Classical dendritic cells mediate fibrosis directly via the retinoic acid pathway in severe eye allergy
Sarah D. Ahadome, Rose Mathew, Nancy J. Reyes, Priyatham S. Mettu, Scott W. Cousins, Virginia L. Calder, Daniel R. Saban
Sarah D. Ahadome, Rose Mathew, Nancy J. Reyes, Priyatham S. Mettu, Scott W. Cousins, Virginia L. Calder, Daniel R. Saban
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Research Article Immunology Ophthalmology

Classical dendritic cells mediate fibrosis directly via the retinoic acid pathway in severe eye allergy

Abstract

Fibrosis is a shared end-stage pathway to lung, liver, and heart failure. In the ocular mucosa (conjunctiva), fibrosis leads to blindness in trachoma, pemphigoid, and allergy. The indirect fibrogenic role of DCs via T cell activation and inflammatory cell recruitment is well documented. However, here we demonstrate that DCs can directly induce fibrosis. In the mouse model of allergic eye disease (AED), classical CD11b+ DCs in the ocular mucosa showed increased activity of aldehyde dehydrogenase (ALDH), the enzyme required for retinoic acid synthesis. In vitro, CD11b+ DC–derived ALDH was associated with 9-cis-retinoic acid ligation to retinoid x receptor (RXR), which induced conjunctival fibroblast activation. In vivo, stimulating RXR led to rapid onset of ocular mucosal fibrosis, whereas inhibiting ALDH activity in DCs or selectively depleting DCs markedly reduced fibrosis. Collectively, these data reveal a profibrotic ALDH-dependent pathway by DCs and uncover a role for DC retinoid metabolism.

Authors

Sarah D. Ahadome, Rose Mathew, Nancy J. Reyes, Priyatham S. Mettu, Scott W. Cousins, Virginia L. Calder, Daniel R. Saban

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Figure 5

Local DC depletion protects CD11c-eGFP/DTR mice from developing ocular mucosal fibrosis during allergic inflammation.

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Local DC depletion protects CD11c-eGFP/DTR mice from developing ocular m...
Ipsilateral diphtheria toxin (DTx) instillation was given topically (3.125 ng) on days –1, 3, and 5 of challenge, whereas the contralateral eye received PBS control. (A) Equivalent levels of allergic inflammation in allergic eye disease (AED) is achieved despite unilateral DTx instillation to CD11c-eGFP/DTR mice (black arrows). Clinical scores and enumeration of ocular mucosal eosinophils (Eos) and CD4+ T cells (flow cytometry) compared DTx-treated eyes vs. PBS-treated contralateral eyes on day 7. (B) Deletion efficacy of unilateral DTx instillation. Intravital multiphoton microscopy of DTx-treated eye and vehicle-treated contralateral eyes was carried out in AED mice to verify DC deletion in the DTx-treated eye (SHG, second harmonic generation). Lymph nodes (LNs) were collected for flow cytometry to verify deletion of ipsilateral migratory type-2 classical DCs (cDC2). Data is derived from triplicate data points from n = 5 mice. (C) Unilateral DTx instillation during AED leads to reduced collagen deposition in the ocular mucosa of the treated eye (black arrows). Micrographs represent n = 5 mice. (D) Unilateral DTx instillation restores normal levels of proliferation, contractility, and collagen production of AED conjunctival fibroblasts from the treated eye. Fibroblast data are represented by triplicate data points from 3 separate fibroblast cultures from 3 different mice (error bars represent ±SEM; **P < 0.005, ****P < 0.00005; 1-way ANOVA with Bonferroni correction). Each experiment was carried out at least twice.