Therapeutic Angiogenesis in Wounds: The Influence of Growth Factors at a Muscle Flap — Ischemic Tissue Interface

Abstract

After having demonstrated that the transfer of a well perfused muscle flap predictably enhances the revascularization of ischemic tissue, further studies revealed the presence of basic fibroblast growth factor (bFGF) at the ischemic/non ischemic interface and a proliferative effect of wound fluid collected from this interface on endothelial cells. The aim of this study was, 1. to further investigate the process of revascularization for presence of other growth factors (VEGF, TGF/ß) and 2. to analyze whether this process can be blocked by the addition of an anti bFGF antibody in vivo and 3. if the introduction of exogenous bFGF to the flap-ischemic tissue interface can additionally increase capillary density.

Hindlimb ischemia was produced in New Zealand White Rabbits by ligation of the right common iliac artery (n = 5, group I). A ischemic-non ischemic interface was created by the additional transposition of an inferiorly based left rectus abdominis muscle flap (n=0.10, group II). For the collection of wound fluid and application of growth factor a percutaneously accessible wound fluid chamber was positioned at the flap-ischemic limb interface. In the first experiment an anti bFGF antibody was added to the interface via the wound fluid chamber (n = 5, group II). Biopsies were taken on POD’s 1, 4 and 7. Blood vessels were detected immunohistochemically (CD 31+). In a second experiment (n = 5, group II) 125 μg of recombinant bFGF was added to the interface via the wound fluid chamber on POD 1. Biopsies were taken on POD 7 and blood vesssel count was performed as described previously. Also on POD 7 biopsies were taken for immunohistochemical detection of growth factors.

After in vivo antibody injection the number of new blood vessels at the ischemic-non ischemic interface was reduced significantly (70.7±6.89 vs. 9.93±5.17, p<0.01). After addition of exogenous bFGF number of new blood vessel formations was significantly increased compared to the group were only a flap was transposed to an ischemic hindlimb (70.7±6.89 vs. 108.4±17.6, p<0.03).

These data demonstrate that bFGF is one of the major components in the wound fluid which are responsible for new blood vessel formation. This endogenous effect can be amplified by the addition of exogenous bFGF. In this study the effect of a surgical technique could be improved by using a recombinant angiogenic protein. A further step would be the use of gene therapy. Chroninc wounds, positioned on the body surface would be easily reachable for this technique. Several growth factors (i.e bFGF, VEGF, PDGF, EGF, TGF) will be available to improve surgical procedures or for new therapies based on molecular biology techniques.