Review Article Update on Abdominal Aortic Aneurysm Research: From Clinical to Genetic Studies

15 Pages·2015·2.1 MB·English

Hindawi Publishing Corporation
Scientifica
Volume 2014, Article ID 564734, 14 pages
http://dx.doi.org/10.1155/2014/564734
Review Article
Update on Abdominal Aortic Aneurysm Research:
From Clinical to Genetic Studies
HelenaKuivaniemi,1,2EvanJ.Ryer,2,3JamesR.Elmore,2,3IreneHinterseher,4
DianeT.Smelser,1andGerardTromp1
1TheSigfriedandJanetWeisCenterforResearch,GeisingerHealthSystem,Danville,PA,USA
2DepartmentofSurgery,TempleUniversitySchoolofMedicine,Philadelphia,PA,USA
3DepartmentofVascularandEndovascularSurgery,GeisingerHealthSystem,Danville,PA,USA
4DepartmentofGeneral,Visceral,VascularandThoracicSurgery,Charite´Universita¨tsmedizinBerlin,Charite´CampusMitte,
Berlin,Germany
CorrespondenceshouldbeaddressedtoHelenaKuivaniemi;[email protected]
Received17December2013;Accepted2February2014;Published17April2014
AcademicEditors:D.PaciniandB.Z.Simkhovich
Copyright©2014HelenaKuivaniemietal. This is an open access article distributed under the Creative Commons Attribution
License,whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperly
cited.
Anabdominalaorticaneurysm(AAA)isadilatationoftheabdominalaortawithadiameterofatleast3.0cm.AAAsareoften
asymptomatic and are discovered as incidental findings in imaging studies or when the AAA ruptures leading to a medical
emergency.AAAsaremorecommoninmalesthanfemales,inindividualsofEuropeanancestry,andinthoseover65yearsof
age.Smokingisthemostimportantenvironmentalriskfactor.Inaddition,apositivefamilyhistoryofAAAincreasestheperson’s
riskforAAA.Interestingly,diabeteshasbeenshowntobeaprotectivefactorforAAAinmanylargestudies.HallmarksofAAA
pathogenesisincludeinflammation,vascularsmoothmusclecellapoptosis,extracellularmatrixdegradation,andoxidativestress.
AutoimmunitymayalsoplayaroleinAAAdevelopmentandprogression.InthisOutlookpaper,wesummarizeourrecentstudies
onAAAincludingclinicalstudiesrelatedtosurgicalrepairofAAAandgeneticriskfactorandlarge-scalegeneexpressionstudies.
Weconcludewithadiscussiononourresearchprojectsusinglargedatasetsavailablethroughelectronicmedicalrecordsand
biobanks.
1.Introduction Hallmarks of AAA pathogenesis include inflammation,
vascularsmoothmusclecell(VSMC)apoptosis,extracellular
Anabdominalaorticaneurysm(AAA)isapermanentlocal-
matrix(ECM)degradation,andoxidativestress[2,5,6,10].
izeddilatationoftheabdominalaortawithatransversediam-
InAAApatients,T-cellssecreteproinflammatorycytokines
eter≥3.0cm[1].AAAsareoftenasymptomaticandaredis-
[11]andnaturalkillercellsdisplayincreasedcytotoxicity[12].
coveredasincidentalfindingsinimagingstudies(e.g.,abdo-
AutoimmunitymayalsoplayaroleinAAAdevelopmentand
minal ultrasonography or computerized tomography (CT)
progression[3,13].
examination)orwhentheAAArupturesleadingtoamedical
InthisOutlookpaper,wesummarizeourrecentstudies
emergency.AAAsaremorecommoninmalesthanfemales
(6:1ratio),inindividualsofEuropeanancestryandinthose onAAAstartingwithclinicalobservationsandthenmoving
>65 years of age [2–8]. Smoking is the most important into studies on the genetic risk factors for AAA followed
environmental risk factor for AAA development [2–8]. In by studies on the pathogenesis of AAA, large-scale gene
addition,apositivefamilyhistoryofAAAincreasesaperson’s expressionstudiesandstudiesonanimalmodels.Finally,we
riskforAAA[2–9].Interestingly,diabeteshasbeenshownto discussfutureresearchusinglargedatasetsavailablethrough
beaprotectivefactorforAAAinmanylargestudies[2–8]. electronicmedicalrecords(EMR)andbiobanks.
2 Scientifica
Table1:SAAVEacteligibilityin52studypatientswithrupturedAAAatthetimeofpresentation.
Total Smokinghistory FamilyhistoryofAAA SAAVEacteligible
Variable
𝑛(%) 𝑛 𝑛 𝑛(%)
Age(male)
65–75 10(19.2) 7 0 7(13.5)
<65 7(13.5) 5 0 0
>75 19(36.5) 11 1 1(1.9)
Female 16(30.8) 13 1 1(1.9)
Total (17.3)
AAA:abdominalaorticaneurysm;smokinghistory:patientshadsmoked>100cigarettesintheirlifetime.
Modifiedfrom[21].
2.ClinicalStudiesonAAA havebeeneligibleforthe“WelcometoMedicare”screening
aorticultrasound(Table1).Ofthemalepatientsineligiblefor
2.1.RuptureofAAAIsPreventable. Themainriskofanun- screeningundertheSAAAVEAct,7/36(14%)wereyounger
treatedAAAisprogressiveexpansion,rupture,hemorrhage, than 65 years and 19/36 (37%) were older than 75 years.
and death. AAA prevalence increases with age, and even Only 10/36 (19%) male patients were between the age of 65
thoughtheincidencehasdeclinedinthepasttenyears[14], and75years,sevenofwhichwereeligibleforthescreening
ruptureofAAAisstillasignificantcauseofdeathwith10– ultrasoundsecondarytotobaccouse.Elevenofthe19male
15% of AAAs presenting as ruptured AAAs (rAAA) in the patients older than 75 years had a history of smoking and
emergencyroom.AAAruptureriskincreaseswithincreasing wouldhavequalifiedundermoreinclusiveagecriteria.There
aortic diameter and this catastrophic event is associated were also16/52 (31%)femalesbetween theage of61 and96
with a mortality of 50 to 80% [15–17]. Due to the excessive years who presented with a rAAA. Thirteen (81%) of the
mortality associated with emergent repair, the mainstay of femaleshadasmokinghistory.Unfortunately,AAAscreen-
AAAmanagementisearlydiagnosisandelectiverepairprior ing in female patients is not covered by the SAAAVE
to rupture. In an effort to reduce the number of AAA- Act. Overall, greater than 80% of patients who presented
relateddeaths,theScreeningAbdominalAorticAneurysms to our institution with a rAAA would not be included in
VeryEfficiently(SAAAVE)ActwasapprovedbytheUnited theSAAAVEActscreeningprogram.Fromourinvestigation,
States Congress in January 2007. The SAAAVE Act permits we concluded that routine ambulatory medical evaluations
a single screening aortic ultrasound examination as part of in conjunction with current AAA screening methods are
the“WelcometoMedicare”packageforpatientswithdefined inadequatetodetectAAAsinanat-riskpopulationpriorto
risk factors for AAA. Specifically, males between the age of rupture.
65and75yearswhohavesmokedgreaterthan100cigarettes
in their lifetime or patients of any age or sex with a strong 2.2. Quality of Life for AAA Patients. We have also exam-
family history are eligible for this screening examination ined the long-term quality of life (QOL) in AAA patients
[18]. Despite the introduction of the SAAAVE Act in 2007, under surveillance and after operative treatment [23]. We
screeningforAAAremainsunderutilized[19].Additionally, performedaretrospectiveanalysisof78patientswithsmall
more recent data suggest that the implementation of the aneurysms (diameter 3.0–4.9cm) undergoing surveillance
SAAAVE Act has not had any discernible effect on AAA at University Hospital of Dresden in Germany and com-
rupturerateorAAA-relatedmortality,presumablyduetoits pared them with long-term survivors following operative
severeunderutilization[20]. treatment during the time period of 1995 to 2006. The
WehaveanactiveinterestinAAAscreeningandstudied surgicalgroupincluded26patientsundergoingopenrepair
whether routine medical evaluation in the ambulatory care for the treatment of a rAAA, 47 patients following elective
setting combined with the utilization of the SAAAVE Act, endovascularaneurysmrepair(EVAR),and98patientsfol-
initscurrentform,isaneffectivemethodforscreeningand lowingelectiveopenrepair.Patientswereassessedusingthe
diagnosingpatientsatriskforAAA[21].Totestourhypoth- WHO Quality of Life-BREF (WHOQOL-BREF) and Short
esis, we retrospectively reviewed 149 consecutive patients Form Health Survey (SF-36). The WHOQOL-BREF is an
presenting to our tertiary care center, Geisinger Health internationally standardized QOL questionnaire that exists
System (GHS) [22], with a rAAA. Of these 149 patients, 52 in different languages and is proven to determine reduced
patientshadcompleteEMRdocumentationofanambulatory QOL in chronic diseases and the SF-36 is a well-known
care visit within the 6 months prior to the date of rupture. internationalQOLtest,oftenusedaftersurgicalprocedures.
Twenty-oneoftheruptures(40%)hadaradiographicstudy SF-36 is also available in multiple languages. Surprisingly,
(duplexultrasoundorCTscan)thatdemonstratedanAAA. we found that patients undergoing surveillance for a small
Only12ofthese21(57%)werereferredtoandevaluatedbya AAAhadsignificantlydiminishedphysicalhealth(𝑃=0.04)
vascularsurgeon.Furthermore,underthecurrentSAAAVE scores on the WHOQOL-BREF and significantly decreased
Act criteria, only 9/52 (17%) of the study patients would role-emotional(𝑃 = 0.003)androle-physical(𝑃 = 0.02)on
Scientifica 3
the SF-36 compared to the age- and sex-matched Ger- 1.0
mancontrolsubjects.Incontrast,patientsundergoingelec- 0.9
tiveAAArepairhadsimilarQOLscoresasmatchedGerman
0.8
subjects. It is likely that the lower QOL in AAA patients
0.7
undergoing surveillance can be improved through more
intensiveeducationabouttheirhealthconditionandthelow val 0.6
vi
rsintisuksdmioeasfllwrAuilpAltbAuerpenaeitneiedntehtdsetuoenasdreeleyrgifsotoianuggresseufforofvrettishllewanidlcliesi.emapser.ovFeuQrthOeLr verall sur 00..54
O
0.3
2.3.SurvivalRatesofAAAPatientsafterOperativeTreatment. 0.2
Once AAAs are identified, they can be managed using
0.1
different therapeutic modalities: traditional open surgical
0.0
repair,minimallyinvasiveEVAR,orcontinuedsurveillance.
0 1 2 3 4 5 6 7 8
Treatmentinmostcasesisselectedbasedonaneurysmsize,
aneurysm shape, and the patient’s corresponding medical Years
comorbidities. Traditional open surgical repair involves a rAAA
large incision in the abdomen and replacement of the EVAR
aneurysmwithasyntheticfabricgraft.Analternativetreat- eAAA
ment, first described in 1986, is EVAR [24]. This minimally
Figure1:Survivalanalysisforpatientsafterarupturedabdominal
invasivetechniqueinvolvesinsertionofafabriccoveredstent
aorticaneurysm(rAAA),electiveopenrepair(eAAA),orelective
torelinetheaneurysmalaortaviathefemoralandiliacarter- endovascularrepair(EVAR).Kaplan-Meiercurvesweregenerated
ies.Thefunctionofthestentgraftistoexcludetheweakened with the indicated numbers of patients at risk. Reproduced with
aorticaneurysmwallfromthesystemicbloodpressureand permissionfrom[26].
hencerupture.TheintroductionofEVARhasrevolutionized
thetherapeuticapproachtopatientswithAAA.Furthermore,
the last decade has witnessed a rapid progression in the
techniques and devices engineered to perform endovascu-
electiveAAArepairs.Therelativelong-termsurvivalratein
lar AAA stent grafting in an attempt to decrease graft-
allthreesurgicalgroupswasthesameasthatforthegeneral
relatedcomplicationsandreinterventions.Inourexperience,
German population. Our analysis demonstrated that the
suitable anatomy, device familiarity, and cost are the most
relativelong-termsurvivalafterAAArepair,regardlessofthe
importantfactors regarding selection forEVAR. In general,
modality,isequaltothatofacomparablepopulation-based
many of the current devices used according to instructions
groupafterthefirstpostoperativemonth.Wearehopefulthat
foruseareequivalentregardingpostoperativecomplications,
oureffortswillassistcliniciansindecision-makingandmay
migration,andaneurysm-relatedmortality[25].Inaddition
helpahesitantpatientwhendecidingonmanagementoftheir
to device design, we have an active interest in studying the
AAA.
outcomesfollowingAAArepair[26].Recently,wecompared
the relative survival rates of patients after various operative
treatments for AAA to those of the general population. To 2.4.ComparingtheCostofAAARepair. Inadditiontostudy-
perform this study, we retrospectively reviewed the records ing clinical outcomes, we are also concerned with the cost
ofallpatientswhounderwentopenrepairforrAAA,elective of AAA repair. This is especially important as clinicians
openrepair,andelectiveEVARofAAAsfrom1995to2005 continually balance the use of emerging technology with
at the Vascular Center, Technical University of Dresden, efforts to decrease health care expenditures. Recent studies
Germany.TheUniversityHospitalofDresdenisamongthe have shown that the standard minimally invasive EVAR
higher-volumecentersforAAAinGermany[27].Westudied procedure comes with decreased short term morbidity but
319 patients after operative treatment of AAA, including alsowithincreasedcosts[28–30].Furthermore,EVARcom-
113 (35%) with open rAAA repair, 152 (48%) with elective monlyinvolvesextendingtheaorticrepairpastthecommon
open AAA repair, and 54 (17%) with EVAR. Kaplan-Meier iliac arteries into the external iliac arteries, which adds
survivalcurvesofthethreeoperativelytreatedpatientgroups both complexity and expense. Without thrombosis of the
are shown in Figure1. The rAAA patients showed a sharp excluded internal iliac artery (IIA), retrograde flow can
decreaseinsurvivalduringthefirst6monthsafteroperative lead to continued sac pressurization (i.e., endoleak) and
management (including hospital mortality); 50% were alive aneurysm enlargement. Conventionally, embolization has
after6months,46%werealiveafteroneyear,and36%were beenachievedsafelybyinsertingembolizationcoilsintothe
alive after three years. The elective open AAA repair group proximalIIAtoinducethrombosis.TheAmplatzerVascular
showed an 89% survival rate after one year and 82% after Plug(AGAMedicalCorp,Plymouth,Minnesota),anitinol-
threeyears.TheEVARgrouphadasurvivalrateof96%after based self-expanding cylindrical occlusion device, has been
oneyearand92%afterthreeyears.Thetime-specificrelative showntobeasuitablealternativetocoilembolization.Since
survival rate of the rAAA group reached 1.0 at 16 months bothmodalitieshavebeenshowntobesuccessfultechniques,
followingemergencysurgeryandaftertenmonthsforopen and limited data directly comparing the two treatment
4 Scientifica
70,000 3.1.DNALinkageStudies. DNAlinkageanalysisisanunbi-
P=0.22
60,000 asedgenome-widemethodusedtoidentifysusceptibilityloci
byfollowinginheritancepatternsofthediseaseofinterestin
50,000
a family through the use of genetic markers [35]. Typically,
40,000 P=0.39 linkagebetweenaspecificgeneticmarker,orseveralmarkers,
($) 30,000 andthediseaseofinterestcanbedeterminedusingcomplex
20,000 statisticalanalyses[36].ThemostcommonapproachofDNA
10,000 linkagestudiesistouselargecollectionsofmultigenerational
families. Due to the late-age-at onset of AAA and the fact
5,000 P=0.07
that many patients die of ruptured AAA, it is difficult
2,500 to collect blood samples for DNA isolations from large
0 multigenerational families. DNA linkage studies on AAA
Coil/plug Operating room Hospital have, therefore, used affected relative-pair approach. Using
Charges this approach two genetic loci, containing several plausible
Coiln=22
candidate genes located on chromosomes 4q31 and 19q13,
Plugn=26
werediscoveredforAAA[37–39].
Figure2:Economicanalysisofinternaliliacarteryembolizations.
Coilembolization(COIL)andAmplatzerVascularPlugemboliza- 3.2.AAAGenome-WideAssociationStudies(GWAS). GWAS
tion (PLUG) charges, operating room charges, and total hospital
uses a case-control approach and examines many common
charges for internal iliac artery embolizations performed prior to
geneticvariantsinalargenumberofindividualstoidentifya
endovascularaneurysmrepairforthetimeperiodfrom2004to2010
variantthatisassociatedwithaspecifictrait.GWAStypically
(standardized to 2011 dollars). Reproduced with permission from
focusesonassociationsbetweenSNPs,variationsinasingle
[31].
nucleotidewithintheDNAsequence,andtheirinfluenceon
healthanddisease.Ifsufficientlylargecase-controlgroupsare
used,GWASisanefficientmethodtoidentifyreproducible
modalitiesareavailable,wesoughttocomparethetwotech- risk alleles predisposing to the disease of interest [9, 40].
niques[31].Todoso,weperformedaretrospectivereviewof GWAShasprovenapowerfulinstrumenttoidentifygenetic
53consecutivepatients(51malesand2females)treatedwith risk factors associated with the presence of cardiovascular
percutaneousIIAembolizationspriortoEVARfrom2004to disease and has been carried out by international consortia
2010.Twenty-nineweretreatedwithplatinumembolization toidentifysusceptibilitylociforAAA[28,41–44].
coils (Cook Medical Inc., Bloomington, Indiana) and 28 The five chromosomal regions in the human genome
weretreatedwithAmplatzerVascularPlugdevices.Patients with the strongest supporting evidence of contribution to
undergoing Plug embolization demonstrated significantly the genetic risk for AAA are listed in Table2 and include
shorterproceduretimes(𝑃 = 0.008);however,periprocedu- (1) CDKN2BAS gene (located on chromosome 9p21), also
ral success or morbidity did not differ between the groups. knownasANRIL,whichencodesanantisenseRNAthatreg-
Furthermore, there was no significant difference in charges ulates expression of the cyclin-dependent kinase inhibitors
for the embolization material, operating room, or overall CDKN2A and CDKN2B [44]; (2) DAB2 interacting protein
hospital charges (Figure2). These findings supported our (DAB2IP; located on chromosome 9q33), which encodes
initialhypothesisthatthesetwotreatmentmodalities,despite an inhibitor of cell growth and survival [43]; (3) low den-
differingexpertopinions,areequalintermsofefficacyand sity lipoprotein receptor-related protein 1 (LRP1; located on
cost. chromosome12q13.3),aplasmamembranereceptorinvolved
in vascular smooth muscle and macrophage endocytosis
[45], (4) low density lipoprotein receptor (LRPR; located
3.TheDiscoveryofNewGeneticRisk
onchromosome19p13.2)[41],and(5)contactin-3(CNTN3;
FactorsforAAA
located on chromosome 3p12.3), which demonstrated the
strongestassociationinsmokersandyetitsfunctionremains
AAAisacomplex,multifactorialdiseasewithastronggenetic
unclear[42].
component[4,6–9,32,33].About20%ofAAApatientshave
While the associations between these genetic loci and
atleastonerelativewiththiscondition[4,6,7,9,34].Since
AAA are statistically strong, the functional variants con-
thefirstcandidategenestudieswerepublished20yearsago,
tributingtothediseasearenotyetknown.Furthermore,dis-
nearly100geneticassociationstudiesusingsinglenucleotide
coveringtheunderlyingbiologicalmechanismswillrequire
polymorphisms (SNPs) in biologically relevant genes have
intensemultidisciplinaryefforts[46].
beenreportedonAAA[9].Morerecently,unbiasedgenome-
wideapproachessuchasfamily-basedDNAlinkagestudies
andgenome-wideassociationstudies(GWAS)havebeencar- 3.3.Pathway-BasedGeneticAssociationStudiesforAAA. As
riedouttoidentifysusceptibilitylociforAAA.Byproviding highlighted previously, GWAS is a powerful tool to detect
anupdatedsynopsisofourAAA-relatedresearchefforts,we genetic variants associated with a disease state of interest.
willexaminethedifferentapproachesusedtosearchoutnovel WithGWAS,itiscommontofocusonthestatisticallymost
geneticriskfactors. significant results to avoid false positive results and ignore
Scientifica 5
Table2:AAAgeneticlocidiscoveredusinggenome-wideassociationstudies.
Chromosomal Nearestgene OR Association
Polymorphism RAF
location(study) (genesymbol;geneID) [95%CI] 𝑃valuea
Contactin-3 1.33
3p12.3[42] (CNTN3;5067) rs7635818 0.42 [1.10–1.21] 0.0028
9p21.3[44] C(CDDKKNN22BBAanSt1i;s1e0n0s0e4R8N91A2)1 rs10757278 0.45 [1.221.–311.42] 1.2×10−12
9q33.1[43] D(DAABB22iInPt;e1r5a3c0ti9n0g)protein rs7025486 0.25 [1.141.–211.28] 4.6×10−10
Lowdensitylipoprotein
12q13.3[45] receptor-relatedprotein1 rs1466535 0.68 [1.101.–151.21] 4.5×10−10
(LRP1;4035)
19p13.2[41] L(LoDwLdRe;n3s9it4y9l)ipoproteinreceptor rs6511720 0.88 [0.700.–706.83] 2.1×10−10
RAF:riskallelefrequencyinpopulation;OR:oddsratio;95%CI:95%confidenceinterval;rsnumber:uniqueidentifierforeachsinglenucleotidepolymorphism
(formoreinformation,seehttp://www.ncbi.nlm.nih.gov/snp/).
GenesymbolsandIDsareavailablefromhttp://www.ncbi.nlm.nih.gov/gene/.
a𝑃valuesweretakenfromthefirstreportdemonstratingassociationwithAAAandcitedinthefirstcolumn.
Modifiedfrom[4].
“less significant” variants with potentially greater biological Thisstudyrepresentsanotherimportantdiscoveryofoursin
plausibility. A pathway-based analysis approach to GWAS theongoinginvestigationofgeneticmarkersinAAA.
ranks differentially expressed genes by the significance of
theirexpressionalongwiththebeliefofplausibilityandany 3.4.CandidateGeneStudiesforAAA. Candidategeneanal-
prior disease association. In a recent investigation of ours ysis is yet another study design and is the most common
[47],weappliedsuchabiologicalpathway-basedscreen[48] approach used to analyze the genetics behind AAAs [6, 8,
toawhole-genomeAAAcase-controldatasettodetermine 9]. Candidate genes are selected based on their biological
whethervariationsingenespreviouslyshowntobeassociated functionandtheirpotentialroleinthediseasepathogenesis.
with either coronary artery disease (CAD) or blood lipids InTable3wesummarizethemostsignificantgeneticassoci-
are also associated with AAA. The first phase of the study ationswithAAAidentifiedincandidategeneandpathway-
involved analyzing 44 lipid- and CAD-associated loci in basedstudies.
a New Zealand discovery cohort (612 controls and 608
Inoneofthecandidategenestudies,weinvestigatedthe
AAAcases),includingfour,PCSK9(1p32.3),SORT1-CELSR2-
causalrelationshipbetweenvariantsoflipoprotein(a)(LPA)
PSRC1(1p13.3),APOA1(11q23.3),andLDLR(19p13.2),which
andAAA[50].OurinterestinLPAstemmedfromthework
wereallstronglyassociatedwithbothphenotypes.Ofthese,
by others [58] who demonstrated an association between
15 lead SNPs were associated with AAA with observed 𝑃
the alleles of two SNPs in the LPA gene, rs10455872 and
values < 0.05. Three SNP associations, rs599839 on 1p13.3
rs3798220, and high plasma levels of LPA as well as CAD.
(SORT1-CELSR2-PSRC1),rs4977574on9p21(CDKN2BAS1),
andrs4775049on15q21–23(LIPC),had𝑃 < 0.1inthesame We utilized DNA samples from 35 case-control series that
includedpatientswithischemicstroke(effectivesamplesize
directionofassociationinaseparateNewZealandvalidation
(ne) = 9,396), peripheral arterial disease (ne = 5,215), AAA
cohort(1,766controlsand713AAAcases)andwerefollowed
(𝑛=4,572),venousthromboembolism(ne=4,607),intracra-
up in another separate cohort, the Wellcome Trust Case
ControlConsortium(WTCCC)AAAcohort(5,605controls nial aneurysm (ne = 1,328), and CAD (ne = 12,716), as well
and1,286AAAcases).TwoSNPsremainedsignificantfollow- as from 3,714 subjects with carotid intima. media thickness
ing WTCCC AAA cohort validation. These were the 1p13.3 measurements. The main analyses assessed the association
SORT1-CELSR2-PSRC1 rs599839, which represents a novel betweentheoutcomevariablesandthetotalnumberofminor
AAA association, and rs4977574 9p21 CDKN2BAS1, which alleles of either SNP (C allele of rs3798220 or G allele of
is in a previously reported AAA locus [44]. Replication in rs10455872).Thetotalnumberofminoralleles(orLPAscore)
additionalindependentcase-controlcohortsdemonstrateda was associated with AAA (OR: 1.23; 95% CI: 1.11 to 1.36;
consistentassociationwiththeGalleleofrs599839showing 𝑃=6.0×10−5).GiventhesubstantialoverlapbetweenCAD
aprotectiveeffectwithinsixofthe11cohortsexamined.Inall and AAA, it is conceivable that the associations of the LPA
ofthe11cohorts,theminorallelefrequency(MAF)waslower variants with AAA are mediated through their association
in cases than in controls, and when all genotyped cohorts with CAD. To investigate this potential confounder, we
wereanalyzedtogether(7,048AAAcasesand75,976controls, reanalyzed the association between the LPA variants and
pHet = 0.68), the meta 𝑃 value was 7.2 × 10−14. Modeling AAAincaseswithandwithoutahistoryofCAD.Afterthe
for confounding interactions of concurrent dyslipidemia, exclusionofpatientswithCAD,theeffectestimatesforLPA
heart disease, and other risk factors suggested that this scorebecamelowerforAAA(OR:1.11;𝑃=0.16),suggesting
marker is an independent predictor of AAA susceptibility. a strongerassociationofthe LPA scorewithatherosclerotic
6 Scientifica
Table3:MostsignificantassociationswithAAAdiscoveredincandidategeneandpathway-basedstudies.
Genename AAAcases Controls OR Association
(study) Functionalclass Polymorphism 𝑁 𝑁 [95%CI] 𝑃valuea
SORT1[47]b Lipidmetabolism rs599839 7,048 75,976 [0.706.–801.85] 7.2×10−14
IL6R[49] Inflammation rs7529229 4,524 15,710 [0.800.–804.89] 2.7×10−11
LPA[50] Lipidmetabolism rs10rs435759887222w0ith 4,572 33,520 [1.111–.213.36] 6.0×10−5
AGTR1[51]b Renin-angiotensinsystem rs5186 1,226 1,723 [1.312.–610.93] 1.1×10−6
TGFBR2[52]b TGFBsignaling rs1036095 1,904 2,616 [1.231.–529.07] 4.8×10−4
TGFBR2[52]b TGFBsignaling rs764522 1,904 2,616 [1.281.–629.25] 2.7×10−4
ACE[53]b Renin-angiotensinsystem rs4646994 1,415 1,677 [1.171.–315.56] <0.0001
MMP3[54]b DegradationofECM rs3025058 1,258 1,406 [1.213.–418.78] 3.95×10−5
1.37
MMP13[55]b DegradationofECM rs2252070 800 843 [1.04–1.82] NA
MTHFD1[56] Methioninemetabolism rs8003379 423 423 [0.206.–401.65] <0.0001
0.47
MTRR[56] Methioninemetabolism rs326118 423 423 [0.29–0.77] 0.003
LRP5[57] Lipidmetabolism rrss43978881539000 423 423 [1.421–.136.29] <0.0001
OR:oddsratio;95%CI:95%confidenceinterval;ECM:extracellularmatrix;TGFB:transforminggrowthfactorbeta;NA:notavailable.Genesymbolsare
availablefromhttp://www.ncbi.nlm.nih.gov/gene/.
a𝑃-valuesweretakenfromeitherameta-analysisorthelargestreportdemonstratingassociationwithAAAandcitedinthefirstcolumn.
bMeta-analysis.
Modifiedfrom[4].
diseasemanifestedinmorethanonevascularbed.Although (𝑃 < 0.05). When tested for genotypic association using
this study had limitations, it demonstrated an association logisticregression,sixoftheseSNPswerenominallyassoci-
between two variants in the LPA gene and AAA. Further ated,twowerenotassociated,andanadditionalSNPinGPI
studiesarenecessarytoconfirmtheseintriguingresultsasthe (glucose-6-phosphate isomerase) was identified; however,
possibleassociationbetweendyslipidemiaandAAAremains onlytheassociationwiththeSNPrs7248389inthePEPDgene
controversial. remained significant when correcting for multiple testing.
In one of our more recent AAA projects we began by Further analysis of the PEPD gene with DNA sequencing,
investigating plausible and physiologic candidate genes on however, failed to identify mutations responsible for AAA
chromosome19,whichwehadpreviouslyfoundtobelinked formation.Theseresultsdemonstratethedifficultyinmaking
to AAA in our affected relative pair-based linkage study educated guesses about potential targets in candidate gene
[38].TheAAAlinkageintervalonchromosome19q13spans studies.
approximately 4Mbp and contains over 100 genes [38]. In
order to identify a smaller set of more relevant candidate 3.5. Meta-Analysis of Genetic Association Studies on Poly-
genes, Gene Ontology [59] and the Kyoto Encyclopedia of morphisms in the Matrix Metalloproteinase Genes. A meta-
GenesandGenomes(KEGG)[60]wereusedtoidentifynine analysisisastatisticaltechniquethatcombinesresultsfrom
geneswithfunctionsrelevanttoAAApathogenesis.Eightof differentstudiesinanefforttoimprovereliability.Whilemost
thesegeneswereselectedbasedonanannotatedfunctionin commonly applied to clinical studies it can also be used to
theimmunesystemandonegene(PEPD)wasincludedbased improvethereliabilityofgeneticstudies.Tothisend,weper-
on its potential for contributing to ECM remodeling in the formedasystematicreviewandmeta-analysisofSNPswithin
AAAwall[61].UsingDNAsamplesfrom394casesand419 the gene families of matrix metalloproteinases (MMPs)
controls,wegenotyped41SNPslocatedinoraroundthenine and their inhibitors (tissue inhibitor of metalloproteinases;
candidategenesandfoundeightSNPsinthreegenes,CD22(2 TIMPs)andtheirassociationwithAAA[54].Toaccomplish
SNPs),PEPD(5SNPs),andHAMP (hepcidinantimicrobial thistask,weperformedasearchofMEDLINEandEMBASE
peptide; 1 SNP), as being nominally associated with AAA toidentifystudiesassessingtheassociationofSNPsinMMP
Scientifica 7
and TIMP genes with AAA. We initially identified a total the German general population, 3–17% are seropositive for
of 168 published studies. After more critical examination, Borreliaantibodies[71–75].Amongforestworkersonestudy
only 13 studies were deemed suitable and were included in reported7.9%seropositiverate[73]andanotherstudy29.1%
the meta-analysis. The combined population size of the 13 [76]. Our findings suggested a relationship between AAAs
studies totaled 7,037 individuals (3,581 AAA case and 3,456 and B. burgdorferi s.l. We hypothesize that the underlying
controls). Sample sizes ranged from 91 to 1,337 participants mechanismforB.burgdorferis.l.inAAAformationissimilar
perstudyandrepresentedapopulationofEuropeanancestry to that by the spirochete Treponema pallidum; alternatively,
from North America, Europe, and Australia. Studies varied AAAs could develop due to induced autoimmunity via
with regard to inclusion criteria, screening for potentially molecularmimicryorviasimilaritiesbetweenB.burgdorferi
undiagnosed AAA, distribution of conventional AAA risk s.l.proteinsandaorticproteins.Werecognizethelimitations
factors, as well as matching cases and controls for AAA surroundingthissmallstudyandareplanningalargerscale
riskfactors,age,sex,andsmoking.Allstudiesthatreported endeavoronamorediversepatientpopulation.
differencesintheprevalenceoftraditionalAAAriskfactors
between AAA and control populations conducted multiple 4.2. Genome-Wide Microarray-Based mRNA Studies. An
logistic regression analyses. Assessment of deviation from unbiasedapproachtostudyAAApathogenesisatthemolec-
the Hardy-Weinberg equilibrium was stated in 10 studies; ular level is to carry out a genome-wide microarray-based
however, evaluation of genotyping error and reporting of mRNAormicroRNA(miRNA)analysistoidentifychanges
appropriate rs numbers were evident in only four and five inmRNAandmiRNAlevelsassociatedwithAAA[7,8,33,
studies,respectively.Overall,58SNPsin10geneswereexam- 77, 78]. In silico analysis can be used to classify the genes
ined.Ofthese,eightSNPsineightgenes(rs1799750,MMP1; intofunctionalgroupsandpathways.Anothercomputational
rs3025058, MMP3; rs3918242, MMP9; rs486055, MMP10; approachistofindtranscriptionfactorbindingssitesinthe
rs2276109,MMP12;rs2252070,MMP13;rs4898,TIMP1;and geneswithalteredexpression[79].
rs9619311,TIMP3)wereassessedcommonlyinatleastthree Werecentlyreportedtheresultsofoursecondmicroar-
differentsamplepopulationsandwereincludedinthemeta- ray-basedmRNAexpressionstudyonhumanAAA[80]and
analysis. Three SNPs were assessed in two studies and the combined these findings with our previous study [81]. The
remaining47SNPswerereportedinonlyonestudy,mostly combinedanalysisrevealed57differentiallyexpressedgenes
identifiedthroughsequencingofentirecodingregions.This with consistent results in both studies (Figure4). A total of
meta-analysisrevealedthatthe5AalleleofMMP3rs3025058 32geneshadincreasedand25decreasedexpressioninAAA
(MAF = 48%)wassignificantlyassociatedwithAAAunder (Figure4). The significance of the overlap between the two
dominant(OR=1.48;95%CI:1.23to1.78;𝑃 = 3.95×10−5) independentexperimentswasevaluatedusingFisher’sexact
and recessive (OR = 1.31; 95% CI: 1.10 to 1.56; 𝑃 = 0.005) test. The odds ratio was 8.9 (95% CI: 5.6–14.3) and 𝑃 <
modelsofinheritance.Furtherinvestigationsofthismarker 2.2×10−16.Wethenselected43genesforfollow-upstudies
may improve our understanding of AAA pathogenesis and with emphasis on genes not previously implicated in AAA
assisttargetedAAAscreeningprograms. pathobiology[80].Thesegenesrepresentedawiderangeof
biological functional categories such as “calcium signaling,”
“cell development and differentiation,” “cell adhesion,” and
4.NovelInsightsonAAAPathobiology
“inflammatoryresponse.”ThemRNAlevelsweresignificantly
differentbetweenAAAandnonaneurysmalinfrarenalaortic
4.1. The Role of Microorganisms in the Pathogenesis of
controlsamplesin38/43(88%)genestestedusingaRT-PCR-
AAA. Microorganisms,includingChlamydia[62–64],Myco-
basedPCRarraymethod[80]andthedirectionofthechange
plasma pneumoniae [62], Helicobacter pylori [62], human
wasthesameseeninbothmicroarraystudies[80,81].Novel
cytomegalovirus (HCMV) [65], herpes simplex virus (HSV)
validated genes in AAA pathobiology included ADCY7,
[66],anddifferentoralbacteria[67–69]mayserveaspossible
ARL4C, BLNK, FOSB, GATM, LYZ, MFGE8, PRUNE2,
triggersforthedevelopmentofAAAs,butdataremainincon-
PTPRC, SMTN, TMODI, and TPM2. Considering that the
clusive.We,too,wereintriguedbyapossiblemicrobialtrigger
resultsoftwoindependentmicroarraystudiesandthePCR
inAAApathobiologyandthereforestudiedwhetherBorrelia
arraywereconcordant,weareconfidentthatthesegenesare
burgdorferisensulato(sl),themicroorganismresponsiblefor
differentiallyexpressedinAAAandcouldcontributetoAAA
Lyme disease, was involved in the etiology of AAAs [70].
pathogenesis.
Using a case-control design, we recruited 96 consecutive
In another study, we focused on the complement cas-
patientsdiagnosedwithAAAusingultrasonographyorCT cade for further investigation [82]. Our previous microar-
(diameter≥3cm)attheVascularSurgeryDepartment,Tech- ray study [81] had shown that 13 (38%) of the 34 genes
nical University, Dresden, Germany. We collected venous of the complement cascade arm of the “complement and
blood samples from participants and analyzed them for coagulation cascades” KEGG pathway had significantly dif-
antibodies against B. burgdorferi using an enzyme-linked ferentmRNAexpressionsbetweenAAAandcontroltissues.
immunosorbentassay(ELISA).Anypositiveresultwascon- Five had increased and eight had decreased expression in
firmedbyWesternblotanalysis.AmongAAApatients,34% AAAcomparedtothecontroltissues.Furthermore,follow-
were seropositive for B. burgdorferi s.l. antibodies, whereas up studies showed strong staining of AAA tissue samples
only15.7%ofpatientswithperipheralartery disease (PAD) using an antibody specific to C2, one of the complement
were seropositive (Figure3; 𝑃 = 0.003). In comparison, in cascadeproteins.Insilicoanalysisofthepromoterregionsof
8 Scientifica
40
34.4
%)
e ( 30 29.1
c
n
e
al
v
e 20
pr 15.7 16.9
o
er 12.5
S
10 7.9
4.0
2.8 2.7
AAA PAD Random Random Lumber- Blood Lumber- Blood Blood
sample sample jacks donors jacks donors donors
n=96 n=108 n=288 n=1228 n=630 n=200 n=499 n=472 n=1000
Baden-Wurt-Baden-Wurt- Berlin-Bran-
Saxony Saxony temberg temberg BrandenburgBrandenburg denburg Bavaria Hamburg
1997[71] 1992[72] 1996[73] 1996[73] 2000[76] 1992[74] 1997[75]
Figure3:SeroprevalencesforBorreliaburgdorferisensulatoantibodiesindifferentriskgroupsinGermany.OnlystudieswithbothELISA
andimmunoblottingdatawereincluded.AAA,abdominalaorticaneurysm;PAD,peripheralarterydisease.Fordetails,see[70].Reproduced
withpermissionfrom[70].
the 13 differentially expressed complement cascade genes lowerintheabdominalthaninthethoracicaorta.Abdom-
usingWholeGenomerVISTAshowedenrichmentforbind- inal aorta is known to be more susceptible for aneurysm
ingsitesforatranscriptionfactorSTAT5Awhencomparedto formation.DownregulationofHOXgenescouldhaveseveral
theentiregenome.ToexperimentallyvalidatethatSTAT5A detrimental effects in the human aorta, since HOX genes
binds on the promoters of the complement cascade genes, havewell-establishedrolesinregulatingcellproliferationand
chromatinimmunoprecipitationfollowedbyhybridizationto differentiation[83].
high-density promoter arrays (ChIP-chip) was carried out
using microarrays covering 10kbp of the promoters of all
4.3. Genome-Wide MicroRNA (miRNA) Analysis for AAA.
known genes. STAT5A demonstrated binding to 6,297 dis-
miRNAs are small, well-conserved, noncoding molecules
tinctgenes,1,095(17%)ofwhichweredifferentiallyexpressed
which can inhibit gene expression at the posttranscrip-
in human AAA tissue (431 had increased expression and
tional level. Each miRNA is predicted to regulate a large
664 had decreased expression). In the complement cascade
number of target genes (mRNAs). We recently published
genes,strongevidenceforSTAT5Abindingwasfoundon10
ourmicroarray-basedgenome-wideanalysisofmiRNApat-
ofthe34complementcascadegenesandmoderateevidence
terns in human AAA [84]. Five miRNAs (miR-133b, miR-
onninecomplementcascadegenes.Insummary,thisstudy 133a, miR-331-3p, miR-30c-2, and miR-204) found to be
providedmultiplelinesofevidencethatcomplementcascade downregulated in AAA were then validated with real-time
isimportantinAAApathogenesisandthatinhumanAAA quantitative RT-PCR and an independent set of samples.
thepathwayisactivatedviathelectinandclassicalpathways. Extensivebioinformaticanalyseswerecarriedouttoidentify
Our microarray-based mRNA expression profiles [81] the mRNA targets of these miRNAs (Figure5). A total of
also formed the foundation for the study on HOX (home- 1,836 potential target genes were found, 222 of which were
odomain-containing)genesinAAA[83].Wehadfoundthat significantlyupregulatedinourpreviouslypublishedmRNA
78HOXgeneswereexpressedintheadulthumanaortaand expressionstudy[81].OneofthesetargetswasMMP9which
that 31 of these had significantly different mRNA levels in hasawell-establishedroleinAAApathogenesis[85].
AAAcomparedtocontrolabdominalaortictissuesfroman
age-,sex-,andethnicity-matchedgroupofindividuals.Tenof
4.4. Animal Models of AAA Pathogenesis. While it is our
these31geneswereso-calledclassicHOXgenes.Interestingly,
preferencetousehumanAAAtissueinourstudies,itcanonly
themRNAlevelsofallofthemweresignificantlydecreasedin
be obtained during open repair operations and, therefore,
AAA[83].HOXA4wasthemostsignificantlydecreasedHOX
studies on human AAA are restricted to end-stage disease
geneinhumanAAAtissuebasedonmicroarrayresults.We with hugely altered aortic tissue architecture. Thankfully,
confirmeditsdecreasedexpressioninanindependentsetof severalmousemodelsforaneurysmshavebeendeveloped[8]
12AAAcasesand12similarlyagedcontrolsusingareal-time providinganopportunitytostudyearlystagesofaneurysm
quantitativeRT-PCRassay.WealsodetectedHOXA4mRNA development.Themostwidelyusedofthemistheso-called
inculturedhumanaorticSMCsandaorticendothelialcells. angiotensin II- (AngII-) induced mouse model of aortic
AnotherintriguingfindingwasthatHOX4Aexpressionwas aneurysmsinwhichmicelackingtheapolipoproteinEgene
Scientifica 9
AAA CTL
1 2 3 4 1 2 3 4 ESMymILbIoNl1 G1e1n1e1 I7D log2 Fold
PPP1R3C 5507
RAMP1 10267
TPM2 7169
LMOD1 25802 −3 −8
LDOC1 23641
ITGA5 3678
MFGE8 4240
SMTN 6525
PPP1R12B 4660
RASL12 51285
ZBTB16 7704
NPTX2 4885
ITGA10 8515 −2 −4
PRUNE2 158471
HSPB2 3316
SMARCD3 6604
NTRK3 4916
CSRP2 1466
FHL5 9457
LAMA2 3908
TMOD1 7111 −1 −2
LARP6 55323
PDE8B 8622
FOSB 2354
MX2 4600
MARCKS 4082
FAM20B 9917
KIAA0746 23231
ARL4C 10123
PLEK 5341 0 0
ADCY7 113
CD4 920
CCL4 6351
FCGR2B 2213
CCL8 6355
LYZ 4069
BLNK 29760
ICL1130oRrAf18 803158837 1 2
NCF4 4689
DHRS9 10170
MNDA 4332
CYTIP 9595
CD48 962
PTPRC 5788
GPR65 8477
CD83 9308 2 4
DUSP6 1848
EVI2B 2124
MARCKS 4082
KIAA0746 23231
IGJ 3512
LCP2 3937
TMEM176B 28959
CADM1 23705
SAMSN1 64092 3 8
GATM 2628
CXCR4 7852
CXCR4 7852
CXCR4 7852
Figure4:Heatmapofthe57differentiallyexpressedgenesfoundintwoindependentmicroarraystudiesforAAA.Theheatmapwasproduced
byhierarchicalclusteringoftheprobesetdata.Probesetsforgenesarerepresentedbyrowswiththegenedendrogramatleft.Thereare61
probesetsrepresentedsincethereareredundantprobesetsontheAffymetrixmicroarrayforsomegenes,forexample,CXCR4,whichisthe
generepresentedbythreelinesatthebottom.GenesymbolsandgeneIDsontheright(foundathttp://www.ncbi.nlm.nih.gov/).Samples
(4AAAsamplesand4controls)arerepresentedbycolumns.GreencolorindicatesdecreasedexpressioninAAAandredcolorindicates
increasedexpressioninAAA.
receive an infusion of angiotensin II and develop vascular bypreventingtheaccumulationofinflammatorycellstothe
lesionsincludingatherosclerosis,dissection,anddilatationof aneurysm[86].
thesuprarenalaorta.Inacollaborativestudywiththeteam
fromtheNationwideChildren’sHospital,weinvestigatedthe 5.ElectronicMedicalRecordsand
role of Notch signaling in aneurysm formation using this Biobanks:NewResourcesfor
mousemodel[86].Notch1isahumangenethatencodesa
EpidemiologicalandGeneticResearch
transmembrane receptor which plays multiple roles during
development and cell differentiation. Notch 1 signaling was GHS is an integrated, comprehensive health care delivery
foundtobeactivatedinthisAAAmousemodel.Additionally, systemthatservesalarge,stable,mainlyruralpopulationin
Notch1haploinsufficiencyandpharmacologicalinhibitionof North central and Northeastern Pennsylvania [22]. GHS is
Notch1signalingreducedtheincidenceofaorticaneurysms considered one ofthe most wired health care organizations
10 Scientifica
C9orf91 ZNF217
KIAA1147 MAP3K11 SAMD9 FAM73AGCLC LASP1RAB11FIP1 CD47
CXCR3 AGRP JDP2 GABPB2 MIOS PFAS
GNB4 CMTM6 SLC4A8 ZNF385A PWWP2B SFXN5
GCH1 DBNL
DUSP5 SQLE TMEM123 MCL1
CAPN3 PPP6R3
RCE1 NIPA2 miR-133a IDH1 AK2
OSCAR COL1A1 DOK1 SPTY2D1
LYPLA2 FUCA1 ELMO1 miR-133b WIPI2
FAM46C CDCA8 SYAP1 CDK5R1 KLRK1 FSCN1 TNK2 SGK1
CD86
NRIP3 TGIF2 PABPC1 ENC1 PSD3 PREX1
RAPGEF6 ATOX1 MYO9B IQGAP2 TCF7
ATP2B1 SMARCD1 TNFRSF10B SRSF2 SNX30
DNM2 CHKB CNN2 LHFPL2 TMEM86A
CCNY LAMB3
YTHDF3 DNAJB1
CCR2 MME CBFA2T3 SFXN2 TGFBR1 CSRNP1SLC7A8 TOMM40
TP53INP1
NTM IL23A PRF1 EDEM1 TGOLN2 FURIN
HCAR3 SELL GALNT4 P2RX7AMMECR1L CYBB BCL11A PLK3 RNF44 VASH1 CHST11
TNFFRASMF8178ALNRRCCEH8D1 POUM2FA2PK1IPCEFA1RHGAP30DUSP4 RASSF5 EPHB2 BIN1 PRDM1 LEP ICOS ATG7 CLEC2BPABPN1IL10RA
SLA2 M6PR GREM1 GRAMD4 CDC7 DUSP14 STXBP5 HIC2 FZD5SOCS1 WDR81 GRASP ZNF319 PARP10
C22oErfZ1R3 CCRL2 GGA2 C3orf62UBE2J1 miR-204 NEKC6D5 DEDEDM2R3CWFT1N9LFA1IP3 AVPHHL1A LRCH4 DAGLADENND1AmiR-331-3p RARA ZCNFLF1652COPS7B
PTDSS1 KDM2A ARID3B VASP HCAR2 DR1 ARAP2 PTPN2 GPR114 ITPKB
MARCKSB3RGPNS6TK5A5ADSGOPRTLAN12FAAIFPA8ML210R7BAMSSSF4A26ANRBAFG2PEAHTD4SP1RED1C1T1oBrCf715D9 ATPP1CMS1332orf5JARIDT2FEC IL7R ABCAP12RY8USF2KLAFQC1LP6M9N TMRAARFK3R2AB1K1IFAIPA41539PLGEAKS7
AHR PDE4B DUSP19 ING3 RELT MICAL3 DCLRE1B
BMP2K MRPS34 KIAA0226 HNRPA2 P2RX1 IER5 KCNJ10 SMG5
ARL4C PRDM2 TMEM127 MOXD1 ZC3HAV1
C2orf68
CD28
−39.40 −26.70 −17.70
RNA-RNAΔG(kcal/mol)
Figure5:ANetworkofmiRNAs,miR-133a,miR-133b,miR-331-3p,andmiR-204,andtheirtargetgenes.EachmiRNAispredictedtoregulate
alargenumberoftargetgenes(mRNAs).Bioinformaticanalysispredictedthat222geneswithupregulatedexpressioninAAAbasedona
priormicroarraystudy[81]weretargetsofmiR-133a,miR-133b,miR-331,ormiR-204.ThepredictedminimumfreeenergyofthemiRNAand
targetmRNAhybridizationfromtheprogramRNAhybridversion2.1.isshownbythelineandnodecolor.BlacklinesforYTHFD3indicate
󸀠 ∗
thatthe3UTRsequencewasnotavailablefromEnsemblBioMart,andtheminimumfreeenergywasnotcalculated.miR-30c-2 wasnot
∗
includedbecauseitisamiRNA strandthatisusuallydegradedandthereforenonfunctional.Thefigureisreproducedfrom[84].
in the USA and it has utilized a unified EMR since 1996 Inthisstudyapproximately900AAAcasesandover14,000
[22].Tofacilitateresearchdataminingandanalysis,in2008, controlswereidentifiedfromtheEMRatGHSandusedto
GHS implemented a data warehouse system including the identify risk factors for AAA. We replicated the direction
outpatientrecordsofallpatientsseenbybothprimarycare andmagnitudeofseveralknownriskfactorsoriginallyfound
and specialty providers [22]. Another important initiative intraditionalepidemiologicalAAAstudies[88].Thisstudy
launched by GHS was the biobanking program called the demonstrated that EMR is a useful resource to assess risk
MyCode project, which includes a central repository of factorsandidentifynewassociations.
patient samples (blood, DNA, serum, and tissue) that are GHSisoneoftheninemembersoftheelectronicMEdical
linkable to EMR for broad research use in a manner that Records and GEnomics (eMERGE) network, a National
protectsconfidentialityofpatientinformation[87]. HumanGenomeResearchInstitute-(NHGRI-)fundedcon-
To test our hypothesis that EMR can be utilized retro- sortiumwhichisdevelopingmethodsandbestpracticesfor
spectively to identify risk factors and that it is comparable the utilization of the EMR as a tool for genomic research
totraditionalepidemiologicalmethodsforriskfactorassess- [89].EachmemberintheeMERGEconsortiumhasanEMR
mentofacomplexdisease,weusedAAAasatestcase[88]. andabiobankandhasproposeddiseasesortraitsforwhich