Microenvironment-responsive bilayer hydrogel microspheres with gelatin-shell for osteoarthritis treatment.

Osteoarthritis is a long-term degenerative condition of the joints that is characterized by the breakdown of cartilage and inflammation of the synovial membrane. The presence of an inflammatory microenvironment and the degradation of the extracellular matrix produced by chondrocytes leads to the aggravation of cartilage injury, hindering the treatment of osteoarthritis. A promising approach to address this issue is to apply a combined strategy that is sensitive to the specific conditions in osteoarthritic joints and possesses properties that can reduce inflammation and promote cartilage healing. Here, inspired by the structure of chocolate-covered peanuts, we developed an injectable, environment-responsive bilayer hydrogel microsphere using microfluidics technology. The microsphere applied chondroitin sulfate methacryloyl (ChsMA) as its core and was coated with a methacryloyl gelatin (GelMA) shell that was loaded with celecoxib (CLX) liposomes (ChsMA+CLX@Lipo@GelMA). CLX was released from the liposomes when the GelMA shell rapidly degraded in response to the osteoarthritic microenvironment and suppressed the generation of inflammatory agents, demonstrating a beneficial impact of the outer shell in reducing inflammation. While the inner methacryloyl microsphere core degraded, chondroitin sulfate was released to promote chondrocyte anabolism and facilitate cartilage repair. Thus, the synthesized bilayer hydrogel microspheres hold great potential for treating osteoarthritis.

Cellular senescence in skeletal disease: mechanisms and treatment.

The musculoskeletal system supports the movement of the entire body and provides blood production while acting as an endocrine organ. With aging, the balance of bone homeostasis is disrupted, leading to bone loss and degenerative diseases, such as osteoporosis, osteoarthritis, and intervertebral disc degeneration. Skeletal diseases have a profound impact on the motor and cognitive abilities of the elderly, thus creating a major challenge for both global health and the economy. Cellular senescence is caused by various genotoxic stressors and results in permanent cell cycle arrest, which is considered to be the underlying mechanism of aging. During aging, senescent cells (SnCs) tend to aggregate in the bone and trigger chronic inflammation by releasing senescence-associated secretory phenotypic factors. Multiple signalling pathways are involved in regulating cellular senescence in bone and bone marrow microenvironments. Targeted SnCs alleviate age-related degenerative diseases. However, the association between senescence and age-related diseases remains unclear. This review summarises the fundamental role of senescence in age-related skeletal diseases, highlights the signalling pathways that mediate senescence, and discusses potential therapeutic strategies for targeting SnCs.

BMP-2 functional polypeptides relieve osteolysis via bi-regulating bone formation and resorption coupled with macrophage polarization.

Osteolysis caused by wear debris around the prosthesis is the main reason for aseptic loosening. Extending prosthetic service life is still challenging. In this study, we first synthesized a bone morphogenetic protein-2 (BMP-2) functional polypeptide (BMP2pp), and evaluated the effects of BMP2pp on macrophage polarization and impaired osteogenesis caused by titanium (Ti) particles in vitro. Then, we delineated the impact of BMP2pp on bone formation and resorption in a mouse calvarial bone osteolysis model induced by Ti particles. The results showed that BMP2pp not only alleviated the Ti-induced inhibition of osteoblastic differentiation in human placenta-derived mesenchymal stem cells (hPMSCs) but also prevented Ti-induced M1 macrophage polarization and promoted M2 macrophage differentiation in mice. Conditioned medium from BMP2pp-activated macrophages increased the osteogenesis of hPMSCs. The western blot results indicated a significant decrease in the expression of NF-κB inducing kinase (NIK) and phospho-NF-κB p65 in bone marrow-derived macrophages treated with BMP2pp. Furthermore, we clarified the protective effect of BMP2pp on bone formation and the reduction in bone resorption coupled with the immunomodulatory properties of calvarial osteolysis in mice. In summary, BMP2pp ameliorated the Ti-mediated impairment in osteogenic potential of hPMSCs, suppressed the M1 polarization of macrophages by inhibiting the activation of the NF-κB signaling pathway, and ameliorated Ti-induced bone osteolysis. Our research suggests that BMP2pp may be a potential option for treating prosthetic loosening induced by wear debris from prostheses.

Immunopolarization-regulated 3D printed-electrospun fibrous scaffolds for bone regeneration.

Three-dimension (3D)-printed bioscaffolds are precise and personalized for bone regeneration. However, customized 3D scaffolds may activate the immune response in vivo and consequently impede bone formation. In this study, with layer-by-layer deposition and electrospinning technology to control the physical structure, 3D-printed PCL scaffolds with PLLA electrospun microfibrous (3D-M-EF) and nanofibrous (3D-N-EF) composites were constructed, and their immunomodulatory effect and the subsequent osteogenic effects were explored. Compared to 3D-N-EF scaffolds, 3D-M-EF scaffolds polarized more RAW264.7 cells toward alternatively activated macrophages (M2), as demonstrated by increased M2 and deceased classically activated macrophage (M1) phenotypic marker expression in the cells. In addition, the 3D-M-EF scaffolds shifted RAW264.7 cells to the M2 phenotype through PI3K/AKT signaling and enhanced VEGF and BMP-2 expression. Conditional medium from the RAW264.7 cells seeded in 3D-M-EF scaffolds promoted osteogenesis of MC3T3-E1 cells. Furthermore, in vivo study of repairing rat calvarial defects, the 3D-M-EF scaffolds increased the polarization of M2 macrophages, enhanced angiogenesis, and accelerated new bone formation. Collectively, our data suggested that well-designed 3D-M-EF scaffolds are favorable for osteogenesis through regulation of M2 polarization. Therefore, it is potential to utilize the physical structure of 3D-printed scaffolds to manipulate the osteoimmune environment to promote bone regeneration.

Substrate stiffness modulates bone marrow-derived macrophage polarization through NF-κB signaling pathway.

The stiffness of the extracellular matrix (ECM) plays an important role in regulating the cellular programming. However, the mechanical characteristics of ECM affecting cell differentiation are still under investigated. Herein, we aimed to study the effect of ECM substrate stiffness on macrophage polarization. We prepared polyacrylamide hydrogels with different substrate stiffness, respectively. After the hydrogels were confirmed to have a good biocompatibility, the bone marrow-derived macrophages (BMMs) from mice were incubated on the hydrogels. With simulated by the low substrate stiffness, BMMs displayed an enhanced expression of CD86 on the cell surface and production of reactive oxygen species (ROS) in cells, and secreted more IL-1ß and TNF-α in the supernatant. On the contrary, stressed by the medium stiffness, BMMs expressed more CD206, produced less ROS, and secreted more IL-4 and TGF-ß. In vivo study by delivered the hydrogels subcutaneously in mice, more CD68+CD86+ cells around the hydrogels with the low substrate stiffness were observed while more CD68+CD206+ cells near by the middle stiffness hydrogels. In addition, the expressions of NIK, phosphorylated p65 (pi-p65) and phosphorylated IκB (pi-IκB) were significantly increased after stimulation with low stiffness in BMMs. Taken together, these findings demonstrated that substrate stiffness could affect macrophages polarization. Low substrate stiffness promoted BMMs to shift to classically activated macrophages (M1) and the middle one to alternatively activated macrophages (M2), through modulating ROS-initiated NF-κB pathway. Therefore, we anticipated ECM-based substrate stiffness with immune modulation would be under consideration in the clinical applications if necessary.

Characterization and immunogenicity of bone marrow-derived mesenchymal stem cells under osteoporotic conditions.

Mesenchymal stem cells (MSCs) are characterized by their multilineage potential and low immunogenicity. However, the properties of MSCs under pathological conditions are unclear. The current study investigated the differentiation potential and immunological characteristics of bone marrow-derived MSCs from ovariectomized-osteoporotic rats (OP-BMSCs). Although the expression of cell morphology- and stemness-related surface markers was similar between OP-BMSCs and BMSCs from healthy rats (H-BMSCs), the proliferation rate was significantly decreased compared with that of H-BMSCs. Regarding multilineage potential, osteogenesis and chondrogenesis abilities of OP-BMSCs decreased, but the adipogenesis ability was significantly enhanced compared with that of H-BMSCs. As expected, decreased osteogenesis following osteogenic induction resulted in reduced expression of ß-catenin, osteocalcin, and runt-related transcription factor 2 in OP-BMSCs. Remarkably, the expression of the co-stimulatory proteins CD40 and CD80 was significantly higher, whereas the expression of the negative co-stimulatory molecule programmed cell death ligand 1 was significantly lower in the OP-BMSCs than that in H-BMSCs. Consequently, H-BMSCs inhibited the proliferation and secretion of inflammatory cytokines from anti-CD3 antibody-activated T cells, whereas OP-BMSCs did not. These results indicate that decreased osteogenesis and increased immunogenicity of OP-BMSCs contribute to bone loss in osteoporosis.

Haem oxygenase-1 induction prevents glucocorticoid-induced osteoblast apoptosis through activation of extracellular signal-regulated kinase1/2 signalling pathway.

BACKGROUND: High-dose glucocorticoid (GC) therapy always causes osteoporosis partly by inducing osteoblast apoptosis. However, the underlying mechanisms of GC-induced apoptosis remain elusive. Haem oxygenase-1 (HO-1) is a cytoprotective protein that rescues cells from H2O2 or high glucose-induced apoptosis. In bone metabolism, HO-1 also participates in osteoclast and osteoblast differentiation. OBJECTIVE: The present study aimed to investigate the protective role of HO-1 against GC-induced osteoblast apoptosis and to elucidate the underlying mechanism. METHODS: Mouse osteoblastic MC3T3-E1 cells were treated with dexamethasone (Dex) for 24 h in the presence or absence of cobalt (III) protoporphyrin IX chloride (CoPP, an inducer of HO-1). In some experiments, U0126 was added to the culture 1 h before CoPP treatment. The induction of apoptosis was determined by flow cytometry. Cell viability was evaluated using a cell counting kit-8 (CCK-8) assay. The expression levels of Bax and bcl-2 were measured by real-time polymerase chain reaction and Western blot. HO-1, extracellular signal-regulated kinase (ERK)-1/2 and pERK1/2 protein levels were measured by Western blot analysis. RESULTS: Dex promoted apoptosis and inhibited cell viability in MC3T3-E1 cells. In addition, Dex significantly increased Bax expression and reduced Bcl-2 expression. The expression of HO-1 was also reduced after Dex treatment. HO-1 induction by CoPP significantly attenuated Dex-induced apoptosis as evidenced by Annexin V/PI staining. The mRNA expression level of antiapoptotic gene Bcl-2 was also increased after CoPP treatment. Moreover, CoPP treatment increased the phosphorylation of ERK1/2. U0126, an inhibitor of ERK activation, significantly abrogated the protective effects of CoPP. CONCLUSION: Our results demonstrate that HO-1 induction by CoPP can attenuate Dex-induced apoptosis of mouse osteoblastic MC3T3-E1 cells. The antiapoptotic effect of HO-1 induction may be correlated with the activation of ERK1/2 signalling pathway. The translational potential of this article: HO-1 induction by CoPP can prevent GC-induced osteoblast apoptosis. Our findings will highlight the therapeutic potential of HO-1 induction in GC-induced osteoporosis.

Macrophages and bone inflammation.

Bone metabolism is tightly regulated by the immune system. Accelerated bone destruction is observed in many bone diseases, such as rheumatoid arthritis, fracture, and particle-induced osteolysis. These pathological conditions are associated with inflammatory responses, suggesting the contribution of inflammation to bone destruction. Macrophages are heterogeneous immune cells and are polarized into the proinflammatory M1 and antiinflammatory M2 phenotypes in different microenvironments. The cytokines produced by macrophages depend on the macrophage activation and polarization. Macrophages and macrophage-derived cytokines are important to bone loss in inflammatory bone disease. Recent studies have shown that macrophages can be detected in bone tissue and interact with bone cells. The interplay between macrophages and bone cells is critical to bone formation and repair. In this article, we focus on the role of macrophages in inflammatory bone diseases, as well as discuss the latest studies about macrophages and bone formation, which will provide new insights into the therapeutic strategy for bone disease.

Metformin Enhances Osteogenesis and Suppresses Adipogenesis of Human Chorionic Villous Mesenchymal Stem Cells.

Metformin is the first-line anti-hyperglycemic drugs commonly used to treat type 2 diabetes. Recent studies have shown that metformin can enhance bone formation through induction of endothelial nitric oxide synthase (eNOS). Human chorionic villous mesenchymal stem cells (CV-MSCs) are promising candidates for regenerative medicine. The present study aimed to investigate the effects of metformin on the osteogenic and adipocytic differentiation of human CV-MSCs, and to elucidate the underlying mechanism. CV-MSCs, prepared from human term placentae, were cultured with different concentrations of metformin. Treatment for 72 hours with 0.05 mM metformin had no noticeable effect on the proliferation of CV-MSCs. Consequently, CV-MSCs were cultured for seven or 14 days in the osteogenic medium supplemented with 0.05 mM metformin. Treatment for seven days with metformin increased the expression levels of osteogenic protein mRNAs, including alkaline phosphatase, runt-related transcription factor 2, and osteopontin. Metformin also enhanced the mineralization of CV-MSCs. Furthermore, metformin induced the expression of eNOS in CV-MSCs during osteogenic differentiation. By contrast, when CV-MSCs were cultured for 14 days in the adipogenic medium, 0.05 mM metformin inhibited the expression of adipogenic protein mRNAs, including proliferators-activated receptor-γ and CCAAT/enhancer binding protein-α. The lipid droplet accumulation was also reduced on 28 days after metformin treatment. These findings indicate that metformin can enhance osteogenic differentiation of CV-MSCs and reduce adipocyte formation. The effect of metformin on osteogenic differentiation of CV-MSCs may be associated with eNOS expression. Our findings will highlight the therapeutic potential of metformin in osteoporosis and bone fracture.

Improved osteogenesis and upregulated immunogenicity in human placenta-derived mesenchymal stem cells primed with osteogenic induction medium.

BACKGROUND: Mesenchymal stem cells (MSCs) are widely used in cell-based therapy owing to their multilineage potential and low immunogenicity. However, low differentiation efficiency and unpredictable immunogenicity of allogeneic MSCs in vivo limit their success in therapeutic treatment. Herein, we evaluated the differentiation potential and immunogenicity of human placenta-derived MSCs manipulated with osteogenic priming and dedifferentiation process. METHODS: MSCs from human placentas were subjected to osteogenic induction and then cultivated in osteogenic factor-free media; the obtained cell population was termed dedifferentiated mesenchymal stem cells (De-MSCs). De-MSCs were induced into osteo-, chondro- and adipo-differentiation in vitro. Cell proliferation was quantified by a Cell-Counting Kit-8 or tritiated thymidine ([(3)H]-TdR) incorporation. Meanwhile, the osteogenesis of De-MSCs in vivo was assayed by real-time PCR and histological staining. The expressions of stem cell markers and co-stimulatory molecules on De-MSCs and lymphocytes from primed BALB/c mouse with De-MSCs were determined by flow cytometry. RESULTS: De-MSCs exhibited some properties similar to MSCs including multiple differentiation potential and hypoimmunogenicity. Upon re-osteogenic induction, De-MSCs exhibited higher differentiation capability than MSCs both in vitro and in vivo. Of note, De-MSCs had upregulated immunogenicity in association with their osteogenesis, reflected by the alternated expressions of co-stimulatory molecules on the surface and decreased suppression on T cell activation. Functionally, De-MSC-derived osteoblasts could prime lymphocytes of peripheral blood and spleen in BALB/c mice in vivo. CONCLUSIONS: These data are of great significance for the potential application of De-MSCs as an alternative resource for regenerative medicine and tissue engineering. In order to avoid being rejected by the host during allogeneic De-MSC therapy, we suggest that immune intervention should be considered to boost the immune acceptance and integration because of the upregulated immunogenicity of De-MSCs with redifferentiation in clinical applications.

Hypoxia Promotes Osteogenesis of Human Placental-Derived Mesenchymal Stem Cells.

Placental-derived mesenchymal stem cells (pMSCs) are promising candidates for regenerative medicine because they possess high proliferative capacity and multi-differentiation potential. Human pMSCs are residing in an environment with low oxygen tension in the body. Heme oxygenase-1 (HO-1) is known to participate in the regulation of MSC differentiation. The present study aimed to investigate the impact of hypoxia on the osteogenic differentiation of human pMSCs, and to elucidate the role of HO-1 in the osteogenic differentiation of hypoxic pMSCs. Human pMSCs were cultured under normoxia (21% O2) or hypoxia (5% O2) for 3 days. We found that hypoxia maintained the morphology and immunophenotype of human pMSCs. The expression of stemness markers Oct4, Nanog, and Sox2 was increased under hypoxia. After a 5-day hypoxic culture, the proliferation ability of pMSCs was increased, which might be correlated with the increased expression of stem cell factor. During osteogenic induction, hypoxia increased the expression of osteogenic genes including osteopontin, osteocalcin, and alkaline phosphatase (ALP). Moreover, hypoxia increased the mineralization and ALP levels of human pMSCs as evidenced by Alizarin Red staining and ALP staining. Upregulation of HO-1 by cobalt-protoporphyrin treatment increased the osteogenic differentiation of pMSCs under hypoxia, while inhibition of HO-1 by Zn-protoporphyrin reduced the osteogenic differentiation of hypoxic pMSCs. Taken together, our data suggest that hypoxia can promote the osteogenic differentiation of human pMSCs. Upregulation of HO-1 can further increase the osteogenesis of human pMSCs under hypoxia. Our findings will highlight the therapeutic potential of MSCs in the tissue engineering of bones.

TGF-ßl Suppresses Inflammation in Cell Therapy for Intervertebral Disc Degeneration.

Recent studies suggest that cell therapy may be an effective way to repair intervertebral disc degeneration. As a strong immune suppressor, TGF-ß1 has been shown to inhibit inflammation respond effectively. The objective of this study was to explore the effects of TGF-ß1 during bone marrow mesenchymal stem cells-based therapy for disc degeneration. In vitro assays demonstrated that co-culturing of nucleus pulposus cells with bone marrow mesenchymal stem cells resulted in significantly higher levels of TGF-ßl secretion. This increase inhibited IκB phosphorylation and NF-κB activation, detected by western blot analysis. Meanwhile, in a rabbit model, MRI analysis revealed significant recovery of signal intensity in the degenerative discs of rabbits receiving cells transplantation, than receiving cells treated with a TGF-ß1 inhibitor or saline. These findings indicated that enhanced TGF-ß1 production recovered the degeneration of intervertebral disc. And also immunohistochemical staining detected enhanced collagen II expression in the rabbits treated with cell transplantation. However, the NF-κB positive cells were significantly less than other two control groups. Thus, cell therapy promoted TGF-ß1 expression in nucleus pulposus, leading to anti-inflammatory effects via the inhibition of NF-κB, and the amelioration of disc degradation due to increased expression of collagen II and aggrecan in degenerative intervertebral disc.

Curcumin attenuated acute Propionibacterium acnes-induced liver injury through inhibition of HMGB1 expression in mice.

Curcumin is a phenolic product isolated from the rhizome of Curcuma longa and has protective effects on inflammatory diseases. Here we investigated the protective effect of curcumin in acute Propionibacterium acnes (P. acnes)-induced inflammatory liver injury. C57BL/6 mice were primed with P. acnes followed by LPS challenge to induce fulminant hepatitis. Curcumin or vehicle control was administered perorally by gavage once daily starting 2days before P. acnes priming. We found that curcumin significantly improved mouse mortality. Then, to investigate the underlying mechanisms of curcumin in this acute inflammatory liver injury model, we primed C57BL/6 mice with P. acnes only. We found that curcumin treatment attenuated P. acnes-induced liver injury as evidenced by decreased production of ALT. In addition, curcumin treatment reduced the production of proinflammatory cytokines such as TNF-α and IFN-γ, accompanied by reduced hepatocyte apoptosis. Furthermore, curcumin treatment significantly reduced HMGB1 cytoplasmic translocation and expression by down-regulating acetylation of lysine. Taken together, our results suggest that curcumin protects mice from P. acnes-induced liver injury through reduction of HMGB1 cytoplasmic translocation and expression.

Collagen membrane alleviates peritendinous adhesion in the rat Achilles tendon injury model.

BACKGROUND: Tendon adhesion is one of the most common causes of disability following tendon surgery. Therefore, prevention of peritendinous adhesion after surgical repair of tendon is a major challenge. The aim of this study was to explore the possible application of a collagen membrane for the prevention or attenuation of peritendinous adhesions. METHODS: Sprague-Dawley (SD) rat Achilles tendon was cut and sutured by a modified Kessler's technique with or without the collagen membrane wrapped. Macroscopic, morphological and biomechanical evaluations were applied to examine the recovery of the injured tendon at 4 and 8 weeks after surgery. RESULTS: The surgery group wrapped by collagen membranes had a better outcome than the group with surgery repair only. In the collagen membrane-treated group, less adhesion appeared, stronger tensile strength was detected, and more tendon fibers and collagen I expression were observed morphologically. CONCLUSION: Wrapping the tendon with a collagen membrane may be an efficient approach for tendon repair and preventing tendon adhesion after its ruptures.

The role of TLR and chemokine in wear particle-induced aseptic loosening.

Wear particle-induced periprosthetic osteolysis remains the principal cause of aseptic loosening of orthopaedic implants. Monocytes/macrophages phagocytose wear particles and release cytokines that induce inflammatory response. This response promotes osteoclast differentiation and osteolysis. The precise mechanisms by which wear particles are recognized and induce the accumulation of inflammatory cells in the periprosthetic tissue have not been fully elucidated. Recent studies have shown that toll-like receptors (TLRs) contribute to the cellular interaction with wear particles. Wear particles are recognized by monocytes/macrophages through TLRs coupled with the adaptor protein MyD88. After the initial interaction, wear particles induce both local and systemic migration of monocytes/macrophages to the periprosthetic region. The cellular migration is mediated through chemokines including interleukin-8, macrophage chemotactic protein-1, and macrophage inhibitory protein-1 in the periprosthetic tissues. Interfering with chemokine-receptor axis can inhibit cellular migration and inflammatory response. This paper highlights recent advances in TLR, and chemokine participated in the pathogenesis of aseptic loosening. A comprehensive understanding of the recognition and migration mechanism is critical to the development of measures that prevent wear particle-induced aseptic loosening of orthopaedic implants.

Curcumin increases rat mesenchymal stem cell osteoblast differentiation but inhibits adipocyte differentiation.

BACKGROUND: Curcumin is a phenolic natural product isolated from the rhizome of Curcuma longa (turmeric) and has effects on bone health and fat formation. The bone marrow mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into osteoblasts and adipocytes. Osteoblast differentiation of MSCs can be a result of upregulation of heme oxygenase (HO)-1 expression. Curcumin can potently induce HO-1 expression. OBJECTIVE: The present study describes the effects of curcumin on rat MSC (rMSCs) differentiation into osteoblasts and adipocytes. MATERIALS AND METHODS: Rat bone marrow MSCs were isolated and treated with or without curcumin. Osteoblast differentiation was confirmed and determined by alkaline phosphatase (ALP) activity, mineralized nodule formation, the expression of Runx2 (runt-related transcription factor 2) and osteocalcin. Adipocyte differentiation was determined by Oil red O staining and the expression of peroxisome proliferator-activated receptor-γ 2 (PPARγ2) and CCAAT/enhancer-binding protein (C/EBP) α. RESULTS: Curcumin increased ALP activity and osteoblast-specific mRNA expression of Runx2 and osteocalcin when rMSCs were cultured in osteogenic medium. In contrast, curcumin decreased adipocyte differentiation and inhibited adipocyte-specific mRNA expression of PPARγ2 and C/EBPα when rMSCs were cultured in adipogenic medium. HO-1 expression was increased during osteogenic differentiation of rMSCs. CONCLUSIONS: These findings demonstrate that curcumin can promote osteogenic differentiation of rMSCs and inhibit adipocyte formation. The effect of curcumin on osteogenic differentiation of rMSCs is correlated with HO-1 expression.

Heme oxygenase-1 alleviates mouse hepatic failure through suppression of adaptive immune responses.

Heme oxygenase-1 (HO-1) has protective effects on liver damage induced by noxious stimuli. The mechanism of action of HO-1 is not well understood. In the present study, we investigate the effect of HO-1 in a model of fulminant hepatic failure induced by Propionibacterium acnes and lipopolysaccharide (LPS). The expression of HO-1 mRNA and protein in the liver was increased after repeated administration of the HO-1 inducer cobalt protoporphyrin IX. We found that HO-1 protected mice from acute liver damage induced by P. acnes/LPS and prolonged survival. On the contrary, administration of the HO-1 inhibitor zinc protoporphyrin IX increased liver damage induced by P. acnes/LPS. Subsequently, to investigate the underlying mechanisms of HO-1 in the acute liver injury model, we primed mice with P. acnes only. We found that the expression of HO-1 mRNA and protein in dendritic cells (DCs) was increased after the administration of cobalt protoporphyrin IX. HO-1 decreased the mature markers major histocompatibility complex II and CD80 on liver DCs. The expression of CCR7, CCL2, and CCL22 mRNA, which are expressed by mature DCs, was also reduced. These liver DCs could not efficiently stimulate CD4+ T cell activation and proliferation. Consequently, HO-1 inhibited the activation, proliferation, and T helper 1 polarization of liver-infiltrating CD4+ T cells and reduced the production of serum alanine aminotransferase and proinflammatory cytokines such as interferon-γ and tumor necrosis factor-α. Taken together, our data suggest that HO-1 alleviates P. acnes/LPS-induced fulminant hepatic failure, probably by inhibiting DC-induced adaptive responses.

Therapeutic effect of MIP-1alpha-recruited dendritic cells on preestablished solid and metastatic tumors.

We previously found that dendritic cell (DC) precursors could be recruited into the peripheral blood of B6 mice by administration of macrophage inflammatory protein (MIP)-1alpha. These MIP-1alpha-recruited DCs could induce anti-tumor protective immunity when pulsed with tumor cell lysate. In this study, MIP-1alpha-recruited DCs could not effectively suppress preestablished tumor when pulsed with B16 tumor cell lysate. However, inoculation with these DCs expressing MAGE-1 induced an anti-tumor immunity against preestablished solid and metastatic tumor from B16-MAGE-1 cells. These MIP-1alpha-recruited DCs expressed higher level of CCR7 and displayed a more significant chemotactic response toward secondary lymphoid tissue. Therefore, they are superior in the induction of cytotoxic T lymphocytes and the inhibition of tumor development and metastasis than bone marrow-derived DCs. This study established a novel approach to the treatment of preestablished solid and metastatic tumors using MIP-1alpha-recruited DCs transduced with tumor antigen gene.

18Beta-glycyrrhetinic acid ameliorates acute Propionibacterium acnes-induced liver injury through inhibition of macrophage inflammatory protein-1alpha.

18Beta-glycyrrhetinic acid (GA), the major bioactive component of licorice root extract, has a protective effect on hepatic injury and exhibits antiinflammatory activity. Here, we investigate the effect of GA in Propionibacterium acnes-induced acute inflammatory liver injury. C57BL/6 mice were primed with P. acnes followed by lipopolysaccharide challenge to induce fulminant hepatitis. GA (75 mg/kg) or vehicle control was administered intraperitoneally daily 1 day after P. acnes priming, and GA significantly improved mouse mortality. Then, to investigate the underlying mechanisms of GA in this acute inflammatory liver injury model, we primed C57BL/6 mice with P. acnes only. We propose that GA ameliorates acute P. acnes-induced liver injury through reduced macrophage inflammatory protein (MIP)-1alpha expression in Kupffer cells by down-regulating MyD88 expression and inhibiting NF-kappaB activation. Reduced MIP-1alpha expression lowered the recruitment of CD11c(+)B220(-) dendritic cell precursors into the liver. Consequently, GA treatment inhibits the activation and proliferation of liver-infiltrating CD4(+) T cells and reduces the production of serum alanine aminotransferase and proinflammatory cytokines such as interferon-gamma and tumor necrosis factor-alpha. Moreover, anti-MIP-1alpha treatment in P. acnes-primed mice inhibits the recruitment of dendritic cell precursors into the liver and suppresses mouse mortality as GA does. Taken together, our results suggest that GA exhibits antiinflammatory effects through inhibition of MIP-1alpha in a mouse model of acute P. acnes-induced inflammatory liver injury.