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We analysed the cytoskeletal proteins and extracellular matrix components of in vitro cultured BMSC both in resting state and after activation with IFN gamma and TNF alpha, using an immunoperoxidase procedure. BMSC expressed fibronectin, alpha-actin, beta-tubulin, vimentin and vinculin while cytokeratinpan, GFAP, neurofilament, desmin and laminin were not expressed. This pattern of expression was not affected by addition of TNF alpha and IFN gamma, but differs from human tonsil stromal cells for laminin expression and alpha-actin localization.

We investigated whether stromal cells obtained from human tonsils could interact and modulate the proliferation of the osteosarcoma cell in order to determine why lymph node metastases usually have a low incidence and remain occult using routine examinations. The effects of the supernatant of resting or activated stromal cells were analysed on osteoblastic cell proliferation of three different cell lines (HOS, U2, OS, MG-63). Only the proliferation of MG-63 was significantly inhibited. The direct adhesion of stromal cells to the osteosarcoma cell lines caused a greater inhibition of the proliferation of all three lines tested.

Osteoblastic cells are in direct or indirect contact with lymphocytes and bone marrow cells that are the main targets of HIV-1. Therefore we analysed whether HIV-1 could infect these cells using three bone cell lines (HOS, MG-63, U2 OS) as a model. These cells were infected with HIV-1 (strain NL4-3) and the supernatants were harvested every day for 20 days for p24 antigen measured using an ELISA immunoassay. The DNA of infected cells was extracted at days 3, 9, and 12 and the PCR for gag gene was performed using Jurkat cell line as a negative control and ACH-2 cell line as a positive control. Our results demonstrated that HOS, MG-63 and U2 OS are not infected by HIV-1. These data were confirmed using PCR that is currently the most sensitive procedure available.