Contribution of collagen network features to functional properties of engineered cartilage.
BACKGROUND
Damage to articular cartilage is one of the features of osteoarthritis (OA). Cartilage damage is characterised by a net loss of collagen and proteoglycans. The collagen network is considered highly important for cartilage function but little is known about processes that control composition and function of the cartilage collagen network in cartilage tissue engineering. Therefore, our aim was to study the contribution of collagen amount and number of crosslinks on the functionality of newly formed matrix during cartilage repair.


METHODS
Bovine articular chondrocytes were cultured in alginate beads. Collagen network formation was modulated using the crosslink inhibitor beta-aminopropionitrile (BAPN; 0.25mM). Constructs were cultured for 10 weeks with/without BAPN or for 5 weeks with BAPN followed by 5 weeks without. Collagen deposition, number of crosslinks and susceptibility to degradation by matrix metalloproteinase-1 (MMP-1) were examined. Mechanical properties of the constructs were determined by unconfined compression.


RESULTS
BAPN for 5 weeks increased collagen deposition accompanied by increased construct stiffness, despite the absence of crosslinks. BAPN for 10 weeks further increased collagen amounts. Absence of collagen crosslinks did not affect stiffness but ability to hold water was lower and susceptibility to MMP-mediated degradation was increased. Removal of BAPN after 5 weeks increased collagen amounts, allowed crosslink formation and increased stiffness.


CONCLUSIONS
This study demonstrates that both collagen amounts and its proper crosslinking are important for a functional cartilage matrix. Even in conditions with elevated collagen deposition, crosslinks are needed to provide matrix stiffness. Crosslinks also contribute to the ability to hold water and to the resistance against degradation by MMP-1.
Bastiaansen-Jenniskens
Y M
YM
TNO Quality of Life, Business Unit BioSciences, Leiden, The Netherlands; Erasmus MC, University Medical Centre Rotterdam, Department of Orthopaedics, The Netherlands.
Koevoet
W
W
de Bart
A C W
AC
van der Linden
J C
JC
Zuurmond
A M
AM
Weinans
H
H
Verhaar
J A N
JA
van Osch
G J V M
GJ
Degroot
J
J
D000464:Alginates; D000629:Aminopropionitrile / Q000494:pharmacology*; D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000473:pathology; D002417:Cattle; D002452:Cell Count; D002478:Cells, Cultured; D019902:Chondrocytes; D005109:Extracellular Matrix / Q000737:chemistry* / Q000187:drug effects / Q000201:enzymology; D024022:Fibrillar Collagens / Q000378:metabolism*; D015870:Gene Expression; D020782:Matrix Metalloproteinases / Q000494:pharmacology; D010003:Osteoarthritis / Q000473:pathology; D010539:Permeability; D010641:Phenotype; D012038:Regeneration / Q000502:physiology*; D013314:Stress, Mechanical; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods*
D000464:Alginates; D024022:Fibrillar Collagens; D000629:Aminopropionitrile; D020782:Matrix Metalloproteinases