A comparison of clinically relevant sources of mesenchymal stem cell-derived exosomes: Bone marrow and amniotic fluid.

BACKGROUND/PURPOSE: Exosomes may constitute a more practical alternative to live cells in select stem cell-based therapies. We sought to compare exosomes from two mesenchymal stem cell (MSC) sources relevant to perinatal and pediatric diseases. METHODS: Exosomes were isolated by reagent-enhanced centrifugation from cell culture media of banked human bone marrow (bm) and amniotic fluid (af) MSCs after serum starvation. Characterization was by flow exometry for tetraspanin markers CD9, CD63, and CD81, transmission electron microscopy for size and morphology, and tunable resistive pulse sensing for size distribution and concentration. Statistical comparisons of count data were made by Poisson regression modeling and Student's T-test. RESULTS: Exosomes of appropriate size and morphology were isolated with comparable expressions of CD9 (96% vs. 94%), CD63 (88% vs. 66%), and CD81 (71% vs. 63%) for bmMSC and afMSC, respectively. Total exosome yield (particles/mL) adjusted for number of cells was higher from afMSCs than bmMSCs by an estimated 25% (P < 0.001). CONCLUSIONS: While bone marrow and amniotic fluid mesenchymal stem cells are comparable sources of exosomes in size distribution, morphology, and expression of typical surface markers, yield may be higher from amniotic fluid cells. The amniotic fluid appears to be a preferable source of exosomes for clinical applications. LEVEL OF EVIDENCE: N/A (bench laboratory study).

Red Blood Cells: A Source of Extracellular Vesicles.

During their lifetime, like all other cell types, red blood cells (RBCs) release both exosomes and plasma membrane derived EVs (ectosomes). RBC exosomes are formed only during the development of RBCs in bone marrow, and are released following the fusion of microvesicular bodies (MVB) with the plasma membrane. On the other hand, RBC EVs are generated during normal aging of RBCs in circulation by budding of the plasma membrane due to complement -mediated calcium influx, followed by vesicle shedding. This makes red blood cells and stored red cells a reliable source of EVs for basic and clinical research.

Characterization of Extracellular Vesicles by Flow Cytometry.

Here, we describe a comprehensive methodology for the setup and standardization of EV analysis using nanoscale flow cytometry. Controls of different size ranges, fluorescent intensities, and materials can be used to set up distribution curves that are then used for instrument optimization and as a reference guide. Using these controls, flow cytometry instruments can be primed for the detection, analysis, and sorting of specific EV populations. This allows for cross platform comparison and the ability to monitor both quality control (QC) and quality assurance (QA). The method here describes the use of nanoparticles to optimize a flow cytometer for small particle detection. It also outlines the procedures necessary to recover EVs for downstream applications.

NAD+ protects against EAE by regulating CD4+ T-cell differentiation.

CD4(+) T cells are involved in the development of autoimmunity, including multiple sclerosis (MS). Here we show that nicotinamide adenine dinucleotide (NAD(+)) blocks experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, by inducing immune homeostasis through CD4(+)IFNγ(+)IL-10(+) T cells and reverses disease progression by restoring tissue integrity via remyelination and neuroregeneration. We show that NAD(+) regulates CD4(+) T-cell differentiation through tryptophan hydroxylase-1 (Tph1), independently of well-established transcription factors. In the presence of NAD(+), the frequency of T-bet(-/-) CD4(+)IFNγ(+) T cells was twofold higher than wild-type CD4(+) T cells cultured in conventional T helper 1 polarizing conditions. Our findings unravel a new pathway orchestrating CD4(+) T-cell differentiation and demonstrate that NAD(+) may serve as a powerful therapeutic agent for the treatment of autoimmune and other diseases.

Role of endothelial progenitor cells and inflammatory cytokines in healing of diabetic foot ulcers.

BACKGROUND: To evaluate changes in endothelial progenitor cells (EPCs) and cytokines in patients with diabetic foot ulceration (DFU) in association with wound healing. METHODS: We studied healthy subjects, diabetic patients not at risk of DFU, at risk of DFU and with active DFU. We prospectively followed the DFU patients over a 12-week period. We also investigated similar changes in diabetic rabbit and mouse models of wound healing. RESULTS: All EPC phenotypes except the kinase insert domain receptor (KDR)(+)CD133(+) were reduced in the at risk and the DFU groups compared to the controls. There were no major EPC differences between the control and not at risk group, and between the at risk and DFU groups. Serum stromal-cell derived factor-1 (SDF-1) and stem cell factor (SCF) were increased in DFU patients. DFU patients who healed their ulcers had lower CD34(+)KDR(+) count at visits 3 and 4, serum c-reactive protein (CRP) and granulocyte-macrophage colony-stimulating factor (GM-CSF) at visit 1, interleukin-1 (IL-1) at visits 1 and 4. EPCs tended to be higher in both diabetic animal models when compared to their non-diabetic counterparts both before and ten days after wounding. CONCLUSIONS: Uncomplicated diabetes does not affect EPCs. EPCs are reduced in patients at risk or with DFU while complete wound healing is associated with CD34(+)KDR(+) reduction, suggesting possible increased homing. Low baseline CRP, IL-1α and GM-CSF serum levels were associated with complete wound healing and may potentially serve as prognostic markers of DFU healing. No animal model alone is representative of the human condition, indicating the need for multiple experimental models.