The angiogenesis inhibitor endostatin impairs blood vessel maturation during wound healing

Abstract

Endostatin is a cleavage product of collagen XVIII that strongly inhibits tumor angiogenesis. To determine if endostatin affects other angiogenic processes, we generated full-thickness excisional wounds on the back of mice that were systemically treated with recombinant murine endostatin. No macroscopic abnormalities of the wound healing process were observed. Histological analysis revealed normal wound contraction and re-epithelialization, but a slight reduction in granulation tissue formation and reduced matrix deposition at the wound edge. The blood vessel density in the wounds of endostatin-treated mice was not affected. However, ultrastructural analysis demonstrated severe abnormalities in blood vessel maturation. The wound vessels in the endostatin-treated mice were narrowed or closed with an irregular luminal surface, resulting in a severe reduction in the number of functional vessels and extravasation of erythrocytes. Endostatin treatment did not affect the expression level and localization of collagen XVIII mRNA and protein. Furthermore, the angiogenesis regulators vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 were normally expressed in the wounds of endostatin-treated mice. However, expression of the major wound matrix proteins fibronectin and collagens I and III was significantly reduced. This reduction is likely to explain the reduced density of the wound matrix. Our results demonstrate that endostatin treatment reduces the number of functional blood vessels and the matrix density in the granulation tissue, but does not significantly affect the overall wound healing process.

Structure and Function of Collagen‐Derived Endostatin Inhibitors of Angiogenesis

“…Endostatin treatment did not interfere with vessel density in the granulation tissue, wound contraction, or the final stage of repair. During the peak of angiogenesis, however, endostatin interferes with vessel maturation, as indicated by massive hemorrhages and pathological changes in the ultrastructure of vessel walls (48). These findings are consistent with a higher sensitivity of tumor vessels, which are known to have a chaotic and leaky architecture and also integrate tumor cells into their endothelial lining (3).…”

“…Endostatin inhibition was shown to selectively decrease blood flow and size of tumor vessels and enhances apoptosis of tumor cells (46). Endostatin effects on more physiological forms of angiogenesis have been studied in two different models of cutaneous wound healing (47,48). Endostatin treatment did not interfere with vessel density in the granulation tissue, wound contraction, or the final stage of repair.…”

Regulation of scar formation by vascular endothelial growth factor

“…For example, endostatin treatment during wound healing has been described to alter collagen deposition, 45 and CM101 has been suggested to reduce scarring in Kaposi's sarcoma patients. 46 ZD6474, an inhibitor of VEGFR-2 receptor tyrosine kinase activity, has recently been reported to reduce the degree of fibrosis after wound healing.…”

Signaling pathways involving adenosine A2A and A2B receptors in wound healing and fibrosis

“…Interestingly, A 2A R knockout mice have more disorganized granulation tissue after wounding compared to wild-type mice although the re-epithelialization rate is not impacted [16,24]. Finally, there is evidence that the inhibitor of angiogenesis endostatin modulates dermal collagen deposition and that inhibition of adenosine receptor-mediated angiogenesis alters the composition of scars thus demonstrating that the two key elements of granulation tissue formation are at least partially interdependent [25].…”