LEUKEMIA INHIBITORY FACTOR IS MITOGENIC TO OSTEOBLASTS

Leukemia inhibitory factor (LIF) regulates cell growth and is produced by a variety of tissues, including bone. Previously we have shown tha t recombinant human LIF induced an increase in osteoclast number, bone formation, and DNA synthesis. In the present study, we have defined t he cells in intact bone at which the proliferative effects of LIF occu r, using simultaneous enzyme histochemistry and autoradiographic techn iques. The area of alkaline phosphatase-positive staining was increase d twofold (p = 0.0008) and the number of [H-3]thymidine-positive cells was increased twofold (p = 0.0024) in LIP-treated bones. The radiolab eled cells either colocalized with alkaline phosphatase or were in the osteoprogenitor region. They were not found in the acid phosphatase-p ositive staining osteoclasts. These results indicate that cells which have a mitogenic response to LIF are bone-forming rather than bone-res orbing cells. (C) 1997 by Elsevier Science Inc. All rights reserved.