Modulation of extracellular proteolytic activity and anchorage-independent growth of cultured cells by sarcoma cell-derived factors: relationships to transforming growth factor-beta

TGF beta 1 regulation of collagen metabolism by embryonic palate mesenchymal cells

Proper metabolism of the extracellular matrix (ECM) in mammalian embryonic palatal tissue is required for normal development of the palate. In particular, perturbation of collagen metabolism in the embryonic orofacial region results in the production of cleft palate. Although several types of collagen have been localized in the embryonic palate, factors responsible for regulating their synthesis have not been identified. Transforming growth factor beta (TGF beta), shown to be capable of modulating ECM metabolism in other tissues, has been localized in the developing palate. Thus, we examined the ability of TGF beta 1 to modulate collagen synthesis and degradation in murine embryonic palate mesenchymal (MEPM) cells in vitro. Immunohistochemical analysis confirmed that type III collagen was predominant in the mesenchyme of the embryonic palate, whereas type I collagen was ubiquitous throughout palatal epithelium and mesenchyme. Total collagen production by TGF beta-treated confluent MEPM cells in serum-free conditioned medium was determined by measuring incorporation of L-[2-3-4-5-3H]proline into hydroxyproline. Treatment for 24 hr with TGF beta 1 stimulated incorporation into both cell layer and medium fractions. Quantification of collagen types by ELISA indicated that TGF beta 1 stimulated the accumulation of type III collagen as early as 3 hr after treatment. Northern blot analysis of MEPM cells treated with TGF beta 1 revealed that steady-state levels of mRNA encoding for procollagen alpha 1 (I) and alpha 1 (III) were increased and that these effects were ablated by cycloheximide but not actinomycin. The effects of TGF beta treatment on MEPM cell collagen levels also reflected alterations in collagen degradation. TGF beta-treated MEPM cells exhibited a significant diminution of total protease activity. Moreover, analysis by substrate gel electrophoresis indicated specific decreases in vertebrate collagenase and stromelysin. These data represent the first report of changing proteolytic profiles during palatogenesis. Thus, TGF beta regulates the amount of collagen present in embryonic palatal tissue at the level of synthesis and degradation.

An investigation into the role of inflammatory cells in Dupuytren's disease

An immunohistochemical study was performed on nodules excised from the palmar fascia of patients with Dupuytren's contracture. In cellular nodules, antibodies to actin (used as a marker for myofibroblasts), desmin, vimentin, Mac 387 (a macrophage marker) and leucocyte common antigen were used. A correlation was demonstrated between the numbers of macrophages and the presence of myofibroblasts. The presence of myofibroblasts is generally considered to indicate the active stage of the disease. Inflammatory cells other than macrophages were largely absent from the nodules, although lymphocytes were frequent in the tissue around the nodules. Microvascular changes were prominent in the nodules and pericyte proliferation was observed around occluded capillaries. Release of growth factors from macrophages may be important in Dupuytren's contracture, as is the case in other fibrotic diseases. The possible role of macrophages in the aetiology of Dupuytren's disease is discussed.

Sustained arterial injury and progression of atherosclerosis

In this paper the following findings were described: 1) Murine arteriosclerosis induced by immune challenge was ultrastructurally characterized by intimal monocyte-macrophage recruitment and minor endothelial alterations; 2) Atherosclerotic lesions of human coronary arteries exhibited frequently segmental or patchy neovascularization, probably representing a response to intimal injury as an example of repair process. Newly formed blood vessels in the intima were derived from both adventitial and luminal endothelial growth; 3) Angiogenesis in vitro was related to the activation of fibrinolytic system especially via the autocrine production of u-PA from endothelial cells, and this process was modulated by cytokines and TGF beta. These findings add more evidence for the hypothesis that the chronic inflammation-repair process plays an essential role in the initiation and progression of atherosclerosis.

Isolation of two new proteins from bovine colostrum which stimulate epidermal growth factor-dependent colony formation of NRK-49F cells

Defatted bovine colostrum and decaseinated whey contain biological activity similar to that of TGF-beta in that they stimulate the anchorage-independent growth of NRK-49F cells in the presence of EGF. Two new proteins with such activity, termed BC-1 and BC-2, were isolated from decaseinated colostrum by a sequence of DEAE-Sephacel chromatography, Sephadex G-100 gel filtration in 1 M acetic acid, Sephadex G-50 re-gelfiltration in 8 M urea-1 M acetic acid and reverse-phase FPLCs. The two proteins showed distinctly different molecular weight from that of TGF-beta 1. BC-1 was a small Mr peptide of 8.5 kD. BC-2 had molecular mass of 46 kD, which yielded peptides of 46,40, and 6 kD on reduction. In contrast to TGF-beta, both proteins did not lose their biological activity on reduction. Both BC-1 and BC-2 suppress DNA synthesis in concanavalin A-stimulated thymocytes. These results suggest that BC-1 and BC-2 belong to a new class of mitogen/inhibitors, though their biological activities resemble those of TGF-beta.

Transforming growth factor-ßs as modulators of pericellular proteolytic events

Since the discovery of transforming growth factor-ß:s an increasing number of different biological effects have been attributed to this group of proteins. Analysis of the cellular responses to TGFß stimulation at the molecular level has indicated that TGFß acts as an activator of transcription of several genes. This may in part explain the plethora of various functions that have been ascribed to TGFß. In addition to the TGFß family of polypeptides there is an increasing number of related factors, whose major roles appear to be involved in developmental processes. A distinct feature of TGFß is its ability to regulate pericellular proteolysis of cultured cells. As yet this property has not been associated with other members of this group of polypeptides. Depending on the target cell type TGFß may either increase or decrease pericellular proteolytic activity. Proteolytic activation of latent TGFß and its possible inhibition by TGFß-induced protease inhibitors could be a physiological feed-back mechanism in the control of proteolytic activity in the vicinity of cells.