Fig. 1: Local delivery of exogenous Tregs promotes healing of injured mouse tissues.

a Critical-size cranial defects, quadriceps volumetric muscle loss defect or full-thickness dorsal skin wounds were performed in wildtype C57BL6/J mice and treated with a fibrin hydrogel only, or hydrogel containing exogenous spleen Tregs. Tissue healing was assessed at different time points for each tissue. b Bone regeneration evaluated by microCT analysis of cranial defects expressed as defect coverage and new bone volume at D28 post-injury (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 of tissue sections 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 Percentage wound closure at D7 and D10 post-injury evaluated by histomorphometric analysis of tissue sections (n = 8 wounds for D7, n = 8 wounds for D10 ‘No Tregs’ and n = 12 wounds for D10 ‘+ Tregs’). 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, 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. Two-tailed unpaired Student’s t-test was used in (b), two-tailed Mann–Whitney U test for non-parametric data was used in (d). Two-way ANOVA with Bonferroni post hoc test was used in (f) for multiple comparisons. P values are indicated; ***P ≤ 0.001. 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).