Opioid growth factor modulates angiogenesis

OBJECTIVE: Induced angiogenesis has recently been attempted as a therapeutic modality in patients with occlusive arterial atherosclerotic disease. We investigated the possible role of endogenous opioids in the modulation of angiogenesis. METHODS: Chick chorioallantoic membrane was used as an in vivo model to study angiogenesis. Fertilized chick eggs were incubated for 3 days, explanted, and incubated for an additional 2 days. Three-millimeter methylcellulose disks were placed on the surface of the chorioallantoic membrane; each disk contained opioid growth factor ([Met(5)]-enkephalin; 5 microgram), the short-acting opioid receptor antagonist naloxone (5 microgram), opioid growth factor and naloxone together (5 microgram of each), the long-acting opioid antagonist naltrexone (5 microgram), or distilled water (control). A second series of experiments was performed with distilled water, the angiogenic inhibitor retinoic acid (1 microgram), and vascular endothelial growth factor (1 microgram) to further evaluate our model. The developing vasculature was imaged 2 days later with a digital camera and exported to a computer for image analysis. Total number of blood vessels, total vessel length, and mean vessel length were measured within a 100-mm(2) region surrounding each applied disk. Immunocytochemical analysis was performed with antibodies directed against opioid growth factor and its receptor (OGFr). RESULTS: Opioid growth factor had a significant inhibitory effect on angiogenesis, both the number of blood vessels and the total vessel length being decreased (by 35% and 20%, respectively) in comparison with control levels (P <.005). The simultaneous addition of naloxone and opioid growth factor had no effect on blood vessel growth, nor did naloxone alone. Chorioallantoic membranes exposed to naltrexone displayed increases of 51% and 24% in blood vessel number and length, respectively, in comparison with control specimens (P <.005). These results indicate that the opioid growth factor effects are receptor mediated and tonically active. Immunocytochemistry demonstrated the presence of both opioid growth factor and OGFr within the endothelial cells and mesenchymal cells of the developing chorioallantoic membrane vessel wall. Retinoic acid significantly reduced the number and the total length of blood vessels, whereas vascular endothelial growth factor increased both the number and the length of blood vessels in comparison with the controls (P <.0001). The magnitude of opioid growth factor's effects were comparable to those seen with retinoic acid, whereas inhibition of opioid growth factor with naltrexone induced an increase in total vessel length comparable to that for vascular endothelial growth factor. CONCLUSIONS: These results demonstrate for the first time that endogenous opioids modulate in vivo angiogenesis. Opioid growth factor is a tonically active peptide that has a receptor-mediated action in regulating angiogenesis in developing endothelial and mesenchymal vascular cells.     

家兔激素性股骨头缺血坏死血管壁中差异表达基因的研究

目的 运用基因芯片技术,筛选激素影响的血管壁中主要生长因子基因的差异表达情况,进一步探讨激素性股骨头缺血坏死的发病机理. 方法中国大白兔25只.随机分为对照组(n=5),内毒素组(n=10)和模型组(n=10),利用大肠杆菌内毒素及甲泼尼龙诱导股骨头缺血坏死模型,分别取旋股内侧动、静脉,提取组织总RNA,与含有122个兔基因的寡核苷酸基因芯片杂交、洗涤、染色和扫描,分析检测数据. 结果在检测的122个基因中,差异显著的基因动脉有10个,静脉有27个,生物学信息分析发现这些基因大部分与血管生成、炎症免疫、骨化相关. 结论激素在导致股骨头缺血坏死的过程中降低了血管壁中主要促血管生长因子的转录,进而影响了其在血管壁中的生物活性.     

血管内皮生长因子单克隆抗体治疗子宫内膜异位症的实验研究

目的：观察血管内皮生长因子（VEGF）单克隆抗体（单抗）对子宫内膜异位症（EMs）血管生成的抑制作用,为从抗血管途径治疗EMs提供依据。方法：60只新鲜受精鸡蛋随机分为接种组（20枚）、接种治疗组（20枚）、单纯空白组（10枚）和空白载体组（10枚）。接种组和接种治疗组建立子宫内膜异位症鸡胚绒毛尿囊膜（CAM）模型,接种治疗组给予VEGF单抗10μg/d。单纯空白组不接种子宫内膜,空白载体组以无菌明胶海绵为载体,给予PBS20μg/d。通过显微血管计数、原位铺片及组织学观察等方法检测接种的子宫内膜组织对CAM血管生成和VEGF单抗对异位内膜病灶生长行为的影响。结果：接种组CAM血管生成反应明显增强,血管数目显著高于单纯空白组和空白载体组;接种治疗组血管数目显著低于接种组,有明显的间质坏死。结论：子宫内膜能明显促进CAM的血管生成,VEGF单抗能够显著抑制异位病灶的血管形成,并抑制子宫内膜的生长,证实抗血管途径可以作为治疗EMs的一种有效方法。     

Anti-angiogenesis in prostate cancer： knocked down but not out

Angiogenesis is a very complex physiological process, which involves multiple pathways that are dependent on the homeostatic balance between the growth factors （stimulators and inhibitors）. This tightly controlled process is stimulated by angiogenic factors, which are present within the tumor and surrounding tumor-associated stromal cells. The dependence of tumor propagation, invasion and metastasis on angiogenesis makes the inhibitors of new blood vessel formation attractive drugs for treating the malignancies. Angiogenesis can be disrupted by several distinct mechanisms： by inhibiting endothelial cells, by interrupting the signaling pathways or by inhibiting other activators of angiogenesis. This strategy has shown therapeutic benefit in several types of solid tumors, leading to Food and Drug Administration （FDA） approval of anti-angiogenic agents in the treatment of kidney, non-small cell lung, colon and brain cancers. Although no angiogenesis inhibitors have been approved for patients with metastatic prostate cancer, therapies that target new blood vessel formation are still an emerging and Dromising area of prostate cancer research.     

Combined VEGF and PDGF treatment reduces secondary degeneration after spinal cord injury

Trauma to the spinal cord creates an initial physical injury damaging neurons, glia, and blood vessels, which then induces a prolonged inflammatory response, leading to secondary degeneration of spinal cord tissue, and further loss of neurons and glia surrounding the initial site of injury. Angiogenesis is a critical step in tissue repair, but in the injured spinal cord angiogenesis fails; blood vessels formed initially later regress. Stabilizing the angiogenic response is therefore a potential target to improve recovery after spinal cord injury (SCI). Vascular endothelial growth factor (VEGF) can initiate angiogenesis, but cannot sustain blood vessel maturation. Platelet-derived growth factor (PDGF) can promote blood vessel stability and maturation. We therefore investigated a combined application of VEGF and PDGF as treatment for traumatic spinal cord injury, with the aim to reduce secondary degeneration by promotion of angiogenesis. Immediately after hemisection of the spinal cord in the rat we delivered VEGF and PDGF and to the injury site. One and 3 months later the size of the lesion was significantly smaller in the treated group compared to controls, and there was significantly reduced gliosis surrounding the lesion. There was no significant effect of the treatment on blood vessel density, although there was a significant reduction in the numbers of macrophages/microglia surrounding the lesion, and a shift in the distribution of morphological and immunological phenotypes of these inflammatory cells. VEGF and PDGF delivered singly exacerbated secondary degeneration, increasing the size of the lesion cavity. These results demonstrate a novel therapeutic intervention for SCI, and reveal an unanticipated synergy for these growth factors whereby they modulated inflammatory processes and created a microenvironment conducive to axon preservation/sprouting.     

Angiogenesis — a New Goal in Peripheral Artery Occlusive Disease Therapy

The vasculature is mostly quiescent in the normal adult, with the exception of the growth of new blood vessels during the female reproductive cycle. Recent advances in the knowledge concerning the molecular changes and the identification of genetic events in this vascular quiescence, as well as in vascular growth, has led to an increasing number of studies in which these phenomena are manipulated. Angiogenesis is the growth of new vessels from existing ones. Although new vessel formation is involved in many pathologic situations, like tumour growth, therapeutic angiogenesis has been presented as a novel method for the treatment of ischemic diseases, like peripheral arterial occlusive disease (PAOD).

In experimental studies therapeutic angiogenesis has been produced by recombinant growth-factor protein application as well as by growth factor gene therapy. Most widely studied factors belong to vascular endothelial growth factor (VEGF) or fibroblast growth factor (FGF) families. Studies have also shown that, angiogenic growth factors stimulate endothelial cell migration and accelerate endothelial repair by enhancing post-injury re-endothelization. In clinical studies angiogenic therapy has been evaluated in patients with severe vascular diseases. The results have revealed that therapy is well tolerated as well as safe and that angiogenic therapy has a clear biologic effect. However, controlled studies are still needed to answer the question whether therapeutic angiogenesis offers a real clinical benefit to patients with PAOD.     

Intramuscular administration of vascular endothelial growth factor augmenting collateral circulation in a rat hindlimb replantation model

This study evaluated the effect of exogenous vascular endothelial growth factor (VEGF) on augmentation of collateral circulation in a rat hindlimb replantation model. Twenty-eight rats, divided into four groups, underwent right hindlimb replantation. In experimental Group 1, the rats received daily intramuscular VEGF injections (1 microg/kg). In Group 2, the rats received 25 microg/kg VEGF injections. In Group 3, the rats received 50 microg/kg VEGF injections. In Group 4, the control group, rats received saline injections. Seven days after replantation, the repaired femoral vessels were excised. Seven days after excision of the femoral vessels, toe necrosis ratios of the replanted hindlimbs were grossly examined, and calf blood pressures were measured. Angiography was performed and muscle tissue was biopsied for histology. The results showed that administration of VEGF significantly decreased toe necrosis and improved calf blood pressure ratio, angiographic score, and capillary density in the replanted hindlimbs that underwent late vessel excision. The effect of VEGF was significantly dose-dependent. The authors conclude that VEGF can augment angiogenesis and collateral vessel formation in replanted limbs, and improve survival in replanted limbs with potential late arterial insufficiency.     

An Assay to Measure Angiogenesis in Human Fat Tissue

Background Inhibition of angiogenesis reverses rodent obesity. A validated assay in human fat tissue is needed to study the role of angiogenesis in human obesity. Methods Human fat tissue fragments from surgery were placed in 96-well plates, embedded in fibrin thrombin clot and overlaid with cell culture media containing 20% fetal bovine serum. After 15 days, the clots were examined by histology and electron microscopy. The effect of taxol, cobalt chloride and a heparin-steroid combination was tested in the fat tissue assay and compared to the validated human placental vein angiogenesis model (HPVAM). Results Blood vessels initiated growth and elongated from the fat tissue fragments over 15 days. Presence of blood vessels was confirmed with histology and electron microscopy. Taxol at 10⁻⁶ and 10⁻⁷ M completely inhibited angiogenesis, while Taxol 10⁻⁸ and 10⁻⁹ M and the heparin-steroid partially inhibited angiogenesis.The response to taxol and heparin-steroid was similar to that of the HPVAM, a validated angiogenesis assay. Cobalt chloride, a stimulator of vascular endothelial growth factor (VEGF) stimulated angiogenesis initiation at 10−9 M in fat tissue and the HPVAM, but at 10⁻¹⁰ M blood vessel growth was stimulated only in the fat assay. Conclusion This angiogenesis assay based on human fat tissue uses three-dimensionally intact human tissue. The vessels are derived from quiescient vessels within the fat. These properties allow the angiogenic switch to be evaluated in an in vitro setting. The angiogenic response of fat tissue is not identical to placental tissue. This assay allows exploration of angiogenesis in fat tissue.     

The role of angiogenesis in prostate development and the pathogenesis of prostate cancer

New vessel formation, a highly-regulated, active process commencing in the embryo and evident notably during the pubertal growth spurt, is essential for normal prostate development. Reactivation of this process in response to physiological stimuli, particularly hypoxia in mature tissues, occurs with new vessels forming principally from stromal components. Although angiogenesis is complex, putatively involving a multitude of angiogenic factors and inhibitors, there is powerful evidence of the importance of the VEGF system in the development of both the normal prostate and prostate cancer. Recent advances include an understanding of how castration acts through the VEGF system to inhibit angiogenesis. Stromal-endothelial and epithelial-endothelial interactions are just beginning to be investigated. A better understanding of how physiological angiogenesis is controlled should help to provide further insights into the mechanism of disregulated angiogenesis in tumours. Ultimately, new antiangiogenic agents are likely to find a role in the management of patients with prostate cancer.     

Angiogenesis--a new goal in peripheral artery occlusive disease therapy

The vasculature is mostly quiescent in the normal adult, with the exception of the growth of new blood vessels during the female reproductive cycle. Recent advances in the knowledge concerning the molecular changes and the identification of genetic events in this vascular quiescence, as well as in vascular growth, has led to an increasing number of studies in which these phenomena are manipulated. Angiogenesis is the growth of new vessels from existing ones. Although new vessel formation is involved in many pathologic situations, like tumour growth, therapeutic angiogenesis has been presented as a novel method for the treatment of ischemic diseases, like peripheral arterial occlusive disease (PAOD). In experimental studies therapeutic angiogenesis has been produced by recombinant growth-factor protein application as well as by growth factor gene therapy. Most widely studied factors belong to vascular endothelial growth factor (VEGF) or fibroblast growth factor (FGF) families. Studies have also shown that, angiogenic growth factors stimulate endothelial cell migration and accelerate endothelial repair by enhancing post-injury re-endothelization. In clinical studies angiogenic therapy has been evaluated in patients with severe vascular diseases. The results have revealed that therapy is well tolerated as well as safe and that angiogenic therapy has a clear biologic effect. However, controlled studies are still needed to answer the question whether therapeutic angiogenesis offers a real clinical benefit to patients with PAOD.     

Neoangiogenese als Rezidivursache nach Krossektomie der primären Stammvarikose

The term neoangiogenesis describes the new formation of blood vessels from pre-existing vessels in adults and has been experimentally demonstrated as a repair mechanism in destroyed veins. It has been shown radiographically that transsections near the knee can initially lead to new connections between the ends of veins through many, minute tuft-like vessels. In the further course the number of veins recedes and in the remaining veins the walls thicken leading to formation of a muscle layer. True neovasculates are characterised by a convoluted course, a scar-like embedding in situ, thin walls, lack of valves and an origin in the deep vein system. The scientific elaboration of this phenomenon has now been established as a small phlebological scientific field, which attempts to investigate whether such a neovascularisation really exists, and which criteria can be used to differentiate neovasculates from regeneration due to other causes. Of central importance is also the question what course does the new formation of vessels take, whereby the vascular endothelial growth factor (VEGF) has proven to be a potent factor of angiogenesis. The clarification of all these questions should help develop therapeutic and operative measures to exclude neovasculisation as a cause of recurrence.     

Vascular endothelial growth factor induces extracellular matrix proteins and osteopontin in the umbilical artery

Vascular endothelial growth factor (VEGF) is a mitogenic, angiogenic, and potent mediator of vascular permeability. It plays a role in injuries, contributes to edema during the acute stage of tissue damage, and promotes repair during recovery. We recently showed that VEGF serum levels of burn patients with a considerable number of damaged vessels were significantly increased. Here, we study the effects of VEGF on healthy vessels treated with a comparable VEGF concentration achieved in patients suffering heavy burns. VEGF 165 (0.2 mL of 10 ng/mL) or vehicle (saline 0.9%) was intraluminally applied to umbilical arteries for 90 min at 37 degrees C. Then, the cord was perfused for 4 hr. During perfusion, functional and biochemical parameters were kept within normal physiological ranges. Afterward, the vessels were analyzed applying morphometry, sirius red staining, polarization microscopy, Western blot analysis, and immunohistochemistry. Moreover, cultured human umbilical vein endothelial cells (HUVECs) were treated with VEGF or vehicle for 90 min and 5.5 hr to examine extracellular matrix (ECM) proteins and receptor tyrosine kinases. VEGF-treated umbilical arteries showed significant tissue edema and simultaneously an enhancement of laminin and collagen types I, III, and IV compared with control arteries. We detected an increase in Flt-1, Flk-1, osteopontin, and ss(1)-integrin. VEGF induced laminin early in HUVECs as measured by flow cytometry. In parallel, VEGF induced a higher amount of osteopontin, ss(1)-integrin, and both receptor tyrosine kinases in endothelial cells within 90 min. Intraluminal application of VEGF enhances ECM protein, osteopontin, and ss(1)-integrin production of the endothelium, while it still generates tissue edema. VEGF initiates vascular remodeling as early as it generates edema, even if the target vessel is not damaged. Osteopontin and ss(1)-integrin, both induced by VEGF, may play an important role in the vascular remodeling process.     

Angiogenesis and the tumour hypoxia response in prostate cancer: a review

The formation of new blood vessels, angiogenesis, is a highly-regulated active process that is critical for the development of the normal and malignant prostate. The vascular endothelial growth factor (VEGF) system assumes a critical role in the angiogenic process. Angiogenesis is a prerequisite for the expansion of solid tumours beyond 1-3 mm3 and is stimulated in response to a hypoxic environment. This review discusses the process of angiogenesis and the key angiogenic mediator, VEGF, and their role in tumour progression and metastasis. A better understanding of the mechanisms behind angiogenesis will ultimately lead to the development of new anti-angiogenic agents in the management of prostate cancer.     

Leiomyosarcoma of the cephalic vein: case report and review of the literature

Vascular leiomyosarcoma is extremely rare and represents < 2% of all leiomyosarcomas. The frequency of occurrence of leiomyosarcomas in veins is five times more than in arteries, with approximately half of them occurring in the inferior vena cava. Although leiomyosarcomas originating from large arteries or veins have been widely reported, similar tumors of peripheral vessels of upper extremities are extremely rare. To our knowledge, leiomyosarcomas of the cephalic vein over the wrist area have not been previously documented. We report a case of leiomyosarcoma of the cephalic vein in a 63-year-old man who presented with right hand and forearm swelling and tenderness for more than 1 year. Grossly, a solitary, elongated, white, and firm intraluminal growth tumor was infiltrative along the vessel wall with focal nodular formation and filled the lumen of cephalic vein, measuring 11 cm in length. Histological study revealed an intermediate-grade leiomyosarcoma of vascular origin.     

异种血管组织的脱细胞研究

目前,临床上涉及小口径动脉闭塞的血管疾患呈增多的趋势,然而可供选择的移植物却并不多,虽然聚四氟乙烯等材料用于大口径动脉的移植取得了较好效果,但用于小口径动脉移植的远期通畅率却不尽如人意.作为金标准的大隐静脉或自体动脉移植又受到来源、额外手术创伤与经济负担的困扰.组织工程血管的出现有望解决这个难题.以脱细胞的异种血管作为构建组织工程血管用支架目前研究的较为广泛.本文对目前常用的各种脱细胞方法及其相关的问题做一简要综述.     

Implications of human macrophage metalloelastase and vascular endothelial growth factor gene expression in angiogenesis of hepatocellular carcinoma

OBJECTIVE: To determine molecular mechanisms involved in angiogenesis of hepatocellular carcinoma (HCC). SUMMARY BACKGROUND DATA: Tumor angiogenesis is believed to derive from the balance between angiogenic stimulators and inhibitors. It has been suggested that the switch to the angiogenic phenotype requires both upregulation of the first and downregulation of the second. However, its molecular basis in vivo remains obscure. In this study the authors analyze the participation of two factors in angiogenesis of HCC- human macrophage metalloelastase (HME), a matrix metalloproteinase responsible for the generation of angiostatin, a potent angiogenesis inhibitor, and vascular endothelial growth factor (VEGF), the most potent endogenous angiogenic factor. METHODS: Tumorous and contiguous nontumorous tissues from 25 patients with HCC who underwent curative partial hepatectomy were subjected to Northern blot analysis to detect HME and VEGF messenger RNA (mRNA) expression. Western blot analysis was used to detected angiostatin. Tumor vascularity was evaluated using hepatic angiography. RESULTS: Eleven of the 15 cases expressing the HME gene showed hypovascular tumors, whereas hypervascular tumors were seen in 9 of the 10 HME-negative cases. The median of HME mRNA expression (tumorous/nontumorous ratio) was 6.5 (range 0-264.5) in the hypovascular group and 0 (range 0-3.2) in the hypervascular group. A stepwise logistic analysis revealed that HME and VEGF mRNA expression were two independent variables significantly affecting the vascularity of HCC tumors. CONCLUSION: HME gene expression is significantly associated with hypovascular tumors; moreover, angiogenesis in HCC is not determined by a single factor, but depends on the net balance between HME and VEGF gene expressions.     

New insights in synovial angiogenesis

Angiogenesis is the formation of new capillaries from pre-existing vessels. A number of soluble and cell-bound factors may stimulate neovascularization. The perpetuation of angiogenesis involving numerous soluble and cell surface-bound mediators has been associated with rheumatoid arthritis (RA). These angiogenic mediators, among others, include growth factors, primarily vascular endothelial growth factor (VEGF) and hypoxia-inducible factors (HIFs), as well as pro-inflammatory cytokines, various chemokines, cell adhesion molecules, proteases and others. Among the several potential angiogenesis inhibitors, targeting of VEGF, HIF-1, angiopoietin and the α_Vβ₃ integrin, as well as some endogenous or synthetic compounds including angiostatin, endostatin, paclitaxel, fumagillin analogues, 2-methoxyestradiol and thalidomide seems to be promising for the management of synovial inflammation and angiogenesis. A complete review of antiangiogenic drugs used in animal models of arthritis or human RA is available in a table.     

Angiogenic factors in the central nervous system

The past decade has seen considerable advances in the understanding of angiogenesis. Blood vessel development and growth in the central nervous system are tightly controlled processes that are regulated by angiogenic factors. Angiogenic factors have been implicated in the pathogenesis of a wide variety of disorders, including primary and metastatic brain tumors, aneurysms, arteriovenous malformations, and cavernous malformations. The potential clinical applications of angiogenesis research include inhibition of angiogenesis to control brain tumors and therapeutic angiogenesis to promote collateral blood vessel formation among patients at risk of ischemia. This article summarizes the processes of blood vessel formation in the brain, examines the angiogenic factors that are prominent in the central nervous system, reviews the clinical use of angiogenesis inhibitors, and identifies areas for future investigation.     

Serum angiogenic activity: diagnostic relevance in renal cell carcinoma

OBJECTIVE: Angiogenesis is essential for tumor growth and progression. However, reported data on angiogenic parameters in patients with renal cell carcinoma are contradictory. The objective of this study was to use serum to compare the systemic angiogenic activity in patients with renal cell carcinoma and to determine if pathologic stage and grade correlated to this angiogenesis parameter. METHODS: Serum of 28 patients with a newly diagnosed renal cell carcinoma, 28 healthy volunteers and 9 patients with bladder carcinoma were used for this study. All sera were tested in a 72-hour endothelial cell proliferation assay. In addition the serum concentrations of the angiogenesis stimulators basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) were determined using standard ELISA assays. RESULTS: The serum of renal cell carcinoma patients showed a median stimulation of human umbilical vein endothelial cells (HUVEC) of 89.79% (range 58.47-147.95%) and serum of healthy volunteers showed a median stimulation of 95.35% (range 74.64-141.77%) (p > 0.05). In contrast serum of patients with bladder carcinoma showed a median stimulation of 140.16% (range 64.82-200.16%) (p = 0.024). No correlations of the serum angiogenic activity and tumor stage or grade have been found in renal cell carcinoma patients. Furthermore, no correlations for serum bFGF and VEGF concentrations have been found. CONCLUSIONS: Serum angiogenic activity of patients with renal cell carcinoma did not differ significantly from healthy controls, while serum of patients with bladder carcinoma showed a significant increase in endothelial cell stimulation. Furthermore, bFGF and VEGF serum concentrations did not correlate to serum angiogenic activity in patients with renal cell carcinoma. Therefore, the determination of systemic angiogenic parameters, in case of renal cell carcinoma, might not lead to adequate data concerning prognosis or therapeutic effects.     

Exogenous pro-angiogenic stimuli cannot prevent physiologic vessel regression

BACKGROUND: In healing wounds, rising levels of vascular endothelial growth factor (VEGF) induce a period of robust angiogenesis. The levels of pro-angiogenic factors in the wound begin to decline just before a period of vascular regression, suggesting that these mediators are necessary to sustain vessel density. The purpose of this study was to determine if the maintenance of pro-angiogenic stimuli in the wound would prevent physiological vessel regression. MATERIALS AND METHODS: A standard subcutaneous sponge wound model was modified by the addition of a mini-osmotic pump, allowing manipulation of the wound milieu by the addition of exogenous growth factors. After initial characterization of this model, exogenous VEGF (10 microg/mL), FGF (10 microg/mL), PDGF (10 microg/mL), or VEGF (10 microg/mL) plus FGF (10 microg/mL) were delivered to wounds and blood vessel density analyzed by immunohistochemistry. RESULTS: VEGF administration resulted in a transient increase in wound vessel density (P < 0.05). None of the pro-angiogenic growth factors (VEGF, FGF, PDGF, VEGF/FGF) were able to prevent vascular regression (P = NS). CONCLUSIONS: These findings suggest that the anti-angiogenic signals that mediate physiological vascular regression in wounds are strongly dominant over pro-angiogenic stimuli during the later phases of wound healing. Clinical manipulation of anti-angiogenic signals in addition to the currently used pro-angiogenic targets may be needed to achieve therapeutic modulation of blood vessel density.