Bacteriophage Cocktail in Hydrogel Dressing Modulates Macrophage Responses and Induces Skin Cell Migration

Background: Bacteriophage mixtures have been explored as biomaterials to promote tissue repair. In this study, we tested the hypothesis that incorporating a phage mixture into a wound dressing could modulate immune cell responses and skin cell migration within the wound environment.

Methods: Phage strains specific to three common Bacterial pathogens-Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa-were embedded in an alginate hydrogel (E-Alg) or grafted onto its surface (S-Alg). The viability of the phages released from the samples were tested. 3T3 fibroblasts in a transwell system were co-cultured with Raw 264.7 macrophages seeded on the dressing samples containing the phage mixture. The cytokine release and fibroblast migration through the transwell membrane were measured.

Results: The phages remained lytic to their hosts after incorporation in the dressing samples (p < 0.001). Macrophages internalized similar numbers of phages, regardless of whether they were stimulated with lipopolysaccharide (LPS) or not (p > 0.05). In the presence of the phage mixture, the resting macrophage produced significantly more nitric oxide (NO), interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α) (p < 0.001). In contrast, the phage mixture significantly reduced the production of these inflammatory mediators in LPS-stimulated macrophages (p < 0.001). The numbers of fibroblast migrating through the membrane toward the macrophages positively correlated with the concentrations of TNF-α and IL-10 released by the macrophages.

Conclusion: A nonhealing wound-common in diabetic patients-is often a result of weakened immune responses. A phage-releasing dressing may not only alleviate Bacterial infection but also attract and stimulate immune responses that promote skin repair.