Relationship Between Dysbiotic Wound Microbiota and Critical Colonization: Involvement of FOXP3-Positive Cells in Rats.

Introduction: Detection of critical colonization is gaining importance in wound management, but its pathophysiology remains unclear. We previously clarified that a dysbiotic wound microbiota differing from skin commensal microbiota may be involved in critical colonization and that such wounds contain fewer Forkhead box protein P3 (FOXP3)-positive cells in the tissue. However, it is not clear whether FOXP3-positive cells contribute to the development of critical colonization. Here, we examined whether inhibition of FOXP3-positive cell could induce critical colonization when the commensal microbiota was present in the wounds.

Methods: Sprague-Dawley rats were administered FK506 or vehicle to inhibit differentiation into FOXP3-positive cells. Full-thickness wounds were made on the dorsal skin and inoculated with bacterial solution (dysbiosis group) or Luria-Bertani medium (commensal group). A bacterial solution was prepared by anaerobically culturing bacteria from the skin of donor rats on an artificial dermis in Luria-Bertani medium for 72 hours. Tissues were collected on day 4 postwounding for histological evaluation.

Results: After microbiota transplantation, excessive inflammation occurred in the FK506 + commensal group. In contrast, wounds with transplanted dysbiotic microbiota showed the same level of neutrophil infiltration, regardless of FK506 administration. Furthermore, the wound area was larger in the FK506 + commensal group than in the vehicle + commensal group on day 4 postwounding ( P = 0.01). This area was also significantly larger in both the vehicle + dysbiosis ( P = 0.01) and FK506 + dysbiosis groups ( P = 0.03) than in the vehicle + commensal group.

Conclusions: This study has shown that dysbiosis may be at least related to developing critical colonization, and the results suggest that FOXP3-positive cells are involved in this process. Our study may contribute to establishing new interventions that prevent critical colonization by correcting wound microbiota.