Intravenous hMSCs improve myocardial infarction in mice because cells embolized in lung are activated to secrete the anti-inflammatory protein TSG-6

An inducible caspase 9 suicide gene to improve the safety of mesenchymal stromal cell therapies

Mesenchymal stromal cells (MSCs) have been infused in hundreds of patients to date, with minimal reported side effects. However, follow-up is limited and long-term side effects are unknown. Because several animal models have raised safety concerns, we sought to develop a system allowing control over the growth and survival of MSCs used therapeutically. We have previously described a suicide system based on an inducible caspase-9 (iCasp9) protein that is activated using a specific chemical inducer of dimerization (CID), analogs of which have been safely tested in a phase I study. Here, we show that MSCs can be easily transduced with this system and selected to high purity (greater than 97%) with clinical grade immunomagnetic procedures. The transduced cells maintain their basic physiology, including expression of surface antigens (such as positivity for CD73, CD90, and CD105, and negativity for hematopoietic markers) and their potential to differentiate into diverse connective tissue lineages (adipocytes, osteoblasts, and chondroblasts). Those cells and their differentiated progeny can be selectively eliminated in vitro or in vivo within 24 hours after exposure to pharmacological levels of CID, with evidence of apoptosis in more than 95% of iCasp9-positive cells. In conclusion, we have developed directed MSC killing to provide a necessary safety mechanism for therapies using progenitor cells. We believe that this approach will become of increasing value as clinical applications for MSCs develop further.

Host tissue response in stem cell therapy

Preclinical and clinical trials of stem cell therapy have been carried out for treating a broad spectrum of diseases using several types of adult stem cells. While encouraging therapeutic results have been obtained, much remains to be investigated regarding the best cell type to use, cell dosage, delivery route, long-term safety, clinical feasibility, and ultimately treatment cost. Logistic aspects of stem cell therapeutics remain an area that requires urgent attention from the medical community. Recent cardiovascular trial studies have demonstrated that growth factors and cytokines derived from the injected stem cells and host tissue appear to contribute largely to the observed therapeutic benefits, indicating that trophic actions rather than the multilineage potential (or stemness) of the administered stem cells may provide the underlying tissue healing power. However, the capacity for trophic factor production can be aberrantly downregulated as seen in human heart disease. Skeletal muscle is a dynamic tissue with an impressive ability to continuously respond to environmental stimuli. Indeed, a relation exists between active skeletal muscle and low cardiovascular risk, highlighting the critical link between the skeletal muscle and cardiovascular systems. Adding to this notion are recent studies showing that stem cells injected into skeletal muscle can rescue the failing rodent heart through activation of the muscle trophic factor network and mobilization of bone marrow multilineage progenitor cells. However, aging and disease can adversely affect the host tissue into which stem cells are injected. A better understanding of the host tissue response in stem cell therapy is necessary to advance the field and bridge the gap between preclinical and clinical findings.

Adipose stem cell treatment in mice attenuates lung and systemic injury induced by cigarette smoking

RATIONALE

Adipose-derived stem cells express multiple growth factors that inhibit endothelial cell apoptosis, and demonstrate substantial pulmonary trapping after intravascular delivery.

OBJECTIVES

We hypothesized that adipose stem cells would ameliorate chronic lung injury associated with endothelial cell apoptosis, such as that occurring in emphysema.

METHODS

Therapeutic effects of systemically delivered human or mouse adult adipose stem cells were evaluated in murine models of emphysema induced by chronic exposure to cigarette smoke or by inhibition of vascular endothelial growth factor receptors.

MEASUREMENTS AND MAIN RESULTS

Adipose stem cells were detectable in the parenchyma and large airways of lungs up to 21 days after injection. Adipose stem cell treatment was associated with reduced inflammatory infiltration in response to cigarette smoke exposure, and markedly decreased lung cell death and airspace enlargement in both models of emphysema. Remarkably, therapeutic results of adipose stem cells extended beyond lung protection by rescuing the suppressive effects of cigarette smoke on bone marrow hematopoietic progenitor cell function, and by restoring weight loss sustained by mice during cigarette smoke exposure. Pulmonary vascular protective effects of adipose stem cells were recapitulated by application of cell-free conditioned medium, which improved lung endothelial cell repair and recovery in a wound injury repair model and antagonized effects of cigarette smoke in vitro.

CONCLUSIONS

These results suggest a useful therapeutic effect of adipose stem cells on both lung and systemic injury induced by cigarette smoke, and implicate a lung vascular protective function of adipose stem cell derived paracrine factors.

Galectin-3 secreted by human umbilical cord blood-derived mesenchymal stem cells reduces amyloid-beta42 neurotoxicity in vitro

In this study, we found that expression and secretion of galectin-3 (GAL-3) were upregulated by amyloid-beta42 (Abeta42) exposure in human umbilical cord blood-derived mesenchymal stem cell (hUCB-MSC) without cell death. Abeta42-exposed rat primary cortical neuronal cells co-treated with recombinant GAL-3 were protected from neuronal death in a dose-dependent manner. hUCB-MSCs were cocultured with Abeta42-exposed rat primary neuronal cells or the neuroblastoma cell line, SH-SY5Y in a Transwell chamber. Coculture of hUCB-MSCs reduced cell death of Abeta42-exposed neurons and SH-SY5Y cells. This neuroprotective effect of hUCB-MSCs was reduced significantly by GAL-3 siRNA. These data suggested that hUCB-MSC-derived GAL-3 is a survival factor against Abeta42 neurotoxicity.

Aggregation of human mesenchymal stromal cells (MSCs) into 3D spheroids enhances their antiinflammatory properties

Previous reports suggested that culture as 3D aggregates or as spheroids can increase the therapeutic potential of the adult stem/progenitor cells referred to as mesenchymal stem cells or multipotent mesenchymal stromal cells (MSCs). Here we used a hanging drop protocol to prepare human MSCs (hMSCs) as spheroids that maximally expressed TNFalpha stimulated gene/protein 6 (TSG-6), the antiinflammatory protein that was expressed at high levels by hMSCs trapped in the lung after i.v. infusion and that largely explained the beneficial effects of hMSCs in mice with myocardial infarcts. The properties of spheroid hMSCs were found to depend critically on the culture conditions. Under optimal conditions for expression of TSG-6, the hMSCs also expressed high levels of stanniocalcin-1, a protein with both antiinflammatory and antiapoptotic properties. In addition, they expressed high levels of three anticancer proteins: IL-24, TNFalpha-related apoptosis inducing ligand, and CD82. The spheroid hMSCs were more effective than hMSCs from adherent monolayer cultures in suppressing inflammatory responses in a coculture system with LPS-activated macrophages and in a mouse model for peritonitis. In addition, the spheroid hMSCs were about one-fourth the volume of hMSCs from adherent cultures. Apparently as a result, larger numbers of the cells trafficked through the lung after i.v. infusion and were recovered in spleen, liver, kidney, and heart. The data suggest that spheroid hMSCs may be more effective than hMSCs from adherent cultures in therapies for diseases characterized by sterile tissue injury and unresolved inflammation and for some cancers that are sensitive to antiinflammatory agents.

Cardiac cell therapy: lessons from clinical trials

Cardiac cell therapy has now been in clinical use since 10 years. Both autologous skeletal myoblasts and bone marrow-derived different cell subsets (mononuclear cells, hematopoietic progenitors, mesenchymal stem cells) have been investigated in different settings (acute myocardial infarction, refractory angina and chronic heart failure). Despite the huge variability in cell processing techniques, dosing, timing of delivery and route for cell transfer, some lessons can yet be drawn, primarily from randomized controlled trials and summarized as follows: Techniques used for cell preparation are reasonably well controlled although better standardization and improvement in scale-up procedures remain necessary; cell therapy is overall safe, with the caveat of ventricular arrhythmias which still require careful scrutinization; the cell type needs to be tailored to the primary clinical indication, whereas the paracrine effects of bone marrow cells may be therapeutically efficacious for limitation of remodelling or relief of angina, only cells endowed with a true cardiomyogenic differentiation potential are likely to effect regeneration of chronic scars; autologous cells are primarily limited by their variable and unpredictable functionality, thereby calling attention to banked, consistent and readily available allogeneic cell products provided the immunological issues inherent in their use can be satisfactorily addressed; regardless of the cell type, a meaningful and sustained therapeutic benefit is unlikely to occur until cell transfer and survival techniques are improved to allow greater engraftment rates; and trial end points probably need to be reassessed to focus on mechanistic issues or hard end points depending on whether new or already extensively used cells are investigated. Hopefully, these lessons may serve as a building block whose incorporation in the design of second-generation trials will help making them more clinically successful. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

Effect of myogenic stem cells on contractile properties of the repaired and unrepaired transected external anal sphincter in an animal model

OBJECTIVE

To estimate the effect of myogenic stem cells on contractile function of the external anal sphincter after transection with or without repair in an animal model.

METHODS

One hundred twenty virginal female rats were randomly assigned to repair (n=60) or no repair (n=60) after anal sphincter transection. Animals were further divided into two groups: 40-microliter injection at the transection site with either phosphate-buffered solution (control) or myogenic stem cells (3.2x10 cells). Animals were killed at 7, 21, or 90 days, and the anal sphincter complex dissected and analyzed for contractile function.

RESULTS

Contractile function of the external anal sphincter was severely impaired 7 days after sphincter transection with or without repair. Twitch tension, maximal tetanic contraction, and maximal contractile force in response to electrical field stimulation improved significantly with time after sphincter repair. Injection of myogenic stem cells in the anal sphincter at the time of repair resulted in superior contractile function at both 7 days and 90 days compared with controls. Interestingly, contractile function of the nonrepaired external anal sphincter did not improve with time with or without myogenic stem cells. Indicators of denervation (fatigue and twitch or tetany ratios) did not change among groups.

CONCLUSION

In this animal model, injection of myogenic stem cells at the time of external anal sphincter repair resulted in enhanced contractile function at 90 days compared with repair alone. Without repair, function of the external anal sphincter was not improved by stem cell therapy at any time point. These results suggest that addition of myogenic stem cells improves both acute and long-term function of the external anal sphincter after mechanical injury.

Targeting improves MSC treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is an inflammatory autoimmune disease characterized by T-cell infiltration to the colon. Mesenchymal stem cells (MSCs) have the potential to rescue IBD owing to their immunosuppressive capabilities and clinical studies have shown positive influence on intestinal graft versus host disease. We demonstrate here a new method to coat MSCs with antibodies against addressins to enhance their delivery to the colon and thereby increase the therapeutic effectiveness. Bioluminescence imaging (BLI) demonstrated that vascular cell adhesion molecule antibody (Ab)-coated MSCs (Ab(VCAM-1)- MSCs) had the highest delivery efficiency to inflamed mesenteric lymph node (MLN) and colon compared to untreated MSCs, Ab(isotype)-MSCs, and Ab(MAdCAM)-MSCs. Therapeutically, when mice with IBD were injected with addressin Ab-coated MSCs, they showed dramatically improved survival rates, higher IBD therapeutic scores, and significantly improved body weight gain compared to mice injected with MSCs only, isotype Ab, free Ab plus MSCs, or vehicle-only controls. These data demonstrate that anti-addressin Ab coating on MSC increased cell delivery to inflamed colon and increased the efficacy of MSC treatment of IBD. This is the first study showing an increased therapeutic efficacy when stem cells are first coated with antibodies specifically target them to inflamed sites.

Platelet-lysate-expanded mesenchymal stromal cells as a salvage therapy for severe resistant graft-versus-host disease in a pediatric population

Despite advances in graft-versus-host-disease (GVHD) treatment, it is estimated that overall survival (OS) at 2 years for hematopoietic cell transplantation (HCT) recipients who experience steroid-resistant GVHD is 10%. Among recent therapeutic approaches for GVHD treatment, mesenchymal stromal cells (MSCs) hold a key position. We describe a multicenter experience of 11 pediatric patients diagnosed with acute or chronic GVHD (aGVHD, cGVHD) treated for compassionate use with GMP-grade unrelated HLA-disparate donors' bone marrow-derived MSCs, expanded in platelet-lysate (PL)-containing medium. Eleven patients (aged 4-15 years) received intravenous (i.v.) MSCs for aGVHD or cGVHD, which was resistant to multiple lines of immunosuppression. The median dose was 1.2 x 10(6)/kg (range: 0.7-3.7 x 10(6)/kg). No acute side effects were observed, and no late side effects were reported at a median follow-up of 8 months (range: 4-18 months). Overall response was obtained in 71.4% of patients, with complete response in 23.8% of cases. None of our patients presented GVHD progression upon MSC administration, but 4 patients presented GVHD recurrence 2 to 5 months after infusion. Two patients developed chronic limited GVHD. This study underlines the safety of PL-expanded MSC use in children. MSC efficacy seems to be greater in aGVHD than in cGVHD, even after failure of multiple lines of immunosuppression.

Mesenchymal stem cell therapy: Two steps forward, one step back

Mesenchymal stem cell (MSC) therapy is poised to establish a new clinical paradigm; however, recent trials have produced mixed results. Although MSC were originally considered to treat connective tissue defects, preclinical studies revealed potent immunomodulatory properties that prompted the use of MSC to treat numerous inflammatory conditions. Unfortunately, although clinical trials have met safety endpoints, efficacy has not been demonstrated. We believe the challenge to demonstrate efficacy can be attributed in part to an incomplete understanding of the fate of MSC following infusion. Here, we highlight the clinical status of MSC therapy and discuss the importance of cell-tracking techniques, which have advanced our understanding of the fate and function of systemically infused MSC and might improve clinical application.

Stem cell therapy for type 1 diabetes mellitus

The use of stem cells in regenerative medicine holds great promise for the cure of many diseases, including type 1 diabetes mellitus (T1DM). Any potential stem-cell-based cure for T1DM should address the need for beta-cell replacement, as well as control of the autoimmune response to cells which express insulin. The ex vivo generation of beta cells suitable for transplantation to reconstitute a functional beta-cell mass has used pluripotent cells from diverse sources, as well as organ-specific facultative progenitor cells from the liver and the pancreas. The most effective protocols to date have produced cells that express insulin and have molecular characteristics that closely resemble bona fide insulin-secreting cells; however, these cells are often unresponsive to glucose, a characteristic that should be addressed in future protocols. The use of mesenchymal stromal cells or umbilical cord blood to modulate the immune response is already in clinical trials; however, definitive results are still pending. This Review focuses on current strategies to obtain cells which express insulin from different progenitor sources and highlights the main pathways and genes involved, as well as the different approaches for the modulation of the immune response in patients with T1DM.

Allogenic stem cell therapy improves right ventricular function by improving lung pathology in rats with pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a chronic lung disease that leads to right ventricular (RV) hypertrophy (RVH), remodeling, and failure. We tested treatment with bone marrow-derived mesenchymal stem cells (MSCs) obtained from donor rats with monocrotaline (MCT)-induced PAH to recipient rats with MCT-induced PAH on pulmonary artery pressure, lung pathology, and RV function. This model was chosen to mimic autologous MSC therapy. On day 1, PAH was induced by MCT (60 mg/kg) in 20 female Wistar rats. On day 14, rats were treated with 106 MSCs intravenously (MCT + MSC) or with saline (MCT60). MSCs were obtained from donor rats with PAH at 28 days after MCT. A control group received saline on days 1 and 14. On day 28, the RV function of recipient rats was assessed, followed by isolation of the lungs and heart. RVH was quantified by the weight ratio of the RV/(left ventricle + interventricular septum). MCT induced an increase of RV peak pressure (from 27 ± 5 to 42 ± 17 mmHg) and RVH (from 0.25 ± 0.04 to 0.47 ± 0.12), depressed the RV ejection fraction (from 56 ± 11 to 43 ± 6%), and increased lung weight (from 0.96 ± 0.15 to 1.66 ± 0.32 g), including thickening of the arteriolar walls and alveolar septa. MSC treatment attenuated PAH (31 ± 4 mmHg) and RVH (0.32 ± 0.07), normalized the RV ejection fraction (52 ± 5%), reduced lung weight (1.16 ± 0.24 g), and inhibited the thickening of the arterioles and alveolar septa. We conclude that the application of MSCs from donor rats with PAH reduces RV pressure overload, RV dysfunction, and lung pathology in recipient rats with PAH. These results suggest that autologous MSC therapy may alleviate cardiac and pulmonary symptoms in PAH patients.

Vascular endothelial growth factor (VEGF) as a key therapeutic trophic factor in bone marrow mesenchymal stem cell-mediated cardiac repair

We recently demonstrated a novel effective therapeutic regimen for treating hamster heart failure based on injection of bone marrow mesenchymal stem cells (MSCs) or MSC-conditioned medium into the skeletal muscle. The work highlights an important cardiac repair mechanism mediated by the myriad of trophic factors derived from the injected MSCs and local musculature that can be explored for non-invasive stem cell therapy. While this therapeutic regimen provides the ultimate proof that MSC-based cardiac repair is mediated by the trophic actions independent of MSC differentiation or stemness, the trophic factors responsible for cardiac regeneration after MSC therapy remain largely undefined. Toward this aim, we took advantage of the finding that human and porcine MSCs exhibit species-related differences in expression of trophic factors. We demonstrate that human MSCs when compared to porcine MSCs express and secrete 5-fold less vascular endothelial growth factor (VEGF) in conditioned medium (40+/-5 and 225+/-17 pg/ml VEGF, respectively). This deficit in VEGF output was associated with compromised cardiac therapeutic efficacy of human MSC-conditioned medium. Over-expression of VEGF in human MSCs however completely restored the therapeutic potency of the conditioned medium. This finding indicates VEGF as a key therapeutic trophic factor in MSC-mediated myocardial regeneration, and demonstrates the feasibility of human MSC therapy using trophic factor-based cell-free strategies, which can eliminate the concern of potential stem cell transformation.

Sleuthing the source of regeneration by MSCs

Mesenchymal stem cells (MSCs) can differentiate into useful cell types and also have the ability to modulate inflammation. In this issue of Cell Stem Cell, Lee et al. (2009) investigate the production of the soluble inflammation inhibitor TSG-6 by MSCs.