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

Cellular distribution of transforming growth factor-beta 1 and procollagen types I, III, and IV transcripts in carbon tetrachloride-induced rat liver fibrosis

The cellular distribution and temporal expression of transcripts from transforming growth factor-beta 1 (TGF-beta 1) and procollagen alpha 1(I), alpha 1(III), and alpha 1(IV) genes were studied in carbon tetrachloride (CCl4)-induced rat liver fibrosis by using in situ hybridization technique. During the fibrotic process, TGF-beta 1 and procollagen genes were similarly and predominantly expressed in Desmin-positive perisinusoidal cells (e.g., fat-storing cells and myofibroblasts) and fibroblasts and their expression continued to be higher than those observed in control rats. These transcripts were also observed in inflammatory cells mainly granulocytes and macrophage-like cells at the early stages of liver fibrosis. The production of extracellular matrix along small blood vessels and fibrous septa coincided with the expression of these genes. Expression of TGF-beta 1 and procollagen genes were not detected in hepatocytes throughout the experiment. No significant differences in cellular distribution or time course of gene expression among procollagen alpha 1(I), alpha 1(III), and alpha 1(IV) were observed. Desmin-positive perisinusoidal cells and fibroblasts appeared to play the principal role in synthesis of collagens in CCl4-induced hepatic fibrosis. The simultaneous expression of TGF-beta 1 and procollagen genes in mesenchymal cells, including Desmin-positive perisinusoidal cells, during hepatic fibrosis suggests the possibility that TGF-beta 1 may have an important role in the production of fibrosis.

Cellular mechanisms of TGF-beta action

Transforming growth factor beta (TGF-beta), initially identified in platelet extracts by virtue of its ability to confer anchorage-independent growth and a neoplastic phenotype on mesenchymal cells, has subsequently been identified as a potent inhibitor of proliferation in most cells of epithelial origin. Our laboratory has investigated the role of specific second messengers in mediating the transcriptional responses of fibroblasts following addition of TGF-beta 1. Our studies indicate that TGF-beta 1, alone and in conjunction with epidermal growth factor (EGF), is capable of stimulating increases in both phosphoinositide metabolism and calcium influx, leading to significant increases in intracellular levels of Ca++ and inositol trisphosphate (IP3). Our data indicated that Ca++ influx and inositol phosphate release are coupled in Rat-1 cells, and suggested that influx of Ca++ from the extracellular medium is required for the change in IP3 accumulation observed in response to both EGF and TGF-beta 1. Using nuclear run-on analysis of the transcription of rat transin, a secreted metalloproteinase homologous to human stromelysin, we have also demonstrated a significant inhibition of transin transcription within 10 min of TGF-beta 1 treatment. The ability of TGF-beta 1 to inhibit transin gene transcription was not related to the TGF-beta 1-induced influx of Ca++ or to an increase in intracellular inositol phosphates, since inhibiting production of these second messengers failed to inhibit repression of the transin gene.

Immunohistochemical evidence of a role for transforming growth factor beta in the pathogenesis of nodular sclerosing Hodgkin's disease

Transforming growth factor beta (TFG-beta) is a multifunctional growth factor that promotes the growth of fibroblasts, collagen synthesis and angiogenesis, and stimulates monocyte migration and activation, but suppresses the growth and differentiation of immune lymphocytes and killer cells. Previously we demonstrated biologic activity for TGF-beta in supernatants of fresh Hodgkin's disease (HD) cell cultures and the cell line L428 derived from nodular sclerosing HD. This study was undertaken to find evidence of TGF-beta activity directly in tissues affected by HD. Formalin-fixed tissue from 14 patients with HD, including 8 nodular sclerosis, 4 mixed cellularity, 1 lymphocyte predominance, and 1 lymphocyte depletion type were studied by immunoperoxidase technique with antibody CC (1-30) raised against a synthetic polypeptide with the same N-terminal amino acid sequence as TGF-beta 1. Transforming growth factor beta activity was demonstrated in six cases of nodular sclerosis but not in other histologic types of HD. Staining for TGF-beta was found in the cytoplasm of Reed-Sternberg (RS) cells in one case and on the surface of RS cells and their lacunar variants in five cases. Transforming growth factor beta activity associated with the extracellular matrix was localized mainly around blood vessels, zones of necrosis, at the margins of bands of collagen sclerosis, and in areas containing syncytia of RS cells. In two cases TGF-beta was associated with collections of epithelioid histiocytes or granulomas. Small lymphocytes, granulocytes, and germinal center cells were unreactive. These results suggest that TGF-beta is a growth factor of biologic importance in HD and may be responsible for many of the histologic features, such as nodular sclerosis and granulomas, that may have prognostic significance.

Transforming growth factor-beta and the initiation of chondrogenesis and osteogenesis in the rat femur

We have investigated the ability of exogenous transforming growth factor-beta (TGF-beta) to induce osteogenesis and chondrogenesis, critical events in both bone formation and fracture healing. Daily injections of TGF-beta 1 or 2 into the subperiosteal region of newborn rat femurs resulted in localized intramembranous bone formation and chondrogenesis. After cessation of the injections, endochondral ossification occurred, resulting in replacement of cartilage with bone. Gene expression of type II collagen and immunolocalization of types I and II collagen were detected within the TGF-beta-induced cartilage and bone. Moreover, injection of TGF-beta 2 stimulated synthesis of TGF-beta 1 in chondrocytes and osteoblasts within the newly induced bone and cartilage, suggesting positive autoregulation of TGF-beta. TGF-beta 2 was more active in vivo than TGF-beta 1, stimulating formation of a mass that was on the average 375% larger at a comparable dose (p less than 0.001). With either TGF-beta isoform, the dose of the growth factor determined which type of tissue formed, so that the ratio of cartilage formation to intramembranous bone formation decreased as the dose was lowered. For TGF-beta 1, reducing the daily dose from 200 to 20 ng decreased the cartilage/intramembranous bone formation ratio from 3.57 to zero (p less than 0.001). With TGF-beta 2, the same dose change decreased the ratio from 3.71 to 0.28 (p less than 0.001). These data demonstrate that mesenchymal precursor cells in the periosteum are stimulated by TGF-beta to proliferate and differentiate, as occurs in embryologic bone formation and early fracture healing.

Bartonella bacilliformis stimulates endothelial cells in vitro and is angiogenic in vivo

Bartonellosis, a biphasic disease caused by motile intracellular bacteria, produces in its tissue phase a characteristic dermal eruption (Verruga peruana) resulting from a pronounced endothelial cell proliferation. Bacteria are found in the interstitium and within the cytoplasm of endothelial cells (Rocha-Lima inclusion). The aim of this study was to determine if Bartonella bacilliformis produce a substance(s) that might be responsible for the vascular proliferation seen in the Verruga. This was assessed in an in vitro system using human endothelial cells and measuring proliferation as well as production of tissue type plasminogen activator after exposure to the endothelial cultures to B. bacilliformis extracts. Our results indicate that B. bacilliformis possess an activity that stimulates endothelial cell proliferation up to three times that of control. The factor(s) is specific for endothelial cells, heat sensitive, larger than 12 to 14 kd, not enhanced by heparin, has no affinity for heparin, and is precipitated by 45% ammonium sulfate. In addition, the B. bacilliformis extracts stimulate production of t-PA antigen in a concentration-dependent fashion. This activity is also heat sensitive and not lost after dialysis (12 to 14 kd). B. bacilliformis extracts, however, do not increase the production of plasminogen activator inhibitor. It was also determined that B. bacilliformis extracts stimulate the formation of new blood vessels in an in vivo model for angiogenesis. These results describe a bacterial factor(s) that stimulates two important steps in the development of new blood vessels in vitro, as well as the formation of new blood vessels in vivo. Determining the mechanism of action, combined with a complete characterization of this factor(s), may help in understanding the pathogenesis not only of the Verruga and angiogenesis in general but also the recently described Cat-Scratch-associated epithelioid hemangiomas in patients with AIDS and Kaposi sarcoma.

The effect of platelet releasate on wound healing in animal models

The alpha granules of platelets contain growth factors that are important in wound healing. We found that a major effect of thrombin-induced human platelet releasates in animal models of wound healing is to enhance the development of granulation tissue and new connective tissue matrix. These studies provide further evidence that platelet-derived protein factors may be useful in treating full-thickness dermal wounds by increasing the rate of granulation tissue formation.

Histamine as a growth factor and chemoattractant for human carcinoma and melanoma cells: action through Ca2(+)-mobilizing H1 receptors

Histamine receptors are present on the surface of various normal and tumor-derived cell types, where their biological function is incompletely understood. Here we report that histamine not only stimulates cell proliferation under serum-free conditions, but also is chemotactic for human carcinoma (Hela and A431) and melanoma (A875) cells expressing H1 type receptors. Histamine was found to be a potent activator of phospholipase C, leading to polyphosphoinositide hydrolysis and subsequent intracellular Ca2+ mobilization. In addition, histamine also causes the protein kinase C-mediated activation of Na+/H+ exchange, as evidenced by an amiloride-sensitive rise in cytoplasmic pH. All histamine-induced responses, including chemotaxis and DNA synthesis, are completely inhibited by the H1 receptor antagonist pyrilamine, but not by cimetidine, an inhibitor of histamine H2 type receptors. Our results suggest that histamine may have a previously unrecognized role in the migration and proliferation of cells expressing H1 receptors.

Exogenous transforming growth factor-beta 2 enhances connective tissue formation and wound strength in guinea pig dermal wounds healing by secondary intent

The presence of transforming growth factor-beta (TGF-beta) at the site of acute injury, its ability to attract inflammatory and connective tissue cells, and its stimulatory effect on the deposition of connective tissue matrix combine to suggest that it may play a key role in the response to injury. The effect of exogenous TGF-beta form 2 on dermal wounds healing by secondary intent was investigated using a sponge composed of collagen and heparin as a delivery vehicle. Longitudinal lenticular-shaped wounds on the dorsum of adult guinea pigs were treated at the time of wounding with delivery vehicle containing 0.5, 1, or 5 micrograms of purified, bovine bone-derived TGF-beta 2, and were compared with wounds that received vehicle only or were untreated. At days 8 and 14 the amount of connective tissue in the wounds and the extent of epithelialization were determined by histomorphometric methods, and wound breaking strength was determined. At day 8, but not at day 14, wounds treated with 1 or 5 micrograms of TGF-beta 2 contained a significantly higher proportion of connective tissue than did wounds treated with vehicle only, and they also exhibited higher wound strength. No effect on wound size or re-epithelialization was detected. The observations provide evidence that a single treatment with exogenous TGF-beta 2 delivered in collagen/heparin sponge vehicle can accelerate repair in guinea pig dermal wounds allowed to heal by secondary intent.

Evaluation of transforming growth factor beta and type I procollagen gene expression in fibrotic skin diseases by in situ hybridization

Full thickness biopsies of affected skin and fascia from one patient with diffuse fasciitis and eosinophilia (DF), two patients with generalized morphea (GM), and five patients with progressive systemic sclerosis (PSS) of recent onset were examined for the expression of transforming growth factor beta 1 (TGF beta 1) and type I procollagen genes by in situ hybridization with human sequence-specific cDNA. An increased number of fibroblasts showing clearly detectable expression of pro alpha 1(I)collagen gene was found in all fibrotic lesions when compared with unaffected skin from the patient with DF and skin from two normal individuals examined in parallel. Expression of the TGF beta 1 gene was noted in a fibroblast subpopulation of the affected tissues from the patients with DF and GM. In contrast, the TGF beta 1 gene was not expressed at a detectable level in affected skin from the five patients with PSS. The results suggest that TGF beta 1 may play a role in the development of skin fibrosis in cases of DF and GM. However, from these studies, we cannot implicate TGF beta 1 in the pathogenesis of skin fibrosis in PSS.

Atherogenesis during low level hypercholesterolemia in the nonhuman primate. I. Fatty streak formation

Although a large body of data is available concerning atherogenesis in animals maintained at high levels of hypercholesterolemia, little data are available for animals maintained at lower levels of hypercholesterolemia for longer periods of time, closer to those observed in humans. The chronologic sequence of cellular events and interactions that occur during the formation of the lesions of atherosclerosis was investigated during relatively low level hypercholesterolemia (200 to 400 mg/dl) in a series of nonhuman primates (Macaca nemestrina). The arterial tree of each animal was examined by light microscopy and scanning and transmission electron microscopy. Immunohistochemical staining with monoclonal antibodies specific for smooth muscle cells, monocyte-macrophages, and T-lymphocytes was performed to analyze the cellular composition of the lesions. After 6 months of low level hypercholesterolemia, the surface of the aorta contained large numbers of adherent leukocytes, many of which were in the process of entering the artery. This resulted in irregularly shaped nodular elevations, or fatty streaks, preferentially located at branch sites and bifurcations. The fatty streaks consisted of intimal accumulations of numerous lipid-laden macrophages together with relatively small numbers of T-lymphocytes. With lesion progression, the thickness of the fatty streaks increased, and their surfaces became irregular and frequently showed disruptions of covering endothelial cells resulting in exposure of subendothelial macrophages. Platelet microthrombi were observed over some of the exposed macrophages at some branches or bifurcations in every animal studied. These observations made during the early phases of atherosclerosis lesion formation are virtually identical to those described in our previous reports in high level hypercholesterolemic nonhuman primates (600 to 1000 mg/dl) with the exception that the changes occurred more slowly in the lower levels of hypercholesterolemia.

Connective tissue biology and hepatic fibrosis: report of a conference

The past 15 years have seen major advances in the characterization of extracellular matrix proteins and structure of matrix. As a by-product of this work, investigators now have an array of molecular and immunological reagents for monitoring matrix metabolism. Progress in the isolation and culture of individual cell types from liver has made possible direct measurement of matrix protein production and also has opened the way to studies of matrix degradation. The expanding knowledge of soluble mediators of inflammation is being applied to the regulation of matrix protein synthesis and degradation. Finally, experimental models of fibrosis in vivo are available for defining the complexity of matrix metabolism in the intact tissue and for validating the findings from cell culture and in vitro systems.

Transforming growth factors and the regulation of cell proliferation

The number of different growth regulatory molecules which have been isolated and characterized is continuing to increase. As more information is obtained, it has become apparent that the cooperative actions of many factors with distinct activities is necessary for appropriate proliferative responses. An interplay of both growth stimulatory and growth inhibitory factors is essential for normal growth. Of crucial importance, therefore, is the appropriate regulation of growth factors. Unregulated expression, synthesis, posttranslational processing or activation of either positive or negative growth signals may contribute to neoplastic transformation (Fig. 3). Altered responses to normally positive or negative signals by transformed cells have been demonstrated by several investigators [64, 79, 84]. While altered growth factor responses in transformed cells are well documented, the mechanisms responsible for the loss of growth control are poorly understood and are likely to be both complex and numerous. Continued efforts to dissect and comprehend fully growth factor action on normal cells will be necessary before an understanding of neoplastic transformation can be achieved.

Effects of transforming growth factor-beta on long-term human cord blood monocyte cultures

Transforming growth factor-beta (TGF-beta) modulates growth and differentiation in many cell types and is abundant in bone matrix. We recently showed that human cord blood monocytes cultured in the presence of 1,25(OH)2D3 acquire some features of osteoclast precursors. Since TGF-beta has been shown to influence bone resorption in organ culture, we have studied the effect of TGF-beta (1-1,000 pg/ml) on cord blood monocyte cultures. These cells were cultured on plastic substrate during 3 weeks in the presence of 20% horse serum and 10(-9) M 1,25(OH)2D3. TGF-beta, from a concentration of 10 pg/ml in the culture medium, decreased in a dose dependent manner the formation of multinucleated cells. At a concentration of TGF-beta of 1 ng/ml, the multinucleated cells were reduced to 2.1% +/- 0.3%, compared to 19.3% +/- 1.5% in control cultures. TGF-beta inhibited in a dose-dependent manner the proliferation of cord blood monocytes as assessed by 3H-thymidine incorporation at 7 and 14 days of culture. The fusion index was also decreased by 3 weeks of treatment with TGF-beta. Indomethacin did not reverse the inhibitory effects of TGF-beta. The expression of the osteoclastic phenotype was assessed using two different antibodies: 23C6, a monoclonal antibody directed against the vitronectin receptor, which is highly expressed by osteoclasts but not by adult monocytes, and an antibody to HLA-DR, which is not present on osteoclast. TGF-beta decreased the expression of HLA-DR and increased in a dose-dependent manner the proportion of 23C6-labeled cells; these results suggest that TGF-beta could modulate a differentiation effect to the osteoclastic phenotype. However, when cord blood monocytes were cultured on devitalized rat calvariae prelabeled with 45Ca, TGF-beta did not induce any 45Ca release from bone cultured with monocytes, suggesting that full osteoclastic differentiation was not achieved. These results emphasize the complex role of TGF-beta in the local regulation of bone cell differentiation and in bone remodeling.

Complex regulation of transforming growth factor beta 1, beta 2, and beta 3 mRNA expression in mouse fibroblasts and keratinocytes by transforming growth factors beta 1 and beta 2

Regulation of transforming growth factor beta 1 (TGF beta 1), TGF beta 2, and TGF beta 3 mRNAs in murine fibroblasts and keratinocytes by TGF beta 1 and TGF beta 2 was studied. In quiescent AKR-2B fibroblasts, in which TGF beta induces delayed stimulation of DNA synthesis, TGF beta 1 autoregulation of TGF beta 1 expression was observed as early as 1 h, with maximal induction (25-fold) after 6 to 12 h. Increased expression of TGF beta 1 mRNA was accompanied by increased TGF beta protein production into conditioned medium of AKR-2B cells. Neither TGF beta 2 nor TGF beta 3 mRNA, however, was significantly induced, but both were apparently down regulated at later times by TGF beta 1. Protein synthesis was not required for autoinduction of TGF beta 1 mRNA in AKR-2B cells. Nuclear run-on analyses and dactinomycin experiments indicated that autoregulation of TGF beta 1 expression is complex, involving both increased transcription and message stabilization. In contrast to TGF beta 1, TGF beta 2 treatment of quiescent AKR-2B cells increased expression of TGF beta 1, TGF beta 2, and TGF beta 3 mRNAs, but with different kinetics. Autoinduction of TGF beta 2 mRNA occurred rapidly with maximal induction at 1 to 3 h, enhanced TGF beta 3 mRNA levels were observed after 3 h, and increased expression of TGF beta 1 occurred later, with maximal mRNA levels obtained after 12 to 24 h. Nuclear run-on analyses indicated that TGF beta 2 regulation of TGF beta 2 and TGF beta 3 mRNA levels is transcriptional, while TGF beta 2 induction of TGF beta 1 expression most likely involves both transcriptional and posttranscriptional controls. In BALB/MK mouse keratinocytes, minimal autoinduction of TGF beta 1 occurred at only the 12- and 24-h time points and protein synthesis was required for this autoinduction. The results of this study provide an example in which TGF beta 1 and TGF beta 2 elicit different responses and demonstrate that expression of TGF beta 1, and TGF beta 3 are regulated differently. The physiological relevance of TGF beta 1 autoinduction in the context of wound healing is discussed.

Recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) enhances healing and strength of granulation skin wounds

A new animal model to study secondary intention wound healing and the effects of topically applied rhTGF-beta 1 was developed. A time course study was performed of full thickness 6 mm punch wounds placed on the backs of anesthetized pigs and treated once with either 3% methylcellulose or rhTGF-beta 1 in 3% methylcellulose or left untreated. Wounds receiving rhTGF-beta 1 had enhanced tensile strength at days 4 and 7 compared to controls. Studies of the response on days 4 and 7 to graded doses of rhTGF-beta 1 showed that a dose of 250 or 2500 ng rhTGF-beta 1 gave a similar enhanced wound strength, while 25 ng rhTGF-beta 1 had no effect. Blood flow to treated granulating wounds as measured by 141Ce microspheres indicate an increase in flow in wounds treated with 250, 500 or 2500 ng rhTGF-beta 1 compared to controls. These results indicate a possible use for rhTGF-beta 1 in enhancing wound healing clinically.

Accelerated healing of ulcer wounds in the rabbit ear by recombinant human transforming growth factor-beta 1

A dermal ulcer wound-healing model was established in rabbit ear to examine the effects of recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) in wound healing. Histomorphometric examination of the wounds indicate a biphasic healing response 7 days after a single application of rhTGF-beta 1 at the time of wounding. Statistically significant healing occurred at 5-100 ng but not at higher doses of 500 or 1000 ng rhTGF-beta 1/wound. Enhanced collagen synthesis as determined by [3H]proline incorporation occurred at 15 and 25 ng and was significantly depressed at 500 ng rhTGF-beta 1/wound. Multiple doses of 100 ng rhTGF-beta 1 applied to the wound at the time of wounding and for 3 days after wounding provided results comparable to the single application of growth factor. Delaying treatment 24 hr after wounding did not enhance wound healing compared with vehicle. Our findings suggest that rhTGF-beta 1 can be a valuable growth factor to improve the healing of ulcer wounds.

Rapid onset synovial inflammation and hyperplasia induced by transforming growth factor beta

After intraarticular injection of TGF-beta 1 or TGF-beta 2, marked swelling and erythema of the injected joints were apparent within 12-24 h. On a scale of 0 to 4, by day 3, the TGF-beta-treated joints had articular indices (AI) of 3.6 +/- 0.5 to 4.0 +/- 0.0 compared with no response for the vehicle-injected contralateral joints. Histopathologic evaluation revealed a predominantly mononuclear phagocyte infiltrate with some neutrophils and T lymphocytes, consistent with active inflammation. The monocytic pattern of leukocyte infiltration at 2-3 d was comparable to that seen in animals with antigen-induced arthritis after 2-3 wk. Extensive synovial fibroblast hyperplasia became apparent within 48 h, likely as a result of TGF-beta induction of growth factor synthesis by the accumulating monocytes. TGF-beta 2, a homologue of TGF-beta 1, was found to induce a similar level of synovitis and synovial hyperplasia consistent with its parallel monocyte and fibroblast chemotactic properties and ability to induce transcription and translation of monocyte/macrophage-derived growth factors. These data suggest that TGF-beta, released by platelets and activated inflammatory cells, may play a direct role in leukocyte recruitment and activation in arthritic and other chronic inflammatory lesions.

Mesoderm induction in Xenopus laevis distinguishes between the various TGF-beta isoforms

Induction of mesoderm in ectodermal explants of Xenopus laevis blastula embryos had previously been shown to respond selectively to TGF-beta 2, with TGF-beta s 1 and 5 having no activity in this assay. As TGF-beta s 1, 2, and 3 are frequently coexpressed in tissues, we wished to examine the activity of TGF-beta 3 relative to that of TGF-beta s 1 and 2 in this assay as well as in other in vitro assays. We report here that when the activity of recombinant TGF-beta 3 is normalized to that of TGF-beta 1 in the assay for growth inhibition in CCL-64 cells, it is also equal to that of TGF-beta 1 in assays for stimulation of both anchorage-independent growth of rat NRK cells and chemotaxis of human monocytes. In contrast, in the assay for mesoderm induction, recombinant TGF-beta 3 is 10-fold more active than TGF-beta 2, inducing expression of muscle specific alpha-actin at concentrations as low as 1 ng/ml. These results suggest that more complex systems, in contrast to individual cell types, may respond selectively to the various TGF-beta isoforms and that there might be biological consequences of TGF-beta isoform switching in vivo.

Isolation and characterization of TGF-beta 2 and TGF-beta 5 from medium conditioned by Xenopus XTC cells

TGF-beta 2 and -beta 5 have been purified from medium conditioned by Xenopus cultured cells (XTC) and identified based on their N-terminal amino acid sequence analysis and biological activity. When applied in high concentrations, Xenopus TGF-beta 2, like porcine TGF-beta 2, induces expression of mesodermal markers from cultured Xenopus ectodermal explants, whereas TGF-beta 5 is inactive in this assay. However, the TGF-beta 's could be separated from the major mesoderm-inducing activity present in XTC medium. Xenopus TGF-beta 2 and -beta 5 are approximately equivalent to TGF-beta 1 in their abilities to inhibit the growth of mink lung CCL-64 cells, induce anchorage-independent growth of rat NRK cells, inhibit the proliferation and antibody secretion of human B-lymphocytes, and stimulate chemotaxis of human monocytes. These data establish the functional activity of TGF-beta 5 and suggest that more complex multicellular systems, in contrast to most isolated cells, discriminate between the different TGF-beta s.

In situ expression of transforming growth factor beta in streptococcal cell wall-induced granulomatous inflammation and hepatic fibrosis

The expression of transforming growth factor beta (TGF-beta) was examined during the evolution of streptococcal cell wall (SCW)-induced hepatic granulomas in rats to evaluate the role of TGF-beta in chronic inflammation progressing to fibrosis. As determined by immunocytochemistry, Kupffer cells rapidly expressed TGF-beta 1 following intraperitoneal (i.p.) injection of SCW, and TGF-beta was expressed by mononuclear phagocytes in the earliest cell aggregates as well as by mononuclear phagocytes within the capsule of mature lesions. Interestingly, apparent extracellular TGF-beta was observed in mature lesions at the interface of the capsule and the cellular core, a region of active fibrogenesis. Granulomas isolated 3, 6, and 12 weeks post-SCW injection elaborated nanogram (ng) quantities of latent and active TGF-beta into culture supernatants, and expressed high levels of 2.4 and 1.9 kb TGF-beta 1 transcripts. Expression of procollagen type I and III mRNAs were observed in parallel with the expression of the TGF-beta 1 transcripts. Thus, TGF-beta is expressed throughout SCW-granuloma development, and, based on known bioactivities, it appears that TGF-beta mediates, in part, the recruitment and activation of monocytes and fibroblasts and deposition of collagen in SCW-granulomas and likely other chronic inflammatory lesions progressing to fibrosis.

TGF-beta regulates production of growth factors and TGF-beta by human peripheral blood monocytes

Transforming growth factor beta 1 (TGF-beta 1) and its closely related homologue, TGF-beta 2, rapidly induce growth factor gene expression by freshly isolated human peripheral blood monocytes. Within 3 h of exposure to TGF-beta, mRNA species specific for interleukin-1 (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF) were observed. By 14-18 h, cytokine bioactivity and protein were detected in the culture supernatants. Furthermore, not only TGF-beta 1, but also TGF-beta 2 mRNA are expressed constitutively in unstimulated monocytes. However, in response to exogenous TGF-beta (beta 1 or beta 2), only TGF-beta 1 gene expression is upregulated, and the expression of TGF-beta 2 mRNA is unchanged. This selective autoinduction of TGF-beta 1 appears to be controlled at both transcriptional and post-transcriptional levels. These paracrine and autocrine activities of TGF-beta suggest potential mechanisms through which an inflammatory response can be initiated and amplified. In addition, the TGF-beta enhancement of growth factor generation may promote fibrosis and angiogenesis relevant to physiological tissue repair as well as pathological fibrotic sequelae.

Basic FGF treatment of endothelial cells down-regulates the 85-KDa TGF beta receptor subtype and decreases the growth inhibitory response to TGF-beta 1

Transforming growth factor-beta 1 (TGF beta 1) and basic fibroblast growth factor (bFGF) are known to be potent inhibitors and stimulators, respectively, of endothelial cell growth in vitro. In the present study we examined the effect of bFGF on endothelial cell growth inhibitory activity of TGF beta 1 and on the binding of (125I)-TGF beta 1 to these cells. The concentration of TGF beta 1 required for half-maximal inhibition of endothelial cell growth was increased in a dose-dependent manner by bFGF (a 20-100 fold increase at 1 ng/ml of bFGF). A 24 h-pretreatment of cells with bFGF resulted in abolition of the TGF beta 1 inhibitory effect on DNA synthesis. Moreover, the binding of (125I)-TGF beta 1 to the endothelial cell surface was decreased in a concentration-dependent and time-dependent manner after a preincubation of these cells with bFGF. Analysis of the binding parameters showed that bFGF decreased by two-fold the number of TGF beta receptors (to approximately 6000 receptors per cell). Cross-linking experiments with disuccinimidyl suberate demonstrated the presence of two TGF beta receptor subtypes, a predominant 85 kDa form and a minor 65 kDa form. Basic FGF decreased selectively the labeling of the 85 kDa TGF beta receptor subtype. These findings suggest that the growth stimulator bFGF can attenuate the cell's response to the growth inhibitor TGF beta 1.

Transforming growth factor-ßs as modulators of pericellular proteolytic events

Since the discovery of transforming growth factor-ß:s an increasing number of different biological effects have been attributed to this group of proteins. Analysis of the cellular responses to TGFß stimulation at the molecular level has indicated that TGFß acts as an activator of transcription of several genes. This may in part explain the plethora of various functions that have been ascribed to TGFß. In addition to the TGFß family of polypeptides there is an increasing number of related factors, whose major roles appear to be involved in developmental processes. A distinct feature of TGFß is its ability to regulate pericellular proteolysis of cultured cells. As yet this property has not been associated with other members of this group of polypeptides. Depending on the target cell type TGFß may either increase or decrease pericellular proteolytic activity. Proteolytic activation of latent TGFß and its possible inhibition by TGFß-induced protease inhibitors could be a physiological feed-back mechanism in the control of proteolytic activity in the vicinity of cells.

Protein factors which regulate cell motility

Cell motility (i.e., movement) is an essential component of normal development, inflammation, tissue repair, angiogenesis, and tumor invasion. Various molecules can affect the motility and positioning of mammalian cells, including peptide growth factors, (e.g., EGF, PDGF, TGF-beta), substrate-adhesion molecules (e.g., fibronectin, laminin), cell adhesion molecules (CAMs), and metalloproteinases. Recent studies have demonstrated a group of motility-stimulating proteins which do not appear to fit into any of the above categories. Examples include: 1) scatter factor (SF), a mesenchymal cell-derived protein which causes contiguous sheets of epithelium to separate into individual cells and stimulates the migration of epithelial as well as vascular endothelial cells; 2) autocrine motility factor (AMF), a tumor cell-derived protein which stimulates migration of the producer cells; and 3) migration-stimulating factor (MSF), a protein produced by fetal and cancer patient fibroblasts which stimulates penetration of three-dimensional collagen gels by non-producing adult fibroblasts. SF, AMF, and MSF are soluble and heat labile proteins with Mr of 77, 55, and 70 kd by SDS-PAGE, respectively, and may be members of a new class of cell-specific regulators of motility. Their physiologic functions have not been established, but available data suggest that they may be involved in fetal development and/or tissue repair.

Complex regulation of transforming growth factor beta 1, beta 2, and beta 3 mRNA expression in mouse fibroblasts and keratinocytes by transforming growth factors beta 1 and beta 2

Regulation of transforming growth factor beta 1 (TGF beta 1), TGF beta 2, and TGF beta 3 mRNAs in murine fibroblasts and keratinocytes by TGF beta 1 and TGF beta 2 was studied. In quiescent AKR-2B fibroblasts, in which TGF beta induces delayed stimulation of DNA synthesis, TGF beta 1 autoregulation of TGF beta 1 expression was observed as early as 1 h, with maximal induction (25-fold) after 6 to 12 h. Increased expression of TGF beta 1 mRNA was accompanied by increased TGF beta protein production into conditioned medium of AKR-2B cells. Neither TGF beta 2 nor TGF beta 3 mRNA, however, was significantly induced, but both were apparently down regulated at later times by TGF beta 1. Protein synthesis was not required for autoinduction of TGF beta 1 mRNA in AKR-2B cells. Nuclear run-on analyses and dactinomycin experiments indicated that autoregulation of TGF beta 1 expression is complex, involving both increased transcription and message stabilization. In contrast to TGF beta 1, TGF beta 2 treatment of quiescent AKR-2B cells increased expression of TGF beta 1, TGF beta 2, and TGF beta 3 mRNAs, but with different kinetics. Autoinduction of TGF beta 2 mRNA occurred rapidly with maximal induction at 1 to 3 h, enhanced TGF beta 3 mRNA levels were observed after 3 h, and increased expression of TGF beta 1 occurred later, with maximal mRNA levels obtained after 12 to 24 h. Nuclear run-on analyses indicated that TGF beta 2 regulation of TGF beta 2 and TGF beta 3 mRNA levels is transcriptional, while TGF beta 2 induction of TGF beta 1 expression most likely involves both transcriptional and posttranscriptional controls. In BALB/MK mouse keratinocytes, minimal autoinduction of TGF beta 1 occurred at only the 12- and 24-h time points and protein synthesis was required for this autoinduction. The results of this study provide an example in which TGF beta 1 and TGF beta 2 elicit different responses and demonstrate that expression of TGF beta 1, and TGF beta 3 are regulated differently. The physiological relevance of TGF beta 1 autoinduction in the context of wound healing is discussed.

Heterogeneity among human mononuclear phagocytes in their secretion of lysozyme, interleukin 1 and type-beta transforming growth factor: a quantitative analysis at the single-cell level

Human mononuclear phagocytes have the remarkable capacity to secrete a wide range of products. The reverse hemolytic plaque assay was used to visualize and quantify the secretion of lysozyme, interleukin 1 or type-beta transforming growth factor by individual monocytes and macrophages. With this sensitive immunoassay, the release of these products by either freshly isolated monocytes, macrophages derived from monocytes in vitro, or activated peritoneal macrophages was detected in both the presence and absence of secretagogues. When coupled with immunocytochemistry for EBM/11, a monoclonal marker for human cells of the monocyte/macrophage cell lineage, functional heterogeneity was evident both in the amount of lysozyme, interleukin 1 or type-beta transforming growth factor released per cell, and in the number of EBM/11+ cells which secreted detectable levels of these products at any one time. In addition, there was a size-dependent heterogeneity among human monocytes and culture-derived macrophages in their ability to secrete interleukin 1 or lysozyme, respectively. We conclude that the secretory activity of individual mononuclear phagocytes is markedly heterogeneous.

Mesoderm induction and blood island formation by angiogenic growth factors and embryonic inducing factors

Factors which induce mesoderm, including endothelium lined cavities and primitive blood cells in omnipotent amphibian ectoderm, have been isolated from different sources. Recently it was shown that angiogenic factors, which belong to the protein families of the heparin binding growth factors (acidic and basic fibroblast growth factor) and the transforming growth factors (TGF-beta 1 and -beta 2), also induce mesodermal tissues in amphibian ectoderm. In triturus ectoderm, capillary like endothelial networks are induced preferentially by the transforming growth factors. The relationship between growth factors and inducing factors is discussed.

Macrophage production of transforming growth factor beta and fibroblast collagen synthesis in chronic pulmonary inflammation

A rat model of bleomycin-induced pulmonary inflammation and fibrosis was used to examine the relationship between collagen synthesis and transforming growth factor beta (TGF-beta) production, and cellular distribution. Total lung TGF-beta was elevated within 2 h of intratracheal bleomycin administration and peaked 7 d later at levels 30-fold higher than controls. This was followed by a gradual decline with lower but persistent levels of production in the late phase of the response between 21 and 28 d later. The peak TGF-beta levels preceded the maximum collagen and noncollagen protein synthesis measured by [3H]proline incorporation into lung fibroblast explants of bleomycin-treated rats. The pattern of immunohistochemical staining localized TGF-beta initially in the cytoplasm of bronchiolar epithelium cells and subepithelial extracellular matrix. The peak of lung TGF-beta levels at 7 d coincided with intense TGF-beta staining of macrophages dispersed in the alveolar interstitium and in organized clusters. Later in the course of the response. TGF-beta was primarily associated with extracellular matrix in regions of increased cellularity and tissue repair, and coincided with the maximum fibroblast collagen synthesis. This temporal and spatial relationship between collagen production and TGF-beta production by macrophages suggests an important if not primary role for TGF-beta in the pathogenesis of the pulmonary fibrosis.

Secretion of monocyte chemotactic activity by alveolar macrophages

The purpose of this study was to determine if alveolar macrophages (AMs) are a source of monocyte chemoattractants and the role bleomycin interaction with AMs may play in the recruitment of monocytes to the lung in a rodent model of bleomycin-induced pulmonary fibrosis. AMs isolated from rats with bleomycin-induced fibrosis secreted significantly greater amounts of monocyte chemoattractants than those isolated from normal rats. When AMs from normal rats were stimulated with bleomycin in vitro, monocyte chemotactic activity was secreted into the medium. Chemotactic activity secretion by AM stimulated with 0.01 to 0.1 micrograms/ml bleomycin was significantly higher than that of cells incubated in medium alone. This activity was truly chemotactic for monocytes, but caused only minimal migration of normal AMs. Bleomycin itself at concentrations of 1 pg/ml to 10 micrograms/ml had no monocyte chemoattractant activity. Characterization of the chemotactic activity in conditioned media (CM) from bleomycin-stimulated AM demonstrated that the major portion of the activity bound to gelatin, was heterogeneous, with estimated molecular weights of 20 to 60 kd, and was inactivated by specific antifibronectin antibody. These findings suggest that fibronectin fragments are primarily responsible for the monocyte chemotactic activity secreted by AMs. Through increased secretion of such chemotactic substances, AMs could play a key role in the recruitment of peripheral blood monocytes into the lung in inflammatory lung disease and fibrosis.

Growth factors in wound healing. Single and synergistic effects on partial thickness porcine skin wounds

Several growth factors are potential mediators of wound healing, although their actual roles, interactions, and therapeutic use are not established. Six well-characterized human growth factors were chosen for detailed investigation by topical application to standardized skin wounds in swine: epidermal growth factor (EGF), transforming growth factors alpha and beta (TGF-alpha and TGF-beta), fibroblast growth factor (FGF), insulin-like growth factor-I (IGF-I), and platelet-derived growth factor (PDGF). When applied singly in doses up to 1,500 ng, only TGF-beta produced a marked tissue response, as demonstrated by an increase in the new connective tissue volume, the collagen content and maturity, and increased angiogenesis. However, TGF-beta enhanced inflammation and caused abnormal epithelial differentiation and decreased epithelial volume, the last reversed by addition of IGF-I. Recombinant PDGF-2 homodimer, if given in combination with recombinant IGF-I, caused a similar increase in the new connective tissue volume and collagen content and maturity, but without increased inflammation. In addition, this combination stimulated increased amounts of epithelium with normal differentiation. The synergy of PDGF-2 and IGF-I was optimal at a ratio of 2:1 by weight. Of the six individual factors and nine combinations tested, the combinations of PDGF-2 and IGF-I or PDGF-2 and TGF-alpha were the most potent stimulators of healing in the absence of increased inflammation.

Expression and control of vascular endothelial cells: proliferation and differentiation by fibroblast growth factors

Evidence from in vitro studies supports the concept that growth factors could be involved in the development and function of the vascular tree. Among the growth factors known to influence vascular endothelial cells' proliferation and differentiation, in vitro, are the fibroblast growth factors. These consist of two closely, structurally, related polypeptides that differ by their isoelectric point and have been called basic and acidic fibroblast growth factor. These growth factors, in particular basic fibroblast growth factor, which is expressed and synthesized by vascular endothelial cells, could influence the development, remodeling, and function of the vascular tree through regulating mechanisms involving paracrine and autocrine control of cell proliferation and differentiation.

Transforming growth factor-beta activity is potentiated by heparin via dissociation of the transforming growth factor-beta/alpha 2-macroglobulin inactive complex

The control of smooth muscle cell (SMC) proliferation is determined by the combined actions of mitogens, such as platelet-derived growth factor, and the opposing action of growth inhibitory agents, such as heparin and transforming growth factor-beta (TGF-beta). The present studies identify an interaction between heparin and TGF-beta in which heparin potentiates the biological action of TGF-beta. Using a neutralizing antibody to TGF-beta, we observed that the short term antiproliferative effect of heparin depended upon the presence of biologically active TGF-beta. This effect was observed in rat and bovine aortic SMC and in CCL64 cells, but not in human saphenous vein SMC. Binding studies demonstrated that the addition of heparin (100 micrograms/ml) to medium containing 10% plasma-derived serum resulted in a 45% increase in the specific binding of 125I-TGF-beta to cells. Likewise, heparin induced a twofold increase in the growth inhibitory action of TGF-beta at concentrations of TGF-beta near its apparent dissociation constant. Using 125I-labeled TGF-beta, we demonstrated that TGF-beta complexes with the plasma component alpha 2-macroglobulin, but not with fibronectin. Heparin increases the electrophoretic mobility of TGF-beta apparently by freeing TGF-beta from its complex with alpha 2-macroglobulin. Dextran sulfate, another highly charged antiproliferative molecule, but not chondroitin sulfate or dermatan sulfate, similarly modified TGF-beta's mobility. Relatively high, antiproliferative concentrations of heparin (1-100 micrograms/ml) were required to dissociate the TGF-beta/alpha 2-macroglobulin complex. Thus, it appears that the antiproliferative effect of heparin may be partially attributed to its ability to potentiate the biological activity of TGF-beta by dissociating it from alpha 2-macroglobulin, which normally renders it inactive. We suggest that heparin-like agents may be important regulators of TGF-beta's biological activity.

Platelet-derived growth factor and transforming growth factor-beta enhance tissue repair activities by unique mechanisms

Platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) markedly potentiate tissue repair in vivo. In the present experiments, both in vitro and in vivo responses to PDGF and TGF-beta were tested to identify mechanisms whereby these growth factors might each enhance the wound-healing response. Recombinant human PDGF B-chain homodimers (PDGF-BB) and TGF-beta 1 had identical dose-response curves in chemotactic assays with monocytes and fibroblasts as the natural proteins from platelets. Single applications of PDGF-BB (2 micrograms, 80 pmol) and TGF-beta 1 (20 micrograms, 600 pmol) were next applied to linear incisions in rats and each enhanced the strength required to disrupt the wounds at 5 d up to 212% of paired control wounds. Histological analysis of treated wounds demonstrated an in vivo chemotactic response of macrophages and fibroblasts to both PDGF-BB and to TGF-beta 1 but the response to TGF-beta 1 was significantly less than that observed with PDGF-BB. Marked increases of procollagen type I were observed by immunohistochemical staining in fibroblasts in treated wounds during the first week. The augmented breaking strength of TGF-beta 1 was not observed 2 and 3 wk after wounding. However, the positive influence of PDGF-BB on wound breaking strength persisted through the 7 wk of testing. Furthermore, PDGF-BB-treated wounds had persistently increased numbers of fibroblasts and granulation tissue through day 21, whereas the enhanced cellular influx in TGF-beta 1-treated wounds was not detectable beyond day 7. Wound macrophages and fibroblasts from PDGF-BB-treated wounds contained sharply increased levels of immunohistochemically detectable intracellular TGF-beta. Furthermore, PDGF-BB in vitro induced a marked, time-dependent stimulation of TGF-beta mRNA levels in cultured normal rat kidney fibroblasts. The results suggest that TGF-beta transiently attracts fibroblasts into the wound and may stimulate collagen synthesis directly. In contrast, PDGF is a more potent chemoattractant for wound macrophages and fibroblasts and may stimulate these cells to express endogenous growth factors, including TGF-beta, which, in turn, directly stimulate new collagen synthesis and sustained enhancement of wound healing over a more prolonged period of time.

Tissue reaction to intraperitoneal polymer implants: species difference and effects of corticoid and doxorubicin

The peritoneal cavity is a convenient site for implantation of encapsulated hormone-secreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspersed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.

Physiology and cell biology update: polypeptide growth factors and their relation to renal disease

A number of polypeptide growth factors have been shown to act on different types of renal cells, and many are produced by the kidney itself. It is unclear whether the compensatory hypertrophy that follows the destruction of nephrons is under the control of growth factors, but they undoubtedly participate in various forms of progressive renal injury, including chronic glomerular and tubulointerstitial diseases via autocrine, paracrine, and possibly even endocrine routes. As new developments occur in this rapidly changing field, it is hoped that this knowledge can be used to ameliorate the damage, halt the progression, or enhance the recovery from a disease process in the kidney and in other tissues.

Role of growth factors in inflammation and repair

Mononuclear cells generate a variety of hormone-like proteins termed growth factors that are instrumental in the evolution and resolution of inflammatory reactions. Many of these growth regulatory molecules have multifunctional properties. For example, the mononuclear cell-derived growth factors, platelet-derived growth factor (PDGF), and transforming growth factor beta (TGF-beta), are potent leukocyte chemoattractants. In addition, TGF-beta, a product of platelets, T lymphocytes, and monocytes, appears to induce the transcription of other monocyte-derived growth hormone genes. In this regard, picomolar concentrations of TGF-beta stimulate peripheral blood monocytes to transcribe the genes for PDGF (c-sis), basic fibroblast growth factor (FGF), interleukin 1 (IL-1), and tumor necrosis factor (TNF). Furthermore, levels of mRNA for TGF-beta, which is constitutively expressed in resting monocytes, are also increased by exogenous TGF-beta. Each of these monocyte products exhibits a plethora of biological activities on other cell types. T lymphocytes, in response to antigen, contribute to this network by secreting growth factors and lymphokines that regulate monocyte growth factor production.

In vitro and in vivo association of transforming growth factor-beta 1 with hepatic fibrosis

Despite extensive efforts, little progress has been made in identifying the factors that induce hepatic fibrosis. Transforming growth factor-beta (TGF-beta) has been shown to enhance collagen production, therefore its role in hepatic fibrosis was investigated. Treatment of cultured hepatic cells with TGF-beta 1 increased type I procollagen mRNA levels 13-fold due to post-transcriptional gene regulation. When two animal models of hepatic fibrosis, murine schistosomiasis and CCl4-treated rats, were examined, they both exhibited increased levels of TGF-beta 1 gene expression at times that somewhat preceded the increase in collagen synthesis. In contrast, in murine schistosomiasis, mRNA levels of tumor necrosis factor and interleukin-1 peaked early in the fibrogenic process. Immunohistochemical analysis showed TGF-beta 1 to be present in normal mouse liver and to be markedly increased in mice infected with schistosomiasis. TGF-beta 1 appeared in the hepatic parenchyma, primarily in hepatocytes. These findings strongly suggest a role for TGF-beta 1 in a pathophysiological state.

Purification and amino acid analysis of two human glioma-derived monocyte chemoattractants

Two chemoattractants for human monocytes were purified to apparent homogeneity from the culture supernatant of a glioma cell line (U-105MG) by sequential chromatography on Orange A-Sepharose, an HPLC cation exchanger, and a reverse phase HPLC column. On SDS-PAGE gels under reducing or nonreducing conditions, the molecular masses of the two peptides glioma-derived chemotactic factor 1 and 2 were 15 and 13 kD, respectively. Amino acid composition of these molecules was almost identical, and differed from other cytokines that have been reported. The NH2 terminus of each peptide was apparently blocked. When tested for chemotactic efficacy, the peptides attracted approximately 30% of the monocytes added to chemotaxis chambers, at the optimal concentration of 10(-9) M. Potency and efficacy were comparable with that of FMLP, which is often used as a reference attractant. The activity was chemotactic rather than chemokinetic. In contrast to their interaction with human monocytes, the pure peptides did not attract neutrophils. These pure tumor-derived chemoattractants can now be compared with attractants produced by normal cells and evaluated for their biological significance in human neoplastic disease.

Correlation of fibrosis and transforming growth factor-beta type 2 levels in the eye

Approximately 1 out of every 10 eyes undergoing surgery for retinal detachment develops excessive intraocular fibrosis that can lead to traction retinal detachment and ultimate blindness. This disease process has been termed proliferative vitreoretinopathy (PVR). The ability to monitor and grade this fibrotic response accurately within the eye as well as the ability to aspirate vitreous cavity fluid bathing the fibrotic tissue makes this an ideal setting in which to investigate the development of fibrosis. Although laboratory studies have recently shown that transforming growth factor-beta (TGF-beta) can enhance fibrosis, little clinical evidence is yet available correlating the level of this or other growth factors with the degree of fibrosis in a clinical setting. We have found that vitreous aspirates from eyes with intraocular fibrosis associated with PVR have more than three times the amount of TGF-beta (1,200 +/- 300 pM [SEM]) found in eyes with uncomplicated retinal detachments without intraocular fibrosis (360 +/- 91 pM [SEM]). Using an in vitro assay, 84-100% of the TGF-beta activity could be blocked with specific antibodies against TGF-beta 2, whereas only 10-21% could be blocked by specific antibodies against TGF-beta 1. TGF-beta 1 was used in an animal model of traction retinal detachment. Since beta 1 and beta 2 have essentially identical biologic effects and only human beta 1 was available in quantities required, beta 1 was chosen for these in vivo studies. The injection of TGF-beta1 plus fibronectin (FN) but not TGF-beta1 alone into the vitreous cavity of rabbits resulted in the increased formation of intraocular fibrosis and traction retinal detachments as compared to control eyes. In previous studies, intravitreal FN levels were also found to be elevated in eyes with intraocular fibrosis.

Ovarian steroid treatment blocks a postmenopausal increase in blood monocyte interleukin 1 release

In previous studies, we showed that blood monocyte elaboration of interleukin 1 (IL-1), a known stimulator of bone resorption, was higher in osteoporotic patients with rapid bone turnover than in those with slow turnover and in nonosteoporotic subjects. Since an acceleration of bone loss following menopause contributes to the risk of osteoporosis in women, we have studied the effects of menopause and ovarian steroid treatment on IL-1 release by monocytes obtained from nonosteoporotic and osteoporotic women. IL-1 activity in the monocyte culture medium derived from untreated postmenopausal women (nonosteoporotic and osteoporotic) was higher than in the medium derived from either untreated premenopausal or estrogen/progesterone-treated postmenopausal women. A significant negative correlation was found between IL-1 and years since menopause in both the healthy (r = -0.75; P less than 0.005) and the osteoporotic (r = -0.61; P less than 0.01) untreated postmenopausal women. The difference between the two slopes was significant at P less than 0.05. Premenopausal IL-1 levels were achieved within 8 years of menopause in the nonosteoporotic, but not in the osteoporotic, subjects in whom increases were evident as long as 15 years after menopause. IL-1 also correlated inversely with vertebral mineral density (r = -0.37; P less than 0.05), as measured by quantitative computed tomography. In prospective studies, treatment with estrogen/progesterone for 1 month caused a substantial highly significant decrease in IL-1 activity in each of three nonosteoporotic and five osteoporotic women, confirming the apparent effect of hormone therapy observed in the cross-sectional analysis. Although a cause-effect relationship has not been established, it is our hypothesis, based on these data, that alterations in IL-1 production may underlie the postmenopausal acceleration in bone loss and its inhibition by ovarian steroids. Persistent elevation of IL-1 secretion appears to be a feature of postmenopausal osteoporosis.

Transforming growth factor-beta does not alter interleukin-1 expression in cultured human macrophages

Transforming growth factor-beta (TGF beta) is a growth modulator that stimulates the growth of fibroblastic cells but inhibits the growth of cells of epithelial origin. TGF beta also influences the production of extracellular matrix proteins, and of proteases and the type 1 plasminogen activator inhibitor (PAI-1) by cultured cells. TGF beta appears also to have various immunoregulatory effects, suppressing both T- and B-cell activities. It has been proposed that it might increase the expression of interleukin-1 (IL-1) mRNA in cultured human monocytes, thus potentiating immune functions. To analyze the role of TGF beta in IL-1 production we have now quantitated the effect of this factor on the production of biologically active IL-1 as well as IL-1 beta mRNA expression. The effect of TGF beta on IL-1 production optimally activated with bacterial lipopolysaccharide (LPS) was also studied. It was found that IL-1 activity and mRNA levels were rapidly elevated by LPS but not by TGF beta. Culture fluids from monocytes treated with TGF beta alone or with TGF beta plus LPS inhibited the proliferation of the test thymocytes. After gel filtration, the media from TGF beta-treated cultures showed no activity in the molecular weight area of IL-1 (approx. 15 kD), while the supernatants from TGF beta plus LPS-induced cells contained IL-1 activity in these fractions, the magnitude of which was, however, at the same level as in the culture fluids derived from cells stimulated with LPS alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Transforming growth factor beta reverses the glucocorticoid-induced wound-healing deficit in rats: possible regulation in macrophages by platelet-derived growth factor

Transforming growth factor beta (TGF-beta) and the platelet-derived growth factor (PDGF) are potent mitogenic polypeptides which enhance rates of wound healing in experimental animals; in contrast, glucocorticoids inhibit wound repair. The potential of TGF-beta and PDGF to reverse this inhibition in healing was tested in methylprednisolone-treated rats with deficits in skin wound strength of 50%. Single applications of TGF-beta (10-40 pmol per wound, 0.25-1 micrograms) applied locally at the time of wounding fully reversed this deficit in a concentration-dependent and highly reproducible manner. Wounds in glucocorticoid-treated animals were characterized by a near total absence of neutrophils and macrophages and by a delayed influx and reduced density of fibroblasts; however, such wounds treated with TGF-beta showed significant increases in wound fibroblasts and in intracellular procollagen type I. PDGF did not reverse the deficit in wound breaking strength in glucocorticoid-treated rats; there were more fibroblasts in the PDGF-treated wounds, but these fibroblasts lacked the enhanced expression of procollagen type I found in TGF-beta-treated wounds. The wound macrophages, required for normal tissue repair, remained absent from both PDGF- and TGF-beta-treated wounds in glucocorticoid-treated animals. This result suggested that macrophages might normally act as an intermediate in the induction of procollagen synthesis in fibroblasts of PDGF-treated wounds and that TGF-beta might bypass the macrophage through its capacity to stimulate directly new synthesis of procollagen type I in fibroblasts. Whereas PDGF does not stimulate procollagen synthesis, in a rodent macrophage cell line, PDGF induced a highly significant, time-dependent enhancement of expression of TGF-beta.

Purification and amino acid analysis of two human glioma-derived monocyte chemoattractants

Two chemoattractants for human monocytes were purified to apparent homogeneity from the culture supernatant of a glioma cell line (U-105MG) by sequential chromatography on Orange A-Sepharose, an HPLC cation exchanger, and a reverse phase HPLC column. On SDS-PAGE gels under reducing or nonreducing conditions, the molecular masses of the two peptides glioma-derived chemotactic factor 1 and 2 were 15 and 13 kD, respectively. Amino acid composition of these molecules was almost identical, and differed from other cytokines that have been reported. The NH2 terminus of each peptide was apparently blocked. When tested for chemotactic efficacy, the peptides attracted approximately 30% of the monocytes added to chemotaxis chambers, at the optimal concentration of 10(-9) M. Potency and efficacy were comparable with that of FMLP, which is often used as a reference attractant. The activity was chemotactic rather than chemokinetic. In contrast to their interaction with human monocytes, the pure peptides did not attract neutrophils. These pure tumor-derived chemoattractants can now be compared with attractants produced by normal cells and evaluated for their biological significance in human neoplastic disease.

Purification and amino acid analysis of two human glioma-derived monocyte chemoattractants

Two chemoattractants for human monocytes were purified to apparent homogeneity from the culture supernatant of a glioma cell line (U-105MG) by sequential chromatography on Orange A-Sepharose, an HPLC cation exchanger, and a reverse phase HPLC column. On SDS-PAGE gels under reducing or nonreducing conditions, the molecular masses of the two peptides glioma-derived chemotactic factor 1 and 2 were 15 and 13 kD, respectively. Amino acid composition of these molecules was almost identical, and differed from other cytokines that have been reported. The NH2 terminus of each peptide was apparently blocked. When tested for chemotactic efficacy, the peptides attracted approximately 30% of the monocytes added to chemotaxis chambers, at the optimal concentration of 10(-9) M. Potency and efficacy were comparable with that of FMLP, which is often used as a reference attractant. The activity was chemotactic rather than chemokinetic. In contrast to their interaction with human monocytes, the pure peptides did not attract neutrophils. These pure tumor-derived chemoattractants can now be compared with attractants produced by normal cells and evaluated for their biological significance in human neoplastic disease.

The effect of in vivo T helper and T suppressor lymphocyte depletion on wound healing

The role of T lymphocytes in wound healing is still not well-defined. Because it had been previously shown that in vivo depletion of T cells leads to impaired wound healing, the effect of depleting T cell subsets on subsequent fibroplasia was studied. T helper/effector cells were depleted by the use of the monoclonal antibody GK1.5, reactive against the L3T4 antigen (CD4). T suppressor/cytotoxic lymphocytes were depleted by using the 2.43 monoclonal antibody reactive against the Lyt 2 antigen (CD8). In the first experiment, Balb/c mice were treated with the antibodies starting at 24 hours before wounding was performed, and weekly thereafter. Depletion of the T helper/effector cells had no effect on wound-breaking strength or hydroxyproline deposition in sponge granulomas, whereas depletion of T suppressor/cytotoxic cells significantly enhanced both of these healing parameters. In a second experiment, T cell subset depletion was started on Days 0, 3, 7, 10, and 14 postwounding, and treatments were continued weekly thereafter. Once again, depletion of T helper/effector cells had no effect on wound healing, whereas depletion of T suppressor/cytotoxic cells markedly increased both wound-breaking strength and collagen synthesis. In conclusion, the data show that T suppressor/cytotoxic cells have a counter-regulatory role in wound healing, whereas the T cell subset responsible for up-regulating wound healing remains to be identified.

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

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

Autoregulation of interleukin 1 production

Interleukin 1 (IL 1) alpha and beta are distinct cytokines with a common receptor on target cells. Both have been implicated in immunity, inflammation and connective tissue metabolism. Their production is stimulated by microbial products and also by other cytokines derived from accessory cells and lymphocytes. Following reports that IL 1 can stimulate its own production, we have tested the effects of recombinant IL 1 on the synthesis and release of IL 1 alpha and beta by human blood mononuclear cells (MNC). We confirmed that autoinduction occurs but report also the novel finding that this effect is very concentration dependent. At some concentrations within the range found in vivo, recombinant IL 1 not only failed to stimulate further IL 1 production but also inhibited the background level of synthesis in 20-h MNC cultures. The negative feedback appears unrelated to prostaglandin E2 and interferon-gamma levels and could not be reproduced by adding transforming growth factor beta. This previously unrecognized autoregulation may be relevant to clinical diseases associated with pathogenic over-production of IL 1.