Cutaneous wound healing promoted by topical administration of heat-killed Lactobacillus plantarum KB131 and possible contribution of CARD9-mediated signaling.

Optimal conditions for wound healing require a smooth transition from the early stage of inflammation to proliferation, and during this time alternatively activated (M2) macrophages play a central role. Recently, heat-killed lactic acid bacteria (LAB), such as Lactobacillus plantarum (L. plantarum) have been reported as possible modulators affecting the immune responses in wound healing. However, how signaling molecules regulate this process after the administration of heat-killed LAB remains unclear. In this study, we examined the effect of heat-killed L. plantarum KB131 (KB131) administration on wound healing and the contribution of CARD9, which is an essential signaling adaptor molecule for NF-kB activation upon triggering through C-type lectin receptors, in the effects of this bacterium. We analyzed wound closure, histological findings, and inflammatory responses. We found that administration of KB131 accelerated wound closure, re-epithelialization, granulation area, CD31-positive vessels, and α-SMA-positive myofibroblast accumulated area, as well as the local infiltration of leukocytes. In particular, M2 macrophages were increased, in parallel with CCL5 synthesis. The acceleration of wound healing responses by KB131 was canceled in CARD9-knockout mice. These results indicate that the topical administration of KB131 accelerates wound healing, accompanying increased M2 macrophages, which suggests that CARD9 may be involved in these responses.

Topical Administration of Heat-Killed Enterococcus faecalis Strain KH2 Promotes Re-Epithelialization and Granulation Tissue Formation during Skin Wound-Healing.

Lactic acid bacteria (LAB) are known to have beneficial effects on immune responses when they are orally administered as bacterial products. Although the beneficial effects of LAB have been reported for the genera Lactobacillus and Lactococcus, little has been uncovered on the effects of the genus Enterococcus on skin wound-healing. In this study, we aimed to clarify the effect of heat-killed Enterococcus faecalis KH2 (heat-killed KH2) strain on the wound-healing process and to evaluate the therapeutic potential in chronic skin wounds. We analyzed percent wound closure, re-epithelialization, and granulation area, and cytokine and growth factor production. We found that heat-killed KH2 contributed to the acceleration of re-epithelialization and the formation of granulation tissue by inducing tumor necrosis factor-α, interleukin-6, basic fibroblast growth factor, transforming growth factor (TGF)-ß1, and vascular endothelial growth factor production. In addition, heat-killed KH2 also improved wound closure, which was accompanied by the increased production of TGF-ß1 in diabetic mice. Topical administration of heat-killed KH2 might have therapeutic potential for the treatment of chronic skin wounds in diabetes mellitus. In the present study, we concluded that heat-killed KH2 promoted skin wound-healing through the formation of granulation tissues and the production of inflammatory cytokines and growth factors.

Contribution of Invariant Natural Killer T Cells to the Clearance of Pseudomonas aeruginosa from Skin Wounds.

Chronic infections are considered one of the most severe problems in skin wounds, and bacteria are present in over 90% of chronic wounds. Pseudomonas aeruginosa is frequently isolated from chronic wounds and is thought to be a cause of delayed wound healing. Invariant natural killer T (iNKT) cells, unique lymphocytes with a potent regulatory ability in various inflammatory responses, accelerate the wound healing process. In the present study, we investigated the contribution of iNKT cells in the host defense against P. aeruginosa inoculation at the wound sites. We analyzed the re-epithelialization, bacterial load, accumulation of leukocytes, and production of cytokines and antimicrobial peptides. In iNKT cell-deficient (Jα18KO) mice, re-epithelialization was significantly decreased, and the number of live colonies was significantly increased, when compared with those in wild-type (WT) mice on day 7. IL-17A, and IL-22 production was significantly lower in Jα18KO mice than in WT mice on day 5. Furthermore, the administration of α-galactosylceramide (α-GalCer), a specific activator of iNKT cells, led to enhanced host protection, as shown by reduced bacterial load, and to increased production of IL-22, IL-23, and S100A9 compared that of with WT mice. These results suggest that iNKT cells promote P. aeruginosa clearance during skin wound healing.