Umbilical cord-derived mesenchymal stem cells instruct dendritic cells to acquire tolerogenic phenotypes through the IL-6-mediated upregulation of SOCS1

Hepatic carcinoma-associated fibroblasts induce IDO-producing regulatory dendritic cells through IL-6-mediated STAT3 activation

Although carcinoma-associated fibroblasts (CAFs) in tumor microenvironments have a critical role in immune cell modulation, their effects on the generation of regulatory dendritic cells (DCs) are still unclear. In this study, we initially show that CAFs derived from hepatocellular carcinoma (HCC) tumors facilitate the generation of regulatory DCs, which are characterized by low expression of costimulatory molecules, high suppressive cytokines production and enhanced regulation of immune responses, including T-cell proliferation impairment and promotion of regulatory T-cell (Treg) expansion via indoleamine 2,3-dioxygenase (IDO) upregulation. Our findings also indicate that STAT3 activation in DCs, as mediated by CAF-derived interleukin (IL)-6, is essential to IDO production. Moreover, IDO inhibitor, STAT3 and IL-6 blocking antibodies can reverse this hepatic CAF-DC regulatory function. Therefore, our results provide new insights into the mechanisms by which CAFs induce tumor immune escape as well as a novel cancer immunotherapeutic approach (for example, targeting CAFs, IDO or IL-6).

Mesenchymal stromal cells and immunomodulation: A gathering of regulatory immune cells

Because of their well-recognized immunomodulatory properties, mesenchymal stromal cells (MSCs) represent an attractive cell population for therapeutic purposes. In particular, there is growing interest in the use of MSCs as cellular immunotherapeutics for tolerance induction in allogeneic transplantations and the treatment of autoimmune diseases. However, multiple mechanisms have been identified to mediate the immunomodulatory effects of MSCs, sometimes with several ambiguities and inconsistencies. Although published studies have mainly reported the role of soluble factors, we believe that a sizeable cellular component plays a critical role in MSC immunomodulation. We refer to these cells as regulatory immune cells, which are generated from both the innate and adaptive responses after co-culture with MSCs. In this review, we discuss the nature and role of these immune regulatory cells as well as the role of different mediators, and, in particular, regulatory immune cell induction by MSCs through interleukin-10. Once induced, immune regulatory cells accumulate and converge their regulatory pathways to create a tolerogenic environment conducive for immunomodulation. Thus, a better understanding of these regulatory immune cells, in terms of how they can be optimally manipulated and induced, would be suitable for improving MSC-based immunomodulatory therapeutic strategies.

Immunogenicity of allogeneic mesenchymal stromal cells: what has been seen in vitro and in vivo?

Mesenchymal stromal cells (MSC) are promising candidates for supporting regeneration and suppressing undesired immune reactivity. Although autologous MSC have been most commonly used for clinical trials, data on application of allogeneic MHC-unmatched MSC were reported. The usage of MSC as an 'off-the-shelf' product would have several advantages; however, it is an immunological challenge. The preclinical studies on the (non)immunogenicity of MSC are contradictory and, unfortunately, solid data from clinical trials are missing. Induction of an alloresponse would be a major limitation for the application of allogeneic MSC. Here we discuss the key elements for the induction of an alloresponse and targets of immunomodulation by MSC as well as preclinical and clinical hints on allo(non)response to MSC.

MiR-30a attenuates immunosuppressive functions of IL-1β-elicited mesenchymal stem cells via targeting TAB3

Mesenchymal stem cells (MSCs) possess the ability to modulate the immune response, and their abnormalities are related to several diseases. We previously reported that miR-30a expression significantly increased in the maternal-fetal interface during preeclampsia (PE), but the effects of miR-30a on the immunoregulatory characteristics of MSCs are unclear. In this study, we determined that miR-30a over-expression inhibited the IL-1β-elicited activation of the nuclear factor κB (NF-κB) and JNK signaling pathways and the production of IL-6, cyclooxygenase 2 (COX2) and IL-8 by targeting transforming growth factor-β-activated kinase 1 binding protein 3 (TAB3) in MSCs. Moreover, the over-expression of miR-30a also impaired MSCs' anti-inflammatory effects on macrophages. These data demonstrated that miR-30a in MSCs may participate in the immune dysregulation of the maternal-fetal interface during PE.

Jagged-2 enhances immunomodulatory activity in adipose derived mesenchymal stem cells

Adipose derived Mesenchymal stem cells (AMSCs) are able to expand in vitro and undergo differentiation into multiple cell lineages, yet have low immunogenicity while exhibiting several immunoregulatory characteristics. We sought to investigate the immunomodulatory mechanisms of AMSCs to better understand their immunogenic properties. Following 10 days of chondrogenic differentiation or 48 hours of IFN-γ pretreatment, AMSCs retained low level immunogenicity but prominent immunoregulatory activity and AMSC immunogenicity was enhanced by chondrogenic differentiation or IFN-γ treatment. We found Jagged-2 expression was significantly elevated following chondrogenic differentiation or IFN-γ pretreatment. Jagged-2-RNA interference experiments suggested that Jagged-2-siRNA2 suppresses Jagged-2 expression during chondrogenic differentiation and in IFN-γ pretreated AMSCs. Besides, Jagged-2 interference attenuated immunosuppressive activity by mixed lymphocyte culture and mitogen stimulation experiments. So, the immunoregulatory activity of AMSCs, to some extent dependent upon Jagged-2, might be stronger after multilineage differentiation or influence from inflammatory factors. This may also be why rejection does not occur after allogeneic AMSCs differentiate into committed cells.

Mesenchymal stromal cells and chronic inflammatory bowel disease

Recent experimental findings have shown the ability of mesenchymal stromal cells (MSCs) to home to damaged tissues and to produce paracrine factors with anti-inflammatory properties, potentially resulting in reduction of inflammation and functional recovery of the damaged tissues. Prompted by these intriguing properties and on the basis of encouraging preclinical data, MSCs are currently being studied in several immune-mediated disorders. Inflammatory bowel diseases (IBD) represent a setting in which MSCs-based therapy has been extensively investigated. Phase I and II studies have documented the safety and feasibility of MSCs. However, efficacy results have so far been conflicting. In this review, we will discuss the biologic rationale that makes MSCs a promising therapeutic tool for IBD, and analyze recent experimental and clinical findings, highlighting current limitations and future perspectives of MSCs-related immunotherapy for IBD.

Umbilical cord-derived multipotent mesenchymal stromal cells: biological properties and clinical applications

The article presents the current literature evidence and own data on the origin and properties of human umbilical cord-derived multipotent mesenchymal stromal cells including proliferative potential, plasticity, stability of caryotype and phenotype, and immunomodulatory activity A review of clinical trials using this cell type is performed Prospects for the use of multipotent stromal cells, derived from umbilical cord, in cell transplantation associate with the need for specialized biobanking and transplant standardization criteria

The endometrium as a source of mesenchymal stem cells for regenerative medicine

Stem cell therapies have opened new frontiers in medicine with the possibility of regenerating lost or damaged cells. Embryonic stem cells, induced pluripotent stem cells, hematopoietic stem cells, and mesenchymal stem cells have been used to derive mature cell types for tissue regeneration and repair. However, the endometrium has emerged as an attractive, novel source of adult stem cells that are easily accessed and demonstrate remarkable differentiation capacity. In this review, we summarize our current understanding of endometrial stem cells and their therapeutic potential in regenerative medicine.

Interactions between MSCs and immune cells: implications for bone healing

It is estimated that, of the 7.9 million fractures sustained in the United States each year, 5% to 20% result in delayed or impaired healing requiring therapeutic intervention. Following fracture injury, there is an initial inflammatory response that plays a crucial role in bone healing; however, prolonged inflammation is inhibitory for fracture repair. The precise spatial and temporal impact of immune cells and their cytokines on fracture healing remains obscure. Some cytokines are reported to be proosteogenic while others inhibit bone healing. Cell-based therapy utilizing mesenchymal stromal cells (MSCs) is an attractive option for augmenting the fracture repair process. Osteoprogenitor MSCs not only differentiate into bone, but they also exert modulatory effects on immune cells via a variety of mechanisms. In this paper, we review the current literature on both in vitro and in vivo studies on the role of the immune system in fracture repair, the use of MSCs in the enhancement of fracture healing, and interactions between MSCs and immune cells. Insight into this paradigm can provide valuable clues in identifying cellular and noncellular targets that can potentially be modulated to enhance both natural bone healing and bone repair augmented by the exogenous addition of MSCs.

Plasticity of mesenchymal stem cells in immunomodulation: pathological and therapeutic implications

Mesenchymal stem cells (MSCs) are multipotent stromal cells that exist in many tissues and are capable of differentiating into several different cell types. Exogenously administered MSCs migrate to damaged tissue sites, where they participate in tissue repair. Their communication with the inflammatory microenvironment is an essential part of this process. In recent years, much has been learned about the cellular and molecular mechanisms of the interaction between MSCs and various participants in inflammation. Depending on their type and intensity, inflammatory stimuli confer on MSCs the ability to suppress the immune response in some cases or to enhance it in others. Here we review the current findings on the immunoregulatory plasticity of MSCs in disease pathogenesis and therapy.