engleski

Lipopolysaccharide injection suppresses osteoblastogenesis but stimulates osteoclaStogenesis from mouse bone marrow cells

Lipopolysaccharide (LPS) from gram-negative bacteria may cause chronic inflammation and subsequent bone loss, and has been involved in the pathogenesis of several bacterially induced bone disseases like peridontitis, osteomyelitis and bacterial arthritis. LPS strongly stimulates osteoclast formation and induces production of many local pro-inflammatory factors, such as tumor necrosis factor α , interleukin-1, prostaglandin E2. The aim of our study is to investigate the effects of LPS on bone cell differentiation in the bone marrow microinvironment. C57BL/6 mice were injected intraperitonealy once a week during 4 weeks in a dose of 5 µ g and 20 µ g LPS/g body mass. After 5 weeks, splenocytes from these mice were stimulated by mitogen Concanavalin A (ConA ; 10µ g/mL ) or LPS (25µ g/mL) for 4 days in culture followd by MTT cell proliferation assay. Bone marrow cells were cultured under conditions stimulating for osteoblastogenic differentiation (ascorbic acid, dexamethasone and β -glycerolphosphate) or osteoclastogenic differentiation (receptor activator of nuclear factor-κ B ligand and macrophage colony-stimulating factor) cultures. Osteoclast-like cells were identified as tartarat-resistant acid phosphatase (TRAP)-positive multinucleated cells. Osteoblast colonies were detected as alkaline phosphatase-positive colony-forming units. There was a dose-dependent stimulation in cell proliferation after LPS injection, which increased further upon restimulation in vitro by ConA and LPS. LPS-stimulation significantly suppressed osteoblast differentiation from bone marrow cells after (39.3 2.1 of ALP-positive colonies in mice injected with 20 µ g LPS/g mice vs 76.7 10.8 in control mice, p=0.009, t-test). At the same time the number of TRAP-positive osteoclast-like cells was increased in LPS-injected mice compared with the controls (22.6 6.2 of TRAP-positive osteoclasts in mice injected with 20 µ g LPS/g mice vs 3.2 0.75 in control mice, p= 0.001, t-test). Our preliminary results indicate that LPS-injection in vivo induced increase in osteoclast differentiation and inhibition in osteoblast differentiation from bone marrow cells ex vivo. Our further aim is to investigate intracellular mechanisms by which LPS affects bone cell differentiation and activity.

osteoblastogenesis; osteoclastogenesis; lipopolysaccharide

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