Human prosthesis loosening fibroblasts (PLFs) form resorption pits on whale dentin slices in vitro. (a) After 4 weeks of culture on dentin slices, PLFs exhibited morphological signs of bone resorption and produced characteristic signs of resorption pits (closed arrowheads) with remains of PLFs still in situ (open arrowheads). (b) Addition of 10 ng/ml tumour necrosis factor (TNF)-α to the medium enhanced the resorption of dentin, as seen from multiple resorption pits (closed arrowheads). Again, remains of PLFs were seen on the dentin slices (open arrowheads). (c) TNF-α 100 ng/ml also enhanced the size of the resorption pits generated by the PLFs (closed arrowhead). (d) Dentin slices on which no PLFs were cultured showed a clear and smooth surface and no erosions were seen. (e) Freshly differentiated osteoclasts that were used as controls produced characteristic resorption pits after 4 days (closed arrowhead). (f) However, there were considerable differences between osteoclast cultures, with some osteoclasts starting bone resorption only after 2 weeks (closed arrowhead).
Pap et al. Arthritis Res Ther 2003 5:R163-R173 doi:10.1186/ar752