Human mesenchymal stromal cells attenuate graft-versus-host disease and maintain graft-versus-leukemia activity following experimental allogeneic bone marrow transplantation

Foreskin as a source of immunotherapeutic mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have well-characterized properties and thus represent an attractive cell population for use in several therapeutic applications. Due to the limitations and inconveniences associated with classical sources of MSCs, the identification and characterization of alternative sources are required for safe and efficient cell therapy. The skin tissue is currently referred to as a reservoir of cells with therapeutically relevant functions. Historically considered biological waste, foreskin (FSK) is increasingly used to provide immunotherapeutic MSCs for medicinal products. This review discusses for the first time the nature and profile of MSCs within the foreskin tissue and, in particular, their immunobiology. A better immunological characterization and understanding of foreskin-derived cells will be critical for improving MSC-based cellular strategies for immunotherapeutic applications.

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

BACKGROUND

Mesenchymal stromal cells (MSCs) have shown promising results for the treatment of refractory acute graft-versus-host disease. While safety of MSC infusion has been demonstrated, the use of cryopreserved MSCs in clinical trials has raised concerns regarding the retention of their functional activity. This has led to the recommendation by experts in the field to use freshly harvested MSCs, even though this approach is much less practical from a logistic point of view. In the present study, we revisited the impact of cryopreservation on MSC functionality and addressed the possibility that warming events on frozen cells rather than cryopreservation per se could impact MSC functionality.

METHODS

Following controlled-rate freezing to -130°C, umbilical cord-derived MSCs were left at room temperature (RT) for 2-10 min or on dry ice for 10 min, before being transferred into liquid nitrogen (LqN₂). MSCs of each group were subsequently tested (viability, functionality and cellular damage) and compared with their freshly harvested counterparts.

RESULTS

We demonstrated that freshly harvested MSCs as well as cryopreserved MSCs that were left on dry ice following step-down freezing have comparable viability, functionality and integrity. In contrast, cryopreserved MSCs that were left at RT before being transferred into LqN₂ were functionally impaired and showed cellular damage upon thawing even though they exhibited high viability.

DISCUSSION

Warming events after freezing and not cryopreservation per se significantly impair MSC functionality, indicating that cryopreserved MSCs can be an advantageous alternative to freshly harvested cells for therapeutic purposes.

The influence of macrophages on mesenchymal stromal cell therapy: passive or aggressive agents?

Mesenchymal stromal cells (MSC) have emerged as promising cell therapies for multiple conditions based on demonstrations of their potent immunomodulatory and regenerative capacities in models of inflammatory disease. Understanding the effects of MSC on T cells has dominated the majority of work carried out in this field to date; recently, however, a number of studies have shown that the therapeutic effect of MSC requires the presence of macrophages. It is timely to review the mechanisms and manner by which MSC modulate macrophage populations in order to design more effective MSC therapies and clinical studies. A complex cross-talk exists through which MSC and macrophages communicate, a communication that is not controlled exclusively by MSC. Here, we examine the evidence that suggests that MSC not only respond to inflammatory macrophages and adjust their secretome accordingly, but also that macrophages respond to encounters with MSC, creating a feedback loop which contributes to the immune regulation observed following MSC therapy. Future studies examining the effects of MSC on macrophages should consider the antagonistic role that macrophages play in this exchange.

Regulatory B cells promote graft-versus-host disease prevention and maintain graft-versus-leukemia activity following allogeneic bone marrow transplantation

Regulatory B cells (Bregs) are involved in the pathogenesis of graft-versus-host disease (GVHD). However, whether Bregs can alleviate acute GVHD without compromising graft-versus-leukemia (GVL) effects remains unclear. Here, we evaluated the role of Bregs in acute GVHD and GVL activity in both a mouse model and a clinical cohort study. In the acute GVHD mouse model, co-transplantation of Bregs prevents onset through inhibiting Th1 and Th17 differentiation and expanding regulatory T cells. In the GVL mouse model, Bregs contributed to the suppression of acute GVHD but had no adverse effect on GVL activity. In the clinical cohort study, a higher dose of Bregs in allografts was associated with a lower cumulative incidence of acute GVHD but not with increased risk of relapse. Our data demonstrate that Bregs can prevent acute GVHD and maintain GVL effects and suggest that Bregs have potential as a novel strategy for acute GVHD alleviation.

Treatment of chemically induced oral ulcer using adipose-derived mesenchymal stem cell sheet

BACKGROUND

This study investigated the effects of mesenchymal stem cell (MSC) sheet transplantation on healing of chemically induced oral ulceration in a rabbit animal model.

METHODS

Oral mucosal ulcers were induced by topical application of filter paper soaked with 70% acetic acid to the anterior gingiva and buccal mucosa of 12 New Zealand white rabbits. The animals were randomly assigned to two groups: with (treatment group, n = 6) or without (control group, n = 6) cell sheets applied to ulcers. Gross findings were sequentially evaluated, and histologic examination was performed on day 7.

RESULTS

Based on gross inspection, ulceration resolved before day 5 in the treatment group; however, in the control group, healing was incomplete on day 7. In the treatment group, the total area of the ulcer decreased significantly from day 2 to day 5 (P < 0.001) and from day 5 to day 7 (P = 0.020), whereas the area decreased significantly from day 5 to day 7 in the control group (P < 0.001). Histologic and immunofluorescence examination revealed full-thickness mucosa healing and complete basal cell coverage in the treatment group; in contrast, only partial healing was observed on day 7 in the control group.

CONCLUSIONS

Cell sheet technology using MSC can be an alternative treatment for oral ulcerations in that it can decrease healing time without invasive properties.

Cyclin-dependent kinase 5 activity is required for allogeneic T-cell responses after hematopoietic cell transplantation in mice

Molecular intermediates in T-cell activation pathways are crucial targets for the therapy and prevention of graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (allo-HCT). We recently identified an essential role for cyclin-dependent kinase 5 (Cdk5) in T-cell activation and effector function, but the contribution of Cdk5 activity to the development of GVHD has not been explored. Using an established, preclinical, murine, GVHD model, we reveal that Cdk5 activity is increased in key target organs early after allo-HCT. We then generated chimeric mice (Cdk5^+/+C or Cdk5^-/-C) using hematopoietic progenitors from either embryonic day 16.5 Cdk5^+/+ or Cdk5^-/- embryos to enable analyses of the role of Cdk5 in GVHD, as germ line Cdk5 gene deletion is embryonically lethal. The immunophenotype of adult Cdk5^-/-C mice is identical to control Cdk5^+/+C mice. However, transplantation of donor Cdk5^-/-C bone marrow and T cells dramatically reduced the severity of systemic and target organ GVHD. This phenotype is attributed to decreased T-cell migration to secondary lymphoid organs (SLOs), reduced in vivo proliferation within these organs, and fewer cytokine-producing donor T cells during GVHD development. Moreover, these defects in Cdk5^-/- T-cell function are associated with altered CCR7 signaling following ligation by CCL19, a receptor:ligand interaction critical for T-cell migration into SLOs. Although Cdk5 activity in donor T cells contributed to graft-versus-tumor effects, pharmacologic inhibition of Cdk5 preserved leukemia-free survival. Collectively, our data implicate Cdk5 in allogeneic T-cell responses after HCT and as an important new target for therapeutic intervention.

Human mesenchymal stem cells (MSCs) for treatment towards immune- and inflammation-mediated diseases: review of current clinical trials

Human mesenchymal stem cells (MSCs) are multilineage somatic progenitor/stem cells that have been shown to possess immunomodulatory properties in recent years. Initially met with much skepticism, MSC immunomodulation has now been well reproduced across tissue sources and species to be clinically relevant. This has opened up the use of these versatile cells for application as 3rd party/allogeneic use in cell replacement/tissue regeneration, as well as for immune- and inflammation-mediated disease entities. Most surprisingly, use of MSCs for in immune-/inflammation-mediated diseases appears to yield more efficacy than for regenerative medicine, since engraftment of the exogenous cell does not appear necessary. In this review, we focus on this non-traditional clinical use of a tissue-specific stem cell, and highlight important findings and trends in this exciting area of stem cell therapy.

Mesenchymal stromal cells from the foreskin: Tissue isolation, cell characterization and immunobiological properties

BACKGROUND AIMS

Because of their self-renewal capacity, multilineage potential and immunomodulatory properties, MSCs are an attractive tool for cell-based immunotherapy strategies. Foreskin, considered as a biological waste material, has been shown to be a reservoir of therapeutic cells.

METHODS

MSCs were isolated from different foreskin samples, maintained under in vitro culture and defined according to the International Society for Cellular Therapy (ISCT) criteria. We subsequently determined their main cell characteristics as well as their immunobiological properties. The following parameters were determined: (i) morphology and phenotype, (ii) proliferative and clonogenic potentials, (iii) tri-lineage differentiation ability, (iv) immunological profile, (v) immunomodulatory properties and (vi) protein and messenger RNA expression/secretion profile of immunoregulatory cytokines/factors as well as the pattern of toll-like receptors (TLRs). By using a pro-inflammatory cytokine cocktail, we also evaluated the influence of an inflammatory environment on their biology.

RESULTS

With a typical fibroblast-like morphology and an ISCT-compliant phenotype, foreskin-MSCs (FSK-MSCs) were highly proliferative and had a great clonogenic potential. They displayed multilineage capacities and interesting immunomodulatory properties. Of importance, FSK-MSCs were not immunogenetic and were further able to inhibit T-cell proliferation. We showed that several immunoregulatory cytokines and factors might be potentially involved in FSK-MSC immunomodulation with particular attention to hepatocyte growth factor and interleukin-11. Moreover, FSK-MSCs expressed several TLRs and were sensitive to the inflammatory environment by properly adjusting their profile and fate.

CONCLUSIONS

Foreskin represents a new alternative source for MSCs that is compliant with ISCT criteria. Their unique immunobiological properties allow consideration of FSK-MSCs as a valuable tolerogenic product for cell-based immunotherapy.

Remestemcel-L for the treatment of graft versus host disease

INTRODUCTION

Remestemcel-L, a third-party, off-the-shelf preparation of bone-marrow derived mesenchymal stromal cells (MSCs), has been developed for experimental use in acute graft-versus-host disease (aGvHD) and other immune-mediated conditions. Several preclinical and clinical studies have indeed suggested the potential of human mesenchymal stromal cells (MSCs) as an effective treatment for steroid-refractory aGvHD. However, an unambiguous demonstration of efficacy is still lacking. Areas covered: This review critically examines the biologic rationale supporting MSCs use in aGvHD and analyzes the results of published clinical trials in this setting, with a particular focus on the potential benefits and drawbacks of Remestemcel-L. For this purpose, a systematic literature search was performed in PubMed using the following keywords: 'mesenchymal stromal cells', 'mesenchymal progenitor cells', 'multipotent stromal cells', 'mesenchymal cells', 'MSC', 'Remestemcel-L', 'Prochymal', and 'graft-versus-host disease' or 'GvHD'. Expert commentary: Remestemcel-L represents a promising alternative to second-line immunosuppressive agents for the treatment of steroid-refractory aGvHD. Despite the safety and the favorable risk/benefit profile of this cell product, which has been demonstrated in several phase I-II studies, large and prospective randomized trials are required to confirm its efficacy in aGvHD and to define the optimal schedule of administration in terms of infusion timing, cell dose and pharmacological synergism.

Antimicrobial Properties of Mesenchymal Stem Cells: Therapeutic Potential for Cystic Fibrosis Infection, and Treatment

Cystic fibrosis (CF) is a genetic disease in which the battle between pulmonary infection and inflammation becomes the major cause of morbidity and mortality. We have previously shown that human MSCs (hMSCs) decrease inflammation and infection in the in vivo murine model of CF. The studies in this paper focus on the specificity of the hMSC antimicrobial effectiveness using Pseudomonas aeruginosa (gram negative bacteria) and Staphylococcus aureus (gram positive bacteria). Our studies show that hMSCs secrete bioactive molecules which are antimicrobial in vitro against Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumonia, impacting the rate of bacterial growth and transition into colony forming units regardless of the pathogen. Further, we show that the hMSCs have the capacity to enhance antibiotic sensitivity, improving the capacity to kill bacteria. We present data which suggests that the antimicrobial effectiveness is associated with the capacity to slow bacterial growth and the ability of the hMSCs to secrete the antimicrobial peptide LL-37. Lastly, our studies demonstrate that the tissue origin of the hMSCs (bone marrow or adipose tissue derived), the presence of functional cystic fibrosis transmembrane conductance regulator (CFTR: human, Cftr: mouse) activity, and response to effector cytokines can impact both hMSC phenotype and antimicrobial potency and efficacy. These studies demonstrate, the unique capacity of the hMSCs to manage different pathogens and the significance of their phenotype in both the antimicrobial and antibiotic enhancing activities.

Route of delivery influences biodistribution of human bone marrow-derived mesenchymal stromal cells following experimental bone marrow transplantation

Mesenchymal stromal cells (MSCs) have shown promise as treatment for graft-versus-host disease (GvHD) following allogeneic bone marrow transplantation (alloBMT). Mechanisms mediating in vivo effects of MSCs remain largely unknown, including their biodistribution following infusion. To this end, human bone-marrow derived MSCs (hMSCs) were injected via carotid artery (IA) or tail vein (TV) into allogeneic and syngeneic BMT recipient mice. Following xenogeneic transplantation, MSC biodistribution was measured by bioluminescence imaging (BLI) using hMSCs transduced with a reporter gene system containing luciferase and by scintigraphic imaging using hMSCs labeled with [^99mTc]-HMPAO. Although hMSCs initially accumulated in the lungs in both transplant groups, more cells migrated to organs in alloBMT recipient as measured by in vivo BLI and scintigraphy and confirmed by ex vivo BLI imaging, immunohistochemistry and quantitative RT-PCR. IA injection resulted in persistent whole–body hMSC distribution in alloBMT recipients, while hMSCs were rapidly cleared in the syngeneic animals within one week. In contrast, TV-injected hMSCs were mainly seen in the lungs with fewer cells traveling to other organs. Summarily, these results demonstrate the potential use of IA injection to alter hMSC biodistribution in order to more effectively deliver hMSCs to targeted tissues and microenvironments.

Human Periodontal Stem Cells Release Specialized Proresolving Mediators and Carry Immunomodulatory and Prohealing Properties Regulated by Lipoxins

The actions of human periodontal ligament stem cells (hPDLSCs) on polymorphonuclear neutrophil (PMN) apoptosis and antimicrobial functions, and the impact of lipoxin A₄ (LXA₄) on hPDLSCs were investigated. hPDLSCs significantly reduced apoptosis and stimulated microbicidal activity of human PMNs, via both cell-cell interactions and paracrine mechanisms. hPDLSCs also were found to biosynthesize proresolving lipid mediators and prostaglandins. This study also demonstrated that the LXA₄-ALX/FPR2 axis regulates regenerative functions of hPDLSCs by a novel receptor-mediated mechanism.

Unresolved inflammation and tissue destruction are underlying mechanisms of periodontitis, which is linked to dysregulated polymorphonuclear neutrophil (PMN) functions. Lipoxin A₄ (LXA₄) is a specialized proresolving lipid mediator (SPM) that dampens excessive inflammation, promotes resolution, and protects from leukocyte-mediated tissue damage. Human periodontal ligament stem cells (hPDLSCs) represent key players during tissue regeneration and may contribute to resolution of inflammation; thus, they may represent a promising tool in regenerative dentistry. In the present study, we investigated the actions of hPDLSCs on PMN apoptosis and antimicrobial functions, and determined the impact of LXA₄ on hPDLSCs. hPDLSCs significantly reduced apoptosis and stimulated microbicidal activity of human PMNs, via both cell-cell interactions and paracrine mechanisms. Lipid mediator metabololipidomics analysis demonstrated that hPDLSCs biosynthesize SPMs, including resolvin D1, D2, D5, and D6; protectin D1; maresins; and LXB₄; as well as prostaglandins D₂, E₂, and F_2α. LXA₄ significantly enhanced proliferation, migration, and wound healing capacity of hPDLSCs through the activation of its cognate receptor ALX/FPR2, expressed on hPDLSCs. Together, these results demonstrate that hPDLSCs modulate PMN functions, and provide the first evidence that stem cells generate SPM and that the LXA₄-ALX/FPR2 axis regulates regenerative functions of hPDLSCs by a novel receptor-mediated mechanism.

Significance

These findings uncovered unappreciated features of stem cells from the periodontal ligament, supporting the notion that these cells may act as master regulators of pathophysiological events through the release of mediators that promote the resolution of inflammation and bacterial killing. The study also demonstrated that it is possible to modulate important functions of periodontal stem cells using lipoxin A₄, a potent endogenous stop signal of inflammation. Thus, this study revealed an unappreciated anti-inflammatory proregenerative circuit that may be exploited to combat periodontal pathologies using resident stem cells. Moreover, the data may represent a more general template to explain the immunomodulatory functions of stem cells.

Hypodermin A, a potential agent for prevention of allogeneic acute rejection

Immunosuppressive agents play an important role in the success of organ transplantation, however the chronic toxicity of these agents is a major issue over the long-term. Hypodermin A (HA) is an enzyme secreted by the larvae of Hypoderma lineatum (Diptera: Oestridae), and has been implicated in immunosuppression in cattle. Malassagne et al. have demonstrated that HA can degrade the C3 protein, and could be used to prevent hyperacute xenogeneic rejection. We found that overexpression of HA in RAW264.7 cells induced significant secretion of prostaglandin E2 (PGE2), which mediates a variety of innate and adaptive immune responses through four E-type prostanoid (EP) receptor subtypes (EP1-4). PGE2 is useful in the management of allogeneic acute rejection. In addition, we found that induction of PGE2 expression downregulates the expression of interferon (IFN)-γ and interleukin (IL)-2, and promotes the secretion of IL-10 in vitro through the EP4 receptor. It was previously shown that activation of IL-2 and IFN-γ is involved in allograft acute rejection. IL-10 is known to prevent inflammation, and can improve allograft survival rates. We concluded that besides preventing hyperacute xenogeneic rejection, HA might also be a potential therapeutic candidate for ameliorating acute rejection during allotransplantation.

Stem Cells and Regenerative Medicine: Myth or Reality of the 21th Century

Since the 1960s and the therapeutic use of hematopoietic stem cells of bone marrow origin, there has been an increasing interest in the study of undifferentiated progenitors that have the ability to proliferate and differentiate into various tissues. Stem cells (SC) with different potency can be isolated and characterised. Despite the promise of embryonic stem cells, in many cases, adult or even fetal stem cells provide a more interesting approach for clinical applications. It is undeniable that mesenchymal stem cells (MSC) from bone marrow, adipose tissue, or Wharton's Jelly are of potential interest for clinical applications in regenerative medicine because they are easily available without ethical problems for their uses. During the last 10 years, these multipotent cells have generated considerable interest and have particularly been shown to escape to allogeneic immune response and be capable of immunomodulatory activity. These properties may be of a great interest for regenerative medicine. Different clinical applications are under study (cardiac insufficiency, atherosclerosis, stroke, bone and cartilage deterioration, diabetes, urology, liver, ophthalmology, and organ's reconstruction). This review focuses mainly on tissue and organ regeneration using SC and in particular MSC.

Intra-arterial Administration of Placenta-Derived Decidual Stromal Cells to the Superior Mesenteric Artery in the Rabbit: Distribution of Cells, Feasibility, and Safety

Selective administration of mesenchymal stromal cells to the mesenteric arteries is a potential technique to overcome pulmonary trapping and increase the density of transplanted cells in extensive mural inflammation of the intestine, such as in inflammatory bowel disease and graft-versus-host disease. We injected 5 × 10(6) (111)In-oxine-labeled human decidual stromal cells (DSCs) to the rabbit superior mesenteric artery (SMA) using clinical routine catheters guided by an angiographical system under sterile conditions. We used longitudinal single-photon emission tomography at 6 h and at 1, 2, and 5 days to assess trafficking and distribution of DSCs. We used digital subtraction angiography, computed tomography, and hematoxylin and eosin stainings to determine biodistribution of cells and to assess safety end points. We found that selective injection of human DSCs to the rabbit SMA does not result in acute embolic complications. Furthermore, we found that IV administration resulted in extensive retention of the radiolabeled DSCs in the lungs, corroborating previous studies on pulmonary trapping. In sharp contrast, selective injections to the SMA resulted in uptake distributed in the intestine supplied by the SMA and in the liver, indicating that this approach could significantly increase the fraction of injected DSCs reaching the target tissue.

Immunosuppressive mechanisms of human bone marrow derived mesenchymal stromal cells in BALB/c host graft versus host disease murine models

Background

Mesenchymal stromal cells (MSCs) are proven to have immunosuppressive functions via various mechanisms. These mechanisms were demonstrated by administering bone marrow derived human MSCs (hMSCs) to graft versus host disease (GVHD) murine models.

Methods

BALB/c host mice were irradiated prior to receiving C57BL/6 donor T cell depleted bone marrow (TCDBM) cells (negative control) and donor CD4+ T lymphocyte with (treatment group) or without hMSCs (positive control). The presence of hMSCs in target tissues and lymphoid organs was documented by using in vivo imaging and measuring the expression of EphB2 and ephrin-B2 by RTqPCR. Survival rate and GVHD score were also monitored. Tissue sections were obtained for histopathologic analysis. Flow cytometry was used to document donor T cell alloreactivity and expression of CCR5, CXCR3 and CCR7. ELISA was utilized to determine levels of proinflammatory cytokines, RANTES (CCL5) and phosphorylated STAT 5A/B. RTqPCR was performed to quantify expression of CCL3 and CXCL9. Western blotting was performed to qualitatively measure iNOS expression.

Results

Survival rate and GVHD score improved with hMSC treatment. Pathologic changes of GVHD were abrogated. Documentation of suppression of RANTES, CCL3, CXCL9, CCR5 and CXCR3 with simultaneous decrease of donor T cell alloreactivity was demonstrated 6 days after transplantation, along with reduction of levels of inflammatory cytokines, suppression of STAT 5A/B phosphorylation, increased expression of CCR7 and increased production of nitrous oxide by hMSCs. Documentation of homing of hMSCs to lymphoid organs and target tissues was also performed.

Conclusions

These mechanisms contribute to the current understanding of MSC mechanisms of immunosuppression and forms a comprehensive picture of how they exert immunosuppression in an in vivo model of immune dysregulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s40164-015-0007-0) contains supplementary material, which is available to authorized users.