Function Of Mesenchymal Stromal Cells Research Articles

Impairment in the Mesenchymal Bone-Marrow Niche of Beta-Thalassemia Patients and Association with Prolonged Iron Exposure

Bone marrow (BM) contains a population of mesenchymal stromal cells (MSC) that, together with endothelial cells and osteoblasts, provide a specific microenvironment to support hematopoietic stem cell homeostasis. Beta-thalassemia (BT) is an hereditary blood disorder characterized by reduced or absent synthesis of hemoglobin beta-chains. Data on the mesenchymal compartment in BT patients are scarce. We isolated and characterized MSCs from BT and healthy donor (HD) BM samples. BT-MSCs showed a reduced clonogenic capacity, delay in colony formation, lower numbers of CFU-Fs and longer population doubling time. Similarly, we observed an altered differentiation capacity into adipocytes and osteoblasts. Both HD- and BT-MSCs express the canonical mesenchymal markers. On the contrary, the expression of CD146 and CD271 was extremely reduced in BT-MSCs, indicating a pauperization of the most primitive stem cell pool. We analyzed the expression of genes involved in the crosstalk between MSCs and HSCs and found a reduced expression of Cxcl12, SCF and Angp1 in BT-MSCs. Several genes relevant for MSC functionality were also downregulated in BT-MSCs. We demonstrated that MSCs are able to uptake and store iron. ROS levels were increased in BT-MSCs possibly due to altered anti-oxidant response and iron overload associated with blood transfusions. Importantly, higher level of ROS and reduced expression of primitive markers were observed in HD-MSCs cultured in presence of iron, underlying the importance of iron level for normal MSC function. In conclusion, we showed an impairment in the mesenchymal niche of BT-BM possibly associated with prolonged iron exposure. DisclosuresMarktel:GSK: Other: B-thalassemia gene therapy was developed by Fondazione Telethon and Ospedale San Raffaele and has been inlicenced by GSK that provides funding for the clinical trial, Research Funding. Ciceri:GSK: Other: B-thalassemia gene therapy was developed by Fondazione Telethon and Ospedale San Raffaele and has been inlicenced by GSK that provides funding for the clinical trial, Research Funding.

Optimized lentiviral transduction of human amniotic mesenchymal stromal cells

Mesenchymal stromal cells are excellent candidates for regenerative medicine since they are multipotent, easy to isolate, can be expanded to obtain clinically relevant numbers and are immunoprivileged. Stable genetic modification with viral vectors can improve mesenchymal stromal cell function and enhance their therapeutic potential. However, standard viral vectors achieve sub-optimal transduction efficiency with a single infection. On the other hand, multiple transduction cycles or antibiotic-based selection methods may alter the stem cell phenotype. We hypothesized that the use of lentiviral vectors containing specific regulatory sequences may result in improved transduction efficiency. Thus, we compared two types of third generation lentiviral vectors, one of which, the pLenti7.3 vector, contains the optimized sequences for Polypurine Tract and Woodchuck Post-transcriptional Regulatory Element. We demonstrated that with the pLenti7.3 it is possible to efficiently transduce human mesenchymal stromal cells with a single transduction cycle. Additionally, we successfully showed that by using the pLenti7.3 vector it is possible to efficiently over-express different growth factors, particularly relevant for cardiac protection and differentiation, in human mesenchymal stromal cells.

Orthogonal potency analysis of mesenchymal stromal cell function during ex vivo expansion

Adult bone marrow mesenchymal stromal cells (MSCs) have cross-functional, intrinsic potency that is of therapeutic interest. Their ability to regenerate bone, fat, and cartilage, modulate the immune system, and nurture the growth and function of other bone marrow hematopoietic stem/progenitor cells have all been evaluated by transplant applications of MSCs. These applications require the isolation and expansion scaled cell production. To investigate biophysical properties of MSCs that can be feasibly utilized as predictors of bioactivity during biomanufacturing, we used a low-density seeding model to drive MSCs into proliferative stress and exhibit the hallmark characteristics of in vitro aging. A low-density seeding method was used to generate MSCs from passages 1–7 to simulate serial expansion of these cells to maximize yield from a single donor. MSCs were subjected to three bioactivity assays in parallel to ascertain whether patterns in MSC age, size, and shape were associated with the outcomes of the potency assays. MSC age was found to be a predictor of adipogenesis, while cell and nuclear shape was strongly associated to hematopoietic-supportive potency. Together, these data evaluate morphological changes associated with cell potency and highlight new strategies for purification or alternatives to assessing MSC quality.

Survivin Is Required for Mouse and Human Bone Marrow Mesenchymal Stromal Cell Function.

Although mesenchymal stromal cells (MSCs) have significant potential in cell-based therapies, little is known about the factors that regulate their functions. While exploring regulatory molecules potentially involved in MSC activities, we found that the endogenous multifunctional factor Survivin is essential for MSC survival, expansion, lineage commitment, and migration. Pharmacological or genetic blockade of Survivin expression in mouse and human bone marrow MSC enhances caspase 3 and 7 expression and reduces proliferation resulting in fewer MSC and clonogenic colony-forming unit-fibroblasts (CFU-F), whereas ectopic Survivin overexpression in MSC results in their expansion. Survivin is also required for the MSC proliferative responses to basic fibroblast growth factor and platelet derived growth factor. In a wound healing model, Survivin inhibition results in suppression of MSC migration to the wound site. In addition, loss of Survivin in MSCs compromises their hematopoiesis-supporting capacity. These results demonstrate that Survivin is a key regulator of mouse and human MSC function, and suggest that targeted modulation of Survivin in MSCs may have clinical utility to enhance MSC recovery and activity following insult or stress. Stem Cells 2018;36:123-129.

Coupling of P2Y receptors to Ca2+ mobilization in mesenchymal stromal cells from the human adipose tissue

The purinergic transduction was examined in mesenchymal stromal cells (MSCs) from the human adipose tissue, and several nucleotides, including ATP, UTP, and ADP, were found to mobilize cytosolic Ca2+. Transcripts for multiple purinoreceptors were detected in MSC preparations, including A1, A2A, A2B, P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y13, P2Y14, P2X2, P2X4, and P2X7. Cellular responses to nucleotides were insignificantly sensitive to bath Ca2+, pointing at a minor contribution of Ca2+ entry, and were suppressed by U73122 and 2-APB, implicating the phosphoinositide cascade in coupling P2Y receptors to Ca2+ release. While individual cells were sensitive to several P2Y agonists, responsiveness to a given nucleotide varied from cell to cell, suggesting that particular MSCs could employ different sets of purinoreceptors. Caged Ca2+ stimulated Ca2+-induced Ca2+ release (CICR) that was mediated largely by IP3 receptors, and resultant Ca2+ transients were similar to nucleotide responses by magnitude and kinetics. A variety of findings hinted at CICR to be a universal mechanism that finalizes Ca2+ signaling initiated by agonists in MSCs. Individual MSCs responded to nucleotides in an all-or-nothing manner. Presumably just CICR provided invariant Ca2+ responses observed in MSCs at different nucleotide concentrations. The effects of isoform specific agonists and antagonists suggested that both P2Y1 and P2Y13 were obligatory for ADP responses, while P2Y4 and P2Y11 served as primary UTP and ATP receptors, respectively. Extracellular NAD+ stimulated Ca2+ signaling in each ATP-responsive MSC by involving P2Y11. The overall data indicate that extracellular nucleotides and NAD+ can serve as autocrine/paracrine factors regulating MSC functions.

Reduced neuroprotective potential of the mesenchymal stromal cell secretome with ex vivo expansion, age and progressive multiple sclerosis

BackgroundClinical trials using ex vivo expansion of autologous mesenchymal stromal cells (MSCs) are in progress for several neurological diseases including multiple sclerosis (MS). Given that environment alters MSC function, we examined whether in vitro expansion, increasing donor age and progressive MS affect the neuroprotective properties of the MSC secretome. MethodsComparative analyses of neuronal survival in the presence of MSC-conditioned medium (MSCcm) isolated from control subjects (C-MSCcm) and those with MS (MS-MSCcm) were performed following (1) trophic factor withdrawal and (2) nitric oxide–induced neurotoxicity. ResultsReduced neuronal survival following trophic factor withdrawal was seen in association with increasing expansion of MSCs in vitro and MSC donor age. Controlling for these factors, there was an independent, negative effect of progressive MS. In nitric oxide neurotoxicity, MSCcm-mediated neuroprotection was reduced when C-MSCcm was isolated from higher-passage MSCs and was negatively associated with increasing MSC passage number and donor age. Furthermore, the neuroprotective effect of MSCcm was lost when MSCs were isolated from patients with MS. DiscussionOur findings have significant implications for MSC-based therapy in neurodegenerative conditions, particularly for autologous MSC therapy in MS. Impaired neuroprotection mediated by the MSC secretome in progressive MS may reflect reduced reparative potential of autologous MSC-based therapy in MS and it is likely that the causes must be addressed before the full potential of MSC-based therapy is realized. Additionally, we anticipate that understanding the mechanisms responsible will contribute new insights into MS pathogenesis and may also be of wider relevance to other neurodegenerative conditions.

Growth factor independence 1 (Gfi1) regulates the AML supporting function of mesenchymal stromal cells

Growth factor independence 1 (Gfi1) regulates the AML supporting function of mesenchymal stromal cells

Biomaterials that promote cell-cell interactions enhance the paracrine function of MSCs.

Mesenchymal stromal cells (MSCs) secrete paracrine factors that play crucial roles during tissue regeneration. Whether this paracrine function is influenced by the properties of biomaterials in general, and those used for cell delivery in particular, largely remains unexplored. Here, we investigated if three-dimensional culture in distinct microenvironments - nanoporous hydrogels (mean pore size ∼5nm) and macroporous scaffolds (mean pore size ∼120μm) - affects the secretion pattern of MSCs, and consequently leads to differential paracrine effects on target progenitor cells such as myoblasts. We report that compared to MSCs encapsulated in hydrogels, scaffold seeded MSCs show an enhanced secretion profile and exert beneficial paracrine effects on various myoblast functions including migration and proliferation. Additionally, we show that the heightened paracrine effects of scaffold seeded cells can in part be attributed to N-cadherin mediated cell-cell interactions during culture. In hydrogels, this physical interaction between cells is prevented by the encapsulating matrix. Functionally blocking N-cadherin negatively affected the secretion profile and paracrine effects of MSCs on myoblasts, with stronger effects observed for scaffold seeded compared to hydrogel encapsulated cells. Together, these findings demonstrate that the therapeutic potency of MSCs can be enhanced by biomaterials that promote cell-cell interactions.

Transient warming events occurring after freezing impairs umbilical cord–derived mesenchymal stromal cells functionality

BackgroundMesenchymal stromal cells (MSCs) have shown promising results for the treatment of refractory acute graft-versus-host disease. While safety of MSC infusion has been demonstrated, the use of cryopreserved MSCs in clinical trials has raised concerns regarding the retention of their functional activity. This has led to the recommendation by experts in the field to use freshly harvested MSCs, even though this approach is much less practical from a logistic point of view. In the present study, we revisited the impact of cryopreservation on MSC functionality and addressed the possibility that warming events on frozen cells rather than cryopreservation per se could impact MSC functionality. MethodsFollowing controlled-rate freezing to −130°C, umbilical cord–derived MSCs were left at room temperature (RT) for 2–10 min or on dry ice for 10 min, before being transferred into liquid nitrogen (LqN2). MSCs of each group were subsequently tested (viability, functionality and cellular damage) and compared with their freshly harvested counterparts. ResultsWe demonstrated that freshly harvested MSCs as well as cryopreserved MSCs that were left on dry ice following step-down freezing have comparable viability, functionality and integrity. In contrast, cryopreserved MSCs that were left at RT before being transferred into LqN2 were functionally impaired and showed cellular damage upon thawing even though they exhibited high viability. DiscussionWarming events after freezing and not cryopreservation per se significantly impair MSC functionality, indicating that cryopreserved MSCs can be an advantageous alternative to freshly harvested cells for therapeutic purposes.

Comparison and immunobiological characterization of retinoic acid inducible gene-I-like receptor expression in mesenchymal stromal cells

Due to their immunomodulatory and regenerative properties, Mesenchymal stromal cells (MSC) have generated major interests in several clinical settings including transplantation and inflammatory diseases. MSC functions can be influenced by their tissue origin. Their microenvironment strongly affects their biology notably through TLR sensing. In this study, we show that MSC isolated from four different sources express another type of cytosolic pathogen recognition receptors known as retinoic acid inducible gene-I (RIG-I)-like receptors (RLR). RLR activation in MSC induces the production of Type I IFN (IFN-β) and Type III IFN (IFN-λ1). The highest producers are adipose tissue(AT)-MSC. We further show that Interferon production is induced through TBK1/IKK-ε signaling and IRF7 phosphorylation. Depending on MSC source, the knockdown of TLR3 and/or RIG-I decreases the MSC response to RLR ligand poly(I:C)/Lyovec. Among the different MSC types, AT-MSCs display the highest sensitivity to viral stimuli as shown by the alteration of their viability after prolonged stimulation. Our work indicates that this could be linked to an increase of pro-apoptotic Noxa expression. Finally, the expression of IDO1 and LIF upon RLR activation indicate the increase of MSC immunomodulatory potential, especially in AT-MSCs. Altogether, these data should be considered when designing MSC-based therapy in clinical settings where inflammation or infection are present.

PGE2 Receptor Subtype 1 (EP1) Regulates Mesenchymal Stromal Cell Osteogenic Differentiation by Modulating Cellular Energy Metabolism.

Mesenchymal stromal cells (MSCs) are multipotent progenitors capable of differentiation into osteoblasts and can potentially serve as a source for cell-based therapies for bone repair. Many factors have been shown to regulate MSC differentiation into the osteogenic lineage such as the Cyclooxygenase-2 (COX2)/Prostaglandin E2 (PGE2) signaling pathway that is critical for bone repair. PGE2 binds four different receptors EP1-4. While most studies focus on the role PGE2 receptors EP2 and EP4 in MSC differentiation, our study focuses on the less studied, receptor subtype 1 (EP1) in MSC function. Recent work from our laboratory showed that EP1-/- mice have enhanced fracture healing, stronger cortical bones, higher trabecular bone volume and increased in vivo bone formation, suggesting that EP1 is a negative regulator of bone formation. In this study, the regulation of MSC osteogenic differentiation by EP1 receptor was investigated using EP1 genetic deletion in EP1-/- mice. The data suggest that EP1 receptor functions to maintain MSCs in an undifferentiated state. Loss of the EP1 receptor changes MSC characteristics and permits stem cells to undergo more rapid osteogenic differentiation. Notably, our studies suggest that EP1 receptor regulates MSC differentiation by modulating MSC bioenergetics, preventing the shift to mitochondrial oxidative phosphorylation by maintaining high Hif1α activity. Loss of EP1 results in inactivation of Hif1α, increased oxygen consumption rate and thus increased osteoblast differentiation. J. Cell. Biochem. 118: 4383-4393, 2017. © 2017 Wiley Periodicals, Inc.

LB33 - Transient warming events occurring after freezing impairs umbilical cord-derived mesenchymal stromal cell functionality

Mesenchymal stromal cells (MSC) have shown promising results for the treatment of refractory acute graft-versus-host-disease and are considered for many other therapeutic applications. While safety of MSC infusion has been demonstrated, the use of cryopreserved MSC in clinical trials has raised concerns about the retention of their functional activity. This has led to the recommendation by several experts in the field to use freshly harvested MSC, even though this approach is much less practical from a logistic point of view. In the present study, we revisited the impact of cryopreservation on MSC and addressed the possibility that warming events on frozen cells rather than cryopreservation per se could impair MSC functionality and affect cell integrity. Following controlled-rate freezing to −130°C, umbilical cord-derived MSC were left at room temperature for 2 to 10 minutes (group 1) or on dry ice for 10 minutes (group 2), before being transferred into liquid nitrogen. MSC of each experimental group were subsequently thawed and tested together with their freshly harvested counterpart. We first determined viability by DAPI staining and found a slight (<10%) albeit significant decrease in post-thaw viability of cells from groups 1 and 2 compared to freshly harvested cells. We next determined the ability of MSC to inhibit the proliferation of CD3/CD28 activated T cells as a measure of their immunosuppressive effect. MSC from group 1 had a dramatically reduced immunosuppressive effect (>75%) while MSC from group 2 were as efficient as their freshly harvested counterpart. IFN-γ-induced IDO expression was also impaired in group 1 MSC. Post-thaw cell integrity was evaluated by adhesion to fibronectin-coated dishes, lactate dehydrogenase release and actin filament staining. Group 1 MSC had a reduced ability to bind to fibronectin and exhibited a higher level of lactate dehydrogenase release compared to MSC from group 2. Defects in actin cytoskeleton were observed in thawed MSC from group 1 but not group 2. We thus conclude that warming events after freezing and not cryopreservation per se significantly impair MSC functionality and induce cellular damage upon thawing indicating that properly cryopreserved MSC can be an advantageous alternative to freshly harvested cells for therapeutic purposes.

Immune dysfunctionality of replicative senescent mesenchymal stromal cells is corrected by IFNγ priming.

Industrial-scale expansion of mesenchymal stromal cells (MSCs) is often used in clinical trials, and the effect of replicative senescence on MSC functionality is of mechanistic interest. Senescent MSCs exhibit cell-cycle arrest, cellular hypertrophy, and express the senescent marker β-galactosidase. Although both fit and senescent MSCs display intact lung-homing properties in vivo, senescent MSCs acquire a significant defect in inhibiting T-cell proliferation and cytokine secretion in vitro. IFNγ does not upregulate HLA-DR on senescent MSCs, whereas its silencing did not reverse fit MSCs' immunosuppressive properties. Secretome analysis of MSC and activated peripheral blood mononuclear cell coculture demonstrate that senescent MSCs are significantly defective in up (vascular endothelial growth factor [VEGF], granulocyte colony-stimulating factor [GCSF], CXCL10, CCL2) or down (IL-1ra, IFNγ, IL-2r, CCL4, tumor necrosis factor-α, IL-5) regulating cytokines/chemokines. Unlike indoleamine 2,3 dioxygenase (IDO), silencing of CXCL9, CXCL10, CXCL11, GCSF, CCL2, and exogenous addition of VEGF, fibroblast growth factor-basic do not modulate MSCs' immunosuppressive properties. Kynurenine levels were downregulated in senescent MSC cocultures compared with fit MSC counterparts, and exogenous addition of kynurenine inhibits T-cell proliferation in the presence of senescent MSCs. IFNγ prelicensing activated several immunomodulatory genes including IDO in fit and senescent MSCs at comparable levels and significantly enhanced senescent MSCs' immunosuppressive effect on T-cell proliferation. Our results define immune functional defects acquired by senescent MSCs, which are reversible by IFNγ prelicensing.

Morphological features of IFN-γ–stimulated mesenchymal stromal cells predict overall immunosuppressive capacity

Human mesenchymal stromal cell (MSC) lines can vary significantly in their functional characteristics, and the effectiveness of MSC-based therapeutics may be realized by finding predictive features associated with MSC function. To identify features associated with immunosuppressive capacity in MSCs, we developed a robust in vitro assay that uses principal-component analysis to integrate multidimensional flow cytometry data into a single measurement of MSC-mediated inhibition of T-cell activation. We used this assay to correlate single-cell morphological data with overall immunosuppressive capacity in a cohort of MSC lines derived from different donors and manufacturing conditions. MSC morphology after IFN-γ stimulation significantly correlated with immunosuppressive capacity and accurately predicted the immunosuppressive capacity of MSC lines in a validation cohort. IFN-γ enhanced the immunosuppressive capacity of all MSC lines, and morphology predicted the magnitude of IFN-γ-enhanced immunosuppressive activity. Together, these data identify MSC morphology as a predictive feature of MSC immunosuppressive function.

Brief Report: Proteasomal Indoleamine 2,3-Dioxygenase Degradation Reduces the Immunosuppressive Potential of Clinical Grade-Mesenchymal Stromal Cells Undergoing Replicative Senescence.

Owing to their immunosuppressive properties, mesenchymal stromal cells (MSCs) obtained from bone marrow (BM-MSCs) or adipose tissue (ASCs) are considered a promising tool for cell therapy. However, important issues should be considered to ensure the reproducible production of efficient and safe clinical-grade MSCs. In particular, high expansion rate, associated with progressive senescence, was recently proposed as one of the parameters that could alter MSC functionality. In this study, we directly address the consequences of replicative senescence on BM-MSC and ASC immunomodulatory properties. We demonstrate that MSCs produced according to GMP procedures inhibit less efficiently T-cell, but not Natural Killer (NK)- and B-cell, proliferation after reaching senescence. Senescence-related loss-of-function is associated with a decreased indoleamine 2,3-dioxygenase (IDO) activity in response to inflammatory stimuli. In particular, although STAT-1-dependent IDO expression is transcriptionally induced at a similar level in senescent and nonsenescent MSCs, IDO protein is specifically degraded by the proteasome in senescent ASCs and BM-MSCs, a process that could be reversed by the MG132 proteasome inhibitor. These data encourage the use of appropriate quality controls focusing on immunosuppressive mechanisms before translating clinical-grade MSCs in the clinic. Stem Cells 2017;35:1431-1436.

A Proinflammatory Secretome Mediates the Impaired Immunopotency of Human Mesenchymal Stromal Cells in Elderly Patients with Atherosclerosis.

Inflammation plays a pivotal role in the initiation and progression of atherosclerosis (ATH). Due to their potent immunomodulatory properties, mesenchymal stromal cells (MSCs) are evaluated as therapeutic tools in ATH and other chronic inflammatory disorders. Aging reduces MSCs immunopotency potentially limiting their therapeutic utility. The mechanisms that mediate the effect of age on MSCs immune‐regulatory function remain elusive and are the focus of this study. Human adipose tissue‐derived MSCs were isolated from patients undergoing coronary artery bypass graft surgery. MSCs:CD4+T‐cell suppression, a readout of MSCs' immunopotency, was assessed in allogeneic coculture systems. MSCs from elderly subjects were found to exhibit a diminished capacity to suppress the proliferation of activated T cells. Soluble factors and, to a lesser extent, direct cell‐cell contact mechanisms mediated the MSCs:T‐cell suppression. Elderly MSCs exhibited a pro‐inflammatory secretome with increased levels of interleukin‐6 (IL‐6), IL‐8/CXCL8, and monocyte chemoattractant protein‐1 (MCP‐1/CCL2). Neutralization of these factors enhanced the immunomodulatory function of elderly MSCs. In summary, our data reveal that in contrast to young MSCs, MSCs from elderly individuals with ATH secrete high levels of IL‐6, IL‐8/CXCL8 and MCP‐1/CCL2 which mediate their reduced immunopotency. Consequently, strategies aimed at targeting pro‐inflammatory cytokines/chemokines produced by MSCs could enhance the efficacy of autologous cell‐based therapies in the elderly. Stem Cells Translational Medicine 2017;6:1132–1140

Abstract TP94: Mesenchymal Stromal Cells Behave Differently When Exposed to Medications Commonly Prescribed to Stroke Patients

Background: As a promising investigational therapy for stroke recovery, mesenchymal stromal cells (MSCs) are in various stages of clinical trials. MSCs may promote recovery through cytokine release and immunomodulation. Stroke patients typically are treated with antiplatelets and medications for hypertension and hyperlipidemia. We explored the effect of commonly prescribed drugs at physiological concentrations on MSCs. Methods: Clinical grade bone marrow MSCs from healthy donor at passage 2 were thawed and re-suspended in serum free media. Monocytes (Mo) were isolated from peripheral blood of healthy humans. MSCs and Mo were cultured alone as well as in co-culture and exposed to simvastatin, atenolol, losartan, captopril, or aspirin. They were also exposed to high glucose (upto 40mM) to simulate hyperglycemia. At 24 hours of incubation, media was collected and TNF-α concentration was measured, as an index of immunomodulation of Mo by MSCs. Cell viability was also measured (using MTT assay and flow cytometry). Results: There were significant effects of all drugs on viability of MSCs but with no impact on Mo. More importantly, Losartan (dose independent), Simvastatin and Atenolol (dose-dependent) reduced the viability of MSCs even at the pharmacologically relevant concentrations (Fig 1). High glucose had no effect on viability of MSCs or Mo. TNF-α secretion from co-culture of MSCs and Mo at 24 hours showed differences at very high doses of aspirin (2-fold increase), atenolol (0.5 fold decrease), and glucose (0.5 fold decrease) (data not shown). However, these high concentrations are unlikely to be achieved pharmacologically in plasma of patients treated with these drugs. Conclusion: Exposure of MSCs to clinically relevant drugs can alter their viability and function. Our results suggest that stroke trials involving use of intravenous MSCs should consider the differential impact of commonly prescribed medications on MSCs function.

Mesenchymal stromal cell therapy to promote cardiac tissue regeneration and repair.

This review focuses on articles published from January 2015 to June 2016 on mesenchymal stromal cell (MSC) therapy for cardiac regeneration and repair. During this period, reports published on MSCs address the best MSC tissue source for cellular therapy, mechanisms of MSC activity and improving MSC longevity, and homing in vivo. Currently, there is no definitive therapeutic advantage of any one tissue-derived MSC over another, and even combination therapies struggle with conflicting outcomes. MSC activity, persistence in vivo, or homing can be improved by priming strategies, genetic modification, or biomaterials. Despite numerous studies showing improvement in heart function after acute cardiac injury, the reproducibility and efficacy of the therapy remains elusive and falls short of expectations in clinical trials. Although the safety of MSCs is undisputed, the success of MSC preparations in improving cardiac function clinically remains uncertain due to challenges in correlating MSC potency with clinical outcomes, donor-related variation in MSC function, and a profusion of culture methodologies. Several strategies are available to advance MSC cell therapy for acute cardiac injury to promote cardiac regeneration and repair in rigorous preclinical and clinical studies.

De novo AML exhibits greater microenvironment dysregulation compared to AML with myelodysplasia-related changes

The interaction between the bone marrow microenvironment and malignant hematopoietic cells can result in the protection of leukemia cells from chemotherapy in both myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). We, herein, characterized the changes in cytokine expression and the function of mesenchymal stromal cells (MSC) in patients with MDS, AML with myelodysplasia-related changes (MRC), a well-recognized clinical subtype of secondary AML, and de novo AML. We observed a significant inhibitory effect of MDS-MSC on T lymphocyte proliferation and no significant differences in any of the cytokines tested. AML-MSC inhibited T-cell proliferation only at a very low MSC/T cell ratio. When compared to the control, AML-MRCderived MSC presented a significant increase in IL6 expression, whereas de novo AML MSC presented a significant increase in the expression levels of VEGFA, CXCL12, RPGE2, IDO, IL1β, IL6 and IL32, followed by a decrease in IL10 expression. Furthermore, data indicate that IL-32 regulates stromal cell proliferation, has a chemotactic potential and participates in stromal cell crosstalk with leukemia cells, which could result in chemoresistance. Our results suggest that the differences between AML-MRC and de novo AML also extend into the leukemic stem cell niche and that IL-32 can participate in the regulation of the bone marrow cytokine milieu.

Mesenchymal Stromal Cells and Toll-Like Receptor Priming: A Critical Review.

Mesenchymal Stromal Cells (MSCs) are potential cellular candidates for several immunotherapy purposes. Their multilineage potential and immunomodulatory properties make them interesting tools for the treatment of various immunological diseases. However, depending on the local microenvironment, diverse biological functions of MSCs can be modulated. Indeed, during infections such as obtained following TLR-agonist engagement (called as TLR priming), the phenotype, multilineage potential, hematopoietic support and immunomodulatory capacity of MSCs can present critical changes, which could further affect their therapeutic potential. Thus, for appropriate clinical application of MSCs, it is important to well know and understand these effects in particular during infectious episodes and to find the suitable experimental settings to study that. Pre-stimulation of MSCs with a specific TLR ligand may serve as an effective priming step to modulate one of its function to achieve a desired therapeutic issue.