Determination of Endogenous Cytokines in Chronic Wounds

Abstract

This study objectively characterized the microenvironment of indolent, chronic wounds by developing a method by which minute quantities of cytokines could be extracted from chronic wounds and separately identified. Recombinant DNA technology and the ability to clone compounds such as cytokines allow new management schemes for the treatment of acute and chronic wounds. Before treatment with an exogenous cytokine is started, it would be helpful to know the endogenous level of that cytokine in the wound. Although various methods of extracting cytokines from acute wounds have been reported, no techniques have existed to reliably measure endogenous levels of cytokines in chronic wounds. Porous, inert hydrophilic dextranomer beads were tested for their ability to absorb or adsorb protein and cytokines in vitro with either albumin or albumin laced with various known amounts of cytokines, and then from chronic human pressure ulcers. The Bradford protein assay was used to determine protein levels. Enzyme-linked immunosorbent assay (ELISA) techniques were used to determine levels of platelet-derived growth factor (PDGF)-AB, basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and transforming growth factor-Beta (TGF-beta) extracted by the beads. Between 88% and 98% of known amounts of albumin could be recovered. Similarly, more than 90% of the laced cytokines could be recovered. In 20 grade III/IV pressure ulcers, although protein concentrations were remarkably similar, endogenous levels of cytokine growth factors varied tremendously. Platelet-derived growth factor-AB ranged from 49 to 867 pg/mL; bFGF from 47 to 697 pg/mL; and EGF from nondetectable to 247.5 pg/mL. TGF-B was not detected in 17 of the 20 pressure ulcers. This new technique appears useful for measuring endogenous levels of cytokines. Levels of cytokines found in these chronic wounds are much lower than those reported from acute wounds. The marked variation found among the 20 wounds may help to explain the differences reported in recent wound healing trials with exogenous cytokines.