Figure 1.

Fibroblast-like cells from the synovial-like interface membrane around loose joint arthroplasties produce signs of bone resorption in the severe combined immunodeficient (SCID) mouse model of matrix degradation. (a) and (b) Cultured prosthesis loosening fibroblasts (PLFs) were soaked into a collagen sponge and coimplanted with normal human bone under the renal capsule of SCID mice. After 60 days, histological evaluation showed attachment and invasion of the PLFs into the bone matrix (a, magnification ×630). The presence of PLFs in resorption pits was seen predominantly at sites at which the cells left the collagen sponge (b, magnification ×630). (c) Immunohistochemistry with antivimentin antibodies that recognize human fibroblasts but not mouse cells demonstrated the human origin of the fibroblast-like cells invading the bone. Human, vimentin-positive PLFs (arrowheads) were found abundantly in the SCID mouse sections (c, magnification ×630) and exhibited close contact to the resorption lacunae.