Fig. 7. Local delivery of allogeneic and xenogeneic Tregs promotes tissue healing.

a Skin, bone or muscle injuries were performed in BALB/c mice and treated with a fibrin hydrogel only, or hydrogel containing sorted spleen Tregs from C57BL6/J mice (allogeneic delivery), or hydrogel containing human Tregs isolated from peripheral blood and expanded in vitro (xenogeneic delivery). Tissue healing was assessed at different time points for each tissue. b Cranial regeneration at D28 post-injury evaluated by microCT and expressed as defect coverage and new bone volume (n = 8 defects). c Representative cranial reconstructions. The original defect area is shaded with a dashed red outline. d Muscle regeneration represented by the percentage of fibrotic area and muscle area measured by histomorphometric analysis at D10 post-injury (n = 8 defects). e Representative muscle histology of a transverse section of the rectus femoris stained with Masson’s trichrome at D10 post-injury. Muscle tissue is stained in red, and the fibrotic area is in blue. Scale bar = 1 mm. f Wound closure at D10 post-injury evaluated by histomorphometric analysis (n = 8 wounds). g Representative histology of skin tissue stained with haematoxylin and eosin at D10 post-injury. Black arrows indicate wound edges and red arrows indicate tips of epithelium tongue. The epithelium (if any) is stained in purple as a homogeneous keratinocyte layer on top of the wounds, underneath which the granulation tissue is stained in pink–violet, with dark purple granulocyte nuclei. Scale bar = 1 mm. Data are plotted in box plots showing the median (central line) and IQR (bounds) with whiskers extending to the minimum and maximum values. One-way ANOVA with Bonferroni post hoc test was used in (b, d: right) and a two-sided Kruskal–Wallis with Dunn’s post hoc test was used for non-parametric data in (d: left, f) for multiple comparisons. P values are indicated; ***P ≤ 0.001. (aTregs: allogeneic Tregs; hTregs: human Tregs). a Created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license (https://creativecommons.org/licenses/by-nc-nd/4.0/deed.en).