Eliska Javorkova

Mesenchymal Stem Cells, Nanofiber Scaffolds and Ocular Surface Reconstruction

Ocular surface defects represent one of the most common causes of impaired vision or even blindness. For treatment, keratoplasty represents the first choice. However, if corneal defects are more extensive and associated with a limbal stem cell (LSC) deficiency, corneal transplantation is not a sufficient therapeutic procedure and only viable approach to treatment is the transplantation of LSCs. When the LSC deficiency is a bilateral disorder, autologous LSCs are not available. The use of allogeneic LSCs requires strong immunosuppression, which leads to side-effects, and the treatment is not always effective. The alternative and perspective approach to the treatment of severe ocular surface injuries and LSC deficiency is offered by the transplantation of autologous mesenchymal stem cells (MSCs). These cells can be obtained from the bone marrow or adipose tissue of the particular patient, grow well in vitro and can be transferred, using an appropriate scaffold, onto the damaged ocular surface. Here they exert beneficial effects by possible direct differentiation into corneal epithelial cells, by immunomodulatory effects and by the production of numerous trophic and growth factors. Recent experiments utilizing the therapeutic properties of MSCs in animal models with a mechanically or chemically injured ocular surface have yielded promising results and demonstrated significant corneal regeneration, improved corneal transparency and a rapid healing process associated with the restoration of vision. The use of autologous MSCs thus represents a promising therapeutic approach and offers hope for patients with severe ocular surface injuries and LSC deficiency.

Modulation of the early inflammatory microenvironment in the alkali-burned eye by systemically administered interferon-γ-treated mesenchymal stromal cells.

The aim of this study was to investigate the effects of systemically administered bone-marrow-derived mesenchymal stromal cells (MSCs) on the early acute phase of inflammation in the alkali-burned eye. Mice with damaged eyes were either untreated or treated 24 h after the injury with an intravenous administration of fluorescent-dye-labeled MSCs that were unstimulated or pretreated with interleukin-1α (IL-1α), transforming growth factor-β (TGF-β), or interferon-γ (IFN-γ). Analysis of cell suspensions prepared from the eyes of treated mice on day 3 after the alkali burn revealed that MSCs specifically migrated to the damaged eye and that the number of labeled MSCs was more than 30-times higher in damaged eyes compared with control eyes. The study of the composition of the leukocyte populations within the damaged eyes showed that all types of tested MSCs slightly decreased the number of infiltrating lymphoid and myeloid cells, but only MSCs pretreated with IFN-γ significantly decreased the percentage of eye-infiltrating cells with a more profound effect on myeloid cells. Determining cytokine and NO production in the damaged eyes confirmed that the most effective immunomodulation was achieved with MSCs pretreated with IFN-γ, which significantly decreased the levels of the proinflammatory molecules IL-1α, IL-6, and NO. Taken together, the results show that systemically administered MSCs specifically migrate to the damaged eye and that IFN-γ-pretreated MSCs are superior in inhibiting the acute phase of inflammation, decreasing leukocyte infiltration, and attenuating the early inflammatory environment.

Distinct cytokines balance the development of regulatory T cells and interleukin-10-producing regulatory B cells

Regulatory T cells have been well described and the factors regulating their development and function have been identified. Recently, a growing body of evidence has documented the existence of interleukin‐10 (IL‐10) ‐producing B cells, which are called regulatory B10 cells. These cells attenuate autoimmune, inflammatory and transplantation reactions, and the main mechanism of their inhibitory action is the production of IL‐10. We show that the production of IL‐10 by lipopolysaccharide‐stimulated B cells is significantly enhanced by IL‐12 and interferon‐γ and negatively regulated by IL‐21 and transforming growth factor‐β. In addition, exogenous IL‐10 also inhibits B‐cell proliferation and the expression of the IL‐10 gene in lipopolysaccharide‐stimulated B cells. The negative autoregulation of IL‐10 production is supported by the observation that the inclusion of anti‐IL‐10 receptor monoclonal antibody enhances IL‐10 production and the proliferation of activated B cells. The effects of cytokines on IL‐10 production by B10 cells did not correlate with their effects on B‐cell proliferation or on IL‐10 production by T cells or macrophages. The cytokine‐induced changes in IL‐10 production occurred on the level of IL‐10 gene expression, as confirmed by increased or decreased IL‐10 mRNA expression in the presence of a particular cytokine. The regulatory cytokines modulate the number of IL‐10‐producing cells rather than augmenting or decreasing the secretion of IL‐10 on a single‐cell level. Altogether these data show that the production of IL‐10 by B cells is under the strict regulatory control of cytokines and that individual cytokines differentially regulate the development and activity of regulatory T cells and IL‐10‐producing regulatory B cells.

Suppression of IL-10 production by activated B cells via a cell contact-dependent cyclooxygenase-2 pathway upregulated in IFN-γ-treated mesenchymal stem cells.

The immunoregulatory properties of mesenchymal stem cells (MSCs) have been well documented in various models in vitro and in vivo. Furthermore, a population of regulatory B cells (Bregs) that produce relatively high concentrations of IL-10 has been recently described. To study the relationship between MSCs and Bregs, we analyzed the effects of MSCs on IL-10 production by lipopolysaccharide (LPS)-activated mouse B cells. The production of IL-10 by B cells remained preserved in the presence of MSCs and was even significantly enhanced by IFN-γ. However, the production of IL-10 was strongly suppressed in cultures containing MSCs and IFN-γ. Preincubation of MSCs, but not of B cells, with IFN-γ induced the suppression of IL-10 secretion in cultures containing MSCs and B cells. The supernatants from IFN-γ-treated MSCs had no inhibitory effect, and the suppression of IL-10 production was abrogated if the MSCs and B cells were separated in a transwell system. Analysis of the gene expression of IFN-γ- or IFN-γ and LPS-treated MSCs revealed a strong upregulation of genes for indoleamine-2,3-dioxygenase (IDO), cyclooxygenase-2 (Cox-2) and programmed cell death-ligand 1 (PD-L1). While the inhibition of IDO activity or the inclusion of the neutralization monoclonal antibody anti-PD-L1 did not abrogate the suppression, indomethacin, an inhibitor of Cox-2, completely inhibited the MSC-mediated suppression of IL-10 production. Accordingly, the production of IL-10 by B cells was inhibited by exogenous prostaglandin E2. The results thus suggest that IFN-γ-treated MSCs strongly inhibit IL-10 production by activated B cells by a mechanism requiring cell contact and involving the Cox-2 pathway.

The Favorable Effect of Mesenchymal Stem Cell Treatment on the Antioxidant Protective Mechanism in the Corneal Epithelium and Renewal of Corneal Optical Properties Changed after Alkali Burns

The aim of this study was to examine whether mesenchymal stem cells (MSCs) and/or corneal limbal epithelial stem cells (LSCs) influence restoration of an antioxidant protective mechanism in the corneal epithelium and renewal of corneal optical properties changed after alkali burns. The injured rabbit corneas (with 0.25 N NaOH) were untreated or treated with nanofiber scaffolds free of stem cells, with nanofiber scaffolds seeded with bone marrow MSCs (BM-MSCs), with adipose tissue MSCs (Ad-MSCs), or with LSCs. On day 15 following the injury, after BM-MSCs or LSCs nanofiber treatment (less after Ad-MSCs treatment) the expression of antioxidant enzymes was restored in the regenerated corneal epithelium and the expressions of matrix metalloproteinase 9 (MMP9), inducible nitric oxide synthase (iNOS), α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), and vascular endothelial factor (VEGF) were low. The central corneal thickness (taken as an index of corneal hydration) increased after the injury and returned to levels before the injury. In injured untreated corneas the epithelium was absent and numerous cells revealed the expressions of iNOS, MMP9, α-SMA, TGF-β1, and VEGF. In conclusion, stem cell treatment accelerated regeneration of the corneal epithelium, restored the antioxidant protective mechanism, and renewed corneal optical properties.

Mesenchymal Stem Cells Attenuate the Adverse Effects of Immunosuppressive Drugs on Distinct T Cell Subopulations

Immunosuppressive drugs are widely used to treat undesirable immune reaction, however their clinical use is often limited by harmful side effects. The combined application of immunosuppressive agents with mesenchymal stem cells (MSCs) offers a promising alternative approach that enables the reduction of immunosuppressive agent doses and simultaneously maintains or improves the outcome of therapy. The present study aimed to determinate the effects of immunosuppressants on individual T cell subpopulations and to investigate the efficacy of MSC-based treatment combined with immunosuppressive drugs. We tested the effect of five widely used immunosuppressants with different action mechanisms: cyclosporine A, mycophenolate mofetil, rapamycin, and two glucocorticoids - prednisone and dexamethasone in combination with MSCs on mouse CD4+ and CD8+ lymphocyte viability and activation, Th17 (RORγt+), Th1 (T-bet+), Th2 (GATA-3+) and Treg (Foxp3+) cell proportion and on the production of corresponding key cytokines (IL-17, IFNγ, IL-4 and IL-10). We showed that MSCs modulate the actions of immunosuppressants and in combination with immunosuppressive drugs display distinct effect on cell activation and balance among different T lymphocytes subpopulations and exert a suppressive effect on proinflammatory T cell subsets while promoting the functions of anti-inflammatory Treg lymphocytes. The results indicated that MSC-based therapy could be a powerful strategy to attenuate the negative effects of immunosuppressive drugs on the immune system.

Targeted neural differentiation of murine mesenchymal stem cells by a protocol simulating the inflammatory site of neural injury.

Damaged neural tissue is regenerated by neural stem cells (NSCs), which represent a rare and difficult‐to‐culture cell population. Therefore, alternative sources of stem cells are being tested to replace a shortage of NSCs. Here we show that mouse adipose tissue‐derived mesenchymal stem cells (MSCs) can be effectively differentiated into cells expressing neuronal cell markers. The differentiation protocol, simulating the inflammatory site of neural injury, involved brain tissue extract, fibroblast growth factor, epidermal growth factor, supernatant from activated splenocytes and electrical stimulation under physiological conditions. MSCs differentiated using this protocol displayed neuronal cell morphology and expressed genes for neuronal cell markers, such as neurofilament light (Nf‐L), medium (Nf‐M) and heavy (Nf‐H) polypeptides, synaptophysin (SYP), neural cell adhesion molecule (NCAM), glutamic acid decarboxylase (GAD), neuron‐specific nuclear protein (NeuN), βIII‐tubulin (Tubb3) and microtubule‐associated protein 2 (Mtap2), which are absent (Nf‐L, Nf‐H, SYP, GAD, NeuN and Mtap2) or only slightly expressed (NCAM, Tubb3 and Nf‐M) in undifferentiated cells. The differentiation was further enhanced when the cells were cultured on nanofibre scaffolds. The neural differentiation of MSCs, which was detected at the level of gene expression, was confirmed by positive immunostaining for Nf‐L protein. The results thus show that the simulation of conditions in an injured neural tissue and inflammatory environment, supplemented with electrical stimulation under physiological conditions and cultivation of cells on a three‐dimensional (3D) nanofibre scaffold, form an effective protocol for the differentiation of MSCs into cells with neuronal markers. Copyright

Distinct Immunoregulatory Mechanisms in Mesenchymal Stem Cells: Role of the Cytokine Environment.

Mesenchymal stem cells (MSCs) represent a population of cells which have the ability to regulate reactivity of T and B lymphocytes by multiple mechanisms. The immunoregulatory activities of MSCs are strictly influenced by the cytokine environment. Here we show that two functionally distinct cytokines, interleukin-4 (IL-4) and interferon-γ (IFN-γ), significantly potentiate the ability of MSCs to inhibit IL-10 production by activated regulatory B cells (Bregs). However, MSCs in the presence of IL-4 or IFN-γ inhibit the IL-10 production by different mechanisms. Preincubation of MSCs with IFN-γ led to the suppression, but pretreatment with IL-4 of neither MSCs nor B cells resulted in the suppression of IL-10 production. The search for candidate regulatory molecules expressed in cytokine-treated MSCs revealed different patterns of the gene expression. Pretreatment of MSCs with IFN-γ, but not with IL-4, induced expression of indoleamine-2,3-dioxygenase, cyclooxygenase-2 and programmed cell death-ligand 1. To identify the molecule(s) responsible for the suppression of IL-10 production, we used specific inhibitors of the putative regulatory molecules. We found that indomethacine, an inhibitor of cyclooxygenase-2 (Cox-2) activity, completely abrogated the inhibition of IL-10 production in cultures containing MSCs and IFN-γ, but had no effect on the suppression in cell cultures containing MSCs and IL-4. The results show that MSCs can inhibit the response of B cells to one stimulus by different mechanisms in dependence on the cytokine environment and thus support the idea of the complexity of immunoregulatory action of MSCs.

Up-regulation of μ-, δ- and κ-opioid receptors in concanavalin A-stimulated rat spleen lymphocytes

Regulation of μ-, δ- and κ-opioid receptor protein level in spleen lymphocytes when stimulated by mitogen is not known. To answer the question whether these cells do express opioid receptor (OR) proteins, primary, fresh rat spleen lymphocytes were prepared and stimulated for 48 h with mitogenic dose of Con A. The unstimulated lymphocytes did not express μ- and δ-OR proteins in detectable amounts, however, stimulation with Con A resulted in appearance of clearly detectable immunoblot signals of both μ-OR and δ-OR. κ-OR were detected already in primary cells and increased 2.4-fold in Con A-stimulated cells. These results were supported by data obtained by flow cytometry analysis indicating a dramatic increase in number of μ-, δ- and κ-OR expressing cells after mitogen stimulation. The newly synthesized μ-, δ- and κ-OR in Con A-stimulated spleen lymphocytes were present in the cells interior and not functionally mature, at least in terms of their ability to enhance activity of trimeric G proteins determined by three different protocols of agonist-stimulated, high-affinity [35S]GTPγS binding assay. The up-regulation of μ-, δ- and κ-OR was associated with specific decrease of their cognate trimeric G proteins, Gi1α/Gi2α; the other Gα and Gβ subunits were unchanged. The level of β-arrestin-1/2 was also decreased in Con A-stimulated splenocytes. We conclude that up-regulation of OR expression level in spleen lymphocytes by Con A proceeds in conjunction with down-regulation of their intracellular signaling partners, Gi1α/Gi2α proteins and β-arrestin-1/2. These regulatory proteins are expressed in high amounts already in unstimulated cells and decreased by mitogen stimulation.

The effect of clinically relevant doses of immunosuppressive drugs on human mesenchymal stem cells

Immunosuppressive drugs are used to suppress graft rejection after transplantation and for the treatment of various diseases. The main limitations of their use in clinical settings are severe side effects, therefore alternative approaches are desirable. In this respect, mesenchymal stem cells (MSCs) possess a regenerative and immunomodulatory capacity that has generated considerable interest for their use in cell-based therapy. Currently, MSCs are tested in many clinical trials, including the treatment of diseases which require simultaneous immunosuppressive treatment. Since the molecular targets of immunosuppressive drugs are also present in MSCs, we investigated whether immunosuppressive drugs interact with the activity of MSCs. Human MSCs isolated from the bone marrow (BM) or adipose tissue (AT) were cultured in the presence of clinical doses of five widely used immunosuppressive drugs (cyclosporine A, mycophenolate mofetil, rapamycin, prednisone and dexamethasone), and the influence of these drugs on several factors related to the immunosuppressive properties of MSCs, including the expression of immunomodulatory enzymes, various growth factors, cytokines, chemokines, adhesion molecules and proapoptotic ligands, was assessed. Glucocorticoids, especially dexamethasone, showed the most prominent effects on both types of MSCs and suppressed the expression of the majority of the factors that were tested. A significant increase of hepatocyte growth factor production in AT-MSCs and of indoleamine 2,3-dioxygenase expression in both types of MSCs were the only exceptions. In conclusion, clinically relevant doses of inhibitors of calcineurin, mTOR and IMPDH and glucocorticoids interfere with MSC functions, but do not restrain their immunosuppressive properties. These findings should be taken into account before preparing immunosuppressive strategies combining the use of immunosuppressive drugs and MSCs.