Expression and mechanism of granulocyte-macrophage colony stimulating factor in acute skin defect of the mice

Abstract

Objective To investigate the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) and its associated mechanism during the wound healing. Methods The animal model with the full-thickness skin injury was used in the study. Fifty male mice were involved in the study and divided randomly into control group (n = 25) and GM-CSF group (n = 25). Each group had five time points (5 mice per time point). All the mice received full-thickness skin defect (1 cm × 1 cm) through the panniculus camosus on the midline of the back near the neck after anesthesia. Recombinant human granulocyte-macrophage colony stimulating factor (RhGM-CSF) gel (10 μg/cm2) were applied in the GM-CSF group and gel matrix without RhGM-CSF applied in the control group. The wound healing time and rate were observed at days 3, 5, 7, 10 and 14 after injury. The wound specimens were collected to detect the histopathological change. The microvessel density of the wound was counted based on the results of CD31 immunohistochemistry. RT-PCR was employed to detect the expression changes of GMCSF, platelet-derived growth factor (PDGF) , vascular endothelial growth factor ( VEGF) and stromal cell derived factor-1 (SDF-1). Results RT-PCR results showed that the gene expression of GM-CSF reached the peak at day 3 after injury (P＜0. 01) and kept the high level at days 3-10 after injury (P＜ 0. 05) , followed by a sharp decrease to a normal level at day 14 after wound. The wound healing time was average (2.4 ±0. 3) days earlier than the control mice after application of rhGM-CSF, with significant increase of the wound healing rate during 7-14 days after injury ( P ＜ 0. 05 ). In the GM-CSF group, the early histology of trauma wound showed a small number of neutrophils, obvious epithelial cell proliferation in the wound margin, marked hyperplasia of the granulation tissue, high cell density with quantity of spindle-shaped and oval-shaped cells and increased number of new blood vessels. The microvessel density was also increased significantly (P ＜ 0. 05) at days 7-14 after injury. The gene expressions of VEGF and SDF-1 were significantly increased at day 7 and day 10 respectively after injury (P＜0.05) and the gene expression of pro-healing factor PDGF was significantly increased in every time point (at days 5, 7 and 10,P＜0.05;at day 14,P＜0.01). Conclusion GM-CSF expresses highly in the early stage after injury and can promote the wound healing, when the mechanism may relate to the up-regulated expressions of pro-angiogenic factors and pro-healing growth factors. Key words: Wound healing; Granulocyte-macrophage colony stimulating factor; Microvessel density; Growth factor; Gene expression