RESEARCH ARTICLE
Glycop o ein YKL-40: A po en ial bioma ke o
disease ac i i y in heuma oid a h i is du ing
in ensi e ea men wi h csDMARDs and
in liximab. E idence om he andomised
con olled NEO-RACo ial
Tuija Va
¨a
¨na
¨nen
1
, Ka iina Vuol eenaho
1
*, Hannu Kau iainen
2,3,4,5
, Riina Nieminen
1
,
Timo Mo
¨ o
¨nen
6
, Pekka Hannonen
7
, Ma kku Ko pela
8
, Ma kku J. Kauppi
9,10
, Ka i Laiho
9
,
Oili Kaipiainen-Seppa
¨nen
11
, Rii a Luosuja
¨ i
12
, Tea Uusi alo
13
, Toini Uu ela
14
,
Ma ja a Lei isalo-Repo
12
, Ee a Moilanen
1
, on behal o he NEO-RACo S udy G oup
¶
1The Immunopha macology Resea ch G oup, Facul y o Medicine and Li e Sciences, Uni e si y o Tampe e
and Tampe e Uni e si y Hospi al, Tampe e, Finland, 2Depa men o Gene al P ac ice, Uni e si y o
Helsinki, Helsinki, Finland, 3Uni o P ima y Heal h Ca e, Helsinki Uni e si y Hospi al, Helsinki, Finland,
4Uni o P ima y Heal h Ca e, Kuopio Uni e si y Hospi al, Kuopio, Finland, 5MedCa e L d, A
¨a
¨nekoski,
Finland, 6Depa men o Rheuma ology, Uni e si y o Tu ku and Tu ku Uni e si y Hospi al, Tu ku, Finland,
7Depa men o Medicine, Jy a
¨skyla
¨Cen al Hospi al, Jy a
¨skyla
¨, Finland, 8Depa men o In e nal
Medicine, Cen e o Rheuma ic Diseases, Tampe e Uni e si y Hospi al, Tampe e, Finland, 9Depa men o
Medicine, Pa
¨ija
¨ -Ha
¨me Cen al Hospi al, Lah i, Finland, 10 Facul y o Medicine and Li e Sciences, Uni e si y
o Tampe e, Tampe e, Finland, 11 Depa men o Medicine, Kuopio Uni e si y Hospi al, Kuopio, Finland,
12 Rheuma ology, Uni e si y o Helsinki and Helsinki Uni e si y Hospi al, Helsinki, Finland, 13 Depa men
o Medicine, Ha
¨meenlinna Cen al Hospi al, Ha
¨meenlinna, Finland, 14 Depa men o Medicine, Lapland
Cen al Hospi al, Ro aniemi, Finland
¶ All he au ho s named in he au ho lis a e membe s o he NEO-RACo S udy G oup. O he membe s o he
NEO-RACo S udy G oup a e p o ided in he Acknowledgmen s.
*ka iina. uol eenaho@u a. i
Abs ac
Objec i e
YKL-40, a chi inase-like glycop o ein associa ed wi h in lamma ion and issue emodeling,
is p oduced by join issues and ecognized as a candida e au o-an igen in heuma oid
a h i is (RA). In he p esen s udy, we in es iga ed YKL-40 as a po en ial bioma ke o dis-
ease ac i i y in pa ien s wi h ea ly RA a baseline and du ing in ensi e ea men aiming o
ea ly emission.
Me hods
Nine y-nine pa ien s wi h ea ly DMARD-naï e RA pa icipa ed in he NEO-RACo s udy. Fo
he i s ou weeks, he pa ien s we e ea ed wi h he combina ion o sulphasalazine, me h-
o exa e, hyd oxychlo oquine and low dose p ednisolone (FIN-RACo DMARD combina ion),
and subsequen ly andomized o ecei e placebo o in liximab added on he ea men o
u he 22 weeks. Disease ac i i y was e alua ed using he 28-join disease ac i i y sco e
and plasma YKL-40 concen a ions we e measu ed by immunoassay.
PLOS ONE | h ps://doi.o g/10.1371/jou nal.pone.0183294 Augus 25, 2017 1 / 15
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OPEN ACCESS
Ci a ion: Va¨a¨na¨nen T, Vuol eenaho K, Kau iainen H,
Nieminen R, Mo¨ o¨nen T, Hannonen P, e al. (2017)
Glycop o ein YKL-40: A po en ial bioma ke o
disease ac i i y in heuma oid a h i is du ing
in ensi e ea men wi h csDMARDs and in liximab.
E idence om he andomised con olled NEO-
RACo ial. PLoS ONE 12(8): e0183294. h ps://doi.
o g/10.1371/jou nal.pone.0183294
Edi o : Michael Nu mohamed, VU Uni e si y
Medical Cen e , NETHERLANDS
Recei ed: Oc obe 28, 2016
Accep ed: Augus 2, 2017
Published: Augus 25, 2017
Copy igh : ©2017 Va¨a¨na¨nen e al. This is an open
access a icle dis ibu ed unde he e ms o he
C ea i e Commons A ibu ion License, which
pe mi s un es ic ed use, dis ibu ion, and
ep oduc ion in any medium, p o ided he o iginal
au ho and sou ce a e c edi ed.
Da a A ailabili y S a emen : All ele an da a a e
wi hin he pape and i s Suppo ing In o ma ion
iles.
Funding: This s udy was inancially suppo ed by
he Compe i i e Resea ch Funding o Tampe e
Uni e si y Hospi al (KV and EM), he Helsinki
Uni e si y Cen al Hospi al Resea ch Funds (ML-R)
and Finska La¨ka esa¨llskape (ML-R). A baseline an
un es ic ed g an was p o ided by Sche ing-
Resul s
A he baseline, plasma YKL-40 concen a ion was 57 ±37 (mean ±SD) ng/ml. YKL-40 was
signi ican ly associa ed wi h he disease ac i i y sco e, in e leukin-6 and e y h ocy e sedi-
men a ion a e bo h a he baseline and du ing he 26 weeks’ ea men . The csDMARD
combina ion dec eased YKL-40 le els al eady du ing he i s ou weeks o ea men , and
he e was no u he educ ion when he umou nec osis ac o -αan agonis in liximab was
added on he combina ion ea men .
Conclusions
High YKL-40 le els we e ound o be associa ed wi h disease ac i i y in ea ly DMARD-naï e
RA and du ing in ensi e ea - o- a ge he apy. The p esen esul s sugges YKL-40 as a
use ul bioma ke o disease ac i i y in RA o be used o s ee ea men owa ds emission.
In oduc ion
YKL-40 is an in lamma ion-associa ed glycop o ein wi h a molecula weigh o 40 kDa. I
belongs o he amily o chi inase like p o eins bu lacks he enzyma ic ac i i y o ue chi i-
nases. YKL-40 is known also by names chi inase-3-like p o ein 1 (Chi3-l1), b eas eg ession
p o ein 39 (BRP-39), human ca ilage glycop o ein 39, and chond ex. I is exp essed in a ious
cell ypes and inc eased le els o YKL-40 ha e been linked o in lamma ion, issue emodeling
and cance , bu he exac biological ac i i ies a e ye o be iden i ied [1].
Rheuma oid a h i is (RA) is a ch onic au oimmune disease a ec ing p incipally he join s,
bu he mechanisms ha igge he au oimmune esponses leading e en ually o join des uc-
ion a e no ully known. A ea ly phases o he p ocess, exogenous and au ologous an igens
a e p esen ed o T-cells by an igen p esen ing cells and in e es ingly, YKL-40 is ecognized as
a candida e au oan igen [2–6]. Ci cula ing YKL-40 le els ha e been shown o be highe in RA
pa ien s as compa ed o heal hy con ols [7–13]. Also, he YKL-40 concen a ions in syno ial
luid (SF) a e highe han hose measu ed in plasma indica ing signi ican in a-a icula p o-
duc ion [7,11]. Wi hin RA join s, YKL-40 has been ecognized as a majo sec e o y p o ein o
a icula chond ocy es [14]. Syno ial cells, mac ophages and neu ophils in il a ing in o he
RA syno ium also p oduce YKL-40 [1,14–16], and jus ecen ly, splenic T-cells ha e been
added o he lis o YKL-40 p oducing cells in RA [17].
In he ea men o RA, he cu en ea - o- a ge app oach aims o ea ly emission
o maximally low disease ac i i y. Biological disease modi ying an i- heuma ic d ugs
(bDMARDs), including umou nec osis ac o -α(TNF-α) inhibi o s, a e ecommended o be
commenced wi h con en ional sys emic disease-modi ying an i heuma ic d ugs (csDMARDs)
i he ea men a ge is no eached wi h csDMARDs alone [18]. In RA, assessmen o disease
ac i i y is based on composi e indices, such as he 28-join disease ac i i y sco e (DAS28) [19]
e alua ing he coun o ende and swollen join s, in lamma ion and pa ien ´s assessmen o
he disease ac i i y. We ha e epo ed p e iously based on he cu en NEO-RACo ial [20–
23] excellen sus ained clinical esul s wi h ea - o- a ge app oach in pa ien s wi h ea ly,
DMARD-naï e RA by using he in ensi ied Finnish Rheuma oid A h i is combina ion (FIN-
RACo) ea men . This consis s o a combina ion o h ee csDMARDs (i.e. sulphasalazine,
me ho exa e and hyd oxychlo oquine) and low dose glucoco icoid (GC) ollowing a p ede-
ined p o ocol supplemen ed wi h ac i e ea men o in lamed join s wi h in a-a icula GC
YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
PLOS ONE | h ps://doi.o g/10.1371/jou nal.pone.0183294 Augus 25, 2017 2 / 15
Plough Finland, which was used o he pu chase
o in liximab. Sche ing-Plough Finland also
p o ided suppo o in es iga o mee ings. The
unde s did no ha e any ole in he s udy design,
da a collec ion and analysis, p epa a ion o he
manusc ip , o decision o publish.
Compe ing in e es s: Au ho s ha e epo ed he
ollowing compe ing in e es s: KV has ecei ed
hono a ia om GSK. HK has ecei ed hono a ia
om Abb ie and P ize . TM has ecei ed hono a ia
om Abb ie, Amgen, BMS, Eli Lilly, MSD, No a is,
P ize , and Roche. PH has ecei ed hono a ia om
Abb ie, As aZeneca, BMS, MSD, P ize , P o essio
Finland, and Roche. MK has ecei ed hono a ia o
consul ing ees om Abbo , BMS, Celgene, GSK,
Hospi a, MSD, No a is, P ize , Roche, UCB
Pha ma. MJK has ecei ed hono a ia om Abbo ,
BMS, GSK, MSD, P ize , Roche, UCB Pha ma. OK-
S has ecei ed hono a ia om Abb ie, Medac,
MSD, No a is, P ize , Roche, and UCB Pha ma.
M-LR has ecei ed hono a ia om Abb ie, BMS,
MSD, P ize , Regene on and Roche. EM has
ecei ed hono a ia om GSK, BMS and P ize . No
non- inancial con lic s o in e es exis o any o
he au ho s. A baseline an un es ic ed g an was
p o ided by Sche ing-Plough Finland, which was
used o he pu chase o in liximab. Sche ing-
Plough Finland also p o ided suppo o
in es iga o mee ings. The unde s had no
in ol emen in he s udy design, in he collec ion,
analysis and in e p e a ion o he da a in he w i ing
o he epo , o in he decision o submi he pape
o publica ion. This does no al e ou adhe ence
o PLOS ONE policies on sha ing da a and
ma e ials.
injec ions [24]. A 2 yea s, DAS28 emission was achie ed in 82% o he pa ien s [20]. Adding
in liximab o he FIN-RACo combina ion ea men o he i s 6 mon hs in a andomized,
double-blind and pa allel-g oup manne , induced emission mo e apidly, bu di e ences
be ween he ea men g oups we e no s a is ical signi ican a 2 o 5 yea s ollow-up [20,21].
In he sea ch o no el bioma ke s, we hypo hesized ha YKL-40, an in lamma o y ac o
p oduced mainly by in a-a icula issues, could e lec disease ac i i y and in lamma ion in
RA pa ien s. In he p esen s udy, we es ed his hypo hesis by measu ing he YKL-40 plasma
le els in DMARD-naï e pa ien s a he baseline and du ing in ensi e an i- heuma ic ea men
in he NEO-RACo s udy.
Me hods
S udy design, pa ien s, ou comes and ollow-up
Nine y-nine (99) pa ien s wi h ea ly ac i e RA ul illing he classi ica ion c i e ia posi ioned by
ACR [25] we e ec ui ed in o his in es iga o ini ia ed mul icen e s udy be ween Ma ch 2003
and Ap il 2005. NEO-RACo s udy is a p ospec i e 5 yea ial, wi h ex ension o 10 yea s. Fol-
low-up was comple ed in 2015 a e which seconda y endpoin analyses we e pe o med.
Pa ien s we e ea ed wi h an in ensi ied FIN-RACo combina ion including sulphasalazine (up
o a maximum o 2 g/day), me ho exa e (up o a maximum o 25 mg/week), hyd oxychlo o-
quine (35 mg/kg/week), and p ednisolone (7.5 mg/day) and double blindly andomized o
ecei e in alloca ion a io 1:1 in usions o ei he placebo (sol en wi hou ac i e d ug) o in lix-
imab (3 mg/kg), a weeks 4, 6, 10, 18 and 26. The pa ien s we e s a i ied acco ding o se oposi-
i i y ( heuma oid ac o de ined in a local acc edi ed labo a o y). The andomisa ion was
pe o med cen ally by an ex e nal labo a o y no pa icipa ing in he clinical ial in blocks o
10 pa ien s. As pa o he p o ocol, all in lamed join s we e ac i ely ea ed wi h in a-a icula
injec ions o glucoco icoids. A e 24 mon hs, i he pa ien was in emission, p ednisolone
and DMARDs we e g adually ape ed o wi h a p ede ined p o ocol o in he case o non-
emission medica ion was modi ied acco ding o he judgmen o he ea ing heuma ologis
aiming a s ic emission.
The DAS28 sco e (ESR) was used o e alua e disease ac i i y [19]. The modi ied Sha p- an
de Heijde sco e was used o e alua e adiologic sco e [26]. The pa ien selec ion c i e ia as
well as he ea men p o ocol, ou comes and ollow-up ha e been desc ibed ea lie [20–23].
The s udy was conduc ed acco ding o he Decla a ion o Helsinki. All pa ien s ga e
in o med w i en consen . The s udy p o ocol was app o ed by he e hics commi ee o he
Hospi al Dis ic o Helsinki and Uusimaa (s a emen numbe 676/E5/02, da e Janua y 14,
2002) and egis e ed a Helsinki Uni e si y Cen al Hospi al HUCH S udy Regis e (da e Ap il
29, 2003). The s udy was egis e ed a he Clinical T ials Da abase (h ps://clinical ials.go /
c 2/show/NCT00908089? e m=NCT00908089& ank=1) in 2009, soon a e he e ision o he
Decla a ion o Helsinki in 2008, which p omo ed ial egis a ion in a publicly accessible da a-
base. The au ho s con i m ha all ongoing and ela ed ials o his d ug/in e en ion a e
egis e ed.
Plasma samples and ELISA
Plasma samples we e collec ed a weeks 0, 4, 10, 18, 26 (all ime poin s we e a ailable om 88
pa ien s, 60 emales, Fig 1) and kep a -80˚C un il assayed. The concen a ions o YKL-40 and
ma ix me allop o einase-3 (MMP-3) (R&D Sys ems, Minneapolis, MN, USA), and in e leu-
kin-6 (IL-6) (eBioScience Inc., San Diego, CA, USA) we e measu ed by ELISA ollowing he
ins uc ions o he manu ac u e .
YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
PLOS ONE | h ps://doi.o g/10.1371/jou nal.pone.0183294 Augus 25, 2017 3 / 15
S a is ics
Resul s a e exp essed as medians wi h in e qua ile anges (IQRs) o means wi h s anda d
de ia ions (SDs) o 95% con idence in e als (95% CIs). S a is ical compa isons be ween he
g oups we e ca ied ou by using - es , boo s ap ype es (5000 eplica ions) o chi-squa e
es , when app op ia e. Analysis o epea ed da a was ca ied ou by using gene alizing es ima -
ing equa ions (GEE) wi h he uns uc u ed co ela ion s uc u e. Gene alized es ima ing equa-
ions we e de eloped as an ex ension o he gene al linea model (e.g. OLS eg ession analysis)
o analyze longi udinal and o he co ela ed da a. In longi udinal GEE analyses, DAS28 and i s
componen s we e used as ou come a iables, YKL-40 and ime as co a ia es and he model
was adjus ed wi h age, gende , heuma oid ac o posi i i y and ea men . In he case o iola-
ion o he assump ions (e.g. non-no mali y), a boo s ap- ype es was used (5 000 eplica-
ions). A ea unde he cu e (AUC) was calcula ed wi h he apezoidal me hod o e he ime
Fig 1. CONSORT low diag am o he NEO-RACo s udy.
h ps://doi.o g/10.1371/jou nal.pone.0183294.g001
YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
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poin s om 0 o 26 weeks. A possible non-linea ela ionships be ween YKL40(AUC) and
DAS28(AUC) and IL-6(AUC) was assessed by using eg ession models wi h quad a ic e m.
Co ela ion coe icien s we e calcula ed by he Spea man me hod. The no mali y o he a i-
ables was es ed by using he Shapi o-Wilk W es . STATA so wa e ( e sion 13.1, S a aCo p,
LP, Texas, USA) was used in he s a is ical analysis.
Resul s
A he baseline, YKL-40 concen a ion in he DMARD-naï e RA pa ien s was 57 ±37 ng/ml
(mean ±SD, n = 88) and he e was no di e ences be ween emales and males (55 ±37 ng/ml,
n = 60 s 61 ±38 ng/ml, p = 0.43). Cha ac e is ics o he pa ien s a e shown in Table 1. The le -
els o YKL-40 unde baseline condi ions co ela ed posi i ely wi h he disease ac i i y mea-
su ed as DAS28 sco e ( = 0.41, p<0.001, Fig 2A). When he DAS28 componen s we e
assessed sepa a ely, he baseline YKL-40 co ela ed posi i ely wi h he coun o ende join s
( = 0.28, p = 0.004, Fig 2B) and ESR ( = 0.50, p<0.001, Fig 2C), bu he e was no co ela ion
wi h he coun o swollen join s o pa ien ´s global assessmen o gene al heal h. P oin lamma-
o y cy okine IL-6 as well as MMP-3 showed a posi i e co ela ion wi h YKL-40 a he baseline
( = 0.30, p = 0.004, Fig 2D and = 0.39, p<0.001, Fig 2E, espec i ely).
The pa ien s ecei ed a combina ion o sulphasalazine, me ho exa e, hyd oxychlo oquine
and low dose p ednisolone o he i s ou weeks ollowing he in ensi ied FIN-RACo combi-
na ion ea men s a egy [24]. Subsequen ly, he pa ien s we e andomized o ecei e in lixi-
mab o placebo, which was added on he csDMARD combina ion ea men o he u he 22
weeks.
Table 1. The baseline cha ac e is ics o he pa ien s.
Cha ac e is ic The ini ial andomiza ion g oup P- alue All
FIN-RACo + In liximab (n = 44) FIN-RACo + Placebo (n = 44) (n = 88)
Demog aphic da a a baseline
Female, no (%) 32 (73) 28 (64) 0.41 60 (68)
Age (yea s), mean ±SD yea s 47 ±9 44 ±11 0.22 46 ±10)
Du a ion o symp oms (mon hs), median (IQR) 4 (2, 5) 4 (3, 6) 0.54 4 (2, 6)
Rheuma oid ac o p esen (%) 35 (80) 32 (73) 0.56 67 (76)
Measu es o disease ac i i y a baseline
Swollen join coun , mean ±SD 14 ±5 16 ±8 0.33 15 ±6
Tende join coun , mean ±SD 18 ±9 21 ±11 0.10 20 ±10
E y h ocy e sedimen a ion a e (mm/h), mean ±SD 33 ±20 33 ±23 0.84 33 ±21
Pa ien ’s global assessmen (VAS, mm), mean ±SD 49 ±25 47 ±28 0.71 48 ±26
Pain (VAS, mm), mean ±SD 52 ±28 51 ±28 0.79 52 ±27
Physician’s global assessmen (VAS, mm), mean ±SD 46 ±20 53 ±20 0.12 50 ±20
DAS28, mean ±SD 5.4 ±1.0 5.6 ±1.4 0.66 5.5 ±1.2
Physical unc ion (HAQ), mean ±SD 1.0 ±0.6 0.9 ±0.7 0.47 0.9 ±0.7
Radiog aphy a baseline
E osion sco e*, mean ±SD 2.5 ±7.1 1.9 ±4.4 0.66 2.2 ±5.9
Na owing sco e*, mean ±SD 0.5 ±1.6 0.3 ±0.7 0.48 0.4 ±1.2
To al sco e, mean ±SD 3.0 ±8.3 2.1 ±4.7 0.62 2.6 ±6.7
S a is ical compa ison be ween he g oups was pe o med by - es , boo s ap- ype - es (5000 eplica ions), o chi-squa e es , when app op ia e.
*Radiologic sco e by modi ied Sha p- an de Heijde sco e.
h ps://doi.o g/10.1371/jou nal.pone.0183294. 001
YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
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Du ing he i s ou weeks o ea men wi h he csDMARD combina ion, YKL-40 le els
dec eased signi ican ly (p<0.001, Fig 3). This dec ease in YKL-40 le els showed a posi i e co -
ela ion o he change in IL-6 ( = 0.38, 95% CI: 0.18, 0.54) as well as he change in MMP-3 le -
els ( = 0.42, 95% CI: 0.23, 0.58) om baseline o ou weeks; whe eas no co ela ion o he
change in DAS28 was ound.
Du ing he ollowing 22 weeks o ea men wi h csDMARD ±in liximab, YKL-40 le els
showed a mino u he dec ease (g oups combined: -5.0 ng/ml, 95%CI: -9.6 o -0.5,
p = 0.031). Howe e , he e was no di e ence in YKL-40 le els be ween placebo and in liximab
ea ed g oups o e ime (Fig 3). The esul oge he sugges ha dec ease in YKL-40 le els is
ela ed o he an i heuma ic e ec o DMARDs, no o in liximab ea men pe se.
To assess he associa ions o YKL-40 wi h disease ac i i y o e ime (du ing he 26 weeks o
ea men ), a ea unde cu e (AUC) analysis adjus ed o age, gende and heuma oid ac o
(RF) posi i i y was used. A signi ican co ela ion be ween DAS28 AUC
0-26 weeks
and YKL-40
AUC
0-26 weeks
( = 0.41, p<0.001) was ound as shown in Fig 4A. Simila ly, du ing he 26
Fig 2. YKL-40 was associa ed wi h disease ac i i y, IL-6 and MMP-3 in he DMARD-naï e RA pa ien s. The igu e shows sca e plo s o YKL-40
le els wi h disease ac i i y measu ed as DAS28 (A), ende join coun (B), e y h ocy e sedimen a ion a e (C), IL-6 (D), and MMP-3 (E) a he baseline.
Co ela ion coe icien s we e calcula ed by he Spea man me hod. YKL-40 showed posi i e co ela ion o DAS28, ende join coun , ESR, IL-6 and MMP-
3 a he baseline.
h ps://doi.o g/10.1371/jou nal.pone.0183294.g002
YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
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weeks’ ea men , YKL-40 AUC
0-26 weeks
showed a signi ican posi i e co ela ion o ESR
AUC
0-26 weeks
( = 0.56, p<0.001), PGA AUC
0-26 weeks
( = 0.23, p = 0.035) as well as o IL-6
AUC
0-26 weeks
( = 0.31, p = 0.004, Fig 4B). These esul s we e con i med in longi udinal gene -
alized es ima ing equa ion model (GEE, adjus ed o ea men g oup as well as o age, gende
and heuma oid ac o ) whe e YKL-40 showed a signi ican independen associa ion wi h
Fig 3. YKL-40 le els dec eased du ing he in ensi e an i- heuma ic ea men wi h a combina ion o
csDMARDs. The igu e shows he mean change in plasma YKL-40 le els in 88 pa ien s in he NEO-RACo
-s udy ea ed wi h a combina ion o sulphasalazine, me ho exa e, hyd oxychlo oquine and low dose
p ednisolone o he i s ou weeks, and he ea e andomized o ecei e ei he placebo in usions (Fin-RACo
+ Pla) o in liximab in usions (Fin-RACo + INFL) added on he csDMARD combina ion o ano he 22 weeks.
YKL-40 le els dec eased signi ican ly (p<0.001) du ing he i s ou weeks o ea men wi h csDMARDs;
when in liximab (o placebo) was added o he ea men he e was a mino u he dec ease (g oups
combined, p = 0.031) bu no di e ence be ween placebo and in liximab ea men g oups was ound. The
change is p esen ed as ng/ml, mean ±95% CI, n = 88.
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YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
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Fig 4. YKL-40 was associa ed wi h disease ac i i y and in lamma ion du ing in ensi e ea men wi h
DMARDs. The igu e shows quad a ic ela ionships o YKL-40 wi h he disease ac i i y measu ed as DAS28
(A) and wi h he in lamma o y cy okine IL-6 (B) du ing he 26 weeks o ea men . The pa ien s we e ea ed o
he i s ou weeks wi h a combina ion o sulphasalazine, me ho exa e, hyd oxychlo oquine and low dose
p ednisolone, and he ea e andomized o ecei e ei he placebo in usions o in liximab in usions added o
YKL-40 as a bioma ke o disease ac i i y in heuma oid a h i is
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DAS28, and associa ed mos po en ly wi h ESR and PGA when he indi idual measu es o his
a iable we e analyzed (Table 2).
Discussion
In he p esen s udy, we ound ha high YKL-40 le els we e associa ed wi h mo e se e e
in lamma ion and wi h disease ac i i y in DMARD naï e pa ien s wi h ea ly RA, as well as in
he same pa ien s du ing 26 weeks’ in ensi e an i- heuma ic ea men . YKL-40 is hus p o-
posed as a po en ial bioma ke o disease ac i i y and in lamma ion no only in ea ly ea men
naï e RA, bu also du ing ac i e d ug ea men aiming o emission.
YKL-40 is p esen in RA join s and i s concen a ions in syno ial luid a e highe han
hose in se um indica ing in a-a icula syn hesis o he glycop o ein [7,11]. Possible in a-
a icula cell ypes p oducing YKL-40 a e ib oblas -like syno ial cells, mac ophages, neu o-
phils and chond ocy es [1,11,27]. Hypome hyla ed DNA loci o he YKL-40 gene we e ecen ly
de ec ed in syno ial cells om RA pa ien s and his epigene ic change was p esen ed o lead o
he o e exp ession o he gene [28]. Also, pe iphe al blood de i ed CD16 posi i e mononu-
clea cells wi h a mac ophage pheno ype in il a ing in o he syno ium a e ano he po en ial
cellula sou ce o YKL-40 in RA [15]. In addi ion, lymphocy es may p oduce YKL-40: Recen
s udy by Tanaka e al. using glucose-6-phospa ase isome ase immunized mice as a model o
RA, showed o e exp ession o YKL-40 in splenic egula o y T cells [17].
The cellula e ec s o YKL-40 a e no , howe e , known e y well. I may be ha YKL-40
i sel is no he unc ional e ec o molecule bu a p ecu so . To suppo ha assump ion,
YKL-40 de i ed pep ides ha e been shown o induce T-cell p oli e a ion in RA pa ien s [2].
An igen p esen ing cells (APCs) om RA syno ial luid we e epo ed o p ocess YKL-40 and
p esen he decay pep ides o T-cells [6]. This was associa ed wi h he RA- ela ed HLA-DR4
pheno ype, and especially he pep ide 259–271 was ound o induce T-cell p oli e a ion
[2,6,29]. Also, he immune esponse was shi ed owa ds he p oin lamma o y Th1 ype eac-
ion by YKL-40 in pa ien s wi h RA, bu no in heal hy con ols [5]. Fu he , T-lymphocy es
wi h RA-associa ed HLA-DR4 alleles we e epo ed o p oduce high amoun s o in e e on-γ
and TNF-αwhen e-exposed o YKL-40 de i ed pep ides, while he p oduc ion o hese
cy okines in T-cells wi h HLA-alleles non-associa ed o RA was e y low [29]. Mo eo e ,
he ea men o ano he 22 weeks. Measu emen s we e ca ied ou a weeks 0, 4, 10, 18, and 26 du ing he
ea men and a ea unde he cu e analysis o e ime (AUC
0-26 weeks
) adjus ed o age, gende and RF
posi i i y was used. G ay-shaded a eas ep esen 95% con idence in e als a ound he mean. YKL-40
AUC
0-26 weeks
showed a s a is ically signi ican co ela ion o DAS28 AUC
0-26 weeks
and IL-6 AUC
0-26 weeks
.
h ps://doi.o g/10.1371/jou nal.pone.0183294.g004
Table 2. Gene alized es ima ing equa ions models o he e ec o YKL40, ime and in e ac ion in measu es o disease ac i i y om baseline o 26
weeks.
DAS28 TJC SJC ESR PGA
B (95% CI) p- alue B (95% CI) p- alue B (95% CI) p- alue B (95% CI) p- alue B (95% CI) p- alue
YKL-40 0.03
(0.02 o 0.04)
<0.001 0.08
(0.04 o 0.12)
<0.001 0.07
(0.03 o 0.10)
<0.001 0.32
(0.20 o 0.44)
<0.001 0.29
(0.15 o 0.43)
<0.001
Time -0.10
(-0.12 o -0.08)
<0.001 -0.17
(-0.25 o -0.09)
<0.001 -0.16
(-0.22 o -0.10)
<0.001 -0.31
(-0.52 o -0.10)
0.004 -0.84
(-1.17 o -0.51)
<0.001
TimexYKL-40 0.24 <0.001 0.004 0.017 0.073
Models we e adjus ed using age, gende , heuma oid ac o posi i i y and ea men . DAS28—disease ac i i y sco e in 28 join s, TJC— ende join coun ,
SJC—swollen join coun , ESR—e y h ocy e sedimen a ion a e, PGA—pa ien ´s global assessmen .
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