Placenta-Expanded Stromal Cell Therapy in a Rodent Model of Simulated Weightlessness.

Long duration spaceflight poses potential health risks to astronauts during flight and re-adaptation after return to Earth. There is an emerging need for NASA to provide successful and reliable therapeutics for long duration missions when capability for medical intervention will be limited. Clinically relevant, human placenta-derived therapeutic stromal cells (PLX-PAD) are a promising therapeutic alternative. We found that treatment of adult female mice with PLX-PAD near the onset of simulated weightlessness by hindlimb unloading (HU, 30 d) was well-tolerated and partially mitigated decrements caused by HU. Specifically, PLX-PAD treatment rescued HU-induced thymic atrophy, and mitigated HU-induced changes in percentages of circulating neutrophils, but did not rescue changes in the percentages of lymphocytes, monocytes, natural killer (NK) cells, T-cells and splenic atrophy. Further, PLX-PAD partially mitigated HU effects on the expression of select cytokines in the hippocampus. In contrast, PLX-PAD failed to protect bone and muscle from HU-induced effects, suggesting that the mechanisms which regulate the structure of these mechanosensitive tissues in response to disuse are discrete from those that regulate the immune- and central nervous system (CNS). These findings support the therapeutic potential of placenta-derived stromal cells for select physiological deficits during simulated spaceflight. Multiple countermeasures are likely needed for comprehensive protection from the deleterious effects of prolonged spaceflight.

Perinatal Cells: A Promising COVID-19 Therapy?

The COVID-19 pandemic has become a priority in the health systems of all nations worldwide. In fact, there are currently no specific drugs or preventive treatments such as vaccines. The numerous therapies available today aim to counteract the symptoms caused by the viral infection that in some subjects can evolve causing acute respiratory distress syndromes (ARDS) with consequent admission to intensive care unit. The exacerbated response of the immune system, through cytokine storm, causes extensive damage to the lung tissue, with the formation of edema, fibrotic tissues and susceptibility to opportunistic infections. The inflammatory picture is also aggravated by disseminated intravascular coagulation which worsens the damage not only to the respiratory system, but also to other organs. In this context, perinatal cells represent a valid strategy thanks to their strong immunomodulatory potential, their safety profile, the ability to reduce fibrosis and stimulate reparative processes. Furthermore, perinatal cells exert antibacterial and antiviral actions. This review therefore provides an overview of the characteristics of perinatal cells with a particular focus on the beneficial effects that they could have in patients with COVID-19, and more specifically for their potential use in the treatment of ARDS and sepsis.

Immunization with a Myelin-Derived Antigen Activates the Brain's Choroid Plexus for Recruitment of Immunoregulatory Cells to the CNS and Attenuates Disease Progression in a Mouse Model of ALS.

Amyotrophic lateral sclerosis (ALS) is a devastating fatal motor neuron disease, for which there is currently no cure or effective treatment. In this disease, local neuroinflammation develops along the disease course and contributes to its rapid progression. In several models of CNS pathologies, circulating immune cells were shown to display an indispensable role in the resolution of the neuroinflammatory response. The recruitment of such cells to the CNS involves activation of the choroid plexus (CP) of the brain for leukocyte trafficking, through a mechanism that requires IFN-γ signaling. Here, we found that in the mutant SOD1(G93A) (mSOD1) mouse model of ALS, the CP does not support leukocyte trafficking during disease progression, due to a local reduction in IFN-γ levels. Therapeutic immunization of mSOD1 mice with a myelin-derived peptide led to CP activation, and was followed by the accumulation of immunoregulatory cells, including IL-10-producing monocyte-derived macrophages and Foxp3(+) regulatory T cells, and elevation of the neurotrophic factors IGF-1 and GDNF in the diseased spinal cord parenchyma. The immunization resulted in the attenuation of disease progression and an increased life expectancy of the mSOD1 mice. Collectively, our results demonstrate that recruitment of immunoregulatory cells to the diseased spinal cord in ALS, needed for fighting off the pathology, can be enhanced by transiently boosting peripheral immunity to myelin antigens.

IFN-γ-dependent activation of the brain's choroid plexus for CNS immune surveillance and repair.

Infiltrating T cells and monocyte-derived macrophages support central nervous system repair. Although infiltration of leucocytes to the injured central nervous system has recently been shown to be orchestrated by the brain's choroid plexus, the immunological mechanism that maintains this barrier and regulates its activity as a selective gate is poorly understood. Here, we hypothesized that CD4(+) effector memory T cells, recently shown to reside at the choroid plexus stroma, regulate leucocyte trafficking through this portal through their interactions with the choroid plexus epithelium. We found that the naïve choroid plexus is populated by T helper 1, T helper 2 and regulatory T cells, but not by encephalitogenic T cells. In vitro findings revealed that the expression of immune cell trafficking determinants by the choroid plexus epithelium is specifically induced by interferon-γ. Tumour necrosis factor-α and interferon-γ reciprocally controlled the expression of their receptors by the choroid plexus epithelium, and had a synergistic effect in inducing the epithelial expression of trafficking molecules. In vivo, interferon-γ-dependent signalling controlled trafficking through the choroid plexus; interferon-γ receptor knockout mice exhibited reduced levels of T cells and monocyte entry to the cerebrospinal fluid and impaired recovery following spinal cord injury. Moreover, reduced expression of trafficking molecules by the choroid plexus was correlated with reduced CD4(+) T cells in the choroid plexus and cerebrospinal fluid of interferon-γ receptor knockout mice. Similar effect on the expression of trafficking molecules by the choroid plexus was found in bone-marrow chimeric mice lacking interferon-γ receptor in the central nervous system, or reciprocally, lacking interferon-γ in the circulation. Collectively, our findings attribute a novel immunological plasticity to the choroid plexus epithelium, allowing it to serve, through interferon-γ signalling, as a tightly regulated entry gate into the central nervous system for circulating leucocytes immune surveillance under physiological conditions, and for repair following acute injury.

Immunomodulation by poly-YE reduces organophosphate-induced brain damage.

Accidental organophosphate poisoning resulting from environmental or occupational exposure, as well as the deliberate use of nerve agents on the battlefield or by terrorists, remain major threats for multi-casualty events, with no effective therapies yet available. Even transient exposure to organophosphorous compounds may lead to brain damage associated with microglial activation and to long-lasting neurological and psychological deficits. Regulation of the microglial response by adaptive immunity was previously shown to reduce the consequences of acute insult to the central nervous system (CNS). Here, we tested whether an immunization-based treatment that affects the properties of T regulatory cells (Tregs) can reduce brain damage following organophosphate intoxication, as a supplement to the standard antidotal protocol. Rats were intoxicated by acute exposure to the nerve agent soman, or the organophosphate pesticide, paraoxon, and after 24 h were treated with the immunomodulator, poly-YE. A single injection of poly-YE resulted in a significant increase in neuronal survival and tissue preservation. The beneficial effect of poly-YE treatment was associated with specific recruitment of CD4(+) T cells into the brain, reduced microglial activation, and an increase in the levels of brain derived neurotrophic factor (BDNF) in the piriform cortex. These results suggest therapeutic intervention with poly-YE as an immunomodulatory supplementary approach against consequences of organophosphate-induced brain damage.

Excess circulating alternatively activated myeloid (M2) cells accelerate ALS progression while inhibiting experimental autoimmune encephalomyelitis.

BACKGROUND: Circulating immune cells including autoreactive T cells and monocytes have been documented as key players in maintaining, protecting and repairing the central nervous system (CNS) in health and disease. Here, we hypothesized that neurodegenerative diseases might be associated, similarly to tumors, with increased levels of circulating peripheral myeloid derived suppressor cells (MDSCs), representing a subset of suppressor cells that often expand under pathological conditions and inhibit possible recruitment of helper T cells needed for fighting off the disease. METHODS AND FINDINGS: We tested this working hypothesis in amyotrophic lateral sclerosis (ALS) and its mouse model, which are characterized by a rapid progression once clinical symptoms are evident. Adaptive transfer of alternatively activated myeloid (M2) cells, which homed to the spleen and exhibited immune suppressive activity in G93A mutant superoxide dismutase-1 (mSOD1) mice at a stage before emergence of disease symptoms, resulted in earlier appearance of disease symptoms and shorter life expectancy. The same protocol mitigated the inflammation-induced disease model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), which requires circulating T cells for disease induction. Analysis of whole peripheral blood samples obtained from 28 patients suffering from sporadic ALS (sALS), revealed a two-fold increase in the percentage of circulating MDSCs (LIN(-/Low)HLA-DR(-)CD33(+)) compared to controls. CONCLUSIONS: Taken together, these results emphasize the distinct requirements for fighting the inflammatory neurodegenerative disease, multiple sclerosis, and the neurodegenerative disease, ALS, though both share a local inflammatory component. Moreover, the increased levels of circulating MDSCs in ALS patients indicates the operation of systemic mechanisms that might lead to an impairment of T cell reactivity needed to overcome the disease conditions within the CNS. This high level of suppressive immune cells might represent a risk factor and a novel target for therapeutic intervention in ALS at least at the early stage.

Abnormal changes in NKT cells, the IGF-1 axis, and liver pathology in an animal model of ALS.

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing fatal neurodegenerative disorder characterized by the selective death of motor neurons (MN) in the spinal cord, and is associated with local neuroinflammation. Circulating CD4(+) T cells are required for controlling the local detrimental inflammation in neurodegenerative diseases, and for supporting neuronal survival, including that of MN. T-cell deficiency increases neuronal loss, while boosting T cell levels reduces it. Here, we show that in the mutant superoxide dismutase 1 G93A (mSOD1) mouse model of ALS, the levels of natural killer T (NKT) cells increased dramatically, and T-cell distribution was altered both in lymphoid organs and in the spinal cord relative to wild-type mice. The most significant elevation of NKT cells was observed in the liver, concomitant with organ atrophy. Hepatic expression levels of insulin-like growth factor (IGF)-1 decreased, while the expression of IGF binding protein (IGFBP)-1 was augmented by more than 20-fold in mSOD1 mice relative to wild-type animals. Moreover, hepatic lymphocytes of pre-symptomatic mSOD1 mice were found to secrete significantly higher levels of cytokines when stimulated with an NKT ligand, ex-vivo. Immunomodulation of NKT cells using an analogue of α-galactosyl ceramide (α-GalCer), in a specific regimen, diminished the number of these cells in the periphery, and induced recruitment of T cells into the affected spinal cord, leading to a modest but significant prolongation of life span of mSOD1 mice. These results identify NKT cells as potential players in ALS, and the liver as an additional site of major pathology in this disease, thereby emphasizing that ALS is not only a non-cell autonomous, but a non-tissue autonomous disease, as well. Moreover, the results suggest potential new therapeutic targets such as the liver for immunomodulatory intervention for modifying the disease, in addition to MN-based neuroprotection and systemic treatments aimed at reducing oxidative stress.

Attenuation of AD-like neuropathology by harnessing peripheral immune cells: local elevation of IL-10 and MMP-9.

Immunization with an altered myelin-derived peptide (MOG45D) improves recovery from acute CNS insults, partially via recruitment of monocyte-derived macrophages that locally display a regulatory activity. Here, we investigated the local alterations in the cellular and molecular immunological milieu associated with attenuation of Alzheimer's disease-like pathology following immunotherapy. We found that immunization of amyloid precursor protein/presenilin 1 double-transgenic mice with MOG45D peptide, loaded on dendritic cells, led to a substantial reduction of parenchymal and perivascular amyloid beta (Abeta)-plaque burden and soluble Abeta((1-42)) peptide levels as well as reduced astrogliosis and levels of a key glial scar protein (chondroitin sulphate proteoglycan). These changes were associated with a shift in the local innate immune response, manifested by increased Iba1+/CD45(high) macrophages that engulfed Abeta, reduced pro-inflammatory (tumor necrosis factor-alpha) and increased anti-inflammatory (interleukin-10) cytokines, as well as a significant increase in growth factors (IGF-1 and TGFbeta) in the brain. Furthermore, the levels of matrix metalloproteinase-9, an enzyme shown to degrade Abeta and is associated with glial scar formation, were significantly elevated in the brain following immunization. Altogether, these results indicate that boosting systemic immune cells leads to a local immunomodulation manifested by elevated levels of anti-inflammatory cytokines and metalloproteinases that contribute to ameliorating Alzheimer's disease pathology.

Application of glatiramer acetate to neurodegenerative diseases beyond multiple sclerosis: the need for disease-specific approaches.

Adaptive and innate immunity, if well controlled, contribute to the maintenance of the CNS, as well as to downregulation of adverse acute and chronic neurological conditions. T cells that recognize CNS antigens are needed to activate resident immune cells and to recruit blood-borne monocytes, which act to restore homeostasis and facilitate repair. However, boosting such a T-cell response in a risk-free way requires a careful choice of the antigen, carrier, and regimen. A single vaccination with CNS-derived peptides or their weak agonists reduces neuronal loss in animal models of acute neurodegeneration. Repeated injections are needed to maintain a long-lasting effect in chronic neurodegenerative conditions, yet the frequency of the injections seems to have a critical effect on the outcome. An example is glatiramer acetate, a compound that is administered in a daily regimen to patients with multiple sclerosis. A single injection of glatiramer acetate, with or without an adjuvant, is neuroprotective in some animal models of acute CNS injuries. However, in an animal model of amyotrophic lateral sclerosis, a single injection of adjuvant-free glatiramer acetate is insufficient, while daily injections are not only ineffective but can carry an increased risk of mortality in female mice.Thus, considering immune-based therapies as a single therapy, rather than as a family of therapies that are regimen dependent, may be misleading. Moreover, the vaccination regimen and administration of a compound, even one shown to be safe in humans for the treatment of a particular neurodegenerative disease, must be studied in preclinical experiments before it is tested in a clinical trial for a novel indication; otherwise, an effective drug in a certain regimen for one disease may be ineffective or even carry risks when used for another disorder.

Selective ablation of bone marrow-derived dendritic cells increases amyloid plaques in a mouse Alzheimer's disease model.

We have recently shown that the ability of microglia to effectively fight off aggregated beta-amyloid plaque formation and cognitive loss in transgenic mouse models of Alzheimer's disease (Tg-AD), is augmented in response to T-cell-based immunization, using glatiramer acetate (GA). The immunization increases incidence of local CD11c+ dendritic-like cells. It is unclear, however, whether these dendritic cells are derived from resident microglia or from the bone marrow. To determine the origin of this dendritic-cell population, we used chimeric mice whose bone marrow-derived cells express a transgene that allows the cells to be specifically ablated by diphtheria toxin. We show here that T-cell-based immunization of these mice, using GA, induced the recruitment of bone marrow-derived dendritic cells. Depletion of the dendritic cells by systemic injection of diphtheria toxin resulted in significantly increased formation of amyloid plaques. Thus, recruitment of bone marrow-derived dendritic cells evidently plays a role in reducing plaque formation in a mouse model of Alzheimer's disease.

Microglia can be induced by IFN-gamma or IL-4 to express neural or dendritic-like markers.

Microglia are resident cells in the central nervous system (CNS), of hematopoietic origin with a high plasticity. In this study, we examined whether adaptive immune system, involving in CNS maintenance and repair, can induce microglia to express markers of neural cells. We show that long exposure (above 10 days) of microglia to low doses (10 ng/ml) of the 'proinflammatory' T-cell derived cytokine, IFN-gamma, induced them to express neuronal markers including gamma-aminobutyric acid (GABA) and glutamic acid decarboxylase (GAD-67). In contrast, exposure of microglia to low doses (10 ng/ml) of the 'anti-inflammatory' T-cell derived cytokine, IL-4, induced the expression of oligodendrocyte markers and dendritic cell (DC) marker, CD11c. The microglial origin of the neural-like cells was confirmed using microglia from transgenic mice expressing GFP under promoter of the chemokine fractalkine receptor CX(3)CR1, and diphtheria toxin receptor, under CD11c promoter. This study emphasizes that microglial plasticity includes their ability to give rise to neural-like cells and shows that cytokines produced by the adaptive immune system are involved in these processes.

Glatiramer acetate fights against Alzheimer's disease by inducing dendritic-like microglia expressing insulin-like growth factor 1.

Alzheimer's disease (AD) is characterized by plaque formation, neuronal loss, and cognitive decline. The functions of the local and systemic immune response in this disease are still controversial. Using AD double-transgenic (APP/PS1) mice, we show that a T cell-based vaccination with glatiramer acetate, given according to a specific regimen, resulted in decreased plaque formation and induction of neurogenesis. It also reduced cognitive decline, assessed by performance in a Morris water maze. The vaccination apparently exerted its effect by causing a phenotype switch in brain microglia to dendritic-like (CD11c) cells producing insulin-like growth factor 1. In vitro findings showed that microglia activated by aggregated beta-amyloid, and characterized as CD11b(+)/CD11c(-)/MHC class II(-)/TNF-alpha(+) cells, impeded neurogenesis from adult neural stem/progenitor cells, whereas CD11b(+)/CD11c(+)/MHC class II(+)/TNF-alpha(-) microglia, a phenotype induced by IL-4, counteracted the adverse beta-amyloid-induced effect. These results suggest that dendritic-like microglia, by facilitating the necessary adjustment, might contribute significantly to the brain's resistance to AD and argue against the use of antiinflammatory drugs.

Induction and blockage of oligodendrogenesis by differently activated microglia in an animal model of multiple sclerosis.

The role of activated microglia (MG) in demyelinating neurodegenerative diseases such as multiple sclerosis is controversial. Here we show that high, but not low, levels of IFN-gamma (a cytokine associated with inflammatory autoimmune diseases) conferred on rodent MG a phenotype that impeded oligodendrogenesis from adult neural stem/progenitor cells. IL-4 reversed the impediment, attenuated TNF-alpha production, and overcame blockage of IGF-I production caused by IFN-gamma. In rodents with acute or chronic EAE, injection of IL-4-activated MG into the cerebrospinal fluid resulted in increased oligodendrogenesis in the spinal cord and improved clinical symptoms. The newly formed oligodendrocytes were spatially associated with MG expressing MHC class II proteins and IGF-I. These results point to what we believe to be a novel role for MG in oligodendrogenesis from the endogenous stem cell pool.