Hydrocolloid dressing improves wound healing by increasing M2 macrophage polarization in mice with diabetes

Abstract

Impaired wound healing is one of the most common complications of diabetes, and is known to be caused by multiple complicated factors. For instance, impaired angiogenesis, neuropathy, and hyperglycemia all function to delay subsequent wound closure. Alternatively, moist wound healing, which provides an appropriate environment for wounds, was reported to permit rapid healing by managing wound exudate. Accordingly, wound dressing materials that facilitate moist healing have been developed. The present study sought to clarify the effects of wound dressing material for moist healing of diabetic wounds, in terms of the dynamics of angiogenic factors and macrophages, using a mouse model of naturally occurring diabetes. Wounds with full-thickness skin defects were inflicted on the backs of mice and covered with dressing materials of hydrogel or gauze (control), which were retained for 3, 5, 7, 10, or 14 days following wound generation. During this time, the localization of neutrophils, fibroblasts and macrophages as well as the expression of vascular endothelial growth factor (VEGF) in the wounds and surrounding areas was observed each day. Healing clearly occurred in the hydrogel group with an increase in neutrophils and the angiogenic factor, VEGF. Moreover, the use of hydrogel resulted in a rapid rise in M1 macrophages, which appeared in the early stage of the injury, as well as rapid subsequent appearance of M2 macrophages. Thus, herein, we demonstrate that the formation of a moist environment via wound dressing material effectively improves diabetic wound healing.

Keywords: M2 macrophage; diabetic mice; hydrocolloid dressing; wound healing.

Fig. 1

Representative images of full-thickness skin defects in db/db and control mice, at 0 and 14 days post-surgery. upper: hydrogel, bellow: gauze.

Fig. 2

Transmitted light images of HE stained sections of the defects in db/db and control mice, treated with hydrogel or gauze at 3, 7, and 14 days post-surgery (Scale bar = 500um). * indicates the area of full-thickness skin defects, arrow is indicating the presence of scars. From day 3 to 14 defective skin was reconstituted.

Fig. 3

Immunohistochemical staining for neutrophils, VEGF, collagen I and collagen III in hydrogel and gauze groups at 3, 5, 7, 14 and 21 days post-surgery (Scale bar = 200um, ND: no data). Inset: higher magnification image of the square area showing neutrophil-positive cells (arrowhead). Arrows indicate the boundary between defects and normal skin. Numerous immuno-positive cells were observed near the boundary area.

Fig. 4

Semi-quantification analysis of anti-neutrophil antibody classified into ± to +++; ±: positivity ≤ 10%, +: 10% ≤ positivity <5 0%, ++: 50% ≤ positivity < 80%, +++: positivity ≥ 80%. Semi-quantification analysis of anti-VEGF antibody, anti-collage I antibody, and anti-collagen III antibody, classified into ± to +++; ±: positivity ≤ 10%, +: 10% ≤ positivity < 50%, ++: 50% ≤ positivity < 80%, +++: positivity ≥ 80%. Neutrophil and VEGF levels were evaluated on days 3, 5, 7, and 14 post-surgery. Collagen I and collagen III were evaluated on days 3, 5, 7, 14, and 21 post-surgery.

Fig. 5

Immunohistochemical staining of the boundary area between defective and normal tissue for M1 and M2 at 0.5, 1, 2, 3, and 5 days post-surgery (Scale bar = 100um). No positive cells were in the defective area at 0.5 day.

Fig. 6

Semi-quantification analysis of anti-M1 and M2 antibody classified into – to ++; –: no positivity, ±: positivity < 10%, +: 20% ≤ positivity <50%, ++: positivity ≥ 50%, at 0.5, 1, 2, 3, and 5 days post-surgery.