Mechanisms involved in the development and healing of diabetic foot ulceration

Abstract

We examined the role of vascular function and inflammation in the development and failure to heal diabetic foot ulcers (DFUs). We followed 104 diabetic patients for a period of 18.4 ± 10.8 months. At the beginning of the study, we evaluated vascular reactivity and serum inflammatory cytokines and growth factors. DFUs developed in 30 (29%) patients. DFU patients had more severe neuropathy, higher white blood cell count, and lower endothelium-dependent and -independent vasodilation in the macrocirculation. Complete ulcer healing was achieved in 16 (53%) patients, whereas 13 (47%) patients did not heal. There were no differences in the above parameters between the two groups, but patients whose ulcers failed to heal had higher tumor necrosis factor-α, monocyte chemoattractant protein-1, matrix metallopeptidase 9 (MMP-9), and fibroblast growth factor 2 serum levels when compared with those who healed. Skin biopsy analysis showed that compared with control subjects, diabetic patients had increased immune cell infiltration, expression of MMP-9, and protein tyrosine phosphatase-1B (PTP1B), which negatively regulates the signaling of insulin, leptin, and growth factors. We conclude that increased inflammation, expression of MMP-9, PTP1B, and aberrant growth factor levels are the main factors associated with failure to heal DFUs. Targeting these factors may prove helpful in the management of DFUs.

FIG. 1.

Cumulative incidence of DFUs.

FIG. 2.

Differences in serum TNFα, MCP-1, MMP-9, and FGF-2 among diabetic patients who did not develop DFUs, those who developed foot ulceration and completely healed over a 12-week period (Healers), and those who developed foot ulceration and failed to heal over the same time period (Nonhealers).

FIG. 3.

Forearm-skin biopsy immunohistochemistry analysis (frozen sections, ×100 magnification). A: Hematoxylin and eosin staining in a skin biopsy from a diabetic patient showing round cell inflammatory reaction around blood vessels (black arrows), round inflammatory cells in dermis far from vessels (red arrow), and fibrocytes/fibroblast (green arrows). B: Hematoxylin and eosin staining in a healthy control subject shows superficial blood vessels without perivascular round cell infiltration (black arrows). In the dermis, there are normal collagen bundles, without excess numbers of fibrocytes/fibroblasts or round single cells. C: CD45RO staining in a diabetic patient showing numerous positive lymphoid cells (round cells) around blood vessels (black arrows). D: CD45RO staining in a healthy subject showing a few positive lymphoid cells (round cells) around blood vessels (black arrows). E: MMP-9 staining in a diabetic patient showing intense expression by stromal cells (green arrows). In addition, the antibody was expressed by endothelial cells (black arrows) and reveals the basement membrane of blood vessels (red arrows). F: MMP-9 staining in a healthy control subject. There is faint expression by stromal cells (green arrows) and limited expression by endothelial cells (black arrows). G: PTP1B staining in a diabetic patient showing cytoplasmic, membranous, or paranuclear dot-like staining pattern. PTP1B is strongly expressed by endothelial cells (black arrows), inflammatory cells (red arrow), epidermal basal cells (brown arrow), and dermis cells, mainly fibroblast (blue arrow). H: PTP1B staining in a healthy control subject showing a faint stain pattern in fibrocytes/fibroblasts (black arrows) and endothelial cells (green arrow). (A high-quality digital representation of this figure is available in the online issue.)