Induction of IL-6 production by bone marrow stromal cells on the adhesion of IL-6-dependent hematopoietic cells

Differences in Tumor Microenvironment Dictate T Helper Lineage Polarization and Response to Immune Checkpoint Therapy

Immune checkpoint therapy (ICT) shows encouraging results in a subset of patients with metastatic castration-resistant prostate cancer (mCRPC) but still elicits a sub-optimal response among those with bone metastases. Analysis of patients' bone marrow samples revealed increased T_h17 instead of T_h1 subsets after ICT. To further evaluate the different tumor microenvironments, we injected mice with prostate tumor cells either subcutaneously or intraosseously. ICT in the subcutaneous CRPC model significantly increases intra-tumoral T_h1 subsets and improves survival. However, ICT fails to elicit an anti-tumor response in the bone CRPC model despite an increase in the intra-tumoral CD4 T cells, which are polarized to T_h17 rather than T_h1 lineage. Mechanistically, tumors in the bone promote osteoclast-mediated bone resorption that releases TGF-β, which restrains T_h1 lineage development. Blocking TGF-β along with ICT increases T_h1 subsets and promotes clonal expansion of CD8 T cells and subsequent regression of bone CRPC and improves survival.

Bone-healing capacity of conditioned medium derived from three-dimensionally cultivated human mesenchymal stem cells and electrical stimulation on collagen sponge

Continuing from our previous study, we hypothesized that combining electrical stimulation (ES) and three-dimensional (3D) culture would be a useful strategy to obtain more bioactive factors in conditioned medium (CM) derived from human mesenchymal stem cells (hMSC). Our aim in this study was to investigate the bone-healing capacity of CM derived from hMSC after 4 days of culture on a collagen sponge-exposed (CM-ES) or unexposed (CM-control; CM-CON) to ES in comparison with that of hMSC implantation. A cytokine assay of both CMs revealed the presence of cytokines, growth factors, and trophic factors. In vitro evaluation of both CMs showed increased cell growth and alkaline phosphatase activity of the hMSC, with little difference between CMs. We investigated the bone-healing effect using two bone disease models: bone defect and inflammatory bone loss. The calvaria defect was implanted with whole CM or 3D-precultured hMSC unexposed to ES. Microcomputed tomography analysis after 4 weeks indicated a twofold greater bone volume in the CM-CON and CM-ES groups than in the hMSC and vehicle groups, though we found no difference between the CM groups. However, CM-ES enhanced the bone healing of interleukin-1-induced bone loss to a level comparable with hMSC, whereas CM-CON did not. These results show that 3D-cultured CM had a greater or similar capacity for bone healing as treatment using hMSC transplantation, and CM-ES was especially effective against inflammatory bone loss. Thus, 3D-cultured CM with or without ES presents an encouraging alternative to MSC-based bone healing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 311-320, 2018.

Juxtacrine interaction of macrophages and bone marrow stromal cells induce interleukin-6 signals and promote cell migration

The bone marrow contains a heterogeneous milieu of cells, including macrophages, which are key cellular mediators for resolving infection and inflammation. Macrophages are most well known for their ability to phagocytose foreign bodies or apoptotic cells to maintain homeostasis; however, little is known about their function in the bone microenvironment. In the current study, we investigated the in vitro interaction of murine macrophages and bone marrow stromal cells (BMSCs), with focus on the juxtacrine induction of IL-6 signaling and the resultant effect on BMSC migration and growth. The juxtacrine interaction of primary mouse macrophages and BMSCs activated IL-6 signaling in the co-cultures, which subsequently enhanced BMSC migration and increased BMSC numbers. BMSCs and macrophages harvested from IL-6 knockout mice revealed that IL-6 signaling was essential for enhancement of BMSC migration and increased BMSC numbers via juxtacrine interactions. BMSCs were the main contributor of IL-6 signaling, and hence activation of the IL-6/gp130/STAT3 pathway. Meanwhile, macrophage derived IL-6 remained important for the overall production of IL-6 protein in the co-cultures. Taken together, these findings show the function of macrophages as co-inducers of migration and growth of BMSCs, which could directly influence bone formation and turnover.

Ameloblastin promotes bone growth by enhancing proliferation of progenitor cells and by stimulating immunoregulators

In this study, we examined the role of the enamel matrix protein, ameloblastin, in bone growth and remodelling, and attempted to identify some of the molecular mechanisms involved in these processes. The effects of recombinant ameloblastin (rAmbn) were tested in vivo in rats, and in vitro in primary human mesenchymal stem cells, osteoblasts, chondrocytes, and osteoclasts. We used a microarray technique to identify genes that were regulated in human osteoblasts and verified our findings using multiplex protein analysis and real-time RT-PCR. Recombinant ameloblastin was found to stimulate bone healing in vivo, and to enhance the proliferation of mesenchymal stem cells and osteoblasts, as well as the differentiation of osteoclast precursor cells in vitro. The most profound effect was on the regulation of genes related to immune responses as well as on the expression of cytokines and markers of bone cell differentiation, indicating that ameloblastin has an effect on mesenchymal cell differentiation. A receptor has not yet been identified, but we found rAmbn to induce, directly and indirectly, signal transducer and activator of transcription (STAT) 1 and 2 and downstream factors in the interferon pathway.

Interleukin-6 maintains bone marrow-derived mesenchymal stem cell stemness by an ERK1/2-dependent mechanism

Adult human mesenchymal stem cells (MSCs) hold promise for an increasing list of therapeutic uses due to their ease of isolation, expansion, and multi-lineage differentiation potential. To maximize the clinical potential of MSCs, the underlying mechanisms by which MSC functionality is controlled must be understood. We have taken a deconstructive approach to understand the individual components in vitro, namely the role of candidate "stemness" genes. Our recent microarray gene expression profiling data suggest that interleukin-6 (IL-6) may contribute to the maintenance of MSCs in their undifferentiated state. In this study, we showed that IL-6 gene expression is significantly higher in undifferentiated MSCs as compared to their chondrogenic, osteogenic, and adipogenic derivatives. Moreover, we found that MSCs secrete copious amounts of IL-6 protein, which decreases dramatically during osteogenic differentiation. We further evaluated the role of IL-6 for maintenance of MSC "stemness," using a series of functional assays. The data showed that IL-6 is both necessary and sufficient for enhanced MSC proliferation, protects MSCs from apoptosis, inhibits adipogenic and chondrogenic differentiation of MSCs, and increases the rate of in vitro wound healing of MSCs. We further identified ERK1/2 activation as the key pathway through which IL-6 regulates both MSC proliferation and inhibition of differentiation. Taken together, these findings show for the first time that IL-6 maintains the proliferative and undifferentiated state of bone marrow-derived MSCs, an important parameter for the optimization of both in vitro and in vivo manipulation of MSCs.

Interleukin-6 deficiency affects bone marrow stromal precursors, resulting in defective hematopoietic support

Interleukin-6 (IL-6) is a critical factor in the regulation of stromal function and hematopoiesis. In vivo bromodeoxyuridine incorporation analysis indicates that the percentage of Lin(-)Sca-1(+) hematopoietic progenitors undergoing DNA synthesis is diminished in IL-6-deficient (IL-6(-/-)) bone marrow (BM) compared with wild-type BM. Reduced proliferation of IL-6(-/-) BM progenitors is also observed in IL-6(-/-) long-term BM cultures, which show defective hematopoietic support as measured by production of total cells, granulocyte macrophage-colony-forming units (CFU-GMs), and erythroid burst-forming units (BFU-Es). Seeding experiments of wild-type and IL-6(-/-) BM cells on irradiated wild-type or IL-6-deficient stroma indicate that the hematopoietic defect can be attributed to the stromal and not to the hematopoietic component. In IL-6(-/-) BM, stromal mesenchymal precursors, fibroblast CFUs (CFU-Fs), and stroma-initiating cells (SICs) are reduced to almost 50% of the wild-type BM value. Moreover, IL-6(-/-) stromata show increased CD34 and CD49e expression and reduced expression of the membrane antigens vascular cell adhesion molecule-1 (VCAM-1), Sca-1, CD49f, and Thy1. These data strongly suggest that IL-6 is an in vivo growth factor for mesenchymal precursors, which are in part implicated in the reduced longevity of the long-term repopulating stem cell compartment of IL-6(-/-) mice.

3D culture of murine hematopoietic cells with spatial development of stromal cells in nonwoven fabrics

BACKGROUND

The in vivo hematopoietic microenvironment is composed of stromal cells and extracellular matrix in a 3D configuration. We have created a 3D microenvironment in vitro, employing spatial development of stromal cells in a nonwoven fabric porous carrier, Fibra-cel (FC). We compared its performance with that of a 2D microenvironment.

METHODS

Primary murine BM cells were inoculated on the layers of stromal cells prepared in FC (3D) or on a dish (2D) and cultured for 7-21 days. The hematopoietic cells harvested from the cultures were evaluated by colony-forming unit (CFU) assay and transplantation to sub lethally irradiated mice.

RESULTS

The maximum stromal cell concentration in the 2D culture was higher than that in the 3D culture. However, the hematopoietic cell concentration in the 3D culture was kept at a higher level than that in the 2D culture. The number of CFU-mix increased five times during 3D cultivation, but decreased in the 2D culture. The engraftment percentage of 3D cultured cells was comparable with that of fresh cells, and markedly higher than that of 2D cultured cells.

DISCUSSION

The 3D culture constructed with FC and stromal cells was clearly superior to 2D culture because hematopoietic progenitor cells were expanded without the addition of cytokines and the content of hematopoietic stem cells was maintained.

Rapid and efficient generation of lentivirally gene-modified dendritic cells from DC progenitors with bone marrow stromal cells

Since dendritic cells (DC) play pivotal roles in both innate and adaptive immunity, DC can be a good target for immuno-gene therapy. However, the optimal generation method for gene-modified DC has not yet been well exploited. CD34+ cells from cord blood (CB), bone marrow (BM), or peripheral blood (PB) were expanded in a medium containing stem cell factor (SCF), flt 3 ligand (Flt3L) and thrombopoietin (TPO) with or without HESS-5, a murine BM stromal cell line, for 2 weeks (the first expansion step), then differentiated to DC in a medium containing granulocyte-macrophage colony-stimulating factor (GM-CSF), flt 3 ligand (Flt3L), stem cell factor (SCF), tumor necrosis factor-alpha (TNF-alpha), IL-4, and lipopolysaccharide (LPS) for 9 days (the second differentiation step). DC progenitors were transduced with human immunodeficiency virus (HIV) vectors at different time points during the second step. Use of HESS-5 during the first step resulted in more DC generation than without it (cell expansion: CB, 10,461 vs. 354-fold; BM, 962 vs. 225-fold; peripheral blood mononuclear cell (PBMC), 8,506 vs. 240-fold; %DC: CB, 83.4% vs. 76.9%; BM, 83.6 vs. 69.8%; PBMC, 85.9 vs. 60.5%). Gene transduction to the in vitro expanded DC progenitors at day 3 during the second step, resulted in better final yield of the gene-modified DC than that to those at day 0 or day 6 (as much as 44% of DC expressed green fluorescence protein (GFP) as a transgene) and the transduction efficiency correlated with endocytic ability and percent of S phase. DC transduced with an HIV vector encoding a melanoma antigen, MART-1, were adequately recognized by specific anti-MART-1 CTL. The two-step culture method with HESS-5 is useful for rapid expansion of DC progenitors and subsequent lentiviral gene transduction to DC.

Gp130 activation by soluble interleukin-6 receptor/interleukin-6 enhances osteoblastic differentiation of human bone marrow-derived mesenchymal stem cells

Interleukin-6 (IL-6) promotes osteodifferentiation in bone-located progenitors; however, it is not known whether this cytokine affects the differentiation of bone marrow-located osteoprogenitors. To address this issue, we prepared human bone marrow-derived mesenchymal stem cells (MSCs), which were characterized by a cell surface phenotype and multipotential nature. It was observed that in the presence of IL-6, MSCs were not differentiated into the osteogenic lineage, as evidenced by a failure to induce alkaline phosphatase activity, an earlier marker of osteodifferentiation. The lack of effect of IL-6 correlates with the observation that MSCs do not express a membrane-bound or soluble IL-6 receptor (sIL-6R). The incompetence of IL-6 was not reversed by the addition of sIL-6R alone or the sIL-6R/IL-6 complex, as it occurs in other IL-6R-negative cells. However, after MSC osteocommittment by dexamethasone, sIL-6R or the sIL-6R/IL-6 complex enhanced alkaline phosphatase activity. The effect of sIL-6R or sIL-6R/IL-6 proved to be dependent on gp130 availability, which is expressed by MSCs, and involves stat-3 phosphorylation. These data suggest that IL-6R deficiency may represent for bone marrow-located mesenchymal progenitors a sort of protective mechanism to escape the osteogenic effect of IL-6, which is produced by the MSC itself as well as by other marrow stromal cells.

Major histocompatibility complex restriction between hematopoietic stem cells and stromal cells in vitro

We have previously found that a significant number of hematopoietic progenitors accumulate in engrafted bones with the same major histocompatibility complex (MHC) as the transplanted bone marrow cells. In the present study, to further clarify the MHC restriction between hematopoietic stem cells (HSC) and microenvironment, we carried out cobblestone colony formation assays by culturing HSCs with MHC-matched or -mismatched stromal cell monolayers. The formation of cobblestone colonies under MHC-mismatched stromal cells significantly decreased in comparison with MHC-matched stromal cells. However, the decrease in cobblestone colony formation under MHC-mismatched stromal cells was not significant when using MHC class I-deficient HSC or stromal cells. Taken together with the results using B10 congenic strains, it is suggested that the MHC preference is restricted by MHC class Ia molecules. Treatment with monoclonal antibodies (mAbs) against MHC class Ia molecules of stromal cell phenotypes significantly enhanced the cobblestone colony formation, whereas treatment with mAbs against HSC phenotypes significantly inhibited it. The expression of cytokines to promote hematopoiesis was enhanced by the mAbs against stromal cell phenotypes. The enhancement of cytokine expression was also observed when stromal cells and HSCs were MHC-matched. These results suggest that signaling via the MHC molecules augments stromal cell activity and elicits the MHC restriction.

Identification and characterization of rat AILIM/ICOS, a novel T-cell costimulatory molecule, related to the CD28/CTLA4 family

Activation-inducible lymphocyte immuno-mediatory molecule (AILIM) is an inducible cell surface glycoprotein expressed on thymocytes and activated lymphocytes. Specific monoclonal antibody to rat AILIM induced the cell aggregation of a rat thymoma cell line and ConA-activated splenocytes. In the present study, we identified the primary structure of two species of rat AILIM by expression cloning. We also cloned mouse and human AILIM homologues and the predicted amino acid sequences were identical to those of the inducible costimulator ICOS/CRP-1, which belongs to the CD28/CTLA4 family. Although the human and mouse AILIM/ICOS molecule is localized on T-cells, the major population of AILIM/ICOS-positive cells in rat splenocyte was CD45RA-positive B-cells. The expression level of AILIM/ICOS on T-cells was relatively low; however, its expression was drastically induced by the treatment with PMA plus Ca-ionophore or the engagement of CD3 and these costimulatory molecules. Almost all T-cells exhibited potency as to its expression. Functional analysis of AILIM/ICOS demonstrated that AILIM-mediated costimulation was relatively weak compared to that of human.

Pattern of cytokine expression by rat liver epithelial cells supporting long-term culture of human CD34(+)umbilical cord blood cells

Fetal liver is the main site of haematopoiesis during mid-gestation. The adult liver still provides a favourable environment for extramedullary haematopoiesis. Nevertheless, regulation of liver haematopoiesis by cell-cell contacts or by cytokines remains poorly understood. Recently, we have shown that rat liver epithelial cells (RLECs) support long-term survival and multilineage differentiation of adult human CD34(+)and CD34(+)/CD38(-)haematopoietic cells obtained from granulocyte-colony stimulating factor mobilized peripheral blood and from bone marrow respectively. In addition, the importance of physical proximity between haematopoietic cells and RLECs was clearly demonstrated. Here, our findings give evidence that RLECs belonging to the epithelial but non-parenchymal liver compartment also sustain the long-term production of progenitors from human CD34(+)umbilical cord blood cells. Moreover, to better analyse the regulation of haematopoiesis in this RLEC coculture model, we have investigated the cytokine expression by RLECs alone and by RLECs coming from coculture with CD34(+)cells from umbilical cord blood. We demonstrated that a broad spectrum of cytokines acting at different stages of haematopoiesis is produced by RLECs. Interestingly, an upregulation of leukemia inhibitory factor expression by RLECs in presence of CD34(+)haematopoietic cells was observed. These data suggest an important role of cell-cell interactions in the regulation of haematopoiesis.

A murine stromal cell line promotes the expansion of CD34high+-primitive progenitor cells isolated from human umbilical cord blood in combination with human cytokines

The in vitro expansion of CD34+ cells is important for clinical applications such as transplantation and gene therapy with CD34+ cells isolated from human umbilical cord blood. In the present study, we developed a xenogenic coculture system involving HUCB-CD34+ cells and a murine stromal cell line, HESS-5 cells, in the presence of recombinant human (rh) cytokines. We examined the effects of combinations of cytokines, such as rh-IL-3, rh-SCF, rh-granulocyte colony-stimulating factor (G-CSF), rh-granulocyte-macrophage-CSF and h-erythropoietin (EPO), on the expansion of CD34high+ cells and colony-forming progenitor cells (CFCs). The proliferation of CD34high+ cells and CFCs was dramatically promoted on coculture with HESS-5 cells, and the expansion ratio of the CD34high+ cells showed good correlation with that of high-proliferative potential colony-forming cells (HPP-CFCs). The most potent combination of cytokines in this xenogenic coculture system for the expansion of CD34high+ cells and HPP-CFCs was rh-IL-3 and rh-SCF. The proliferation of CD34high+ cells was supported in the presence of HESS-5 cells with direct cell contact, but not observed in the indirect coculture involving a microporous membrane. Furthermore, we developed a unique coculture method, designated as the bilayer coculture method, involving CD34+ cells and HESS-5 cells using a microporous membrane. This expansion system will be applicable to the expansion of the primitive progenitor cells of HUCB-CD34+ cells and is worthy of consideration for the clinical application of HUCB-CD34+ cells.

Integrin β2 (CD18)-Mediated Cell Proliferation of HEL Cells on a Hematopoietic-Supportive Bone Marrow Stromal Cell Line, HESS-5 Cells

Cellular interactions between hematopoietic cells and stromal cells play important roles in the proliferation and differentiation of hematopoietic cells. The proliferation of a human erythroleukemia cell line, HEL cells, which can differentiate into macrophage- and megakaryocyte-like cells, and erythroid precursors was dramatically induced on coculture with a hematopoietic-supportive stromal cell line, HESS-5 cells, which can support long-term hematopoiesis in vitro without fetal bovine serum. HEL cells proliferated when they were cocultured with but not without direct cell contact. Because the coculture supernatants with direct cell contact and cytokines such as interleukins and growth factors did not exhibit growth-stimulating activity toward HEL cells, it was suggested that some molecule that has growth-stimulating activity exists on the surface of the cells. Extracellular matrix components such as fibronectin, laminin, vitronectin, and collagen did not affect the proliferation of HEL cells. An anti-CD18 monoclonal antibody, which recognizes the common β chain of the β2 integrin subfamily, induced dramatic proliferation of HEL cells. Moreover, the proliferation of HEL cells was inhibited by an antisense oligonucleotide of CD18 mRNA. As judged from these observations, the proliferation of HEL cells was mediated by CD18 molecules expressed on HEL cells. On the contrary, the common counter-receptor of the β2 integrin subfamily, intercellular adhesion molecule-1, which is expressed on CHO-K1 cells, did not stimulate the growth of HEL cells. It is known that other counter molecules of the β2 integrin subfamily, such as complement C3bi and fibrinogen, are not produced by stromal cells. These findings suggest that the proliferation of HEL cells may be induced through an interaction between a novel molecule of the β2 integrin subfamily on HEL cells and the counter-receptor on HESS-5 cells. The β2 integrin subfamily may regulate the growth of hematopoietic cells in hematopoiesis in vivo and/or cause the abnormal growth of leukemia cells.