title: Time, stress, and location dependent chondrocyte death and collagen damage in cyclically loaded articular cartilage.
abstract: We investigated the effect of light (0.1 MPa), moderate (1 MPa) or heavy (5 MPa) cyclical stresses applied continuously or intermittently for 0 to 72 h on cell death and collagen damage in adult bovine cartilage explants. No increase in cell death was observed in the cartilage loaded with a continuous cyclic stress at 0.1 MPa for up to 72 h. Cell death occurred in the uppermost superficial tangential zone (STZ) of explants after loading for 1 h at 1 MPa, and reached a maximum depth of 61+/-23 micro m by 6 h (at the rate of 9+/-6 micro m/h). At 5 MPa, cell death occurred in the STZ after as little as 1 min (30 cycles) of loading, and reached a maximum depth of 70+/-2 micro m by 60 min (47+/-8 micro m/h). When an intermittent (with 2 s on, 2 s off) stress of 5 MPa was applied, cell death appeared in the STZ after 2 min (30 cycles) and increased to a depth of 63+/-2 micro m at 60 min (45+/-11 micro m/h). No significant differences were observed between the continuous and intermittent loading conditions. Both collagenase-cleaved and denatured collagen fibers were found in the STZ of explants loaded at 1 and 5 MPa. We concluded that load-induced cell death depends on load duration and magnitude, and that the chondrocytes in the STZ are more vulnerable to load-induced injury than those in the middle and deep zones.
authors.affiliation: Laboratory for Soft Tissue Research, The Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021-4891, USA. chench@hss.edu
authors.forename: Chih Tung
authors.initials: CT
authors.lastname: Chen
authors.forename: Madhu
authors.initials: M
authors.lastname: Bhargava
authors.forename: Peggy M
authors.initials: PM
authors.lastname: Lin
authors.forename: Peter A
authors.initials: PA
authors.lastname: Torzilli
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000502:physiology*; D002417:Cattle; D016923:Cell Death; D019902:Chondrocytes / Q000502:physiology*; D003094:Collagen / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D017364:Collagenases / Q000378:metabolism; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D010507:Periodicity; D013314:Stress, Mechanical; D013997:Time Factors; D016474:Weight-Bearing
chemical_list: D003094:Collagen; D017364:Collagenases