Coordinated regulation of hyaluronan and aggrecan content in the articular cartilage of immobilized and exercised dogs.
OBJECTIVE
To study the influence of joint loading and immobilization on articular cartilage hyaluronan concentration and histological distribution in the knee joints of young dogs subjected to 11 weeks' immobilization by splinting, and 15 weeks' running exercise at a rate of 40 km/day.


METHODS
The amount of hyaluronan in articular cartilage was determined by a competitive binding assay using a biotinylated hyaluronan binding complex (HABC) of aggrecan and link protein. Histologic sections were stained for the localization of hyaluronan with the HABC probe. Extracted proteoglycans were characterized by sodium dodecyl sulfate agarose gel electrophoresis.


RESULTS
Immobilization significantly reduced the concentration of hyaluronan in all sites studied (tibial and femoral condyles, patellar surface of femur). The proportion of hyaluronan to total uronic acid (mainly from aggrecan) remained unchanged because of a concurrent decrease in aggrecan. The ratio of hyaluronan and aggrecan remained constant also in runners. The staining pattern of free hyaluronan in the tissue sections and the electrophoretic mobility of the extracted proteoglycans were not affected by the different loading regimes.


CONCLUSIONS
Reduced joint loading due to splint immobilization significantly decreases both hyaluronan and aggrecan in the articular cartilage. The remarkably parallel changes in aggrecan and hyaluronan content suggest that joint loading exerts a coordinated influence on their metabolism.
Haapala
J
J
Department of Anatomy, University of Kuopio, Finland.
Lammi
M J
MJ
Inkinen
R
R
Parkkinen
J J
JJ
Agren
U M
UM
Arokoski
J
J
Kiviranta
I
I
Helminen
H J
HJ
Tammi
M I
MI
D053674:Aggrecans; D000818:Animals; D001667:Binding, Competitive; D001710:Biotin; D002358:Cartilage, Articular / Q000378:metabolism*; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D016326:Extracellular Matrix Proteins; D005260:Female; D006025:Glycosaminoglycans / Q000378:metabolism; D006820:Hyaluronic Acid / Q000378:metabolism*; D007103:Immobilization; D037181:Lectins, C-Type; D009043:Motor Activity; D009994:Osmolar Concentration; D011509:Proteoglycans / Q000378:metabolism*; D012420:Running; D013997:Time Factors; D014018:Tissue Distribution; D014574:Uronic Acids / Q000378:metabolism
D053674:Aggrecans; D016326:Extracellular Matrix Proteins; D006025:Glycosaminoglycans; D037181:Lectins, C-Type; D011509:Proteoglycans; D014574:Uronic Acids; D001710:Biotin; D006820:Hyaluronic Acid