Transforming growth factor beta alters plasminogen activator activity in human skin fibroblasts

Gene Therapy for Cardiovascular Disease: Basic Research and Clinical Prospects

In recent years, the vital role of genetic factors in human diseases have been widely recognized by scholars with the deepening of life science research, accompanied by the rapid development of gene-editing technology. In early years, scientists used homologous recombination technology to establish gene knock-out and gene knock-in animal models, and then appeared the second-generation gene-editing technology zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) that relied on nucleic acid binding proteins and endonucleases and the third-generation gene-editing technology that functioned through protein-nucleic acids complexes-CRISPR/Cas9 system. This holds another promise for refractory diseases and genetic diseases. Cardiovascular disease (CVD) has always been the focus of clinical and basic research because of its high incidence and high disability rate, which seriously affects the long-term survival and quality of life of patients. Because some inherited cardiovascular diseases do not respond well to drug and surgical treatment, researchers are trying to use rapidly developing genetic techniques to develop initial attempts. However, significant obstacles to clinical application of gene therapy still exists, such as insufficient understanding of the nature of cardiovascular disease, limitations of genetic technology, or ethical concerns. This review mainly introduces the types and mechanisms of gene-editing techniques, ethical concerns of gene therapy, the application of gene therapy in atherosclerosis and inheritable cardiovascular diseases, in-stent restenosis, and delivering systems.

Differential uPA Expression by TGF-β1 in Gingival Fibroblasts

Transforming Growth Factor-β1 (TGF-β1) plays a key role in connective tissue remodeling and inflammation. Under pathological conditions, like periodontal disease, fibroblasts may display an altered response to this growth factor. To investigate this question, we have studied whether TGF-β1 may differentially regulate the expression of urokinase at the protein level in primary cultures of fibroblasts derived from healthy gingiva, granulation tissue from gingival wounds, and chronic periodontal disease. We observed that TGF-β1 may repress urokinase expression in healthy gingival fibroblasts and promote its production in granulation-tissue fibroblasts. A significant correlation was found between expression of the myofibroblast marker α-smooth-muscle actin and stimulation of urokinase production by TGF-β1. Immunostaining of gingival wounds showed that myofibroblasts were involved in urokinase production. TGF-β1-stimulated urokinase expression was blocked after inhibition of the c-jun-NH2 terminal kinase signaling pathway. We propose that stimulation of urokinase production by TGF-β1 is involved in the responses of activated fibroblasts to tissue injury.

Regional changes in elastic fiber organization and transforming growth factor β signaling in aortas from a mouse model of marfan syndrome

In Marfan Syndrome (MFS), development of thoracic aortic aneurysms (TAAs) is characterized by degeneration of the medial layer of the aorta, including fragmentation and loss of elastic fibers, phenotypic changes in the smooth muscle cells, and an increase in the active form of transforming growth factor-β (TGFβ), which is thought to play a major role in development and progression of the aneurysm. We hypothesized that regional difference in elastic fiber fragmentation contributes to TGFβ activation and hence the localization of aneurysm formation. The fibrillin-1-deficient mgR/mgR mouse model of MFS was used to investigate regional changes in elastin fiber fragmentation, TGFβ activation and changes in gene expression as compared to wild-type littermates. Knockdown of Smad 2 and Smad 3 with shRNA was used to determine the role of the specific transcription factors in gene regulation in aortic smooth muscle cells. We show increased elastin fiber fragmentation in the regions associated with aneurysm formation and altered TGFβ signaling in these regions. Differential effects of Smad 2 and Smad 3 were observed in cultured smooth muscle cells by shRNA-mediated knockdown of expression of these transcription factors. Differential signaling through Smad 2 and Smad 3 in regions of active vascular remodeling likely contribute to aneurysm formation in the mgR/mgR model of MFS. Increased elastin fiber fragmentation in these regions is associated with these changes as compared to other regions of the thoracic aorta and may contribute to the changes in TGFβ signaling in these regions.

Connective tissue disorders and cardiovascular complications: the indomitable role of transforming growth factor-beta signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that cosegregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic root dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. Given the evidence of increased transforming growth factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in this relationship. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, heritable connective tissue syndromes related to TGF-β receptor (TGFBR) mutations, and discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Pathophysiology of thoracic aortic aneurysm (TAA): is it not one uniform aorta? Role of embryologic origin

Thoracic aortic aneurysm (TAA) is a clinically silent and potentially fatal disease whose pathophysiology is poorly understood. Application of data derived from animal models and human tissue analysis of abdominal aortic aneurysms may prove misleading given current evidence of structural and biochemical aortic heterogeneity above and below the diaphragm. Genetic predisposition is more common in TAA and includes multi-faceted syndromes such as Marfan, Loeys-Dietz, and type IV Ehlers-Danlos as well as autosomal-dominant familial patterns of inheritance. Investigation into the consequences of these known mutations has provided insight into the cell signaling cascades leading to degenerative remodeling of the aortic medial extracellular matrix (ECM) with TGF-β playing a major role. Targeted research into modifying the upstream regulation or downstream effects of the TGF-β1 pathway may provide opportunities for intervention to attenuate TAA progression.

Biological features of thoracic aortic diseases. Where are we now, where are we heading to: established and emerging biomarkers and molecular pathways

Thoracic aortic aneurysms (TAAs) and aortic dissections (ADs) are among the main causes of mortality and morbidity in Western countries. For this reason, the diagnosis, prevention and prediction of TAAs and ADs have become a very active area of research; in fact, it is important to monitor and predict the evolution of these diseases over time. It is also critical, in cases of doubtful diagnosis, to receive some guidance from biochemical assays, particularly in the case of ADs. Although biological testing for disease prediction has already been discussed several times, the role of biomarkers in TAAs and ADs is still under discussion for routine patient screening, periodical follow-up or for prompt diagnosis in emergency conditions. In this review, we update the current knowledge and new trends regarding the role of biomarkers in thoracic aortic diseases, focusing on established and emerging biomarkers in the fields of genetics, inflammation, haemostasis and matrix remodelling as well as on substances released upon cell damage. Other than D-dimer, a sensitive but not a specific marker for the diagnosis of AD that has been widely tested by several authors and currently seems a viable option in ambiguous cases, the remaining markers have been most frequently assessed in limited or mixed patient populations. This currently precludes their widespread adoption as diagnostic or prognostic tools, even if many of these markers are conceptually promising. In years to come, we expect that future studies will further clarify the diagnostic and prognostic features of several established and emerging biomarkers that, to date, are still in the translational limbo separating biological discovery from a practical clinical role.

The pathogenesis of aortopathy in Marfan syndrome and related diseases

Marfan syndrome is a systemic connective tissue disorder that is inherited in an autosomal-dominant pattern with variable penetrance. Although there are many clinical manifestations of this disease, the most life threatening are cardiovascular complications, including mitral valve prolapse and aortic root aneurysm. When the primary defect was discovered in the fibrillin-1 gene, it was hypothesized that mutations in fibrillin-1 resulted in a weakened and disordered elastic architecture. However, recent evidence has suggested that the Marfan syndrome is caused by more than just a disordered microfibril matrix. Interest was stimulated when it was discovered that fibrillin-1 mutations enhanced the release of sequestered latent transforming growth factor-beta, a well-described mediator of vascular remodeling. This article focuses on the pathophysiology of aortopathy in the Marfan syndrome and related diseases, with special emphasis on the role of transforming growth factor-beta in mediating the pathogenesis of this disease.

Transforming growth factor-beta signaling in thoracic aortic aneurysm development: a paradox in pathogenesis

Thoracic aortic aneurysms (TAAs) are potentially devastating, and due to their asymptomatic behavior, pose a serious health risk characterized by the lack of medical treatment options and high rates of surgical morbidity and mortality. Independent of the inciting stimuli (biochemical/mechanical), TAA development proceeds by a multifactorial process influenced by both cellular and extracellular mechanisms, resulting in alterations of the structure and composition of the vascular extracellular matrix (ECM). While the role of enhanced ECM proteolysis in TAA formation remains undisputed, little attention has been focused on the upstream signaling events that drive the remodeling process. Recent evidence highlighting the dysregulation of transforming growth factor-beta (TGF-beta) signaling in ascending TAAs from Marfan syndrome patients has stimulated an interest in this intracellular signaling pathway. However, paradoxical discoveries have implicated both enhanced TGF-beta signaling and loss of function TGF-beta receptor mutations, in aneurysm formation; obfuscating a clear functional role for TGF-beta in aneurysm development. In an effort to elucidate this subject, TGF-beta signaling and its role in vascular remodeling and pathology will be reviewed, with the aim of identifying potential mechanisms of how TGF-beta signaling may contribute to the formation and progression of TAA.

Transforming growth factor-beta3 affects plasminogen activator inhibitor-1 expression in fetal mice and modulates fibroblast-mediated collagen gel contraction

For over two decades, the precise role of transforming growth factor-beta (TGF-beta) isoforms in scarless healing of mammalian fetal skin wounds has generated much interest. Although their exact role remains to be established, it has been suggested that high TGF-beta3 activity may correlate with a scarless phenotype. Previously, we showed that plasminogen activator inhibitor-1 (PAI-1), a known TGF-beta downstream molecule and marker of fibrosis, is also developmentally regulated during fetal skin development. In this study, the relationship between TGF-beta3 and PAI-1 was investigated using embryonic day 14.5 TGF-beta3 knockout (ko) mice. The results showed increased PAI-1 expression in the epidermis and dermis of ko mice, using an ex vivo limb-wounding study. Furthermore, increased PAI-1 expression and activity was seen in embryo extracts and conditioned media of ko dermal fibroblasts. When TGF-beta3 knockout fibroblasts were placed into three-dimensional collagen matrices, they were found to have decreased collagen gel contraction, suggesting altered cell-matrix interaction. These findings provide a further avenue for the interactive role of TGF-beta3 and PAI-1 during fetal scarless repair.

Plasminogen activator inhibitor-1 is elevated, but not essential, in the development of bleomycin-induced murine scleroderma

Accumulative data have demonstrated that plasminogen activator inhibitor-1 (PAI-1) plays an important role in the extracellular matrix metabolism; however, the involvement of PAI-1 in scleroderma has not been fully elucidated. In this study, we investigated the role of PAI-1 in bleomycin-induced murine scleroderma. 100 microg of bleomycin was injected subcutaneously to the back skin of C3H/HeJ mice on alternate day for 4 weeks. Histopathological findings revealed that PAI-1 was positive in macrophage-like cells and fibroblastic cells in the dermis, in parallel with the induction of dermal sclerosis. PAI-1 mRNA expression in the whole skin was up-regulated at 1 and 4 weeks. The production of active PAI-1 protein in the lesional skin was significantly increased 3 and 4 weeks after bleomycin treatment. Next, we examined whether dermal sclerosis is induced by bleomycin in PAI-1-deficient (PAI-1-/-) mice. 10 microg of bleomycin was subcutaneously injected to PAI-1-/- and wild type (WT) mice 5 days per week for 4 weeks. Histological examination revealed that dermal sclerosis was similarly induced even in PAI-1-/- as well as WT mice. Dermal thickness and collagen contents in the skin were significantly increased by bleomycin injection in both PAI-1-/- and WT mice, and the rate of increase was similar. These data suggest that PAI-1 plays an important role, possibly via TGF-beta pathway activation. However, the fact that PAI-1 deficiency did not ameliorate skin sclerosis suggest that PAI-1 is not the essential factor in the development of bleomycin-induced scleroderma, and more complex biochemical effects other than PA/plasmin system are greatly suspected.

Elevated aqueous humour tissue inhibitor of matrix metalloproteinase-1 and connective tissue growth factor in pseudoexfoliation syndrome

BACKGROUND/AIMS

Pseudoexfoliation syndrome (PXF) was recently found to be associated with increased expression of transforming growth factor beta(1) (TGFbeta(1)) in the aqueous humour. As concern has been raised regarding anti-TGFbeta therapy, which can potentially disrupt the maintenance of anterior chamber associated immune deviation, the authors explored the levels of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), matrix metalloproteinase-9 (MMP-9), and connective tissue growth factor (CTGF) in aqueous humour to determine if these may represent alternative therapeutic targets.

METHODS

Aqueous humour samples were collected from patients who underwent routine cataract surgery. All patients were categorised into three main groups-PXF, uveitis, and control. The PXF group was further subcategorised into three grades based on the density of the exfoliative material observed on biomicroscopy, as well as the presence or absence of glaucoma. TIMP-1, MMP-9, and CTGF levels were measured using specific enzyme immunoassays (ELISA).

RESULTS

Eyes with PXF had significantly higher aqueous humour TIMP-1 concentration (n = 56, mean (SE), 9.76 (1.10) ng/ml) compared with controls (n = 112, 5.73 (0.43) ng/ml, p<0.01). Similarly, the CTGF level in PXF eyes (n = 36, 4.38 (0.65) ng/ml) was higher than controls (n = 29, 2.35 (0.46) ng/ml, p<0.05). Further, the CTGF concentration in the PXF glaucoma group is significantly higher compared with PXF eyes without glaucoma (6.03 (1.09) ng/ml v 2.73 (0.45) ng/ml, p<0.01). The MMP-9 levels were low and below detection limit in all PXF and control samples with no statistical difference between groups.

CONCLUSION

A raised TIMP-1 level and a low MMP-9 level in aqueous humour of PXF eyes may imply a downregulation in proteolytic activity. The increased CTGF concentration supports the proposed fibrotic pathology of PXF. Regulation of MMP/TIMP expression and anti-CTGF therapy may offer potential therapeutic avenues for controlling PXF associated ocular morbidity.

Latent TGF-beta binding proteins: extracellular matrix association and roles in TGF-beta activation

Transforming growth factor betas (TGF-betas) are multifunctional and pleiotropic growth factors. Their major effects include inhibition of cell proliferation and enhancement of extracellular matrix production. TGF-betas are secreted from cells as latent complexes, consisting of mature dimeric growth factor, the latency-associated propeptide (LAP), and a distinct gene product, latent TGF-beta binding protein LTBP. The secreted complex is targeted to specific locations in the extracellular matrix by the appropriate LTBP. The latent complex needs subsequently to be activated. Most studies describing biological effects of TGF-beta have been carried out in cell cultures using high concentrations of active, soluble TGF-beta, where appropriate targeting of the growth factor is missing. However, TGF-beta is produced and secreted in vivo as a latent complex in a specific and targeted manner. Various experimental approaches have convincingly shown the importance of the activation of latent TGF-beta, as well as the importance of LTBPs as targeting molecules of the effects of TGF-beta. Essential steps in the activation appear to be cellular recognition of extracellular matrix-associated LTBPs and subsequent recognition of the associated latent TGF-beta. Cell recognition by specific molecules like integrins and proteolytic events involving plasminogen activation evidently play multifaceted roles in the regulation of TGF-beta activation.

JNK regulates autocrine expression of TGF-beta1

The c-Jun NH2-terminal kinase (JNK) has been implicated in the function of transforming growth factor beta (TGF-beta). To test the role of JNK, we examined the effect of compound disruption of the murine genes that encode the ubiquitously expressed isoforms of JNK (Jnk1 and Jnk2). We report that JNK-deficient fibroblasts isolated from Jnk1-/- Jnk2-/- mice constitutively express TGF-beta1. Complementation studies demonstrate that JNK is a repressor of Tgf-beta1 gene expression. This mechanism of regulation of TGF-beta1 expression by JNK represents an unexpected form of cross-talk between two important signaling pathways. Together, these data demonstrate that the JNK pathway may contribute to the regulation of autocrine TGF-beta1-mediated biological responses in vivo.

Expression of Fibrinolytic and Coagulation Factors in Cocultured Human Endothelial and Smooth Muscle Cells

Interactions between endothelial cells and smooth muscle cells are interesting from a tissue-engineering point of view. We have developed a coculture system that allows direct contact between these two cell types. The fibrinolytic factors PAI-1, tPA, and uPA and the coagulation factor TF, were studied at the gene level by RT-PCR and at the protein level by ELISA. Significant changes of all studied factors were seen at the gene level in cocultured endothelial cells. tPA and TF were upregulated 4- and 7-fold, respectively, and PAI-1 and uPA were downregulated 4- and 1.5-fold, respectively, compared with single-cultured controls. In cocultured smooth muscle cells alterations of PAI-1 and TF were significant, with a 1.5-fold upregulation of PAI-1 and a 2.5-fold downregulation of TF. Results at the protein level mirrored the gene expression results. These findings indicate that cocultured endothelial cells are rendered both hypercoagulative and hyperfibrinolytic.

Plasminogen activator/plasmin system: a major player in wound healing?

The role of the plasminogen activator/plasmin system in fibrinolysis has been well established. Indeed, clinicians worldwide have successfully utilized recombinant tissue-type plasminogen activator as first-line treatment of acute myocardial infarction for almost 2 decades. Outside the field of cardiology, there has been increasing excitement regarding the possible contribution of this system in many other important biological processes, including cell adhesion, cell migration, cell-cell signaling, tumor invasion and metastasis, ovulation, and wound healing. In this review, we present evidence in the current literature that the plasminogen activator/plasmin system does have a role in wound healing, looking at both normal and abnormal healing. Furthermore, the invaluable insights provided by numerous transgenic animal experiments are summarized.

Stimulation of collagen production by transforming growth factor-beta1 during differentiation of cardiac fibroblasts to myofibroblasts

The aim of the present study was to elucidate how transforming growth factor-beta(1) (TGF-beta(1)) can stimulate collagen deposition in cardiac tissue by interstitial cells via stimulation of fibroblasts, via myofibroblasts, or via differentiation of fibroblasts to myofibroblasts. The dose- and time-dependent stimulation of collagen production and of expression of alpha-smooth muscle actin (alpha-SMA), a marker of myofibroblasts, was studied in cultures of second-passage adult rat cardiac fibroblasts. The TGF-beta(1)-stimulated collagen production is positively correlated (r=0.68, P<0.001) with the appearance of alpha-SMA. Only at high concentrations (40 to 600 pmol/L) and after a long time (24 to 48 hours) of incubation, TGF-beta(1) increases the collagen production and stimulates the differentiation of fibroblasts to myofibroblasts. The maximal stimulation of the collagen production (2-fold, P<0.001) observed after incubation of cultures of fibroblasts with 600 pmol/L TGF-beta(1) for 48 hours is accompanied by a maximal stimulation of alpha-SMA expression (3.5-fold, P<0.001), when cultures consist mainly of myofibroblasts. The stimulation of collagen production cannot be reversed either after additional incubation of TGF-beta(1)-stimulated second-passage cultures for 2 days or in their offspring in the next third passage after incubation for 7 days without TGF-beta(1). The increased collagen production in these third-passage cultures cannot be further stimulated by TGF-beta(1). Our data suggest that TGF-beta(1)-stimulated collagen production in cultures of adult rat cardiac ventricular fibroblasts cannot be explained by a direct stimulation of the collagen production either in fibroblasts or in myofibroblasts. Instead, TGF-beta(1) induces the differentiation of fibroblasts to myofibroblasts, which have a higher activity for collagen production than fibroblasts.

Connective tissue growth factor: an attractive therapeutic target in fibrotic renal disease

Despite diverse initiating insults, glomerulosclerosis and tubulointerstitial fibrosis are pathological features common to most forms of progressive renal disease. Control of systemic hypertension and blockade of the renin-angiotensin system ameliorate the rate of progression of chronic renal disease; however they generally fail to completely arrest the scarring process. While the chain of events leading to scarring are still being defined, TGF-beta is a cytokine that plays a pivotal role in the pathogenesis of glomerulosclerosis and tubulointerstitial fibrosis [1]. Given the pleiotropic effects of TGF-beta, significant attention has focused on the potential of its downstream mediators as therapeutic targets. Connective tissue growth factor (CTGF) is a member of the CCN gene family, which includes CyR61 (cysteine rich 61), Nov (Nephroblastoma overexpressed) and the WISP family (for review see [2,3,4]). These immediate-early genes coordinate complex biologic processes during differentiation and tissue repair [5]. Increased expression of CTGF has been detected in experimental and human renal fibrosis where it correlates with glomerulosclerosis and the degree of tubulointerstitial fibrosis [6]. In these settings CTGF expression is regulated at least in part by TGF-beta. This review details the biology of CTGF with specific reference to its potential as a therapeutic target in renal fibrosis.

Developmental differences in the expression and modulation of extracellular matrix proteases and inhibitors in mouse skin fibroblasts

To investigate developmental differences in the wound repair process between fetal and adult skin fibroblasts, we studied the expression of plasminogen activator, plasminogen activator inhibitor, matrix metalloproteinase, and tissue inhibitor of metalloproteinase in E-15, E-17, newborn and adult mouse skin fibroblasts cultured within three dimensional matrices of either collagen or fibrin. Fibrin overlay and reverse overlay analyses revealed that mouse skin fibroblasts secreted tissue plasminogen activator and type1 plasminogen activator inhibitor. However, only E-15 and E-17 fibroblasts secreted the active form of tissue plasminogen activator, while in newborn and adult fibroblasts tissue plasminogen activator was conjugated to type1 plasminogen activator inhibitor. Only adult fibroblasts expressed a high level of active type1 plasminogen activator inhibitor. Gelatin zymography revealed that the predominant matrix metalloproteinase secreted by all the mouse fibroblasts was gelatinase A (matrix metalloproteinase -2). Matrix metalloproteinase -2 was partially activated in the adult fibroblasts cultured within a collagen matrix. The tissue inhibitor of metalloproteinase-2 was expressed by all fibroblasts, but levels were highest in the newborn and adult fibroblasts. When E-15 fibroblasts were cultured within a fibrin matrix, tissue plasminogen activator was downregulated. Transforming growth factor-betadownregulated tissue plasminogen activator while upregulating type1 plasminogen activator inhibitor, and platelet-derived growth factor enhanced tissue plasminogen activator expression in E-15 fibroblasts. Therefore, plasminogen activator and its inhibitor, and matrix metalloproteinase and its associated tissue inhibitor are differentially expressed in fetal and adult fibroblasts, and their expression is controlled by extracellular matrix components and growth factors present in wounds.

Transforming growth factor beta 1 and sodium butyrate differentially modulate urokinase plasminogen activator and plasminogen activator inhibitor-1 in human breast normal and cancer cells

The effects of transforming growth factor beta 1 (TGF-beta1) and sodium butyrate on cell proliferation and the urokinase plasminogen activator (uPA) system were examined in normal human breast epithelial cells (HBECs) and in a breast cancer cell line, MDA-MB-231. In HBECs, TGF-beta1 inhibited cell proliferation and uPA activity, while it augmented plasminogen activator inhibitor-1 (PAI-1) antigen level. Sodium butyrate inhibited both cell proliferation and uPA activity but did not affect the level of PAI-1. In MDA-MB-231, TGF-beta1 had no effect on cell proliferation but increased uPA activity and PAI-1 antigen level; sodium butyrate inhibited both cell proliferation and uPA activity but had no effect on PAI-1 level. Moreover, in the presence of plasminogen, cell detachment could be modulated by the level of cell-associated uPA. Our results indicate (1) that the effects of TGF-beta1 on cell growth can be dissociated from its effects on the uPA/PAI system; (2) that, while TGF-beta1 is a potent inhibitor of cell proliferation and uPA activity in normal cells, it may promote invasion and metastasis of tumour cells by increasing uPA activity and PAI-1 levels; and (3) that sodium butyrate offers a potential approach to preventing tumour development by inhibiting both cell proliferation and invasion.

Cytoskeleton regulates expression of genes for transforming growth factor-beta 1 and extracellular matrix proteins in dermal fibroblasts

Cytoskeleton not only controls cell morphology but also regulates cell growth, migration, differentiation, and gene expression, events which are fundamental to embryogenesis, carcinogenesis, and wound healing. We have recently reported that reorganization of cytoskeleton induces expression of mRNA for transforming growth factor-beta 1 (TGF-beta 1), collagenase, and tissue inhibitor of metalloproteinase-I (TIMP-I) in dermal fibroblasts. In this report we have examined the role of gene transcription in this induction. As judged by nuclear run-on assay, trypsin, EGTA (ethylene glycol-bis (beta-aminoethyl ether) N, N, N', N', tetra-acetic acid), or cytochalasin C (Chs) increased the rate of transcription of the TGF-beta 1 gene by 2.0, 2.7, and 1.6 fold, respectively, and of the collagenase gene by 5.3, 6.2, and 3.3 fold. The rate of transcription of the TIMP-I gene was increased by trypsin (4.3 fold) or EGTA (3.8 fold) but unaffected by Chs. Cytochalasin induced an increase in the rate of transcription of procollagen I (alpha 1), procollagen I (alpha 2), and fibronectin genes by 1.4, 1.5, and 1.9 fold respectively, while trypsinization or EGTA treatment had no or little effects on these gene. Since transcription of the TGF-beta 1 gene is believed to be largely governed by the activating protein 1 (AP1) complex, we also examined the expression of mRNA for c-fos and c-jun protoon-coproteins. Trypsinization induced rapid (within 30 min) and transient expression of c-fos mRNA. A 2.4 fold increase in c-jun mRNA was apparent after 4 hr and persisted for at least 24 hr. Actinomycin D (Act D) suppressed the induction of TGF-beta 1 mRNA by Chs but had less effect on the TGF-beta 1 mRNA in trypsinized cells which had been replated for 4 hr, suggesting that the half life of TGF-beta 1 mRNA is reduced in cells with a disassembled cytoskeleton. Simultaneous treatment with Chs and cycloheximide (Cxm) resulted in a superinduction of TGF-beta 1 mRNA by 88 +/- 23% (n = 4, P < 0.05), which was abrogated by preexposure to Act D. In contrast, the induction of collagenase mRNA by Chs was totally blocked by Cxm, indicating that the Cxm-mediated superinduction is selective and that protein synthesis is required for induction of this mRNA. Our results suggest that the activities of genes for proteins involved in the structure (Type I collagen and fibronectin), turnover (collagenase and TIMP-1) and regulation (TGF-beta 1) of extracellular matrix (ECM), are all governed at least in part by the status of the cytoskeleton. Since the cytoskeleton is reorganized during cell division, migration, and differentiation, these results may have implications for the regulation of ECM during such processes as embryogenesis, carcinogenesis, and wound healing.

The differential regulation and secretion of proteinases from fetal and neonatal fibroblasts by growth factors

One of the major differences between fetal and adult wound repair is the unique ability of fetal wounds to heal without scarring. Since scar formation is a function of extracellular matrix deposition, the regulation of this component is fundamental in tissue remodeling. In this study, we have characterized the differences in the secretion of matrix-degrading proteases, namely urokinase plasminogen activator and gelatinase A and B, from fetal and neonatal fibroblasts. In addition, we examined the modulation of these protease levels by growth factors known to be important in wound repair. The results indicate that the secretion of these proteases differ significantly between the two cell types. The levels of urokinase plasminogen activator and its inhibitor were notably higher in media conditioned by neonatal fibroblasts in comparison to fetal samples. In contrast, the basal level of gelatinase A was comparable in both cell types, whilst the level of gelatinase B was elevated in the fetal fibroblasts. Transforming growth factor-beta 1 reduced the level of urokinase plasminogen activator and stimulated the secretion of plasminogen activator inhibitor-1 and progelatinase B in both neonatal and fetal fibroblasts. However, only progelatinase A and an activated form of gelatinase B were significantly elevated in fetal fibroblasts. In contrast, platelet-derived growth factor stimulated urokinase plasminogen activator, its inhibitor and both gelatinase A and B, an effect which was more apparent in fetal fibroblasts. This difference in protease regulation may be reflected in the differing rate and quality of tissue remodeling observed during adult vs fetal wound repair.

Serum albumin is a specific inhibitor of apoptosis in human endothelial cells

Excess blood vessels are removed by apoptosis of endothelial cells, however, the signals responsible for this have not been defined. Apoptosis of cultured human umbilical vein endothelial cells is induced by deprivation of serum or adhesion. In this paper, apoptosis in human umbilical vein and microvascular endothelium was induced by deprivation of serum and or adhesion. Apoptosis was confirmed on the basis of morphology, ultrastructure and internucleosomal cleavage of DNA. Loss of endothelial adhesion was found to be an early event in cultured endothelial cell apoptosis and was exploited to quantitate apoptosis. The effect of: bovine serum albumin; human serum albumin; recombinant human albumin; dithiothreitol reduced human and bovine albumin; CNBr treated human and bovine albumin as well as ovalbumin upon endothelial apoptosis was determined. Native bovine and human albumin as well as recombinant human material inhibited apoptosis at physiological concentrations with identical dose response curves in both umbilical vein and microvascular cells. Dithiothreitol treatment destroyed all protective activity while bovine but not human albumin was partially inactivated by CNBr treatment. The unrelated protein ovalbumin was not protective. Albumin did not inhibit apoptosis if cells were also deprived of adhesion. The data suggest that albumin is a specific inhibitor of human endothelial apoptosis but does not protect cells also deprived of adhesion. Reduced supply of albumin to endothelium in poorly perfused blood vessels may provide a mechanism for the removal of excess blood vessels in remodelling tissues. Also, the failure of albumin to protect endothelial cells deprived of adhesion from apoptosis may reflect the need to remove potentially micro-embolic cells detached due to trauma.

Elevated levels of plasminogen activator inhibitor-1 may account for the altered fibrinolysis by keloid fibroblasts

Using a 3-dimensional fibrin gel model system simulating fibroplasia of wound repair, we investigated the interaction between keloid fibroblasts and fibrin matrix and compared it with that of normal fibroblasts. Normal skin fibroblasts caused fibrin gel degradation under serum-free conditions, whereas keloid fibroblasts did not cause microscopically detectable gel degradation. Fibrin gel degradation occurred through plasmin-mediated fibrinolysis, which was initiated by fibroblasts exhibited high uPA but low plasminogen activator inhibitor-1 (PAI-1) activities, and transforming growth factor-beta 1 prevented fibrinolysis of normal fibroblasts by upregulating PAI-1 while downregulating uPA activities. In contrast, keloid fibroblasts exhibited an intrinsically high level of PAI-1 and a low level of uPA. This change in the ratio of activator and inhibitor activities was attributed to altered fibrin degradation by keloid fibroblasts. The PAI-1 increase was also demonstrated at the RNA level by Northern analysis. In terms of the pivotal role of the plasmin/plasminogen activator system in matrix remodeling, the elevated PAI-1 level exhibited by keloid fibroblasts may have significant consequences not only in altered fibrin degradation, but also in subsequent repair steps that lead to keloids and fibrosis.

Engineering, expression and renaturation of targeted TGF-beta fusion proteins

This study reports the expression, purification, and renaturation of biologically active Transforming Growth Factor-beta 1 (TGF-beta 1) fusion proteins from Escherichia coli (E. coli). A prokaryotic expression vector was engineered to produce tripartite fusion proteins consisting of (i) a purification tag, (ii) a protease-sensitive linker/collagen binding domain, and (iii) a cDNA sequence encoding the active fragment of human TGF-beta 1. The expressed fusion proteins TGF-B1-F1 and TGF-B1-F2, located in inclusion bodies, were solubilized with 8 M urea and renatured using a glutathione redox-coupled system and protracted dialysis under several experimental conditions. The purification of the recombinant proteins was achieved by binding the His-tag of the fusion proteins on a Ni-NTA metal chelate column. The biological activity of the recombinant growth factor was demonstrated by its ability to inhibit mink lung (Mv1Lu) cell proliferation and/or to stimulate proliferation of NIH-3T3 mouse fibroblasts, where purified human platelet TGF-beta 1 served as a positive control. Purified TGF-B1-F1 and TGF-B1-F2 (collagen-binding) constructs exhibited anti-proliferative activities comparable to purified platelet TGF-beta 1, but at lower specific activities. Binding of the renatured TGF-B1-F2 fusion protein to collagen was demonstrated by stable binding on a collagen-conjugated Sephadex-G15 column. The high affinity binding was also demonstrated by the binding of 3H-collagen to the TGF-B1-F2 protein immobilized on a Ni-NTA column. The TGF-B1-F2 fusion protein bound to collagen coated surfaces with high affinity but exhibited comparatively lower biological activity than the fusion protein in solution, suggesting a potentially latent configuration. Taken together, these results demonstrate that biologically active TGF-beta 1 fusion proteins can be recovered from transformed bacteria by oxidative refolding; thus, providing a means for its high-yield production, purification, and renaturation from microorganisms. Furthermore, these results support the concept that auxiliary domains may be used to modulate and/or target TGF-beta 1 for specific applications.

Transforming growth factor-beta system and its regulation by members of the steroid-thyroid hormone superfamily

TGF-beta s and their receptors are expressed ubiquitously, and they act as key regulators of many aspects of cell growth, differentiation, and function. Steroid action on target tissues is often associated with increase in TGF-beta isoforms. Regulation of TGF-beta expression and activation is crucial for normal development and growth control. The loss of responsiveness of different tumor cells to the antiproliferative effects of TGF-beta is a common feature in carcinogenesis. Multiple changes are required for the cells to gain complete resistance to TGF-beta growth inhibition (Fynan and Reiss, 1993; Kimchi et al., 1988; Samuel et al., 1992). Although many tumor cells are not growth inhibited by TGF-beta, they respond to TGF-beta treatment by changes in the expression of matrix components and enhanced proteolytic activity (KeskiOja et al., 1988). Agents that induce TGF-beta production in target tissues can have a chemopreventive or chemotherapeutic value for the management of epithelial malignancies. Conversely, data supporting a positive role for TGF-beta in established tumor progression are beginning to emerge (Arteaga et al., 1993a,b; Barrett-Lee et al., 1990; Arrick et al., 1992 ; E. A. Thompson et al., 1991). In later stages of tumor development, cell proliferation is often not inhibited by TGF-beta, and tumor cells secrete large amounts of this growth factor (Fynan and Reiss, 1993). In vivo TGF-beta secreted by tumor or stromal cells can influence host responses such as a natural killer cell function and thus indirctly support tumor cell viability (Arteaga et al., 1993b). TGF-beta may also affect tumor growth indirectly by stromal effects and promotion of angiogenesis. TGF-beta may also be involved in the progression of breast tumors from the steroid-sensitive to steroid-insensitive state (King et al., 1989). Understanding of the net effect of TGF-beta in different stages of tumor development is critical for the evaluation of its therapeutic value in cancer treatment.

Expression of transforming growth factor beta in the embryonic avian lens coincides with the presence of mitochondria

During their maturation, lens cells lose all membrane bound organelles, including mitochondria. In chicken embryos this process begins in the central lens fibers beginning around embryonic day 12 (E12). Transforming growth factor beta (TGF beta) is a multipotent growth modulator thought to play a role in numerous developmental processes. TGF beta 1 has been localized to mitochondria in rat liver cells and muscle cells. In the present study, we examined the expression of TGF beta isoform mRNAs and proteins during chicken embryonic lens development. PCR analysis demonstrated TGF beta 2 and TGF beta 3 transcripts in the lens epithelium and fibers throughout pre- and post-hatching development. TGF beta isoforms were detected throughout the lens epithelium and fibers early in development (E6). However by E19, the distribution of TGF beta 2 and TGF beta 3 transcripts and proteins coincided with regions of the lens that contained mitochondria. In addition, intense TGF beta staining was observed in the basal portions of the equatorial epithelial cells, a region with abundant mitochondria. Transcripts for TGF beta 1 and TGF beta 4 were not detected in any tissue or time frame examined. Similarly, no immunostaining for TGF beta 1 was observed.

Alteration in cell morphology triggers transforming growth factor-beta 1, collagenase, and tissue inhibitor of metalloproteinases-I expression in normal and hypertrophic scar fibroblasts

Using immunocytochemistry and Northern blot analysis, we investigated the role of cell morphology and reorganization of the cytoskeleton in the expression of transforming growth factor-beta 1 (TGF-beta 1) in human dermal fibroblasts. Disruption of the cytoskeleton was induced by three different agents--trypsin, ethyl-eneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), or cytochalasin--and was confirmed by staining with rhodamine-labeled phalloidin. Immunocytochemical staining with antibodies specific for TGF-beta 1 revealed a cell-shape-related induction of TGF-beta 1. Northern blot analysis of total RNA showed a significant increase in the expression of TGF-beta 1 mRNA as early as 4 h and peaking at 12 h after disruption of the cytoskeleton. Quantitative analysis of TGF-beta 1 mRNA expression at 4 h after treatment with trypsin, EGTA, or cytochalasin C showed increases of 2.6-, 3.3-, and 2.6-fold, respectively. Disruption of the cytoskeleton by trypsin, EGTA, or cytochalasin C increased mRNA for collagenase by 3.8-fold, 2.3-fold, or 2.5-fold, respectively. The expression of mRNA for tissue inhibitor of metalloproteinases I (TIMP-I) also showed a 3.2-fold increase by trypsin, a 3.6-fold increase by EGTA, and a 2.5-fold increase by cytochalasin C. Cell-shape-related induction of TGF-beta 1, collagenase, and TIMP-I genes appears to be selective, as the levels of mRNA for fibronectin and type I procollagen were not significantly altered. These data suggest that gene expression of TGF-beta 1, collagenase, and TIMP-I is governed by the status of the cytoskeleton microfilament organization, which may be a mechanism of gene regulation during cell division, migration, and differentiation, events fundamental to wound healing.

Effect of endothelial cells and transforming growth factor-beta 1 on cultured vascular smooth muscle cell growth patterns

Smooth muscle cells (SMCs) cultured alone exhibit characteristic "hill and valley" macroscopic growth features. We studied smooth muscle cells cocultured with endothelial cells and the effect of transforming growth factor beta 1 on smooth muscle cells: Bovine smooth muscle cells were plated on 13 microns-thick semipermeable membranes. Smooth muscle cells were cultured either alone (in Dulbecco's Modified Eagles Media/2.5% calf serum, four wells/group); with neutralizing anti-transforming growth factor-beta 1 antibody (10 micrograms/ml); with the protease inhibitor aprotinin (prevents plasmin-mediated activation of transforming growth factor-beta 1, 200 mg/ml); or in the presence of confluent bovine endothelial cells cocultured on the opposite side of the membrane before plating smooth muscle cells. After 72 hours in culture smooth muscle cell organizational growth characteristics were examined by light microscopy. Hill and valley formation by smooth muscle cells resulted in areas of the membrane becoming devoid of smooth muscle cells, whereas other areas developed multilayered densely populated smooth muscle cells. Computed planimetry was used to measure this bare surface area to quantitate the extent of hill and valley growth, which was compared between groups by analysis of variance. Smooth muscle cells cultured alone demonstrated prominent hill and valley formation with a bare surface area of 2.64 +/- 0.51 mm2. Smooth muscle cells exposed to transforming growth factor-beta 1 antibody had much less hill and valley formation (bare surface area 0.92 +/- 0.29, p < 0.01), whereas aprotinin virtually prevented hill and valley formation (bare surface area 0.0, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclosporin A enhances cytokine and phorbol ester-induced fibroblast collagenase expression

Cyclosporin A is successfully used in the treatment of scleroderma, a condition with excessive deposition of collagen in the dermis. Cultured human dermal fibroblasts were used as a model to study the effects of cyclosporin A on metalloproteinase expression and activity. Fibroblasts were treated with collagenase inducing agents, phorbol 12-myristate 13-acetate (PMA), cytokines interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), and the calcium ionophore A23187 in the presence of cyclosporin A under serum-free conditions, and alterations in metalloproteinase expression were studied by Northern hybridization and immunoblotting analyses, and assays for collagenolytic activity. Induction of collagenase expression by PMA and cytokines was enhanced severalfold by 1-10 microM cyclosporin A. Treatment of cells with cyclosporin A alone caused only a minor increase in collagenase mRNA levels. The secretion of immunoreactive collagenase protein and the level of p-aminophenylmercuric acetate activatable collagenase activity were increased by PMA and further enhanced by cyclosporin A. The expression of the other metalloproteinases stromelysin-1, 92-kD gelatinase, and 72-kD gelatinase or metalloproteinase inhibitor TIMP-1 were not affected by cyclosporin A. Time dependence analysis of the expression of the mRNAs for c-jun and junB indicated that the induction of these genes persisted significantly longer in cells treated with both PMA and cyclosporin A than in cells treated with PMA alone. Enhanced induction of collagenase mRNA may thus result from prolonged AP-1 activity. The results indicate that cyclosporin A potently enhances the expression of collagenase in dermal fibroblasts.

Regulation of plasminogen activation by interleukin-6 in human lung fibroblasts

We determined that exposure of cultured lung fibroblasts (HEL-299) to recombinant human interleukin-6 (0-400 ng/ml) resulted in a dose- and time-dependent increase in secreted and cell lysate PAI-1 and total tPA levels (maximal increase of 2.6-fold and 1.7-fold, respectively). Specificity of this response was indicated when increases in PAI-1 levels were inhibited by neutralizing polyclonal antibodies to IL-6, but not with non-specific antibodies. Inhibition of the response to IL-6 by cycloheximide and alpha-amanitin indicates that increases in PAI-1 are dependent on both protein and RNA synthesis. The addition of IL-6 to HEL-299 cells also stimulated a dose- and time-dependent increase in steady-state PAI-1 mRNA levels (3.8 to 15.1 pg/micrograms total RNA by 24 h). A rapid increase (5-6-fold) in PAI-1 mRNA levels was found between 3 and 12 h. Nuclear run-on assays using a maximum dose of IL-6 showed that IL-6 increases a 4-fold rate of transcription of the PAI-1 gene. We further showed that LPS induces a 70% increase in secreted IL-6 and a 50% increase in PAI-1 protein levels. Increasing doses of anti-IL-6 completely blocked the effect of LPS on PAI-1 while non-specific antibodies had no effect. These studies suggest an autocrine role for IL-6 in regulating localized proteolysis and modulating tissue remodeling during acute inflammatory conditions by fibroblasts.

Transforming growth factor-beta 1 stimulates macrophage urokinase expression and release of matrix-bound basic fibroblast growth factor

Macrophage expression of urokinase-type plasminogen activator (uPA) appears to play a role in their release of matrix-bound basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta). In experiments reported here, we have examined the potential regulatory effects of bFGF and TGF-beta 1 on macrophage uPA expression. TGF-beta 1 stimulated in a dose- and time-dependent manner the expression of secreted membrane and intracellular uPA activities by a macrophage cell line (RAW264.7). When examined at similar concentrations, bFGF had little effect, and interleukin-1 alpha, tumor necrosis factor-alpha, and monocyte colony stimulating factor had no effect on macrophage uPA expression. Exposure of macrophages to TGF-beta 1 led to a rapid and sustained increase in the steady-state levels of uPA mRNA that was independent of de novo protein synthesis and was completely inhibited by actinomycin D. However, the TGF-beta 1-induced increase in uPA mRNA was largely unaffected by subsequent incubation of cells with actinomycin D. The protein kinase C inhibitor H7 markedly reduced the ability of TGF-beta 1 to stimulate expression of uPA activity. Likewise, okadaic acid and microcystin, inhibitors of serine/threonine phosphatases, potentiated the ability of TGF-beta 1 to upregulate macrophage uPA expression. TGF-beta 1 primed cells converted nearly all added plasminogen to plasmin and expressed sixfold more membrane-bound plasmin than control cells. Preincubation of TGF-beta 1 with either serum or methylamine-modified alpha 2-macroglobulin did not affect its ability to induce macrophage uPA expression. When control and TGF-beta 1-primed macrophages were cultured on matrices containing bound 125I-bFGF, their release of 125I-bFGF was increased five and tenfold, respectively, in the presence of plasminogen. The ability of TGF-beta to induce macrophage uPA expression and the plasmin-dependent release of matrix-bound bFGF may provide an indirect mechanism by which TGF-beta stimulates angiogenesis.

TGF beta induction of extracellular matrix associated proteins in normal and transformed human mammary epithelial cells in culture is independent of growth effects

We have previously characterized a human mammary epithelial cell (HMEC) culture system for the effects of TGF beta 1 on cell growth. In the current report, the effects of TGF beta 1 on synthesis and secretion of proteins associated with the extracellular matrix and proteolysis were examined. In particular, we compared the TGF beta responses of normal finite lifespan HMEC, which are growth inhibited by TGF beta, to two immortally transformed cell lines derived from the normal HMEC. One of these lines maintains active growth in the presence of TGF beta and the other shows partial growth inhibition. In contrast to the differing effects of TGF beta on cell growth, we found that all these cell types showed strong induction of most of the mRNA and protein species examined, including fibronectin, collagen IV, laminin, type IV collagenase, urokinase type plasminogen activator (uPA), and plasminogen activator inhibitor 1 (PAI-1). The profile of TGF beta 1 binding proteins was the same in HMEC that were, and were not growth suppressed by TFG beta. Therefore, the effects of TGF beta on cell growth could be dissociated from its effects on specialized responses, indicating that within this one cell type there must be at least two independent pathways for TGF beta activity, one which leads to cessation of proliferation and one which induces a specific set of cellular responses. This cell system may be useful for examining the pathway of TGF beta induced growth inhibition using closely matched cells which vary in their growth-induced response but retain similar specialized responses to TGF beta.

Transforming growth factor beta as a neuronoglial signal during peripheral nervous system response to injury

In contrast to the central nervous system (CNS), the peripheral nervous system (PNS) displays an important regenerative ability which is dependent, at least in part, on Schwann cell properties. The mechanisms which stimulate Schwann cells to adapt their behavior after a lesion to generate adequate conditions for PNS regeneration remain unknown. In this work, we report that adult rat dorsal root ganglion (DRG) neurons are able, after a lesion performed in vivo or when they are dissociated and cultured in vitro, to synthesize transforming growth factor beta (TGF beta), a pleiotropic growth factor implicated in wound healing processes and in carcinogenesis. This TGF beta is tentatively identified as the beta-1 isoform. Adult rat DRG neurons release a biologically active form of TGF beta which is able to elicit multiple Schwann cell responses including a stimulation to proliferate. Moreover, purified TGF beta-1 produces a Schwann cell morphology alteration and decreases the secretion of tissue-type plasminogen activator (tPA) and enhances the secretion of plasminogen activator inhibitor (PAI) by Schwann cells. This generates conditions which are thought to favor a successful neuritic regrowth. Furthermore, purified TGF beta-1 stimulates type IV collagen mRNA expression in Schwann cells. This subtype of collagen is associated with the process of myelinization. Finally, TGF beta-1 decreases nerve growth factor (NGF) mRNA expression by Schwann cells, an effect which could participate in the maintenance of a distoproximal NGF gradient during nerve regeneration. We propose that neuronal TGF beta plays an essential role as a neuronoglial signal that modulates the response of Schwann cells to injury and participates in the successful regeneration processes observed in the PNS.

The effect of transforming growth factor beta on the plasminogen activator activity of normal human osteoblast-like cells and a human osteosarcoma cell line MG-63

Transforming growth beta (TGF-beta) has been proposed to have a role in bone remodeling by affecting the differentiation and activity of osteoblasts and osteoclasts and by inhibiting the production of proteinases, such as plasminogen activators (PAs). Studies on PAs have largely been based on data from nonhuman and fetal cell lines, however. The purpose of this study was to investigate the effect of TGF-beta on the PA activity of normal human osteoblast-like cells and to compare this with its action on the human osteosarcoma cell line MG-63. The action of interleukin-1 beta (IL-1 beta) was also assessed because it has been shown to increase PA activity in other connective tissue cell types. Normal osteoblast-like cells had low to undetectable basal urokinase (uPA) and tissue plasminogen activator (tPA) activity, which was significantly stimulated by TGF-beta 1. This action was shown to be dependent on transcription and new protein synthesis. TGF-beta 2 had a similar action. IL-1 beta did not stimulate PA activity. In contrast, the MG-63 cell line had high basal tPA and uPA activities. TGF-beta 1 decreased basal PA activity, the effect being most marked for uPA activity. IL-1 beta stimulated uPA and tPA activity. TGF-beta 1 inhibited IL-1 beta-stimulated uPA activity, but the effect on tPA was more variable. This study has shown that TGF-beta has opposite effects on the PA activity of the two osteoblast-like cell types studied. Care must therefore be used before extrapolating data from one cell type to another.(ABSTRACT TRUNCATED AT 250 WORDS)

Pericellular substrates of human mast cell tryptase: 72,000 dalton gelatinase and fibronectin

Migrating cells degrade pericellular matrices and basement membranes. For these purposes cells produce a number of proteolytic enzymes. Mast cells produce two major proteinases, chymase and tryptase, whose physiological functions are poorly known. In the present study we have analyzed the ability of purified human mast cell tryptase to digest pericellular matrices of human fibroblasts. Isolated matrices of human fibroblasts and fibroblast conditioned medium were treated with tryptase, and alterations in the radiolabeled polypeptides were observed in autoradiograms of sodium dodecyl sulphate polyacrylamide gels. It was found that an M(r) 72,000 protein was digested to an M(r) 62,000 form by human mast cell tryptase while the plasminogen activator inhibitor, PAI-1, was not affected. Cleavage of the M(r) 72,000 protein could be partially inhibited by known inhibitors of tryptase but not by aprotinin, soybean trypsin inhibitor, or EDTA. Fibroblastic cells secreted the M(r) 72,000 protein into their medium and it bound to gelatin as shown by analysis of the medium by affinity chromatography over gelatin-Sepharose. The soluble form of the M(r) 72,000 protein was also susceptible to cleavage by tryptase. Analysis using gelatin containing polyacrylamide gels showed that both the intact M(r) 72,000 and the M(r) 62,000 degraded form of the protein possess gelatinolytic activity after activation by sodium dodecyl sulphate. Immunoblotting analysis of the matrices revealed the cleavage of an immunoreactive protein of M(r) 72,000 indicating that the protein is related to type IV collagenase. Further analysis of the pericellular matrices indicated that the protease sensitive extracellular matrix protein fibronectin was removed from the matrix by tryptase in a dose-dependent manner. Fibronectin was also susceptible to proteolytic degradation by tryptase. The data suggest a role for mast cell tryptase in the degradation of pericellular matrices.

Transforming growth factor-beta 1 is a heparin-binding protein: identification of putative heparin-binding regions and isolation of heparins with varying affinity for TGF-beta 1

Previous studies indicated that a major factor in heparin's ability to suppress the proliferation of vascular smooth muscle cells is an interaction with transforming growth factor-beta 1 (TGF-beta 1). Heparin appeared to bind directly to TGF-beta 1 and to prevent the association of TGF-beta 1 with alpha 2-macroglobulin (alpha 2-M). The present studies indicate that 20-70% of iodinated TGF-beta 1 binds to heparin-Sepharose and the retained fraction is eluted with approximately 0.37 M NaCl. Native, unlabelled platelet TGF-beta 1, however, is completely retained by heparin-Sepharose and eluted with 0.9-1.2 M NaCl. Using synthetic peptides, the regions of TGF-beta 1 that might be involved in the binding of heparin and other polyanions were examined. Sequence analysis of TGF-beta 1 indicated three regions with a high concentration of basic residues. Two of these regions had the basic residues arranged in a pattern homologous to reported consensus heparin-binding regions of other proteins. The third constituted a structurally novel pattern of basic residues. Synthetic peptides homologous to these three regions, but not to other regions of TGF-beta 1, were found to bind to heparin-Sepharose and were eluted with 0.15 M-0.30 M NaCl. Only two of these regions were capable of blocking the binding of heparin to 125I-TGF-beta. Immobilization of these peptides, followed by affinity purification of heparin, indicated that one peptide was capable of isolating subspecies of heparin with high and low affinity for authentic TGF-beta 1. The ability of TGF-beta 1 to bind to heparin or related proteoglycans under physiological conditions may be useful in understanding the biology of this pluripotent growth and metabolic signal. Conversely, a subspecies of heparin molecules with high affinity for TGF-beta 1 may be a factor in some of the diverse biological actions of heparin.

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.

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.

Regulation of tumor-host interactions in breast cancer

Breast cancer has a striking dependence upon steroid and other endocrine hormones in its onset, regulation, and malignant progression to its most deadly forms. The epithelium of the normal mammary gland is also regulated by the ovarian endocrine steroids estrogen and progesterone, by other endocrine hormones, and by poorly defined influences of the stromal cells and basement membrane. The onset and development of cancer appears to involve tumor misinterpretation of and/or desensitization to host regulatory signals, and finally to releasing its own hormonal signal to reorganize the host for its own benefit. Current studies are beginning to examine mediators of tumor-host interaction and their regulation by steroid hormones. Important tumor-host interactions under investigation include desmoplasia, angiogenesis, metastases and immunosuppression.

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

Transforming growth factor-beta is a pluripotent regulator of cell growth and differentiation. The growth factor is expressed as a latent complex that must be converted to an active form before interacting with its ubiquitous high affinity receptors. This conversion involves the release of the mature growth factor through disruption of the non-covalent interactions with its pro-peptide or latency associated peptide. The mechanisms for this release in vivo have not been fully characterized but appear to be cell specific and might involve processes such as acidification or proteolysis. Although several factors including transcriptional regulation, receptor modulation and scavenging of the active growth factor have been implicated, the critical step controlling the biological effects of transforming growth factor-beta may be the activation of the latent molecule.

Endothelial cell regulation by transforming growth factor-beta

Pronounced changes including growth inhibition, increased matrix deposition and suppression of cell-associated proteolytic activity, take place in endothelial cells (EC) upon the application of TGF-beta. Interrelationships between these effects have shed some light on the mechanism of action of TGF-beta and on its role in regulating EC function vis-a-vis angiogenesis. For instance, preliminary evidence has indicated that increased levels of certain matrix components may be partly responsible for the antiproliferative action of TGF-beta. In addition, TGF-beta and bFGF have opposing effects on cellular proteolytic balance which may contribute to the antagonistic effect that TGF-beta has on bFGF-induced EC growth and possibly to the anti-angiogenic effect exerted by TGF-beta under certain circumstances. Of particular interest in this regard is the fact that physical contact between EC and vascular mural cells in EC:mural cell cocultures has been found to generate active TGF-beta, thus further implicating TGF-beta in the maintenance of the quiescent, differentiated aggregation of EC as found in vascular structures in vivo. While more information is needed to define what, if any role TGF-beta plays in endothelial differentiation, it is to be noted that many of the cellular and biochemical processes affected by TGF-beta are linked to differentiation. It is therefore possible that the growth inhibition of EC by TGF-beta primes them for differentiation and/or is critical for the maintenance of a differentiated state.

Transforming growth factor beta inhibits plasminogen activator (PA) activity and stimulates production of urokinase-type PA, PA inhibitor-1 mRNA, and protein in rat osteoblast-like cells

Transforming growth factor beta (TGF beta) treatment of rat osteoblast-rich calvarial cells or of the clonal osteogenic sarcoma cells, UMR 106-01, resulted in dose-dependent inhibition of plasminogen activator (PA) activity, and increased production of 3.2 kb mRNA and protein for PA inhibitor -1 (PAI-1). Although tissue-type PA (tPA) protein was not measured, TGF beta did not influence production of mRNA for tPA. Production of 2.3 kb mRNA for urokinase-type PA (uPA) was also increased by TGF beta in a dose-dependent manner. The effects of TGF beta on synthesis of mRNA for PAI-1 and uPA were maintained when protein synthesis was inhibited, and were abolished by inhibition of RNA synthesis. Although uPA had not been detected previously as a product of rat osteoblasts, treatment of lysates of osteoblast-like cells with plasmin yielded a band of PA activity on reverse fibrin autography, corresponding to a low Mr form of uPA. Untreated conditioned media from normal osteoblasts or UMR 106-01 cells contained no significant TGF beta activity, but activity could be detected in acidified medium. Treatment of conditioned media with plasmin resulted in activation of approximately 50% of the TGF beta detectable in acidified media. The results identify several effects of TGF beta on the PA-PA inhibitor system in osteoblasts. Net regulation of tPA activity through the stimulatory actions of several calciotropic hormones and the promotion of PAI-1 formation by TGF beta could determine the amount of osteoblast-derived TGF beta activated locally in bone. Stimulation of osteoblast production of mRNA for uPA could reflect effects on the synthesis of sc-uPA, a precursor for the active form of the enzyme.

Transforming growth factor beta stimulates urokinase-type plasminogen activator and DNA synthesis, but not prostaglandin E2 production, in human synovial fibroblasts

Transforming growth factor beta (TGF-beta) is usually associated with matrix formation and tissue repair; in contrast, cellular expression of the serine proteinase, urokinase-type plasminogen activator (u-PA) is often correlated with tissue remodeling, as well as with cell migration and transformation. We report here that purified recombinant human TGF-beta (greater than or equal to 300 pg/ml) can stimulate rapidly (within 2 h) the u-PA activity of nonrheumatoid synovial fibroblast-like cells. As for interleukin 1 (IL-1), u-PA mRNA levels are raised in response to TGF-beta, but unlike IL-1, no increase in prostaglandin E2 levels occurs. In contrast to a number of other examples in the literature, in which these two cytokines have opposing actions, TGF-beta can potentiate the action of optimal concentrations of IL-1 in enhancing u-PA expression. These effects of TGF-beta are similar to those of all-trans-retinoic acid. In addition, synovial fibroblast DNA synthesis was stimulated by TGF-beta. Because TGF-beta has been detected in the synovia of patients with rheumatoid arthritis and has been shown to reduce the collagenase levels and proliferation of synovial fibroblast-like cells, it has been proposed by others to be involved beneficially in the reparative processes occurring in arthritic lesions. However, on the basis of our findings, we propose alternative functions for this cytokine--namely, roles in the destructive events as well as in the synovial hyperplasia observed in rheumatoid joints.

Regulation of the expression of a secreted acidic protein rich in cysteine (SPARC) in human fibroblasts by transforming growth factor beta. Comparison of transcriptional and post-transcriptional control with fibronectin and type I collagen

Transforming growth factor beta (TGF-beta) and secreted protein acidic rich cysteine (SPARC) have been associated with the rapid remodeling of connective tissues that occurs in wound healing and developmental processes. To study the temporal and mechanistic aspects of TGF-beta-regulated extracellular-protein gene expression in human fibroblasts, confluent cells were pulse labeled for 30 min with [35S]methionine at various times following the single addition of 1.0 ng/ml TGF-beta. After a 4-h chase period, specific radiolabeled media proteins were isolated by either immunoprecipitation or affinity chromatography and quantitated. Stimulation of SPARC synthesis was first apparent 5 h after addition of TGF-beta, reached a maximum (3.5-fold increase) at 24 h and persisted for at least 96 h. A similar temporal response to TGF-beta was observed for the extracellular matrix proteins collagen and fibronectin. In contrast, TGF-beta induced a strong (greater than sixfold increase at 9 h after addition of TGF-beta), but transient stimulation of the synthesis of endothelial-type plasminogen activator inhibitor. Northern blot analysis showed that SPARC mRNA levels were increased by TGF-beta in parallel with increase in SPARC synthesis; a maximum 3.9-fold increase in SPARC mRNA being reached at 24 h. Similarly, the levels of both collagen and fibronectin mRNA were increased by TGF-beta treatment. In each case the stimulation of mRNA was blocked by the presence of the translation inhibitor, cycloheximide. Stability of SPARC mRNA (half-life of approximately 50 h) was not significantly altered by TGF-beta. In contrast, the stability of collagen and fibronectin mRNA were both increased in the presence of TGF-beta; the increased stability being pronounced in less dense cells. In addition to effects on stability, transcription of the collagen and fibronectin genes was increased 7 h after TGF-beta addition, but returned to control levels by 24 h. However, transcription of the SPARC gene was unaffected by TGF-beta at both time points and, together with the stability data, indicates that TGF-beta regulates SPARC expression via a nuclear post-transcriptional mechanism. Differential regulation of gene expression by TGF-beta in a precise temporal pattern via transcriptional and post-transcriptional pathways may be an important aspect of the response of fibroblast cells in a wound environment.

Reaction of alpha 2-macroglobulin with plasmin increases binding of transforming growth factors-beta 1 and beta 2

The binding of 125I-transforming growth factors-beta 1 and beta 2 (TGF-beta 1 and TGF-beta 2) to alpha 2-macroglobulin (alpha 2M) was studied before and after reaction with plasmin, thrombin, trypsin, or methylamine. Complex formation between TGF-beta and native or reacted forms of alpha 2M was demonstrated by non-denaturing polyacrylamide gel electrophoresis and autoradiography. Reaction of native alpha 2M with plasmin or methylamine markedly increased the binding of 125I-TGF-beta 1 and 125I-TGF-beta 2 to alpha 2M. The alpha 2M-plasmin/TGF-beta complexes were minimally dissociated by heparin. Reaction of alpha 2M with thrombin or trypsin reduced the binding of 125I-TGF-beta 1 and 125I-TGF-beta 2; the resulting complexes were readily dissociated by heparin. Complexes between TGF-beta 2 and native or reacted forms of alpha 2M were less dissociable by heparin than the equivalent complexes with TGF-beta 1. These studies demonstrate that the TGF-beta-binding activity of alpha 2M is significantly affected by plasmin, thrombin, trypsin and methylamine. Observations that alpha 2M-plasmin preferentially binds TGFs-beta suggest a mechanism by which alpha 2M may regulate availability of TGFs-beta to target cells in vivo.