Chronic inflammatory diseases are characterized by elevated levels of tumor necrosis factor (TNF) and decreasing bone mineral density. TNF promotes differentiation of bone resorbing osteoclasts from their hematopoietic precursors. Its impact on differentiation of mesenchymal precursors of bone forming osteoblasts isolated from adipose (ASC) was largely unknown. I found that TNF did neither induce osteoblastic differentiation of ASC nor exhibited an impact on osteoblastic differentiation in vitro. Thus, TNF mediates osteolysis in vivo presumably mainly by its pro-osteoclastogenic effect.
