mimecan and cardiac extracellular matrix integrity

Mimecan and cardiac extracellular matrix integrityLucas Van Aelst, MD

Department of Internal Medicine, University Hospitals Leuven, Leuven, BelgiumVIB-Vesalius Research Center, KULeuven, Leuven, Belgium

What is mimecan?

• Synonym: Osteoglycin (OGN)

• Part of the Small Leucin-Rich ProteoGlycans (SLRP)Other members: biglycan, decorin, fibromodulin, lumican

Phylogenetic analysis and chromosomal organization of

various human SLRP classes.

Schaefer, Iozzo J Biol Chem 2008;283:21305

Small Leucin-Rich Proteoglycans

Multiple signaling pathways evoked by SLRPs

Schaefer, Iozzo J Biol Chem 2008;283:21305

Iozzo J Biol Chem 1999;274:18843

Important for regulation of matrix structure, cell cycle and growth actions

Matricellular proteinsModulate cell-matrix interactions and cell function, without participating

in structural scaffold of the extracellular matrix.

Members:

CCN family members (CCN1-6),Osteonectin (SPARC),Osteopontin (OPN),Tenascins (TN-C, TN-X),Thrombospondins (TSP-1, TSP-2)

Prenatal Growth Adult life Pathology

BIRTH

Tissue repair,Tumour growth

Time

Exp

ress

ion

leve

l

Known non-cardiac functions of mimecan

• Studied in: 1990: Bone formation (Bentz et al., J Biol Chem 265:5024),1997: Atherosclerosis (Shanahan et al., Arterioscler Thromb Vasc Biol 17:2437),1998: Eye & corneal transparency (Liu et al., J Biol Chem 273:22584),2005: Pituitary tumours (Hu et al., J Clin Endocrin Metab 90;6657), 2008: Cochlea & auditory phenotype (Williamson et al., Hear Res 237:57),2008: Metastasis (Cui et al., Acta Biochim Biophys Sin 40:349), 2009: Arteriogenesis (Kampmann et al., Mol Cell Biochem 322:15),2009: Differentiation SCLC(-)/NSCLC(+) (Zhang et al., Oncol Rep 22:1057), 2010: Metabolic syndrome (Pravenec. Methods Mol Biol 597:415),2010: (Pre)term labour (Romero et al., J Matern Fetal Neonatal Med 23:261).

Osteoglycin protein expression in human heart disease

CAD: Isolated coronary artery disease;AS: Concentric hypertrophy secondary to aortic stenosis;HF: Ischemic heart failure and eccentric hypertrophy;HTN: Hypertensive heart disease

Petretto et al., Nat Genet 2008;40(5):546

Does mimecan regulate the integrity of the cardiac extracellular matrix

after myocardial infarction?

0

5

10

15

20

25

30

Sham 3d post-MI 7d post-MI 14d post-MI

• mRNA: Myocardial infarction in mice, sacrificed after 3d, 7d, 14d

p < 0,05

p < 0,05

p = 0,05

Re

lati

ve e

xpre

ssio

n le

vel (

A.U

)

p = NS

Increased expression of mimecan in infarcted area

Van Aelst, unpublished

p < 0,05

0

0,5

1

1,5

2

2,5

3

3,5

Sham 3d post-MI 14d post-MI

Protein:

• Infarcted Area • Remote Area

Increased expression of mimecan in infarcted area

PreOGN

OGNGAPDH

p = NS

p < 0,05

p < 0,05

Re

lati

ve e

xpre

ssio

n le

vel (

A.U

)


Infarcted AreaRemote Area

R

I

S

BB

Increased mortality in the absence of mimecan

Myocardial infarction, mimecan-KO vs. WT mice, 14 days

Similar infarct size in WT vs. KO

Surv

ival

Days after myocardial infarction

Male WT (n = 7)

Female WT (n = 14)

Female KO (n = 8)

Male KO (n = 13)

0

10

20

30

40

50

WT KO

Infa

rct

Size

(%

)


*

* p < 0,05

Cardiac rupture and dilatation in the absence of mimecan in male mice

Mimecan WT, MI, 3d Mimecan KO, MI, 3d


No difference in diastolic dimension nor cardiac function 14d after MI in WT vs KO mice

0

1

2

3

4

5

6

7

WT KO WT KO

LVID

d -

len

gth

(m

m)

0

5

10

15

20

25

30

35

WT KO WT KO

Frac

tio

nal

sh

ort

en

ing

(%)


WT: n = 14KO: n = 8

Baseline 14d after MI Baseline 14d after MI

No significant differences in inflammatory and basic structural histological analyses between WT and KO animals

0

250

500

750

WT KO

CD

45

co

un

t/m

m² WT, 14d KO, 14d

Infarct Thickness (µm) 316 ± 17 281 ± 18

Res. Necrotic Area (%) 4,9 ± 0,5 4,0 ± 0,9

Mac3 count/mm² 131 ± 25 141 ± 35

CD31 count/mm² 151 ± 14 177 ± 20

CD45, WT CD45, KO


No obvious difference in total collagen content in the infarcted area between WT and KO mice

0

10

20

30

40

50

60

WT KO

Co

llage

n D

ep

osi

tio

n (

%)

WT

KO


Impaired collagen cross-linking in the infarct in the absence of mimecan

% Thick/thin collagen fibers:

33 ± 3.4% Thick/thin collagen fibers:

18 ± 4.3* *P<0.01

MIMECAN WILD TYPE MIMECAN KNOCKOUT


Mimecan treatment prevents cardiac dilatation and dysfunction

0

10

20

30

40

RR5 - no MMI

OGN - no MMI

RR5 -MMI

OGN -MMI

Eje

ctio

n F

ract

ion

(%

)

0

1

2

3

4

5

6

7

RR5 - no MMI

OGN - no MMI

RR5 - MMIOGN -MMI

LVID

d (

mm

)

I.V. injection of 1.109 AdV Mimecan, 7 d before MI in WT mice

high mimecan plasma/cardiac levels

p < 0,05 p < 0,05

RR5Sham

RR5Sham

OGNSham

OGNSham

RR5MI

RR5MI

OGNMI

OGNMI

Vector:Group:

Vector:Group:

Van Aelst, unpublishedn = 5 n = 5 n = 10 n = 10

Conclusion:• Matricellular proteins modulate cell-matrix interactions and cell

function, without participating in the structural scaffold of theextracellular matrix (ECM).

• SLRPs, a recently described class of collagen-associated matrixproteins, have a role in collagen fibrillogenesis and a direct andindirect effect on cell growth. As such, they can be classified asmatricellular proteins.

• Mimecan KO male mice die between 3d and 10d after MI (rupture).

• In mimecan KO female mice, there is no significant difference inmortality and cardiac function as compared to WT female mice;there is a difference in collagen quality between mimrcan WT andKO female animals.

• Adenoviral overexpression of mimecan improves cardiac functionafter MI.

• Further in vitro studies are needed to establish the role of mimecanin cardiac ECM integrity after myocardial infarction.

Katholieke Universiteit LeuvenP. CaraiP. CarmelietJ. d’HoogeM. Swinnen*D. Vanhoutte*P. Veulemans

Imperial College LondonL. ColmanS. Cook

Maastricht UniversityS. HeymansS. Jochems*A. PapageorgiouM. Schellings*B. SchroenR. Van LeeuwenW. Verhesen

Acknowledgements:

Funding and Grants:

mimecan and cardiac extracellular matrix integrity

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