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BACKGROUND: Mast cells are immune sentinels in the skin that respond to a wide range of pathological and environmental stimuli; they owe their function to the expression of Toll-like receptors (TLRs). We previously found that tonsil-derived mesenchymal stem cells (T-MSCs) were able to effectively attenuate TLR7-mediated skin inflammation in mice, which was accompanied by an increase in mast cell number. The present study investigated whether T-MSC extracellular vesicles, such as exosomes, are able to regulate mast cell activation in response to TLR7 stimulation. METHODS: The HMC-1 human mast cell line was treated with a TLR7 agonist in the presence or absence of T-MSC exosomes, and the levels of expressed inflammatory cytokines were assessed. Additionally, mice were repeatedly injected with a TLR7 agonist with or without interval treatments with T-MSC exosomes and assessed dermal distribution of mast cells and related immune cells. RESULTS: We showed that T-MSC exosomes containing microRNAs that target inflammatory cytokines significantly reduced the expression of inflammatory cytokines in TLR7 agonist-treated HMC-1 cells. In addition, T-MSC exosomes inhibited the increase in the number of both dermal mast cells and CD14-positive cells in TLR7 agonist-treated mice. CONCLUSION: Our data suggest that T-MSC exosomes have regulatory effects on mast cell activation under inflammatory conditions, including TLR7 stimulation.

Background Co-transplantation of bone marrow cells (BMCs) and mesenchymal stem cells (MSCs) is used as a strategy to improve the outcomes of bone marrow transplantation. Tonsil-derived MSCs (TMSCs) are a promising source of MSCs for co-transplantation. Previous studies have shown that TMSCs or conditioned media from TMSCs (TMSC-CM) enhance BMC engraftment. However, the factors in TMSCs that promote better engraftment have not yet been identified. Methods Mice were subjected to a myeloablative regimen of busulfan and cyclophosphamide, and the mRNA expression in the bone marrow was analyzed using an extracellular matrix (ECM) and adhesion molecule-targeted polymerase chain reaction (PCR) array. Nano-liquid chromatography with tandem mass spectrometry, real-time quantitative PCR, western blots, and enzyme-linked immunosorbent assays were used to compare the expression levels of metalloproteinase 3 (MMP3) in MSCs derived from various tissues, including the tonsils, bone marrow, adipose tissue, and umbilical cord. Recipient mice were conditioned with busulfan and cyclophosphamide, and BMCs, either as a sole population or with control or MMP3-knockdown TMSCs, were co-transplanted into these mice. The effects of TMSC-expressed MMP3 were investigated. Additionally, Enzchek collagenase and Transwell migration assays were used to confirm that the collagenase activity of TMSC-expressed MMP3 enhanced BMC migration. Results Mice subjected to the myeloablative regimen exhibited increased mRNA expression of collagen type IV alpha 1/2 (Col4a1 and Col4a2). Among the various extracellular matrix-modulating proteins secreted by TMSCs, MMP3 was expressed at higher levels in TMSCs than in other MSCs. Mice co-transplanted with BMCs and control TMSCs exhibited a higher survival rate, weight recovery, and bone marrow cellularity compared with mice co-transplanted with BMCs and MMP3-knockdown TMSCs. Control TMSC-CM possessed higher collagenase activity against collagen IV than MMP3-knockdown TMSC-CM. TMSC-CM also accelerated BMC migration by degrading collagen IV in vitro. Conclusions Collectively, these results indicate that TMSCs enhance BMC engraftment by the secretion of MMP3 for the modulation of the bone marrow extracellular matrix.

Located near the oropharynx, the tonsils are the primary mucosal immune organ. Tonsil tissue is a promising alternative source for the high-yield isolation of adult stem cells, and recent studies have reported the identification and isolation of tonsil-derived stem cells (T-SCs) from waste surgical tissue following tonsillectomies in relatively young donors (i.e., under 10 years old). As such, T-SCs offer several advantages, including superior proliferation and a shorter doubling time compared to bone marrow-derived mesenchymal stem cells (MSCs). T-SCs also exhibit multi-lineage differentiation, including mesodermal, endodermal (e.g., hepatocytes and parathyroid-like cells), and even ectodermal cells (e.g., Schwann cells). To this end, numbers of researchers have evaluated the practical use of T-SCs as an alternative source of autologous or allogenic MSCs. In this review, we summarize the details of T-SC isolation and identification and provide an overview of their application in cell therapy and regenerative medicine.

Animal studies using chronic social defeat stress (CSDS) in mice showed that brain-derived neurotrophic factor (BDNF) signaling in the mesolimbic dopamine (DA) circuit is important for the development of social aversion. However, the downstream molecular targets after BDNF release from ventral tegmental area (VTA) DA terminals are unknown. Here, we show that depressive-like behaviors induced by CSDS are mediated in part by Gadd45b downstream of BDNF signaling in the nucleus accumbens (NAc). We show that Gadd45b mRNA levels are increased in susceptible but not resilient mice. Intra-NAc infusion of BDNF or optical stimulation of VTA DA terminals in NAc enhanced Gadd45b expression levels in the NAc. Importantly, Gadd45b downregulation reversed social avoidance in susceptible mice. Together, these data suggest that Gadd45b in NAc contributes to susceptibility to social stress. In addition, we investigated the function of Gadd45b in demethylating CpG islands of representative gene targets, which have been associated with a depressive phenotype in humans and animal models. We found that Gadd45b downregulation changes DNA methylation levels in a phenotype-, gene-, and locus-specific fashion. Together, these results highlight the contribution of Gadd45b and changes in DNA methylation in mediating the effects of social stress in the mesolimbic DA circuit.

Background: Mast cells are skin immune sentinels located in the upper dermis, where wheal formation and sensory nerve stimulation take place. Skin inflammation is occasionally accompanied by mast cell-driven responses with wheals, angioedema, or both. Immunoglobulin E (IgE) antibodies are regarded as typical stimuli to drive mast cell activation. However, various causative factors, including microbial infections, can drive IgE-independent mast cell response. When infected, the innate immunity orchestrates an immune response by activating receptor signaling via Toll-like receptors (TLRs). Objective: In this study, we determined the effect of TLR7 stimulation on mast cells to investigate the possible mechanism of IgE-independent inflammatory response. Methods: Human mast cell (HMC) line, HMC-1 cells were treated with TLR7 agonist and the morphologic alteration was observed in transmission electron microscopy. Further, TLR7 agonist treated HMC-1 cells were conducted to RNA sequencing to compare transcriptomic features. Results: HMC-1 cells treated with TLR7 agonist reveals increase of intracellular vesicles, lipid droplets, and ribosomes. Also, genes involved in pro-inflammatory responses such as angiogenesis are highly expressed, and Il12rb2 was the most highly up-regulated gene. Conclusion: Our data suggest that TLR7 signaling on mast cells might be a potential therapeutic target for mast cell-driven, IgE-independent skin inflammation. (Ann Dermatol 33(5) 402∼408, 2021)

Lymphatic vessels serve as conduits through which immune cells traffic. Because lymphatic vessels are also involved in lipid transport, their function is vulnerable to abnormal metabolic conditions such as obesity and hyperlipidemia. Exactly how these conditions impact immune cell trafficking, however, is not well understood. Here, we found higher numbers of LYVE-1-positive lymphatic endothelial cells and CD3-positive T cells in the lymph nodes of mice fed high-cholesterol or high-fat diets compared with those of mice fed a normal chow diet. To confirm the effect of fat content on immune cell trafficking, the lymphatic endothelial SVEC4-10 cell line was treated with palmitic acid at a 100 μM concentration. After 24 h, palmitic acid-treated cells exhibited increased expression of podoplanin and vascular growth-associated molecules (VEGFC, VEGFD, VEGFR3, and NRP2) and enhanced tube formation. Microarray analysis showed an increase in pro-inflammatory cytokine and chemokine transcription after palmitic acid treatment. Finally, transwell migration assay confirmed that T cell line moved toward medium previously cultured with palmitic acid-treated SVEC4-10 cells. Together, our results suggest that hyperlipidemia drives lymphatic vessel remodeling and T cell migration toward lymphatic endothelial cells.

Although mast cells are traditionally thought to function as effector cells in allergic responses, they have increasingly been recognized as important regulators of various immune responses. Mast cells mature locally; thus, tissue-specific influences are important for promoting mast cell accumulation and survival in the skin and the gastrointestinal tract. In this study, we determined the effects of keratinocytes on mast cell accumulation during Th17-mediated skin inflammation. We observed increases in dermal mast cells in imiquimod-induced psoriatic dermatitis in mice accompanied by the expression of epidermal stem cell factor (SCF), a critical mast cell growth factor. Similar to mouse epidermal keratinocytes, SCF was highly expressed in the human HaCaT keratinocyte cell line following stimulation with IL−17. Further, keratinocytes promoted mast cell proliferation following stimulation with IL−17 in vitro . However, the effects of keratinocytes on mast cells were significantly diminished in the presence of anti−CD117 (stem cell factor receptor) blocking antibodies. Taken together, our results revealed that the Th17-mediated inflammatory environment promotes mast cell accumulation through keratinocyte-derived SCF.

It has been established that mesenchymal stem cells (MSCs) can have a suppressive effect on T cells, yet much remains unknown about the underlying mechanisms that support this effect. The T cell co-stimulatory pathway involving the programmed death-1 (PD-1) receptor and its ligand PD-L1 regulates T cell activation, tolerance, and subsequent immune-mediated tissue damage. In this study, human palatine tonsil-derived MSCs (T-MSCs) constitutively expressed PD-L1 and exhibited a suppressive activity that specifically targeted murine Th17 differentiation. Additionally, polyinosinic-polycytidylic acid (poly I:C), a Toll-like receptor 3 (TLR3) ligand, increased PD-L1 expression on T-MSCs. The elevated PD-L1 levels enhanced the suppressive functions of T-MSCs on Th17 differentiation. Therefore, pre-stimulation of T-MSCs with poly I:C may serve as an effective therapeutic priming step for modulating Th17-dominant immune responses.

Effector B cells are central contributors to the development of autoimmune disease by activating autoreactive T cells, producing pro-inflammatory cytokines and organizing ectopic lymphoid tissue. Conversely, IL-10-producing regulatory B (Breg) cells have pivotal roles in maintaining immunological tolerance and restraining excessive inflammation in autoinflammatory disease. Thus, regulating the equilibrium between antibody-producing effector B cells and Breg cells is critical for the treatment of autoimmune disease. In this study, we investigated the effect of human palatine tonsil-derived mesenchymal stem cells (T-MSCs) on estradiol (E2)-induced B-cell responses in vivo and in vitro. Transplantation of T-MSC into E2-treated mice alleviated B-cell-mediated immune responses and increased the population of IL-10-producing Breg cells. T-MSCs regulated the B-cell populations by producing Epstein–Barr virus (EBV)-induced 3 (EBI3), one of the two subunits of IL-35 that is the well-known inducer of Breg cells. We demonstrate a critical role of EBI3 (IL-35) in vitro by depleting EBI3 in T-MSCs and by adding exogenous IL-35 to the culture system. Taken together, our data suggest that IL-35-secreting MSCs may become an attractive therapeutic to treat B-cell-mediated autoimmune diseases via expanding Breg cells.

The application of mesenchymal stem cells (MSCs) for treating bone-related diseases shows promising outcomes in preclinical studies. However, cells that are isolated and defined as MSCs comprise a heterogeneous population of progenitors. This heterogeneity can produce variations in the performance of MSCs, especially in applications that require differentiation potential in vivo, such as the treatment of osteoporosis. Here, we aimed to identify genetic markers in tonsil-derived MSCs (T-MSCs) that can predict osteogenic potential. Using a single-cell cloning method, we isolated and established several lines of nondifferentiating (ND) or osteoblast-prone (OP) clones. Next, we performed transcriptome sequencing of three ND and three OP clones that maintained the characteristics of MSCs and determined the top six genes that were upregulated in OP clones. Upregulation of WNT16 and DCLK1 expression was confirmed by real-time quantitative PCR, but only WNT16 expression was correlated with the osteogenic differentiation of T-MSCs from 10 different donors. Collectively, our findings suggest that WNT16 is a putative genetic marker that predicts the osteogenic potential of T-MSCs. Thus, examination of WNT16 expression as a selection criterion prior to the clinical application of MSCs may enhance the therapeutic efficacy of stem cell therapy for bone-related complications, including osteoporosis.

Osteoporosis is a disease that affects 35% women and 20% men aged more than 65 years. Reduction in bone formation and increased bone resorption are known factors that drive osteoporosis, but recent studies suggest a positive correlation between bone marrow adipose tissue (MAT) and osteoporosis. Previously, we have observed that tonsil-derived mesenchymal stem cells (T-MSCs) reduce MAT in a mouse model of bone marrow depletion. That prompted us to investigate on the senile osteoporosis to characterize the bone-forming effect, as well as MAT-reducing effect of T-MSCs. In a mouse model of senescence-accelerated mouse prone 6 (SAMP6), we injected T-MSCs or T-MSC conditioned medium (CM) through tail vein and examined changes in bone microstructure using micro-CT scan and hematoxylin & eosin (H&E) staining. Biochemical markers of osteoporosis, deoxypyridinoline (DPD) and osteocalcin, were examined by ELISA. Results demonstrated attenuation in the progression of osteoporosis, in part, by sustaining osteocalcin production and by blocking MAT accumulation. Increase in matrix mineralization was determined using in vitro culture of murine preosteoblast cell line by treatment of T-MSC CM. Interestingly, T-MSC CM induced continuous weight loss and selectively reduced visceral adipose tissue mass. Finally, antiadipogenic effects of T-MSC CM were determined in vitro. In conclusion, regulation of bone together with MAT could be considered as a new therapeutic option for the treatment of senile osteoporosis and this report may provide a framework for future cell therapy using T-MSCs.

Skin forms a physical barrier that protects the body against outside agents. The deepest layer of the skin, the stratum basale, contains two cell types: agent-sensing keratinocytes, and melanin-producing melanocytes. Keratinocytes can sense both harmless commensal organisms and harmful pathogens via Toll-like receptors (TLRs), and keratinocytes subsequently drive immune responses. Activation of TLR3 is required for barrier repair because it stimulates essential genes, including tight junction genes, and inflammatory cytokines. Within the basal layer of the skin, resident melanocytes use their dendritic processes to connect with approximately 30-40 neighboring keratinocytes. Most studies have focused on the transfer of melanin-synthesizing melanosomes from melanocytes to keratinocytes, but the potential regulation of melanogenesis by soluble factor(s) produced by keratinocytes remains to be explored. Studying such regulation in vivo is challenging because of the keratinocyte:melanocyte ratio in the epidermis and the location of the cells within the skin. Therefore, in this study, we investigated whether keratinocytes affected melanocyte melanogenesis in vitro under normal or inflammatory conditions. We found that polyinosinic-polycytidylic acid [poly(I:C)] stimulation induced PD-L1 secretion from HaCaT cells and that poly(I:C)-induced PD-L1 inhibited melanin production by B16F10 cells. These data provide key evidence that keratinocytes can alter melanocyte melanogenesis via the production of soluble factors under inflammatory conditions.

Human mesenchymal stem cells (MSCs) are adult multipotent cells that have plasticity and inhabit the stroma of diverse tissues. The potential utility of MSCs has been heavily investigated in the fields of regenerative medicine and cell therapy. However, MSCs represent diverse populations that may depend on the tissue of origin. Thus, the ability to identify specific MSC populations has remained difficult. Using RNA sequencing, we analyzed the whole transcriptomes of bone marrow-derived MSCs (BMs), adipose tissue-derived MSCs (AMs), and tonsil-derived MSCs (TMs). We categorized highly regulated genes from these MSC groups according to functional gene ontology (GO) classification. AMs and TMs showed higher expression of genes encoding proteins that function in protein binding, growth factor, or cytokine activity in extracellular compartments than BMs. Interestingly, TM were highly enriched for genes coding extracellular, protein-binding proteins compared with AMs. Functional Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis also showed differentially enriched signaling pathways between the three MSC groups. Further, we confirmed surface antigens expressed in common and in a tissue-specific manner on BMs, AMs, and TMs by flow cytometry analysis. This study provides comprehensive characteristics of MSCs derived from different tissues to better understand their cellular and molecular biology.

Mutations in MEGF10 cause early onset myopathy, areflexia, respiratory distress, and dysphagia (EMARDD), a rare congenital muscle disease, but the pathogenic mechanisms remain largely unknown. We demonstrate that short hairpin RNA (shRNA)-mediated knockdown of Megf10, as well as overexpression of the pathogenic human p.C774R mutation, leads to impaired proliferation and migration of C2C12 cells. Myoblasts from Megf10-/- mice and Megf10-/-/mdx double knockout (dko) mice also show impaired proliferation and migration compared to myoblasts from wild type and mdx mice, whereas the dko mice show histological abnormalities that are not observed in either single mutant mouse. Cell proliferation and migration are known to be regulated by the Notch receptor, which plays an essential role in myogenesis. Reciprocal co-immunoprecipitation studies show that Megf10 and Notch1 interact via their respective intracellular domains. These interactions are impaired by the pathogenic p.C774R mutation. Megf10 regulation of myoblast function appears to be mediated at least in part via interactions with key components of the Notch signaling pathway, and defects in these interactions may contribute to the pathogenesis of EMARDD.

Saturated free fatty acids (FFAs) act as lipid mediators and induce insulin resistance in skeletal muscle. Specifically, in obesity‐related diseases such as type 2 diabetes, FFAs directly reduce insulin sensitivity and glucose uptake in skeletal muscle. However, the knowledge of how FFAs mediate inflammation and subsequent tissue disorders, including fibrosis in skeletal muscle, is limited. FFAs are a natural ligand for toll‐like receptor 2 (TLR2) and TLR4, and induce chronic low‐grade inflammation that directly stimulates skeletal muscle tissue. However, persistent inflammatory stimulation in tissues could induce pro‐fibrogenic processes that ultimately lead to perturbation of the tissue architecture and dysfunction. Therefore, blocking the link between inflammatory primed skeletal muscle tissue and connective tissue might be an efficient therapeutic option for treating obesity‐induced muscle inactivity. In this study, we investigated the impact of conditioned medium obtained from human palatine tonsil‐derived mesenchymal stem cells (T‐MSCs) on the interaction between skeletal muscle cells stimulated with palmitic acid (PA) and fibroblasts. We found that PA‐treated skeletal muscle cells actively secreted interleukin‐1β (IL‐1β) and augmented the migration, proliferation and expression of fibronectin in L929 fibroblasts. Furthermore, T‐CM inhibited the skeletal muscle cell‐derived pro‐fibrogenic effect via the production of the interleukin‐1 receptor antagonist (IL‐1Ra), which is an inhibitor of IL‐1 signalling. Taken together, our data provide novel insights into the therapeutic potential of T‐MSC‐mediated therapy for the treatment of pathophysiological processes that occur in skeletal muscle tissues under chronic inflammatory conditions.

The regulation of microglial cell phenotype is a potential therapeutic intervention in neurodegenerative disease. Previously, we reported that transforming growth factor-β (TGF-β) levels in mesenchymal stromal cells (MSCs) could be used as potential biological markers to predict the effectiveness of autologous MSC therapy in patients with amyotrophic lateral sclerosis. However, the underlying mechanism of TGF-β in MSCs was not fully elucidated in determining the functional properties of microglia. In this study, we aimed to clarify the role of TGF-β that is involved in MSC effectiveness, especially focusing on microglia functional properties that play a pivotal role in neuroinflammation. We found that MSC-conditioned media (MSC-CM) inhibited proinflammatory cytokine expression, restored alternative activated microglia phenotype markers (fractalkine receptor, mannose receptor, CD200 receptor), and enhanced phagocytosis in lipopolysaccharide (LPS)-stimulated microglia. In addition, TGF-β in MSC-CM played a major role in these effects by inhibiting the nuclear factor-κB pathway and restoring the TGF-β pathway in LPS-stimulated microglia. Recombinant TGF-β also induced similar effects to MSC-CM in LPS-stimulated microglia. Therefore, we propose that MSCs can modulate the functional properties of microglia via TGF-β secretion, switching them from a classically activated phenotype to an inflammation-resolving phenotype. The latter role may be associated with the inhibition of neuroinflammatory processes in neurodegenerative disorders. Significance The results of this study showed that microglia functional properties may be modulated depending on the composition and quantity of mesenchymal stromal cell (MSC)-secreting factors. Transforming growth factor (TGF)-β is proposed as a modulator of microglia functional properties among MSC-secreting factors, and this study aligns with a previous clinical study by these same authors. TGF-β releasing capacity could be an important factor enhancing the therapeutic efficacy of MSCs in clinical trials.

Background: The pathogenesis of psoriasis may involve the interleukin (IL)-23 and Th17-mediated immune responses. Th17 cells secret IL-17 and IL-22, which mediates dermal inflammation and acanthosis. Objective: As inhibitor of nuclear factor κB kinase-α (IKKα) has been previously identified as a primary regulator of keratinocyte differentiation and proliferation, we proposed that IL-17 and IL-22 might affect keratinocyte differentiation by changing the expression of IKKα. Methods: We employed HaCaT cells maintained culture medium at a low calcium concentration (0.06 mM) and induced differentiation by switching to the high concentration (2.8 mM) media with IL-17 or IL-22, then compared the IKKα expression and the cell cycle. We employed reconstituted human epidermal skin (Neoderm) and mice ears for the in vivo studies. Results: Elevated calcium concentration induced IKKα expression and terminal differentiation with cell cycle arrest in HaCaT cell cultures. Moreover, IL-17 and IL-22 treatment also induced IKKα in HaCaT cells and reconstituted human epidermis. IKKα induction was also noted, following the injection of IL-17 and IL-22 into mice ears. Conclusion: Although the induction of IKKα was accompanied by keratinocyte diffe-rentiation, IL-17 and IL-22 did not affect calcium-mediated differentiation or the cell cycle. Rather, IL-17 and IL-22 appear to contribute to the inflammation occurring via the induction of IKKα from keratinocytes or skin layers. (Ann Dermatol 24(4) 398∼405, 2012)

Background aims. Although mesenchymal stromal cells (MSC) from human palatine tonsils (tonsillar MSC, T-MSC) have been isolated, whether T-MSC isolated from multiple donors are feasible for cell banking has not been studied. Methods . T-MSC before and after a standard protocol of cryopreservation and thawing were assessed regarding several basic characteristics, including colony-forming unit – fi broblast features, MSC-specifi c surface antigen profi les, and inhibition of alloreactive T-cell proliferation. In vitro mesodermal differentiation potentials to adipocytes, osteocytes and chondrocytes were detected by staining with either cell-specifi c dyes or antibody after incubation with each appropriate differentiation medium. Expression of mesoderm-specifi c genes was also quantifi ed by real-time polymerase chain reaction (PCR) assay. Expression profi les of endoderm-specifi c genes were identifi ed by reverse transcription PCR assay. The feasibility of T-MSC in future engraftment was tested by short tandem repeat (STR) analysis using genomic DNA isolated randomly from three independent subjects. Results . Both fresh and cryopreserved – thawed T-MSC showed a similar high proliferation capacity and expressed primitive cell-surface markers. Hematopoietic cell markers, HLA-DR, co-stimulatory molecules and follicular dendritic cell markers were not detected. In addition to mesodermal differentiation, fresh and cryopreserved – thawed cells also underwent endodermal differentiation, as evidenced by the expression of endoderm-specifi c genes including forkhead box A2 (FoxA2), SIX homeobox 1 (Six1) and chemokine (C-C motif) ligand 21 (CCL21). Both cells signifi cantly decreased phorbol 12- myristate 13-acetate (PMA)-induced T-cell proliferation. T-MSC from three independent donors formed chimerism in STR analysis. Conclusions . Our results demonstrate for the fi rst time that T-MSC are a potentially good source for MSC banking.

Tonsils comprise part of the mucosal immune system and contain lymphocytes, macrophages, and follicular dendritic cells (FDCs). FDCs are located in the B cell area of the follicles of secondary lymphoid organs, such as the spleen, tonsils, or lymph nodes, and they trap and retain immune complexes on their surfaces to regulate B cell activation and maturation. Stromal cells from the palatine tonsils are often used for FDC in vitro studies, and it has been reported that human palatine tonsils may be a good source of multipotent mesenchymal cells. Therefore, we assessed whether tonsil-derived mesenchymal stromal cells could differentiate into a FDC-like phenotype. We discovered that stromal cells isolated from human tonsils not only had the potential to differentiate into various cell types of mesenchymal origin, but they also could differentiate into FDC-like cells under cytokine stimulation in vitro.

Neutropenia is a principal complication of cancer treatment. We investigated the supportive effect of adipose tissue-derived mesenchymal stem cells (AD-MSCs) on the viability and function of neutrophils. Neutrophils were derived from HL-60 cells by dimethylformamide stimulation and cultured with or without AD-MSCs under serum-starved conditions to evaluate neutrophil survival, proliferation, and function. Serum starvation resulted in the apoptosis of neutrophils and decreased cell survival. The co-culture of neutrophils and AD-MSCs resulted in cell survival and inhibited neutrophil apoptosis under serum-starved conditions. The survival rate of neutrophils was prolonged up to 72 h, and the expression levels of interferon (IFN)-α, granulocyte colony-stimulating factor (G-CSF), granulocyte–macrophage colony-stimulating factor, and transforming growth factor (TGF)-β in AD-MSCs were increased after co-culture with neutrophils. AD-MSCs promoted the viability of neutrophils by inhibiting apoptosis as well as enhancing respiratory burst, which could potentially be mediated by the increased expression of IFN-α, G-CSF, and TGF-β. Thus, we conclude that the use of AD-MSCs may be a promising cell-based therapy for increasing immunity by accelerating neutrophil function.

Allergic asthma is characterized by infiltration of eosinophils, elevated Th2 cytokine levels, airway hyperresponsiveness, and IgE. In addition to eosinophils, mast cells, and basophils, a variety of cytokines are also involved in the development of allergic asthma. The pivotal role of eosinophils in the progression of the disease has been a subject of controversy. To determine the role of eosinophils in the progression of airway inflammation, we sensitized and challenged BALB/c wild-type (WT) mice and eosinophil-deficient ΔdblGATA mice with ovalbumin (OVA) and analyzed different aspects of inflammation. We observed increased eosinophil levels and a Th2-dominant response in OVA-challenged WT mice. In contrast, eosinophil-deficient ΔdblGATA mice displayed an increased proportion of mast cells and a Th17-biased response following OVA inhalation. Notably, the levels of IL-33, an important cytokine responsible for Th2 immune deviation, were not different between WT and eosinophil-deficient mice. We also demonstrated that mast cells induced Th17-differentiation via IL-33/ST2 stimulation in vitro. These results indicate that eosinophils are not essential for the development of allergic asthma and that mast cells can skew the immune reaction predominantly toward Th17 responses via IL-33 stimulation.

Restricted numbers and poor regenerative properties limit the use of adult stem cells. We tested the effect of hypoxic treatment as a method by which to increase cell migration. Bone marrow cells (BMCs) were cultured under oxygen saturations of 0.1, 3, and 20% for 24h. After hypoxic treatment, BMCs of apoptotic fraction were decreased. The expression of CXCR4 was noticeably increased in the hypoxia-treated BMCs and their migration in response to SDF-1alpha was enhanced compared with cells cultured under normoxic condition. Hypoxic BMCs had a higher degree of engraftment to the CCl(4)-injured liver than the normoxic cells. Hypoxic treatment of BMCs may have merits in decreasing apoptosis of those cells as well as in enhancing cellular migration to SDF-1alpha, the chemokine which binds to BMCs expressed CXCR4 and to the injured tissue, such as CCl(4) damaged liver.

Keratinocytes constitute the first-line barrier against exogenous antigens and contain Toll-like receptors (TLRs), which function as pattern-recognition molecules to activate antimicrobial innate immune responses. In an effort to ascertain whether or not filaggrin (filament-aggregating protein) expression affected the TLR-mediated responses of keratinocytes, we transfected filaggrin siRNA into HaCaT human keratinocyte cells and determined that thymic stromal lymphopoietin (TSLP) and IL-6 secretion were increased by poly(I:C) stimulus. Additionally, TSLP expression is increased in filaggrin knockdown as well as TLR3 stimulation in reconstituted human epidermal layers. Therefore, the findings of this study show that reduced filaggrin levels may influence innate immune responses via TLR stimuli and may contribute to the pathogenesis of inflammatory skin disease via TSLP expression.

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) represent a promising tool for stem cell-based therapies. However, the majority of MSCs fail to reach the injury site and have only minimal therapeutic effect. In this study, we assessed whether hypoxia/reoxygenation (H/R) preconditioning of human BM-MSCs could increase their functional capacity and beneficial effect on ischemic rat cortical neurons. Human BM-MSCs were cultured under hypoxia (1% O2) and with long-term reoxygenation for various times to identify the optimal conditions for increasing their viability and proliferation. The effects of H/R preconditioning on the BM-MSCs were assessed by analyzing the expression of prosurvival genes, trophic factors, and cell migration assays. The functionally improved BM-MSCs were cocultured with ischemic rat cortical neurons to compare with normoxic cultured BM-MSCs. Although the cell viability and proliferation of BM-MSCs were reduced after 1 day of hypoxic culture (1% O2), when this was followed by 5-day reoxygenation, the BM-MSCs recovered and multiplied extensively. The immunophenotype and trilineage differentiation of BM-MSCs were also maintained under this H/R preconditioning. In addition, the preconditioning enhanced the expression of prosurvival genes, the messenger RNA (mRNA) levels of various trophic factors and migration capacity. Finally, coculture with the H/R-preconditioned BM-MSCs promoted the survival of ischemic rat cortical neurons. H/R preconditioning of BM-MSCs increases prosurvival signals, trophic factor release, and cell migration and appears to increase their ability to rescue ischemic cortical neurons. This optimized H/R preconditioning procedure could provide the basis for a new strategy for stem cell therapy in ischemic stroke patients.

Human mast cells are potent effector cells in host defense mechanisms of innate and acquired immunity, including inflammatory diseases such as asthma and atherosclerosis. Mast cells originate from pluripotent hematopoietic progenitors in the bone marrow. Activation of mast cells by different stimuli triggers the release of a large range of mediators, including de novo synthesized eicosanoids which are highly biologically active lipid mediators. For the generation of lipid mediators, cytoplasmic lipid droplets have been shown to function as a major intracellular pool of arachidonic acid, the precursor for eicosanoids biosynthesis. The article summarizes current knowledge on mast cell biosynthesis of lipid mediator and the role in inflammation.

We have investigated BM (bone marrow)-derived MSCs (mesenchymal stem cells) for the treatment of liver injury. It was hypothesized that MSC-mediated resolution of liver injury could occur through an antioxidative process. After being injected with CCl4 (carbon tetrachloride), mice were injected with syngenic BM-derived MSCs or normal saline. Oxidative stress activity of the MSCs was determined by the analysis of ROS (reactive oxygen species) and SOD (superoxide dismutase) activity. In addition, cytoprotective genes of the liver tissue were assessed by real-time PCR and ARE (antioxidant-response element) reporter assay. Up-regulated ROS of CCl4-treated liver cells was attenuated by co-culturing with MSCs. Suppression of SOD by adding an SOD inhibitor decreased the effect of MSCs on injured liver cells. MSCs significantly increased SOD activity and inhibited ROS production in the injured liver. The gene expression levels of Hmox-1 (haem oxygenase-1), BI-1 (Bax inhibitor-1), HGF (hepatocyte growth factor), GST (glutathione transferase) and Nrf2 (nuclear factor-erythoid 2 p45 subunit-related factor 20), attenuated by CCl4, were increased up to basal levels after MSC transplantation. In addition, MSCs induced an ARE, shown by luciferase activity, which represented a cytoprotective response in the injured liver. Evidence of a new cytoprotective effect is shown in which MSCs promote an antioxidant response and supports the potential of using MSC transplantation as an effective treatment modality for liver disease.

Cell therapy using MSCs (mesenchymal stem cells) might be effective treatment for refractory GVHD (graft-versus-host disease). However, the fate and distribution of MSCs after transplantation remains unclear. In this study, an animal model was developed to monitor the dynamic distribution of MSCs in mice with GVHD. A GVHD mouse model was established by transplanting C57BL/6 donor bone marrow cells and C57BL/6 EGFP (enhanced green fluorescent protein) splenocytes into lethally irradiated BALB/c nude recipient mice. Donor MSCs were obtained from MHC-identical C57BL/6 RFP (red fluorescent protein) mice and infused into the recipient mice on the same transplantation day. In vivo movement of the donor splenocytes (EGFP) and MSCs (RFP) were evaluated by measuring the biofluorescence (IVIS-Xenogen system). Donor splenocytes and MSCs reached the lungs first, and then the gastrointestinal tract, lymph nodes and skin, in that order; the transit time and localization site of these cells were very similar. In the recipient mouse with GVHD, the number of detectable cells declined with time, as assessed by biofluorescence imaging and confirmed by RT (real-time)-PCR. This bioimaging system might be useful for preclinical testing and the design of therapeutic strategies for monitoring the dynamic distribution of MSCs with GVHD.

Osteoclasts (OCLs) are multinucleated cells that are derived from the monocyte/macrophage hematopoietic lineage in response to receptor activator of NF-kappaB ligand (RANKL) activation. They are specialized cells responsible for physiological bone resorption and as well as pathologic bone loss. In addition to their unique ability to resorb bone, OCLs also play a potential role in the mobilization of hematopoietic progenitor cells from the bone marrow (BM), particularly under various stress stimuli (e.g. hypoxia, injury or inflammation). We investigated the effect of activated OCLs on the stem cell niche and whether this leads to mobilization of hematopoietic progenitors. We induced activated OCLs from the RAW264.7 cell line through stimulation with RANKL and we quantified the levels of the stem cell niche component SDF-1 on the osteblasts and CXCR4 on the bone marrow cells (BMCs) by culturing with supernatants from activated OCLs. In addition, we exposed mice to stress by inducing liver injury with CCl4 followed by injecting RANKL to activate OCLs and compared the effect on the mobilization of hematopoietic progenitor cells from the BM. We found that functional OCLs cleaved SDF-1alpha in the osteoblasts and increased CXCR4 expression in the BMCs. Moreover, under stress in vivo, mobilized hematopoietic progenitor cells were significantly increased after RANKL treatment. These results suggest that OCLs might be involved in alteration of the interaction between SDF-1 and CXCR4 leading to mobilization of hematopoietic progenitor cells from the BM.

Graft-versus-host disease (GvHD) remains a major complication after allogeneic hematopoietic cell transplantation (HCT). Recent literature demonstrates a potential benefit of human mesenchymal stromal cells (MSC) for the treatment of refractory GvHD; however, the optimal dose remains uncertain. We set out to develop an animal model that can be used to study the effect of MSC on GvHD.A GvHD mouse model was established by transplanting C3H/he donor bone marrow (BM) cells and spleen cells into lethally irradiated BALB/c recipient mice. MSC were obtained from C3H/he mice and the C3H/10T1/2 murine MSC line.The mRNA expression of Foxp3 in regional lymph nodes (LN) localized with T cells was markedly increased by the addition of C3H10T1/2 cells in a real-time polymerase chain reaction (PCR). Using a mixed lymphocyte reaction, we determined the optimal splenocyte proliferation inhibition dose (MSC:splenocyte ratios 1:2 and 1:1). Three different C3H10T1/2 cell doses (low, 0.5 x 10(6), intermediate, 1 x 10(6), and high, 2 x 10(6)) with a consistent splenocyte dose (1 x 10(6)) were evaluated for their therapeutic potential in an in vivo GvHD model. The clinical and histologic GvHD score and Kaplan-Meier survival rate were improved after MSC transplantation, and these results demonstrated a dose-dependent inhibition.We conclude that MSC inhibit GvHD in a dose-dependent manner in this mouse model and this model can be used to study the effects of MSC on GvHD.

We have previously reported that bone marrow cells (BMCs) participate in the regeneration after liver injury. However, it is not established that this is the result of differentiation of hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs) or the combination of both. We investigated the contribution of each cell fraction to the regenerative process. First, we confirmed that transplanted stem cells migrate directly to injured liver tissue without dispersing to other organs. Next, we divided green fluorescent protein (GFP)-expressing BMCs into three populations as mononuclear cells, MSCs and HSCs. We then compared the engraftment capacity after transplantation of each fraction of cells into liver-injured mice. Of these, the MSCs transplanted group showed the highest GFP fluorescence intensities in liver tissue by flow cytometry analysis and confocal microscopic observation. Furthermore, MSCs showed differentiation potential into hepatocytes when co-cultured with injured liver cells, which suggests that MSCs showed highest potential for the regeneration of injured liver tissue compared with those of the other two cell refractions.

Background Mesenchymal stromal cells (MSC) comprise one of the BM stromal cells that are known to support hematopoiesis. It has also been suggested recently that MSC display immunosuppressive capacities through inhibiting the differentiation of monocyte-derived DC. DC travel to the lymph nodes (LN) to present Ag to T cells, and CCL21 is the chemokine that plays an important role in DC migration into the T-cell area of LN. We addressed the effect of MSC on this chemotactic activity of DC, one of the typical characteristics upon maturation. Methods BM cells were isolated and then cultured for generation of myeloid DC in the presence of GM-CSF and/or lipopolysaccharide with or without MSC. MSC were identified by flow cytometry of the immunologic markers and by performing colony-forming unit fibroblast assay. Migration of DC was observed with a newly developed time-lapse video microscopic technique. Results MSC co-culture inhibited the initial differentiation of DC, as well as their maturation. The matured DC actively migrated directionally in response to CCL21, a powerful DC-attracting chemokine, whereas the MSC co-cultured DC did not. Discussion Collectively, the findings of these experiments raise the possibility that MSC suppress the migratory function of DC and so they may serve immunoregulatory activities through the modulation of the Ag-presenting function of DC.