162 Alkaline Phosphatase Activity is Related to Acute Inflammation and Collagen Turnover During Acute and Chronic Wound Healing

Abstract

Alkaline phosphatase (ALP) is an ubiquitous enzyme produced by different cell types. Previous reports have demonstrated ALP induction by extracellular matrix, ascorbic acid or IL-6. Using histochemical techniques, we evaluated the ex vivo activity of ALP in incisional and excisional acute wounds, chronic wounds, and keloids in animal and human models. We also compared in situ ALP activity with type I/III collagen levels using histological methods (Herovici technique). Results demonstrated that 1) during the first stage of acute wound healing the increase in ALP activity precedes high levels of type III collagen, meanwhile type I collagen diminishes. When ALP activity disappears, the proportion of type I/III collagen returns to normal. 2) ALP activity is almost null in chronic wounds, which are characterized by thick type I collagen fibers and some type III collagen throughout the tissue. However, when the wound is treated, ALP activity rises to maximum levels together with type III collagen, but type I collagen is absent. 3) In keloids ALP activity is also absent; however when the scar is treated with a proinflammatory cytokine downmodulator (collagen-polyvinylpyrrolidone) endogenous type I collagen diminishes, while type III collagen and ALP activity are increased. Based on the above results we suggest that ALP activity is an acute inflammation marker since the enzyme levels are increased in acute wounds but not in chronic inflammation processes. Nevertheless, when chronic lesions or scars are in the process of healing, the increase in ALP activity is clear. And as a result, we believe that treatments for chronic wounds or scars induce acute inflammation and consequently stimulate wound repair or fibrolysis. In conclusion, ALP activity is an important factor to be considered in acute and chronic wound repair and their healing process. This work was partially supported by Sociedad Mexicana de Investigacion Biomedica A.C.