Aleksandar Arsenijevic

Mesenchymal stem cells attenuate acute liver injury by altering ratio between interleukin 17 producing and regulatory natural killer T cells

Mesenchymal stem cells (MSCs) are, due to immunomodulatory characteristics, considered as novel agents in the treatment of immune‐mediated acute liver failure. Although it is known that MSCs can regulate activation of T lymphocytes, their capacity to modulate function of neutrophils and natural killer T (NKT) cells, major interleukin (IL) 17–producing cells in acute liver injury, is still unknown. By using 2 well‐established murine models of neutrophil and NKT cell–mediated acute liver failure (induced by carbon tetrachloride and α‐galactoceramide), we investigated molecular and cellular mechanisms involved in MSC‐mediated modulation of IL17 signaling during acute liver injury. Single intravenous injection of MSCs attenuate acute hepatitis and hepatotoxicity of NKT cells in a paracrine, indoleamine 2,3‐dioxygenase (IDO)–dependent manner. Decreased levels of inflammatory IL17 and increased levels of immunosuppressive IL10 in serum, reduced number of interleukin 17–producing natural killer T (NKT17) cells, and increased presence of forkhead box P3 + IL10–producing natural killer T regulatory cells (NKTregs) were noticed in the injured livers of MSC‐treated mice. MSCs did not significantly alter the total number of IL17‐producing neutrophils, CD4+, and CD8 + T lymphocytes in the injured livers. Injection of mesenchymal stem cell–conditioned medium (MSC‐CM) resulted with an increased NKTreg/NKT17 ratio in the liver and attenuated hepatitis in vivo and significantly reduced hepatotoxicity of NKT cells in vitro. This phenomenon was completely abrogated in the presence of IDO inhibitor, 1‐methyltryptophan. In conclusion, the capacity of MSCs to alter NKT17/NKTreg ratio and suppress hepatotoxicity of NKT cells in an IDO‐dependent manner may be used as a new therapeutic approach in IL17‐driven liver inflammation. Liver Transplantation 23 1040–1050 2017 AASLD.

Potential dual immunomodulatory role of VEGF in ulcerative colitis and colorectal carcinoma.

Objective. Progression from ulcerative colitis (UC) toward colorectal carcinoma (CRC) is multistep process that includes gene alterations of tumor suppressor genes, such as p53 and p16. The aim of this study was to investigate the expression patterns of p16, p53 and VEGF in affected tissue and serum levels of cytokines TNF-α, IFN-γ, IL-4, IL-6, IL-10 and IL-17 in patients with UC and CRC, respectively. Matherials and methods. Serum levels of cytokine in patients with UC (n=24) and CRC (n=75) and in a healthy group (n=37) were analyzed by ELISA. Endoscopic biopsies specimens of UC and CRC were studied by immunohistochemical staining for p16, p53 and VEGF. Results. Patients with UC with presence of extraintestinal manifestations, complications, and positive staining of p16, p53 and VEGF respectively had higher serum levels of pro-inflammatory cytokines. Higher percentage of CRC patients had positive staining of p16, p53 and VEGF. CRC patients with positive staining of VEGF had decreased systemic values of pro-inflammatory IFN-γ and increased values of immunosuppressive IL-10. Conclusions. Relatively low IL-10 in patients with severe UC is insufficient to compensate IL-6 secretion and subsequently enhanced type 1/17 immune response. In UC patients, p16 and p53 induce enhanced VEGF expression and subsequent production of pro-inflammatory TNF-α and IL-6. In CRC patients VEGF seems to have immunosuppressive role. It appears that tumor suppressor gene-VEGF axis have dual role on immune response in inflammation of UC and tumor growth and progression of CRC.

Mesenchymal stem cells attenuate liver fibrosis by suppressing Th17 cells – an experimental study

This study investigates molecular and cellular mechanisms involved in mesenchymal stem cell (MSC)‐mediated modulation of IL‐17 signaling during liver fibrosis. Mice received CCl4 (1 μl/g intraperitoneally) twice/week for 1 month. MSCs (1 × 106), or MSC‐conditioned medium (MSC‐CM), were intravenously injected 24 h after CCl4 and on every 7th day. Liver fibrosis was determined by macroscopic examination, histological analysis, Sirius red staining, and RT‐PCR. Serum levels of cytokines, indoleamine 2,3‐dioxygenase (IDO), and kynurenine were determined by ELISA. Flow cytometry was performed to identify liver‐infiltrated cells. In vitro, CD4+ T cells were stimulated and cultured with MSCs. 1‐methyltryptophan was used for inhibition of IDO. MSCs significantly attenuated CCl4‐induced liver fibrosis by decreasing serum levels of inflammatory IL‐17, increasing immunosuppressive IL‐10, IDO, and kynurenine, reducing number of IL‐17 producing Th17 cells, and increasing percentage of CD4+IL‐10+ T cells. Injection of MSC‐CM resulted with attenuated fibrosis accompanied with the reduced number of Th17 cells in the liver and decreased serum levels of IL‐17. MSC‐CM promoted expansion of CD4+FoxP3+IL‐10+ T regulatory cells and suppressed proliferation of Th17 cells. This phenomenon was completely abrogated in the presence of IDO inhibitor. MSCs, in IDO‐dependent manner, suppress liver Th17 cells which lead to the attenuation of liver fibrosis.

Stem Cells and Labeling for Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition that usually results in sudden and long-lasting locomotor and sensory neuron degeneration below the lesion site. During the last two decades, the search for new therapies has been revolutionized with the improved knowledge of stem cell (SC) biology. SCs therapy offers several attractive strategies for spinal cord repair. The transplantation of SCs promotes remyelination, neurite outgrowth and axonal elongation, and activates resident or transplanted progenitor cells across the lesion cavity. However, optimized growth and differentiation protocols along with reliable safety assays should be established prior to the clinical application of SCs. Additionally, the ideal method of SCs labeling for efficient cell tracking after SCI remains a challenging issue that requires further investigation. This review summarizes the current findings on the SCs-based therapeutic strategies, and compares different SCs labeling approaches for SCI.

Mesenchymal Stem Cells Attenuate Cisplatin-Induced Nephrotoxicity in iNOS-Dependent Manner

Mesenchymal stem cells (MSCs) are, due to their immunomodulatory characteristics, utilized in therapy of immune-mediated diseases. We used murine model of cisplatin nephrotoxicity to explore the effects of MSCs on immune cells involved in the pathogenesis of this disease. Intraperitoneal application of MSCs significantly attenuated cisplatin nephrotoxicity, decreased inflammatory cytokines TNF-α and IL-17, and increased anti-inflammatory IL-10, IL-6, nitric oxide (NO), and kynurenine in sera of cisplatin-treated mice. MSC treatment significantly attenuated influx of leukocytes, macrophages, dendritic cells (DCs), neutrophils, CD4+ T helper (Th), and CD8+ cytotoxic T lymphocytes (CTLs) in damaged kidneys and attenuated the capacity of renal-infiltrated DCs, CD4+ Th, and CD8+ CTLs to produce TNF-α and IL-17. Similar effects were observed after intraperitoneal injection of MSC-conditioned medium (MSC-CM) indicating that MSCs exert their beneficial effects in paracrine manner. Inhibition of inducible nitric oxide synthase (iNOS) in MSC-CM resulted with increased number of TNF-α-producing DCs and IL-17-producing CTLs, decreased number of IL-10-producing tolerogenic DCs and regulatory CD4+FoxP3+ T cells, and completely diminished renoprotective effects of MSC-CM. In conclusion, MSCs, in iNOS-dependent manner, attenuated inflammation in cisplatin nephrotoxicity by reducing the influx and capacity of immune cells, particularly DCs and T lymphocytes, to produce inflammatory cytokines.

Mesenchymal Stem Cell-Dependent Modulation of Liver Diseases

Acute liver failure and cirrhosis display sequential and overlapping severe pathogenic processes that include inflammation, hepatocyte necrosis, and fibrosis, carrying a high mortality rate. Mesenchymal stem cells (MSCs) are a heterogeneous subset of stromal stem cells with immunonodulatory characteristics. MSCs are considered to act through multiple mechanisms to coordinate a dynamic, integrated response to liver inflammation and fibrosis, which prevents the progressive distortion of hepatic architecture. Accordingly, MSCs as well as their products have been investigated as a novel therapeutic approach for the treatment of inflammatory and fibrotic liver diseases. In this review, we highlight the current findings on the MSC-based modulation of liver inflammation and fibrosis, and the possible use of MSCs in the therapy of immune-mediated liver pathology. We briefly describe the cellular and molecular mechanisms involved in MSC-dependent modulation of cytokine production, phenotype and function of liver infiltrated inflammatory cells and compare effects of engrafted MSCs versus MSC-generated conditioned medium (MSC-CM) in the therapy of acute liver injury. In order to elucidate therapeutic potential of MSCs and their products in modulation of chronic liver inflammation and fibrosis, we present the current findings regarding pathogenic role of immune cells in liver fibrosis and describe mechanisms involved in MSC-dependent modulation of chronic liver inflammation with the brief overview of on-going and already published clinical trials that used MSCs for the treatment of immune mediated chronic liver diseases. The accumulating evidence shows that MSCs had a significant beneficial effect in the treatment of immune-mediated liver diseases.

Murine Cytomegalovirus Infection Induces Susceptibility to EAE in Resistant BALB/c Mice

In contrast to C57BL/6 mice, BALB/c mice are relatively resistant to the induction of experimental autoimmune encephalomyelitis (EAE) after challenge with MOG35–55 peptide. Here, we provide the first evidence that infection with murine cytomegalovirus (MCMV) in adulthood abrogates this resistance. Infected BALB/c mice developed clinical and histological signs similar to those seen in susceptible C57BL/6 mice. In addition to CD4+ cells, large proportion of cells in the infiltrate of diseased BALB/c mice was CD8+, similar with findings in multiple sclerosis. CD8+ cells that responded to ex vivo restimulation with MOG35–55 were not specific for viral epitopes pp89 and m164. MCMV infection favors proinflammatory type of dendritic cells (CD86+CD40+CD11c+) in the peripheral lymph organs, M1 type of microglia in central nervous system, and increases development of Th1/Th17 encephalitogenic cells. This study indicates that MCMV may enhance autoimmune neuropathology and abrogate inherent resistance to EAE in mouse strain by enhancing proinflammatory phenotype of antigen-presenting cells, Th1/Th17, and CD8 response to MOG35–55.

Deletion of Galectin-3 Enhances Xenobiotic Induced Murine Primary Biliary Cholangitis by Facilitating Apoptosis of BECs and Release of Autoantigens

Galectin-3 (Gal-3) is a carbohydrate binding lectin, with multiple roles in inflammatory diseases and autoimmunity including its antiapoptotic effect on epithelial cells. In particular, increased expression of Gal-3 in epithelial cells is protective from apoptosis. Based on the thesis that apoptosis of biliary epithelial cells (BECs) is critical to the pathogenesis of Primary Biliary Cholangitis (PBC), we have analyzed the role of Gal-3 in the murine model of autoimmune cholangitis. We took advantage of Gal-3 knockout mice and immunized them with a mimotope of the major mitochondrial autoantigen of PBC, 2-octynoic acid (2-OA) coupled to BSA (2OA-BSA) and evaluated the natural history of subsequent disease, compared to control wild-type mice, by measuring levels of antibodies to PDC-E2, immunohistology of liver, and expression of Gal-3. We report herein that deletion of Gal-3 significantly exacerbates autoimmune cholangitis in these mice. This is manifested by increased periportal infiltrations, bile duct damage, granulomas and fibrosis. Interestingly, the BECs of Gal-3 knockout mice had a higher response to apoptotic stimuli and there were more pro-inflammatory lymphocytes and dendritic cells (DCs) in the livers of Gal-3 knockout mice. In conclusion, Gal-3 plays a protective role in the pathways that lead to the inflammatory destruction of biliary epithelial cells.

Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes in the Treatment of Eye Diseases

Mesenchymal stem cells (MSCs) were, due to their immunomodulatory and pro-angiogenic characteristics, extensively explored as new therapeutic agents in cell-based therapy of uveitis, glaucoma, retinal and ocular surface diseases.Since it was recently revealed that exosomes play an important role in biological functions of MSCs, herewith we summarized current knowledge about the morphology, structure, phenotype and functional characteristics of MSC-derived exosomes emphasizing their therapeutic potential in the treatment of eye diseases.MSC-derived exosomes were as efficient as transplanted MSCs in limiting the extent of eye injury and inflammation. Immediately after intravitreal injection, MSC-derived exosomes, due to nano-dimension, diffused rapidly throughout the retina and significantly attenuated retinal damage and inflammation. MSC-derived exosomes successfully delivered trophic and immunomodulatory factors to the inner retina and efficiently promoted survival and neuritogenesis of injured retinal ganglion cells. MSC-derived exosomes efficiently suppressed migration of inflammatory cells, attenuated detrimental Th1 and Th17 cell-driven immune response and ameliorated experimental autoimmune uveitis. MSC-derived exosomes were able to fuse with the lysosomes within corneal cells, enabling delivering of MSC-derived active β-glucuronidase and consequent catabolism of accumulated glycosaminoglycans, indicating their therapeutic potential in the treatment of Mucopolysaccharidosis VII (Sly Syndrome). Importantly, beneficent effects were noticed only in animals that received MSC-derived exosomes and were not seen after therapy with fibroblasts-derived exosomes confirming specific therapeutic potential of MSCs and their products in the treatment of eye diseases.In conclusion, MSC-derived exosomes represent potentially new therapeutic agents in the therapy of degenerative and inflammatory ocular diseases.

Fecal Galectin-3: A New Promising Biomarker for Severity and Progression of Colorectal Carcinoma

Background and Objectives The aim of the study was to determine systemic and fecal values of galectin-3 and pro- and anti-inflammatory cytokines in patients with CRC and the relationship with clinicopathological aspects. Methods Concentrations of galectin-3, TNF-α, TGF-β, IL-10, and IL-1β were analyzed in samples of blood and stool of 60 patients with CRC. Results Systemic concentration of TNF-α was significantly lower in patients with severe diseases (advanced TNM stage, nuclear grade, and poor histological differentiation) as in patients with more progressive CRC (lymph and blood vessel invasion, presence of metastasis). Fecal values of anti-inflammatory cytokines TGF-β and IL-10 were increased in patients with severe stadium of CRC. Fecal concentration of Gal-3 was enhanced in CRC patients with higher nuclear grade, poor tumor tissue differentiation, advanced TNM stage, and metastatic disease. Gal-3/TNF-α ratio in sera and feces had a higher trend in patients with severe and advanced diseases. Positive correlation between fecal Gal-3 and disease severity, tumor progression, and biomarkers AFP and CEA, respectively, was also observed. Conclusions Predomination of Gal-3 in patients with advanced diseases may implicate on its role in limiting ongoing proinflammatory processes. The fecal values of Gal-3 can be used as a valuable marker for CRC severity and progression.