Modulation of Macrophage Recruitment into Wounds by Monocyte Chemoattractant Protein-1

Previous studies suggest that normal wound repair requires the regulated production of monocyte and macrophage chemoattractants. The current study examines the role of monocyte chemoattractant protein-1 (MCP-1) in coordinating monocyte recruitment into sites of injury. MCP-1 protein was detected in both incisional and excisional murine wounds, with a peak concentration occurring slightly before maximum macrophage infiltration. Compared to wounds treated with control antibody, wounds treated with a neutralizing monoclonal anti-MCP-1 antibody contained significantly fewer macrophages (8.2 +/- 0.9 vs. 14 +/- 1.7 macrophages per high power field, p < 0.05). Conversely, the addition of recombinant MCP-1 to wounds resulted in a substantial increase in the number of macrophages (107% to 124% increase over untreated wounds, p < 0.01). Because macrophages promote wound healing, the effect of recombinant MCP-1 on the wound healing process was examined. Incisional wounds (n = 12) were either left untreated or treated with vehicle alone, 5 ng recombinant MCP-1 in vehicle, or 50 ng recombinant MCP-1 in vehicle. Wound disruption strength was determined on days 7, 14, 21, and 28 for each group. Wounds treated with MCP-1 exhibited a slight increase in wound disruption strength at nearly all time points but this increase did not reach statistical significance. Addition of 100 ng of MCP-1 to excisional wounds did not have any significant effect on wound reepithelialization. Taken together, the results show that MCP-1 is produced within wounds at physiologic concentrations, and is an important positive regulator of macrophage recruitment into sites of injury. Addition of exogenous MCP-1 to wounds of normal mice yields only modest enhancement of the repair process.