OBJECTIVETo explore the relationship between TNF-alpha, transcriptional co-activator with PDZ-binding motif (TAZ) and bone disease of multiple myeloma.

METHODSThe biological characteristics, especially the osteogenic potential of marrow MSCs from myeloma patients and normal subjects were studied. Real-time RT-PCR and Western-blot were employed to detect mRNA and protein expression of TAZ in MSCs. The concentration of TNF-alpha in the marrow plasma was detected using ELISA method. CD138(+) myeloma cells were cocultured with normal MSCs with or without anti-human TNF-alpha monoclonal antibody in the Transwell system. Real-time RT-PCR was employed to detect the mRNA expressions of ALP, Cbfa1 and TAZ in MSCs two weeks later. von Kossa staining was used to detect the mineral deposition. TNF-alpha was added into the culture media of normal marrow MSCs and real-time RT-PCR and Western-blot were employed to detect mRNA and protein expression of TAZ in MSCs one week later.

RESULTSReal-time RT-PCR revealed that the mRNA of osteogenic markers was decreased in comparison with that of normal controls after cultured in the osteogenic medium. von Kossa staining showed weakened mineral deposition in MSCs from multiple myeloma patients compared with that in normal subjects after osteogenic differentiation for two weeks. The mRNA and protein levels of TAZ in the MSCs from myeloma patients were decreased. TNF-alpha concentration in the marrow plasma of myeloma patients was higher than that in the normal controls [(355.4 +/- 49.1) vs. (92.3 +/- 17.2) pg/ml]. CD138(+) myeloma cells inhibited mRNA expressions of ALP, Cbfal1 and TAZ in MSCs, which could be partially reversed by anti-human TNF-alpha monoclonal antibody.

CONCLUSIONThe osteogenic potential of MSCs from myeloma patients is significantly decreased in comparison with that in normal subjects, which may play an important role in the pathology of myeloma bone disease. TAZ expression inhibited by TNF-alpha may play an important role in this inhibition effect.