Recruitment and proliferation of T lymphocytes is supported by IFN?- and TNF?-activated human osteoblasts: Involvement of CD54 (ICAM-1) and CD106 (VCAM-1) adhesion molecules and CXCR3 chemokine receptor

A Multifunctional Nanostructured Hydrogel as a Platform for Deciphering Niche Interactions of Hematopoietic Stem and Progenitor Cells

For over half a century, hematopoietic stem cells (HSCs) have been used for transplantation therapy to treat severe hematologic diseases. Successful outcomes depend on collecting sufficient donor HSCs as well as ensuring efficient engraftment. These processes are influenced by dynamic interactions of HSCs with the bone marrow niche, which can be revealed by artificial niche models. Here, a multifunctional nanostructured hydrogel is presented as a 2D platform to investigate how the interdependencies of cytokine binding and nanopatterned adhesive ligands influence the behavior of human hematopoietic stem and progenitor cells (HSPCs). The results indicate that the degree of HSPC polarization and motility, observed when cultured on gels presenting the chemokine SDF-1α and a nanoscale-defined density of a cellular (IDSP) or extracellular matrix (LDV) α4β1 integrin binding motif, are differently influenced on hydrogels functionalized with the different ligand types. Further, SDF-1α promotes cell polarization but not motility. Strikingly, the degree of differentiation correlates negatively with the nanoparticle spacing, which determines ligand density, but only for the cellular-derived IDSP motif. This mechanism potentially offers a means of predictably regulating early HSC fate decisions. Consequently, the innovative multifunctional hydrogel holds promise for deciphering dynamic HSPC-niche interactions and refining transplantation therapy protocols.

Circulating immunoglobulins and transient lymphocytopenia in a sub-study of CAPRISA 012B, testing HIV monoclonal antibodies in a phase 1 trial

Acute, transient lymphocytopenia, not clinically significant was observed in the CAPRISA 012B phase 1 clinical trial following administration of broadly neutralizing antibodies (bnAb)-CAP256V2LS alone or with VRC07-523LS. Lymphocytopenia was assigned upon a > 50% decline in absolute lymphocyte counts following bnAb administration. We posited that systemic immunoglobulins (Igs), and cytokine profiles of eight women who developed lymphocytopenia were different to the 12 women without lymphocytopenia. Plasma Ig subclasses (IgG)/isotypes (IgM/IgA), and 27 cytokines were measured at enrolment (prior to bnAbs) and at days 1, 7, 28, 56 post-bnAb administration. IgG subclasses, IgM and total lymphocyte counts were significantly lower prior to bnAbs in women with gradable lymphocytopenia than those without. Gradable lymphocytopenia compared to non-lymphocytopenia women had significantly higher MIP-1β from enrolment up to day 56. TNF-α was significantly lower in gradable lymphocytopenia compared to non-lymphocytopenia women for enrolment, days 7, 28 and 56 except for day 1. Within the gradable and within the non-lymphocytopenia women, from enrolment to day 1, significantly elevated IL-6, IL-8, IP-10, MCP-1, G-CSF and IL-1RA were found. Additionally, within the gradable lymphocytopenia women, 9 additional cytokines (TNF-α, MIP-1α, MIP-1β, RANTES, Basic FGF, eotaxin, IFN-γ, IL-17A and IL-4) were significantly elevated at day 1 post-bnAbs compared to enrolment. This sub study presents preliminary findings to support the monitoring of baseline immunological markers including lymphocyte counts for assessing the development of transient lymphocytopenia. In high-risk settings conducting clinical trials testing bnAbs for HIV prevention, understanding factors that could amplify rates of lymphocytopenia, even if transient, remain undefined.

Inhibition of VEGF gene expression in osteoblast cells by different NSAIDs

OBJECTIVE

To determine the effect of different nonsteroidal anti-inflammatory drugs (NSAIDs) on vascular endothelial growth factor (VEGF) gene expression in two osteoblast cell populations.

DESIGN

Osteoblasts obtained by primary culture (HOp) and human osteosarcoma cell line MG63 (MG-63), which were treated with 10 μM doses of acetaminophen, indomethacin, ketoprofen, diclofenac, ibuprofen, ketorolac, naproxen or piroxicam. At 24 h of treatment, their gene expression of VEGF was evaluated by real-time polymerase chain reaction (RT-PCR) and compared with the expression in untreated cells (control group).

RESULTS

The treatment with the different NSAIDs significantly reduced VEGF expression regardless of the cell line and NSAID studied.

CONCLUSION

The results of this study suggest that these drugs may have undesirable effects on the osteoblast and its bone-forming capacity, given the effect of this growth factor on these cells. Further studies are warranted to determine their repercussions on bone tissue and to elucidate the cell signaling mechanism/s involved.

The link between bone microenvironment and immune cells in multiple myeloma: Emerging role of CD38

The relationship between bone and immune cells is well established both in physiological and pathological conditions. Multiple myeloma (MM) is a plasma cell malignancy characterized by an increase of number and activity of osteoclasts (OCLs) and a decrease of osteoblasts (OBs). These events are responsible for bone lesions of MM patients. OCLs support MM cells survival in vitro and in vivo. Recently, the possible role of OCLs as immunosuppressive cells in the MM BM microenvironment has been underlined. OCLs protect MM cells against T cell-mediated cytotoxicity through the expression of several molecules including programmed death-ligand (PD-L) 1, galectin (Gal) 9, CD200, and indoleamine-2,3-dioxygenase (IDO). Among the molecules that could be involved in the link between immune-microenvironment and osteoclastogenesis the role of CD38 has been hypothesized. CD38 is a well-known adhesion molecule and an ectoenzyme highly expressed by MM cells. Moreover, CD38 is expressed by OCLs and at the surface level on OCL precursors. Targeting CD38 with monoclonal antibodies showed inhibition of both osteoclastogenesis and OCL-mediated suppression of T cell function. This review elucidates this evidence indicating that osteoclastogenesis affect MM immune-microenvironment being a potential target to improve anti-MM immunity and to ameliorate bone disease.

Cellular transcriptional response to zirconia-based implant materials

OBJECTIVE

To adequately address clinically important issues such as osseointegration and soft tissue integration, we screened for the direct biological cell response by culturing human osteoblasts and gingival fibroblasts on novel zirconia-based dental implant biomaterials and subjecting them to transcriptional analysis.

METHODS

Biomaterials used for osteoblasts involved micro-roughened surfaces made of a new type of ceria-stabilized zirconia composite with two different topographies, zirconium dioxide, and yttria-stabilized zirconia (control). For fibroblasts smooth ceria- and yttria-stabilized zirconia surface were used. The expression of 90 issue-relevant genes was determined on mRNA transcription level by real-time PCR Array technology after growth periods of 1 and 7 days.

RESULTS

Generally, modulation of gene transcription exhibited a dual dependence, first by time and second by the biomaterial, whereas biomaterial-triggered changes were predominantly caused by the biomaterials' chemistry rather than surface topography. Per se, modulated genes assigned to regenerative tissue processes such as fracture healing and wound healing and in detail included colony stimulating factors (CSF2 and CSF3), growth factors, which regulate bone matrix properties (e.g. BMP3 and TGFB1), osteogenic BMPs (BMP2/4/6/7) and transcription factors (RUNX2 and SP7), matrix collagens and osteocalcin, laminins as well as integrin ß1 and MMP-2.

SIGNIFICANCE

With respect to the biomaterials under study, the screening showed that a new zirconia-based composite stabilized with ceria may be promising to provide clinically desired periodontal tissue integration. Moreover, by detecting biomarkers modulated in a time- and/or biomaterial-dependent manner, we identified candidate genes for the targeted analysis of cell-implant bioresponse during biomaterial research and development.

Osteoblasts secrete Cxcl9 to regulate angiogenesis in bone

Communication between osteoblasts and endothelial cells (ECs) is essential for bone turnover, but the molecular mechanisms of such communication are not well defined. Here we identify Cxcl9 as an angiostatic factor secreted by osteoblasts in the bone marrow microenvironment. We show that Cxcl9 produced by osteoblasts interacts with vascular endothelial growth factor and prevents its binding to ECs and osteoblasts, thus abrogating angiogenesis and osteogenesis both in mouse bone and in vitro. The mechanistic target of rapamycin complex 1 activates Cxcl9 expression by transcriptional upregulation of STAT1 and increases binding of STAT1 to the Cxcl9 promoter in osteoblasts. These findings reveal the essential role of osteoblast-produced Cxcl9 in angiogenesis and osteogenesis in bone, and Cxcl9 can be targeted to elevate bone angiogenesis and prevent bone loss-related diseases.

Repercussions of NSAIDS drugs on bone tissue: the osteoblast

Non-steroidal anti-inflammatory drugs (NSAIDs) can act by modulating the behavior of osteoblasts, including their proliferation, differentiation, adhesion, and migration, but not all NSAIDs have these effects. Our objective was to update the information on this issue in a review of the literature in order to offer guidance on the prescription of the appropriate NSAID(s) to patients requiring bone tissue repair. To review current knowledge of this issue by searching for all relevant publications since 2001 in the MEDLINE, EMBASE and Cochrane Library databases, we used the following descriptors: bone tissue, osteoblast, NSAIDs, Anti-inflammatory drugs. Published studies show that most NSAIDs have an adverse effect on osteoblast growth by cell cycle arrest and apoptosis induction. The effect on differentiation varies according to the drug, dose, and treatment time. Osteoblast adhesion is increased and migration decreased by some NSAIDs, such as indomethacin and diclofenac. The antigenic profile or phagocytic function can also be modulated by NSAIDs. In general, NSAIDs have an adverse effect on bone tissue and given the routine administration of NSAIDs to individuals requiring bone repair, in which the osteoblast has an essential role, this effect on bone should be borne in mind.

Therapeutic doses of nonsteroidal anti-inflammatory drugs inhibit osteosarcoma MG-63 osteoblast-like cells maturation, viability, and biomineralization potential

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used to reduce pain and inflammation. However, their effect on bone metabolisms is not well known, and results in the literature are contradictory. The present study focusses on the effect of dexketoprofen, ketorolac, metamizole, and acetylsalicylic acid, at therapeutic doses, on different biochemical and phenotypic pathways in human osteoblast-like cells. Osteoblasts (MG-63 cell line) were incubated in culture medium with 1-10 μM of dexketoprofen, ketorolac, metamizole, and acetylsalicylic acid. Flow cytometry was used to study antigenic profile and phagocytic activity. The osteoblastic differentiation was evaluated by mineralization and synthesis of collagen fibers by microscopy and alkaline phosphatase activity (ALP) by spectrophotometric assay. Short-term treatment with therapeutic doses of NSAIDs modulated differentiation, antigenic profile, and phagocyte activity of osteoblast-like cells. The treatment reduced ALP synthesis and matrix mineralization. However, nonsignificant differences were observed on collagen syntheses after treatments. The percentage of CD54 expression was increased with all treatments. CD80, CD86, and HLA-DR showed a decreased expression, which depended on NSAID and the dose applied. The treatments also decreased phagocyte activity in this cellular population. The results of this paper provide evidences that NSAIDs inhibit the osteoblast differentiation process thus reducing their ability to produce new bone mineralized extracellular matrix.

Induction of mast-cell accumulation by promutoxin, an Arg-49 phospholipase A2

Local inflammation is a prominent characteristic of snakebite wound, and snake-venom phospholipase A2s (PLA2s) are some of the main component that contribute to accumulation of inflammatory cells. However, the action of an R49 PLA2s, promutoxin from Protobothrops mucrosquamatus venom, on mast-cell accumulation has not been previously examined. Using a mouse peritoneal model, we found that promutoxin can induce approximately-6-fold increase in mast-cell accumulation, and the response lasts at least for 16 h. The promutoxin-induced mast cell accumulation was inhibited by cyproheptadine, terfenadine, and Ginkgolide B, indicating that histamine and platelet-activating factor (PAF) is likely to contribute to the mast-cells accumulation. Preinjection of antibodies against adhesion molecules ICAM-1, CD18, CD11a, and L-selectin showed that ICAM-1, and CD18, CD11a are key adhesion molecules of promutoxin-induced mast-cell accumulation. In conclusion, promutoxin can induce accumulation of mast cells, which may contribute to snake-venom wound.

Changes in Cytokines of the Bone Microenvironment during Breast Cancer Metastasis

It is commonly accepted that cancer cells interact with host cells to create a microenvironment favoring malignant colonization. The complex bone microenvironment produces an ever changing array of cytokines and growth factors. In this study, we examined levels of MCP-1, IL-6, KC, MIP-2, VEGF, MIG, and eotaxin in femurs of athymic nude mice inoculated via intracardiac injection with MDA-MB-231^GFP human metastatic breast cancer cells, MDA-MB-231BRMS1^GFP, a metastasis suppressed variant, or PBS. Animals were euthanized (day 3, 11, 19, 27 after injection) to examine femoral cytokine levels at various stages of cancer cell colonization. The epiphysis contained significantly more cytokines than the diaphysis except for MIG which was similar throughout the bone. Variation among femurs was evident within all groups. By day 27, MCP-1, MIG, VEGF and eotaxin levels were significantly greater in femurs of cancer cell-inoculated mice. These pro-osteoclastic and angiogenic cytokines may manipulate the bone microenvironment to enhance cancer cell colonization.

Effect of platelet-rich plasma on growth and antigenic profile of human osteoblasts and its clinical impact

PURPOSE

In recent years, there has been widespread clinical use of platelet-rich plasma (PRP) to facilitate the regeneration of different tissues. However, few data are available on the effect of PRP on parameters other than cell growth. The aim of the present study was to evaluate the effect of PRP on the cell cycle, antigenic profile, and proliferation of primary cultured human osteoblasts.

MATERIALS AND METHODS

The cells in the present study were derived from human bone sections obtained from healthy volunteers during third molar surgery. PRP was prepared from human venous blood and used to culture the cell line obtained from the same patient. Flow cytometry was used to study the cell cycle, antigenic profile, and proliferation.

RESULTS

The treatment of osteoblasts with PRP modified the expression of CD54, CD80, CD86, and HLA-DR antigens. PRP treatment increased cell proliferation in the short term, but the cell proliferation capacity diminished in the long term, perhaps owing to cell exhaustion. No change in the cell cycle profile was observed in the PRP-cultured cells.

CONCLUSIONS

These results suggest that PRP treatment accelerates bone neoformation with no cell cycle changes that might carry a risk of malignant transformation.

Effects of Indomethacin, Nimesulide, and Diclofenac on Human MG-63 Osteosarcoma Cell Line

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed drugs worldwide and serve as treatment of some degenerative inflammatory joint diseases. The aim of the present study was to investigate the influence of different concentrations of three NSAIDs on cell proliferation, differentiation, antigenic profile, and cell cycle in the human MG-63 osteosarcoma cell line, incubated for 24 hr. All NSAIDs had an inhibiting effect on osteoblastic proliferation. Treatments for 24 hr had small but significant effects on the antigenic profile. No treatment altered osteocalcin synthesis. Indomethacin and nimesulide treatments arrested the cell cycle at G0/G1. These results suggest that indomethacin, nimesulide, and diclofenac appear to have no effects on osteocalcin synthesis and a slight effect on the antigenic profile. They may delay bone regeneration due to their inhibiting effect on osteoblast growth. Therefore, these drugs should only be used in situations that do not require rapid bone healing.

CXCL8 and CCL5 expression in synovial fluid and blood serum in patients with osteoarthritis of the knee

Chemokines proved able to induce release of enzymes relevant in cartilage damage. The present study addressed the levels of CXCL8 and CCL5 and the potential role of these chemokines in predicting the morphological changes in the course of osteoarthritis (OA). Synovial fluid (SF) and blood serum were obtained from 20 patients undergoing knee replacement surgery because of OA. For comparison, samples were also obtained from another 20 patients during diagnostic or therapeutic arthroscopy performed because of knee injury. The samples were analyzed for CXCL8 and CCL5 using enzyme-linked immunosorbent assay. SF from the group with OA showed significantly (p = 0.024) increased levels of CXCL8 when compared with the group after knee injury. We have not demonstrated any significant correlation between chemokine expression and clinical or radiological signs of OA. Mediators of inflammation are the potential predicting factors of OA, however, with respect to examined chemokines development of a diagnostic test can be limited by the low serum concentration and lack of correlation with clinical and radiological signs of the disease.

Induction of inflammatory cell accumulation by TM-N49 and promutoxin, two novel phospholipase A(2)

Local inflammation is a prominent characteristic of snakebite wound. Snake venom phospholipase A(2)s (PLA(2)s) are one of the main components which contribute to accumulation of inflammatory cells. We have isolated TM-N49 and promutoxin from Protobothrops mucrosquamatus venom and investigated their ability in induction of cell accumulation by using an in vivo mouse model. The results showed that both TM-N49 and promutoxin are potent stimuli for induction of neutrophil, lymphocyte, macrophage and eosinophil accumulation in the mouse peritoneum. The TM-N49- and promutoxin-induced inflammatory cell accumulation was inhibited by pretreatment of animals with cyproheptadine, terfenadine and Ginkgolide B, indicating that histamine and PAF is likely to contribute to the cells accumulation. Pre-injection of antibodies against adhesion molecules ICAM-1, CD18, CD11a and L-selectin showed that ICAM-1 is a key adhesion molecule of TM-N49- and promutoxin-induced lymphocyte, macrophage and eosinophil accumulation; CD18 and CD11a plays an important role in the migration of neutrophils, eosinophils and macrophages; and L-selectin is involved in the neutrophil and eosinophil accumulation. In conclusion, induction of inflammatory cell accumulation by TM-N49 and promutoxin confirms that group II PLA(2)s is pivotal stimulus for cell infiltration, through which they participate in the formation of snakebite inflammation.

Chitosan monomer accelerates alkaline phosphatase activity on human osteoblastic cells under hypofunctional conditions

Chitosan is a natural polyaminosaccharide that is extensively applied as an antitumor and antirheumatic drug. However, there are few reports about its effects on hypofunctional osteoblasts in vitro. We investigated the biological characteristics of a human osteoblastic cell line (NOS-1 cells) that was cultured with a chitosan monomer-containing medium under simulated microgravity conditions. After 7 days of cell incubation under the conventional conditions, the flasks were transferred to a microgravity simulator for 3 days. In the 0.005% chitosan monomer supplemented group, the marker enzyme of biological mineralization, the alkaline phosphatase (ALP) activity, was significantly higher compared with the control group (p<0.05). A cDNA microarray was performed to investigate the effects on the mRNA level by chitosan monomer, and the fluorescent signal was analyzed. The interferon gamma (IFN-gamma) receptor gene was detected with a signal ration of 2.2. The slight increase of IFN-gamma receptor expression was confirmed after 3 days of incubation according to RT-PCR analysis. Western blot analysis also showed the increased expression of IFN-gamma receptor. These results suggest that a supra-low concentration of chitosan monomer may increase the ALP activity of osteoblastic cells through the IFN-gamma receptor at the early phase of cell culture and recover the activity for biological mineralization under the hypofunctional condition.

Expression of elevated levels of pro-inflammatory cytokines in SARS-CoV-infected ACE2+ cells in SARS patients: relation to the acute lung injury and pathogenesis of SARS

The authors have previously shown that acute lung injury (ALI) produces a wide spectrum of pathological processes in patients who die of severe acute respiratory syndrome (SARS) and that the SARS coronavirus (SARS‐CoV) nucleoprotein is detectable in the lungs, and other organs and tissues, in these patients. In the present study, immunohistochemistry (IHC) and in situ hybridization (ISH) assays were used to analyse the expression of angiotensin‐converting enzyme 2 (ACE2), SARS‐CoV spike (S) protein, and some pro‐inflammatory cytokines (PICs) including MCP‐1, TGF‐β1, TNF‐α, IL‐1β, and IL‐6 in autopsy tissues from four patients who died of SARS. SARS‐CoV S protein and its RNA were only detected in ACE2⁺ cells in the lungs and other organs, indicating that ACE2‐expressing cells are the primary targets for SARS‐CoV infection in vivo in humans. High levels of PICs were expressed in the SARS‐CoV‐infected ACE2⁺ cells, but not in the uninfected cells. These results suggest that cells infected by SARS‐CoV produce elevated levels of PICs which may cause immuno‐mediated damage to the lungs and other organs, resulting in ALI and, subsequently, multi‐organ dysfunction. Therefore application of PIC antagonists may reduce the severity and mortality of SARS. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Involvement of ICAM-1 in bone metabolism: a potential target in the treatment of bone diseases?

Bone diseases such as osteoporosis, osteoarthritis and rheumatoid arthritis (RA) affect a great proportion of individuals, with debilitating consequences in terms of pain and progressive limitation of function. Existing treatment of these pathologies has been unable to alter the natural evolution of the disease and, as such, a clearer understanding of the pathophysiology is necessary in order to generate new treatment alternatives. One therapeutic strategy could involve the targeting of intercellular adhesion molecule-1 (ICAM-1; CD54). In bone, ICAM-1 is expressed at the surface of osteoblasts (Obs) and its counter-receptor, leukocyte function-associated antigen-1 (LFA-1; CD11a), at the surface of osteoclast (Oc) precursors. ICAM-1 blockade between the Ob and the pre-Oc results in an inhibition of Oc recruitment and a modulation of inflammation, which could potentially help in controlling disease activity in bone pathologies. So far, clinical studies on ICAM-1 blockade in bone diseases have been limited to RA. A better understanding of the implication of this adhesion molecule in Ob/Oc interactions and inflammatory mediation in the bone pathological state, however, is needed. As new discoveries on the role of this adhesion molecule are being reported, ICAM-1 could become a potential target for other bone diseases as well.

Immunocompetent properties of human osteoblasts: interactions with T lymphocytes

We sought to determine whether osteoblasts (OBs) can serve as accessory cells (ACs) for T-cell activation and whether T cells directly activate OB production of IL-6, using primary human OBs (NHOst), the transformed fetal osteoblast line hFOB1.19, and an osteosarcoma line SaOS-2. Robust, bidirectional activating interactions were shown using each of these three human ostoblast lines.

INTRODUCTION

Osteoblasts (OBs) could come into contact with lymphocytes during inflammatory joint destruction and fracture repair.

MATERIALS AND METHODS

We used several in vitro assays to assess the ability of T cells and OBs to interact in the generation of immune and inflammatory responses.

RESULTS

By flow cytometry, three OB cell lines all were found to express ligands for T-cell co-stimulation. The integrin ligand CD54/ICAM-1 was constitutively expressed by hFOB1.19 and NHOst and was upregulated on SaOS-2 by IFN-gamma. MHC Class II was upregulated on all three lines by IFN-gamma. CD166/ALCAM, a ligand of the T-cell molecule CD6, was constitutively expressed on all three lines. A second putative CD6 ligand designated 3A11 was expressed on hFOB1.19 and NHOst, but not consistently on SaOS-2. The ectoenzyme CD26 (dipeptidyl peptidase IV) was expressed on hFOB1.19 and NHOst, but not on SaOS-2. All three cell lines presented superantigen to T cells, especially after treatment with IFN-gamma. Superantigen presentation was inhibited by antibodies to the leukocyte integrin CD11a/CD18 (LFA-1), MHC Class II, and CD54/ICAM-1. T cells, particularly when cytokine activated for 7 days before co-culture, stimulated all three osteoblast lines to produce interleukin (IL)-6, and this effect was boosted when IL-17 was added to the co-cultures with either resting T cells or cytokine-activated T cells.

CONCLUSIONS

Bidirectional activating interactions are readily shown between human T cells and several types of human OBs. The expression by OBs of ligands for the T cell-specific molecule CD6, as well as other molecules involved in immune interactions, strongly suggests that such in vitro interactions are representative of physiologic or pathologic events that occur in vivo.

Donor CD4+CD25+ T cells promote engraftment and tolerance following MHC-mismatched hematopoietic cell transplantation

Allogeneic bone marrow transplantation (BMT) is a potentially curative treatment for both inherited and acquired diseases of the hematopoietic compartment; however, its wider use is limited by the frequent and severe outcome of graft-versus-host disease (GVHD). Unfortunately, efforts to reduce GVHD by removing donor T cells have resulted in poor engraftment and elevated disease recurrence. Alternative cell populations capable of supporting allogeneic hematopoietic stem/progenitor cell engraftment without inducing GVHD could increase numbers of potential recipients while broadening the pool of acceptable donors. Although unfractionated CD4(+) T cells have not been shown to be an efficient facilitating population, CD4(+)CD25(+) regulatory cells (T-reg's) were examined for their capacity to support allogeneic hematopoietic engraftment. In a murine fully major histocompatibility complex (MHC)-mismatched BMT model, cotransplantation of donor B6 T-reg's into sublethally conditioned BALB/c recipients supported significantly greater lineage-committed and multipotential donor progenitors in recipient spleens 1 week after transplantation and significantly increased long-term multilineage donor chimerism. Donor engraftment occurred without GVHD-related weight loss or lethality and was associated with tolerance to donor and host antigens by in vitro and in vivo analyses. Donor CD4(+)CD25(+) T cells may therefore represent a potential alternative to unfractionated T cells for promotion of allogeneic engraftment in clinical hematopoietic cell transplantation.

Chemokines in cartilage degradation

Besides the well-known activities of the prototypical inflammatory cytokines (IL-1beta, TNFalpha), a role for chemokines and their receptors in cartilage degradation in osteoarthritis has recently been reported. Human chondrocytes can produce CC and CXC chemokines and express chemokine receptors for both chemokine subfamilies. Engagement of these receptors can induce the release of matrix degrading enzymes such as matrix metalloproteinases 1, 3, and 13, and N-acetyl-beta-D-glucosaminidase. Furthermore GROalpha, a CXC chemokine acting on CXCR2, can activate an apoptotic pathway in chondrocytes that leads to chondrocyte cell death. These findings suggest that chemokines can act as an autocrine or paracrine loop on chondrocytes and can contribute to many pathophysiological patterns present in osteoarthritis. Chemokines and their downstream signaling pathways can be considered novel therapeutic targets in osteoarthritis.

Human osteoclasts express different CXC chemokines depending on cell culture substrate: molecular and immunocytochemical evidence of high levels of CXCL10 and CXCL12

Chemokines are important mediators of chemotaxis, cell adherence, and proliferation and exert specific functions in bone remodeling. Despite the potential intriguing role of chemokines in the regulation of osteoclast (OC) functions, little is known about the expression of chemokines and their receptors in human OCs at different stages of differentiation. Therefore, we analyzed the expression of CXC chemokine receptors (CXCR1, CXCR2, CXCR3, CXCR4 and CXCR5) and ligands (CXCL8, CXCL10, CXCL12 and CXCL13) both at molecular and protein levels, in human OCs grown on plastic or calcium phosphate-coated slides at different stages of differentiation. Real-time PCR showed that CXCR1, CXCR2, CXCR3, CXCR4, CXCR5 and CXCL8 were expressed in undifferentiated cells and significantly decreased during OC differentiation. By contrast, CXCL10 and CXCL12 were strongly upregulated from day 0 to day 8 in cells grown on calcium phosphate-coated slides. Immunocytochemistry showed that OCs grown on plastic expressed CXCR3, CXCR4, CXCR5, CXCL8 and CXCL12, while they were negative for CXCR1, CXCR2 and CXCL10. Interestingly, both at molecular and protein levels CXCL10 and CXCL12 significantly increased only when cells were differentiated on calcium phosphate-coated slides. These data suggest that the selection of a substrate that better mimics the tridimensional structure of bone tissue, thus favoring OC maturation and differentiation, may be necessary when studying osteoclastogenesis in vitro.