Function of human skin T cells in wound healing in the in vitro experimental setting

Abstract

Currently, the treatment of persistent non-healing wounds is among the most difficult clinical issues. We studied 20 samples of normal human skin, 10 specimens from patients with acute trauma, and 9 samples from the patients with chronic wounds that did not heal within 2 months. Using multicolor flow cytometry, we found that the resident T lymphocytes (CD3++ and CD3++) are able to locally produce biologically active substances, normalize human skin homeostasis, thus promoting the wound healing. The data obtained indicate that the blood contains mainly +T lymphocytes (p 0.001), while the +T cells detected in wounds represent a population similar to skin cells. We found no difference in the ratio of resident T cells in chronic and acute wounds, and healthy epithelium. Accordingly, non-healing of wounds and chronic clinical course may be caused by dysfunction of T cells. CD69 regulates T cell secretion of growth factors, IFN, IL-17 and IL-22. The relative number of CD69-expressing T cells from the patients with acute wounds was significantly increased, if compared with cells from normal epidermis and chronic wounds (10.5%2.3, 7.6%1.24, and 3.0%1.05, respectively. p 0.001). The number of cells with the CD3++CD69+ phenotype did not differ significantly between all three groups under comparison. Dysregulation of T cell-mediated healing in chronic wounds is caused by reduced production of IGF-1 by resident CD3++T lymphocytes (1.7%0.9 (p 0.001), and CD3++ (0.44%0.02, p 0.001) compared to CD3++T cells derived from acute wounds (13.6%5.6) and CD3++ (8.9%3.1). The + and + T cells isolated from non-healing chronic wounds did not respond to mitogenic stimuli, unlike the cells obtained from acute wounds and healthy skin. In vitro analysis of cytokine secretion by the CD69-deficient dermal T cells showed a lower spontaneous secretion of IL-22 (4.56%2.3 and 23.9%1.05 and 10.6%1.24, respectively; p 0.001) and IL-2 (0.9%0.08 and 22.6%2.5 and 3.9%1.0, and respectively; p 0.01). When analyzing the number of resident skin T cells secreting IL-17, we obtained the following differences for healthy skin (1.4%0.08), acute wounds (11.3%3.2) and chronic wounds (31.7%11.8), thus showing a significant intergroup difference (p 0.001). T lymphocytes in chronic wounds exhibit some functional disorders and are not able to produce biologically active substances that promote physiological tissue regeneration. The results suggest a role of resident T cells in human skin in wound healing processes and provide new insights into the pathogenesis of chronic wounds.