TNF receptor 2, not TNF receptor 1, enhances mesenchymal stem cell-mediated cardiac protection following acute ischemia

Therapeutic CRISPR epigenome editing of inflammatory receptors in the intervertebral disc

Low back pain (LBP) ranks among the leading causes of disability worldwide and generates a tremendous socioeconomic cost. Disc degeneration, a leading contributor to LBP, can be characterized by the breakdown of the extracellular matrix of the intervertebral disc (IVD), disc height loss, and inflammation. The inflammatory cytokine tumor necrosis factor α (TNF-α) has multiple signaling pathways, including proinflammatory signaling through tumor necrosis factor receptor 1 superfamily, member 1a (TNFR1 or TNFRSF1A), and has been implicated as a primary mediator of disc degeneration. We tested our ability to regulate the TNFR1 signaling pathway in vivo, utilizing CRISPR epigenome editing to slow the progression of disc degeneration in rats. Sprague-Dawley rats were treated with TNF-α and CRISPR interference (CRISPRi)-based epigenome-editing therapeutics targeting TNFR1, showing decreased behavioral pain in a disc degeneration model. Surprisingly, while treatment with the vectors alone was therapeutic, the TNF-α injection became therapeutic after TNFR1 modulation. These results suggest direct inflammatory receptor modulation as a potent strategy for treating disc degeneration.

Therapeutic and immunomodulatory potentials of mesenchymal stromal/stem cells and immune checkpoints related molecules

Mesenchymal stromal/stem cells (MSCs) are used in many studies due to their therapeutic potential, including their differentiative ability and immunomodulatory properties. These cells perform their therapeutic functions by using various mechanisms, such as the production of anti-inflammatory cytokines, growth factors, direct cell-to-cell contact, extracellular vesicles (EVs) production, and mitochondrial transfer. However, mechanisms related to immune checkpoints (ICPs) and their effect on the immunomodulatory ability of MSCs are less discussed. The main function of ICPs is to prevent the initiation of unwanted responses and to regulate the immune system responses to maintain the homeostasis of these responses. ICPs are produced by various types of immune system regulatory cells, and defects in their expression and function may be associated with excessive responses that can ultimately lead to autoimmunity. Also, by expressing different types of ICPs and their ligands (ICPLs), tumor cells prevent the formation and durability of immune responses, which leads to tumors' immune escape. ICPs and ICPLs can be produced by MSCs and affect immune cell responses both through their secretion into the microenvironment or direct cell-to-cell interaction. Pre-treatment of MSCs in inflammatory conditions leads to an increase in their therapeutic potential. In addition to the effect that inflammatory environments have on the production of anti-inflammatory cytokines by MSCs, they can increase the expression of various types of ICPLs. In this review, we discuss different types of ICPLs and ICPs expressed by MSCs and their effect on their immunomodulatory and therapeutic potential.

Preconditioning with Substance P Restores Therapeutic Efficacy of Aged ADSC by Elevating TNFR2 and Paracrine Potential

Aging leads to a decline in stem cell activity by reducing the repopulation rate and paracrine potential, ultimately diminishing efficacy in vivo. TNF-α can exert inflammatory and cell death actions via Erk by binding to TNFR-1, and survival and tissue repair actions via Akt by binding to TNFR-2. Aged cells are reported to have insufficient expression of TNFR-2, indicating that aged adipose-derived stem cells (ADSCs-E) lack the ability for cell survival and immune control compared to young ADSCs (ADSCs-Y). This study aims to assess the preconditioning effect of SP on the response of ADSCs-E to inflammation. ADSCs-E were treated with SP and then exposed to a high dose of TNF-α for 24 h. Consequently, ADSC-E exhibited weaker viability and lower TNFR2 levels compared to ADSC-Y. In response to TNF-α, the difference in TNFR2 expression became more pronounced in ADSC-E and ADSC-Y. Moreover, ADSC-E showed a severe deficiency in proliferation and paracrine activity. However, preconditioning with SP significantly enhanced the viability of ADSCs-E and also restored TNFR2 expression and paracrine potential, similar to ADSC-Y under inflammatory conditions. Our findings support the idea that preconditioning with SP has the potential to restore the cellular function of senescent stem cells before transplantation.

Therapeutic TNF-alpha Delivery After CRISPR Receptor Modulation in the Intervertebral Disc

Low back pain (LBP) ranks among the leading causes of disability worldwide and generates a tremendous socioeconomic cost. Disc degeneration, a leading contributor to LBP, can be characterized by the breakdown of the extracellular matrix of the intervertebral disc (IVD), disc height loss, and inflammation. The inflammatory cytokine TNF-α has multiple pathways and has been implicated as a primary mediator of disc degeneration. We tested our ability to regulate the multiple TNF-α inflammatory signaling pathways in vivo utilizing CRISPR receptor modulation to slow the progression of disc degeneration in rats. Sprague-Dawley rats were treated with CRISPRi-based epigenome-editing therapeutics targeting TNFR1 and showed a decrease in behavioral pain in a disc degeneration model. Surprisingly, while treatment with the vectors alone was therapeutic, TNF-α injection itself became therapeutic after TNFR1 modulation. These results suggest direct inflammatory receptor modulation, to harness beneficial inflammatory signaling pathways, as a potent strategy for treating disc degeneration.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Biophotonic Effects of Low-Level Laser Therapy on Adipose-Derived Stem Cells for Soft Tissue Deficiency

PURPOSES

The objectives of this study are to use diode lasers for low-level laser therapy (LLLT) and to assess its applicability and effects in adipose-derived stem cell (ADSC) growth processes.

METHODS

Studies were conducted on the diode laser with wavelengths of 622.7, 527.1, and 467.3 nm. The mechanism of action of LLL illumination was studied on ADSCs, isolated from human tissue, and then cultured by examining different wavelengths to determine the relevant light parameters for optimal responses. We used enzyme-linked immunosorbent assay and real-time polymerase chain to determine the percentages of fibroblast-mediated procollagen type 1 and matrix metallopeptidase 1 (MMP-1), MMP-2, and MMP-9 production at different wavelengths. The levels of lactate dehydrogenase produced by ADSCs after LLL illumination were assessed as well. Clinical results from 20 patients treated for soft tissue deficiency were collected for assessment of ADSC-assisted lipotransfer.

RESULTS

Low-level laser (622.7 nm) illumination on cell cultures in vitro increased ADSCs proliferation, type 1 procollagen expression, collagen production, as well as MMP-1, MMP-2, and MMP-9 relative expression. Statistical analysis demonstrated a significant difference in red light (622.7 nm) versus green light (527.1 nm) and blue light (467.3 nm, P < 0.05). No significant differences were noted between the effects of green and blue lights. In clinical application, all patients attained significant improvement with treatment in the final outcome assessment after 6 months.

CONCLUSIONS

Low-level laser illumination may affect ADSCs growth processes and ADSC-assisted lipotransfer for soft tissue deformity, scar treatment, wound healing, and other reconstructive surgery.

TNFR2 expression predicts the responses to immune checkpoint inhibitor treatments

Immune checkpoint inhibitors (ICIs) by targeting PD-1/PD-L1 or CTLA-4 have markedly improved the outcome of cancer patients. However, most solid tumor patients can't benefit from such therapy. Identification of novel biomarkers to predict the responses of ICIs is crucial to enhance their therapeutic efficacy. TNFR2 is highly expressed by the maximally immunosuppressive subset of CD4⁺Foxp3⁺ regulatory T cells (Tregs), especially those present in tumor microenvironment (TME). Since Tregs represent a major cellular mechanism in tumor immune evasion, TNFR2 may be a useful biomarker to predict the responses to ICIs therapy. This notion is supported by our analysis of the computational tumor immune dysfunction and exclusion (TIDE) framework from published single-cell RNA-seq data of pan-cancer databases. The results show that, as expected, TNFR2 is highly expressed by tumor-infiltrating Tregs. Interestingly, TNFR2 is also expressed by the exhausted CD8 T cells in breast cancer (BRCA), hepatocellular carcinoma (HCC), lung squamous cell carcinoma (LUSC), and melanoma (MELA). Importantly, high expression of TNFR2 is associated with poor responses to the treatment with ICIs in BRCA, HCC, LUSC, and MELA. In conclusion, the expression of TNFR2 in TME may be a reliable biomarker for the precision of ICIs treatment of cancer patients, and this idea merits further research.

Modulation of Mesenchymal Stem Cells for Enhanced Therapeutic Utility in Ischemic Vascular Diseases

Mesenchymal stem cells are multipotent stem cells isolated from various tissue sources, including but not limited to bone marrow, adipose, umbilical cord, and Wharton Jelly. Although cell-mediated mechanisms have been reported, the therapeutic effect of MSCs is now recognized to be primarily mediated via paracrine effects through the secretion of bioactive molecules, known as the “secretome”. The regenerative benefit of the secretome has been attributed to trophic factors and cytokines that play neuroprotective, anti-angiogenic/pro-angiogenic, anti-inflammatory, and immune-modulatory roles. The advancement of autologous MSCs therapy can be hindered when introduced back into a hostile/disease environment. Barriers include impaired endogenous MSCs function, limited post-transplantation cell viability, and altered immune-modulatory efficiency. Although secretome-based therapeutics have gained popularity, many translational hurdles, including the heterogeneity of MSCs, limited proliferation potential, and the complex nature of the secretome, have impeded the progress. This review will discuss the experimental and clinical impact of restoring the functional capabilities of MSCs prior to transplantation and the progress in secretome therapies involving extracellular vesicles. Modulation and utilization of MSCs–secretome are most likely to serve as an effective strategy for promoting their ultimate success as therapeutic modulators.

MicroRNA-425-5p modulates osteoporosis by targeting annexin A2

Background

Studies have shown that the decrease of osteogenic differentiation of bone marrow mesenchymal stem cells (MSC) is an important mechanism of osteoporosis. The object of this study was to explore the role and mechanism of microRNA miR-425-5p in the differentiation of MSC.

Methods

The expression of miR-425-5p in MSC was detected by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Cell proliferation, cell cycle and apoptosis were detected by CCK-8 colorimetry and flow cytometry. The expression of TNF were detected by ELISA.

Results

Our data show that MiR-425-5p could modulate TNF-induced cell apoptosis, proliferation, and differentiation. ANXA2 is also the target of miR-425-5p and ANXA2 was involved in TNF-induced MSC cell apoptosis, proliferation, and differentiation. In addition, MiR-425-5p enhanced osteoporosis in mice.

Conclusion

MiR-425-5p might serve as a potential therapeutic target for the treatment of osteoporosis.

Etanercept-Induced Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane (anti-GBM) disease is a rare form of small-vessel vasculitis that typically causes rapidly progressive glomerulonephritis with or without alveolar haemorrhage. Previously, there has only been one reported case of tumour necrosis factor-α (TNF-α) antagonist-induced anti-GBM disease. Here, we describe the first reported case of etanercept-induced anti-GBM disease. A 55-year-old Caucasian man was referred to our tertiary specialist renal centre with a history of painless macroscopic haematuria. The patient has been receiving weekly etanercept injections over the past 12 months for psoriatic arthropathy. The serum immunology panel results highlighted a significantly raised anti-GBM titre (370.1 U). Etanercept was stopped, and the patient was empirically commenced on pulsed methylprednisolone, cyclophosphamide, and plasma exchange. A renal biopsy showed crescentic glomerulonephritis. Few days after admission, he tested positive for coronavirus disease 2019 (COVID-19), and a decision was made to withhold cyclophosphamide. There was further decline in renal function with hyperkalaemia for which he received 2 sessions of haemodialysis. He was restarted on cyclophosphamide upon discharge. The patient was switched to rituximab treatment afterwards as he developed leucopenia 2 weeks following the commencement of cyclophosphamide. The serum creatinine level continued to improve and remained dialysis-independent. In conclusion, with the increased use of etanercept and other TNF-α antagonists, the prescribing clinician must be aware of the rare but life-threatening drug-induced vasculitis. We recommend careful monitoring of renal indices with the use of this class of medications.

LBO-EMSC Hydrogel Serves a Dual Function in Spinal Cord Injury Restoration via the PI3K-Akt-mTOR Pathway

It is critical to obtain an anti-inflammatory microenvironment when curing spinal cord injury (SCI). On the basis of this, we prepared Lycium barbarum oligosaccharide (LBO)-nasal mucosa-derived mesenchymal stem cells (EMSCs) fibronectin hydrogel for SCI restoration via inflammatory license effect and M2 polarization of microglias. LBO exhibited remarkable M2 polarization potential for microglia. However, EMSCs primed by LBO generated enhanced paracrine effects through the inflammatory license-like process. The observed dual function is likely based on the TNFR2 pathway. In addition, LBO-EMSC hydrogel possesses a synergistic effect on M2 polarization of microglia through the PI3K-Akt-mTOR signaling pathway. The obtained findings provide a simple approach for MSC-based therapies for SCI and shed more light on the role of TNFR2 on bidirectional regulation in tissue regeneration.

TNF-TNFR2 Signal Plays a Decisive Role in the Activation of CD4+Foxp3+ Regulatory T Cells: Implications in the Treatment of Autoimmune Diseases and Cancer

The puzzling biphasic or dual roles of tumor necrosis factor α (TNF) in the inflammatory and immune responses are likely to be mediated by distinct signaling pathways transduced by one of its two receptors, e.g., TNF receptor type I (TNFR1) and TNF receptor type II (TNFR2). Unlike TNFR1 that is ubiquitously expressed on almost all types of cells, the expression of TNFR2 is rather restricted to certain types of cells, such as T lymphocytes. There is now compelling evidence that TNFR2 is preferentially expressed by CD4⁺Foxp3⁺ regulatory T cells (Tregs), and TNFR2 plays a decisive role in the activation, expansion, in vivo function, and phenotypical stability of Tregs. In this chapter, the current understanding of the molecular basis and signaling pathway of TNF-TNFRs signal is introduced. Latest studies that have further supported and substantiated the pivotal role of TNF-TNFR2 interaction in Tregs biology and its molecular basis are discussed. The research progress regarding TNFR2-targeting treatment for autoimmune diseases and cancer is analyzed. Future study should focus on the further understanding of molecular mechanism underlying Treg-stimulatory effect of TNFR2 signal, as well as on the translation of research findings into therapeutic benefits of human patients with autoimmune diseases, allergy, allograft rejection, and cancer.

TNFR2 Is a Crucial Hub Controlling Mesenchymal Stem Cell Biological and Functional Properties

Mesenchymal stem cells (MSCs) have drawn lots of attention as gold standard stem cells in fundamental and clinical researches during the last 20 years. Due to their tissue and vascular repair capacities, MSCs have been used to treat a variety of degenerative disorders. Moreover, MSCs are able to modulate immune cells’ functions, particularly T cells while inducing regulatory T cells (iTregs). MSCs are very sensitive to inflammatory signals. Their biological functions could remarkably vary after exposure to different pro-inflammatory cytokines, notably TNFα. In this article, we have explored the importance of TNFR2 expression in a series of MSCs’ biological and functional properties. Thus, MSCs from wild-type (WT) and TNFR2 knockout (TNFR2 KO) mice were isolated and underwent several ex vivo experiments to investigate the biological significance of TNFR2 molecule in MSC main functions. Hampering in TNFR2 signaling resulted in reduced MSC colony-forming units and proliferation rate and diminished the expression of all MSC characteristic markers such as stem cell antigen-1 (Sca1), CD90, CD105, CD44, and CD73. TNFR2 KO-MSCs produced more pro-inflammatory cytokines like TNFα, IFNγ, and IL-6 and less anti-inflammatory mediators such as IL-10, TGFβ, and NO and induced Tregs with less suppressive effect. Furthermore, the TNFR2 blockade remarkably decreased MSC regenerative functions such as wound healing, complex tube formation, and endothelial pro-angiogenic support. Therefore, our results reveal the TNFα–TNFR2 axis as a crucial regulator of MSC immunological and regenerative functions.

Tumor Necrosis Factor Receptors: Pleiotropic Signaling Complexes and Their Differential Effects

Since its discovery in 1975, TNFα has been a subject of intense study as it plays significant roles in both immunity and cancer. Such attention is well deserved as TNFα is unique in its engagement of pleiotropic signaling via its two receptors: TNFR1 and TNFR2. Extensive research has yielded mechanistic insights into how a single cytokine can provoke a disparate range of cellular responses, from proliferation and survival to apoptosis and necrosis. Understanding the intracellular signaling pathways induced by this single cytokine via its two receptors is key to further revelation of its exact functions in the many disease states and immune responses in which it plays a role. In this review, we describe the signaling complexes formed by TNFR1 and TNFR2 that lead to each potential cellular response, namely, canonical and non-canonical NF-κB activation, apoptosis and necrosis. This is followed by a discussion of data from in vivo mouse and human studies to examine the differential impacts of TNFR1 versus TNFR2 signaling.

TNFα/TNFR2 signaling pathway: an active immune checkpoint for mesenchymal stem cell immunoregulatory function

BACKGROUND

In addition to their multilineage potential, mesenchymal stem cells (MSCs) have a broad range of functions from tissue regeneration to immunomodulation. MSCs have the ability to modulate the immune response and change the progression of different inflammatory and autoimmune disorders. However, there are still many challenges to overcome before their widespread clinical administration including the mechanisms behind their immunoregulatory function. MSCs inhibit effector T cells and other immune cells, while inducing regulatory T cells (T regs), thus, reducing directly and indirectly the production of pro-inflammatory cytokines. TNF/TNFR signaling plays a dual role: while the interaction of TNFα with TNFR1 mediates pro-inflammatory effects and cell death, its interaction with TNFR2 mediates anti-inflammatory effects and cell survival. Many immunosuppressive cells like T regs, regulatory B cells (B regs), endothelial progenitor cells (EPCs), and myeloid-derived suppressor cells (MDSCs) express TNFR2, and this is directly related to their immunosuppression efficiency. In this article, we investigated the role of the TNFα/TNFR2 immune checkpoint signaling pathway in the immunomodulatory capacities of MSCs.

METHODS

Co-cultures of MSCs from wild-type (WT) and TNFR2 knocked-out (TNFR2 KO) mice with T cells (WT and TNFα KO) were performed under various experimental conditions.

RESULTS

We demonstrate that TNFR2 is a key regulatory molecule which is strongly involved in the immunomodulatory properties of MSCs. This includes their ability to suppress T cell proliferation, activation, and pro-inflammatory cytokine production, in addition to their capacity to induce active T regs.

CONCLUSIONS

Our results reveal for the first time the importance of the TNFα/TNFR2 axis as an active immune checkpoint regulating MSC immunological functions.

Upregulated tumor necrosis factor-α transcriptome and proteome in adipose tissue-derived mesenchymal stem cells from pigs with metabolic syndrome

INTRODUCTION

Mesenchymal stem cells (MSCs) have endogenous reparative properties, and may constitute an exogenous therapeutic intervention in patients with chronic kidney disease. The microenvironment of metabolic syndrome (MetS) induces fat inflammation, with abundant expression of tumor necrosis factor (TNF)-α. MetS may also alter the content of adipose tissue-derived MSCs, and we hypothesized that the inflammatory profile of MetS manifests via upregulating MSC mRNAs and proteins of the TNF-α pathway.

METHODS

Domestic pigs were fed a 16-week Lean or MetS diet (n = 4 each). MSCs were harvested from abdominal subcutaneous fat, and their extracellular vesicles (EVs) isolated. Expression profiles of mRNAs and proteins in MSCs and EVs were obtained by high-throughput sequencing and proteomics. Nuclear translocation of the pro-inflammatory transcription factor (NF)-kB was evaluated in MSC and in pig renal tubular cells (TEC) co-incubated with EVs.

RESULTS

We found 13 mRNAs and 4 proteins in the TNF-α pathway upregulated in MetS- vs. Lean-MSCs (fold-change > 1.4, p < 0.05), mostly via TNF-α receptor-1 (TNF-R1) signaling. Three mRNAs were upregulated in MetS-EVs. MetS-MSCs, as well as TECs co-incubated with MetS-EVs, showed increased nuclear translocation of NF-kB. Using qPCR, JUNB, MAP2K7 and TRAF2 genes followed the same direction of RNA-sequencing findings.

CONCLUSIONS

MetS upregulates the TNF-α transcriptome and proteome in swine adipose tissue-derived MSCs, which are partly transmitted to their EV progeny, and are associated with activation of NF-kB in target cells. Hence, the MetS milieu may affect the profile of endogenous MSCs and their paracrine vectors and limit their use as an exogenous regenerative therapy. Anti-inflammatory strategies targeting the TNF-α pathway might be a novel strategy to restore MSC phenotype, and in turn function.

Improving Cell Therapy Survival and Anabolism in Harsh Musculoskeletal Disease Environments

Cell therapies are an up and coming technology in orthopedic medicine that has the potential to provide regenerative treatments for musculoskeletal disease. Despite numerous cell therapies showing preclinical success for common musculoskeletal indications of disc degeneration and osteoarthritis, there have been mixed results when testing these therapies in humans during clinical trials. A theory behind the mixed success of these cell therapies is that the harsh microenvironments of the disc and knee they are entering inhibit their anabolism and survival. Therefore, there is much ongoing research looking into how to improve the survival and anabolism of cell therapies within these musculoskeletal disease environments. This includes research into improving cell function under specific microenvironmental conditions known to exist in the intervertebral disc (IVD) and knee environment such as hypoxia, low-nutrient conditions, hyperosmolarity, acidity, and inflammation. This research also includes improving differentiation of cells into desired native cell phenotypes to better enhance their survival and anabolism in the knee and IVD. This review highlights the effects of specific musculoskeletal microenvironmental challenges on cell therapies and what research is being done to overcome these challenges. Impact statement While there has been significant clinical interest in using cell therapies for musculoskeletal pathologies in the knee and intervertebral disc, cell therapy clinical trials have had mixed outcomes. The information presented in this review includes the environmental challenges (i.e., acidic pH, inflammation, hyperosmolarity, hypoxia, and low nutrition) that cell therapies experience in these pathological musculoskeletal environments. This review summarizes studies that describe various approaches to improving the therapeutic capability of cell therapies in these harsh environments. The result is an overview of what approaches can be targeted and/or combined to develop a more consistent cell therapy for musculoskeletal pathologies.

Heart Failure and Adipose Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are considered a promising cell type for the treatment of heart failure (HF). In particular, MSCs in adipose tissue are being evaluated as an effective therapeutic tool. However, adipose MSCs are a major source of adipocyte generation and linked to obesity, which is an independent risk factor for HF. MSCs express all of the components of the renin-angiotensin system (RAS), which plays a pivotal role in the pathophysiology of HF. The local RAS also regulates MSC adipogenesis, indicating a connection between MSC-adipogenesis-obesity and HF. This review examines evidence of the complex relationship between HF and adipose MSCs and discusses how to explore this association for favorable therapeutic outcomes for HF.

Stem Cell-Derived Exosomes in Autism Spectrum Disorder

Neurodevelopmental lifelong pathologies defined by problems with social interaction, communication capacity and presence of repetitive/stereotyped clusters of behavior and interests are grouped under the definition of autism spectrum disorder (ASD). ASD prevalence is still increasing, indicating the need to identify specific biomarkers and novel pharmacotherapies. Neuroinflammation and neuro-immune cross-talk dysregulation are specific hallmarks of ASD, offering the possibility of treating these disorders by stem cell therapy. Indeed, cellular strategies have been postulated, proposed and applied to ASD. However, less is known about the molecular action mechanisms of stem cells. As a possibility, the positive and restorative effects mediated by stem cells could be due to their paracrine activity, by which stem cells produce and release several ameliorative and anti-inflammatory molecules. Among the secreted complex tools, exosomes are sub-organelles, enriched by RNA and proteins, that provide cell-to-cell communication. Exosomes could be the mediators of many stem cell-associated therapeutic activities. This review article describes the potential role of exosomes in alleviating ASD symptoms.

Critical role of Lin28-TNFR2 signalling in cardiac stem cell activation and differentiation

Tumour necrotic factor receptor-2 (TNFR2) has been to be cardiac-protective and is expressed in cardiac progenitor cells. Our goal is to define the mechanism for TNFR2-mediated cardiac stem cell activation and differentiation. By employing a protocol of in vitro cardiac stem cell (CSC) differentiation from human inducible pluripotent stem cell (hiPSC), we show that expression of TNFR2 precedes expression of CSC markers followed by expression of mature cardiomyocyte proteins. Activation of TNFR2 by a specific agonist promotes whereas inhibition of TNFR2 by neutralizing antibody diminishes hiPSC-based CSC differentiation. Interestingly, pluripotent cell factor RNA-binding protein Lin28 enhances TNFR2 protein expression in early CSC activation by directly binding to a conserved Lin28-motif within the 3'UTR of Tnfr2 mRNA. Furthermore, inhibition of Lin28 blunts TNFR2 expression and TNFR2-dependent CSC activation and differentiation. Our study demonstrates a critical role of Lin28-TNFR2 axis in CSC activation and survival, providing a novel strategy to enhance stem cell-based therapy for the ischaemic heart diseases.

The TNF Family of Ligands and Receptors: Communication Modules in the Immune System and Beyond

The tumor necrosis factor (TNF) and TNF receptor (TNFR) superfamilies (TNFSF/TNFRSF) include 19 ligands and 29 receptors that play important roles in the modulation of cellular functions. The communication pathways mediated by TNFSF/TNFRSF are essential for numerous developmental, homeostatic, and stimulus-responsive processes in vivo. TNFSF/TNFRSF members regulate cellular differentiation, survival, and programmed death, but their most critical functions pertain to the immune system. Both innate and adaptive immune cells are controlled by TNFSF/TNFRSF members in a manner that is crucial for the coordination of various mechanisms driving either co-stimulation or co-inhibition of the immune response. Dysregulation of these same signaling pathways has been implicated in inflammatory and autoimmune diseases, highlighting the importance of their tight regulation. Investigation of the control of TNFSF/TNFRSF activities has led to the development of therapeutics with the potential to reduce chronic inflammation or promote anti-tumor immunity. The study of TNFSF/TNFRSF proteins has exploded over the last 30 yr, but there remains a need to better understand the fundamental mechanisms underlying the molecular pathways they mediate to design more effective anti-inflammatory and anti-cancer therapies.

Critical Role of Tumor Necrosis Factor Signaling in Mesenchymal Stem Cell-Based Therapy for Autoimmune and Inflammatory Diseases

Mesenchymal stem cells (MSCs) have been broadly used as a therapy for autoimmune disease in both animal models and clinical trials. MSCs inhibit T effector cells and many other immune cells, while activating regulatory T cells, thus reducing the production of pro-inflammatory cytokines, including tumor necrosis factor (TNF), and repressing inflammation. TNF can modify the MSC effects via two TNF receptors, i.e., TNFR1 in general mediates pro-inflammatory effects and TNFR2 mediates anti-inflammatory effects. In the central nervous system, TNF signaling plays a dual role, which enhances inflammation via TNFR1 on immune cells while providing cytoprotection via TNFR2 on neural cells. In addition, the soluble form of TNFR1 and membrane-bound TNF also participate in the regulation to fine-tune the functions of target cells. Other factors that impact TNF signaling and MSC functions include the gender of the host, disease course, cytokine concentrations, and the length of treatment time. This review will introduce the fascinating progress in this aspect of research and discuss remaining questions and future perspectives.

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

Mesenchymal TNFR2 promotes the development of polyarthritis and comorbid heart valve stenosis

Mesenchymal TNF signaling is etiopathogenic for inflammatory diseases such as rheumatoid arthritis and spondyloarthritis (SpA). The role of Tnfr1 in arthritis has been documented; however, Tnfr2 functions are unknown. Here, we investigate the mesenchymal-specific role of Tnfr2 in the TnfΔARE mouse model of SpA in arthritis and heart valve stenosis comorbidity by cell-specific, Col6a1-cre-driven gene targeting. We find that TNF/Tnfr2 signaling in resident synovial fibroblasts (SFs) and valvular interstitial cells (VICs) is detrimental for both pathologies, pointing to common cellular mechanisms. In contrast, systemic Tnfr2 provides protective signaling, since its complete deletion leads to severe deterioration of both pathologies. SFs and VICs lacking Tnfr2 fail to acquire pathogenic activated phenotypes and display increased expression of antiinflammatory cytokines associated with decreased Akt signaling. Comparative RNA sequencing experiments showed that the majority of the deregulated pathways in TnfΔARE mesenchymal-origin SFs and VICs, including proliferation, inflammation, migration, and disease-specific genes, are regulated by Tnfr2; thus, in its absence, they are maintained in a quiescent nonpathogenic state. Our data indicate a pleiotropy of Tnfr2 functions, with mesenchymal Tnfr2 driving cell activation and arthritis/valve stenosis pathogenesis only in the presence of systemic Tnfr2, whereas nonmesenchymal Tnfr2 overcomes this function, providing protective signals and, thus, containing both pathologies.

Modulation of Regulatory T Cell Activity by TNF Receptor Type II-Targeting Pharmacological Agents

There is now compelling evidence that tumor necrosis factor (TNF)-TNF receptor type II (TNFR2) interaction plays a decisive role in the activation, expansion, and phenotypical stability of suppressive CD4⁺Foxp3⁺ regulatory T cells (Tregs). In an effort to translate this basic research finding into a therapeutic benefit, a number of agonistic or antagonistic TNFR2-targeting biological agents with the capacity to activate or inhibit Treg activity have been developed and studied. Recent studies also show that thalidomide analogs, cyclophosphamide, and other small molecules are able to act on TNFR2, resulting in the elimination of TNFR2-expressing Tregs. In contrast, pharmacological agents, such as vitamin D3 and adalimumab, were reported to induce the expansion of Tregs by promoting the interaction of transmembrane TNF (tmTNF) with TNFR2. These studies clearly show that TNFR2-targeting pharmacological agents represent an effective approach to modulating the function of Tregs and thus may be useful in the treatment of major human diseases such as autoimmune disorders, graft-versus-host disease (GVHD), and cancer. In this review, we will summarize and discuss the latest progress in the study of TNFR2-targeting pharmacological agents and their therapeutic potential based on upregulation or downregulation of Treg activity.

TNFR2: The new Treg switch?

Three recent publications identified the TNF/TNR2 pathway as a new target to reduce graft-versus-host-disease through regulatory T cells activation or to potentially switch on a strong anti-leukemic effect through regulatory T cells blockade in allogeneic hematopoietic stem cell transplantation. This identified the TNF/TNR2 pathway as a swith and as a new target for immune checkpoint therapy to modulate the immune regulation in this clinical setting.

* CRISPR-Based Epigenome Editing of Cytokine Receptors for the Promotion of Cell Survival and Tissue Deposition in Inflammatory Environments

Musculoskeletal diseases have been associated with inflammatory cytokine action, particularly action by TNF-α and IL-1β. These inflammatory cytokines promote apoptosis and senescence of cells in diseased tissue and extracellular matrix breakdown. Stem cell-based therapies are being considered for the treatment of musculoskeletal diseases, but the presence of these inflammatory cytokines will have similar deleterious action on therapeutic cells delivered to these environments. Methods that prevent inflammatory-induced apoptosis and proinflammatory signaling, in cell and pathway-specific manners are needed. In this study we demonstrate the use of clustered regularly interspaced short palindromic repeats (CRISPR)-based epigenome editing to alter cell response to inflammatory environments by repressing inflammatory cytokine cell receptors, specifically TNFR1 and IL1R1. We targeted CRISPR/Cas9-based repressors to TNFR1 and IL1R1 gene regulatory elements in human adipose-derived stem cells (hADSCs) and investigated the functional outcomes of repression of these genes. Efficient signaling regulation was demonstrated in engineered hADSCs, as activity of the downstream transcription factor NF-κB was significantly reduced or maintained at baseline levels in the presence of TNF-α or IL-1β. Pellet culture of undifferentiated hADSCs demonstrated improved survival in engineered hADSCs treated with TNF-α or IL-1β, while having little effect on their immunomodulatory properties. Furthermore, engineered hADSCs demonstrated improved chondrogenic differentiation capacity in the presence of TNF-α or IL-1β, as shown by superior production of glycosaminglycans in this inflammatory environment. Overall this work demonstrates a novel method for modulating cell response to inflammatory signaling that has applications in engineering cells delivered to inflammatory environments, and as a direct gene therapy to protect endogenous cells exposed to chronic inflammation, as observed in a broad spectrum of degenerative musculoskeletal pathology.

Targeting TNFR2, an immune checkpoint stimulator and oncoprotein, is a promising treatment for cancer

Tumor necrosis factor receptor 2 (TNFR2) is expressed both by some cancer cells and by tumor-infiltrating immunosuppressive CD4⁺FoxP3⁺ regulatory T cells (T_regs). TNFR2 stimulates the activation and proliferation of T_regs, a major checkpoint of antitumor immune responses, and promotes cancer cell survival and tumor growth. In this issue of Science Signaling, Torrey et al found that dominant antagonistic antibodies against human TNFR2 may be a potential therapy for ovarian cancer patients by simultaneously suppressing T_reg activity and inducing the death of the cancer cells.

Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue

Mesenchymal stem cells (MSCs) are broadly distributed cells that retain postnatal capacity for self-renewal and multilineage differentiation. MSCs evade immune detection, secrete an array of anti-inflammatory and anti-fibrotic mediators, and very importantly activate resident precursors. These properties form the basis for the strategy of clinical application of cell-based therapeutics for inflammatory and fibrotic conditions. In cardiovascular medicine, administration of autologous or allogeneic MSCs in patients with ischemic and nonischemic cardiomyopathy holds significant promise. Numerous preclinical studies of ischemic and nonischemic cardiomyopathy employing MSC-based therapy have demonstrated that the properties of reducing fibrosis, stimulating angiogenesis, and cardiomyogenesis have led to improvements in the structure and function of remodeled ventricles. Further attempts have been made to augment MSCs' effects through genetic modification and cell preconditioning. Progression of MSC therapy to early clinical trials has supported their role in improving cardiac structure and function, functional capacity, and patient quality of life. Emerging data have supported larger clinical trials that have been either completed or are currently underway. Mechanistically, MSC therapy is thought to benefit the heart by stimulating innate anti-fibrotic and regenerative responses. The mechanisms of action involve paracrine signaling, cell-cell interactions, and fusion with resident cells. Trans-differentiation of MSCs to bona fide cardiomyocytes and coronary vessels is also thought to occur, although at a nonphysiological level. Recently, MSC-based tissue engineering for cardiovascular disease has been examined with quite encouraging results. This review discusses MSCs from their basic biological characteristics to their role as a promising therapeutic strategy for clinical cardiovascular disease.

Tumor Necrosis Factor α Regulates Endothelial Progenitor Cell Migration via CADM1 and NF-kB

Shortly after the discovery of endothelial progenitor cells (EPCs) in 1997, many clinical trials were conducted using EPCs as a cellular based therapy with the goal of restoring damaged organ function by inducing growth of new blood vessels (angiogenesis). Results were disappointing, largely because the cellular and molecular mechanisms of EPC-induced angiogenesis were not clearly understood. Following injection, EPCs must migrate to the target tissue and engraft prior to induction of angiogenesis. In this study EPC migration was investigated in response to tumor necrosis factor α (TNFα), a pro-inflammatory cytokine, to test the hypothesis that organ damage observed in ischemic diseases induces an inflammatory signal that is important for EPC homing. In this study, EPC migration and incorporation were modeled in vitro using a coculture assay where TNFα treated EPCs were tracked while migrating toward vessel-like structures. It was found that TNFα treatment of EPCs increased migration and incorporation into vessel-like structures. Using a combination of genomic and proteomic approaches, NF-kB mediated upregulation of CADM1 was identified as a mechanism of TNFα induced migration. Inhibition of NF-kB or CADM1 significantly decreased migration of EPCs in vitro suggesting a role for TNFα signaling in EPC homing during tissue repair. Stem Cells 2016;34:1922-1933.

Controlled Inhibition of the Mesenchymal Stromal Cell Pro-inflammatory Secretome via Microparticle Engineering

Mesenchymal stromal cells (MSCs) are promising therapeutic candidates given their potent immunomodulatory and anti-inflammatory secretome. However, controlling the MSC secretome post-transplantation is considered a major challenge that hinders their clinical efficacy. To address this, we used a microparticle-based engineering approach to non-genetically modulate pro-inflammatory pathways in human MSCs (hMSCs) under simulated inflammatory conditions. Here we show that microparticles loaded with TPCA-1, a small-molecule NF-κB inhibitor, when delivered to hMSCs can attenuate secretion of pro-inflammatory factors for at least 6 days in vitro. Conditioned medium (CM) derived from TPCA-1-loaded hMSCs also showed reduced ability to attract human monocytes and prevented differentiation of human cardiac fibroblasts to myofibroblasts, compared with CM from untreated or TPCA-1-preconditioned hMSCs. Thus, we provide a broadly applicable bioengineering solution to facilitate intracellular sustained release of agents that modulate signaling. We propose that this approach could be harnessed to improve control over MSC secretome post-transplantation, especially to prevent adverse remodeling post-myocardial infarction.

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Soluble TPCA-1 attenuates pro-inflammatory secretome in TNF-α-stimulated hMSCs

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TPCA preconditioning fails to inhibit pro-inflammatory secretome in TNF-hMSCs

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TPCA-μP-hMSCs demonstrate sustained inhibition of pro-inflammatory secretome

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Engineered hMSCs inhibit α-SMA expression and collagen deposition in cardiac fibroblasts

Identification of genetic variants in TNF receptor 2 which are associated with the development of cervical carcinoma

Cervical cancer is one of the most common malignancies among women in India. Beside HPV, other factors present in host also put their role in the progression of cervical tumerogenesis. In present study, we screened 300 subjects to identify variations in TNFR2 gene by PCR-dHPLC method followed by direct sequencing. We identified six known and four novel variations in six different exons of TNFR2 gene. Out of these identified variations, five known variations were found to be significantly associated with the risk of cervical cancer (p < 0.0001). On construction of haplotypes, one haplotype (TTGCC) was emerged as a major protective type while two (CAAGC + CTGCC) were revealed as major risk haplotypes. In conclusion, postmenopausal women having CAAGC + CTGCC haplotypes in TNFR2 gene along with HPV infection and tobacco consumption may lead to the development of cervical cancer.

A New Paradigm in Cardiac Regeneration: The Mesenchymal Stem Cell Secretome

The potentialities to apply mesenchymal stem cells (MSCs) in regenerative medicine have been extensively studied over the last decades. In the cardiovascular disease (CVD) field, MSCs-based therapy is the subject of great expectations. Its therapeutic potential has been already shown in several preclinical models and both the safety and efficacy of MSCs-based therapy are being evaluated in humans. It is now clear that the predominant mechanism by which MSCs participate in heart tissue repair is through a paracrine activity. Via the production of a multitude of trophic factors endowed with different properties, MSCs can reduce tissue injury, protect tissue from further adverse effects, and enhance tissue repair. The present review discusses the current understanding of the MSCs secretome as a therapy for treatment of CVD. We provide insights into the possible employment of the MSCs secretome and their released extracellular vesicles as novel approaches for cardiac regeneration that would have certain advantages over injection of living cells.

Association of TNF-α with impaired migration capacity of mesenchymal stem cells in patients with systemic lupus erythematosus

Previous studies indicated that bone marrow mesenchymal stem cells (BMSCs) from patients with systemic lupus erythematosus (SLE) exhibited impaired capacities of proliferation, differentiation, and immune modulation. Considering that migration capacity is important for the exertion of BMSCs functions, the defects in migration might contribute to BMSCs dysfunction in SLE patients. In this study, we showed that the migration capacity of SLE BMSCs was remarkably impaired in comparison with those of healthy controls. Increased tumor necrosis factor α (TNF-α) in SLE serum significantly inhibited the migration capacity and in vivo homing capacity of SLE BMSCs via a specific TNF receptor I (TNFRI) manner, in which decreased HGF mRNA production caused by the activation of I kappa B kinase beta (IKK-β) pathway is partially involved. To our knowledge, this is the first report to discuss the possible mechanisms for impaired migration of BMSCs in SLE patients. Our results suggest that inhibition of TNF-α pathway might be helpful for accelerating BMSCs migration to the inflammatory microenvironment in SLE patients, thereby having a potential role in SLE treatment.

Tumor necrosis factor receptor 2: its contribution to acute cellular rejection and clear cell renal carcinoma

Tumor necrosis factor receptor 2 (TNFR2) is a type I transmembrane glycoprotein and one of the two receptors that orchestrate the complex biological functions of tumor necrosis factor (TNF, also designed TNF-α). Accumulating experimental evidence suggests that TNFR2 plays an important role in renal disorders associated with acute cellular rejection and clear cell renal carcinoma but its exact role in these settings is still not completely understood. This papers reviews the factors that may mediate TNFR2 induction in acute cellular rejection and clear cell renal carcinoma and its contribution to these conditions and discusses its therapeutic implications. A greater understanding of the function of TNFR2 may lead to the development of new anti-TNF drugs.

Mechanisms of load dependency of myocardial ischemia reperfusion injury

Coronary artery disease and associated ischemic heart disease are prevalent disorders worldwide. Further, systemic hypertension is common and markedly increases the risk for heart disease. A common denominator of systemic hypertension of various etiologies is increased myocardial load/mechanical stress. Thus, it is likely that high pressure/mechanical stress attenuates the contribution of cardioprotective but accentuates the contribution of cardiotoxic pathways thereby exacerbating the outcome of an ischemia reperfusion insult to the heart. Critical events which contribute to cardiomyocyte injury in the ischemic-reperfused heart include cellular calcium overload and generation of reactive oxygen/nitrogen species which, in turn, promote the opening of the mitochondrial permeability transition pore, an important event in cell death. Increasing evidence also indicates that the myocardium is capable of mounting a robust inflammatory response which contributes importantly to tissue injury. On the other hand, cardioprotective maneuvers of ischemic preconditioning and postconditioning have led to identification of complex web of signaling pathways (e.g., reperfusion injury salvage kinase) which ultimately converge on the mitochondria to exert cytoprotection. The present review is intended to briefly describe mechanisms of cardiac ischemia reperfusion injury followed by a discussion of our work focused on how pressure/mechanical stress modulates endogenous cardiotoxic and cardioprotective mechanisms to ultimately exacerbate ischemia reperfusion injury.

Comparison of the properties of human CD146+ and CD146- periodontal ligament cells in response to stimulation with tumour necrosis factor α

OBJECTIVES

Periodontal ligament stem cells (PDLSCs) can be used in periodontal regeneration. Tumour necrosis factor-alpha (TNF-α) participates in the regulation of cell proliferation, apoptosis, differentiation, and migration. However, whether TNF-α can affect the biological features of PDLSCs is still unclear. The objective of this study was to illustrate the biological effects (proliferation, apoptosis, osteogenesis and migration) of TNF-α on human CD146 positive periodontal ligament cells (CD146+PLDCs) and CD146 negative periodontal ligament cells (CD146-PDLCs).

METHODS

CD146±PDLCs were isolated from human PDLCs and analyzed using a fluorescence-activated cell sorter. The biological effects of TNF-α on CD146±PDLCs were evaluated by CCK-8 assay (proliferation), DAPI staining (apoptosis), alizarin red staining and alkaline phosphatase activities assay (osteogenesis), and wounding assay and transwell assay (migration).

RESULTS

CD146+PDLCs, which expressed MSC surface markers CD105, CD90, CD73, CD44, and Stro-1, showed higher proliferative and osteogenic potential than CD146-PDLCs. TNF-α at a dose of 2.5ng/ml was found to enhance both proliferation and osteogenesis in CD146+PDLCs. At 5ng/ml, TNF-α promoted proliferation, osteogenesis, and apoptosis in CD146+PDLCs and enhanced osteogenesis in CD146-PDLCs. At 10ng/ml, TNF-α only aggravated apoptosis in CD146+PDLCs. The migratory ability of both CD146+PDLCs and CD146-PDLCs was not altered by TNF-α.

CONCLUSIONS

CD146+PDLCs were subpopulation of MSC. It showed greater proliferative and osteogenic potential than CD146-PDLCs. At low concentration, TNF-α was beneficial to CD146+PDLCs on proliferation and osteogenesis, and at high concentration it was detrimental. CD146-PDLCs were found to be less sensitive to TNF-α.

Inhibition of ubiquitin protein expression and 20S proteasome activity by irbesartan prevents post-infarction ventricular remodeling and decreases TNF-α generation

Myocardial infarction (MI) may induce severe alterations of the cardiac contractile function that may, in turn, lead to heart failure (HF). The ubiquitin-proteasome system (UPS) plays a critical role in cardiac remodeling following MI. Angiotensin II type 1 receptor (AT1R) blockers effectively prevent left ventricular (LV) remodeling. However, it has not been elucidated whether the preventive effect of AT1R-blockers on LV remodeling is mediated through the UPS pathway. In the present study, with the use of cardiac morphometric parameters, haemodynamic measurements and enzyme-linked immunosorbent assay, we demonstrated that post-ischemic HF rats exhibited a significant increase in ventricular remodeling and irbesartan was effective in reversing cardiac remodeling. The expression of TNF-α, ubiquitin protein and 20S proteasome were significantly increased in the MI control group and irbesartan was shown to dose-dependently inhibit the expression of TNF-α, ubiquitin protein and 20S proteasome. In conclusion, it was hypothesized that UPS signaling is involved in ventricular remodeling following MI and the mechanism underlying the effect of irbesartan on ventricular remodeling may be associated with the downregulation of the expression of TNF-α, ubiquitin protein and 20S proteasome.

Novel biomarkers for the progression of diabetic nephropathy: soluble TNF receptors

Despite 2 decades of advances in therapy of diabetic patients, the prevalence of diabetic nephropathy among patients with diabetes has not decreased. However, large-scale multicenter studies have achieved great success in terms of the reduction of albuminuria, suggesting that albuminuria might not be an accurate surrogate marker for slowing the rate of renal function decline. It is important to be able to identify individuals at high risk for renal function decline, or ultimately, end-stage kidney disease (ESKD) and its associated cardiovascular disease (CVD). More sensitive early biomarkers, other than albuminuria and the estimated glomerular filtration rate (eGFR), should be required. Recently, serum concentrations of soluble tumor necrosis factor (TNF), receptor 1 (TNFR1), and TNFR2 have predicted future GFR loss and ESKD in patients of a wide variety of stages and both types of diabetes. Longitudinal interventional studies are needed to validate these biomarkers in a broad range of populations prior to implementation in routine diabetes management.

Ischemia/Reperfusion injury protection by mesenchymal stem cell derived antioxidant capacity

Mesenchymal stem cell (MSC) transplantation after ischemia/reperfusion (I/R) injury reduces infarct size and improves cardiac function. We used mouse ventricular myocytes (VMs) in an in vitro model of I/R to determine the mechanism by which MSCs prevent reperfusion injury by paracrine signaling. Exposure of mouse VMs to an ischemic challenge depolarized their mitochondrial membrane potential (Ψmito), increased their diastolic Ca(2+), and significantly attenuated cell shortening. Reperfusion of VMs with Ctrl tyrode or MSC-conditioned tyrode (ConT) resulted in a transient increase of the Ca(2+) transient amplitudes in all cells. ConT-reperfused cells exhibited a decreased number early after depolarization (EADs) (ConT: 6.3% vs. Ctrl: 28.4%) and prolonged survival (ConT: 58% vs. Ctrl: 33%). Ψmito rapidly recovered in Ctrl as well as ConT-treated VMs on reperfusion; however, in Ctrl solution, an exaggerated hyperpolarization of Ψmito was determined that preceded the collapse of Ψmito. The ability of ConT to attenuate the hyperpolarization of Ψmito was suppressed on inhibition of the PI3K/Akt signaling pathway or IK,ATP. However, protection of Ψmito was best mimicked by the reactive oxygen species (ROS) scavenger mitoTEMPO. Analysis of ConT revealed a significant antioxidant capacity that was linked to the presence of extracellular superoxide dismutase (SOD3) in ConT. In conclusion, MSC ConT protects VMs from simulated I/R injury by its SOD3-mediated antioxidant capacity and by delaying the recovery of Ψmito through Akt-mediated opening of IK,ATP. These changes attenuate reperfusion-induced ROS production and prevent the opening of the permeability transition pore and arrhythmic Ca(2+) release.

Ischemia-reperfusion injury: beneficial effects of mesenchymal stromal cells

PURPOSE OF REVIEW

Organ transplantation and other major surgeries are impacted by ischemia-reperfusion injury (IRI). Mesenchymal stromal cells (MSCs) recently became an attractive alternative therapeutic tool to combat IRI. The present review highlights the effects of MSCs in the preclinical animal models of IRI and clinical trials, and explains their potential modes of action based on the pathophysiological IRI cascade.

RECENT FINDINGS

The application of MSCs in animal models of IRI show anti-inflammatory and anti-apoptotic effects, particularly for damage to the kidneys, heart and lungs. The mechanism of MSC action remains unclear, but may involve paracrine factors which could include the transfer of microvesicles, RNA or mitochondria. Although few clinical trials have reached completion, adverse effects appear minimal.

SUMMARY

MSCs show promise in protecting against IRI-induced damage. They appear to help recovery mainly by affecting the levels of inflammation and apoptosis during the organ repair process. In addition, they may mediate immunomodulatory effects on the innate and adaptive immune processes triggered during reperfusion and reduce fibrosis. Success in preclinical animal models has led to the initiation of ongoing clinical trials.

Tumor necrosis factor receptors: biology and therapeutic potential in kidney diseases

The major evolutionary advance represented in the human immune system is a mechanism of antigen-directed immunity in which tumor necrosis factor (TNF)-α and TNF receptors (TNFRs) play essential roles. Binding of TNF-α to the 55-kDa type I TNFR (TNFR1, TNFRSF1A, CD120a, p55) or the 75-kDa type II TNFR (TNFR2, TNFRSF1B, CD120b, p75) activates signaling pathways controlling inflammatory, immune and stress responses, as well as host defense and apoptosis. Multiple studies have investigated the role of TNFRs in the development of early and late renal failure (diabetic nephropathy, nephroangiosclerosis, acute kidney transplant rejection, renal cell carcinoma, glomerulonephritis, sepsis and obstructive renal injury). This article reviews the general characteristics, the analytical aspects and the biology of TNFRs in this domain. In addition, the potential therapeutic application of specific TNFR blockers is discussed.

Repair mechanisms of bone marrow mesenchymal stem cells in myocardial infarction

The prognosis of patients with myocardial infarction (MI) and resultant chronic heart failure remains extremely poor despite advances in optimal medical therapy and interventional procedures. Animal experiments and clinical trials using adult stem cell therapy following MI have shown a global improvement of myocardial function. Bone marrow-derived mesenchymal stem cells (MSCs) hold promise for cardiac repair following MI, due to their multilineage, self-renewal and proliferation potential. In addition, MSCs can be easily isolated, expanded in culture, and have immunoprivileged properties to the host tissue. Experimental studies and clinical trials have revealed that MSCs not only differentiate into cardiomyocytes and vascular cells, but also secrete amounts of growth factors and cytokines which may mediate endogenous regeneration via activation of resident cardiac stem cells and other stem cells, as well as induce neovascularization, anti-inflammation, anti-apoptosis, anti-remodelling and cardiac contractility in a paracrine manner. It has also been postulated that the anti-arrhythmic and cardiac nerve sprouting potential of MSCs may contribute to their beneficial effects in cardiac repair. Most molecular and cellular mechanisms involved in the MSC-based therapy after MI are still unclear at present. This article reviews the potential repair mechanisms of MSCs in the setting of MI.

Sensing the cardiac environment: exploiting cues for regeneration

Recent pre-clinical and clinical studies indicate that certain exogenous stem cells and biomaterials can preserve cardiac tissue after myocardial infarction. Regarding stem cells, a growing body of data suggests that the short-term positive outcomes are mainly attributed to paracrine signaling mechanisms. The release of such factors is due to the cell's ability to sense cardiac environmentally derived cues, though the exact feedback loops are still poorly understood. However, given the limited engraftment and survival of transplanted cells in the ischemic environment, the long-term clinical benefits of these therapies have not yet been realized. To overcome this, the long-term controlled delivery of bioactive factors using biomaterials is a promising approach. A major challenge has been the ability to develop timely and spatially controlled gradients of different cues, pivotal for the development and regeneration of tissues. In addition, given the complexity of the remodeling process after myocardial infarction, multiple factors may be required at distinct disease stages to maximize therapeutic outcomes. Therefore, novel smart materials that can sense the surrounding environment and generate cues through on demand mechanisms will be of major importance in the translation of these promising advanced therapies. This article reviews how the cardiac environment can mediate the release profiles of bioactive cues from cells and biomaterials and how the controlled delivery impacts heart regeneration.

Mesenchymal stem cells for cardiac cell therapy

Despite refinements of medical and surgical therapies, heart failure remains a fatal disease. Myocardial infarction is the most common cause of heart failure, and only palliative measures are available to relieve symptoms and prolong the patient's life span. Because mammalian cardiomyocytes irreversibly exit the cell cycle at about the time of birth, the heart has traditionally been considered to lack any regenerative capacity. This paradigm, however, is currently shifting, and the cellular composition of the myocardium is being targeted by various regeneration strategies. Adult progenitor and stem cell treatment of diseased human myocardium has been carried out for more than 10 years (Menasche et al., 2001; Stamm et al., 2003), and it has become clear that, in humans, the regenerative capacity of hematopoietic stem cells and endothelial progenitor cells, despite potent proangiogenic effects, is limited (Stamm et al., 2009). More recently, mesenchymal stem cells (MSCs) and related cell types are being evaluated in preclinical models of heart disease as well as in clinical trials (see Published Clinical Trials, below). MSCs have the capacity to self-renew and to differentiate into lineages that normally originate from the embryonic mesenchyme (connective tissues, blood vessels, blood-related organs) (Caplan, 1991; Prockop, 1997; Pittenger et al., 1999). The current definition of MSCs includes plastic adherence in cell culture, specific surface antigen expression (CD105(+)/CD90(+)/CD73(+), CD34(-)/CD45(-)/CD11b(-) or CD14(-)/CD19(-) or CD79α(-)/HLA-DR1(-)), and multilineage in vitro differentiation potential (osteogenic, chondrogenic, and adipogenic) (Dominici et al., 2006 ). If those criteria are not met completely, the term "mesenchymal stromal cells" should be used for marrow-derived adherent cells, or other terms for MSC-like cells of different origin. For the purpose of this review, MSCs and related cells are discussed in general, and cell type-specific properties are indicated when appropriate. We first summarize the preclinical data on MSCs in models of heart disease, and then appraise the clinical experience with MSCs for cardiac cell therapy.

Stem cell-based therapies in ischemic heart diseases: a focus on aspects of microcirculation and inflammation

Stem cells possessing the potential to replace damaged myocardium with functional myocytes have drawn increasing attention in the past decade in treating ischemic heart diseases; these diseases are the leading cause of morbidity and mortality in the world. The adult heart has recently been shown to contain a few cardiac stem cells (CSCs) that, in theory, suggest cardiac repair following acute myocardial infarction is possible if the CSC titer could be increased. Stem cell-based therapies, including hematopoietic stem cells and mesenchymal stem cells, were proven to be marginal and transitional. Multiple factors and mechanisms, rather than direct cardiac regeneration are involved in stem cell-mediated cardiac functional improvement. This review will focus on (1) the interaction between inflammation and stem cells; (2) the fate of stem cells at the microcirculatory level, and their subsequent influences on stem cell-based therapies.

Mesenchymal stem cells at the intersection of cell and gene therapy

IMPORTANCE OF THE FIELD

Mesenchymal stem cells have the ability to differentiate into osteoblasts, chondrocytes and adipocytes. Along with differentiation, MSCs can modulate inflammation, home to damaged tissues and secrete bioactive molecules. These properties can be enhanced through genetic-modification that would combine the best of both cell and gene therapy fields to treat monogenic and multigenic diseases.

AREAS COVERED IN THIS REVIEW

Findings demonstrating the immunomodulation, homing and paracrine activities of MSCs followed by a summary of the current research utilizing MSCs as a vector for gene therapy, focusing on skeletal disorders, but also cardiovascular disease, ischemic damage and cancer.

WHAT THE READER WILL GAIN

MSCs are a possible therapy for many diseases, especially those related to the musculoskeletal system, as a standalone treatment, or in combination with factors that enhance the abilities of these cells to migrate, survive or promote healing through anti-inflammatory and immunomodulatory effects, differentiation, angiogenesis or delivery of cytolytic or anabolic agents.

TAKE HOME MESSAGE

Genetically-modified MSCs are a promising area of research that would be improved by focusing on the biology of MSCs that could lead to identification of the natural and engrafting MSC-niche and a consensus on how to isolate and expand MSCs for therapeutic purposes.

Paracrine mechanisms of stem cell reparative and regenerative actions in the heart

Stem cells play an important role in restoring cardiac function in the damaged heart. In order to mediate repair, stem cells need to replace injured tissue by differentiating into specialized cardiac cell lineages and/or manipulating the cell and molecular mechanisms governing repair. Despite early reports describing engraftment and successful regeneration of cardiac tissue in animal models of heart failure, these events appear to be infrequent and yield too few new cardiomyocytes to account for the degree of improved cardiac function observed. Instead, mounting evidence suggests that stem cell mediated repair takes place via the release of paracrine factors into the surrounding tissue that subsequently direct a number of restorative processes including myocardial protection, neovascularization, cardiac remodeling, and differentiation. The potential for diverse stem cell populations to moderate many of the same processes as well as key paracrine factors and molecular pathways involved in stem cell-mediated cardiac repair will be discussed in this review. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".