Role of microglia in embryonic neurogenesis.

Microglia begin colonizing the developing brain as early as embryonic day 9, prior to the emergence of neurons and other glia. Their ontogeny is also distinct from other central nervous system cells, as they derive from yolk sac hematopoietic progenitors and not neural progenitors. In this review, we feature these unique characteristics of microglia and assess the spatiotemporal similarities between microglia colonization of the central nervous system and embryonic neurogenesis. We also infer to existing evidence for microglia function from embryonic through to postnatal neurodevelopment to postulate roles for microglia in neurogenesis.

Human mesenchymal stromal cells modulate T-cell immune response via transcriptomic regulation.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) have been identified as pan-immunosuppressant in various in vitro and in vivo inflammatory models. Although the immunosuppressive activity of MSCs has been explored in various contexts, the precise molecular signaling pathways that govern inhibitory functions remain poorly elucidated. METHODS: By using a microarray-based global gene expression profiling system, this study aimed to decipher the underlying molecular pathways that may mediate the immunosuppressive activity of umbilical cord-derived MSCs (UC-MSCs) on activated T cells. RESULTS: In the presence of UC-MSCs, the proliferation of activated T cells was suppressed in a dose-depended manner by cell-to-cell contact mode via an active cell-cycle arrest at the G0/G1 phase of the cell cycle. The microarray analysis revealed that particularly, IFNG, CXCL9, IL2, IL2RA and CCND3 genes were down-regulated, whereas IL11, VSIG4, GFA1, TIMP3 and BBC3 genes were up-regulated by UC-MSCs. The dysregulated gene clusters associated with immune-response-related ontologies, namely, lymphocyte proliferation or activation, apoptosis and cell cycle, were further analyzed. CONCLUSIONS: Among the nine canonical pathways identified, three pathways (namely T-helper cell differentiation, cyclins and cell cycle regulation, and gap/tight junction signalling pathways) were highly enriched with these dysregulated genes. The pathways represent putative molecular pathways through which UC-MSCs elicit immunosuppressive activity toward activated T cells. This study provides a global snapshot of gene networks and pathways that contribute to the ability of UC-MSCs to suppress activated T cells.

Isolation and characterization of primary microglia from post-natal murine brain tissues: a comparison of two methods.

Microglia are resident macrophages of the central nervous system (CNS). Apart from playing vital roles as sentinel cells, they are crucial in physiological processes such as synaptic pruning during brain development. CNS disorders require an understanding of the contribution of each cellular compartment to the pathogenesis. Elucidating the role of microglia in disease development and progression in the intricate CNS environment is technically challenging and requires the establishment of reliable, reproducible techniques to isolate and culture microglia. A number of different protocols have been developed for isolation of neonatal microglia and here we compare two widely used methods, namely, mild trypsinization and EasySep® magnetic separation. EasySep® magnetic separation provided higher microglia yield, and flow cytometric evaluation of CD11b and F4/80 markers revealed that EasySep® separation method also produced significantly higher purity compared to mild trypsinization. Microglia isolated using EasySep® separation method were functional, as demonstrated by the generation of nitric oxide, IL-6, TNF-α, and MCP-1 in response to lipopolysaccharide stimulation. In summary, this study has revealed that magnetic separation is superior to mild trypsinization in terms of yield and purity of microglia.

A three-dimensional collagen construct to model lipopolysaccharide-induced activation of BV2 microglia.

BACKGROUND: We report a novel method of culturing microglia in three dimension (3D) using collagen as a substrate. By culturing microglia within a matrix, we aim to emulate the physical state of microglia embedded within parenchyma. METHODS: BV2 microglia cell suspensions were prepared with type I collagen and cast into culture plates. To characterise the BV2 microglia cultured in 3D, the cultures were evaluated for their viability, cell morphology and response to lipopolysaccharide (LPS) activation. Conventional monolayer cultures (grown on uncoated and collagen-coated polystyrene) were set up concurrently for comparison. RESULTS: BV2 microglia in 3D collagen matrices were viable at 48 hrs of culture and exhibit a ramified morphology with multiplanar cytoplasmic projections. Following stimulation with 1 µg/ml LPS, microglia cultured in 3D collagen gels increase their expression of nitric oxide (NO) and CD40, indicating their capacity to become activated within the matrix. Up to 97.8% of BV2 microglia grown in 3D cultures gained CD40 positivity in response to LPS, compared to approximately 60% of cells grown in a monolayer (P<.05). BV2 microglia in 3D collagen gels also showed increased mRNA and protein expression of inflammatory cytokines IL-6, TNF-α and the chemoattractant MCP-1 following LPS stimulation. CONCLUSIONS: In summary, BV2 microglia cultured in 3D collagen hydrogels exhibit multiplanar cytoplasmic projections and undergo a characteristic and robust activation response to LPS. This culture system is accessible to a wide range of analyses and provides a useful new in vitro tool for research into microglial activation.

Immunomodulatory activity of polyphenols derived from Cassia auriculata flowers in aged rats.

The immunomodulatory activity of Cassia auriculata (CA)-derived polyphenols was tested on aged rats. Rats (24-26 months old) were given CA polyphenols supplementation at doses of 25, 50, and 100 mg/kg for 28 days. Flow cytometry analysis of CA polyphenols-treated aged rats showed increased T and B cells percentage along with enhanced proliferation of splenocytes in both resting and LPS-stimulated cells. Increased percentage of pan T cells is further supported by an elevation of CD4+, CD8+, and CD4+CD25+ regulatory cells. In terms of innate immune cell activity, CA polyphenol supplementation reduced the oxidative burst activity of neutrophils in response to PMA and Escherichia coli activation. Our results collectively show that polyphenols derived from CA boost T cell immunity by increasing the number of T cells and its sensitivity towards stimulants and decreasing ROS production by neutrophils that could potentially harm multiple biological systems in aged individuals.

Generation of mesenchymal stem cell from human umbilical cord tissue using a combination enzymatic and mechanical disassociation method.

MSCs (mesenchymal stem cells) promise a great potential for regenerative medicine due to their unique properties of self-renewal, high plasticity, modulation of immune response and the flexibility for genetic modification. Therefore, the increasing demand for cellular therapy necessitates a larger-scale production of MSC; however, the technical and ethical issues had put a halt on it. To date, studies have shown that MSC could be derived from human UC (umbilical cord), which is once considered as clinical waste. We have compared the two conventional methods which are classic enzymatic digestion and explant method with our newly tailored enzymatic-mechanical disassociation method to generate UC-MSC. The generated UC-MSCs from the methods above were characterized based on their immunophenotyping, early embryonic transcription factors expression and mesodermal differentiation ability. Our results show that enzymatic-mechanical disassociation method increase the initial nucleated cell yield greatly (approximately 160-fold) and maximized the successful rate of UC-MSC generation. Enzymatic-mechanical disassociation-derived UC-MSC exhibited fibroblastic morphology and surface markers expression of CD105, CD73, CD29, CD90 and MHC class I. Furthermore, these cells constitutively express early embryonic transcription factors (Nanog, Oct-4, Sox-2 and Rex-1), as confirmed by RT-PCR, indicating their multipotency and high self-renewal capacity. They are also capable of differentiating into osteoblasts and adipocytes when given an appropriate induction. The present study demonstrates a new and efficient approach in generating MSC from UC, hence serving as ideal alternative source of mesenchymal stem cell for clinical and research use.

The immunosuppressive effects of human bone marrow-derived mesenchymal stem cells target T cell proliferation but not its effector function.

Mesenchymal stem cells (MSC) are non-haematopoietic stem cells that are capable of differentiating into tissues of mesodermal origin. MSC play an important role in supporting the development of fetal and adult haematopoiesis. More recently, MSC have also been found to exhibit inhibitory effect on T cell responses. However, there is little information on the mechanism of this immunosuppression and our study addresses this issue by targeting T cell functions at various level of immune responses. We have generated MSC from human adult bone marrow (BM) and investigated their immunoregulatory function at different phases of T cell responses. MSC showed the ability to inhibit mitogen (CD3/CD28 microbeads)-activated T cell proliferation in a dose-dependent manner. In order to evaluate the specificity of this immunosuppression, the proliferation of CD4(+) and CD8(+) cells were measured. MSC equally inhibit CD4(+) and CD8(+) subpopulations of T cells in response to PHA stimulation. However, the antiproliferative effect of MSC is not due to the inhibition of T cell activation. The expression of early activation markers of T cells, namely CD25 and CD69 were not significantly altered by MSC at 24, 48 and 72h. Furthermore, the immunosuppressive effect of MSC mainly targets T cell proliferation rather than their effector function since cytotoxicity of T cells is not affected. This work demonstrates that the immunosuppressive effect of MSC is exclusively a consequence of an anti-proliferative activity, which targets T cells of different subpopulations. For this reason, they have the potential to be exploited in the control of unwanted immune responses such as graft versus host disease (GVHD) and autoimmunity.