In Vitro and in Vivo Models of Cartilage Injury
Darryl D. D'Lima, MD; Sanshiro Hashimoto, MD; Peter C. Chen, PhD; Martin K. Lotz, MD; Clifford W. Colwell Jr., MD

Our previous study1 demonstrated that chondrocytes undergo apoptotis in response to mechanical injury to full-thickness cartilage explants. To validate this response, several models of injury across species and in vivo were examined.

Methods

Full-thickness cartilage explants were harvested from weight-bearing portions of adult bovine femoral condyles, and 5-mm-diameter disks were punched out with a dermal punch. Explants were allowed to stabilize in Dulbecco modified Eagle medium supplemented with 10% fetal bovine serum for forty-eight hours. Explants were then divided into two groups: load and control. The load group underwent a single 500-msec injury load of 30% strain in radially unconfined compression. The control group was not loaded. A 30% strain was found to generate a more consistent injury than the previous loading protocol1. At ninety-six hours after injury, explants underwent histologic examination and the number of apoptotic cells was counted with use of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling). Apoptosis was confirmed in selected samples by electron microscopy and immunostaining of a neo-epitope of cytokeratin. The experiment was repeated with use of normal human articular cartilage harvested from the femoral condyles of postmortem donors.

Osteochondral model: To determine whether the presence of subchondral bone affected the cartilage response, whole rabbit patellae …


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