In previous studies, we described a layer of tissue that formed around
methylmethacrylate cement that had been implanted into the posterior
cervical spine of dogs. We are now reporting on a rat model in which we
induced, in the interface between the bone of the posterior elements of the
dorsal spine and methylmethacrylate, the formation of a layer of tissue
that was morphologically similar to the tissue that had been produced in
the dogs. As in the dogs, we noted macrophages and giant cells and we
demonstrated that the interface tissue synthesized several
basement-membrane components (type-IV collagen, laminin, and fibronectin).
In addition, we demonstrated the synthesis of an additional
extracellular-matrix protein--type-VI collagen. We also showed that
extracts of organ cultures of tissue from the rat model degraded type-I
collagen into three-quarter and one-quarter-length fragments. Such
enzymatic activity is characterized of mammalian collagenase, an enzyme
that is known to play a critical role in the resorption of bone.