Chondrocytes in culture produce a mechanically functional tissue.
A mechanically testable tissue was grown in vitro from rabbit chondrocytes that were initially plated at high density (approximately 80,000 cells/cm2). The DNA, collagen, and proteoglycan content, as well as the tissue thickness, tensile stiffness, and synthesis rates, were measured at 4, 6, and 8 weeks. The biochemical properties were similar to those for immature cartilage, with predominantly type-II collagen produced; this indicated that the cells retained their chondrocytic phenotype. The tissue formed a coherent mechanical layer with testable tensile stiffness as early as 4 weeks. The tensile elastic modulus reached 1.3 MPa at 8 weeks, which is in the range of values for native cartilage from the midzone. Collagen density was approximately 24 mg/ml at 8 weeks, which is about one-half the value for native cartilage, and the collagen fibril diameters were smaller. Chondrocytes in culture responded to culture conditions and were stimulated by cytokine interleukin-1beta. When culture conditions were varied to RPMI nutrient medium with lower fetal bovine serum and higher ascorbic acid concentrations, the thickness decreased and the modulus increased significantly. Interleukin-1beta, added to the 8-week culture for 2 weeks, caused a decrease of 60% in thickness, a decrease of 81% in proteoglycan content, and a decrease of 31% in collagen content; this is similar to the response of cartilage explants to interleukin-1beta. This cartilage analog may be useful as a model system to study structure-function relationships in cartilage or as cartilage-replacement tissue.
Fedewa
M M
MM
Department of Orthopaedic Surgery, University of Minnesota, Minneapolis 55455, USA.
Oegema
T R
TR
Schwartz
M H
MH
MacLeod
A
A
Lewis
J L
JL
D000818:Animals; D002356:Cartilage / Q000737:chemistry / Q000166:cytology* / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects; D003094:Collagen / Q000032:analysis / Q000648:ultrastructure; D003470:Culture Media / Q000494:pharmacology; D046508:Culture Techniques / Q000379:methods; D004247:DNA / Q000032:analysis; D004548:Elasticity; D005109:Extracellular Matrix / Q000187:drug effects / Q000502:physiology; D007375:Interleukin-1 / Q000494:pharmacology; D008297:Male; D008855:Microscopy, Electron, Scanning; D011509:Proteoglycans / Q000032:analysis; D011817:Rabbits; D013314:Stress, Mechanical; D013997:Time Factors; D014867:Water / Q000032:analysis
D003470:Culture Media; D007375:Interleukin-1; D011509:Proteoglycans; D014867:Water; D003094:Collagen; D004247:DNA