Tibial cortex transverse transport accelerates diabetic wound healing via systemic mobilization of non-classical monocytes

Abstract

Aims: To clarify the immunomodulatory mechanisms by which tibial cortex transverse transport (TTT) accelerates wound healing in a type 2 diabetic rat model, with particular focus on the dynamics of subsets of monocytes and macrophages. Methods: A total of 186 male Sprague-Dawley rats were induced as diabetic via a high-fat diet and streptozotocin. A full-thickness skin defect was created on the dorsum of the foot immediately following standard TTT surgery. Wound closure was monitored photographically. At defined timepoints (days 3 to 21), wound tissues underwent histological and immunofluorescence staining (haematoxylin and eosin, Masson's trichrome, picrosirius red, CD68/iNOS/mannose) to assess re-epithelialization, collagen organization, and M1/M2 macrophage populations. Flow cytometry of bone marrow and peripheral blood (CD43 and CD172a markers) quantified classical and non-classical monocyte subsets. Monocyte/macrophage involvement was probed by depleting these cells with clodronate liposomes versus phosphate-buffered saline liposomes. Results: TTT-treated rats achieved complete wound closure by day 21, markedly faster than fixator or sham controls. Histology revealed enhanced re-epithelialization, a thicker epidermis, well-organized type III collagen, and normalized collagen fibre directionality. Immunofluorescence demonstrated a rapid decline in proinflammatory M1 and an increase in reparative M2 macrophages from day 5 onward. Flow cytometry showed a pronounced surge of non-classical monocytes in bone marrow on day 3, followed by elevated circulating levels on days 3 to 6. Monocyte/macrophage depletion markedly delayed healing and disrupted collagen deposition. Conclusion: TTT is associated with accelerated diabetic wound repair, accompanied by preferential mobilization of non-classical monocytes and increased M2 macrophage polarization at the wound site. These findings are consistent with a mechanically induced immunomodulatory process that may contribute to improved healing outcomes.