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Eight human malignant fibrous histiocytomas were examined in vitro, in order to relate their growth properties to mRNA expression for platelet-derived growth factor (PDGF), PDGF receptor (PDGF-R), transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor (EGF-R). Reverse transcriptase-polymerase chain reaction (RT-PCR) showed that all cell lines expressed mRNA for PDGF-R alpha and/or PDGF-R beta; six cell lines expressed mRNA for the PDGF-A chain, with one cell line coexpressing PDGF-B chain mRNA; seven cell lines expressed mRNA for TGF-alpha whereas six cell lines expressed EGF-R mRNA. Conditioned medium from three cell lines contained PDGF; none of the cell lines released TGF-alpha. Two cell lines grew without serum requirements; whereas both expressed mRNA for PDGF, PDGF-R, TGF-alpha and EGF-R, other cell lines, unable to grow without serum, showed the same combination of growth factor/growth factor receptor expression. The two cell lines able to grow without serum were also shown to be stimulated by the addition of PDGF-BB. These findings show that simultaneous expression of mRNA for a growth factor and its receptor does not necessarily imply an autocrine or paracrine loop. However, two of our cell lines fulfil the requirements of possible PDGF-related autocrine and paracrine regulation.

We followed the response of muscle following mild intentional injury to determine a temporal sequence of cellular events involved in muscle repair. We found that intramuscular saline injection induced mild damage to muscle which resulted in the gradual recruitment of mast cells. Around the needle track, mast cells appear around 8 h post-injection. Mast cell accumulation were most dramatic immediately neighboring the posterior tibial vessels supplying the injured muscle. Dystrophin-deficient mdx muscle showed mast cell accumulations 3-fold higher than normal muscle, and this number did not change after saline injection. Additionally, we show that stem cell factor (SCF), a known mast cell chemoattractant, is expressed in both normal and mdx muscle at high levels. This steady-state level did not appear to be influenced by injury or dystrophin status. The implications of these findings are discussed as they relate to the repair of injured muscle and to their possible significance in the pathophysiology of Duchenne muscular dystrophy.

We have previously demonstrated that human promyelocytic HL-60 cells express transforming growth factor-alpha (TGF-alpha) during granulocytic differentiation. The present experiments were carried out in order to determine whether cells differentiated towards monocytes/macrophages will analogously express the TGF-alpha proto-oncogene product. HL-60 cells were induced to differentiate with 1 microM 1,alpha 25-dihydroxycholecalciferol (vitamin D3), and the human monocytoid cell line, U-937, was induced with 1 microM retinoic acid (RA), 0.1 microM vitamin D3, or 0.16 microM phorbol-12-myristate-13-acetate (PMA), ie experimental protocols known to induce monocyte/macrophage differentiation in these cells. In HL-60 cells, lacking constitutive TGF-alpha mRNA, vitamin D3 caused expression of the TGF-alpha gene and protein as demonstrated by Northern blot analysis and enzyme-linked immunoabsorbant assay (ELISA). In U-937 cells, showing constitutive TGF-alpha expression, RA but not vitamin D3 or PMA, caused marked increase in TGF-alpha mRNA (approximately 5-fold) and protein (approximately 3-fold) levels. In both cell lines the increase in TGF-alpha mRNA was evident within 24 h and continued throughout the observation period. Thus, it is established that differentiation of human leukemia cells towards monocytes/macrophages may be accompanied by TGF-alpha gene and protein expression in vitro. This is in conformity with the observed ability of mature activated macrophages to produce TGF-alpha.

We have previously demonstrated a constitutive expression of transforming growth factor alpha (TGF-alpha) in normal human blood eosinophils, both at the mRNA and protein level. This may indicate a novel function of the eosinophil, the regulation of which has not been clarified. Therefore human white blood cells (WBC) were treated with potential regulators of eosinophil function. Northern blot analysis demonstrated that human recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) caused a time and dose-dependent 2- to 3-fold increase of TGF-alpha mRNA levels, in relation to incubation in the absence of cytokine; maximal response was attained within 4 h of incubation. In contrast, IL-5 failed to influence the expression of the TGF-alpha gene. In situ analysis of GM-CSF- or IL-3-stimulated cells showed that eosinophils remained the sole cell type expressing TGF-alpha mRNA. However, whereas GM-CSF significantly induced, within 1 h, release of immunoreactive TGF-alpha protein, IL-3 was insufficient in this respect. In conclusion, our findings indicate that expression of TGF-alpha gene and protein in normal blood eosinophils is differently regulated by GM-CSF and IL-3.

Transforming growth factor alpha (TGF-alpha) is a pleiotropic factor mediating numerous cellular responses in normal and transformed cells. This includes differentiation, proliferation, migration, and formation of extracellular matrix. TGF-alpha has been demonstrated in circulating eosinophils from the idiopathic hypereosinophilic syndrome and in differentiating promyelocytic leukemia cells in vitro. Whether TGF-alpha production also occurs in normal human blood cells is not known. Northern blot analysis showed that normal human white blood cells consistently expressed the TGF-alpha gene in 47 out of 47 donors. Cell preparations enriched in mononucleated cells, and devoid of granulocytes, showed no TGF-alpha mRNA. In situ hybridization experiments assigned the TGF-alpha gene expression to the eosinophils; 100% of the eosinophils and no other cell types were specifically recognized by the complementary human TGF-alpha riboprobe. White blood cells, incubated at 37 degrees C for up to 6 hours, released immunoreactive TGF-alpha to the incubation medium, as determined by ELISA. In contrast, no TGF-alpha protein was detected in the incubation medium of mononuclear cells. It is concluded that TGF-alpha is constitutively produced and released by normal human blood eosinophils. TGF-alpha provided by eosinophils, may participate in the inflammatory reaction by interacting with mesenchymal and epithelial cells, thus promoting fibrosis or neovascularization.

Two Ca(2+)-binding proteins important in regulating muscle responses to Ca2+ flux are differentially expressed following denervation of Xenopus laevis gastrocnemius. Levels of parvalbumin (PV) RNA transcripts and proteins decrease in abundance, while calmodulin (CaM) transcript and protein levels increase. Our studies on PV kinetics in Xenopus follow a pattern observed in other species, however, our observation of a concomitant increase in CaM has not been documented in any system. Molecular analyses of the Xenopus CaM gene indicate that its structure and upstream sequences are highly conserved across several vertebrate species and implicate several transcription factors in the regulation of its expression.

We have used polymerase chain reaction to accelerate our analysis of recombinant lambda-cDNA clones. We have amplified the inserts of lambda gt10 or lambda gt11 recombinants starting with bacteriophage in cored plaques or isolated DNA. The amplifications made with simple or complex oligonucleotide primers have allowed convenient sizing, subcloning and translation of the phage inserts into protein.