Science - USA (2020-04-10)

By contrast,HampDCD11cmice exhibited sig-
nificantly reduced body weight after removal
of DSS, abnormal colon tissue architecture, and
shortened colons relative to controls (Fig. 3, B
to D).Zbtb46Cre-mediated deletion of hepci-
din in cDCs resulted in a similar impairment
of tissue repair relative to controls (fig. S7). Thus,
cDC-derived hepcidin is essential for mucosal
healing.
We next profiled the colonic expression of fer-
roportin (Slc40a1) and observed high expression
in epithelium, neutrophils, and macrophages
(Fig. 3E). To determine whether these are the
targets of hepcidin that facilitate mucosal heal-
ing, we used mice in which a hepcidin-resistant
ferroportin variant,Slc40a1C326Y, is expressed
from the endogenous locus after Cre-mediated
recombination (fig. S8A) ( 16 ). The expression
ofSlc40a1C326Yin DCs or intestinal epithelial
cells had no impact on mucosal healing (fig. S8,
B to E). By contrast,Slc40a1C326Yexpression in
macrophages and neutrophils via LysMCre
resulted in significantly reduced body weight,
abnormal colonic tissue architecture, and short-
ened colons relative to controls and after re-
movalofDSS(Fig.3,FtoH).Consistentwith
posttranslational regulation of ferroportin, DC-
derived hepcidin did not have an impact on
Slc40a1orHmox1mRNA levels in macrophages
(fig. S8F). Thus, ferroportin-expressing macro-
phages and/or neutrophils are a critical target
for hepcidin-mediated mucosal healing.
To test whether this intestinal hepcidin-
ferroportin axis regulates local iron distribution
in the gut, we used quantitative mass spectro-
metry imaging. Strikingly, iron levels within
the cecal tissue of DSS-treatedHampDCD11c
mice were decreased relative to controls (Fig.
4A and fig. S9, A and B). Consistent with this,
non-heme iron levels were increased in the
luminal content ofHampDCD11cmice relative
to controls after DSS-induced damage, but
not in naïve mice (Fig. 4B and fig. S9, C and
D). This likely involves conversion of heme-
bound iron from erythrocytes into non–heme-
bound iron via heme oxygenase 1 in phagocytes
( 17 ), which would then efflux to extracellular
space through ferroportin unless regulated by
hepcidin. Iron sequestration is a key compo-
nent of nutritional immunity ( 4 , 18 , 19 ), so we
examined whether cDC-derived hepcidin alters
the microbiota.HampDCD11cmice exhibited a
significant shift in microbiota composition rel-
ative to littermate controls (Fig. 4C). Fecal mi-
crobiota transplantation (FMT) fromHampDCD11c
mice to wild-type germ-free recipients was
sufficient to transfer impaired mucosal healing
relative to controls (fig. S10).Catenibacterium
andBifidobacteriumwere significantly different
genera inHampDCD11cmice relative to controls
(fig. S11A). Notably,Bifidobacteriumspecies sup-
port epithelial barrier function, and dietary iron
supplementation can suppressBifidobacterium
species and exacerbate inflammation ( 20 ). We

found thatBifidobacteriumspecies expanded

with restricted dietary iron, and that oral admin-

istration ofBifidobacteriumspecies increased

expression of intestinal tight junctions in

wild-type mice and enhanced mucosal heal-

ing inHampDCD11cmice (fig. S11, B to E).

Bifidobacteriumonly partially restored normal

mucosal healing, and the pathways by which

DC-derived hepcidin promotes colonization

with this microbe remain unclear. In addition,

HampDCD11cmice also exhibited significantly

increased levels of tissue-infiltrating bacteria

relative to controls after DSS exposure, and

antibiotic treatment eliminated DSS-induced

phenotypes (Fig. 4D and fig. S12). To determine

whether excess extracellular iron impairs heal-

ing inHampDCD11cmice, we administered

deferoxamine (DFO), which sequesters extra-

cellular iron from bacteria by chelation ( 21 ).

DFO treatment in DSS-exposedHampDCD11c

mice was sufficient to completely restore muco-

sal healing (Fig. 4, E and F).

Our results outline a model in which cDCs

produce hepcidin in response to microbiota-

derived signals, and subsequently limit iron

release from intestinal phagocytes to prevent

tissue infiltration by the microbiota and thus

promote mucosal healing (fig. S13). This con-

trasts with liver-derived hepcidin, which acts

as an endocrine hormone, is induced by in-

flammatory cytokines, and has the potential

to protect against systemic infection ( 7 , 22 , 23 ).

It will be important to interrogate whether

DC-derived hepcidin has the potential for a

direct impact on the immune response (al-

though this was not observed in our models)

or on systemic iron homeostasis in other con-

texts. Furthermore, our results indicate that

hepcidin mimetics could be a beneficial ther-

apeutic strategy in the context of FMT or gas-

trointestinal diseases where mucosal healing

is an emerging therapeutic goal.

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ACKNOWLEDGMENTS

We thank members of the Sonnenberg laboratory for

discussions and critical reading of the manuscript, the

Epigenomics Core of Weill Cornell Medicine, and S. Mozumder

and K. Kim for technical assistance.Funding:Research in the

Sonnenberg laboratory is supported by NIH fellowship

F32AI124517 (N.J.B.); Crohn’s and Colitis Foundation fellowship

608975 (L.Z.); and NIH grants R01AI143842, R01AI123368,

R01AI145989, R21CA249274, and U01AI095608, the NIAID

Mucosal Immunology Studies Team (MIST), the Searle

Scholars Program, an American Asthma Foundation Scholar

Award, an Investigators in the Pathogenesis of Infectious

Disease Award from the Burroughs Wellcome Fund, a

Wade F. B. Thompson/Cancer Research Institute (CRI)

CLIP Investigator grant, the Meyer Cancer Center

Collaborative Research Initiative, Linda and Glenn Greenberg,

and JRI (G.F.S.). G.F.S. is a CRI Lloyd J. Old STAR.

Funding support also included the European Research

Council (FP7/2011-2015 #261296); the“Fondation pour la

Recherche Médicale”(DEq. 20160334903); the Laboratory

of Excellence GR-Ex (ANR-11-LABX-0051); a labex

GR-Ex fellowship (J.R.R.M. and S.L.); the French National

Research Agency (ANR-11-IDEX-0005-02); the“Fondation

ARC pour la recherche sur le cancer”(S.Z.); NIH grants

PP30ES023515 and 1U2CES030859 (C.A. and M.A.); NIH

grant R00HL125899 (S.M.C.); NICHD grant R00HD087523

(C.A.); and Science Foundation Ireland grant FRL4862

(S.M.C.). The JRI IBD Live Cell Bank is supported by the JRI,

Jill Roberts Center for IBD, Cure for IBD, the Rosanne

H. Silbermann Foundation, and Weill Cornell Medicine Division

of Pediatric Gastroenterology and Nutrition.Author

contributions:N.J.B. and G.F.S. conceived the project;

N.J.B., L.Z., T.C.F., K.C.F., J.B.M., J.R.R.M., C.R., S.L., and

S.Z. performed experiments and analyzed data; S.V. and

S.L.-L. provided mouse models and expertise; H.S. performed

pathological analyses; T.A. provided tools and expertise;

C.P. provided mouse models and designed and supervised

experiments; N.J.A. and G.G.P. analyzed sequencing data;

C.A. and M.A. performed and analyzed iron imaging; R.E.S.

provided essential advice and guidance; S.M.C. provided

guidance and iron measurements; and N.J.B. and G.F.S. wrote

the manuscript with input from all the authors.Competing

interests:G.F.S. holds stock and is a member of an advisory

board for Celsius Therapeutics Inc. T.A. is an employee of

Amgen Inc. H.S. is a co-founder of Exeliom Biosciences and

has received unrestricted study grants from Danone, Biocodex,

and Enterome; board membership, consultancy, or lecture

fees from Carenity, Abbvie, Astellas, Danone, Ferring, Mayoly

Spindler, MSD, Novartis, Roche, Tillots, Enterome, Maat,

BiomX, Biose, Novartis, and Takeda. The other authors

declare no competing interests.Data and materials

availability:All data necessary to understand and evaluate

the conclusions of this paper are provided in the manuscript

and supplementary materials. Microarray and 16SrRNA

sequencing data are available from the GEO database

with accession numbers GSE143869 and GSE139371. Floxed

mice are available with a material transfer agreement

with INSERM.

SUPPLEMENTARY MATERIALS

science.sciencemag.org/content/368/6487/186/suppl/DC1

Materials and Methods

Figs. S1 to S13

References ( 24 – 30 )

9 July 2018; resubmitted 22 August 2019

Accepted 11 February 2020

10.1126/science.aau6481

SCIENCEsciencemag.org 10 APRIL 2020•VOL 368 ISSUE 6487 189

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