An autocrine activity capable of substituting for serum in cell cultures

Provided that high cell densities (above 10(6)/ml) are maintained, a factor-dependent murine hemopoietic progenitor cell line (FDC-P1) will proliferate in serum-free medium. The conditioned medium (CM) from high-density FDC-P1 cells permits the serum-free survival of FDC-P1 cells even at low density, indicating the existence of a diffusible autocrine factor. The requirement of FDC-P1 for a colony-stimulating factor (either IL-3 or GM-CSF) is not abrogated by culturing the cells at high cell density or in the conditioned medium. Furthermore, the CM from FDC-P1 enhances the mitogenic stimulation of normal human skin fibroblasts (HSF) by epidermal growth factor (EGF): i.e., the lag period before entry into the cell cycle is shortened by up to 6 hr. The fibroblasts themselves secrete an activity into serum-free medium that appears to be required during mitogenic stimulation by EGF. The HSF-CM also allows FDC-P1 cells to survive and proliferate serum-free at low cell densities. Low concentrations of fetal calf serum or human plasma (0.2-2%) have the same effect as FDC-P1-CM and HSF-CM. We have tested many of the known growth factors, and none of them mimicked the autocrine serum replacing activity (ASRA). The activity in human plasma elutes from a gel-filtration column with an apparent molecular weight of 60,000. It appears as if cultured normal cells and cell lines produce molecules capable of complementing the growth factors required for the survival and proliferation of a range of cells in serum-free cultures.     

Multiple autocrine factors including an extracellular matrix protein are required for the proliferation and spreading of human colon carcinoma cells in vitro

The human colon carcinoma cell line LIM1215 proliferates and changes morphology (spread) in a cell density-dependent manner in response to epidermal growth factor (EGF). At high density, production of autocrine transforming growth factor-alpha enables the cells to proliferate and spread in the absence of exogenous EGF or serum. At low cell density (< 1 x 10(4)/cm2) EGF alone fails to elicit a mitogenic or morphological response and requires the presence of conditioned medium (derived from high cell density serum-free culture of the same cells) to exert its effects. This synergy between EGF and LIM1215 conditioned medium was investigated further. Using a low cell density assay and fractionated LIM1215 conditioned medium, we show that EGF-mediated mitogenic and morphological responses are separable. These responses are dependent on the synergistic action of a low molecular weight autocrine survival factor and an extracellular matrix-like spreading factor(s) secreted into the culture medium respectively. We find that under low cell density, serum-free conditions, EGF alone is insufficient to rescue LIM1215 from rapid apoptotic death. Catalase or LIM1215 autocrine survival factor prevent the death of LIM1215 cells and restore their proliferative (but not morphological) response to EGF, suggesting that cell death under these conditions may be the result of oxidative stress. Combination of EGF, partially purified autocrine survival and spreading factors induced proliferation and spreading of low density LIM1215 cells similar to that observed with EGF and unfractionated conditioned medium. GRGDS peptides strongly inhibited the spreading of LIM1215 cells in the presence of EGF and the partially purified autocrine spreading factor, demonstrating that integrin receptors are involved in the spreading process. Comparison of the spreading response of LIM1215 and Colo 526 cells on ASF and various adhesion proteins indicate that ASF is not collagen-I, collagen-IV, fibronectin or vitronectin. Taken together, these results support the concept that the autonomous growth of colon carcinoma cells in vitro is dependent on the synergistic interaction between several autocrine systems.     

Growth factor responsiveness declines during adulthood for human skin-derived cells

Keratinocytes and fibroblasts were obtained from upper arm biopsies of young (22-27 years) and old (60-82 years) adult donors. Keratinocytes were grown in serum-free medium containing variable quantities of either epidermal growth factor (EGF) or a bovine hypothalamic extract known to contain keratinocyte growth factor (KGF). Fibroblasts were grown in serum-free medium containing variable quantities of EGF or insulin. Paired keratinocyte cultures were plated in serum-free medium containing 20% newborn keratinocyte-conditioned medium (NM) or 20% control conditioned medium (CM). Newborn foreskin keratinocytes were plated in 20% conditioned media derived from newborn, young adult or old adult keratinocyte cultures. In spite of large inter-donor variability, keratinocyte growth significantly decreased with age (0.05 greater than P greater than 0.01). Cell yield at 7 days showed an 8-fold increase for young adults over the KGF dose range treated, but only a 4-fold increase for old adults. Young adult cells in varying concentrations of EGF achieved 3-fold to 5-fold higher densities than old, although EGF was not stimulatory for either adult age group. Donor age-associated loss of growth factor responsiveness was confirmed with dermal fibroblasts derived from the same biopsies. Newborn but not adult keratinocytes were stimulated by NM, while newborn cells were not stimulated by either young or old adult conditioned media (YM or OM). An epidermal proliferation index, incorporating both donor cell yield and cell yield of newborn cells in donor conditioned medium, was significantly different (P less than 0.01) for newborn vs. young or old adult cells. Our findings confirm that a decreased proliferative capacity is measurable within adulthood, and suggest that this decrease may be due to a reduced ability to synthesize or respond to mitogens, including autocrine factors.     

Stimulation of diploid fibroblast growth with serum-free medium conditioned by mezerein-treated monocytic leukemia cells

Medium conditioned by mezerein-treated human acute monocytic leukemia cells (THP-1) stimulated human fibroblast replication. Maximum mitogenic activity was elaborated by THP-1 cells with a 24-hr incubation in 10(-7) M mezerein (activator phase) followed by a 36-hr incubation in insulin-supplemented serum-free Roswell Park Memorial Institute (RPMI)-1640 medium (effector phase). Growth stimulation was not due to the presence of residual mezerein. We previously reported that leukemia cells also produced a growth inhibitor. Fibroblast stimulation was resolved by isoelectrofocusing into several active fractions separate from the growth inhibitory activity for malignant mammary cells. Conditioned medium was mitogenic for fibroblasts in the presence of high concentrations of fetal bovine and human whole blood sera. Growth stimulation was observed in plasma-derived serum only when supplemented with exogenous platelet-derived growth factor. Thus, this THP-1 cell product does not fulfill the role of a competence factor.     

The Fibroblast Mitogenic Activity Released from Human Basophilic Cell Line KU812 is Separate from Tryptase and PDGF Expression

The human leukaemia cell line KU812 has previously been used to study basophil differentiation. In this study the authors analysed the capacity of KU812 to produce the mast cell proteinase tryptase and to synthesize factor(s) mitogenic for fibroblasts. KU812 cells were treated with tetradecanoyl-phorbol-13-acetate (TPA), conditioned medium from the human T-cell line Mo (Mo-CM), or cultured under serum free conditions. After 4 days the cells were analysed for cell growth, differentiation, content of tryptase, and secretion of fibroblast mitogenic activity. Mo-CM and serum starvation increased the expression while TPA treatment down-regulated the expression of FcεRI-α chain. An increase in tryptase content in cell extracts was detected after 4 days of culture in serum-free medium or in the presence of Mo-CM. KU812 conditioned media was found to have a baseline expression of mitogenic activity on normal human foreskin fibroblasts that was increased after serum starvation or after treatment with TPA. Mast cell-derived tryptase has previously been reported to be mitogenic for fibroblasts, but in this study the expression of tryptase did not correlate with the expression of fibroblast mitogenic activity in KU812 cells. Furthermore, affinity-purified lung tryptase did not show any mitogenic activity. Platelet-derived growth factor was also excluded. Although the factor(s) from KU812 cells stimulating fibroblast proliferation have not been identified, our results indicate that basophils may be potential producers of growth factors inducing fibroblast proliferation.     

Removal of phytohemagglutinin from conditioned medium by affinity chromatography

Supernatants of lymphocytes cultured with phytohemagglutinin (PHA-induced conditioned medium) are known to contain residual lectin. Studies with T cells specifically sensitized against a given antigen and maintained in culture by the T cell growth factor in conditioned medium may be hampered by the presence of PHA since the lectin could induce polyclonal activation of T cells.We developed a procedure for removing lectin from conditioned medium by affinity adsorption on porcine thyroglobulin-Sepharose. The affinity method was capable of removing detectable amounts of lectin since the mitogenic capacity for peripheral blood lymphocytes was lost after adsorption. In contrast, thyroglobulin-Sepharose adsorbed CM retained good mitogenic activity and growth-supporting capacity for human cultured T cells.     

VEGF基因转染脂肪干细胞后上清液对皮肤成纤维细胞及脐静脉血管内皮细胞的影响

目的:通过慢病毒将血管内皮生长因子(VEGF)基因转染于人脂肪干细胞(HADSCs),检测其上清液(CM)中生长因子的表达,并用其上清液作用于人皮肤成纤维细胞(HDFs)及人脐静脉内皮细胞(HUVECs),观察对这2种细胞活力和迁移的影响。方法:准备HADSCs、HDFs及HUVECs 3种细胞并鉴定;将携带VEGF165基因的慢病毒转染于HADSCs,定时收集上清液;ELISA法检验上清中生长因子分泌情况;将VEGF-CM与完全培养液以一定比例混合分为5组,分别培养HDFs及HUVECs,CCK-8法检验对2种细胞活力的影响;将最佳比例的VEGF-CM、正常CM(Nor-CM)和完全培养液分别作用于HDFs及HUVECs,划痕法测试出对2种细胞迁移的影响。结果:ELISA结果表明VEGF-CM中VEGF及碱性成纤维细胞生长因子(bFGF)的表达均较Nor-CM组提高;相对于其它比例,当完全培养液与VEGF-CM以1∶2的比例混合时,HDFs和HUVECs的活力显著增强(P0.05);VEGF-CM与其它培养液相比可显著提高HDFs和HUVECs的迁移能力(P0.05)。结论:转染VEGF165基因后的HADSCs可同时增强VEGF及bFGF的分泌,其上清液可提高成纤维细胞及血管内皮细胞的活力和迁移能力。     

Growth suppression of hybrids between transformed cells and normal fibroblasts in serum-free medium: Correlation with retention of human chromosomes

Somatic cell hybrids formed by crossing PG19 mouse melanoma cells with mouse embryo fibroblasts have a reduced ability to proliferate in growth factor-unsupplemented serum-free medium relative to the parental melanoma cells. The suppression of growth of the hybrid cells in serum-free medium is attributable to a strict requirement of these cells for polypeptide growth factors (insulin plus platelet-derived growth factor, fibroblast growth factor, or epidermal growth factor). In contrast, the parental melanoma cells are able to grow without exogenously added growth factors. Fifteen hybrids derived from crosses between mouse L cells and normal human skin fibroblasts also have been tested for ability to grow in growth factor-unsupplemented serum-free medium. Depending on which human chromosomes are retained, growth of these hybrids in serum-free medium is also suppressed relative to growth of the L cell parent. There appear to be several genes on different chromosomes that are involved in suppression of serum-free growth of the fibroblast × L cell hybrids. One weak suppressor gene appears to be on the human X chromosome.     

Human mast cells express functional TrkA and are a source of nerve growth factor

Mast cells are the principal effector cells in IgE-dependent hypersensitivity reactions. Despite reports that rodent mast cells proliferate in the presence of nerve growth factor (NGF), human mast cells reportedly do not respond to this factor. To determine if human mast cells express the NGF receptors, TrkA tyrosine receptor and the low affinity NGF receptor (LNGFR), we first analyzed the mRNA expression by RT-PCR of TrkA and LNGFR in a human mast cell line (HMC-1) and in human mast cells cultured in the presence of stem cell factor. Both HMC-1 and cultured human mast cells were found to express TrkA but not LNGFR. TrkA protein was demonstrated by Western blot analysis of HMC-1 lysates. Using flow cytometric analysis and mast cell tryptase as a mast cell marker, both HMC-1 cells and cultured human mast cells were shown to co-express tryptase and TrkA. Treatment of mast cells with NGF resulted in phosphorylation of TrkA on tyrosine residues as detected by immunoblotting with an antiphosphotyrosine antibody. Furthermore, NGF induced the immediate early gene c-fos in HMC-1 cells. HMC-1 cells and cultured human mast cells were also found to express NGF mRNA, and conditioned medium from HMC-1 cells stimulated neurite outgrowth from chicken embryonic sensory ganglia in culture. This effect was blocked by anti-NGF. Thus, mast cells express functional TrkA and synthesize NGF, suggesting a mechanism by which NGF may act as an autocrine factor for human mast cells, and by which mast cells and nerves may interact.     

Modulation of Transforming Growth Factor-β Actions in Rat Osteoblast-like Cells: The Effects of bFGF and EGF

Abstract

The present study examines how the mitogenic and differentiation functions of transforming growth factor-β (TGF-β) are modulated by basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) in primary cultures of rat osteoblast-like (ROB) cells. TGF-β, bFGF, and EGF individually stimulated [³H]thymidine incorporation and cell proliferation in a dose range of 0.01-10 ng/ml. When studied in combination, high doses of bFGF and EGF were additive to low doses of TGF-β. The additive effects of bFGF and EGF on mitogenesis diminished with increasing doses of TGF-β. These three factors also decreased alkaline phosphatase activity individually within the same dose range. When cells were treated with the combined factors, only high doses of bFGF and EGF were additive to the TGF-β inhibition. We were unable to detect any change in collagen synthesis with each individual factor or in combined treatments. In addition, TGF-β or bFGF alone or in combination did not affect fibronectin synthesis. Our studies showed that the biological functions of TGF-β can be modulated by bFGF and EGF in ROB cells. The pattern of modulation is varied depending on the specific function examined.     

Conditioned media of carcinoma cells cultured in hypoxic microenvironment stimulate angiogenesis in vitro; relationship to basic fibroblast growth factor

Conditioned media (CM) harvested from human pulmonary squamous cell carcinoma (QG56), pulmonary small cell carcinoma (QG90) and gastric adenocarcinoma (MKN28) cultivated under hypoxic conditions (3% oxygen), enhanced the angiogenic activity in vitro more than those obtained under normoxic cultivation (20% oxygen). The total length of the tube structures formed by bovine capillary endothelial cells (BCEs) in the CM cultured at 3% oxygen was about 1.5 (QG56 and MKN28) or 1.9 (QG90) times longer than that at 20% oxygen. Tube formation was diminished by the preincubation of CM with anti-basic fibroblast growth factor (bFGF) IgG. After performing the fractionations of the CM and the crude extracts of cell lysates cultured using a heparin-Sepharose column, the mitogenic activity in the CM from all cancer cells at 3% oxygen was about twice that of CM at 20% oxygen, while it decreased in the cell lysates at 3% oxygen to about 40% of those at 20% oxygen. This mitogenic activity of BCEs in the CM from all cancer cells was almost totally suppressed by anti-bFGF IgG, but not with anti-vascular endothelial growth factor IgG. Hypoxia is an important factor in tumour angiogenesis by bFGF or bFGF-like molecule(s) derived from tumour cells.     

Induction of B cell responsiveness to growth factors by Epstein-Barr virus conversion: comparison of endogenous factors and interleukin-1.

Immortalized B lymphocytes produce a factor(s) that stimulates growth of B cell lines carrying Epstein-Barr virus (EBV). Stimulatory supernatants derived from B cells also exhibit interleukin-1 (IL-1) activity in costimulator assays with the D10.G4.1 helper T cell line. Experiments with purified macrophage-derived IL-1 and recombinant IL-1 beta demonstrate that IL-1 stimulates proliferation of the cell lines that respond to the factors from B lymphocyte lines. One B cell line, Ramos, an EBV-Burkitt's lymphoma, contrasts with other B cell lines in that it is refractory to the growth enhancing effects of B cell conditioned medium and macrophage-derived IL-1. When EBV was introduced into Ramos cells, growth was enhanced by the factor(s) in B cell conditioned medium (six out of seven lines); growth of EBV-converted Ramos lines (six out of seven lines) also was enhanced by IL-1. These findings demonstrate that infection of a non-responsive transformed B lymphocyte by EBV induces cellular responsiveness to factor-mediated growth stimulation.     

Transforming Growth Factor Beta Stimulates Mitogenically Mouse NIH3T3 Fibroblasts and Those Cells Transformed by the EJ-H-ras Oncogene

Abstract

TGF-β1 stimulates thymidine incorporation and the growth rate of mouse NIH3T3 fibroblasts and of those cells transformed by the EJ-H-ras oncogene (TR15 cells), in the presence and the absence of serum. Thymidine incorporation, in serum-deprived cells, is stimulated to a higher degree by 0.1-1 ng/ml of TGF-β in NIH3T3 than in TR15 cells, which have a 10-fold higher basal level of incorporation. In both cell types TGF-β1 is as active, or more active than other mitogens (TGF-α, PDGF-AB, bFGF) at the same concentration. The growth rate of NIH3T3 cells, in low serum or serum-free (S^?) medium, is stimulated by only 10 picograms/ml of TGF-β1, and that of TR15 cells, in S^? medium, by only 1 picogram/m1. In contrast, TGF-β1 inhibits mitogenically unestablished mouse embryo fibroblasts and these fibroblasts immortalized spontaneously and able to grow in S^? medium. It also inhibits the anchorage-independent growth of TR15 cells. NIH3T3 and TR15 cells respond, similarly, to TGF-β activated by acification of their culture medium. The kinetics of thymidine incorporation and of activation of the c-myc proto-oncogene, observed already after 1 hr, in treated NIH3T3 and TR15 cells, suggests a direct mitogenic stimulation. The level of activated c-myc RNA is 2-fold higher at 2 hr, and subsequently decreases relatively less in the TR15 cells.     

Hepatocyte growth inhibitory factor derived from HTLV-I(+) T cell lines: effect on the epidermal growth factor-dependent proliferation of rat hepatocytes

A human T cell leukemia virus-I infected T cell line, ATL-2, produces an interleukin-2 receptor inducing factor, adult T cell leukemia (ATL)-derived factor (ADF). In the conditioned medium (CM) of ATL-2, we found an inhibitory activity on the epidermal growth factor (EGF)-dependent proliferation of primary cultured rat hepatocytes, measured by cell number and [3H]thymidine incorporation. ATL-2 CM dose-dependently inhibited hepatocyte proliferation. This activity was fractionated by gel filtration at a molecular size of 15,000 to 40,000 and was tentatively called hepatocyte growth inhibitory factor (HGI). Further fractionation with the ion-exchange column indicated that HGI was separable from ADF. Nevertheless, there was a positive correlation between HGI and ADF production, because the HGI activity was also detected in the CM of another ADF producer cell line (HUT102), while no significant HGI activity was detected in the CM of low ADF producer cell lines, ED and MOLT4.     

A serum-free [3H]thymidine incorporation assay for the detection of transforming growth factors

Summary A rapid mitogenic assay suitable for the detection of transforming growth factors in the extracts of tissues or cells or in the medium conditioned by tumor cells in vitro is described. The method utilizes a nontumorigenic mouse embryo cell line (AKR-2B cells) maintained in serum-free conditions. Three classes of growth factors can be distinguished using this assay.     

Characterization of conditioned medium of cultured bone marrow stromal cells

It has been recognized that bone marrow stromal cell (BMSC) transplantation has beneficial effects on spinal cord injury in animal models and therapeutic trials. It is hypothesized that BMSCs provide microenvironments suitable for axonal regeneration and secrete some trophic factors to rescue affected cells from degeneration. However, the molecular and cellular mechanisms of the trophic factors involved remain unclear. In the present study, we examined the effects of trophic factors secreted by rat BMSCs using bioassays involving cultured hippocampal neurons. The conditioned medium (CM) as well as non-contact co-culture of BMSCs promoted neurite outgrowth and suppressed TUNEL-positive cells compared to serum-free D-MEM. Protein analyses of the CM by antibody-based protein array analysis and ELISA revealed that the CM contained insulin-like growth factor (IGF)-1, hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and transforming growth factor (TGF)-β1. DNA microarray analysis revealed that neurons highly expressed receptors of IGF-1 and TGF-β1. However, their expression indices remained unchanged even after the CM treatment. The individual trophic factors mentioned above or their combinations were less effective at promoting neuronal survival and neurite outgrowth than the CM. The present study showed that BMSCs secreted various kinds of molecules into the culture medium including trophic factors to promote neuronal survival and neurite outgrowth. The main trophic factors responsible remain to be elucidated.     

Development of cultured dermal substitute composed of hyaluronic acid and collagen spongy sheet containing fibroblasts and epidermal growth factor

The present study aimed to develop a two-layered cultured dermal substitute (CDS). The upper layer is a hyaluronic acid (HA) and collagen (Col) spongy sheet with or without epidermal growth factor (EGF). The lower layer is a HA spongy sheet and Col gel containing fibroblasts. The CDS is prepared in serum-free medium, followed by placing on the wound surface. Corresponding to clinical application, CDS was incubated in serum-free medium for a period of 1, 3 or 5?days, followed by placing onto the air and culture medium interface (wound surface model), and culture for 6?days using conventional culture medium supplemented with serum. Metabolic activity and cytokine production were considerably higher in EGF-incorporating CDS, as compared with EGF-free CDS. Metabolic activity of EGF-incorporating CDS was maintained for a period of 3?days, but decreased slightly after 5?days. EGF-incorporating CDS is able to effectively stimulate fibroblasts within CDS to release increased amounts of vascular endothelial growth factor and hepatocyte growth factor, which are essential for wound healing. CDS is promising for wound therapy, because there is no risk of cellular damage caused by cryopreservation, thawing and rinsing processes. The critical issue is how to reduce the cellular damage during a prolonged period of incubation in serum-free medium. EGF-incorporating CDS can be used after a period of 3–5?days incubation in serum-free medium. This period is sufficient for transport of CDS from manufacturing facilities to hospitals.     

Muscle cells produce a low molecular weight factor with anti-cancer activity

The present study describes a new low molecular weight factor released by muscle cells, which inhibits proliferation of tumor cells in vitro and in vivo, is highly specific towards tumor cells, and has no observable effect on normal cells' proliferation. What first prompted us to investigate this factor was the observation that tumor metastases are extremely rare in striated muscles. Co-culturing of striated muscle cells with malignant cells led to marked morphological alterations in the latter, in contrast to the same cells when incubated without muscle cells. A conditioned medium of striated muscle cells was prepared and its effect tested on a variety of cells. This conditioned medium (CM) inhibited proliferation of tumor cell lines of murine (B16 melanoma, Madison 109 lung carcinoma, MCA-105 sarcoma, ESB lymphoma), or of human origin (HTB-38 adenocarcinoma, T47D breast carcinoma, CX1 colon carcinoma). The proliferation of normal cells (bone marrow cells, fetal liver erythroid cells) was not affected by the CM. Flow cytometric analysis of B16 melanoma cells following incubation with the CM revealed that 63% ± 12 of the cells were in the G₀/G₁ phase of the cell cycle, compared to 47.8% ± 8 of cells incubated with a medium (not conditioned) only. The activity of the CM and of certain fractions thereof was also demonstrated in vivo: they prevented tumor growth in mice inoculated intraperitoneally with MCA-105 sarcoma cells. Partial purification of the CM revealed that the active component was a non-proteinaceous compound with a molecular weight of about 500 D. The results clearly suggest that muscle cells produce a low molecular weight factor which can selectively inhibit the proliferation of tumor cells in vitro and in vivo. This factor is neither species nor tumor specific.