A Novel Immunomodulatory Mechanism Dependent on Acetylcholine Secreted by Human Bone Marrow-derived Mesenchymal Stem Cells

Circulating extracellular choline acetyltransferase regulates inflammation

BACKGROUND

Choline acetyltransferase (ChAT) is required for the biosynthesis of acetylcholine, the molecular mediator that inhibits cytokine production in the cholinergic anti-inflammatory pathway of the vagus nerve inflammatory reflex. Abundant work has established the biology of cytoplasmic ChAT in neurons, but much less is known about the potential presence and function of ChAT in the extracellular milieu.

OBJECTIVES

We evaluated the hypothesis that extracellular ChAT activity responds to inflammation and serves to inhibit cytokine release and attenuate inflammation.

METHODS

After developing novel methods for quantification of ChAT activity in plasma, we determined whether ChAT activity changes in response to inflammatory challenges.

RESULTS

Active ChAT circulates within the plasma compartment of mice and responds to immunological perturbations. Following the administration of bacterial endotoxin, plasma ChAT activity increases for 12-48 h, a time period that coincides with declining tumor necrosis factor (TNF) levels. Further, a direct activation of the cholinergic anti-inflammatory pathway by vagus nerve stimulation significantly increases plasma ChAT activity, whereas the administration of bioactive recombinant ChAT (r-ChAT) inhibits endotoxin-stimulated TNF production and anti-ChAT antibodies exacerbate endotoxin-induced TNF levels, results of which suggest that ChAT activity regulates endogenous TNF production. Administration of r-ChAT significantly attenuates pro-inflammatory cytokine production and disease activity in the dextran sodium sulfate preclinical model of inflammatory bowel disease. Finally, plasma ChAT levels are also elevated in humans with sepsis, with the highest levels observed in a patient who succumbed to infection.

CONCLUSION

As a group, these results support further investigation of ChAT as a counter-regulator of inflammation and potential therapeutic agent.

Immunomodulatory potential of human clonal mesenchymal stem cells and their extracellular vesicle subpopulations in an inflammatory-mediated diabetic Rhesus monkey model

AIMS

This study aimed to investigate the therapeutic potential of a homogenous clonal population of mesenchymal stem cells (cMSC) and their extracellular vesicles (cMSC-EV) subpopulations on isolated rat islets in vitro and in inflammatory-mediated type 1 diabetes (T1D) non-human primate models.

MAIN METHODS

EV subpopulations were isolated from human bone marrow-derived cMSC supernatant by low- and high-speed ultracentrifuge (EV-20K and EV-U110K) and sucrose density gradient (EV-S110K). The EVs were characterized generally and for the level of albumin, acetylcholinesterase (AChE) activity, co-isolate apoptotic markers, and expression of CD63+/annexin V+. Rat islet-derived single cells (iSCs) proliferation was measured using a Ki-67 proliferation assay. Diabetes was induced by multiple low-dose administrations of streptozotocin in rhesus monkeys. The diabetic monkeys were divided into three groups: the cMSC group, received two injections of 1.5 × 106 cMSC/kg body weight; the EV group received two injections of EVs isolated from 1.5 × 106 cMSC/kg, and the vehicle group received phosphate-buffered saline.

KEY FINDINGS

EV-S110K showed higher AChE activity, lower expression of CD63+/annexin V+, and lower apoptotic co-isolates. EV-S110K induced β-cell proliferation in vitro in a dose-dependent manner. The administration of EV-S110K and/or cMSC in diabetic monkeys demonstrated no significant changes in general diabetic indices and β-cell mass in the pancreas of the monkeys. Both treatments demonstrated a lowering trend in blood glucose levels and reduced pro-inflammatory cytokines. In contrast, regulatory T cells and anti-inflammatory cytokines were increased.

SIGNIFICANCE

cMSC and cMSC-EV provided initial evidence to attenuate clinical symptoms in inflammatory-mediated T1D non-human primates through immunomodulation.

Cell-based therapies for neurological disorders - the bioreactor hypothesis

Cell-based therapies are an emerging biopharmaceutical paradigm under investigation for the treatment of a range of neurological disorders. Accumulating evidence is demonstrating that cell-based therapies might be effective, but the mechanism of action remains unclear. In this Review, we synthesize results from over 20 years of animal studies that illustrate how transdifferentiation, cell replacement and restoration of damaged tissues in the CNS are highly unlikely mechanisms. We consider the evidence for an alternative model that we refer to as the bioreactor hypothesis, in which exogenous cells migrate to peripheral organs and modulate and reprogramme host immune cells to generate an anti-inflammatory, regenerative environment. The results of clinical trials clearly demonstrate a role for immunomodulation in the effects of cell-based therapies. Greater understanding of these mechanisms could facilitate the optimization of cell-based therapies for a variety of neurological disorders.

MicroRNA-126 promotes proliferation, migration, invasion and endothelial differentiation while inhibits apoptosis and osteogenic differentiation of bone marrow-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (BMSCs) are widely used for the treatment of inflammatory and immune diseases, and microRNA-126 (miR-126) is a critical regulator in inflammation as well as immunity. However, the mediating role of miR-126 in BMSCs is still not clear. Thus, this study aimed to preliminarily investigate the effect of miR-126 on proliferation, apoptosis, migration, invasion, differentiation, and its potential regulating pathways in BMSCs. Human BMSCs were obtained and infected with miR-126 overexpression lentivirus, control overexpression lentivirus, miR-126 knock-down lentivirus and control knock-down lentivirus, then cell functions, the PI3 K/AKT pathway and MEK1/ERK1 pathway were evaluated. Subsequently, PI3 K overexpression plasmid and MEK1 overexpression plasmid were transfected into BMSCs with miR-126 knockdown, then the cell functions were assessed as well. BMSCs with miR-126 overexpression displayed elevated proliferation, migration and invasion while decreased apoptosis; however, BMSCs with miR-126 knockdown presented with decreased proliferation, migration, invasion but increased apoptosis. As for differentiation, BMSCs with miR-126 overexpression showed higher levels of CD31, eNOS and VE-cadherin but lower expressions of ALP, OPN and RUNX2, while BMSCs with miR-126 knockdown disclosed the opposite results. Additionally, BMSCs with miR-126 overexpression showed elevated PI3 K, pAKT, MEK1 and pERK1 expressions, while BMSCs with miR-126 knockdown displayed opposite results. Furthermore, PI3 K overexpression and MEK1 overexpression both reversed the effects of miR-126 on cell functions in BMSCs. In conclusion, miR-126 is a genetic regulator in BMSCs via modulating multiple cell functions through the PI3 K/AKT and MEK1/ERK1 signaling pathways.

Perivascular Stem Cells Suppress Inflammasome Activation during Inflammatory Responses in Macrophages

Background and Objectives

Perivascular stem cells (PVCs) have been identified as precursors of mesenchymal stem cells (MSCs) that offer promising prospects for application in the development of cellular therapies. Although PVCs have been demonstrated to have greater therapeutic potential compared to bone marrow and adipose tissue-derived MSCs in various diseases, the regulatory role of PVCs on inflammasome activation during macrophage-mediated inflammatory responses has not been investigated.

Methods and Results

In this study, we found that the PVC secretome effectively alleviates secretion of both caspase-1 and interleukin-1β in lipopolysaccharide-primed and activated human and murine macrophages by blocking inflammasome activation and attenuating the production of mitochondrial reactive oxygen species (ROS). We further showed that the PVC secretome significantly reduces inflammatory responses and endoplasmic reticulum stress in peritoneal macrophages in a mouse model of monosodium urate-induced peritonitis. A cytokine antibody array analysis revealed that the PVC secretome contains high levels of serpin E1 and angiogenin, which may be responsible for the inhibitory effects on mitochondrial ROS generation as well as on inflammasome activation.

Conclusions

Our results suggest that PVCs may be therapeutically useful for the treatment of macrophage- and inflammation-mediated diseases by paracrine action via the secretion of various biological factors.