Aggrecan(PG)isthepredominantproteoglycanspeciesinarticularcartilage.Itiscomposedofacoreproteinof210kDatowhichover100chondroitinsulfatechains,about20-50keratansulfatechainsandO-linkedaswellasN-linkedoligosaccharidesarecoventlyattached.

Thecoreproteincontainsthreedistinctglobulardomains(G1-G3).G1isattheaminoterminus,separatedbyashortextendedsegmentfromG2,whileG3isatthecarboxyterminalend.TheG1aminoterminalregioncaninteractnoncovalentlywithhyaluronicacid(HA)andhasthenbetermedthehyaluronicacidbindingregion(HABR).AlinkproteininteractwithboththeG1regionandtheHAtostABIlizethisinteraction.PGisproducedbychondrocytes,anditsproductionisregulatedbycytokinesandgrowthfactorssuchasIL1β,TNFα,IGF1orTGFβ.Inextracellularmatrix,asmanyas200aggrecanmoleculescanbindtoonesingleHAmoleculetoformanaggregate(MW:5107to5108).

Animbalanceinthesynthesisanddegradationofthematrixcomponentsisacommonfeatureofbothosteoarthritisandrheumatoidarthritis.ThelossofPGandothermatrixcomponentsfromthecartilageleadstodestructionofthetissue,causingcompletedeteriorationofthearticularsurface.SeveralrecentpublicationssuggestthatthePGandPGfragmentsreleasedinsynovialfluidandserumduringthedegradationprocessmightserveasMarkersofmetabolicchangesindiseasedcartilage.Cellcultureisacommonlyusedprocedureforthestudyofcartilagemetabolism.ThemeasurementofPGandothermatrixcomponentsinculturesupernatantsandcellularcontentscanassisttheanalysisofofcytokine,growthfactor,drugandpotentialchondroprotectivesubstanceeffectsonthecartilagehomeostasis.IBLInternationalsellsthisELISAforthemeasurementofhumanaggrecantoaidthestudyofthisimportantcartilageconstituent.TheAggrecan/PGELISAisconvenient,highlyspecific,andallowsaccuratemeasurementofPGinsynovialfluid,serumandculturesupernatant.

Thisassayisaninterestingtoolfortheexplorationofthecartilagemetabolism.