Identification of anti-inflammatory M2-like macrophages in diabetic foot ulcer

In diabetic foot ulcers macrophages play an essential role in the immune system due to their phagocytic capabilities, performing multiple trophic functions that are essential for tissue maintenance and homeostasis. Macrophages present in wounds are not a homogeneous population and can have different phenotypes at different stages of the repair process. While macrophages found in the wound are predominantly derived from circulating monocytes, the skin contains a small number of resident macrophages. Two macrophage phenotypes have been classified so far: classically activated macrophages (M1) and alternatively activated macrophages (M2). The exact contribution of these resident macrophages during the repair process is currently unclear. This study aims to identify M2 macrophages and their angiogenic markers in biopsies of diabetic foot ulcer compared to healthy skin biopsies by immunohistochemistry. Skin biopsy from 10 healthy controls, 10 type 2 diabetes mellitus patients, and 10 diabetic foot ulcer patients were analyzed by immunohistochemistry with dual staining in each of the obtained biopsies, both marked and unmarked cells using monoclonal antibodies against CD68, CD163 and CD31. We found that CD68⁺ cells are increased in DFU compared to T2DM patients. However, when analyzing M2 macrophages using the CD163 marker, no changes were observed in any populations. In contrast, the frequency of double-positive (CD68⁺CD163⁺) cells showed significant differences compared to cells CD68⁺CD163^- in DFU and Healthy skin. Furthermore, the results showed that there were only significant differences in CD68 + /CD31 + cells between healthy skin biopsies and T2DM biopsies. We identified a mayor frequency of M2 like macrophage population, however, the lack of CD31⁺ macrophages changes reflect alterations in the progression of wound healing by angiogenic signaling in diabetic conditions.