The EL2 rat fibroblasts line: differential effects of growth factors (EGF, PDGF, FGF, TPA and TGF beta) on cell proliferation and c-fos expression

Conjunctival fibrosis in ocular cicatricial pemphigoid--the role of cytokines

Ocular cicatricial pemphigoid (OCP) is a systemic, autoimmune disease characterised by conjunctival scarring that is often progressive. The pathophysiology of the fibrosis is unknown. This study aimed to determine which fibrogenic cytokines are present in the conjunctiva in patients with acute and chronic OCP as a first stage in determining the mechanisms of fibrosis. Conjunctival biopsies from patients with acute, subacute and chronic OCP (n=13) were compared to normal conjunctiva (n=10). Production of mRNA for, and expression of, transforming growth-beta1, 2 and 3 (TGF-beta), TGF-beta receptor, platelet derived growth factor (PDGF) and fibroblast growth factor (FGF) were assessed using in situ hybridisation and immunohistochemistry. Acute disease showed increased levels of mRNA for TGF-beta1 and 3, mainly in stromal fibroblasts and macrophages. In the stroma, there were concordant increases in latent and activated TGF-beta1 and 3 and TGF-beta receptor expression by fibroblasts. There were no significant increases in the expression of TGF-beta2, PDGF or FGF in acute disease. No cytokines or receptors were significantly increased in chronic disease. Acutely inflamed conjunctiva in OCP is associated with significant stromal levels of TGF-beta1 and 3 but not PDGF or FGF and none were increased in chronic disease. This suggests that TGF-beta may have a key role in the pathogenesis of the fibrosis. The absence of fibrogenic cytokines in chronic progressive OCP provides support for the proposal that fibroblasts in OCP conjunctiva may remain functionally and morphologically abnormal after the withdrawal of cytokine influences.

The immunological features and pathophysiology of ocular cicatricial pemphigoid

Ocular cicatricial pemphigoid is an uncommon but severe and potentially blinding systemic disease. It shares many pathophysiological features with the other bullous skin diseases such as dermatitis herpetiformis, bullous pemphigoid and pemphigus vulgaris. All of these diseases have circulating antibodies that bind to the basement membrane of mucous membranes. The individual diseases differ by each having a specific component of the basement membrane complex as its antigen. In acute ocular cicatricial pemphigoid, the conjunctiva is infiltrated with neutrophils, macrophages, Langerhans cells and CD8+ and CD4+ T-cells while in the chronic disease the conjunctiva is infiltrated mainly by CD8+ T-cells. There is evidence of activation of these T-cells as CD4+ cells as shown by expression of the interleukin-2 receptor and increased expression of major histocompatibility class II antigens within the tissue. The aetiology of the fibrosis is unknown but increased amounts of several fibrogenic growth factors are demonstrable by immunohistochemistry.

Specific growth factor activity identifies and predicts murine mammary tumor

In milk from substrains of mice with varying incidences of developing mammary tumor, we have isolated a specific mitogenic activity, which is unique in that it identifies mice with mammary tumor and predicts those mice that will eventually develop mammary tumor. None of the milk samples from control mice, who never developed mammary tumor, contained this specific predictive mitogenic activity. Chemical characterization has shown this specific mitogenic activity to be acid- and heat-stable and resistant to reducing agents. Partial purification, by ion-exchange, high-performance liquid chromatography size-exclusion, and isoelectrofocusing techniques, of this specific mitogenic activity from milk of mice that had or eventually developed mammary tumor identifies several peptide growth factor components in a 6-10 kDa molecular weight range. Of known growth factors, radioassay techniques identify an insulin-like growth factor-1-like peptide as a major component. Small amounts of platelet-derived growth factor and transforming growth factor-beta activities also were present. Our results suggest that a subset of growth factors that are diagnostic of the presence of murine mammary tumor and predictive of eventual tumor development may be early indicators of the transition of a competent cell to a progressively malignant state. Similar studies of a secreted body fluid from women at risk for breast cancer may lead to the identification of a specific biologic tumor marker for breast cancer.

Identification of a unique biological tumor marker in human breast cyst fluid and breast cancer tissue

Breast cyst fluid from 35 women was stratified into risk groups based on personal and family history of breast cancer. Mitogenic activity in breast cyst fluid of women at highest risk to develop breast cancer was significantly higher than the activity in the lowest-risk group. There was a direct dose-dependent relationship between mitogenic activity and increased risk of developing breast cancer. Size-exclusion chromatography showed that breast cyst fluid from women at highest risk contained two peaks of growth factor activity: less than 6 kilodaltons (kd), identified as human EGF (epidermal growth factor), and 6 to 18 kd. Moderate-risk group samples demonstrated only the single less than 6 kd peak, whereas the lowest-risk group had insignificant growth-promoting activity. Breast cancer tissue analyzed in a similar manner revealed a predominant 6- to 14-kd peak of mitogenic activity demonstrating the same acid- and heat-stability found in breast cyst fluid.

Response of bone marrow stromal cells to adipogenic antagonists

Adipocytes constitute a major part of the bone marrow stroma in vivo and may play an active role in lymphohematopoiesis. Earlier studies had shown that the bone marrow stromal cell clone BMS2 was capable of adipocyte differentiation in vitro, in addition to its well-defined ability to support B lymphopoiesis. We now demonstrate that the process of adipogenesis in this functional bone marrow stromal cell clone can be inhibited by the cytokines interleukin-1 alpha, tumor necrosis factor, and transforming growth factor beta. Exposure of preadipocyte BMS2 cells to these agents blocked the induction of adipocyte differentiation as assessed by morphologic criteria and analysis of the neutral lipid content. Both interleukin-1 alpha and tumor necrosis factor elicited a rapid transient elevation in the steady-state mRNA levels of c-fos, c-jun, and JE. When added to differentiated adipocytes, the three cytokines continued to act as adipogenic antagonists. This was indicated by concentration- and time-dependent decreases in the activity of an adipocyte-specific enzyme, lipoprotein lipase. These changes in enzyme activity correlated directly with a decrease in steady-state levels of lipoprotein lipase mRNA. Another RNA marker of adipocyte differentiation (adipsin) was less influenced by the adipogenic antagonists. This may reflect the longer half-life of this mRNA transcript compared with those of lipoprotein lipase. Our results dramatically demonstrate that the differentiation state of bone marrow stromal cells can be modulated by exogenous factors in vitro. It is also the first report that transformation growth factor beta regulates the activity of lipoprotein lipase. These data suggest potential physiologic actions for these cytokines in vivo within the overall context of lymphohematopoiesis.

Response of bone marrow stromal cells to adipogenic antagonists

Adipocytes constitute a major part of the bone marrow stroma in vivo and may play an active role in lymphohematopoiesis. Earlier studies had shown that the bone marrow stromal cell clone BMS2 was capable of adipocyte differentiation in vitro, in addition to its well-defined ability to support B lymphopoiesis. We now demonstrate that the process of adipogenesis in this functional bone marrow stromal cell clone can be inhibited by the cytokines interleukin-1 alpha, tumor necrosis factor, and transforming growth factor beta. Exposure of preadipocyte BMS2 cells to these agents blocked the induction of adipocyte differentiation as assessed by morphologic criteria and analysis of the neutral lipid content. Both interleukin-1 alpha and tumor necrosis factor elicited a rapid transient elevation in the steady-state mRNA levels of c-fos, c-jun, and JE. When added to differentiated adipocytes, the three cytokines continued to act as adipogenic antagonists. This was indicated by concentration- and time-dependent decreases in the activity of an adipocyte-specific enzyme, lipoprotein lipase. These changes in enzyme activity correlated directly with a decrease in steady-state levels of lipoprotein lipase mRNA. Another RNA marker of adipocyte differentiation (adipsin) was less influenced by the adipogenic antagonists. This may reflect the longer half-life of this mRNA transcript compared with those of lipoprotein lipase. Our results dramatically demonstrate that the differentiation state of bone marrow stromal cells can be modulated by exogenous factors in vitro. It is also the first report that transformation growth factor beta regulates the activity of lipoprotein lipase. These data suggest potential physiologic actions for these cytokines in vivo within the overall context of lymphohematopoiesis.

Stimulation of DNA Synthesis by Interferon and Transforming Growth Factor β in EL2 Rat Fibroblasts. Role of This Effect on the Expression of an EL2-Transformed Phenoptype

The proliferation of normal cells is regulated by both positive and negative growth-effects, induced by growth-stimulatory factors [e.g., Platelet Derived Growth Factor (PDGF), Fibroblast Growth Factor (FGF), Epidermal Growth Factor (EGF)] and growth-inhibitory factors [e.g., Interferons (IFNs), Transforming Growth Factor β (TGFβ), Tumor Necrosis Factor (TNF)]. To investigate these effects, we analyzed DNA synthesis in an euploid fibroblast line (EL2), recently isolated from rat embryo, stimulated with EGF and treated with TGFβ and IFN respectively. Our results show that, in opposition to what is described for other fibroblast lines, in EL2 cells the treatment with appropriate concentrations of TGFβ or IFN did not inhibit the [3H]-thymidine incorporation induced by EGF, but, on the contrary, EGF-induced DNA synthesis was greatly stimulated by the presence of TGFβ or IFN in our cell cultures. The implications of these findings for elucidating the cellular events leading to the malignant conversion are discussed.