Platelet-derived growth factor or basic fibroblast growth factor induce anchorage-independent growth of human fibroblasts

Collagen-derived dipeptide, proline-hydroxyproline, stimulates cell proliferation and hyaluronic acid synthesis in cultured human dermal fibroblasts

Orally ingested collagen undergoes degradation to small di- or tripeptides, which are detected in circulating blood 2 h after ingestion. The influence of collagen-derived peptides on dermal extracellular matrix components and cell proliferation was studied using cultured human dermal fibroblasts. Of the various collagenous peptides tested here, the dipeptide proline-hydroxyproline (Pro-Hyp) enhanced cell proliferation (1.5-fold) and hyaluronic acid synthesis (3.8-fold) at a dose of 200 nmol/mL. This was concomitant with a 2.3-fold elevation of hyaluronan synthase 2 (HAS2) mRNA levels. Small interfering RNA (siRNA)-mediated knockdown of the HAS2 gene in human dermal fibroblasts inhibited Pro-Hyp-induced HAS2 mRNA transcription and cell mitotic activity. Addition of genistein or H7, a protein kinase inhibitor, abolished the Pro-Hyp-induced HAS2 mRNA stimulation. Pro-Hyp elevated phosphorylation of signal transducer and activator of transcription 3 (STAT3) within a short time period (60 min). These results suggest that Pro-Hyp stimulates both cell mitotic activity and hyaluronic acid synthesis, which is mediated by activation of HAS2 transcription.

Modulation of the anchorage-independent phenotype of human lung fibroblasts obtained from fibrotic tissue following culture with retinoid and corticosteroid

Fibroblast heterogeneity has been documented in fibrotic tissue from lung and skin. Differences have been demonstrated in proliferative rates in fibroblasts derived from fibrotic lung tissue as compared to normal. Fibroblast lines derived from adult fibrotic lung tissue and neonatal normal lung tissue exhibit colony growth in soft agarose culture, whereas fibroblast cell lines from normal adult lung tissue do not. The characteristic of anchorage-independent growth is consistent with the aggressive nature of the disease and with developmental lung growth. In this study, fibrotic lung fibroblasts were exposed to growth and differentiating factors to determine whether the anchorage-independent phenotype can be modulated. The results indicate that treatment of fibrotic lung fibroblasts with retinoic acid, known to modify matrix gene expression and induce differentiation, inhibits the cells ability to form colonies under soft agarose growth. Treatment with all-trans-retinoic acid yielded the greatest effect inhibiting both IPF and neonatal lung fibroblast anchorage-independent growth approximately 90% at 10(-6) M. Treatment of IPF fibroblasts with all-trans-retinoic acid also inhibited corticosteroid-induced colony growth. Modulation of the "fibrotic" fibroblast phenotype through retinoid therapy may prove beneficial as a potential therapeutic strategy.

Immunolocalization of transforming growth factor beta 1 and epidermal growth factor receptor epitopes in mouse incisors and molars with a demonstration of in vitro production of transforming activity

Day-14 lower incisors and day-18 first lower molars of mouse embryos produced in vitro transforming activities for non-confluent NRK cells co-cultured in agar, and mitogenic activities for exponentially growing NRK and BHK cells. The patterns of distribution of TGF beta 1 and EGF receptor, both known to regulate cell proliferation, differentiation and transformation in vitro and suspected to play important roles in developmental processes, were studied during mouse odontogenesis by means of indirect immunofluorescence on fixed or frozen fixed sections. TGF beta 1 epitopes were detected in the stellate reticulum of day-13 to day-16 incisors and of molars from day-17 onwards. Dental mesenchyme of day-14 incisors and postnatal molars, and peridental mesenchyme of bud and cap stage molars and incisors were also stained by TGF beta 1 antibodies. EGF receptor was localized in the enamel organs of incisors and molars; the inner dental epithelium and later the outer dental epithelium rapidly became negative while the stellate reticulum remained stained. Incisor apical mesenchyme showed an intense reaction with EGF receptor antibodies after birth.

Differential growth factor expression in transformed mouse NIH-3T3 cells

The expression of growth factor-specific mRNA transcripts and the presence of biologically active growth factors in the conditioned medium and in the cell extracts from mouse NIH-3T3 cells transformed by different oncogenes (Ki-ras, mos, src, fms, fes, met, and trk), by a DNA tumor virus (SV40), or by a chemical carcinogen (N-nitrosomethylurea) were studied. In contrast to NIH-3T3 cells or simian virus 40 (SV40)-transformed 3T3 cells, all the other transformed NIH-3T3 cell lines expressed a 4.5 kb transforming growth factor-alpha (TGF alpha)-specific mRNA transcript and secreted immunoreactive and biologically active TGF alpha ranging from 100 to 225 ng/10(8) cells/48 h. In addition, in the transformed cell lines that were secreting elevated levels of biologically active TGF alpha, there was a 75-95% reduction in the total number of epidermal growth factor receptors on these cells. A 2.6 kb TGF beta mRNA transcript and TGF beta protein in the conditioned medium (30-140 ng/10(8) cells/48 h) was also detected in those lines expressing TGF alpha. Basic fibroblast growth factor-like activity (11-50 ng/10(8) cells) was detected in the cell lysates from NIH-3T3 cells transformed with N-nitrosomethylurea or with trk, where expression of specific 6.9 and 3.9 kb mRNA transcripts for basic fibroblast growth factor could also be found. B chain (c-sis) expression of platelet-derived growth factor was present only in trk-transformed NIH-3T3 cells in which specific c-sis 6.5 and 4.6 kb transcripts were identified. In contrast, platelet-derived growth factor A chain expression of 2.9 and 2.3 kb transcripts was found in ras-, met-, mos-, and fms-transformed NIH-3T3 cells. These results suggest that the expression of different sets of growth factors is controlled in part by structurally distinct groups of transforming genes.

Effect of retinoids on growth factor-induced anchorage independent growth of human fibroblasts

We have studied the effects of all-trans retinol, all-trans retinoic acid, and anhydroretinol, a biologically inactive retinoid, on anchorage-independent growth of human fibroblasts induced by purified growth factors. The anchorage-independence assay was conducted in medium supplemented with serum that had had its peptide growth factors inactivated by treatment with dithiothreitol and iodoacetamide. Physiologic concentrations of either all-trans retinol (0.5 microM) or all-trans retinoic acid (1.0 nM) but not anhydroretinol (0.5 microM) reduced the frequency of anchorage-independent growth of normal human fibroblasts induced by platelet-derived growth factor (PDGF). All-trans retinol was also tested for its effect on the frequency of anchorage-independent growth induced by basic fibroblast growth factor (bFGF) and was found to decrease this growth. All-trans retinol also reduced the frequency of anchorage-independent growth of the human fibrosarcoma-derived cell line, HT1080, which grew in semisolid medium without added growth factors. Inasmuch as these retinoids reduced the frequency of anchorage-independent growth induced by either PDGF or bFGF and because PDGF and bFGF bind to independent cell membrane receptors and are known to stimulate different pathways leading to DNA synthesis, the data suggest that physiologically active retinoids have an effect on a step that is common to both signal pathways.