Correction of Defective T-Regulatory Cells From Patients With Crohn's Disease by Ex Vivo Ligation of Retinoic Acid Receptor-α

BACKGROUND & AIMS: Crohn's disease (CD) is characterized by an imbalance of effector and regulatory T cells in the intestinal mucosa. The efficacy of anti-adhesion therapies led us to investigate whether impaired trafficking of T-regulatory (Treg) cells contributes to the pathogenesis of CD. We also investigated whether proper function could be restored to Treg cells by ex vivo expansion in the presence of factors that activate their regulatory activities. METHODS: We measured levels of the integrin alpha 4 beta 7 on Treg cells isolated from peripheral blood or lamina propria of patients with CD and healthy individuals (controls). Treg cells were expanded ex vivo and incubated with rapamycin with or without agonists of the retinoic acid receptor alpha (RARA), and their gene expression profiles were analyzed. We also studied the cells in cytokine challenge, suppression, and flow chamber assays and in SCID mice with human intestinal xenografts. RESULTS: We found that Treg cells from patients with CD express lower levels of the integrin alpha 4 beta 7 than Treg cells from control patients. The pathway that regulates the expression of integrin subunit a is induced by retinoic acid (RA). Treg cells from patients with CD incubated with rapamycin and an agonist of RARA (RAR568) expressed high levels of integrin alpha 4 beta 7, as well as CD62L and FOXP3, compared with cells incubated with rapamycin or rapamycin and all-trans retinoic acid. These Treg cells had increased suppressive activities in assays and migrated under conditions of shear flow; they did not produce inflammatory cytokines, and RAR568 had no effect on cell stability or lineage commitment. Fluorescently labeled Treg cells incubated with RAR568 were significantly more likely to traffic to intestinal xenografts than Treg cells expanded in control medium. CONCLUSIONS: Treg cells from patients with CD express lower levels of the integrin alpha 4 beta 7 than Treg cells from control patients. Incubation of patients' ex vivo expanded Treg cells with rapamycin and an RARA agonist induced expression of alpha 4 beta 7 and had suppressive and migratory activities in culture and in intestinal xenografts in mice. These cells might be developed for treatment of CD.