Background: Complement C3 increases inflammatory cell migration in wounds. Increasing local amounts of C3 in wounds may augment fibroblast and subsequent collagen deposition and accelerated wound healing. Methods: We examined the effects of complement C3 on the paired rat surgical skin incision model. Each rat served as its own control where topical collagen was applied to one incision and C3 in collagen vehicle was applied to the other incision. To assess for a systemic effect, a control group of rats (one side receiving collagen alone and the other side saline) was compared to the rats receiving the C3. The study was blinded and the sidedness of C3 application was randomized with computer software. Rats were sacrificed on day 3 (n=6), 7 (n=6), and 28 (n=5) after wounding. Tissue harvested from each time point was examined for maximal breaking strength, biochemical analysis, and sectioned for histological examination. A P<0.05 was considered statistically significant. Results: There was a statistically significant 75% increase in maximum wound strength with the topical application of 100nM of C3 as early as day 3 (850 grams) when compared to the control rats (490 grams) Figure 1. No significant differences were seen with 10 nM of C3 at all time points. Histological correlation was seen with an increased inflammatory cell and fibroblast infiltration in treated wounds as compared to control rats at day 3. Western Blot analysis demonstrated increased collagen I and fibronectin content in treated wounds (Figure 2) indication greater fibroblast stimulation. Conclusions: Topical application of Complement C3 in a collagen formulation to skin wounds significantly increases wound healing as early as 3 days after wounding in treated rats. The accelerated wound healing with C3 is likely a result of a local augmentation of both the inflammatory and the proliferative phases of wound healing by causing an increase in vascular permeability and inflammatory cell recruitment and the subsequent early fibroblast migration and collagen deposition in wounds.
Figure 1. Effects of C3 concentrations in collagen formulation on wound strength. A comparison of the effects on maximal wound breaking strength of different concentrations of C3 in collagen treatment is made with those treated with collagen alone in the sham rats.
Figure 2. Western blot analysis of the effects of C3 and collagen on wound healing at day three. Biochemical analysis reveals significant increases in fibronectin (upper bands seen at 220kDa) and collagen I (middle bands seen at 140 kDa) in C3 treated wounds as compared to control wounds as early as Day 3 post-wounding. Actin was used as a loading control (lower bands).