Expression and Proteolysis of Vascular Endothelial Growth Factor is Increased in Chronic Wounds

Abstract

Degradation of angiogenic mediators might be an underlying cause of chronic wounds. To test this hypothesis, we evaluated the expression and integrity of vascular endothelial growth factor, a potent angiogenic mediator, and its receptors, Flt-1 and KDR, in chronic venous leg ulcerations. Immunohisto- chemical, in situ hybridization, and semiquantitative reverse transcriptase polymerase chain reaction analyses all indicate that expression of vascular endothelial growth factor is elevated in ulcerative tissue, with vascular endothelial growth factor mRNA being especially pronounced in the hyperplastic epithelium of the wound margin. Flt-1 and KDR protein and mRNA were detected in the papillary vessels in close vicinity to the lesional epithelium of chronic wounds. Although increased expression of vascular endothelial growth factor protein was detected in the epidermis, the intensity of this staining was weak compared with the epidermal staining in psoriatic lesions and compared with the strong vascular endothelial growth factor mRNA signal in chronic wounds and psoriasis. To analyze whether this apparent decrease in immunoreactivity could be the result of degradation of vascular endothelial growth factor by proteolytic activities from the wound environment, we examined the stability of recombinant vascular endothelial growth factor in wound fluid from chronic leg ulcers. As demonstrated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, incubation of rVEGF165 with chronic, but not acute, wound fluid resulted in rapid proteolytic degradation of rVEGF165. Protease inhibitor studies indicate that serine proteases, such as plasmin, are involved in this degradation. Together, our data show that, although vascular endothelial growth factor expression is elevated in chronic wounds, increased proteolytic activity in this environment results in its degradation, which may contribute to an impaired wound healing response.

A novel primate model of delayed wound healing in diabetes: dysregulation of connective tissue growth factor

“…In contrast, by using the same animals that were studied in the renal series, in the present work CTGF mRNA was not increased in the diabetic wounds but CTGF protein was dysregulated at the posttranscriptional level. In diabetic wounds involving skin and subcutaneous tissues, growth factors, such as PDGF and VEGF protein, that are normally induced in solid organs in diabetes have been reported to be present in reduced amount in wounds [6,7]. The cause of the difference in growth factor findings across tissues in diabetes is unclear, although it may be due to the prolonged inflammatory and protease state that characterises diabetic wounds [39] compared with the profibrotic environment that predominates in diabetic nephropathy [21].…”

“…These processes are tightly regulated by growth factors such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) and by the matrix-degrading enzymes known as matrix metalloproteinases (MMPs). Compared with normal wound healing processes, wound healing in patients with diabetes results in decreased concentrations of PDGF and VEGF proteins in wound tissue [6,7]; however, the effect of diabetes on CTGF in wounds in skin and granulation tissue has not been studied.…”

Proteolytic Processing Regulates Placental Growth Factor Activities

“…Exudate was harvested and tested for plasmin activity as previously described (23,26). PlGF content in serum samples or wound exudates was determined by ELISA (Quantikine human PlGF immunoassay; R & D Systems).…”

“…Specifically, we and others have demonstrated the susceptibility of VEGF-A165 to proteolytic cleavage by plasmin and metalloproteinases (21)(22)(23)(24)(25). Both proteases generate a protease-resistant core fragment containing the VEGFR binding domain but lacking the carboxyl-terminal domain coding for the HBD and the domain encoded by exon 8.…”

VEGF111 : Dr Jekyll et Mr Hyde ?

“…C'est particulièrement vrai pour les ulcères veineux, l'infarctus du myocarde et l'accident vasculaire cérébral. Dans le premier cas, l'environnement de la plaie est riche en plasmine et en métalloprotéa-ses matricielles et dégrade le VEGF165 [5]. Un VEGF165 muté au site de clivage par la plasmine accroît la stabilité des structures vasculaires durant la cicatrisation des plaies chroniques chez les codé par les exons 1 à 4 et 8a (VEGF111, DQ229900) [4].…”