Objective-We have previously shown the simultaneous generation of CD73+ mesenchymal stromal cells (MSCs) along with CD34+ hematopoietic cells from human embryonic stem cells (ESCs) when they are co-cultured with OP9 murine stromal cells. We investigated whether MSCs can be derived from human ESCs without co-culturing with OP9 cells, and if such cells exhibit immunological properties similar to MSCs derived from adult human bone marrow (BM).Materials and Methods-Our starting populations were undifferentiated ESCs cultured on matrigel-coated plates without feeder cells. The differentiated fibroblast-looking cells were tested for expression of MSC markers and their potential for multi-lineage differentiation. We investigated surface expression of HLA molecules on these MSCs before and after treatment with interferon gamma (IFN-γ). We also tested the proliferative response of T-lymphocytes towards MSCs and the effects of MSCs in mixed lymphocyte reaction (MLR) assays. Conclusions-MSCs can be derived from human ESCs without feeder cells. These human ESCderived MSCs have cell surface markers, differentiation potentials, and immunological properties in vitro that are similar to adult BM-derived MSCs. Results-We

BackgroundComponents of the microenvironment such as bone marrow stromal cells (BMSCs) are well known to support multiple myeloma (MM) disease progression and resistance to chemotherapy including the proteasome inhibitor bortezomib. However, functional distinctions between BMSCs in MM patients and those in disease-free marrow are not completely understood. We and other investigators have recently reported that NF-κB activity in primary MM cells is largely resistant to the proteasome inhibitor bortezomib, and that further enhancement of NF-κB by BMSCs is similarly resistant to bortezomib and may mediate resistance to this therapy. The mediating factor(s) of this bortezomib-resistant NF-κB activity is induced by BMSCs is not currently understood.ResultsHere we report that BMSCs specifically derived from MM patients are capable of further activating bortezomib-resistant NF-κB activity in MM cells. This induced activity is mediated by soluble proteinaceous factors secreted by MM BMSCs. Among the multiple factors evaluated, interleukin-8 was secreted by BMSCs from MM patients at significantly higher levels compared to those from non-MM sources, and we found that IL-8 contributes to BMSC-induced NF-κB activity.ConclusionsBMSCs from MM patients uniquely enhance constitutive NF-κB activity in MM cells via a proteinaceous secreted factor in part in conjunction with IL-8. Since NF-κB is known to potentiate MM cell survival and confer resistance to drugs including bortezomib, further identification of the NF-κB activating factors produced specifically by MM-derived BMSCs may provide a novel biomarker and/or drug target for the treatment of this commonly fatal disease.

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Introduction Mesenchymal stromal/stem cells (MSCs) have been used in a wide variety of preclinical experiments and in an increasing number of human clinical trials. Although many of these studies have shown different levels of engraftment, the exact fate of MSCs after transplantation and the tissue response to their engraftment has not been investigated in detail. In the present work we studied the distribution of human MSCs in a rat hind limb ischemic injury model immediately after transplantation and also analyzed the recipient tissue response to transplanted cells. Methods We tracked the in vivo fate of the transplanted MSCs utilizing bioluminescence imaging, fluorescence microscopy, and gene/protein expression analysis in rat hind limb ischemia model. We also monitored the viability of transplanted cells by graft vs. recipient expression analysis and determined the angiogenic and proliferative effect of transplantation by histological staining. Results According to imaging analysis only a small portion of cells persisted for extended period of time at the site of injury. Interestingly, recipient versus graft expression studies showed increased synthesis of rat-origin angiogenic factors and no human-origin mRNA or protein synthesis in transplanted tissues. More importantly, despite the lack of robust engraftment or growth factor secretion the transplantation procedure exerted a significant pro-angiogenic and pro-proliferative effect, which we showed was mediated by angiogenic and mitogenic signaling pathways. Discussion Our results show an immediate temporal tissue effect in response to MSC transplantation that may represent a novel indirect paracrine mechanism for the beneficial effects of cell transplantation observed in injured tissues.

The Tat protein is essential for HIV type 1 (HIV-1) replication and may be an important virulence factor in vivo. We studied the role of Tat in viral pathogenesis by immunizing rhesus macaques with chemically inactivated Tat toxoid and challenging these animals by intrarectal inoculation with the simian͞human immunodeficiency virus 89.6PD. Immune animals had significantly attenuated disease with lowered viral RNA, interferon-␣, and chemokine receptor expression (CXCR4 and CCR5) on CD4 ؉ T cells; these features of infection have been linked to in vitro effects of Tat and respond similarly to extracellular Tat protein produced during infection. Immunization with Tat toxoid inhibits key steps in viral pathogenesis and should be included in therapeutic or preventive HIV-1 vaccines.

Intrarectal simian immunodeficiency virus (SIV) infection in rhesus macaques is a model for sexual transmission of primate retroviruses. Phylogenetic studies on envelope gene sequences that were present in blood following intrarectal SIV inoculation provided evidence for selective amplification of a subset of viruses present in the inoculum and defined one amino acid sequence uniquely associated with intrarectal infection. Both persistent and transient viremia states were observed after intrarectal infection. Immune responses in persistently infected animals accounted for slower rates of disease progression despite the presence of highly pathogenic viruses that were documented by transfusion studies. Transient viremia elicited protective immunity against subsequent intrarectal virus challenge but did not protect against intravenous virus challenge. Transient viremia usually but not always led to self-limiting infection. In one animal, we documented a relapse to active viremia long after the initial transient viremia. SIV transmission across mucosal barriers affects pathogenesis in the short term by limiting the types of viruses established in the host and in the longer term by establishing host responses that slow disease progression despite the presence of highly pathogenic viruses in blood.