Alveolar macrophage deficiency in osteopetrotic mice deficient in macrophage colony-stimulating factor is spontaneously corrected with age and associated with matrix metalloproteinase expression and emphysema

Macrophage colony-stimulating factor (M-CSF) is one of several hematologic growth factors capable of regulating the survival, proliferation, and differentiation of macrophages, but its role in modulation of the accumulation and function of alveolar macrophages (AMs) in vivo is not well defined. Osteopetrotic (Op/Op) mice have no detectable M-CSF and show variable tissue-specific reductions in macrophage numbers. It was hypothesized that AMs would be decreased in number and have altered function in Op/Op mice because of the absence of M-CSF. Lung macrophages identified by Mac-3 staining in lung sections were decreased in number in 20-day-old Op/Op mice (P <.001) but not Op/Op mice older than 4 months (P =.68) compared with findings in age-matched littermate controls. The numbers of AMs recovered by bronchoalveolar lavage (BAL) were also reduced in young but not adult Op/Op mice compared with controls. Expression of interleukin-3 (IL-3) was increased in the lungs of Op/Op mice compared with controls as determined by quantification of IL-3 cytokine levels (P =.04), bioactivity (P =.02), and messenger RNA transcript levels. AMs of Op/Op mice spontaneously released higher levels of matrix metalloproteinases (MMPs) than AMs of controls as determined by immunohistochemical staining of AMs and zymographic assessment of BAL fluid and AM lysates. Consistent with an increased release of MMP, Op/Op mice had abnormal elastin deposition and spontaneously developed emphysema in the absence of molecular or cellular evidence of lung inflammation. These data show that the AM deficiency observed in young Op/Op mice is spontaneously corrected with age and is associated with increased lung levels of IL-3, spontaneous MMP expression by AMs, and destruction of lung tissue.

Toll-like receptor 2 and 4 surface expressions on human monocytes are modulated by interferon-gamma and macrophage colony-stimulating factor

Human Toll-like receptor 2 (TLR2) and TLR4 are recently identified receptors. TLR4 was shown to be the main protein involved in recognizing Gram-negative bacteria, whereas TLR2 is apparently the key factor in responses to other types of microbial pathogens. We examined regulations of TLR2 and TLR4 surface expressions in human peripheral blood monocytes by interferon-gamma (IFN-gamma) and macrophage colony-stimulating factor (M-CSF). IFN-gamma up-regulated both TLR2 and TLR4, but enhanced the surface expression, on human peripheral blood monocytes of TLR4 more than that of TLR2. On the other hand, M-CSF up-regulated both TLR2 and TLR4 surface expression on human peripheral blood monocytes, with no change in the ratio of TLR2/TLR4 surface expression. These results indicate that IFN-gamma enhances receptors involved in the response to Gram-negative bacteria more than those involved in responses to other types of microbial pathogens, whereas M-CSF enhances the receptor response to Gram-negative bacteria in the same manner as to other types of microbial pathogens.

Astrocyte-released cytokines induce ramification and outward K+ channel expression in microglia via distinct signalling pathways

Differentiation of microglial cells is characterized by transformation from ameboid into ramified cell shape and up-regulation of K+ channels. The processes of microglial differentiation are controlled by astrocytic factors. The mechanisms by which astrocytes cause developmental changes in morphological and electrophysiological properties of microglia have remained unclear. We show here that the cytokines transforming growth factor-beta (TGF-beta), macrophage colony-stimulating factor (M-CSF) and granulocyte/macrophage colony-stimulating factor (GM-CSF) are released by astrocytes at concentrations sufficient to induce ramification and up-regulation of delayed rectifier (DR) K+ channels in microglia. Transformation from ameboid into ramified morphology induced in microglia by exposure to astrocyte-conditioned medium (ACM) was inhibited by neutralizing antibodies against TGF-beta, M-CSF or GM-CSF, whilst ACM-induced DR channel expression was exclusively inhibited by antibodies against TGF-beta. Although both ramification and DR channel up-regulation occurred simultaneously, DR channel blockade by charybdotoxin failed to inhibit microglial ramification. The ACM-induced ramification of microglia was inhibited by the tyrosine kinase inhibitor genistein, whereas DR channel up-regulation did not occur in the presence of the serine/threonine kinase inhibitor H7. Our data suggest that astrocytes modulate processes of microglial differentiation in parallel but via distinct signalling pathways.

The molecular basis of osteoclast differentiation and activation

Osteoclasts develop from haemopoietic cells of the monocyte-macrophage lineage. Osteoblasts or stromal cells are essentially involved in osteoclastogenesis through cell-cell interaction with osteoclast progenitor cells. Recent findings indicate that osteoblasts/stromal cells express osteoclast differentiation factor (ODF, also called RANKL, TRANCE and OPGL) as a membrane-associated factor in response to several osteotropic factors to support osteoclast differentiation. ODF is a new member of the tumour necrosis factor (TNF) ligand family. Osteoclast precursors, which express RANK, a TNF receptor family member, recognize ODF through cell-cell interactions with osteoblasts/stromal cells, and differentiate into osteoclasts in the presence of macrophage colony-stimulating factor (M-CSF). Osteoclastogenesis inhibitory factor (OCIF, also called OPG), is a secreted TNF receptor, which acts as a decoy receptor for ODF. ODF is responsible for inducing not only differentiation, but also activation of osteoclasts. Interleukin 1 alpha (IL-1 alpha) can be substituted for ODF in inducing the activation of osteoclasts. Recently, it was shown that mouse TNF alpha stimulated the differentiation of M-CSF-dependent mouse bone marrow macrophages into osteoclasts in the presence of M-CSF without any help of osteoblasts/stromal cells. Osteoclast formation induced by TNF alpha was inhibited by antibodies against TNF type 1 receptor (TNFR1) or TNFR2, but not by OCIF. Osteoclasts induced by TNF alpha formed resorption pits on dentine slices only in the presence of IL-1 alpha. These results demonstrate that TNF alpha stimulates osteoclast differentiation through a mechanism independent of the ODF-RANK interaction. TNF alpha and IL-1 alpha may play an important role in pathological bone resorption due to inflammation.

Regulation of human endometrial stromal decidualization by macrophage colony-stimulating factor

Decidualized human endometrial stromal cells and human decidual CD56+ cells are reported to produce macrophage colony-stimulating factor (M-CSF), although its physiological roles remain unclear. In this study, the effects of M-CSF on cell viability and 8-Br-cAMP-stimulated decidualization of normal human endometrial stromal cells are examined by using an in vitro decidualization activity assay system. M-CSF alone affected neither the viable cell numbers nor PRL release of nonstimulated stromal cells, while high concentrations of M-CSF strongly suppressed the viable cell numbers and PRL secretion of stromal cells costimulated with 8-Br-cAMP and M-CSF. However, M-CSF did not suppress the viable cell numbers and PRL secretion of 8-Br-cAMP-induced decidualized cells. These results indicate that high concentrations of M-CSF can suppress the cell viability of stromal cells in the decidualization process, and inhibit decidualization of endometrial stromal cells. Thus, nonpregnant decidual M-CSF may autoregulate decidualization and the viable cell numbers of endometrial stromal cells in a paracrine manner.

Generation of macrophages from early T progenitors in vitro

Early T progenitors in the thymus have been reported to have the capacity to develop into B cells, thymic dendritic cells, and NK cells. Here we describe conditions that induce early T progenitors to develop into macrophages. Initially, we observed that early T progenitors could be induced to develop into macrophages by cytokines produced from a thymic stromal cell line, TFGD, and later we found that the cytokine mixture of M-CSF plus IL-6 plus IL-7 also induced macrophage differentiation from pro-T cells. M-CSF by itself was unable to induce macrophage differentiation from early T progenitors. To correlate this observation with the developmental potential of early T progenitors, mouse embryonic thymocytes were sorted into four populations, pro-T1 to pro-T4, based on the expression of CD44 and CD25, and then cultured with TFGD culture supernatant. We found that pro-T1 and pro-T2 cells, but not pro-T3 and pro-T4 cells, generate macrophages. Limiting dilution analysis of the differentiation capability of sorted pro-T2 cells also confirmed that pro-T2 cells could generate macrophages. These results suggest that T cells and thymic macrophages could originate from a common intrathymic precursor.

Antitumor immunity induced by irradiated tumor cells producing macrophage colony-stimulating factor

We previously reported that administration into mice of mouse lymphoid leukemia L1210 cells engineered to secrete macrophage colony-stimulating factor (M-CSF) could lead to tumor rejection. Here, we demonstrate that inoculation with irradiated M-CSF-producing cells protects mice against a subsequent challenge with unmodified parental tumor cells. We used 2 experimental protocols: the inoculation with irradiated M-CSF-producing L1210 cells (EM5) before the challenge with parental cells and after the challenge with parental cells. Both protocols effectively improved the survival rate of mice compared with protocols in which irradiated non-M-CSF-producing L1210 cells (EM-mock) were inoculated. Inoculation with 1 x 10(2) irradiated EM5 cells was sufficient to prolong the survival time of mice subsequently challenged with 1 x 10(4) parental cells. In vivo depletion experiments with administration of antibodies suggested the involvement of CD4+ T cells, CD8+ T cells, and natural killer (NK) cells in the antitumor effect. Consistent with these findings, the cytotoxic T lymphocyte activity of splenocytes from EM5-inoculated mice was higher than that from EM-mock-inoculated mice, and L1210 tumors were heavily infiltrated by CD4+ T cells and NK cells as well as macrophages in EM5-inoculated mice.

Colony-stimulating factor 1 promotes progression of mammary tumors to malignancy

In human breast carcinomas, overexpression of the macrophage colony-stimulating factor (CSF-1) and its receptor (CSF-1R) correlates with poor prognosis. To establish if there is a causal relationship between CSF-1 and breast cancer progression, we crossed a transgenic mouse susceptible to mammary cancer with mice containing a recessive null mutation in the CSF-1 gene (Csf1(op)) and followed tumor progression in wild-type and null mutant mice. The absence of CSF-1 affects neither the incidence nor the growth of the primary tumors but delayed their development to invasive, metastatic carcinomas. Transgenic expression of CSF-1 in the mammary epithelium of both Csf1(op)/Csf1(op) and wild-type tumor-prone mice led to an acceleration to the late stages of carcinoma and to a significant increase in pulmonary metastasis. This was associated with an enhanced infiltration of macrophages into the primary tumor. These studies demonstrate that the growth of mammary tumors and the development to malignancy are separate processes and that CSF-1 selectively promotes the latter process. CSF-1 may promote metastatic potential by regulating the infiltration and function of tumor-associated macrophages as, at the tumor site, CSF-1R expression was restricted to macrophages. Our data suggest that agents directed at CSF-1/CSF-1R activity could have important therapeutic effects.

Immunomodulatory approaches to augment phagocyte-mediated host defense for treatment of infectious diseases

Neutrophils, monocytes, and tissue-based macrophages are major cellular components of the innate immune system, which represents the initial line of host defense against invading pathogens. Four cytokines-granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), and interferon-gamma (IFN-gamma)--have received increasing attention as potential adjunctive immunomodulatory agents for treatment of infectious diseases. Studies conducted in vitro and in vivo have shown that G-CSF, GM-CSF, and IFN-gamma can augment the functional antimicrobial activities of neutrophils. Similarly, GM-CSF, M-CSF, and IFN-gamma up-regulate multiple antimicrobial mechanisms in monocytes and macrophages. Studies conducted in animal models have shown the potential use of each of these cytokines for the treatment of infections caused by a variety of bacterial, fungal, and parasitic diseases. Because clinical experience with these immunomodulatory cytokines is relatively limited and currently investigational, controlled clinical trials will be necessary to define specific indications for the administration of these cytokines in therapeutic regimens.

Comparison of macrophage responses to oxidized low-density lipoprotein and macrophage colony-stimulating factor (M-CSF or CSF-1)

Modification of low-density lipoprotein (LDL), for example by oxidation, could be involved in foam cell formation and proliferation observed in atherosclerotic lesions. Macrophage colony-stimulating factor (CSF-1 or M-CSF) has been implicated in foam cell development. It has been reported previously that oxidized LDL (ox.LDL) and CSF-1 synergistically stimulate DNA synthesis in murine bone-marrow-derived macrophages (BMM). The critical signal-transduction cascades responsible for the proliferative response to ox.LDL, as well as their relationship to those mediating CSF-1 action, are unknown. We report here that ox.LDL stimulated extracellular signal-regulated protein kinase (ERK)-1, ERK-2 and phosphoinositide 3-kinase activities in BMM but to a weaker extent than optimal CSF-1 concentrations at the time points examined. Inhibitor studies suggested at least a partial role for these kinases, as well as p70 S6-kinase, in ox.LDL-induced macrophage survival and DNA synthesis. For the DNA synthesis response to CSF-1, the degree of inhibition by PD98059, wortmannin and rapamycin was significant at low CSF-1 concentrations but was reduced as the CSF-1 dose increased. Using BMM from CSF-1-deficient mice (op/op) and a neutralizing antibody approach, we found no evidence for an essential role for endogenous CSF-1 in ox.LDL-mediated survival or DNA synthesis; likewise, with the same approaches, no evidence was obtained for an essential role for endogenous granulocyte/macrophage-CSF in ox.LDL-mediated macrophage survival and, in contrast with the literature, ox.LDL-induced macrophage DNA synthesis.

Convergence of alpha(v)beta(3) integrin- and macrophage colony stimulating factor-mediated signals on phospholipase Cgamma in prefusion osteoclasts

The macrophage colony stimulating factor (M-CSF) and alpha(v)beta(3) integrins play critical roles in osteoclast function. This study examines M-CSF- and adhesion-induced signaling in prefusion osteoclasts (pOCs) derived from Src-deficient and wild-type mice. Src-deficient cells attach to but do not spread on vitronectin (Vn)-coated surfaces and, contrary to wild-type cells, their adhesion does not lead to tyrosine phosphorylation of molecules activated by adhesion, including PYK2, p130(Cas), paxillin, and PLC-gamma. However, in response to M-CSF, Src(-/-) pOCs spread and migrate on Vn in an alpha(v)beta(3)-dependent manner. Involvement of PLC-gamma activation is suggested by using a PLC inhibitor, U73122, which blocks both adhesion- and M-CSF-mediated cell spreading. Furthermore, in Src(-/-) pOCs M-CSF, together with filamentous actin, causes recruitment of beta(3) integrin and PLC-gamma to adhesion contacts and induces stable association of beta(3) integrin with PLC-gamma, phosphatidylinositol 3-kinase, and PYK2. Moreover, direct interaction of PYK2 and PLC-gamma can be induced by either adhesion or M-CSF, suggesting that this interaction may enable the formation of integrin-associated complexes. Furthermore, this study suggests that in pOCs PLC-gamma is a common downstream mediator for adhesion and growth factor signals. M-CSF-initiated signaling modulates the alpha(v)beta(3) integrin-mediated cytoskeletal reorganization in prefusion osteoclasts in the absence of c-Src, possibly via PLC-gamma.

Dependence of interleukin-1-induced arthritis on granulocyte-macrophage colony-stimulating factor

OBJECTIVE

To determine whether granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage CSF (M-CSF or CSF-1) are involved in the methylated bovine serum albumin/interleukin-1 (mBSA/IL-1)-induced arthritis model.

METHODS

Following systemic injection, IL-1 has been shown to augment a weak inflammatory response to mBSA in murine joints and to induce an acute erosive arthritis. GM-CSF and M-CSF have been implicated in inflammatory reactions, including those in joints, and have recently been shown to exacerbate murine arthritis. Since in vitro studies have found that IL-1 can enhance GM-CSF and M-CSF production, we reasoned that they might be playing a part in IL-1-mediated arthritis. GM-CSF-deficient (GM-CSF-/-) and M-CSF-deficient (op/op) mice were injected intraarticularly with mBSA and subcutaneously with IL-1. Arthritis was monitored histologically on day 7. Normal mice were also treated intraperitoneally with blocking monoclonal antibodies to GM-CSF and M-CSF, and to the M-CSF receptor. Numbers of macrophages (Mac-2 and F4/80 staining) were monitored, as was the number of cycling (bromodeoxyuridine-positive) cells.

RESULTS

GM-CSF-/- mice and normal mice treated with anti-GM-CSF antibody did not show IL-1-induced arthritis progression. There was a dramatic reduction in synovial cellularity, including reduced numbers of macrophages and cycling cells. The op/op mice did not develop mBSA/IL-1-induced disease, but blocking antibody to M-CSF or to the M-CSF receptor failed to diminish disease in normal mice.

CONCLUSION

GM-CSF is involved in the IL-1-induced arthritis that follows mBSA injection; M-CSF involvement in the model is also suggested, since op/op mice did not develop arthritis. These studies provide the first in vivo evidence for a role of GM-CSF, and possibly M-CSF, in the proinflammatory actions of IL-1.

Influence of cytokines, monoclonal antibodies and chemotherapeutic drugs on epithelial cell adhesion molecule (EpCAM) and LewisY antigen expression

MoAbs against tumour-associated antigens (TAA) may be useful for the treatment of colorectal cancer. Since an increased expression of TAA may lead to enhanced antibody-dependent cellular cytotoxicity we examined whether the cytokines IL-2, IL-4, IL-6, IL-10, IL-12, interferon-alpha (IFN-alpha), IFN-gamma, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor and tumour necrosis factor-alpha can influence EpCAM and LewisY expression on the surface of the colorectal carcinoma cell lines HT29, LoVo and SW480. We found that only IFN-alpha increased significantly whereas IL-4 decreased both EpCAM and LewisY expression. IFN-gamma significantly increased LewisY expression only. When tumour cells were treated with MoAb, the LewisY-specific MoAb BR55-2 down-regulated LewisY antigen expression, whereas MoAb 17-1A, which binds to EpCAM, up-regulated this TAA after 3 days of culture. The cytokines IFN-alpha or IFN-gamma combined with MoAb 17-1A enhanced further slightly the expression of EpCAM. In additional experiments with chemotherapeutic drugs commonly used for the treatment of colorectal cancer, we found that 5-fluorouracil, mitomycin-C and oxaliplatin up-regulated EpCAM and LewisY antigen expression. Raltitrexed enhanced LewisY and down-regulated EpCAM expression, whereas CPT-11 had no influence at all. The highest expression for EpCAM on HT29 cells was achieved by the combination of IFN-alpha, 5-fluorouracil and MoAb 17-1A. Our results may be useful for defining combinations of biological and chemotherapeutic drugs for the treatment of colorectal cancer. Further trials should evaluate to what extent these combinations enhance antibody-dependent cellular cytotoxicity.

The production and clinical evaluation of macrophage colony-stimulating factor and macrophage chemoattractant protein-1 in human follicular fluids

PROBLEM

In order to investigate the role of macrophage colony-stimulating factor (M-CSF) and macrophage chemoattractant protein-1 (MCP-1) in human ovulation, we measured the concentrations of M-CSF and MCP-1 in human follicular fluids (FFs) and correlated them with oocyte maturation.

METHOD OF STUDY

The oocytes were obtained from the FFs of 46 women undergoing in vitro fertilization and embryo transfer (IVF ET). The concentrations of M-CSF and MCP-1 in the FFs were measured by enzyme-linked immunosorbent assay. In addition, granulosa cells obtained from the FFs of IVF patients were cultured and treated with forskolin and 12-O-tetradecanoylphorbol 13-acetate (TPA) for 24 48 hr.

RESULTS

Concentrations of M-CSF and MCP-1 were significantly higher in the FFs than in the serum (P < 0.01). M-CSF concentrations tended to be higher, while MCP-1 concentrations were significantly higher in the FFs containing mature oocytes than in FFs containing immature oocytes (P < 0.05). The production of M-CSF was markedly increased over the basal level after treatment with forskolin (10 microM) for 24 (P < 0.02) and 48 hr (P < 0.01); however, the production of MCP-1 was unchanged.

CONCLUSIONS

Our data suggest that M-CSF and MCP-1 may play an important role in human preovulatory processes and that M-CSF, in particular, may be regulated by cyclic adenosine monophosphate. M-CSF and MCP-1 may also be valuable biochemical markers in the evaluation of oocyte maturation.

Lipopolysaccharide-induced cytokine and receptor expression and neutrophil infiltration in the liver of osteopetrosis (op/op) mutant mice

BACKGROUND/AIMS

Mice homozygous for the osteopetrosis (op) mutation are genetically deficient in macrophage colony-stimulating factor (M-CSF/CSF-1) and are characterized by defective differentiation and function of macrophages. The aim of this study is to assess the contribution of M-CSF to lipopolysaccharide (LPS)-induced cytokine expression and neutrophil infiltration in the liver.

METHODS

We investigated the effects of LPS administration in M-CSF-deficient op/op mutant mice. The expression of cytokines and receptors in the liver was studied by immunohistochemistry and RT-PCR. Neutrophil infiltration in the liver was also examined.

RESULTS

After LPS administration, cytokine production and expression of LPS receptors, such as CD14 and scavenger receptor class A (MSR-A), were induced at lower levels in op/op mice than those in littermate mice. Neutrophil infiltration in the liver of op/op mice did not differ significantly from that of littermate mice. Anti-IL-8 receptor homologue and anti-C5a receptor antibody reduced the number of infiltrating neutrophils.

CONCLUSIONS

These findings indicate that deficient macrophage activation following LPS injection in op/op mice is associated with decreased expression of CD14 and MSR-A in the liver. Thus, M-CSF plays a critical role in LPS-induced macrophage activation but does not exert a dominant role in neutrophil infiltration in the liver.

TGF-beta 1 and IFN-gamma direct macrophage activation by TNF-alpha to osteoclastic or cytocidal phenotype

TNF-related activation-induced cytokine (TRANCE; also called receptor activator of NF-kappaB ligand (RANKL), osteoclast differentiation factor (ODF), osteoprotegerin ligand (OPGL), and TNFSF11) induces the differentiation of progenitors of the mononuclear phagocyte lineage into osteoclasts in the presence of M-CSF. Surprisingly, in view of its potent ability to induce inflammation and activate macrophage cytocidal function, TNF-alpha has also been found to induce osteoclast-like cells in vitro under similar conditions. This raises questions concerning both the nature of osteoclasts and the mechanism of lineage choice in mononuclear phagocytes. We found that, as with TRANCE, the macrophage deactivator TGF-beta(1) strongly promoted TNF-alpha-induced osteoclast-like cell formation from immature bone marrow macrophages. This was abolished by IFN-gamma. However, TRANCE did not share the ability of TNF-alpha to activate NO production or heighten respiratory burst potential by macrophages, or induce inflammation on s.c. injection into mice. This suggests that TGF-beta(1) promotes osteoclast formation not only by inhibiting cytocidal behavior, but also by actively directing TNF-alpha activation of precursors toward osteoclasts. The osteoclast appears to be an equivalent, alternative destiny for precursors to that of cytocidal macrophage, and may represent an activated variant of scavenger macrophage.

Endogenous production of TGF-beta is essential for osteoclastogenesis induced by a combination of receptor activator of NF-kappa B ligand and macrophage-colony-stimulating factor

Differentiation of osteoclasts, the cells primarily responsible for bone resorption, is controlled by a variety of osteotropic hormones and cytokines. Of these factors, receptor activator of NF-kappaB (RANK) ligand (RANKL) has been recently cloned as an essential inducer of osteoclastogenesis in the presence of M-CSF. Here, we isolated a stroma-free population of monocyte/macrophage (M/Mphi)-like hemopoietic cells from mouse unfractionated bone cells that were capable of differentiating into mature osteoclasts by treatment with soluble RANKL (sRANKL) and M-CSF. However, the efficiency of osteoclast formation was low, suggesting the requirement for additional factors. The isolated M/Mphi-like hemopoietic cells expressed TGF-beta and type I and II receptors of TGF-beta. Therefore, we examined the effect of TGF-beta on osteoclastogenesis. TGF-beta with a combination of sRANKL and M-CSF promoted the differentiation of nearly all M/Mphi-like hemopoietic cells into cells of the osteoclast lineage. Neutralizing anti-TGF-beta Ab abrogated the osteoclast generation. These TGF-beta effects were also observed in cultures of unfractionated bone cells, and anti-TGF-beta blocked the stimulatory effect of 1, 25-dihydroxyvitamin D(3). Translocation of NF-kappaB into nuclei induced by sRANKL in TGF-beta-pretreated M/Mphi-like hemopoietic cells was greater than that in untreated cells, whereas TGF-beta did not up-regulate the expression of RANK, the receptor of RANKL. Our findings suggest that TGF-beta is an essential autocrine factor for osteoclastogenesis.

Delay of tooth eruption in null mice devoid of the type I IL-1R gene

Interleukin-one alpha (IL-1alpha) is located in the stellate reticulum and its receptor, type I IL-1R (IL-1R), is present in the adjacent dental follicle. IL-1alpha may play a role in initiating tooth eruption because of its ability to enhance the gene expression in the dental follicle of putative tooth eruption molecules colony-stimulating factor-one (CSF-1). monocyte chemotactic protein-1 (MCP-1), and nuclear factor kappa B (NFkappa-B). To directly examine the effect of IL-1alpha and IL-1R on tooth eruption, we observed the times of tooth eruption in null mice devoid of the type I IL-1R gene. The results showed that the time of eruption in the null mice was delayed by 2 d for the first mandibular molar and 1 d for incisors as compared to wild type controls. Reverse transcription-polymerase chain reaction (RT-PCR) techniques confirmed the absence of the IL-1R gene in the null mice, but the genes for CSF-1 and NFkappaB were still expressed. Thus, a molecule(s) other than IL-1alpha also may enhance the expression of CSF- and NFkappaB in the dental follicle. Because there is a slight delay of tooth eruption in IL-1R null mice, IL-1alpha may normally play a role in eruption. However, eruption eventually can occur without the signaling from IL-1alpha.

Role of the membrane form of human colony-stimulating factor-1 (CSF-1) in proliferation of multipotent hematopoietic FDCP-mix cells expressing human CSF-1 receptor

Because IL-3-dependent multipotential FDCP-Mix cells expressing human colony-stimulating factor-1 (CSF-1) receptor did not proliferate in response to soluble CSF-1, we investigated whether their proliferation would be induced in co-culture with adherent cells expressing the membrane form of CSF-1 (MemCSF-1). FDCP-Mix cells with high CSF-1R expression (NAF21 cells) were placed on stromal MS-5 cells or STO fibroblasts expressing MemCSF-1 (2M-1 cells and STO-M2 cells, respectively), in absence of IL-3. NAF21 cells bound significantly to 2M-1 cells as compared to control FDCP-Mix cells. Adhesion of NAF21 cells was inhibited by anti-huCSF-1 antibodies, as well as anti-huCSF-1R antibodies. Interestingly, NAF21 cells proliferated on both 2M-1 and STO-M2 cells but with very different kinetics. Moreover, NAF21 cell proliferation was also supported by glutaraldehyde-fixed 2M-1 cells or highly concentrated MS-5 cell culture supernatant, but not by CSF-1 coated on culture dishes. These results strongly suggest that MemCSF-1/CSF-1R interaction mediates a specific adhesion of NAF21 cells to stromal cells and allows stimulation of hematopoietic cells by stromal cell-derived factors expressed in a membrane-bound form or concentrated within the extracellular matrix. Thus, cytokine receptors deficient in mitogenic signalling may nevertheless have a regulatory role in hematopoietic progenitor cell proliferation by acting as adhesion molecules.

Induction of osteoclasts from CD14-positive human peripheral blood mononuclear cells by receptor activator of nuclear factor kappaB ligand (RANKL)

Osteoclasts are bone-resorbing cells that are derived from haemopoietic precursors, including cells present in peripheral blood. The recent identification of RANKL [receptor activator of nuclear factor (NF)-kappaB ligand], a new member of the tumour necrosis factor ligand superfamily that has a key role in osteoclastogenesis, has allowed the in vitro generation of osteoclasts in the absence of cells of the stromal/osteoblast lineage. Human peripheral blood mononuclear cells (PBMC) cultured in vitro with soluble RANKL and human macrophage colony-stimulating factor form osteoclasts. However, PBMC are heterogeneous, consisting of subsets of monocytes and lymphocytes as well as other blood cells. As the CD14 marker is strongly expressed on monocytes, the putative osteoclast precursor in peripheral blood, we have selected CD14(+) cells from PBMC to examine their osteoclastogenic potential and their expression of novel members of the tumour necrosis factor superfamily involved in osteoclastogenesis. Highly purified CD14(+) cells demonstrated mRNA expression of receptor activator of NF-kappaB, but no expression of RANKL or osteoprotegerin, whereas PBMC expressed mRNAs for all three factors. CD14(+) (but not CD14(-)) cells cultured on bone slices for 21 days with human macrophage colony-stimulating factor and soluble RANKL generated osteoclasts and showed extensive bone resorption. Similar numbers of osteoclasts were generated by 10(5) CD14(+) cells and 10(6) PBMC, but there was significantly less intra-assay variability with CD14(+) cells, suggesting the absence of stimulatory/inhibitory factors from these cultures. The ability of highly purified CD14(+) cells to generate osteoclasts will facilitate further characterization of the phenotype of circulating osteoclast precursors and cell interactions in osteoclastogenesis.

Human bone-derived cells support formation of human osteoclasts from arthroplasty-derived cells in vitro

Mononuclear osteoclast precursors are present in the wear-particle-associated macrophage infiltrate found in the membrane surrounding loose implants. These cells are capable of differentiating into osteoclastic bone-resorbing cells when co-cultured with the rat osteoblast-like cell line, UMR 106, in the presence of 1,25(OH)2 vitamin D3. In order to develop an in vitro model of osteoclast differentiation which more closely parallels the cellular microenvironment at the bone-implant interface in situ, we determined whether osteoblast-like human bone-derived cells were capable of supporting the differentiation of osteoclasts from arthroplasty-derived cells and analysed the humoral conditions required for this to occur. Long-term co-culture of arthroplasty-derived cells and human trabecular-bone-derived cells (HBDCs) resulted in the formation of numerous tartrate-resistant-acid-phosphatase (TRAP) and vitronectin-receptor (VNR)-positive multinucleated cells capable of extensive resorption of lacunar bone. The addition of 1,25(OH)2 vitamin D3 was not required for the formation of osteoclasts and bone resorption. During the formation there was release of substantial levels of M-CSF and PGE2. Exogenous PGE2 (10(-8) to 10(-6) M) was found to stimulate strongly the resorption of osteoclastic bone. Our study has shown that HBDCs are capable of supporting the formation of osteoclasts from mononuclear phagocyte precursors present in the periprosthetic tissues surrounding a loose implant. The release of M-CSF and PGE2 by activated cells at the bone-implant interface may be important for the formation of osteoclasts at sites of pathological bone resorption associated with aseptic loosening.

Cytokines in implantation

Implantation is a process that involves development, attachment and invasion of the blastocyst into the endometrium. Successful implantation requires appropriate communication between the embryo and maternal endometrium. There is evidence to suggest that cytokines produced by the maternal endometrium and the developing embryo play a crucial role in this signalling process. Although numerous cytokine-receptor pairs are expressed by the maternal endometrium and the embryo during implantation, functional knowledge of these cytokines is limited. Compelling data demonstrating a functional role for cytokines in implantation comes from studies using specific cytokine and cytokine receptor knockout mice. There are limited similar data for human implantation, but clinical correlative data and studies using in vitro models indicate that cytokines may have an important functional role in this process. Cytokines that appear to have a functional role in mammalian implantation include leukaemia inhibitory factor, interleukin 1, hepatocyte growth factor, stem cell factor, macrophage colony-stimulating factor and insulin-like growth factors. As implantation failure is a significant cause of natural and in vitro fertilization pregnancy failure, a better understanding of the functional role of these cytokine-receptor pairs is important for improving the diagnosis and treatment of infertility.

The colony-stimulating factors and collagen-induced arthritis: exacerbation of disease by M-CSF and G-CSF and requirement for endogenous M-CSF

There is increasing evidence that the colony-stimulating factors (CSFs) may play a part in chronic inflammatory autoimmune diseases, such as rheumatoid arthritis (RA). We examined the involvement of macrophage CSF (M-CSF or CSF-1) and granulocyte CSF (G-CSF) in collagen-induced arthritis (CIA), a murine model of RA. Daily injections of M-CSF or G-CSF, 20-24 days postprimary immunization with type II collagen, exacerbated disease symptoms in suboptimally immunized DBA/1 mice. Support for the involvement of endogenous M-CSF in CIA was obtained by studies in which neutralizing monoclonal antibody reduced the severity of established CIA and also by studies showing the resistance of M-CSF-deficient op/op mice to CIA induction. These studies show that M-CSF and G-CSF can be proinflammatory in CIA and provide evidence that macrophage- and granulocyte-lineage cells can exacerbate CIA. Our results also show that M-CSF-dependent cells are essential for CIA development, suggesting M-CSF may be a suitable target for therapeutic intervention in RA.

Sequential requirements for SCL/tal-1, GATA-2, macrophage colony-stimulating factor, and osteoclast differentiation factor/osteoprotegerin ligand in osteoclast development

OBJECTIVE

Osteoclasts are of hematopoietic origin. The mechanism by which hematopoietic stem cells are specified to the osteoclast lineage is unclear. To understand the process of generation and differentiation of this lineage of cells, we performed in vitro studies on the differentiation of embryonic stem cells.

MATERIALS AND METHODS

We examined the potential of mutant embryonic stem cell lines harboring targeted deletions of the GATA-1, FOG, SCL/tal-1, or GATA-2 genes to differentiate into osteoclasts and determined when these molecules function in osteoclast development.

RESULTS

The lack of GATA-1 or FOG did not affect osteoclastogenesis. In contrast, SCL/tal-1-null embryonic stem cells generated no osteoclasts. In the case of the loss of GATA-2, a small number of osteoclasts were generated. GATA-2-null osteoclasts were morphologically normal and the terminal maturation was not disturbed, but a defect was observed in the generation of osteoclast progenitors. Experiments using specific inhibitors that block the signaling through macrophage colony-stimulating factor and osteoclast differentiation factor/osteoprotegerin ligand suggested that GATA-2 seems to act earlier in osteoclastogenesis than these cytokines. Interestingly, macrophage colony-forming units were not severely reduced by the loss of GATA-2 compared to osteoclast progenitors.

CONCLUSION

These results indicate that osteocalsts need SCL/tal-1 at an early point in development, and that GATA-2 is required for generation of osteoclast progenitors but not for the later stages when macrophage colony-stimulating factor and osteoclast differentiation factor/ osteoprotegerin ligand are needed. We also demonstrated that osteoclast progenitors behave as a different population than macrophage colony-forming units.

Potential role of macrophage colony-stimulating factor in the proliferation of DEL cells

The replication and activation of both vascular smooth muscle cells and macrophages, which have previously entered the arterial wall, are key events in the atherosclerotic process. The importance of macrophage colony-stimulating factor (MCSF) in control of the growth/proliferation of both cell types confers to this compound a central role in the development of vascular lesions. In order to gain insight into the mechanisms of macrophage proliferation, we investigated the effect of MCSF upon the proliferation of DEL cells. DEL cells constitute a monocyte/histiocytic cell line that differentiates along a macrophage lineage following exposure to phorbol ester. DEL cells constitutively express MCSF, and its receptor MCSFR is encoded by c-fms. We examined whether MCSF might play a role in the proliferation of cultured DEL cells. [3H]Thymidine or 5-bromo-2-deoxyuridine (BrdU) incorporation was measured following the addition of recombinant MCSF or L929 cell supernatant (as a source of MCSF) to quiescent DEL cells. In DEL cells, serum-free L929 cell supernatant induced DNA synthesis in a dose-dependent manner, and such an effect could be blunted by pretreatment of L929 cell supernatant with anti-mouse MCSF antibody. In these cells, DNA synthesis could also be triggered in a dose-dependent manner by the addition of recombinant human MCSF (rh MCSF) or thrombin. These findings clearly show that MCSF influences DEL cell proliferation and suggest an autocrine loop activation. They indicate that MCSF plays an important role in the development of vascular lesions, which occur during atherosclerotic progression.