTIVE

To delineate the possible implication of the immunosuppressive cytokine transforming growth factor beta 1 (TGF-beta1) in the pathogenesis of Guillain-Barré syndrome. Guillain-Barré syndrome is a disorder that may implicate cytokines in its pathogenesis. TGF-beta1 is a potent anti-inflammatory cytokine occasionally shown to be regulated in the course of demyelinating disorders.

METHODS

The study measured circulating proinflammatory and anti-inflammatory cytokines from the progressing phase to early recovery in patients with Guillain-Barré syndrome. Plasma concentrations of TNF-alpha, IL-beta1, IL-2, IL-4, IL-6, IL-10, and TGF-beta1 were prospectively evaluated in 15 patients with Guillain-Barré syndrome every three days for the first 15 days after admission to hospital, and in 15 controls with non-inflammatory neurological diseases.

RESULTS

Concentrations of TGF-beta1 in plasma were decreased in 13115 patients (87 %) at day 1, remained low during progression and the plateau of paralysis (days 1-10), and then progressively increased up to control concentrations during early recovery (days 12-15). Concentrations of plasma TGF-beta1 correlated positively with motor function, the lowest values being e found in the most disabled patients. Concentrations of plasma TGF-beta1 were decreased before any treatment, and during treatment by either plasma exchange or intravenous immunoglobulins, plasma exchange being associated with a more pronounced decrease in TGF-beta1 at day 7. Circulating TNF-alpha concentrations were raised, as previously reported, when other cytokines were either randomly increased (IL-2, IL-6), or undetectable (IL-1, IL-4, IL-7, IL-10).

CONCLUSIONS

Down regulation of TGF-beta1 in the early course of Guillain-Barré syndrome could participate in neural inflammation.

The immunoregulatory effects of NK cells: the role of TGF-beta and implications for autoimmunity

The cytotoxic activities of natural killer (NK) cells--important in innate immunity--have received considerable attention, but NK cells also regulate T- and B-cell functions as well as hematopoiesis. Here, David Horwitz and colleagues focus on the capacity of NK cells to regulate antibody production positively and negatively, and in particular on the role of NK-cell transforming growth factor beta (TGF-beta) in downregulation of B-cell activity.

MIC-1, a novel macrophage inhibitory cytokine, is a divergent member of the TGF-beta superfamily

Macrophages play a key role in both normal and pathological processes involving immune and inflammatory responses, to a large extent through their capacity to secrete a wide range of biologically active molecules. To identify some of these as yet not characterized molecules, we have used a subtraction cloning approach designed to identify genes expressed in association with macrophage activation. One of these genes, designated macrophage inhibitory cytokine 1 (MIC-1), encodes a protein that bears the structural characteristics of a transforming growth factor beta (TGF-beta) superfamily cytokine. Although it belongs to this superfamily, it has no strong homology to existing families, indicating that it is a divergent member that may represent the first of a new family within this grouping. Expression of MIC-1 mRNA in monocytoid cells is up-regulated by a variety of stimuli associated with activation, including interleukin 1beta, tumor necrosis factor alpha (TNF-alpha), interleukin 2, and macrophage colony-stimulating factor but not interferon gamma, or lipopolysaccharide (LPS). Its expression is also increased by TGF-beta. Expression of MIC-1 in CHO cells results in the proteolytic cleavage of the propeptide and secretion of a cysteine-rich dimeric protein of Mr 25 kDa. Purified recombinant MIC-1 is able to inhibit lipopolysaccharide -induced macrophage TNF-alpha production, suggesting that MIC-1 acts in macrophages as an autocrine regulatory molecule. Its production in response to secreted proinflammatory cytokines and TGF-beta may serve to limit the later phases of macrophage activation.

Distribution of transforming growth factor beta1-binding proteins and low-affinity receptors during odontoblast differentiation in the mouse

Transforming growth factor-beta1 (TGF-beta1) was immunolocalized within differentiated odontoblasts and ameloblasts while LAP-beta1 was detected at the apicol pole of odonotoblasts and ameloblasts and in predentine. Anti-LAP-beta1 antibodies also stained the epithelial-mesenchymal junction (EMJ). Decorin was immunolocalized in young functional odonotoblasts and in both predentine and dentine. Biglycan was similarly distributed but absent from dentine. Immunostaining with anti-latent TGF-beta1 binding protein-1 (LTBP-1) showed fibrillar structures located at the EMJ and between predontoblasts and odontoblasts; at older states staining was restricted to the dental papilla and sac. Thus differentiated odonotoblasts express TGF-beta1 and in a more restricted manner decorin, biglycan and LAP-beta1; it can be assumed that TGF-beta1 is able to interact with the three molecules present in predentine. Earlier, LTBP-1 and LAP-beta1, both present at the EMJ, may contribute to odontoblast differentiation.

Biology of TGF-beta in knockout and transgenic mouse models

This paper reviews the basic biology and biochemistry of the TGF-beta isoforms including their unique serine-threonine receptors and signaling intermediates. Dysregulation of TGF-beta expression and/or receptor/signaling function have been implicated in a wide variety of pathologies. We will discuss mechanisms underlying some of these disease processes as gained from study of transgenic mice in which expression of TGF-beta 1 has either been lost by targeted deletion of its gene, is overexpressed in a tissue-specific manner, or blocked by its latency associated peptide.

Latent transforming growth factor-beta binding protein domains involved in activation and transglutaminase-dependent cross-linking of latent transforming growth factor-beta

Transforming growth factor-beta (TGF-beta) is secreted by many cell types as part of a large latent complex composed of three subunits: TGF-beta, the TGF-beta propeptide, and the latent TGF-beta binding protein (LTBP). To interact with its cell surface receptors, TGF-beta must be released from the latent complex by disrupting noncovalent interactions between mature TGF-beta and its propeptide. Previously, we identified LTBP-1 and transglutaminase, a cross-linking enzyme, as reactants involved in the formation of TGF-beta. In this study, we demonstrate that LTBP-1 and large latent complex are substrates for transglutaminase. Furthermore, we show that the covalent association between LTBP-1 and the extracellular matrix is transglutaminase dependent, as little LTBP-1 is recovered from matrix digests prepared from cultures treated with transglutaminase inhibitors. Three polyclonal antisera to glutathione S-transferase fusion proteins containing amino, middle, or carboxyl regions of LTBP-1S were used to identify domains of LTBP-1 involved in cross-linking and formation of TGF-beta by transglutaminase. Antibodies to the amino and carboxyl regions of LTBP-1S abrogate TGF-beta generation by vascular cell cocultures or macrophages. However, only antibodies to the amino-terminal region of LTBP-1 block transglutaminase-dependent cross-linking of large latent complex or LTBP-1. To further identify transglutaminase-reactive domains within the amino-terminal region of LTBP-1S, mutants of LTBP-1S with deletions of either the amino-terminal 293 (deltaN293) or 441 (deltaN441) amino acids were expressed transiently in CHO cells. Analysis of the LTBP-1S content in matrices of transfected CHO cultures revealed that deltaN293 LTBP-1S was matrix associated via a transglutaminase-dependent reaction, whereas deltaN441 LTBP-1S was not. This suggests that residues 294-441 are critical to the transglutaminase reactivity of LTBP-1S.