Endothelial Cell Stimulating Angiogenesis Factor Research Articles

The vascularity of atrophic non-unions

The objective of this study was to assess the vascularity of atrophic non-unions using an experimental animal model. Twenty skeletally mature female rabbits were randomly divided into control and experimental groups that were killed 1, 8, or 16 weeks after surgery. The experimental groups underwent surgery to induce an atrophic non-union whereas the control groups underwent a similar operation but which resulted in union. Using immunocytochemical techniques blood vessels were identified in histological sections obtained from the osteotomy site. The concentration of the vessels within the osteotomy gaps was measured, as was the serum concentration of an important angiogenic factor: endothelial cell-stimulating angiogenesis factor (ESAF). The results demonstrated a significant difference between the control and the experimental groups in the concentration of vessels within the gap at 1 week but there was no significant difference between those groups at 8 weeks. There were no significant differences in the ESAF concentration between the groups at any time points. We concluded that established atrophic non-unions can be well vascularised and that measurements of serum levels of ESAF could not distinguish between those osteotomies that would unite and those that would progress to non-union.

Levels of endothelial cell stimulating angiogenesis factor and vascular endothelial growth factor are elevated in psoriasis.

Neovascularization appears to play an early and important part in the evolution of psoriatic plaques. We studied the distribution and production of two known angiogenesis factors, endothelial cell stimulating angiogenesis factor (ESAF) and vascular endothelial growth factor (VEGF), in the skin of patients with chronic plaque psoriasis and normal control subjects. Our results showed that tissue levels of ESAF and VEGF were significantly elevated in involved as compared with normal control skin (P = 0.006 and P < 0. 0001, respectively). Tissue levels of ESAF and VEGF were also raised in involved skin as compared with uninvolved skin in patients with psoriasis (P = 0.001 and P < 0.0001, respectively). Tissue levels of ESAF and VEGF in plaques of psoriasis correlated closely with the clinical severity of psoriasis (r = 0.6 and r = 0.9, respectively). Serum levels of ESAF and VEGF were significantly raised in patients with psoriasis as compared with control subjects (P = 0.001 and P = 0.02, respectively). In vitro culture studies revealed that ESAF is produced by both keratinocytes and fibroblasts in approximately equal quantities in normal skin, whereas VEGF is secreted predominately by keratinocytes. A similar pattern is seen in both involved and uninvolved skin of patients with psoriasis. However, there is increased secretion of both factors in keratinocytes and fibroblasts from involved and uninvolved skin as compared with normal control skin (P < 0.001). The increased levels and secretion in plaques of psoriasis of two molecules, ESAF and VEGF, known to promote new blood vessel formation, suggest a pathogenetic role for them in this disease.

Molecules in focus Endothelial cell stimulating angiogenesis factor

Endothelial cell stimulating angiogenesis factor (ESAF) is a small (>1000 Da) dialysable non-peptide molecule with potent angiogenic activity. ESAF activates the major pro-matrix metalloproteinases and also uniquely reactivates the complex of these active enzymes with their tissue inhibitors resulting in both active enzyme and inhibitor. These actions may be pivotal in its role as an angiogenic factor. ESAF is primarily involved in angiogenic conditions where inflammatory cells are not evident such as foetal bone growth and electrically stimulated skeletal muscles and proliferative retinopathy. However, high levels also occur in actively growing human intracranial tumours but it is not noticeably elevated in rheumatoid arthritic synovial fluid. Its extreme potency and low molecular mass make its structural determination difficult. Possible therapeutic applications would be in the treatment of ischaemic ulcers, acceleration of fracture repair, infertility and more modestly in the correction of baldness. Analogues of ESAF could be of value in treating angiogenic diseases such as psoriasis and proliferative retinopathy.

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.

Measurement of Serum Angiogenic Factor in Devascularized Experimental Tibial Fractures

Early recovery of the vasculature is of profound importance in healing fractures, but the exact role of the regenerating endothelium remains controversial. Serum activity of endothelial cell-stimulating angiogenesis factor (ESAF) was measured after tibial osteotomy in two groups of sheep over a period of 42 days. Each osteotomy was held in an instrumented external fixator, and in one group the musculoperiosteal vasculature was excluded from the osteotomy site. In the well-vascularized group (n = 4), ESAF activity was significantly higher 2-5 days after osteotomy, with a peak at 4 days (21.1 +/- 5.4, p < 0.05), and displayed a biphasic pattern of secretion with a second peak at 7 days (24.3 +/- 5.5). In the devascularized group (n = 4) overall activity was lower, with only a single peak occurring at 9 days (17.5 +/- 3.2). These findings were correlated with significant differences in structural properties and on histological examination. The early detection of such regional vascular responses may prove to be of significant clinical value in high-energy trauma, enabling prediction of those fractures at risk of delayed or nonunion.

Endothelial cell stimulating angiogenesis factor--a new biological marker for disease activity in ankylosing spondylitis?

Endothelial cell stimulating angiogenesis factor (ESAF) is raised in conditions of neovascularization, such as may occur at the endochondral surface of the bone growth plate or in association with syndesmophyte formation. Syndesmophytes are formed in response to chronic enthesitis. Twenty unselected patients with AS were studied and enthesitis was measured clinically using a previously validated enthesitis index. Biochemical and haematological markers of disease activity were measured along with ESAF. Radiographs were scored for the degree of sacroiliitis and syndesmophyte formation and all these measurements were correlated to the enthesitis index. ESAF was raised in AS compared with normal controls. ESAF correlated positively with the enthesitis index but not with any of the biochemical or haematological indices. Higher levels of ESAF were found in those with more advanced sacroiliitis. High ESAF activity may be reflecting the angiogenic process involved in new bone formation associated with sacroiliitis and syndesmophyte formation. ESAF may be a biochemical marker for disease activity in AS.

Increased endothelial cell stimulating angiogenesis factor in patients with tibial fractures

Angiogenesis is an important step in the normal process of fracture healing, irrespective of the method of fixation. Using a quantitative assay, the amount of endothelial cell stimulating factor (ESAF) has been determined in a small group of patients with tibial fractures. ESAF levels were found to be increased when compared with normal volunteers, although this increase was relatively less in fractures held with intramedullary nails than with external fixation.

Production of endothelial cell stimulating angiogenesis factor (ESAF) by chondrocytes during in vitro cartilage calcification

The aim of this study was to identify the stimulus for production of the latent collagenase and angiogenic activator ESAF by growth plate chondrocytes. Stimulation correlated most closely with matrix calcification. Alkaline phosphatase was necessary for calcification (and so stimulation of ESAF production) but we could find no evidence for a direct link with ESAF production. ESAF production was also stimulated by addition of preformed mineral to non-calcified cultures but was inhibited by dexamethasone. Protein synthesis was necessary for the stimulation of ESAF production by calcification, though ESAF is not itself a protein. Based on these findings we suggest that chondrocytes, at a suitable stage of maturation in the growth plate, are stimulated to produce ESAF by the proximity of crystals in the matrix. Stimulation, which may consist of the induction of an enzyme or transport protein, leads to the release of this potent activator of collagenolysis as part of the angiogenic cascade.

Bovine and human pineal glands contain substantial quantities of endothelial cell stimulating angiogenic factor

Using a quantitative assay the amount of a low Mr endothelial cell stimulating angiogenesis factor (ESAF) has been determined in human pineal glands and bovine brain, retina, pineal gland, liver and kidney. Pineal glands contain approximately ten times as much ESAF as the retina or grey and white matter from the cerebral cortex and a hundred times as much as highly vascular tissues such as liver and kidney. The relevance of these findings to the highly vascular nature of the pineal gland is discussed.

A synergistic effect on microvessel cell proliferation between basic fibroblast growth factor (FGFb) and endothelial cell stimulating angiogenesis factor (ESAF)

Stimulation of microvessel endothelial cells grown on collagen gels by endothelial cell stimulating angiogenesis factor was confirmed (1). The potent endothelial cell growth stimulating activity of basic fibroblast growth factor has also been demonstrated for cells grown on collagen gels. However, the growth factor activity of basic fibroblast growth factor towards microvessel endothelial cells was almost eliminated when experiments were carried out in the presence of diafiltered foetal calf serum, but was partially restored by the addition of endothelial cell stimulating angiogenesis factor to medium containing the diafiltered serum. In contrast to these observations, foetal skin fibroblasts were stimulated by basic fibroblast growth factor when grown in medium with diafiltered serum, and this stimulation was not modified by the presence of endothelial cell stimulating angiogenesis factor.

Potentiating effect of heparin in the activation of procollagenase by a low- Mr angiogenesis factor

A low- M r freely dialysable endothelial cell-stimulating angiogenesis factor (ESAF) from conditioned medium of a mouse lymphoma cell line has previously been shown to activate latent skin fibroblast procollagenase. Activation comparable with the maximum that can be achieved with trypsin is obtained with chemically undetectable amounts of the factor. We now show that when even smaller amounts of ESAF are used heparin is able to potentiate its action in this system. The relationship between this activity and the mechanism of angiogenesis, which is itself potentiated by heparin, is discussed.