Early-passage rat lung fibroblasts do not migrate in vitro to transforming growth factor-beta

Our plain-English summary of Early-passage rat lung fibroblasts do not migrate in vitro to transforming growth factor-beta, by A.R. Osornio-Vargas, V.G. Kalter, A. Badgett, et al (American Journal of Respiratory Cell and Molecular Biology, 1993).

The study

• Authors: A.R. Osornio-Vargas, V.G. Kalter, A. Badgett, N. Hernández-Rodríguez, I. Aguilar-Delfín, A.R. Brody
• Journal: American Journal of Respiratory Cell and Molecular Biology
• Published: 1993;8(5):468-71
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Lung fibrosis has been postulated to be mediated by the production of macrophage-derived growth factors that are both mitogenic and chemotactic for fibroblasts. In vitro studies from our laboratory demonstrated that alveolar and interstitial macrophages treated with iron and asbestos release platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) into the media. This conditioned media was capable of inducing proliferation and chemotaxis of primary rat lung fibroblasts (RLF). TGF-beta is known to be present in the media, and RLF have high-affinity receptors for TGF-beta. However, we found that > 95% of the chemotaxis was blocked by a polyclonal anti-PDGF antibody, whereas anti-TGF-beta did not change cell migration. TGF-beta has been described previously as a potent chemoattractant for fibroblasts. Thus, we tested the potential of purified TGF-beta to induce RLF chemotaxis in an attempt to address this apparent contradiction in results. Four separate preparations of RLFs from four different rats, Swiss 3T3 cells, human and rat fetal skin fibroblasts, and human foreskin fibroblasts were tested for chemotaxis using purified porcine TGF-beta 1 as well as human TGF-beta. None of these cells responded chemotactically to TGF-beta over a broad range of concentrations used (0.004 pg/ml to 50 ng/ml). RLF plated at different densities also did not respond to TGF-beta. On the other hand, all the fibroblast types migrated vigorously to PDGF (4 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This was a laboratory study of cells grown in dishes. No asbestos was used in these experiments. The authors' earlier work had found that rat alveolar and interstitial macrophages treated with iron and asbestos released two growth factors, PDGF and TGF-beta. In that work, an antibody against PDGF largely blocked rat lung fibroblasts from migrating toward the macrophage fluid, but an antibody against TGF-beta did not. In this study the authors tested whether purified pig and human TGF-beta attracts fibroblasts. They used early-passage lung fibroblasts from four preparations from male rats, as well as Swiss 3T3 cells, rat and human fetal skin fibroblasts, and human foreskin fibroblasts. None of these cells migrated toward TGF-beta at any concentration tested. Rat lung fibroblasts plated at three different densities also did not migrate toward it. All of the fibroblast types migrated toward PDGF. The same TGF-beta attracted rat mononuclear leukocytes and reduced the incorporation of labeled thymidine into the lung fibroblasts' DNA, which the authors took to show that it was active. The authors concluded that signaling inside cells must be understood before the role of growth factors in attracting cells can be clarified.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: in vitro laboratory experiment (cell migration assays and labeled-thymidine incorporation assays in cultured cells); published as a rapid communication
• Who was studied: Primary lung fibroblasts from four separate preparations from male CD rats, used at passage 3 or 4; Swiss 3T3 cells, fetal rat skin fibroblasts and human fetal skin fibroblasts (from ATCC); human foreskin dermal fibroblasts from a newborn; rat mononuclear leukocytes from venous blood
• Exposure: Purified porcine TGF-beta 1 and purified human TGF-beta, from 50 ng/ml down to 0.004 pg/ml for rat lung fibroblasts; human PDGF at 4 ng/ml as the positive control. No asbestos was used in these experiments; asbestos appears only in the description of the authors' earlier macrophage work.
• Main results:
  • Rat lung fibroblasts did not migrate toward any TGF-beta batch above the negative control (3 ± 2 cells per 10 high-power fields). PDGF always induced their migration (112 ± 16 cells per 10 high-power fields).
  • Rat lung fibroblasts plated at three different densities did not migrate toward TGF-beta at any of the densities. Only rat lung fibroblasts were tested at different densities.
  • Swiss 3T3, fetal rat skin (FR), human fetal skin (27 Sk) and human foreskin fibroblasts also gave negative results for TGF-beta. Their migration to 4 ng/ml PDGF was 130 ± 17, 23 ± 2.8, 35 ± 8.1 and 31 ± 5, respectively.
  • Rat mononuclear leukocytes migrated toward several TGF-beta lots, with optimal activity at 0.5 pg/ml (204 ± 19 cells per 10 high-power fields). The positive controls (zymosan-activated serum or FMLP) gave 270 ± 20 cells per 10 high-power fields.
  • Porcine TGF-beta 1 inhibited the incorporation of labeled thymidine by rat lung fibroblast cultures in a dose-dependent way: 50% inhibition at 0.005 ng/ml and maximal inhibition at 0.1 ng/ml.
• The authors' conclusion: The authors concluded that rat lung fibroblasts have high-affinity TGF-beta receptors yet do not migrate toward TGF-beta. They suggested that the signaling mechanisms inside cells must be understood before the role of growth factors as attractants can be clarified, and that investigators should be cautious in interpreting chemotaxis studies.
• Limitations the authors state:
  • The authors said they could offer no clear explanation for why their results differ from earlier reports that TGF-beta attracts fibroblasts.
  • The authors said differences in experimental conditions (such as cell type, TGF-beta source, albumin in the buffer, serum and cell density) make it difficult to compare results directly across laboratories.

Topics

Medical terms in this study, explained in our Lexicon: Fibroblast, Transforming Growth Factor-beta (TGF-β), Fibrosis, Macrophage, Interstitial, Platelet-Derived Growth Factor (PDGF).

Related studies

• Rat alveolar macrophage-derived platelet-derived growth factor is chemotactic for rat lung fibroblasts — A.R. Osornio-Vargas, J.C. Bonner, et al. (1990)
• Reduced tumor necrosis factor-alpha and transforming growth factor-beta1 expression in the lungs of inbred mice that fail to develop fibroproliferative lesions consequent to asbestos exposure — D.M. Brass, G.W. Hoyle, et al. (1999)
• Differential proliferation of rat lung fibroblasts induced by the platelet-derived growth factor-AA, -AB, and -BB isoforms secreted by rat alveolar macrophages — J.C. Bonner, A.R. Osornio-Vargas, et al. (1991)
• Transforming growth factor-beta(1) overexpression in tumor necrosis factor-alpha receptor knockout mice induces fibroproliferative lung disease — J.Y. Liu, P.J. Sime, et al. (2001)
• Susceptibility to asbestos-induced and transforming growth factor-beta1-induced fibroproliferative lung disease in two strains of mice — G.S. Warshamana, D.A. Pociask, et al. (2002)
• Distribution of transforming growth factor-beta 1, fibronectin, and smooth muscle actin in asbestos-induced pulmonary fibrosis in rats — T.D. Perdue, A.R. Brody (1994)

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