Cloning and sequencing of cDNA encoding bovine macrophage colony-stimulating factor (bM-CSF) and expression of recombinant bM-CSF using baculovirus

Cloning and expression of feline colony stimulating factor receptor (CSF-1R) and analysis of the species specificity of stimulation by colony stimulating factor-1 (CSF-1) and interleukin-34 (IL-34)

Colony stimulating factor (CSF-1) and its receptor, CSF-1R, have been previously well studied in humans and rodents to dissect the role they play in development of cells of the mononuclear phagocyte system. A second ligand for the CSF-1R, IL-34 has been described in several species. In this study, we have cloned and expressed the feline CSF-1R and examined the responsiveness to CSF-1 and IL-34 from a range of species. The results indicate that pig and human CSF-1 and human IL-34 are equally effective in cats, where both mouse CSF-1 and IL-34 are significantly less active. Recombinant human CSF-1 can be used to generate populations of feline bone marrow and monocyte derived macrophages that can be used to further dissect macrophage-specific gene expression in this species, and to compare it to data derived from mouse, human and pig. These results set the scene for therapeutic use of CSF-1 and IL-34 in cats.

Pivotal Advance: Avian colony-stimulating factor 1 (CSF-1), interleukin-34 (IL-34), and CSF-1 receptor genes and gene products

Macrophages are involved in many aspects of development, host defense, pathology, and homeostasis. Their normal differentiation, proliferation, and survival are controlled by CSF-1 via the activation of the CSF1R. A recently discovered cytokine, IL-34, was shown to bind the same receptor in humans. Chicken is a widely used model organism in developmental biology, but the factors that control avian myelopoiesis have not been identified previously. The CSF-1, IL-34, and CSF1R genes in chicken and zebra finch were identified from respective genomic/cDNA sequence resources. Comparative analysis of the avian CSF1R loci revealed likely orthologs of mammalian macrophage-specific promoters and enhancers, and the CSF1R gene is expressed in the developing chick embryo in a pattern consistent with macrophage-specific expression. Chicken CSF-1 and IL-34 were expressed in HEK293 cells and shown to elicit macrophage growth from chicken BM cells in culture. Comparative sequence and co-evolution analysis across all vertebrates suggests that the two ligands interact with distinct regions of the CSF1R. These studies demonstrate that there are two separate ligands for a functional CSF1R across all vertebrates.

Cytokine mRNA profiles in bovine macrophages stimulated with Trypanosoma congolense

It is known that different breeds of cattle display differential susceptibilities to Trypanosome congolense infections, and that N'Dama cattle remain more productive after infection than Boran cattle which are more susceptible to T. congolense. Macrophages from both breeds were cultured in vitro and the expressions of a number of cytokines and iNOS mRNA were analyzed using real time RT-PCR after stimulation with antibody-opsonized trypanosomes. No significant difference was seen between the responses of the two breeds. However, RNA levels of TNF-alpha in the IFN-gamma-primed macrophages were about 100-fold higher than those in the non-primed macrophages. A significant ten-fold decrease was seen for the anti-inflammatory cytokine IL-10. These results indicate that priming of the cells with IFN-gamma cause a serious shift toward an inflammatory response.

Development of goldfish macrophages in vitro

Over 100 years after the first description of macrophages by Metchnikoff, there are still questions as to the mechanisms leading to the heterogeneity of their lineage. Current views are based on the mononuclear phagocyte system (MPS) theory, where all mammalian macrophages are derived from circulating blood monocytes and ultimately from hematopoietic stem cells in the bone marrow. Our studies on the regulation of fish macrophage development, suggested that teleosts have alternate pathways of monopoiesis, which undoubtedly contribute to macrophage heterogeneity in the goldfish. Macrophage heterogeneity has been attributed to a network of positive and negative regulators of macrophage development, including soluble mediators known as colony-stimulating factors of which two (M-CSF and GM-CSF) promote formation and growth of mature macrophages. In contrast to our knowledge of CSFs and their receptors in mammals, there is no published information about fish macrophage CSFs. Since fish macrophages generate their own growth factors, it is reasonable to assume that pathways of fish macrophage development and hematopoiesis may be distinct from those of mammalian macrophages. More importantly, the presence of fish progenitor/stem cells and developing macrophages in long-term cultures, allowed us to address pathways of macrophage differentiation, which could not be addressed in mammalian macrophage culture systems. Characterization of primary kidney macrophage (PKM) cultures from goldfish hematopoietic tissues (kidney) indicated that three distinct subpopulations developed in response to endogenous macrophage growth factors. These macrophage subpopulations expressed several differentiation markers, including the hematopoietic stem cell antigen AC133, c-kit, granulin, CD63, macrosialin, c/EBPbeta, legumain, and the colony-stimulating factor receptor-1 (CSF-1R). In the goldfish, there appeared to be a stringent control between those early progenitors that self-renewed, and those that were recruited into the maturation pathways. We report that upon commitment, goldfish macrophages developed through two distinct differentiation pathways: one consistent with the "classical" pathway (MPS) of macrophage development (progenitors-->monocytes-->mature macrophages), and an "alternate" pathway (AP-macrophages) where mature macrophages appeared to rapidly develop from early progenitors in the absence of an intermediate monocyte stage. AP-macrophages represent a unique subset of spontaneously growing cells. Their self-renewal was promoted by endogenous macrophage growth factors (MGF), and effectively controlled by a novel soluble form of the CSF-1R (sCSF-1R). The discovery of sCSF-1R in the goldfish highlights the inherent complexity in the hematopoietic regulatory machinery of teleosts.

Generation of Multinucleated Giant Cells In Vitro from Bovine Monocytes and Macrophages

The generation of multinucleated giant cells (MGC) from cells of the bovine monocyte-macrophage lineage was investigated. Freshly isolated monocytes were incubated with the conditioned medium (CM) of peripheral blood mononuclear cell cultures treated with Concanavalin A for 1-4 days (CM1 to CM4). Only CM1 generated MGC despite similar concentrations of IFNgamma in all CMs. Nevertheless, MGC formation from monocytes was enhanced by adding either macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF), MGC formations from macrophages were observed only when macrophages were cultured with GM-CSF plus CM. These results indicate that several mechanisms to generate MGC from bovine monocytes-macrophage lineage cells exist, and that GM-CSF is a major mediator of MGC formation in cattle.

Quantitation of bovine macrophage colony-stimulating factor in bovine serum by ELISA

We established an enzyme-linked immunosorbent assay (ELISA) system for the quantitation of bovine macrophage colony-stimulating factor (M-CSF) and used it to measure the serum M-CSF levels in bovine fetuses and calves. The average serum M-CSF level was 2.7+/-1.5 ng/ml in 39 calves under 100 days old, and 1.8+/-0.8 ng/ml in 15 cattle between 101 and 418 days old. Fetal sera samples (n = 6) prepared from cattle between 150 and 280 days of gestational age had a higher average level of M-CSF (8.8+/-1.4 ng/ml). Alteration in serum M-CSF levels in each individual calf was also measured. The serum levels of M-CSF in calves at 0-1 day after birth ranged from 0.52 to 7.3 ng/ml. During the period 113-125 days after birth, serum levels were around 1.4+/-0.39 ng/ml. Although serum M-CSF levels generally decreased as the age of calves advanced, differences among individuals, especially among newborn calves, were observed.

Gene expression of leukemia inhibitory factor (LIF) and macrophage colony stimulating factor (M-CSF) in bovine endometrium during early pregnancy

Leukemia inhibitory factor (LIF) and macrophage colony stimulating factor (M-CSF), members of the group of hemopoietic cytokines, play a primary role in the control of embryo development and implantation and in the growth of the placenta in humans and mice. Gene expressions of LIF and M-CSF were investigated using quantitative RT-PCR in bovine endometrial tissues during early and mid-pregnancy (Days 16-17, 20-21, 30-36, 48-49 and 74-140) and during the estrous cycle (Days 13-14). Leukemia inhibitory factor and M-CSF genes were expressed in all samples examined. Significant differences were found between the gene expression patterns of LIF and M-CSF. Leukemia inhibitory factor expression level at Days 48-49 was the highest in caruncular endometrium, however, the large variability negated any significant differences. Leukemia inhibitory factor expression levels in intercaruncular endometrium at Days 48-49 and 74-140 of pregnancy were greater than at Days 13-14 of the estrous cycle and at other days of pregnancy. No significant change was recognized in M-CSF expression levels in caruncular endometrium. Macrophage colony stimulating factor expression level in intercaruncular endometrium at Days 74-140 was greater than those of the other samples. These results suggest that LIF and M-CSF are produced in the endometrium and may play different roles in early and mid-pregnancy.