Canine macrophages can like human macrophages be in vitro activated toward the M2a subtype relevant in allergy

A systematic strategy for investigating the pharmacological effects and mechanism of traditional Chinese medicinal formula: Guilin Xiguashuang as a case

BACKGROUND

Traditional Chinese medicinal formula (TCMF) has specific advantages in treating diseases. However, the pharmacological effects and mechanism of TCMF composed of traditional Chinese medicines (TCM) with unclear active components or targets have not yet been fully elucidated.

OBJECTIVES

This research proposed a strategy for elucidating the pharmacological effects and mechanism to address this issue systematically.

METHODS

With Guilin Xiguashuang (GLXGS) taken as a case, this study newly provided the multi-level assays, which decomposes TCMF into components, TCM, and TCMF levels. The main pharmacological effects were acquired through a comprehensive analysis based on the active components, pharmacological effects of TCM, and clinical efficacy of TCMF, respectively. The core targets and pathways were further identified and verified to elucidate the mechanism.

RESULTS

The main pharmacological effects of GLXGS were anti-inflammatory, analgesic, antibacterial, immunoregulatory, and wound healing. Moreover, the mechanism analysis demonstrated that GLXGS was involved in the regulation of NF-κB and VEGF signaling pathways and core targets, such as IL-6 and TNF-α. Finally, unproven immunomodulatory and anti-inflammatory mechanism were verified using RAW264.7 and THP-1 cells. GLXGS was verified to down-regulate IL-6, IL-1β, TNF-α, and CD86 in lipopolysaccharides-stimulated RAW264.7 cells, while enhancing polarization in both RAW264.7 and THP-1 cells, which were consistent with analysis results.

CONCLUSION

The present research provides a systematic strategy for the pharmacological effect prediction and mechanism analysis of TCMF, which is of great significance for studying complex TCMF.

Tumor-associated macrophages in canine visceral hemangiosarcoma

Canine hemangiosarcoma (HSA) is a highly malignant tumor derived from hematopoietic stem cells and commonly occurs in visceral organs or skin. Visceral HSAs are particularly aggressive and progress rapidly despite multimodal treatment. Tumor-associated macrophages (TAMs) play a central role in carcinogenesis, tumor progression, and metastasis in humans and murine models. In this retrospective study, we investigated the prevalence and phenotype of TAMs in privately owned, treatment-naïve dogs with naturally occurring HSA. We used CD204 as a general macrophage marker and CD206 as a marker for M2-polarized macrophages. Formalin-fixed paraffin-embedded tissues from HSAs in the spleen (n = 9), heart (n = 6), and other locations (n = 12) from 17 dogs were sectioned and immunohistochemically labeled with CD204 and CD206 antibodies. The mean number of log(CD204)- and log(CD206)-positive cells and the ratio of log(CD206/CD204)-positive cells were compared with normal surrounding tissues and between tumor locations. There were significantly more macrophages and M2 macrophages, and a higher ratio of M2 macrophages to total macrophages in tumor hot spots (P = .0002, P < .0001, and P = .0002, respectively) and in tumor tissues outside of hot spots (P = .009, P = .002, and P = .007, respectively) than in normal surrounding tissues. There were no significant differences between tumor locations, but there was a trend toward higher numbers of CD204-positive macrophages within the splenic tumors. There was no association between histological parameters or clinical stage and TAM numbers or phenotype. As in humans, TAMs in dogs with HSA have a predominantly M2-skewed phenotype. Dogs with HSA could serve as excellent models to evaluate new TAM-reprogramming therapies.

Characterization of polarization states of canine monocyte derived macrophages

Macrophages can reversibly polarize into multiple functional subsets depending on their micro-environment. Identification and understanding the functionality of these subsets is relevant for the study of immune‑related diseases. However, knowledge about canine macrophage polarization is still in its infancy. In this study, we polarized canine monocytes using GM-CSF/IFN- γ and LPS towards M1 macrophages or M-CSF and IL-4 towards M2 macrophages and compared them to undifferentiated monocytes (M0). Polarized M1 and M2 macrophages were thoroughly characterized for morphology, surface marker features, gene profiles and functional properties. Our results showed that canine M1-polarized macrophages obtained a characteristic large, roundish, or amoeboid shape, while M2-polarized macrophages were smaller and adopted an elongated spindle-like morphology. Phenotypically, all macrophage subsets expressed the pan-macrophage markers CD14 and CD11b. M1-polarized macrophages expressed increased levels of CD40, CD80 CD86 and MHC II, while a significant increase in the expression levels of CD206, CD209, and CD163 was observed in M2-polarized macrophages. RNAseq of the three macrophage subsets showed distinct gene expression profiles, which are closely associated with immune responsiveness, cell differentiation and phagocytosis. However, the complexity of the gene expression patterns makes it difficult to assign clear new polarization markers. Functionally, undifferentiated -monocytes, and M1- and M2- like subsets of canine macrophages can all phagocytose latex beads. M2-polarized macrophages exhibited the strongest phagocytic capacity compared to undifferentiated monocytes- and M1-polarized cells. Taken together, this study showed that canine M1 and M2-like macrophages have distinct features largely in parallel to those of well-studied species, such as human, mouse and pig. These findings enable future use of monocyte derived polarized macrophages particularly in studies of immune related diseases in dogs.

Tumor-associated macrophages: Prognostic and therapeutic targets for cancer in humans and dogs

Macrophages are ancient, phagocytic immune cells thought to have their origins 500 million years ago in metazoan phylogeny. The understanding of macrophages has evolved to encompass their foundational roles in development, homeostasis, tissue repair, inflammation, and immunity. Notably, macrophages display high plasticity in response to environmental cues, capable of a strikingly wide variety of dynamic gene signatures and phenotypes. Macrophages are also involved in many pathological states including neural disease, asthma, liver disease, heart disease, cancer, and others. In cancer, most tumor-associated immune cells are macrophages, coined tumor-associated macrophages (TAMs). While some TAMs can display anti-tumor properties such as phagocytizing tumor cells and orchestrating an immune response, most macrophages in the tumor microenvironment are immunosuppressive and pro-tumorigenic. Macrophages have been implicated in all stages of cancer. Therefore, interest in manipulating macrophages as a therapeutic strategy against cancer developed as early as the 1970s. Companion dogs are a strong comparative immuno-oncology model for people due to documented similarities in the immune system and spontaneous cancers between the species. Data from clinical trials in humans and dogs can be leveraged to further scientific advancements that benefit both species. This review aims to provide a summary of the current state of knowledge on macrophages in general, and an in-depth review of macrophages as a therapeutic strategy against cancer in humans and companion dogs.

Distinct differences in immunological properties of equine orthobiologics revealed by functional and transcriptomic analysis using an activated macrophage readout system

Introduction

Multiple biological therapies for orthopedic injuries are marketed to veterinarians, despite a lack of rigorous comparative biological activity data to guide informed decisions in selecting a most effective compound. Therefore, the goal of this study was to use relevant bioassay systems to directly compare the anti-inflammatory and immunomodulatory activity of three commonly used orthobiological therapies (OTs): mesenchymal stromal cells (MSC), autologous conditioned serum (ACS), and platelet rich plasma (PRP).

Methods

Equine monocyte-derived macrophages were used as the readout system to compare therapies, including cytokine production and transcriptomic responses. Macrophages were stimulated with IL-1ß and treated 24 h with OTs, washed and cultured an additional 24 h to generate supernatants. Secreted cytokines were measured by multiplex immunoassay and ELISA. To assess global transcriptomic responses to treatments, RNA was extracted from macrophages and subjected to full RNA sequencing, using an Illumina-based platform. Data analysis included comparison of differentially expressed genes and pathway analysis in treated vs. untreated macrophages.

Results

All treatments reduced production of IL-1ß by macrophages. Secretion of IL-10 was highest in MSC-CM treated macrophages, while PRP lysate and ACS resulted in greater downregulation of IL-6 and IP-10. Transcriptomic analysis revealed that ACS triggered multiple inflammatory response pathways in macrophages based on GSEA, while MSC generated significant downregulation of inflammatory pathways, and PRP lysate induced a mixed immune response profile. Key downregulated genes in MSC-treated cultures included type 1 and type 2 interferon response, TNF-α and IL-6. PRP lysate cultures demonstrated downregulation of inflammation-related genes IL-1RA, SLAMF9, ENSECAG00000022247 but concurrent upregulation of TNF-α, IL-2 signaling, and Myc targets. ACS induced upregulation of inflammatory IL-2 signaling, TNFα and KRAS signaling and hypoxia, but downregulation of MTOR signaling and type 1 interferon signaling.

Discussion

These findings, representing the first comprehensive look at immune response pathways for popular equine OTs, reveal distinct differences between therapies. These studies address a critical gap in our understanding of the relative immunomodulatory properties of regenerative therapies commonly used in equine practice to treat musculoskeletal disease and will serve as a platform from which further in vivo comparisons may build.

Canine polarized macrophages express distinct functional and transcriptomic profiles

Macrophage differentiation and function in disease states is highly regulated by the local microenvironment. For example, macrophage exposure to IFN-γ (interferon gamma) initiates the development of inflammatory (M1) macrophages, which acquire anti-tumoral and antimicrobial activity, while exposure to IL-4 (interleukin-4) and IL-13 (interleukin-13) drives an anti-inflammatory (M2) macrophage phenotype, which promotes healing and suppression of inflammatory responses. Previous studies of canine polarized macrophages have identified several surface markers that distinguished GM-CSF (granulocyte macrophage colony stimulating factor), IFN-γ and LPS (lipopolysaccharide) derived M1 macrophages or M2 macrophages; and reported a subset of genes that can be used to differentiate between polarization states. However, the need remains to understand the underlying biological mechanisms governing canine macrophage polarization states. Therefore, in the present study we used transcriptome sequencing, a larger panel of flow cytometry markers, and the addition of antimicrobial functional assays to further characterize canine macrophage polarization. Transcriptome analysis revealed unique, previously unreported signatures and pathways for polarized canine M1 and M2 macrophages. New flow cytometric markers were also identified, along with new characterization of how macrophage polarization impacted antimicrobial functions. Taken together, the findings reported here provide new insights into canine macrophage biology and identify new tools for the evaluation of polarized macrophages in dogs.

In Vitro Antiparasitic Activities of Monovalent Ionophore Compounds for Human and Canine Leishmaniases

The leishmaniases are vector-borne parasitic diseases affecting humans and animals, with high mortality rates in endemic countries. Infected dogs represent the main reservoir of infection. Disease control is mainly based on chemotherapy, which, at present, shows serious drawbacks both in humans and dogs. Therefore, the discovery or repurposing of new treatments is mandatory. Here, three monovalent ionophores (salinomycin, monensin, nigericin) were tested against promastigotes of Leishmania (L.) infantum, Leishmania tropica, and Leishmania braziliensis, and against amastigotes of L. infantum within human and, for the first time, canine macrophages. All three drugs were leishmanicidal against all Leishmania spp. promastigotes with IC50 values between 7.98 and 0.23 µM. Monensin and nigericin showed IC50 values < 1 µM, whereas salinomycin was the least active compound (IC50 > 4 µM). Notably, the ionophores killed L. infantum amastigotes within human THP-1 cells with IC50 values ranging from 1.67 to 1.93 µM, but they only reduced by 27−37% the parasite burden in L. infantum-infected canine macrophages, showing a host-specific efficacy. Moreover, a selective higher toxicity against canine macrophages was observed. Overall, repurposed ionophores have the potential to be further investigated as anti-Leishmania agents, but different drug options may be required to tackle human or canine leishmaniases.

The Effect of Arginase on Canine T-Lymphocyte Functions and its Modulation by All-Trans Retinoid Acid (ATRA) in Canine Monocyte-Derived Macrophages

Immunosuppressive myeloid cells in the tumor microenvironment play a major role in suppressing tumor immunity via the production of arginase, IL-10, and others. The objectives of this study were to determine the ability of all-trans retinoic acid (ATRA) to decrease the expression of arginase and other soluble mediators by canine monocyte-derived macrophages (MDMs) and to determine the inhibitory activity of arginase on canine T-lymphocytes. The immunomodulatory ability of ATRA (2 µM) on canine MDMs was evaluated via reverse transcription quantitative PCR (RT-qPCR), flow cytometry, arginase activity assay, and enzyme-linked immunoassay (ELISA). Arginase effects on T-lymphocyte phenotype and proliferation were then evaluated by flow cytometry. ATRA consistently decreased MDM expression of IL6, TGFB1, NOS2, ARG1, and CIITA transcripts, by approximately 2-4-fold, although this did not reach statistical significance for ARG1 or CIITA. Furthermore, arginase activity was decreased in ATRA-treated MDMs while the MDM phenotype remained unchanged. Arginase decreased the expression of granzyme B on CD8+ T-lymphocytes and inhibited CD4+ and CD8+ T-lymphocyte proliferation. These findings suggested that ATRA could inhibit canine MDM production of soluble inflammatory/immunosuppressive mediators. These data also revealed that arginase decreased canine T-lymphocyte proliferation and granzyme B expression. Further studies are needed to determine whether ATRA could reverse the immunosuppressive effects of myeloid cells on canine T-lymphocytes in vivo.

Changes in gene expression profiles and cytokine secretions in peripheral monocytes by treatment with small extracellular vesicles derived from a canine lymphoma cell line

Interactions between tumor and immune cells within the tumor microenvironment play an important role in tumor progression, and small extracellular vesicles (EVs) derived from these tumor cells have been shown to exert immunomodulatory effects on various immune cells, including macrophages and lymphocytes. Although the immunomodulatory effects of small EVs derived from human cancer cells have been intensively investigated, few studies have investigated the effects of lymphoma-derived small EVs on macrophages in both human and veterinary medicine. Here, we evaluated the effects of canine lymphoma-derived small EVs on canine primary monocytes, which are the major source of macrophages in neoplastic tissues. Comprehensive gene expression analysis of these treated monocytes revealed their distinct activation via the Toll-like receptor (TLR) and NF-κβ signaling pathways. In addition, treatment with lymphoma small EVs increased the secretion of MCP-1, which induces the infiltration and migration of monocytes and lymphocytes in neoplastic and cancer tissues. The results of this study indicate that canine lymphoma small EVs activate monocytes, possibly through the activation of TLR and NF-κβ signaling pathways, and induce monocytes to secrete of MCP-1, which might contribute to immune cell infiltration within the tumor microenvironment.

Functional Evaluation of Anti-TNF-α Affibody Molecules in Biochemical Detection and Inhibition to Signalling Pathways of a Synovial Cell

BACKGROUND

An affibody molecule obtained from a bioengineered staphylococcal protein was previously shown to act as an affinity binder for a wide range of targets and develop Tumour Necrosis Factor α (TNF-α)-binding clones.

METHODS

In this study, we demonstrated that affibody molecules against TNF-α could bind to recombinant TNF-α on the membrane for biochemical detection. In addition, we examined whether the affibody molecules could block binding between recombinant TNF-α and its receptor on MH7A synovial cells.

RESULTS

When a TNF-α-binding affibody was added, the production level of inflammatory mediators IL-6 and MMP-3 in MH7A were found to decrease up to 44%. Additionally, proliferation of synovial cells was also inhibited by the addition of TNF-α to cultivation media.

CONCLUSION

These results suggest that affibody molecules against TNF-α could be candidate molecules for the detection of TNF-α during biochemical analysis and pharmacotherapy for rheumatoid arthritis.

Immunohistochemical evaluation of immune cell infiltration in canine gliomas

Evasion of the immune response is an integral part of the pathogenesis of glioma. In humans, important mechanisms of immune evasion include recruitment of regulatory T cells (Tregs) and polarization of macrophages toward an M2 phenotype. Canine glioma has a robust immune cell infiltrate that has not been extensively characterized. The purpose of this study was to determine the distribution of immune cells infiltrating spontaneous intracranial canine gliomas. Seventy-three formalin-fixed, paraffin-embedded tumor samples were evaluated using immunohistochemistry for CD3, forkhead box 3 (FOXP3), CD20, Iba1, calprotectin (Mac387), CD163, and indoleamine 2,3-dioxygenase (IDO). Immune cell infiltration was present in all tumors. Low-grade and high-grade gliomas significantly differed in the numbers of FoxP3+ cells, Mac387+ cells, and CD163+ cells (P = .006, .01, and .01, respectively). Considering all tumors, there was a significant increase in tumor area fraction of CD163 compared to Mac387 (P < .0001), and this ratio was greater in high-grade tumors than in low-grade tumors (P = .005). These data warrant further exploration into the roles of macrophage repolarization or Treg interference therapy in canine glioma.

Polyphenols and Cannabidiol Modulate Transcriptional Regulation of Th1/Th2 Inflammatory Genes Related to Canine Atopic Dermatitis

Canine atopic dermatitis (AD) is a multifactorial allergic disease associated with immune and abnormal skin barrier dysfunction and it is one of the primary causes of pruritus. Using a novel in vitro model of AD, here we tried to revert the alteration of transcriptional regulation of AD canine key genes testing a nutraceutical mixture containing flavonoids, stilbene, and cannabinoids, which are already well-known for their applications within dermatology diseases. The nutraceutical mixture induced in inflamed cells a significant downregulation (p < 0.05) of the gene expression of ccl2, ccl17, and tslp in keratinocytes and of ccl2, ccl17, and il31ra in monocytes. Consistent with the observed alterations of tslp, ccl2, ccl17, and il31ra messenger RNA (mRNA) levels, a significant increase (p < 0.05) of DNA methylation at specific CpG sites on the gene regulatory regions was found. These results lay the foundation for the use of these natural bioactives in veterinary medicine and provide a model for deeper understanding of their mechanisms of action, with potential translation to human research.

P2Y2 and P2X4 Receptors Mediate Ca2+ Mobilization in DH82 Canine Macrophage Cells

Purinergic receptors of the P2 subclass are commonly found in human and rodent macrophages where they can be activated by adenosine 5'-triphosphate (ATP) or uridine 5'-triphosphate (UTP) to mediate Ca²⁺ mobilization, resulting in downstream signalling to promote inflammation and pain. However, little is understood regarding these receptors in canine macrophages. To establish a macrophage model of canine P2 receptor signalling, the expression of these receptors in the DH82 canine macrophage cell line was determined by reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. P2 receptor function in DH82 cells was pharmacologically characterised using nucleotide-induced measurements of Fura-2 AM-bound intracellular Ca²⁺. RT-PCR revealed predominant expression of P2X4 receptors, while immunocytochemistry confirmed predominant expression of P2Y₂ receptors, with low levels of P2X4 receptor expression. ATP and UTP induced robust Ca²⁺ responses in the absence or presence of extracellular Ca²⁺. ATP-induced responses were only partially inhibited by the P2X4 receptor antagonists, 2',3'-O-(2,4,6-trinitrophenyl)-ATP (TNP-ATP), paroxetine and 5-BDBD, but were strongly potentiated by ivermectin. UTP-induced responses were near completely inhibited by the P2Y₂ receptor antagonists, suramin and AR-C118925. P2Y₂ receptor-mediated Ca²⁺ mobilization was inhibited by U-73122 and 2-aminoethoxydiphenyl borate (2-APB), indicating P2Y₂ receptor coupling to the phospholipase C and inositol triphosphate signal transduction pathway. Together this data demonstrates, for the first time, the expression of functional P2 receptors in DH82 canine macrophage cells and identifies a potential cell model for studying macrophage-mediated purinergic signalling in inflammation and pain in dogs.

Immunotherapy Targeting Tumor-Associated Macrophages

Macrophages are phagocytic cells that play a broad role in maintaining body homeostasis and defense against foreign pathogens; whereas tumor-associated macrophages (TAMs) support tumor growth and metastasis by promoting cancer cell proliferation and invasion, immunosuppression, and angiogenesis, which is closely related to the poor prognosis in almost all solid tumors. Hence, deep-insight knowledge into TAMs can provide an opportunity to discover more effective strategies for cancer therapeutics. So far, a large number of therapeutic agents targeting TAMs are in clinical trials. In this review, we introduce an extensive overview about macrophages and macrophage-targeting agents.

IgE Antibodies against Cancer: Efficacy and Safety

Immunoglobulin E (IgE) antibodies are well known for their role in allergic diseases and for contributions to antiparasitic immune responses. Properties of this antibody class that mediate powerful effector functions may be redirected for the treatment of solid tumours. This has led to the rise of a new class of therapeutic antibodies to complement the armamentarium of approved tumour targeting antibodies, which to date are all IgG class. The perceived risk of type I hypersensitivity reactions following administration of IgE has necessitated particular consideration in the development of these therapeutic agents. Here, we bring together the properties of IgE antibodies pivotal to the hypothesis for superior antitumour activity compared to IgG, observations of in vitro and in vivo efficacy and mechanisms of action, and a focus on the safety considerations for this novel class of therapeutic agent. These include in vitro studies of potential hypersensitivity, selection of and observations from appropriate in vivo animal models and possible implications of the high degree of glycosylation of IgE. We also discuss the use of ex vivo predictive and monitoring clinical tools, as well as the risk mitigation steps employed in, and the preliminary outcomes from, the first-in-human clinical trial of a candidate anticancer IgE therapeutic.

Peripheral mechanisms of arthritic pain: A proposal to leverage large animals for in vitro studies

Pain arising from musculoskeletal disorders such as arthritis is one of the leading causes of disability. Whereas the past 20-years has seen an increase in targeted therapies for rheumatoid arthritis (RA), other arthritis conditions, especially osteoarthritis, remain poorly treated. Although modulation of central pain pathways occurs in chronic arthritis, multiple lines of evidence indicate that peripherally driven pain is important in arthritic pain. To understand the peripheral mechanisms of arthritic pain, various in vitro and in vivo models have been developed, largely in rodents. Although rodent models provide numerous advantages for studying arthritis pathogenesis and treatment, the anatomy and biomechanics of rodent joints differ considerably to those of humans. By contrast, the anatomy and biomechanics of joints in larger animals, such as dogs, show greater similarity to human joints and thus studying them can provide novel insight for arthritis research. The purpose of this article is firstly to review models of arthritis and behavioral outcomes commonly used in large animals. Secondly, we review the existing in vitro models and assays used to study arthritic pain, primarily in rodents, and discuss the potential for adopting these strategies, as well as likely limitations, in large animals. We believe that exploring peripheral mechanisms of arthritic pain in vitro in large animals has the potential to reduce the veterinary burden of arthritis in commonly afflicted species like dogs, as well as to improve translatability of pain research into the clinic.

IgE Antibodies: From Structure to Function and Clinical Translation

Immunoglobulin E (IgE) antibodies are well known for their role in mediating allergic reactions, and their powerful effector functions activated through binding to Fc receptors FcεRI and FcεRII/CD23. Structural studies of IgE-Fc alone, and when bound to these receptors, surprisingly revealed not only an acutely bent Fc conformation, but also subtle allosteric communication between the two distant receptor-binding sites. The ability of IgE-Fc to undergo more extreme conformational changes emerged from structures of complexes with anti-IgE antibodies, including omalizumab, in clinical use for allergic disease; flexibility is clearly critical for IgE function, but may also be exploited by allosteric interference to inhibit IgE activity for therapeutic benefit. In contrast, the power of IgE may be harnessed to target cancer. Efforts to improve the effector functions of therapeutic antibodies for cancer have almost exclusively focussed on IgG1 and IgG4 subclasses, but IgE offers an extremely high affinity for FcεRI receptors on immune effector cells known to infiltrate solid tumours. Furthermore, while tumour-resident inhibitory Fc receptors can modulate the effector functions of IgG antibodies, no inhibitory IgE Fc receptors are known to exist. The development of tumour antigen-specific IgE antibodies may therefore provide an improved immune functional profile and enhanced anti-cancer efficacy. We describe proof-of-concept studies of IgE immunotherapies against solid tumours, including a range of in vitro and in vivo evaluations of efficacy and mechanisms of action, as well as ex vivo and in vivo safety studies. The first anti-cancer IgE antibody, MOv18, the clinical translation of which we discuss herein, has now reached clinical testing, offering great potential to direct this novel therapeutic modality against many other tumour-specific antigens. This review highlights how our understanding of IgE structure and function underpins these exciting clinical developments.

Activated Macrophages of Monocytic Origin Predominantly Express Proinflammatory Cytokine Genes, Whereas Kupffer Cells Predominantly Express Anti-Inflammatory Cytokine Genes

In the central nervous system and in the liver, the macrophage populations are represented exclusively by descendants of the hematopoietic progenitor cells of the yolk sac. The reasons for such differential distribution of macrophages are not fully understood. We found that, as can be judged by corresponding changes in the expression of CD86 and CD163 markers, the transient macrophages of monocytic lineage are more sensitive to activating stimuli. The two macrophage populations have distinct patterns of gene expression, which is particularly noticeable for M1- and M2-associated genes. For instance, Kupffer cells more readily develop and longer maintain the elevated expression levels of Il4, Il10, and Il13 upon the activation; by contrast, the macrophages of monocytic lineage express Il1b, Il12a, and Tnfα upon the activation. The obtained results allow us to conclude that the in vitro activated Kupffer cells of the liver are committed to M2 phenotype, whereas the in vitro activated monocyte-derived macrophages show a typical M1 behavior. These observations are likely to reflect the situation in the in vivo microenvironments.

A canine in vitro model for evaluation of marrow-derived mesenchymal stromal cell-based bone scaffolds

Tissue engineered bone grafts based on bone marrow mesenchymal stromal cells (MSCs) are being actively developed for craniomaxillofacial (CMF) applications. As for all tissue engineered implants, the bone-regenerating capacity of these MSC-based grafts must first be evaluated in animal models prior to human trials. Canine models have traditionally resulted in improved clinical translation of CMF grafts relative to other animal models. However, the utility of canine CMF models for evaluating MSC-based bone grafts rests on canine MSCs (cMSCs) responding in a similar manner to scaffold-based stimuli as human MSCs (hMSCs). Herein, cMSC and hMSC responses to polyethylene glycol (PEG)-based scaffolds were therefore compared in the presence or absence of osteoinductive polydimethylsiloxane (PDMS). Notably, the conjugation of PDMS to PEG-based constructs resulted in increases in both cMSC and hMSC osteopontin and calcium deposition. Based on these results, cMSCs were further used to assess the efficacy of tethered bone morphogenic protein 2 (BMP2) in enhancing PEG-PDMS scaffold osteoinductivity. Addition of low doses of tethered BMP2 (100 ng/mL) to PEG-PDMS systems increased cMSC expression of osterix and osteopontin compared to both PEG-PDMS and PEG-BMP2 controls. Furthermore, these increases were comparable to effects seen with up to five-times higher BMP2 doses noted in literature. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2382-2393, 2018.