Comparison of cellular functionality of human mesenchymal stromal cells and PBMC

Integrative Single-Cell RNA-Seq and ATAC-Seq Analysis of Peripheral Mononuclear Cells in Patients With Ankylosing Spondylitis

Objective

Genetic studies on ankylosing spondylitis (AS) have identified more than 100 pathogenic genes. Building a bridge between these genes and biologically targeted therapies is the current research hotspot.

Methods

We integrated single-cell assaying transposase-accessible chromatin sequencing (scATAC-seq) and single-cell RNA sequencing (scRNA-seq) to explore the key genes and related mechanisms associated with AS pathogenesis.

Results

We identified 18 cell types in peripheral mononuclear cells from patients with AS and normal controls and summarized the cell-type-specific abnormal genes by scRNA-seq. Interestingly, we found that the pathogenic gene NFKB involved in AS progression originated from CD8+ T cells. Moreover, we observed an abnormal tumor TNF pathway mediated by abnormal expression of TNF, NFKB, FOS, JUN, and JUNB, and scATAC-seq results confirmed the abnormal accessible binding sites of transcriptional factors FOS, JUN, and JUNB. The final magnetic bead sorting and quantitative real-time PCR(RT-qPCR) confirmed that NFKB, FOS, JUN, and JUNB in CD8+ T cells differed in the AS group.

Conclusions

Our results revealed a possible mechanism by which NFKB abnormally regulates FOS, JUN, and JUNB and drives AS progression, providing a novel perspective from a single cell point of view in AS.

Macrophage interactions with polylactic acid and chitosan scaffolds lead to improved recruitment of human mesenchymal stem/stromal cells: a comprehensive study with different immune cells

Despite the importance of immune cell-biomaterial interactions for the regenerative outcome, few studies have investigated how distinct three-dimensional biomaterials modulate the immune cell-mediated mesenchymal stem/stromal cells (MSC) recruitment and function. Thus, this work compares the response of varied primary human immune cell populations triggered by different model scaffolds and describes its functional consequence on recruitment and motility of bone marrow MSC. It was found that polylactic acid (PLA) and chitosan scaffolds lead to an increase in the metabolic activity of macrophages but not of peripheral blood mononuclear cells (PBMC), natural killer (NK) cells or monocytes. PBMC and NK cells increase their cell number in PLA scaffolds and express a secretion profile that does not promote MSC recruitment. Importantly, chitosan increases IL-8, MIP-1, MCP-1 and RANTES secretion by macrophages while PLA stimulates IL-6, IL-8 and MCP-1 production, all chemokines that can lead to MSC recruitment. This secretion profile of macrophages in contact with biomaterials correlates with the highest MSC invasion. Furthermore, macrophages enhance stem cell motility within chitosan scaffolds by 44% but not in PLA scaffolds. Thus, macrophages are the cells that in contact with engineered biomaterials become activated to secrete bioactive molecules that stimulate MSC recruitment.

TNFα and IL-1β influence the differentiation and migration of murine MSCs independently of the NF-κB pathway

INTRODUCTION

Mesenchymal stem cells (MSCs) have the ability to repair and regenerate tissue, home to sites of inflammation, and evade the host immune system. As such, they represent an attractive therapy for the treatment of autoimmune inflammatory diseases. However, results from in vivo murine studies in inflammatory arthritis have been conflicting, and this may be due to the genetic background of the MSCs used. It is known that the inflammatory milieu may influence properties of MSCs and that, in the case of human bone marrow-derived MSCs, this may be mediated by the nuclear factor-kappa-B (NF-κB) pathway. We sought to determine whether pro-inflammatory cytokines altered the differentiation and migration capacity of murine MSCs from different mouse strains and whether this was mediated by NF-κB.

METHODS

The differentiation and migration of FVB and BALB/c MSCs were carried out in the presence of varying concentrations of tumor necrosis factor-alpha (TNFα) and interleukin (IL)-1β, and the NF-κB pathway was inhibited in one of two ways: either by transduction of MSCs with an adenoviral vector expressing a super-repressor of NF-κB or by the addition of curcumin to culture media.

RESULTS

Both BALB/c and FVB MSCs were sensitive to the effect of pro-inflammatory cytokines in vitro. TNFα and IL-1β suppressed BALB/c osteogenesis and adipogenesis and FVB osteogenesis. The migration of both cell types toward media containing fetal bovine serum was augmented by pre-stimulation with either cytokine. In neither cell type were the cytokine effects reversed by abrogation of the NF-κB pathway.

CONCLUSIONS

These data show that murine MSCs from different genetic backgrounds may be influenced by an inflammatory milieu in a manner that is not mediated by NF-κB, as is the case for human MSCs. This is not mediated by NF-κB. These findings are important and should influence how in vivo trials of murine MSCs are interpreted and the future development of pre-clinical studies in inflammatory diseases.

Early intra-articular complement activation in ankle fractures

Cytokine regulation possibly influences long term outcome following ankle fractures, but little is known about synovial fracture biochemistry. Eight patients with an ankle dislocation fracture were included in a prospective case series and matched with patients suffering from grade 2 osteochondritis dissecans (OCD) of the ankle. All fractures needed external fixation during which joint effusions were collected. Fluid analysis was done by ELISA measuring aggrecan, bFGF, IL-1β, IGF-1, and the complement components C3a, C5a, and C5b-9. The time periods between occurrence of fracture and collection of effusion were only significantly associated with synovial aggrecan and C5b-9 levels (P < 0.001). Furthermore, synovial expressions of both proteins correlated with each other (P < 0.001). Although IL-1β expression was relatively low, intra-articular levels correlated with C5a (P < 0.01) and serological C-reactive protein concentrations 2 days after surgery (P < 0.05). Joint effusions were initially dominated by neutrophils, but the portion of monocytes constantly increased reaching 50% at day 6 after fracture (P < 0.02). Whereas aggrecan and IL-1β concentrations were not different in fracture and OCD patients, bFGF, IGF-1, and all complement components were significantly higher concentrated in ankle joints with fractures (P < 0.01). Complement activation and inflammatory cell infiltration characterize the joint biology following acute ankle fractures.

Gene expression profiles of human adipose tissue-derived mesenchymal stem cells are modified by cell culture density

Previous studies conducted cell expansion ex vivo using low initial plating densities for optimal expansion and subsequent differentiation of mesenchymal stem cells (MSCs). However, MSC populations are heterogeneous and culture conditions can affect the characteristics of MSCs. In this study, differences in gene expression profiles of adipose tissue (AT)-derived MSCs were examined after harvesting cells cultured at different densities. AT-MSCs from three different donors were plated at a density of 200 or 5,000 cells/cm². After 7 days in culture, detailed gene expression profiles were investigated using a DNA chip microarray, and subsequently validated using a reverse transcription polymerase chain reaction (RT-PCR) analysis. Gene expression profiles were influenced primarily by the level of cell confluence at harvest. In MSCs harvested at ∼90% confluence, 177 genes were up-regulated and 102 genes down-regulated relative to cells harvested at ∼50% confluence (P<0.05, FC>2). Proliferation-related genes were highly expressed in MSCs harvested at low density, while genes that were highly expressed in MSCs harvested at high density (∼90% confluent) were linked to immunity and defense, cell communication, signal transduction and cell motility. Several cytokine, chemokine and growth factor genes involved in immunosuppression, migration, and reconstitution of damaged tissues were up-regulated in MSCs harvested at high density compared with MSCs harvested at low density. These results imply that cell density at harvest is a critical factor for modulating the specific gene-expression patterns of heterogeneous MSCs.

Encapsulation of factor IX-engineered mesenchymal stem cells in fibrinogen-alginate microcapsules enhances their viability and transgene secretion

Cell microencapsulation holds significant promise as a strategy for cellular therapies; however, inadequate survival and functionality of the enclosed cells limit its application in hemophilia treatment. Here, we evaluated the use of alginate-based microcapsules to enhance the viability and transgene secretion of human cord blood–derived mesenchymal stem cells in three-dimensional cultures. Given the positive effects of extracellular matrix molecules on mesenchymal stem cell growth, we tested whether fibrinogen-supplemented alginate microcapsules can improve the efficiency of encapsulated factor IX–engineered mesenchymal stem cells as a treatment of hemophilia B. We found that fibrinogen-supplemented alginate microcapsules (a) significantly enhanced the viability and proliferation of factor IX–engineered mesenchymal stem cells and (b) increased factor IX secretion by mesenchymal stem cells compared to mesenchymal stem cells in nonsupplemented microcapsules. Moreover, we observed the osteogenic, but not chondrogenic or adipogenic, differentiation capability of factor IX–engineered cord blood mesenchymal stem cells and their efficient factor IX secretion while encapsulated in fibrinogen-supplemented alginate microcapsules. Thus, the use of engineered mesenchymal stem cells encapsulated in fibrinogen-modified microcapsules may have potential application in the treatment of hemophilia or other protein deficiency diseases.

Extracellular GC-rich DNA activates TLR9- and NF-kB-dependent signaling pathways in human adipose-derived mesenchymal stem cells (haMSCs)

INTRODUCTION

The content of GC-rich ribosomal repeats (rDNA) in cell-free DNA (cfDNA) of patients with various diseases is several times higher as compared with genomic DNA (gDNA) and cfDNA of healthy donors. rDNA may act as Toll-like receptor 9 (TLR9) ligands and affect human adipose-derived mesenchymal stem cells (haMSCs). Here we explore effects of human cfDNAs and model rDNA fragments on cultured haMSCs.

AREAS COVERED

Both cfDNAs and cloned rDNA stimulate expression of TLR9 (qRT-PCR). Treatment with cloned rDNA leads to an increase in the number of TLR9(+) cells (FACS), expression levels for both TLR9 and Myd88, the translocation of nuclear factor-kappa B to the nuclei and up-regulation of TNFα and IL-10 cytokines (ELISA). As shown by an analysis of γH2AX-foci and MTT test, the preconditioning of haMSCs with cloned rDNA fragment increases the resistance of these cells to irradiation at 2Gy, while the treatments with control gDNA did not stimulate either TLR9- or NF-kB-dependent signaling pathways.

EXPERT OPINION

GC-rich sequences present in cfDNA stimulate endogenous stems cells when body is exposed to adverse conditions. GC-rich fragments of human DNA may be used for preconditioning of therapeutic MSCs aiming at an increase in their survival in the ailing body.

Mesenchymal stem cells secrete multiple cytokines that promote angiogenesis and have contrasting effects on chemotaxis and apoptosis

We have previously shown that mesenchymal stem cells (MSC) improve function upon integration in ischemic myocardium. We examined whether specific cytokines and growth factors produced by MSCs are able to affect angiogenesis, cellular migration and apoptosis. Conditioned media (CM) was prepared by culturing MSC for 48 hours. CM displayed significantly elevated levels of VEGF, Monocyte Chemoattractant Protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), MIP-1β and monokine induced by IFN-γ (MIG) compared to control media. MSC contained RNA for these factors as detected by RT-PCR. CM was able to induce angiogenesis in canine vascular endothelial cells. MCP-1 and MIP-1α increased cell migration of MSC while VEGF reduced it. H9c2 cells treated with CM under hypoxic conditions for 24 hours displayed a 16% reduction in caspase-3 activity compared to controls. PI 3-kinase γ inhibitor had no effect on controls but reversed the effect of CM on caspase-3 activity. MCP-1 alone mimicked the protective effect of CM while the PI 3-Kγ inhibitor did not reverse the effect of MCP-1. CM reduced phospho-BAD (Ser112) and phospho-Akt (Ser473) while increasing phospho-Akt (Thr308). MCP-1 reduced the level of phospho-Akt (Ser473) while having no effect on the other two; the PI 3-Kγ inhibitor did not alter the MCP-1 effect. ERK 1/2 phosphorylation was reduced in CM treated H9c2 cells, and inhibition of ERK 1/2 reduced the phosphorylation of Akt (Ser473), Akt (Thr308) and Bad (Ser112). In conclusion, MSC synthesize and secrete multiple paracrine factors that are able to affect MSC migration, promote angiogenesis and reduce apoptosis. While both MCP-1 and PI3-kinase are involved in the protective effect, they are independent of each other. It is likely that multiple pro-survival factors in addition to MCP-1 are secreted by MSC which act on divergent intracellular signaling pathways.

Does complement play a role in bone development and regeneration?

The skeletal and the immune system are not two independent systems, rather, there are multifaceted and complex interactions between the different cell types of both systems and there are several shared cytokines. As a part of the innate immunity, the complement system was found to be an important link between bone and immunity. Complement proteins appear to be involved in bone development and homeostasis, and specifically influence osteoblast and osteoclast activity. This review describes the complex mutual regulation of the two systems, and indicates some of the negative side effects as a result of inappropriate or excessive complement activation.

The anaphylatoxin receptor C5aR is present during fracture healing in rats and mediates osteoblast migration in vitro

BACKGROUND

There is evidence that complement components regulate cytokine production in osteoblastic cells, induce cell migration in mesenchymal stem cells, and play a regulatory role in normal enchondral bone formation. We proved the hypothesis that complement might be involved in bone healing after fracture.

METHODS

We investigated the expression of the key anaphylatoxin receptor C5aR during fracture healing in rats by immunostaining after 1, 3, 7, 14, and 28 days. C5aR expression was additionally analyzed in human mesenchymal stem cells (hMSC) during osteogenic differentiation, in human primary osteoblasts, and osteoclasts by reverse transcriptase polymerase chain reaction and immunostaining. Receptor functionality was proven by the migratory response of cells to C5a in a Boyden chamber.

RESULTS

C5aR was expressed in a distinct spatial and temporal pattern in the fracture callus by differentiated osteoblast, chondroblast-like cells in cartilaginous regions, and osteoclasts. In vitro C5aR was expressed by osteoblasts, osteoclasts, and hMSC undergoing osteogenic differentiation. C5aR was barely expressed by undifferentiated hMSC but was significantly induced after osteogenic differentiation. C5aR activation by C5a induced strong chemotactic activity in osteoblasts, and in hMSC, which had undergone osteogenic differentiation, being abolished by a specific C5aR antagonist. In hMSC, C5a induced less migration reflecting their low level of C5aR expression.

CONCLUSIONS

Our in vitro and in vivo results demonstrated the presence of C5aR in bone forming osteoblasts and bone resorbing osteoclasts. It is suggested that C5aR might play a regulatory role in fracture healing in intramembranous and in enchondral ossification, one possible function being the regulation of cell recruitment.

Cell type-specific responses of peripheral blood mononuclear cells to silver nanoparticles

Silver nanoparticles (Ag-NP) are increasingly used in biomedical applications because of their remarkable antimicrobial activity. In biomedicine, Ag-NP are coated onto or embedded in wound dressings, surgical instruments and bone substitute biomaterials, such as silver-containing calcium phosphate cements. Free Ag-NP and silver ions are released from these coatings or after the degradation of a biomaterial, and may come into close contact with blood cells. Despite the widespread use of Ag-NP as an antimicrobial agent, there is a serious lack of information on the biological effects of Ag-NP on human blood cells. In this study, the uptake of Ag-NP by peripheral monocytes and lymphocytes (T-cells) was analyzed, and the influence of nanosilver on cell biological functions (proliferation, the expression of adhesion molecules, cytokine release and the generation of reactive oxygen species) was studied. After cell culture in the presence of monodispersed Ag-NP (5-30μgml(-1) silver concentration), agglomerates of nanoparticles were detected within monocytes (CD14+) but not in T-cells (CD3+) by light microscopy, flow cytometry and combined focused ion beam/scanning electron microscopy. The uptake rate of nanoparticles was concentration dependent, and the silver agglomerates were typically found in the cytoplasm. Furthermore, a concentration-dependent activation (e.g. an increased expression of adhesion molecule CD54) of monocytes at Ag-NP concentrations of 10-15μgml(-1) was observed, and cytotoxicity of Ag-NP-treated monocytes was observed at Ag-NP levels of 25μgml(-1) and higher. However, no modulation of T-cell proliferation was observed in the presence of Ag-NP. Taken together, our results provide the first evidence for a cell-type-specific uptake of Ag-NP by peripheral blood mononuclear cells (PBMC) and the resultant cellular responses after exposure.

Microenvironmental considerations in the application of human mesenchymal stem cells in regenerative therapies

The therapeutic utilization of stem cells has been ongoing for several decades, principally in the form of bone marrow (BM) transplants to treat various hematological disorders and other immune-related diseases. More recently, stem cells have been examined as a potential therapy for a multitude of other diseases and disorders, many of which are currently untreatable. One consideration that poses a formidable task for the successful clinical application of stem cells in new disease models is the impact of the host tissue microenvironment on the desired therapeutic outcome. In vitro, stem cells exist in surroundings directly controllable by the researcher to produce the desired cellular behavior. In vivo, the transplanted cells are exposed to a dynamic host microenvironment laden with soluble mediators and immunoreactive cells. In this review, we focus on the possible contribution by microenvironmental factors, and how these influences can be overcome in therapies utilizing mesenchymal stem cells (MSCs), such as for graft versus host disease, multiple sclerosis and ischemia among others. Specifically, we examine three ubiquitous microenvironmental factors, IL-1alpha/beta(,) TNFalpha, and SDF-1alpha, and consider how inhibitors and receptor antagonists to these molecules could be applied to increase the efficacy of MSC therapies while minimizing unforeseen harm to the patient.

Advanced glycation end products induce chemokine/cytokine production via activation of p38 pathway and inhibit proliferation and migration of bone marrow mesenchymal stem cells

Background

Advanced glycation products (AGEs), as endogenous inflammatory mediator, compromise the physiological function of mesenchymal stem cells (MSCs). MSCs have a potential role in cell replacement therapy in acute myocardial infarction and ischemic cardiomyopathy. However, mechanisms of AGEs on MSCs are still not unveiled.

Methods

Reactive oxygen species (ROS), genes regulation, cell proliferation and migration have been detected by AGE-BSA stimulated MSCs.

Results

We found that in vitro stimulation with AGE-BSA induced generation of reactive oxygen species (ROS), and inhibited dose-dependently proliferation and migration of MSCs. Microarray and molecular biological assessment displayed an increased expression and secretion of Ccl2, Ccl3, Ccl4 and Il1b in a dose- and time-dependent manner. These chemokines/cytokines of equivalent concentration to those in conditioned medium exerted an inhibitory effect on MSC proliferation and migration after stimulation for 24 h. Transient elevation of phospho-p38 in MSCs upon AGE-BSA stimulation was blocked with p38 inhibitor.

Conclusions

The study indicates that AGE-BSA induces production of chemokines/cytokines in a dose- and time-dependent manner via activation of ROS-p38 mediated pathway. These chemokines/cytokines exert an inhibitory effect on MSC growth and migration, suggesting an amplified dysfunction of MSCs by AGEs.

Adult human mesenchymal cells proliferate and migrate in response to chemokines expressed in demyelination

Systemic delivery of multipotent mesenchymal stem cells (MSC) may be of benefit in the treatment of neurological diseases, including multiple sclerosis (MS). Certainly, animal studies have demonstrated functional benefits following MSC transplantation, although the mechanisms by which MSCs migrate to lesions and stimulate repair remain unknown. Chemokines stimulate migration in other settings. In this study, we systematically explore the migratory and proliferative responses of human MSCs (hMSC) to chemokines expressed in MS lesions. We demonstrate that these chemokines trigger hMSC migration. In addition, we show that RANTES and IP-10 promote hMSC proliferation.

Simultaneous cultivation of human endothelial-like differentiated precursor cells and human marrow stromal cells on beta-tricalcium phosphate

AIM

The size of a bone defect limits the ingrowth of bone-forming cells. Endothelial cell-like differentiated precursor cells (endothelial progenitor cells, EPC) enhance the neovascularization, while marrow stromal cells (MSC) promote the repair of bone defects. Our aim was to evaluate if both types of cells can be cocultivated on a beta-tricalcium phosphate (beta-TCP) matrix and maintain their differentiation capacity as well as to analyze the biologic activity of these cell constructs in vivo.

METHODS

MSC from human bone marrow and EPC from buffy coat were used. EPC and MSC, alone or in combination, were seeded on fibronectin-coated beta-TCP. After 2, 6, and 10 days the metabolic activity and the endothelial differentiation were tested. On day 10 real-time RT-PCRs for endothelial genes (von Willebrandt factor, vascular endothelial growth factor, and vascular endothelial growth factor-receptor 2), osteogenic genes (osteocalcin, cbfa-1, and collagen-1alpha), and the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase were performed. Cell-containing constructs were implanted into the critical-size defect of the femur of the nude rat. Bone formation and vascularization was determined after 1 week.

RESULTS

MSC and EPC on beta-TCP remain metabolically active over 10 days. They maintain their differentiation as measured by means of Dil-ac-LDL uptake (EPC) and gene expression of lineage typical genes (EPC + MSC). Although a potential osteogenic differentiation of MSC was maybe affected negatively, constructs loaded with MSC resulted in an increase of new bone mass. Constructs containing EPC resulted in an improved vasculogenesis in vivo.

DISCUSSION

MSC and EPC can be cultivated in combination on a fibronectin-coated beta-TCP, thereby partly maintaining their lineage typical gene expression. The results of the in vivo examinations suggest that beta-TCP combined with EPC and MSC can used as a suitable tool to foster bone healing.

IKK-2 is required for TNF-alpha-induced invasion and proliferation of human mesenchymal stem cells

Mesenchymal stem cells (MSCs) can contribute to tissue repair by actively migrating to sites of tissue injury. However, the cellular and molecular mechanisms of MSC recruitment are largely unknown. The nuclear factor (NF)-kappaB pathway plays a pivotal role in regulating genes that influence cell migration, cell differentiation, inflammation, and proliferation. One of the major cytokines released at sites of injury is tumor necrosis factor-alpha (TNF-alpha), which is known to be a key regulator of the NF-kappaB pathway. Therefore, we hypothesized that TNF-alpha may lead to MSC invasion and proliferation by activation of the NF-kappaB pathway. TNF-receptor 1 and 2, NF-kappaB (p65), and IkappaB kinase 2 (IKK-2) are expressed in human MSCs (hMSCs). Stimulation of hMSCs with TNF-alpha caused a p65 translocation from the cytoplasm to nucleoplasm but did not change the expression profile of MSC markers. TNF-alpha strongly augmented the migration of hMSCs through the human extracellular matrix. Using lentiviral gene transfer, overexpressing a dominant-negative mutant of IKK-2 (dn-IKK-2) significantly blocked this effect. NF-kappaB target genes associated with migration (vascular cell adhesion molecule-1, CD44, and matrix metalloproteinase 9) were upregulated by TNF-alpha stimulation and blocked by dn-IKK-2. Moreover, using the bromodeoxyuridine assay, we showed that the inhibition of the NF-kappaB pathway caused a significant reduction in the basal proliferation rate. TNF-alpha stimulated the proliferation of hMSCs, whereas overexpression of dn-IKK-2 significantly blocked this effect. TNF-alpha led to the upregulated expression of the proliferation-associated gene cyclin D1. In conclusion, we demonstrated that the NF-kappaB pathway components, p65 and IKK-2, are expressed in hMSCs. Our data provide evidence that this signal transduction pathway is implicated in TNF-alpha-mediated invasion and proliferation of hMSCs. Therefore, hMSC recruitment to sites of tissue injury may, at least in part, be regulated by the NF-kappaB signal transduction pathway.