Transforming growth factor-β1 (TGF-β1) is well recognized as a patient mediator of both fibrillar (collagen type I) and basement membrane (collagen type IV) production. However, tissue injury is characterized by the concomitant expression of many cytokines and/or growth factors in addition to TGF-β1, and the ultimate extent of extracellular-matrix (ECM) deposition may reflect the interacting effects of TGF-β1 and these other cytokines and/or growth factors. We, therefore, sought to determine whether other cytokines and/or growth factors, known to be produced after tissue injury, one capable either alone or in combination with TGF-β1 of modulating collagen gene expression. Collagen type I and collagen type IV gene expression was assessed in NIH-3T3 cells, a murine fibroblast-like cell line that responds to TGF-β1, with increases in both collagen type I and collagen type IV production. TGF-β1 coordinately induced production of collagen type IV messenger ribonucleic acid (mRNA) to a level 3.8-fold above its baseline value (p < 0.001) and collagen type I mRNA to a level 2.6-fold above its baseline value (p < 0.001). Of the other cytokines and/or growth factors tested, only epidermal growth factor (EGF) had significant effects on collagen mRNA expression. We report the novel observation that EGF significantly induced collagen type IV mRNA (3.0-fold; p < 0.001) but did not alter collagen type I mRNA expression. Platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), and insulin-like growth factor-1 (IGF-1) did not alter the expression of mRNA for collagen type IV or collagen type I. Addition of TGF-β1 to cytokine- and/or growth factor-treated cells increased both collagen type IV and collagen type I mRNA levels. However, collagen type IV mRNA levels were similar in cultures given TGF-β1 alone and cultures given TGF-β1 with other cytokines and/or growth factors; there were no additive, synergistic, or antagonistic effects after coadministration of TGF-β1 and other cytokines and/or growth factors. With regard to collagen type I mRNA expression, all cytokines and/or growth factors tested, with the exception of TNF-α, had no effect on collagen type I mRNA levels in TGF-β1 -treated cultures. Importantly, TNF-α antagonized the stimulatory effect of TGF-β1 on collagen type I mRNA levels. These observations support a dominant role for TGF-β1 in stimulating coordinate expression of collagen type I and collagen type IV mRNA by NIH-3T3 cells; EGF and TNF-α are capable of inducing divergent expression of the genes for these two types of collagen.
ASJC Scopus subject areas
- Pathology and Forensic Medicine