Human osteoclastogenesis in Epstein-Barr virus-induced erosive arthritis in humanized NOD/Shi-scid/IL-2Rγnull mice.

Many human viruses, including Epstein-Barr virus (EBV), do not infect mice, which is challenging for biomedical research. We have previously reported that EBV infection induces erosive arthritis, which histologically resembles rheumatoid arthritis, in humanized NOD/Shi-scid/IL-2Rγnull (hu-NOG) mice; however, the underlying mechanisms are not known. Osteoclast-like multinucleated cells were observed during bone erosion in this mouse model, and therefore, we aimed to determine whether the human or mouse immune system activated bone erosion and analyzed the characteristics and origin of the multinucleated cells in hu-NOG mice. Sections of the mice knee joint tissues were immunostained with anti-human antibodies against certain osteoclast markers, including cathepsin K and matrix metalloproteinase-9 (MMP-9). Multinucleated cells observed during bone erosion stained positively for human cathepsin K and MMP-9. These results indicate that human osteoclasts primarily induce erosive arthritis during EBV infections. Human osteoclast development from hematopoietic stem cells transplanted in hu-NOG mice remains unclear. To confirm their differentiation potential into human osteoclasts, we cultured bone marrow cells of EBV-infected hu-NOG mice and analyzed their characteristics. Multinucleated cells cultured from the bone marrow cells stained positive for human cathepsin K and human MMP-9, indicating that bone marrow cells of hu-NOG mice could differentiate from human osteoclast progenitor cells into human osteoclasts. These results indicate that the human immune response to EBV infection may induce human osteoclast activation and cause erosive arthritis in this mouse model. Moreover, this study is the first, to our knowledge, to demonstrate human osteoclastogenesis in humanized mice. We consider that this model is useful for studying associations of EBV infections with rheumatoid arthritis and human bone metabolism.

Lactobacillus johnsonii supplementation attenuates respiratory viral infection via metabolic reprogramming and immune cell modulation.

Regulation of respiratory mucosal immunity by microbial-derived metabolites has been a proposed mechanism that may provide airway protection. Here we examine the effect of oral Lactobacillus johnsonii supplementation on metabolic and immune response dynamics during respiratory syncytial virus (RSV) infection. L. johnsonii supplementation reduced airway T helper type 2 cytokines and dendritic cell (DC) function, increased regulatory T cells, and was associated with a reprogrammed circulating metabolic environment, including docosahexanoic acid (DHA) enrichment. RSV-infected bone marrow-derived DCs (BMDCs) from L. johnsonii-supplemented mice had altered cytokine secretion, reduced expression of co-stimulatory molecules, and modified CD4+ T-cell cytokines. This was replicated upon co-incubation of wild-type BMDCs with either plasma from L. johnsonii-supplemented mice or DHA. Finally, airway transfer of BMDCs from L. johnsonii-supplemented mice or with wild-type derived BMDCs pretreated with plasma from L. johnsonii-supplemented mice reduced airway pathological responses to infection in recipient animals. Thus L. johnsonii supplementation mediates airway mucosal protection via immunomodulatory metabolites and altered immune function.

Comparison of growth and differentiation of fetal and adult rhesus monkey mesenchymal stem cells.

The goal of this study was to compare the growth and differentiation potential of fetal and adult rhesus monkey (Macaca mulatta) mesenchymal stem cells (rhMSCs). rhMSCs were obtained from healthy early third-trimester fetal (n = 3) and adult (n = 3) rhesus monkey bone marrow. Fetal rhMSCs were plated at 10, 50, 100, or 1,000 cells/cm(2) in medium containing 10% or 20% infant monkey serum (IMS) or fetal bovine serum (FBS). Fetal rhMSCs grown at 1,000 cells/cm(2) in 20% FBS showed faster growth rates and differentiation toward adipogenic, chondrogenic, and osteogenic lineages when compared to other culture conditions and to adult cells (p < 0.05). Fetal rhMSC showed higher population doubling times (11.3 +/- 0.5) when compared to adult cells (7.3 +/- 0.8) during the first three passages. Adult rhMSC did not grow beyond the third passage under all culture conditions, including those supplemented with insulin-like growth factor (IGF)-I, IGF-II, platelet-derived growth factor (PDGF), and fibroblast growth factor-2 (FGF-2). After the third passage, adult rhMSC cultures were observed with large syncytia and with evidence of apoptosis. Cells obtained from these cultures tested positive for simian foamy virus (SFV) by PCR, RT-PCR, and immunofluorescent assay. Adult rhMSCs cultured with 10 microM tenofovir, an antiviral agent, showed normal growth and differentiation for over 20 population doublings. These findings suggest that: (1) fetal rhMSCs possess greater self-renewal and differentiation potential when compared to adult cells; and (2) SFV can inhibit proliferation of adult rhMSCs in culture, whereas the addition of tenofovir can successfully suppress SFV replication in vitro and result in resumed growth.