Activation of the matrix metalloproteinase inhibitor complex by a low molecular weight angiogenic factor

Capillary growth in relation to blood flow and performance in overloaded rat skeletal muscle

Rat extensor digitorum longus muscles were overloaded by stretch after removal of the synergist tibialis anterior muscle to determine the relationship between capillary growth, muscle blood flow, and presence of growth factors. After 2 wk, sarcomere length increased from 2.4 to 2.9 micrometers. Capillary-to-fiber ratio, estimated from alkaline phosphatase-stained frozen sections, was increased by 33% (P < 0.0001) and 60% (P < 0.01), compared with control muscles (1.44 +/- 0.06) after 2 and 8 wk, respectively. At 2 wk, the increased capillary-to-fiber ratio was not associated with any changes in mRNA for basic fibroblast growth factor (FGF-2) or its protein distribution. FGF-2 immunoreactivity was present in nerves and large blood vessels but was negative in capillaries, whereas the activity of low-molecular endothelial-cell-stimulating angiogenic factor (ESAF) was 50% higher in stretched muscles. Muscle blood flows measured by radiolabeled microspheres during contractions were not significantly different after 2 or 8 wk (132 +/- 37 and 177 +/- 22 ml. min-1. 100 g-1, respectively) from weight-matched controls (156 +/- 12 and 150 +/- 10 ml. min-1. 100 g-1, respectively). Resistance to fatigue during 5-min isometric contractions (final/peak tension x 100) was similar in 2-wk overloaded and contralateral muscles (85 vs. 80%) and enhanced after 8 wk to 92%, compared with 77% in contralateral muscles and 67% in controls. We conclude that increased blood flow cannot be responsible for initiating expansion of the capillary bed, nor does it explain the reduced fatigue within overloaded muscles. However, stretch can present a mechanical stimulus to capillary growth, acting either directly on the capillary abluminal surface or by upregulating ESAF, but not FGF-2, in the extracellular matrix.

Endothelial-cell-stimulating angiogenesis factor (ESAF) activates progelatinase A (72 kDa type IV collagenase), prostromelysin 1 and procollagenase and reactivates their complexes with tissue inhibitors of metalloproteinases: a role for ESAF in non-inflammatory angiogenesis

Endothelial-cell-stimulating angiogenesis factor (ESAF) has been shown to activate procollagenase and reactivate complexes of collagenase and gelatinase A with tissue inhibitor of metallo-proteinase (TIMP)-1. In the present paper we show a purification protocol for bovine pineal ESAF and that purified ESAF activates progelatinase A and prostromelysin-1. Unlike the activation of procollagenase by plasmin/plasminogen activator, which requires the presence of stromelysin for full activation, ESAF is able to activate fully all three proenzymes. Purified ESAF is also shown to reactivate the complexes of gelatinase A, collagenase and stromelysin-1 with TIMP-2. Once separated, both enzyme and inhibitor are active; however, ESAF binds to the enzyme in a manner preventing it from further inhibition by TIMP. ESAF is the only physiological molecule able to reactivate the TIMP/enzyme complex.

Endothelial stimulating angiogenic factor in early fracture healing

The early vascular response is essential for the normal progress of fracture healing and fracture site blood flow has been shown to reach a peak in the first two weeks after injury. Angiogenesis is an important step in this response as new vessel formation is necessary to vascularize the fracture haematoma and the fracture gap. Changes in serum levels of a low molecular weight endothelial stimulating angiogenic factor (ESAF) have been previously reported in a group of four patients with tibial fractures. In this group, ESAF levels were measured on three occasions only and at different time intervals. We present a more detailed profile of serum ESAF level changes in the first 14 days after the fracture.

Degradation of collagen type IV by C6 astrocytoma cells

The key event associated with the initiation of angiogenesis is the localized degradation of the vascular basement membrane. Because of its complex structure, any remodelling and/or modification of the basement membrane must involve the co-ordinated function of a number of different enzyme systems. Type IV collagen is a major protein component (60-90%) of the basement membrane and its degradation is crucial to the initiation of angiogenesis. This study has focused on the mechanisms by which C6 astrocytoma cells degrade human type IV collagen. C6 astrocytoma cells use components of two major degradative pathways to degrade collagen type IV. The major matrix metalloproteinase identified is the activated form (68-KDa) of gelatinase A (72-KDa matrix metalloproteinase) and a serine sensitive 1000-KDa collagenase type IV degrading activity which appears to have the characteristics of a novel extracellular proteasome.

Dissociation of collagenase-tissue inhibitor of metalloproteinases-1 (TIMP-1) complex--its application for the independent measurements of TIMP-1 and collagenase activity in crude culture media and body fluids

Collagenase-tissue inhibitor of metalloproteinases-1 (TIMP-1) complex was prepared from activated collagenase and TIMP-1 purified from culture media of human skin fibroblasts. After having been confirmed to be a complex by zinc chelate chromatography, the complex was demonstrated to dissociate by passage through an anti-TIMP-1 monoclonal antibody-affinity column. On the basis of above evidence, a simple strategy was set up for the independent measurements of TIMP-1 concentration, and both active and total collagenase activities in crude culture media and body fluids.

Role of the 21-kDa protein TIMP-3 in oncogenic transformation of cultured chicken embryo fibroblasts

The 21-kDa protein is an extracellular matrix (ECM) component whose synthesis is stimulated transiently during oncogenic transformation of chicken embryo fibroblasts (CEF) or after treatment of normal cells with the tumor promoter phorbol 12-myristate 13-acetate. Biochemical characterization indicates that the protein is related, but not identical, to two members of the family of tissue inhibitors of metalloproteinases, TIMP-1 and TIMP-2. The cDNA of the 21-kDa protein was recently cloned, and based upon its deduced amino acid sequence and other supporting data we propose that it is another member of this family, a TIMP-3. We now report electrophoretic purification of sufficient quantities of this protein to determine its function. The protein promotes the detachment of transforming cells from the ECM. Although its presence in the matrix may be necessary for cell release it is not the only factor involved because it does not influence the adhesive properties of nontransformed cells. It also appears to accelerate the morphological changes associated with cell transformation and stimulates the proliferation of growth-retarded, nontransformed cells maintained under low serum conditions. Based on these data we hypothesize that the 21-kDa protein promotes the development of the transformed phenotype in cultured cells.

Angiogenesis and rheumatoid arthritis: pathogenic and therapeutic implications

Rheumatoid arthritis can be considered as one of the family of 'angiogenesis dependent diseases'. Angiogenesis in rheumatoid arthritis is controlled by a variety of factors found in the synovial fluid and pannus tissue. Modulation of the angiogenic component of the disease may alter the pathogenesis of the condition, and subsequent cartilage and joint destruction, by reducing the area of the endothelium in the pannus and restricting pannus growth. Current therapeutic strategies exert, to varying extents, an inhibitory effect on the angiogenic process. In particular, the mode of action of the slow acting antirheumatic drugs may be due to their effect on the angiogenic response. The development of novel angiostatic treatments for chronic inflammatory joint disease may lead to a new therapeutic approach in controlling disease progression.

Regulation of growth plate cartilage degradation in vitro: effects of calcification and a low molecular weight angiogenic factor (ESAF)

Endothelial cell stimulating angiogenic factor (ESAF) is an activator of matrix metalloproteinases, including latent collagenase, and is released by chondrocytes during calcification. ESAF, added to cultured growth plate chondrocytes, elicited a time-dependent, 2.4-fold increase in matrix lysis (compared with 30% for IL-1). Matrix breakdown was suppressed by addition of tissue inhibitor of metalloproteinase (TIMP). Although calcification has been previously reported to stimulate ESAF production, no corresponding increase in cartilage lysis was seen in the present study. However, the level of ESAF that cultures produce during calcification is many times less than that added to the cultures in this series of experiments. We conclude that ESAF can produce dramatic increases in cartilage breakdown (apparently by activation of latent enzymes), but only at levels in excess of those stimulated by calcification. This indicates that ESAF may operate in concert with other initiators, perhaps from the invading endothelial cells.

The presence of neutral metalloproteolytic activity and metalloproteinase inhibitors in the interphotoreceptor matrix

Neutral proteolytic activity, having a pH optimum of about 7, was present in the high molecular weight fraction of bovine interphotoreceptor matrix (IPM) separated by gel filtration on Sephacryl S-500. The enzyme(s) was active toward a number of exogenous substrates, including albumin, Azocoll, and gelatin. However, it was inactive toward a synthetic substrate for bacterial collagenase. Proteolytic activity was proportional to protein; however, the time course of the reaction was nonlinear, suggesting that "activation" of a precursor form might be necessary. Of a number of specific inhibitors tested, those directed toward metalloproteinases (1,10-phenanthroline greater than EDTA greater than EGTA) proved most effective. While activity was also inhibited by sulfhydryl reagents and dithiothreitol, inhibitors specific for cysteine proteinases were ineffective. Higher specific activity was present in IPM obtained from retinal pigment epithelium (RPE) than from retina. An endogenous proteinase inhibitor(s) was also found in IPM from both RPE and retina. It was effective against the endogenous metalloproteolytic activity of IPM and also against thermolysin, but not against trypsin or papain. Fractionation of IPM on Sephacryl S-500 revealed a broad peak of inhibitory activity at molecular weights of less than 10(5) daltons. This is the first report of the presence of neutral proteolytic activity and metalloproteinase inhibitor(s) in bovine IPM. These materials may function in concert to maintain the proper level of various components within this matrix.