Beta glucan enhances the wound healing process in zebrafish

β-glucans are natural compounds that interact with the innate immune system. Macrophages play an important role in wound healing process and appear to act as the key regulatory cells for skin repair by removing dead tissues and killing pathogens. Macrophages also produce growth factors that stimulate cells involved in wound healing (production of extracellular matrix). Discovering natural products which may enhance the wound healing process in fish, has numerous health benefits and 1,3-1,6 ß-glucans may reduce the negative effect of stress, inflammatory reactions, and secondary infections. In this study, the effects on wound healing process in zebrafish (Danio rerio) of 1,3-1,6 ß-glucan extracted from yeast cell wall was investigated. Ninety female fish were distributed into 3 groups (3 replicates). Two products were used as source of 1,3-1,6 ß-glucan: MacroGard® and new MacroGard (Biorigin©), MI and MII respectively; fish daily feed intake was estimated in advance (3.88% BW) and both MI and MII included into the feed for reaching the dose of 12.5 mg kg-1 BW. Treatments started 2 weeks before injuring. Afterwards, two circular shape wounds were made using a laser source on the dorsal edge of the abdomen. Wounds were then digitally photographed at 2, 4, 10, 16, 20, 30 days post wound (dpw). Wound area was measured by Image J® software and wound size given as a mean of the two wounds for each fish. The first clear differences of wound sizes (1.882, 1.725 and 1.665 mm2, for Control, MI and MII, respectively) were observed already at 4 dpw and differences were statistically significant between MI and MII compared to Control group (P<0.05); this early effect seems to suggest a rapid influx of immune cells to a wound in particular when "activated" by 1,3-1,6 ß-glucan (Paul and Fend 2009). Again, at 16 dpw groups MI (0.766 mm2) and MII (0.634 mm2) showed significantly (P<0.05) lower wound area than Control (0.994 mm2); at 20 dpw, wound area of MII (0.518 mm2) was significantly (P<0.05) different from Control (0.702 mm2) and MI (0.713 mm2). Analysis of final wound status (at 30 dpw) showed that 67.9% of fish from MII group had completely healed wounds while that was significantly (P<0.05) lower with 23.1% and 41.4% in control and MI groups, respectively suggesting that MII has better wound healing potential than MI. The present study demonstrate that 1,3-1,6 ß-glucan (MacroGard®) have potential to be applied as natural wound healing agent in fish. Particularly interesting seems mainly to be their early effect that may imply a higher protection from possible secondary infections. However, further studies are required to determine the optimal feed inclusion in diets for different fish species as well as to explain the slightly higher wound healing effects observed for MII than MI.