The oxytocin-dependent effect of <i>L. reuteri</i> is mediated by CD4+CD45RBloCD25+ Tregs.

(a) Transferring CD4+CD45RBloCD25+ regulatory T (Treg) cells from oxytocin-potent L. reuteri-fed donor mice is sufficient to recapitulate the beneficial effects of probiotic consumption in the closure of cutaneous biopsy defects in Rag2–/– recipient mice. By contrast, Rag2 mice that got these same cells from L. reuteri-fed oxytocin-deficient donors failed to benefit, and instead presented large wounds at 6 days post- wounding. Whereas wounds of recipient mice of CD4+CD45RBloCD25+ cells of wild-type mice had accelerated wound healing, the recipients of oxytocin-deficient Tregs showed histopathological features of delayed wound healing, including significantly (b) delayed re-epithelialization, (c) decreased collagen deposition, (d) increased numbers of neutrophils, (e) and decreased regulatory T-cell in their wound counts. (b) Hematoxylin and Eosin. (c) Masson's Trichrome. (d and e) Immunohistochemistry; Diaminobenzidine chromogen, Hematoxylin counterstain. Scale bars: (b) = 250 µm; (c), (d) and (e) = 50 µm.