Hyaluronan inhibits osteoclast differentiation via Toll-like receptor 4

Mycobacterium tuberculosis escapes from the phagosomes of infected human osteoclasts reprograms osteoclast development via dysregulation of cytokines and chemokines

Spinal tuberculosis is a condition characterized by massive resorption of the spinal vertebrae due to the infection with Mycobacterium tuberculosis (Mtb). However, the pathogenesis of spinal tuberculosis has not been established because it was almost completely eradicated by the establishment of antibiotic treatment in the mid-20th century. In this study, we investigated the inflammatory responses of human multinucleated osteoclasts infected with virulent Mtb strain. We found that the intracellular Mtb infection of multinuclear osteoclasts resulted in the rapid growth of Mtb and an osteolytic response, rather than inflammation. In response to Mtb infection, the mononuclear osteoclast precursors produced proinflammatory cytokines including tumor necrosis factor (TNF)-α, an intrinsic characteristic they share with macrophages. In contrast, highly fused multinucleated osteoclasts incapacitated the production of these cytokines. Instead, the intracellular Mtb inside multinuclear osteoclasts escaped from the endosome/phagosome, leading to a different pattern of osteoclast activation, with the production of chemokines such as CCL5, CCL17, CCL20, CCL22, CCL24, and CCL25. Moreover, intracellular infection with an avirulent Mtb strain resulted in diminished production of these chemokines. These findings indicate that intracellular Mtb infection in multinuclear osteoclasts reprograms osteoclast development via the dysregulation of cytokines and chemokines.

Toll-like receptor signaling pathways in cardiovascular diseases: challenges and opportunities

Toll-like receptors (TLRs), a family of surface molecules, are involved in innate immune responses. Recent studies indicated that TLRs play a critical role in inflammatory responses to exogenous and endogenous triggers. This article focuses on probable effects of TLRs in the morbidity of cardiovascular events, e.g., ischemic reperfusion (I/R) injury and atherosclerosis. TLR2 and TLR4 have been shown to have the most fundamental role in promoting cytokine production and subsequent inflammatory damages in these states. Blockade of these receptors may be beneficial in both preventing the occurrence and decreasing the complications in cardiovascular events. However, controversies exist on the certainty of this beneficial effect; therefore, additional studies are needed.

New insights into adhesion signaling in bone formation

Mineralized tissues that are protective scaffolds in the most primitive species have evolved and acquired more specific functions in modern animals. These are as diverse as support in locomotion, ion homeostasis, and precise hormonal regulation. Bone formation is tightly controlled by a balance between anabolism, in which osteoblasts are the main players, and catabolism mediated by the osteoclasts. The bone matrix is deposited in a cyclic fashion during homeostasis and integrates several environmental cues. These include diffusible elements that would include estrogen or growth factors and physicochemical parameters such as bone matrix composition, stiffness, and mechanical stress. Therefore, the microenvironment is of paramount importance for controlling this delicate equilibrium. Here, we provide an overview of the most recent data highlighting the role of cell-adhesion molecules during bone formation. Due to the very large scope of the topic, we focus mainly on the role of the integrin receptor family during osteogenesis. Bone phenotypes of some deficient mice as well as diseases of human bones involving cell adhesion during this process are discussed in the context of bone physiology.

Toll-like receptor signaling in liver ischemia and reperfusion

Liver ischemia-reperfusion (I/R) injuries are significant clinical challenges implicated in various hepatic surgical procedures and transplantations. Associated with varying degrees of insult, the hallmark of I/R is the excessive inflammatory response potentiated by the host immune system. Toll-like receptors (TLRs), known to play an important role in pathogen-derived inflammation, are now thought to participate in I/R injury-derived inflammation signaling pathways. Endogenous particles (proteins, cytokines, nucleic acids) that are released from damaged host cells bind to TLR2, TLR4, and TLR9, resulting in even further injury by subsequent inflammatory reactions and activation of the innate immune system. This review aims to systematically examine the current literature about TLR signaling mechanisms, allowing for a greater understanding of the precise role of TLRs in hepatic I/R injuries.

Characterization of recombinant human bone morphogenetic protein-2 delivery from injectable hyaluronan-based hydrogels by means of 125I-radiolabelling

This study presents a thorough in vitro and in vivo characterization of the delivery of bone morphogenetic protein 2 (BMP-2) from a hyaluronan-based hydrogel system. The in vitro release of BMP-2 from similar hydrogels has previously been studied by enzyme-linked immunosorbent assay (ELISA), by which only a fraction of the loaded protein is detected. In the current study, (125) I radiolabelling was used instead to monitor BMP-2 in vitro and in vivo. To minimize protein loss during handling, (125) I-BMP-2 adsorption to different tubes was studied at different times and temperatures. The data showed that Protein LoBind tubes exhibited the lowest protein affinity. Furthermore, a biphasic release profile of biologically active BMP-2 was observed both in vitro and in vivo, with the initial fast phase during the first week, followed by a slower release during the remaining 3 weeks. The initial fast-release phase corresponded to the early bone formation observed after 8 days in an ectopic model in rats. Bone volume and mineral content increased until day 14, after which a decrease in bone volume was observed, possibly due to resorption in response to decreased amounts of released BMP-2. Overall, the results suggested that cautious protein handling and a reliable quantification technique are essential factors for successful design of a BMP-2 delivery system.

Hyaluronic acid-based hydrogels functionalized with heparin that support controlled release of bioactive BMP-2

Bone morphogenetic protein-2 (BMP-2) is a potent osteoinductive factor, yet its clinical use is limited by a short biological half-life, rapid local clearance and propensity for side effects. Heparin (HP), a highly sulfated glycosaminoglycan (GAG) that avidly binds BMP-2, has inherent biological properties that may circumvent these limitations. Here, we compared hyaluronan-based hydrogels formulated to include heparin (Heprasil™) with similar gels without heparin (Glycosil™) for their ability to deliver bioactive BMP-2 in vitro and in vivo. The osteogenic activity of BMP-2 released from the hydrogels was evaluated by monitoring alkaline phosphatase (ALP) activity and SMAD 1/5/8 phosphorylation in mesenchymal precursor cells. The osteoinductive ability of these hydrogels was determined in a rat ectopic bone model by 2D radiography, 3D μ-CT and histological analyses at 8 weeks post-implantation. Both hydrogels sustain the release of BMP-2. Importantly, the inclusion of a small amount of heparin (0.3% w/w) attenuated release of BMP-2 and sustained its osteogenic activity for up to 28 days. In contrast, hydrogels lacking heparin released more BMP-2 initially but were unable to maintain BMP-2 activity at later time points. Ectopic bone-forming assays using transplanted hydrogels emphasized the therapeutic importance of the initial burst of BMP-2 rather than its long-term osteogenic activity. Thus, tuning the burst release phase of BMP-2 from hydrogels may be advantageous for optimal bone formation.

Interleukin-34 produced by human fibroblast-like synovial cells in rheumatoid arthritis supports osteoclastogenesis

Introduction

Interleukin-34 (IL-34) is a recently defined cytokine, showing a functional overlap with macrophage colony stimulating factor (M-CSF). This study was undertaken to address the expression of IL-34 in rheumatoid arthritis (RA) patients and to investigate its regulation and pathogenic role in RA.

Methods

IL-34 levels were determined in the RA synovium, synovial fluid (SF) and fibroblast-like synovial cells (FLS) by immunohistochemistry, real-time PCR, enzyme-linked immunosorbent assay and immunoblotting. RA activity was assessed using Disease Activity Score 28 (DAS28) activity in the plasma collected at baseline and one year after treatment. Conditioned media (CM) were prepared from RA FLS culture with tumor necrosis factor alpha (TNFα) for 24 hours and used for functional assay.

Results

IL-34 was expressed in the synovium, SF, and FLS from RA patients. The production of IL-34 in FLS was up-regulated by TNFα in RA samples compared with osteoarthritis (OA) patients. Importantly, the preferential induction of IL-34 rather than M-CSF by TNFα in RAFLS was mediated by the transcription factor nuclear factor kappa B (NF-κB) and activation of c-Jun N-terminal kinase (JNK). IL-34 elevation in plasma from RA patients was decreased after the administration of disease-modifying anti-rheumatic drugs (DMARDs) in accordance with a decrease in DAS28. CM from RAFLS cultured with TNFα promoted chemotactic migration of human peripheral blood mononuclear cells (PBMCs) and subsequent osteoclast (OC) formation, effects that were attenuated by an anti-IL-34 antibody.

Conclusions

These data provide novel information about the production of IL-34 in RA FLS and indicate that IL-34 is an additional osteoclastogenic factor regulated by TNFα in RA, suggesting a discrete role of IL-34 in inflammatory RA diseases.

Proteoglycans and osteolysis

Osteolysis is a complex mechanism resulting from an exacerbated activity of osteoclasts associated or not with a dysregulation of osteoblast metabolism leading to bone loss. This bone defect is not compensated by bone apposition or by apposition of bone matrix with poor mechanical quality. Osteolytic process is regulated by mechanical constraints, by polypeptides including cytokines and hormones, and by extracellular matrix components such as proteoglycans (PGs) and glycosaminoglycans (GAGs). Several studies revealed that GAGs may influence osteoclastogenesis, but data are very controversial: some studies showed a repressive effect of GAGs on osteoclastic differentiation, whereas others described a stimulatory effect. The controversy also affects osteoblasts which appear sometimes inhibited by polysaccharides and sometimes stimulated by these compounds. Furthermore, long-term treatment with heparin leads to the development of osteoporosis fueling the controversy. After a brief description of the principal osteoclastogenesis assays, the present chapter summarizes the main data published on the effect of PGs/GAGs on bone cells and their functional incidence on osteolysis.

High and low molecular weight hyaluronic acid differentially regulate human fibrocyte differentiation

Background

Following tissue injury, monocytes can enter the tissue and differentiate into fibroblast-like cells called fibrocytes, but little is known about what regulates this differentiation. Extracellular matrix contains high molecular weight hyaluronic acid (HMWHA; ∼2×10⁶ Da). During injury, HMWHA breaks down to low molecular weight hyaluronic acid (LMWHA; ∼0.8–8×10⁵ Da).

Methods and Findings

In this report, we show that HMWHA potentiates the differentiation of human monocytes into fibrocytes, while LMWHA inhibits fibrocyte differentiation. Digestion of HMWHA with hyaluronidase produces small hyaluronic acid fragments, and these fragments inhibit fibrocyte differentiation. Monocytes internalize HMWHA and LMWHA equally well, suggesting that the opposing effects on fibrocyte differentiation are not due to differential internalization of HMWHA or LMWHA. Adding HMWHA to PBMC does not appear to affect the levels of the hyaluronic acid receptor CD44, whereas adding LMWHA decreases CD44 levels. The addition of anti-CD44 antibodies potentiates fibrocyte differentiation, suggesting that CD44 mediates at least some of the effect of hyaluronic acid on fibrocyte differentiation. The fibrocyte differentiation-inhibiting factor serum amyloid P (SAP) inhibits HMWHA-induced fibrocyte differentiation and potentiates LMWHA-induced inhibition. Conversely, LMWHA inhibits the ability of HMWHA, interleukin-4 (IL-4), or interleukin-13 (IL-13) to promote fibrocyte differentiation.

Conclusions

We hypothesize that hyaluronic acid signals at least in part through CD44 to regulate fibrocyte differentiation, with a dominance hierarchy of SAP>LMWHA≥HMWHA>IL-4 or IL-13.

Calcium phosphates compounds in conjunction with hydrogel as carrier for BMP-2: a study on ectopic bone formation in rats

Current treatment of fractures often involves the use of bone graft or bone morphogenetic proteins (BMP) to induce fracture healing, especially in patients with a compromised healing capacity. BMP has to be delivered in conjunction with a carrier. Unfortunately, there are drawbacks and limitations with current carriers, including their bovine origin which carries the risk of an immunological response. The physical properties also limit the use to open surgical procedures, as it cannot be injected. New carriers with improved properties are therefore needed. The aim of this study was to assess the ectopic bone forming capability of various calcium phosphate compounds when used in conjunction with a hydrogel as the carrier for BMP-2. Five different ceramic additives were tested, including β-tricalcium phosphate and four types of hydroxyapatite (HAP) (nanoHAP, HAP, clods of HAP >100 μm, and the biomimetic HAP Ostim35®). The compounds were injected into the thigh muscle of rats, where it formed a gel in situ. After 4 weeks bone formation was evaluated by peripheral quantitative computed tomography and histology. The major finding was that the 20 nm nanoHAP yielded a higher bone density than the other additives (P=0.0008, ANOVA with Tukey's multiple comparison test). We hypothesize that the higher bone density induced by nanoHAP might be due to nanocrystals of calcium phosphate acting as direct building blocks for biomineralization.

Coptisine inhibits RANKL-induced NF-κB phosphorylation in osteoclast precursors and suppresses function through the regulation of RANKL and OPG gene expression in osteoblastic cells

Excessive receptor activator of NF-κB ligand (RANKL) signaling causes enhanced osteoclast formation and bone resorption. The downregulation of RANKL expression and its downstream signals may be an effective therapeutic approach to the treatment of bone loss diseases such as osteoporosis. Here, we found that coptisine, one of the isoquinoline alkaloids from Coptidis Rhizoma, exhibited inhibitory effects on osteoclastogenesis in vitro. Although coptisine has been studied for its antipyretic, antiphotooxidative, dampness dispelling, antidote, antinociceptive, and anti-inflammatory activities in vitro and in vivo, its effects on osteoclastogenesis have not been investigated. Therefore, we evaluated the effects of coptisine on osteoblastic cells as well as osteoclast precursors for osteoclastogenesis in vitro. The addition of coptisine to cocultures of mouse bone marrow cells and primary osteoblastic cells with 10(-8) M 1α,25(OH)(2)D(3) caused significant inhibition of osteoclast formation in a dose-dependent manner. Reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed that coptisine inhibited RANKL gene expression and stimulated the osteoprotegerin gene expression induced by 1α,25(OH)(2)D(3) in osteoblastic cells. Coptisine strongly inhibited RANKL-induced osteoclast formation when added during the early stage of bone marrow macrophage (BMM) cultures, suggesting that it acts on osteoclast precursors to inhibit RANKL/RANK signaling. Among the RANK signaling pathways, coptisine inhibited NF-κB p65 phosphorylations, which are regulated in response to RANKL in BMMs. Coptisine also inhibited the RANKL-induced expression of NFATc1, which is a key transcription factor. In addition, 10 μM coptisine significantly inhibited both the survival of mature osteoclasts and their pit-forming activity in cocultures. Thus, coptisine has potential for the treatment or prevention of several bone diseases characterized by excessive bone destruction.

Intra-articular injection of hyaluronan restores the aberrant expression of matrix metalloproteinase-13 in osteoarthritic subchondral bone

Subchondral bone is a candidate for treatment of osteoarthritis (OA). We investigated the effects of intra-articular injection of hyaluronan (IAI-HA) on subchondral bone in rabbit OA model. OA was induced by anterior cruciate ligament transection, with some rabbits receiving IAI-HA. OA was graded morphologically, and expression of mRNA was assessed by real-time RT-PCR. Tissue sections were stained with hyaluronan-binding protein, and penetration of fluorescent hyaluronan was assessed. The in vitro inhibitory effect of hyaluronan on MMP-13 was analyzed in human osteoarthritic subchondral bone osteoblasts (OA Ob) by real-time RT-PCR and ELISA. Binding of hyaluronan to OA Ob via CD44 was assessed by immunofluorescence cytochemistry. Expression of MMP-13 and IL-6 mRNA in cartilage and subchondral bone, and morphological OA grade, increased over time. IAI-HA ameliorated the OA grade and selectively suppressed MMP-13 mRNA in subchondral bone. IAI-HA enhanced the hyaluronan staining of subchondral bone marrow cells and osteocyte lacunae. Fluorescence was observed in the subchondral bone marrow space. In OA Ob, hyaluronan reduced the expression and production of MMP-13, and anti-CD44 antibody blocked hyaluronan binding to OA Ob. These findings indicate that regulation of MMP-13 in subchondral bone may be a critical mechanism during IAI-HA.

Bone reservoir: Injectable hyaluronic acid hydrogel for minimal invasive bone augmentation

A strategy has been designed to develop hyaluronic acid (HA) hydrogel for in vivo bone augmentation using minimal invasive technique. A mild synthetic procedure was developed to prepare aldehyde modified HA by incorporating an amino-glycerol side chain via amidation reaction and selective oxidation of the pendent group. This modification, upon mixing with hydrazide modified HA formed hydrazone-crosslinked hydrogel within 30s that was stable at physiological pH. In vitro experiments showed no cytotoxicity of hydrogel with the controlled release of active bone morphogenic protein-2 (BMP-2). In vivo evaluation of this gel as a BMP-2 carrier was performed by injecting gels over the rat calvarium and showed bone formation in 8 weeks in correlation with the amount of BMP-2 loaded (0, 1 and 30μg) within the gel. Furthermore, hydrogels with 30μg of BMP-2 induced less bone formation upon subcutaneous injection in comparison with subperiosteal implantation. Histological examination showed newly formed bone with a high expression of osteocalcin, osteopontin and with angiogenic bone marrow when higher BMP-2 concentration was employed. Our result suggests that novel HA hydrogels could be used as a BMP-2 carrier and can promote bone augmentation for potential orthopedic applications.

Blood-derived human osteoclast resorption activity is impaired by Hyaluronan-CD44 engagement via a p38-dependent mechanism

The control of bone resorption is crucial in osteolytic diseases. Once attached to bone, osteoclasts (OCs) initiate the resorption process through the activation of a complex cascade of morphological and biochemical changes. Hyaluronan (HA), an extracellular glycosaminoglycan long non-branching polysaccharide, is expressed in bone matrices. Here we demonstrate that HA counter-balances the erosion activity of human mature OCs by significantly reducing their degradative potential. HA treatment of fully differentiated OCs derived from human peripheral blood monocytes inhibited migration on collagen as well as bone resorption. HA-mediated effects were primarily due to TRAcP, MMP-9, and cathepsin K down-regulation and to the increased levels of TIMP-1, a natural MMP-9 inhibitor. Binding of HA to mature OCs was entirely mediated by CD44: function-blocking anti-CD44 antibodies fully abrogated HA effects, and the engagement of HA receptor caused a rapid de-phosphorylation of Ser325 in the CD44 cytoplasmic tail. The inhibitory action by HA was associated with a transient up-phosphorylation of Pyk2, a novel persistent phosphorylation of p38 and the down-regulation of NFATc1 transcription factor. Our results provide a direct evidence for the involvement of CD44 in the HA-dependent regulation of OC activity and suggest a signaling pathway that could be unique in OC function inhibition.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

A novel isoform of microphthalmia-associated transcription factor inhibits IL-8 gene expression in human cervical stromal cells

Cervical ripening during pregnancy is a profound change in cervix structure and function characterized by increases in the proinflammatory cytokine IL-8 and dissolution of the cervical extracellular matrix. Relatively little is known about the molecular mechanisms that underlie these events. Here, we report identification of a novel isoform of micropthalmia-associated transcription factor in human cervical stromal cells (MiTF-CX) that is down-regulated 12-fold during cervical ripening and that represses expression of IL-8. Ectopic expression of MiTF-CX in human cervical stromal cells resulted in substantial suppression of endogenous IL-8 mRNA and protein expression, whereas expression of dominant negative MiTF-CX mutants with impaired DNA binding resulted in dramatic increases in IL-8 production. Gel shift, reporter gene, and chromatin immunoprecipitation assays revealed one strong binding site (E-box (-397) CACATG(-391)) in the human IL-8 promoter that was crucial for mediating transcriptional repression by MiTF-CX. Moreover, we show that MiTF-CX expression in the cervix was itself positively autoregulated via two E-box motifs within a 2.1-kb promoter fragment. We therefore propose that maintenance of cervical competency during pregnancy is an active process maintained through suppression of IL-8 by the transcription factor MiTF-CX. During cervical ripening, loss of MiTF-CX would result in significant up-regulation of IL-8 mRNA and protein synthesis, thereby leading to recruitment and activation of leukocytes within the cervix and dissolution of the extracellular matrix.

Inhibition of osteoclastogenic differentiation by Ikarisoside A in RAW 264.7 cells via JNK and NF-kappaB signaling pathways

Osteoclasts are specialized bone-resorbing cells derived from multipotent myeloid progenitor cells. They play a crucial homeostatic role in skeletal modeling and remodeling and destroy bone in many pathologic conditions. Receptor activator of NF-kappaB ligand (RANKL) is essential to osteoclastogenesis. In this study, we investigated the effects of Ikarisoside A, isolated from Epimedium koreanum (Berberidaceae), on osteoclastogenesis in RANKL-treated murine monocyte/macrophage RAW 264.7 cells. The results indicate that Ikarisoside A is a potent inhibitor of osteoclastogenesis in RANKL-stimulated RAW 264.7 cells as well as in bone marrow-derived macrophages. The inhibitory effect of Ikarisoside A resulted in decrease of osteoclast-specific genes like matrix metalloproteinase 9 (MMP9), tartrate-resistant acid phosphatase (TRAP), receptor activator of NF-kappaB (RANK), and cathepsin K. Moreover, Ikarisoside A blocked the resorbing capacity of RAW 264.7 cells on calcium phosphate-coated plates. Ikarisoside A also has inhibitory effects on the RANKL-mediated activation of NF-kappaB, JNK, and Akt. Finally, Ikarisoside A clearly decreased the expression of c-Fos and nuclear factor of activated T cells c1 (NFATc1) as well as the transcriptional activity of NFATc1, the master regulator of osteoclast differentiation. The data indicate that Ikarisoside A has potential for use in treatment of diseases involving abnormal bone lysis such as osteoporosis, rheumatoid arthritis, and periodontal bone erosion.

IFNgamma primes macrophages for inflammatory activation by high molecular weight hyaluronan

The objective was to assess outcomes of IFNgamma-priming upon macrophage activation by the synovial macromolecule high molecular weight hyaluronan [HMW-HA] in the context of rheumatoid arthritis inflammation. Human macrophages primed by IFNgamma and activated by HMW-HA were evaluated for cytokine secretion by ELISA and Milliplex assay and activation profiles by nuclear transcription factor EIA. IFNgamma-primed, HMW-HA-activated macrophages produced elevated levels of TNF and secreted the TH1 cytokine IL-12p70, while IFNgamma suppressed HMW-HA-induced secretion of the regulatory cytokine IL-10 and activation of the transcription factor c-Jun. IFNgamma modulates the HMW-HA-induced cytokine response profile promoting macrophage activation and inflammatory TH1 cytokine secretion.

Potential role of cathepsin K in the pathophysiology of mucopolysaccharidoses

Cathepsin K, a papain-like cysteine protease, is highly expressed in osteoclasts and plays a critical role in bone resorption. Dysfunction of the enzyme leads to various skeletal abnormalities. The recent knowledge that the collagenolytic activity of cathepsin K depends on interactions with bone and cartilage-resident glycosaminoglycans (GAGs) may shed some light on diseases such as mucopolysaccharidoses (MPSs). MPSs are a group of lysosomal storage diseases characterized by the accumulation of GAGs in tissues including bone. Typical pathological features of these diseases include skeletal abnormalities such as dysostosis multiplex, short stature, and multiple irregularities in bone development. We describe how further investigation of the cathepsin K/GAG complexes could provide valuable insights into the bone pathology associated with MPS diseases. In this review, we discuss the inhibition of osteoclast function through altered activity of cathepsin K by GAGs and offer insight into a mechanism for the bone pathology seen in MPS patients.

Hexane-Soluble Fraction of the Common Fig, Ficus carica, Inhibits Osteoclast Differentiation in Murine Bone Marrow-Derived Macrophages and RAW 264.7 Cells

Osteoclasts, derived from multipotent myeloid progenitor cells, play homeostatic roles in skeletal modeling and remodeling, but may also destroy bone in pathological conditions such as osteoporosis and rheumatoid arthritis. Osteoclast development depends critically on a differentiation factor, the receptor activator of NF-kappaB ligand (RANKL). In this study, we found that the hexane soluble fraction of the common fig Ficus carica (HF6-FC) is a potent inhibitor of osteoclastogenesis in RANKL-stimulated RAW264.7 cells and in bone marrow-derived macrophages (BMMs). HF6-FC exerts its inhibitory effects by suppression of p38 and NF-kappaB but activation of ERK. In addition, HF6-FC significantly decreased the expression of NFATc1 and c-Fos, the master regulator of osteoclast differentiation. The data indicate that components of HF6-FC may have therapeutic effects on bone-destructive processes such as osteoporosis, rheumatoid arthritis, and periodontal bone resorption.

In situ cross-linkable high molecular weight hyaluronan-bisphosphonate conjugate for localized delivery and cell-specific targeting: a hydrogel linked prodrug approach

We present here a novel synthesis route to functionalize high molecular weight hyaluronan (HMW-HA) with a hydrazide group and a bioactive ligand, namely bisphosphonate (BP). For this purpose, a new symmetrical self-immolative biscarbazate linker has been devised. The hydrazide group was used to form hydrazone cross-linked hydrogel upon treating with previously described aldehyde modified hyaluronan. The 1:1 weight ratio of these two polymers gave hydrogel in less than 30 s. In this communication we present the first in vitro results showing that even though HA can target CD44 positive cancer cells (HCT-116), receptor mediated endocytosis could only occur by cleavage of high molecular weight HA with an ubiquitous enzyme, hyaluronidase (Hase). The cancer cells are known to overexpress CD44 receptors and also increase the hyaluronidase activity in vivo. Thus the pro-drug design, based on drug conjugation to HMW-HA, represents a new drug delivery platform where the drug potency is triggered by Hase mediated degradation of the HA-drug conjugate. We have successfully demonstrated that the cross-linkable HA-BP conjugate first undergoes Hase-mediated scission to the fragments of suitable sizes so as to be internalized by CD44 positive cells. The specificity of this targeting was proven by comparing the results with less CD44 positive HEK-293T cells. The localized delivery of such drugs at the surgical resection site opens up avenues to control tumor recurrence after removal of the tumor. In the form of hydrogel it would prevent systemic exposure of the drug and would allow its controlled release.

Toll-like receptors in ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injuries are implicated in a large array of pathological conditions such as myocardial infarction, cerebral stroke, and hepatic, renal, and intestinal ischemia, as well as following cardiovascular and transplant surgeries. The hallmark of these pathologies is excessive inflammation. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. Endogenous ligands such as low-molecular hyaluronic acid, fibronectin, heat shock protein 70, and heparin sulfate were all found to be cleaved in the inflamed tissue and to activate TLR2 and TLR4, initiating an inflammatory response even in the absence of pathogens and infiltrating immune cells. In this review, we discuss the contribution of TLR activation in hepatic, renal, cerebral, intestinal, and myocardial I/R injuries. A greater understanding of the role of TLRs in I/R injuries may aid in the development of specific TLR-targeted therapeutics to treat these conditions.

Enhanced inhibitory effects of a novel CpG motif on osteoclast differentiation via TREM-2 down-regulation

Recognition of oligodeoxynucleotides containing CpG motifs (CpG-ODNs) by toll-like receptor 9 (TLR9) inhibits RANKL-induced osteoclastogenesis from precursors. This inhibitory effect suggests the possibility of using this strategy to block pathological bone loss. However, the enhancing effect of CpG-ODNs on OC formation from RANKL-primed pre-osteoclasts (pOCs) has hampered their clinical use. In this report, we developed a CpG-KSK13 oligonucleotide with an alternative CpG motif, and tested its effect on osteoclastogenesis in comparison with previously used murine CpG motif (CpG-1826) or human CpG motif (CpG-2006) oligonucleotides. Murine CpG-1826 inhibited RANKL-induced OC formation from BMMs but not from RANKL-primed pOCs, while CpG-KSK13 treatment strongly inhibited OC formation from both BMM and primed pOC cells. CpG-KSK13 also showed a potent inhibitory effect on human OC differentiation using peripheral blood mononuclear cells (PBMCs), which was in contrast to the species-specific response of murine CpG-1826 or human CpG-2006. Moreover, CpG-KSK13 effectively inhibited NFATc1 activity, but not NF-kappaB or AP-1 activity, and decreased TREM-2 promoter activity and subsequent surface expression of the TREM-2 protein induced by M-CSF and RANKL. These results demonstrate that the recognition of CpG-KSK13 via TLR9 inhibits osteoclastogenesis by down-regulating TREM-2 expression. Thus, our findings provide evidence for the potential use of CpG-KSK13 as an anti-osteoclastogenic agent for human and for pre-clinical animals.

Impaired osteoclastogenesis by staphylococcal lipoteichoic acid through Toll-like receptor 2 with partial involvement of MyD88

Degenerative bone disease, marked by excessive loss of calcified matrix, is often associated with bacterial infections. Osteoclasts, which mediate the bone-resorptive process, are derived mainly from myeloid precursor cells of the monocyte/macrophage lineage, from which cells with phagocytic and inflammatory capacities may alternatively arise. Here, we investigated the effect of LTA, a major cell-wall virulence factor of Gram-positive bacteria, on osteoclast differentiation. Osteoclast precursors were prepared from C57BL/6 mouse BM using M-CSF and RANKL. When osteoclastogenesis was induced in the presence of staphylococcal LTA, LTA dose-dependently inhibited the differentiation of osteoclast precursors to mature osteoclasts. A corresponding inhibition of bone-resorptive function was observed in the reduced resorption area on calcium phosphate-coated culture plates. In contrast, the phagocytic and inflammatory potential of the osteoclast precursors increased in the presence of LTA. TLR2, known to recognize LTA, might be essential for the LTA inhibition of osteoclastogenesis, as the inhibition did not occur in the precursors from TLR2-deficient mice. Importantly, MyD88-dependent and MyD88-independent pathways would participate in the inhibition, as determined using MyD88-deficient cells. Moreover, LTA inhibited phosphorylation of ERK and JNK in osteoclast precursors stimulated with M-CSF and RANKL, concomitantly with a decreased DNA-binding activity of AP-1. These results suggest that staphylococcal LTA inhibits osteoclast differentiation primarily through TLR2 but also in part through MyD88 signaling, which in turn, inhibits activation of ERK, JNK, and AP-1.

New trends in face rejuvenation by hyaluronic acid injections

BACKGROUND

Injection techniques are growing, thanks to safer and more suitable filling agents. Hyaluronic acid (HA), a biodegradable product, has become the "gold standard" for fillers. With its wide range, it not only improves wrinkles but also restores volume.

METHODS

Since 1996, many patients have been injected for wrinkles, fine lines, and nasolabial folds. For 3 years, more viscous HAs have been launched, allowing us to restore volumes. Some new procedures are described. These can correct anomalies of the chin and of the nose, and allow a betterment of the periocular area by correcting hollow and falling eyebrows.

RESULTS

The use of different HAs for each area and indication is suitable and offers real possibilities to rejuvenate the skin without downtime. Longevity of the correction depends on treated areas, HA used, and on the individual.

CONCLUSION

HAs are safe and suitable for wrinkles and volume restoration, but besides their mechanical properties, they have numerous physiological functions. With the analysis of literature about the action mechanism of HA and its receptors, it is evident that HA also has a stimulating action on different physiological process.

The JNK-dependent CaMK pathway restrains the reversion of committed cells during osteoclast differentiation

Osteoclastogenesis involves the commitment of macrophage-lineage precursors to tartrate-resistant acid phosphatase-positive (TRAP+) mononuclear pre-osteoclasts (pOCs) and subsequent fusion of pOCs to form multinuclear mature osteoclasts. Despite many studies on osteoclast differentiation, little is known about the signaling mechanisms that specifically mediate the osteoclastic commitment. In this study, we found that inhibition of JNK at the pOC stage provoked reversion of TRAP(+) cells to TRAP(-) cells. The conversion to TRAP(-) cells occurred with concomitant return to the state with higher expression of macrophage antigens, and greater activity of phagocytosis and dendritic-differentiation potential. JNK inhibition at the pOC stage reduced NFATc1 and CaMK levels, and addition of active NFATc1 partially rescued the effect of JNK inhibition. In addition, the level of NFATc1 was decreased by knockdown of CaMK by RNAi and by catalytic inhibition of CaMK, which both caused the reversion of pOCs to macrophages. These data suggest that JNK activity is specifically required for maintaining the committed status during osteoclastogenesis and that the CaMK-NFATc1 pathway is the key element in that specific role of JNK.

Brain-type creatine kinase has a crucial role in osteoclast-mediated bone resorption

Osteoclasts differentiate from precursor cells of the monocyte-macrophage lineage and subsequently become activated to be competent for bone resorption through programs primarily governed by receptor activator of nuclear factor-kappaB ligand in cooperation with macrophage colony-stimulating factor. Proteins prominently expressed at late phases of osteoclastogenesis and with a supportive role in osteoclast function are potential therapeutic targets for bone-remodeling disorders. In this study, we used a proteomics approach to show that abundance of the brain-type cytoplasmic creatine kinase (Ckb) is greatly increased during osteoclastogenesis. Decreasing Ckb abundance by RNA interference or blocking its enzymatic activity with a pharmacological inhibitor, cyclocreatine, suppressed the bone-resorbing activity of osteoclasts grown in vitro via combined effects on actin ring formation, RhoA GTPase activity and vacuolar ATPase function. Activities of osteoclasts derived from Ckb-/- mice were similarly affected. In vivo studies showed that Ckb-/- mice were better protected against bone loss induced by ovariectomy, lipopolysaccharide challenge or interleukin-1 treatment than wild-type controls. Furthermore, administration of cyclocreatine or adenoviruses harboring Ckb small hairpin RNA attenuated bone loss in rat and mouse models. Our findings establish an important role for Ckb in the bone-resorbing function of osteoclasts and underscore its potential as a new molecular target for antiresorptive drug development.

CD44-epidermal growth factor receptor interaction mediates hyaluronic acid-promoted cell motility by activating protein kinase C signaling involving Akt, Rac1, Phox, reactive oxygen species, focal adhesion kinase, and MMP-2

Hyaluronic acid (HA) is known to play an important role in motility of tumor cells. However, the molecular mechanisms associated with HA-promoted melanoma cell motility are not fully understood. Treatment of cells with HA was shown to increase the production of reactive oxygen species (ROS) in a CD44-dependent manner. Antioxidants, such as N-acetyl-l-cysteine and seleno-l-methionine, prevented HA from enhancing cell motility. Protein kinase C (PKC)-alpha and PKCdelta were responsible for increased Rac1 activity, production of ROS, and mediated HA-promoted cell motility. HA increased Rac1 activity via CD44, PKCalpha, and PKCdelta. Transfection with dominant negative and constitutive active Rac1 mutants demonstrated that Rac1 was responsible for the increased production of ROS and cell motility by HA. Inhibition of NADPH oxidase by diphenylene iodonium and down-regulation of p47Phox and p67Phox decreased the ROS level, suggesting that NADPH oxidase is the main source of ROS production. Rac1 increased phosphorylation of FAK. FAK functions downstream of and is necessary for HA-promoted cell motility. Secretion and expression of MMP-2 were increased by treatment with HA via the action of PKCalpha, PKCdelta, and Rac1 and the production of ROS and FAK. Ilomastat, an inhibitor of MMP-2, exerted a negative effect on HA-promoted cell motility. HA increased interaction between CD44 and epidermal growth factor receptor (EGFR). AG1478, an inhibitor of EGFR, decreased phosphorylation of PKCalpha, PKCdelta, and Rac1 activity and suppressed induction of p47Phox and p67Phox. These results suggest that CD44-EGFR interaction is necessary for HA-promoted cell motility by regulating PKC signaling. EGFR-Akt interaction promoted by HA was responsible for the increased production of ROS and HA-promoted cell motility. In summary, HA promotes CD44-EGFR interaction, which in turn activates PKC signaling, involving Akt, Rac1, Phox, and the production of ROS, FAK, and MMP-2, to enhance melanoma cell motility.

The involvement of the Toll-like receptor family in ovulation

INTRODUCTION

Ovulation is similar to an inflammatory response and is associated with increased production of prostaglandins as well as local growth regulatory factors. However, the expression and function of innate immune cell-related genes in non-immune cells within the ovary has been reported recently and provides a novel and important regulatory system during ovulation.

DISCUSSION

Several members of the Toll-like receptor (TLR) surveillance system are expressed in granulosa cells and cumulus cells. These receptors can be activated by pathogens as well as endogenous ligands leading to the induction and release of potent cytokines and chemokines from cumulus cells.

CONCLUSION

These inflammatory factors exert potent effects on cumulus cell-oocyte expansion, ovulation, transport and fertilization indicating that ovulation is a more complex immune-inflammatory process than previously recognized.

Hyaluronan fragments generated by sperm-secreted hyaluronidase stimulate cytokine/chemokine production via the TLR2 and TLR4 pathway in cumulus cells of ovulated COCs, which may enhance fertilization

The toll-like receptor (TLR) system is expressed in cumulus cells of ovulated cumulus-oocyte complexes (COCs) and is activated by bacterial lipopolysaccharides (LPS). However, the endogenous ligand(s) for the TLRs and the physiological role(s) in ovulated COCs remain to be defined. Based on reports that hyaluronan fragments can activate TLR2 and TLR4 in macrophages, and that ovulated COCs are characterized by a hyaluronan-rich matrix, we cultured ovulated mouse COCs with purified hyaluronan fragments, treated them with purified hyaluronidase or exposed them to sperm as a physiologically relevant source of hyaluronidase. Hyaluronan fragments or hyaluronidase activated the NFkappaB pathway and induced Il6, Ccl4 and Ccl5 mRNA expression within 2 hours. Anti-TLR2 and anti-TLR4 neutralizing antibodies significantly suppressed hyaluronan fragment- and hyaluronidase-induced activation of the NFkappaB pathway and the expression of these genes. When ovulated COCs were cultured with sperm, the expression and secretion of cytokine/chemokine family members were induced in a time-dependent manner that could be blocked by TLR2/TLR4 antibodies or by a hyaluronan-blocking peptide (Pep-1). The chemokines secreted from TLR2/TLR4-stimulated COCs activated cognate chemokine receptors (CCRs) localized on sperm and induced sperm protein tyrosine phosphorylation, which was used as an index of capacitation. Significantly, in vitro fertilization of COC-enclosed oocytes was reduced by the TLR2/TLR4 neutralizing antibodies or by Pep-1. From these results, we propose that TLR2 and TLR4 present on cumulus cells were activated by the co-culture with sperm in a hyaluronan fragment-dependent manner, and that chemokines secreted from COCs induced sperm capacitation and enhanced fertilization, providing evidence for a regulatory loop between sperm and COCs during fertilization.