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Background Aims: Mesenchymal stroma/stem-like cells (MSCs) are a popular cell source and hold huge therapeutic promise for a broad range of possible clinical applications. However, to harness their full potential, current limitations in harvesting, expansion and characterization have to be overcome. These limitations are related to the heterogeneity of MSCs in general as well as to inconsistent experimental protocols. Here we aim to compare in vitro methods to facilitate comparison of MSCs generated from various tissues., Methods: MSCs from 3 different tissues (bone marrow, dental pulp, adipose tissue), exemplified by cells from 3 randomly chosen donors per tissue, were systematically compared with respect to their in vitro properties after propagation in specific in-house standard media, as established in the individual laboratories, or in the same commercially available medium., Results: Large differences were documented with respect to the expression of cell surface antigens, population doubling times, basal expression levels of 5 selected genes and osteogenic differentiation. The commercial medium reduced differences in these parameters with respect to individual human donors within tissue and between tissues. The extent, size and tetraspanin composition of extracellular vesicles were also affected., Conclusions: The results clearly demonstrate the extreme heterogeneity of MSCs, which confirms the problem of reproducibility of results, even when harmonizing experimental conditions, and questions the significance of common parameters for MSCs from different tissues in vitro., (Copyright © 2020 International Society for Cell & Gene Therapy. Published by Elsevier Inc. All rights reserved.)

Cellular therapy represents a novel option for the treatment of neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS). Its major aim is the generation of a protective environment for degenerating motor neurons. Mesenchymal stromal cells secrete different growth factors and have antiapoptotic and immunomodulatory properties. They can easily and safely be isolated from human bone marrow and are therefore considered promising therapeutic candidates. In the present study, we compared intraventricular application of human mesenchymal stromal cells (hMSCs) versus single and repeated intraspinal injections in the mutant SOD1 G93A transgenic ALS mouse model. We observed significant reduction of lifespan of animals treated by intraventricular hMSC injection compared with the vehicle treated control group, accompanied by changes in weight, general condition, and behavioural assessments. A potential explanation for these rather surprising deleterious effects lies in increased microgliosis detected in the hMSC treated animals. Repeated intraspinal injection at two time points resulted in a slight but not significant increase in survival and significant improvement of motor performance although no hMSC-induced changes of motor neuron numbers, astrogliosis, and microgliosis were detected. Quantitative real time polymerase chain reaction showed reduced expression of endothelial growth factor in animals having received hMSCs twice compared with the vehicle treated control group. hMSCs were detectable at the injection site at Day 20 after injection into the spinal cord but no longer at Day 70. Intraspinal injection of hMSCs may therefore be a more promising option for the treatment of ALS than intraventricular injection and repeated injections might be necessary to obtain substantial therapeutic benefit., (© 2019 John Wiley & Sons, Ltd.)

The immunosuppressive properties of mesenchymal stromal cells (MSC) have been successfully tested to control clinical severe graft-versus host disease and improve survival. However, clinical studies have not yet provided conclusive evidence of their efficacy largely because of lack of patients' stratification criteria. The heterogeneity of MSC preparations is also a major contributing factor, as manufacturing of therapeutic MSC is performed according to different protocols among different centers. Understanding the variability of the manufacturing protocol would allow a better comparison of the results obtained in the clinical setting among different centers. In order to acquire information on MSC manufacturing we sent a questionnaire to the European Society for Blood and Marrow Transplantation centers registered as producing MSC. Data from 17 centers were obtained and analyzed by means of a 2-phase questionnaire specifically focused on product manufacturing. Gathered information included MSC tissue sources, MSC donor matching, medium additives for ex vivo expansion, and data on MSC product specification for clinical release. The majority of centers manufactured MSC from bone marrow (88%), whilst only 2 centers produced MSC from umbilical cord blood or cord tissue. One of the major changes in the manufacturing process has been the replacement of fetal bovine serum with human platelet lysate as medium supplement. 59% of centers used only third-party MSC, whilst only 1 center manufactured exclusively autologous MSC. The large majority of these facilities (71%) administered MSC exclusively from frozen batches. Aside from variations in the culture method, we found large heterogeneity also regarding product specification, particularly in the markers used for phenotypical characterization and their threshold of expression, use of potency assays to test MSC functionality, and karyotyping. The initial data collected from this survey highlight the variability in MSC manufacturing as clinical products and the need for harmonization. Until more informative potency assays become available, a more homogeneous approach to cell production may at least reduce variability in clinical trials and improve interpretation of results., (Copyright © 2018. Published by Elsevier Inc.)

Therapeutic approaches using multipotent mesenchymal stromal cells (MSCs) are advancing in regenerative medicine, transplantation, and autoimmune diseases. The mechanisms behind MSC immune modulation are still poorly understood and the prediction of the immune modulatory potential of single MSC preparations remains a major challenge for possible clinical applications. Here, we highlight galectin-9 (Gal-9) as a novel, important immune modulator expressed by MSCs, which is strongly upregulated upon activation of the cells by interferon-γ (IFN-γ). Further, we demonstrate that Gal-9 is a major mediator of the anti-proliferative and functional effects of MSCs not only on T cells but also on B cells. Here, Gal-9 and activated MSCs contribute to the suppression of antigen triggered immunoglobulin release. Moreover, we determined that Gal-9 expression could serve as a marker to predict a higher or lower immune modulatory potential of single cell preparations and therefore to distinguish the therapeutic potency of MSCs derived from different donors. Also in vivo co-administration of MSCs or murine Gal-9 resulted in significantly reduced IgG titers in mice immunized with human coagulation factor VIII (FVIII). In conclusion, Gal-9 acts as an immune modulator interfering with multiple cell types including B cells and Gal-9 may serve as a predictive indicator for clinical MSC therapy.