Are mesenchymal stromal cells immune cells?

Mesenchymal stromal cells (MSCs) are considered to be promising agents for the treatment of immunological disease. Although originally identified as precursor cells for mesenchymal lineages, in vitro studies have demonstrated that MSCs possess diverse immune regulatory capacities. Pre-clinical models have shown beneficial effects of MSCs in multiple immunological diseases and a number of phase 1/2 clinical trials carried out so far have reported signs of immune modulation after MSC infusion. These data indicate that MSCs play a central role in the immune response. This raises the academic question whether MSCs are immune cells or whether they are tissue precursor cells with immunoregulatory capacity. Correct understanding of the immunological properties and origin of MSCs will aid in the appropriate and safe use of the cells for clinical therapy. In this review the whole spectrum of immunological properties of MSCs is discussed with the aim of determining the position of MSCs in the immune system.     

Neuropeptides to replace serum in cryopreservation of mesenchymal stromal cells?

Background aimsThe therapeutic potential of human mesenchymal stromal cells (MSCs) has generated considerable interest in a wide variety of areas. MSC banking is feasible, but the optimal technique of cryopreservation remains to be determined.MethodsTo reduce dimethyl sulfoxide (DMSO) concentration in cryopreservation medium, DMSO was replaced with sucrose or trehalose. To increase cell survival and proliferation rates after thawing and to eliminate the need for fetal bovine serum (FBS), neuropeptides of the vasoactive intestinal peptide/glucose-dependent insulinotropic peptide/pituitary adenylate cyclase activating polypeptide family were added to the cryopreservation medium. Cell survival was analyzed by a trypan blue dye exclusion assay. Cell proliferation of cryopreserved MSCs was determined after 7 days of culture.ResultsNo significant differences in cell survival rates were detected between cryopreservation solutions with 5% and 10% DMSO, independently of the addition of trehalose or sucrose. Cell proliferation rates tended to be highest when MSCs were frozen in 5% DMSO + trehalose. FBS could be replaced by human albumin (HA) without loss in cell survival and proliferation potential. With FBS, the addition of neuropeptides could increase cell survival and proliferation rates. Without FBS or HA, cell survival and proliferation rates in the presence of neuropeptides were comparable to rates achieved with FBS or HA.ConclusionsClassic cryopreservation with 10% DMSO could be replaced by 5% DMSO + 30 mmol/L trehalose. FBS could be replaced by HA or neuropeptides without loss in cell survival and proliferation potential. The addition of neuropeptides in the cryopreservation medium containing FBS could increase the cell proliferation rate and consequently cellular output.     

Mortalin antibody-conjugated quantum dot transfer from human mesenchymal stromal cells to breast cancer cells requires cell–cell interaction

The role of tumor stroma in regulation of breast cancer growth has been widely studied. However, the details on the type of heterocellular cross-talk between stromal and breast cancer cells (BCCs) are still poorly known. In the present study, in order to investigate the intercellular communication between human mesenchymal stromal cells (hMSCs) and breast cancer cells (BCCs, MDA-MB-231), we recruited cell-internalizing quantum dots (i-QD) generated by conjugation of cell-internalizing anti-mortalin antibody and quantum dots (QD). Co-culture of illuminated and color-coded hMSCs (QD655) and BCCs (QD585) revealed the intercellular transfer of QD655 signal from hMSCs to BCCs. The amount of QD double positive BCCs increased gradually within 48 h of co-culture. We found prominent intercellular transfer of QD655 in hanging drop co-culture system and it was non-existent when hMSCs and BBCs cells were co-cultured in trans-well system lacking imminent cell–cell contact. Fluorescent and electron microscope analyses also supported that the direct cell-to-cell interactions may be required for the intercellular transfer of QD655 from hMSCs to BCCs. To the best of our knowledge, the study provides a first demonstration of transcellular crosstalk between stromal cells and BCCs that involve direct contact and may also include a transfer of mortalin, an anti-apoptotic and growth-promoting factor enriched in cancer cells.     

Are breast tumours resistant to tamoxifen also resistant to pure antioestrogens?

A substantial proportion of patients with breast cancer are treated with the antioestrogen tamoxifen. As with other endocrine therapies, clinical experience has shown that some tumours in which growth is initially attenuated by tamoxifen treatment become resistant to continued drug treatment and resume growth. The mechanisms underlying the development of tamoxifen resistance have yet to be described but represent an important focus of research with the aim of defining what other therapies might be effective following tamoxifen treatment. Secondly, an understanding of tamoxifen resistance might suggest means to develop more effective agents for primary treatment of the disease. The development of pure antioestrogens, for example ICI 164,384 and ICI 182,780, which differ pharmacologically from tamoxifen in being entirely free of oestrogen partial-agonist activity, together with cell and animal models of tamoxifen resistant human breast cancer, has revealed one mechanism which might be of considerable clinical significance. Pure antioestrogens were shown to inhibit the proliferation of a greater proportion of tumor cells than tamoxifen in vitro, a differential effect that was attributed to the oestrogenic activity of tamoxifen. Subsequently, cell culture studies have shown that breast cancer cell lines selected for resistance to tamoxifen can still remain sensitive to the growth inhibitory action of pure antioestrogens. Similarly, the growth of human breast tumours in nude mice, which is initially attenuated by tamoxifen but then resumes, can be inhibited by pure antioestrogens. Both types of experiment are consistent with the view that tamoxifen resistance in these model systems is due to the oestrogenic action of tamoxifen. Thus, it can be predicted that in some patients whose tumours recur during tamoxifen therapy, a further response to pure antioestrogen treatment might occur. Studies to examine this hypothesis are currently being undertaken with ICI 182,780. One mechanism which might account for the experimental observations is an intrinsic heterogeneity amongst breast tumour cells in their response to tamoxifen, i.e. that there are at least two different populations of cells; one population which responds to tamoxifen as an antioestrogen and one which “reads” tamoxifen as an oestrogen. The growth advantage thus conferred on the latter population would lead to its predominance. If this is what actually happens in a proportion of human tumours, it can be argued that primary treatment of the tumour with a pure antioestrogen, rather than tamoxifen, would be preferred since a more complete and longer-lasting response would be predicted. Recent comparative studies with human breast tumours grown in nude mice support these predictions.     

Are Biomphalaria snails resistant to Schistosoma mansoni?

Among Biomphalaria glabrata/Schistosoma mansoni snail-trematode combinations, it appears that some parasites succeed whilst others fail to infect snails. Snails that become infected are termed susceptible hosts. Those which are not infected are traditionally determined as 'resistant'. Here the concept of B. glabrata resistance to S. mansoni is re-examined in the light of additional observations. It is suggested that, in B. glabrata/S. mansoni, compatibility is tested independently for each individual miracidium and host, and that the success or failure of an infection does not depend on the snail susceptibility/resistance status, but on the 'matched' or 'mismatched' status of the host and parasite phenotypes.     

Skin-derived multipotent stromal cells – an archrival for mesenchymal stem cells

Progenitor stem cells have been identified, isolated and characterized in numerous tissues and organs. However, their therapeutic potential and the use of these stem cells remain elusive except for a few progenitor cells from bone marrow, umbilical cord blood, eyes and dental pulp. The use of bone marrow-derived hematopoietic stem cells (HSC) or mesenchymal stem cells (MSCs) is restricted due to their extreme invasive procedures, low differentiation potential with age and rejection. Thus, we need a clinical grade alternative to progenitor stem cells with a high potential to differentiate, na?ve and is relatively easy in in vitro propagation. In this review, we summarize cell populations of adherent and floating spheres derived from different origins of skin, or correctly foreskin, by enzymatic digestion compared with established MSCs. The morphology, phenotype, differentiation capability and immunosuppressive property of the adherent cell populations are comparable with MSCs. Serum-free cultured floating spheres have limited mesodermal but higher neurogenic differentation potential, analogous to neural crest stem cells. Both the populations confirmed their plethora potential in in vitro. Together, it may be noted that the skin-derived adherent cell populations and floating cells can be good alternative sources of progenitor cells especially in cosmetic, plastic and sports regenerative medicine.     

Amnion-derived mesenchymal stromal cells show a mesenchymal–epithelial phenotype in culture

The amnionic membrane is a rich source of multipotent mesenchymal stromal cells (hAMSC), which are readily available and show a potential use in regenerative medicine and tissue engineering. Before these cells can be applied clinically, careful characterization is necessary, especially as primary cells are known to change their phenotype in culture. We analyzed the mesenchymal phenotype of hAMSC at different stages after isolation using immunohistochemistry. Shortly after isolation (1 day), 92 % (±7 %) of the hAMSC expressed the mesenchymal marker vimentin, 2 % (±1 %) stained for the epithelial marker cytokeratin-7 and 5 % (±4 %) co-expressed these markers. After 5 days, the double positive cells slightly increased to 7 % (±3 %), while exclusive expression of cytokeratin-7 or vimentin remained unchanged (1 % ± 2 % and 92 % ± 1 %, respectively). After the first passage, all attached cells were vimentin-positive, while 54 % (±9 %) co-expressed cytokeratin-7 and vimentin. Thus, we conclude that under culture, hAMSC adopt a hybrid mesenchymal–epithelial phenotype. It is also essential to perform microscopical examination during the first days after isolation to detect contaminations with human amnion-derived epithelial cells in cultures of hAMSC.     

Is CD34 truly a negative marker for mesenchymal stromal cells?

The prevailing school of thought is that mesenchymal stromal cells (MSC) do not express CD34, and this sets MSC apart from hematopoietic stem cells (HSC), which do express CD34. However, the evidence for MSC being CD34^? is largely based on cultured MSC, not tissue-resident MSC, and the existence of CD34^? HSC is in fact well documented. Furthermore, the Stro-1 antibody, which has been used extensively for the identification/isolation of MSC, was generated by using CD34⁺ bone marrow cells as immunogen. Thus, neither MSC being CD34^? nor HSC being CD34⁺ is entirely correct. In particular, two studies that analyzed CD34 expression in uncultured human bone marrow nucleated cells found that MSC (BMSC) existed in the CD34⁺ fraction. Several studies have also found that freshly isolated adipose-derived MSC (ADSC) express CD34. In addition, all of these ADSC studies and several other MSC studies have observed a disappearance of CD34 expression when the cells are propagated in culture. Thus the available evidence points to CD34 being expressed in tissue-resident MSC, and its negative finding being a consequence of cell culturing.     

Homing and migration of mesenchymal stromal cells: How to improve the efficacy of cell therapy?

Mesenchymal stromal cells(MSCs) are currently being investigated for use in a wide variety of clinical applications. For most of these applications, systemic delivery of the cells is preferred. However, this requires the homing and migration of MSCs to a target tissue. Although MSC hominghas been described, this process does not appear to be highly efficacious because only a few cells reach the target tissue and remain there after systemic administration. This has been ascribed to low expression levels of homing molecules, the loss of expression of such molecules during expansion, and the heterogeneity of MSCs in cultures and MSC culture protocols. To overcome these limitations, different methods to improve the homing capacity of MSCs have been examined. Here, we review the current understanding of MSC homing, with a particular focus on homing to bone marrow. In addition, we summarize the strategies that have been developed to improve this process. A better understanding of MSC biology, MSC migration and homing mechanisms will allow us to prepare MSCs with optimal homing capacities. The efficacy of therapeutic applications is dependent on efficient delivery of the cells and can, therefore, only benefit from better insights into the homing mechanisms.     

Is the subarachnoid administration of mesenchymal stromal cells a useful strategy to treat chronic brain damage?

Background aimsTraumatic brain injury (TBI) is a leading cause of mortality and morbidity worldwide. Developing effective protocols for the administration of mesenchymal stromal cells (MSCs) is a promising therapeutic strategy to treat TBI. It is important to develop alternatives to direct parenchymal injection at the injury site because direct injection is an expensive and invasive technique. Subarachnoid transplantation, a minimally invasive and low-risk procedure, may be an important and clinically applicable strategy. The aim of this study was to test the therapeutic effect of subarachnoid administration of MSCs on functional outcome 2 months after an experimental TBI in rats.MethodsTwo months after TBI, 30 female Wistar rats were divided into 3 groups (n = 10 in each group): sham, MSC (received 2 × 10⁶ MSCs) and saline (received only saline) groups. Neurological function, brain and spinal cords samples and cerebrospinal fluid were studied.ResultsNo significant differences were found in neurological evaluation and after histological analysis; differences in the expression of neurotrophins were present but were not statistically significant. MSCs survived in the host tissue, and some expressed neural markers.ConclusionsSimilar to direct parenchymal injections, transplanted MSCs survive, migrate to the injury cavity and differentiate into mature neural cell types for at least 6 months after engraftment. These results open the possibility that MSC administration through subarachnoid administration may be a treatment for the consequences of TBI. The transplantation technique and cell number should be adjusted to obtain functional outcome and neurotrophin production differences.     

Immune regulatory properties of multipotent mesenchymal stromal cells: Where do we stand?

Multipotent mesenchymal stromal cells (MSC) can be isolated and efficiently expanded from almost every single body tissue and have the ability of self-renewal and differentiation into various mesodermal cell lineages. Moreover, these cells are considered immunologically privileged, related to a lack of surface expression of costimulatory molecules required for complete T cell activation. Recently, it has been observed that MSC are capable of suppressing the immune response by inhibiting the maturation of dendritic cells and suppressing the function of T lymphocytes, B lymphocytes and natural killer cells in autoimmune and inflammatory diseases as a new strategy for immunosuppression. The understanding of immune regulation mechanisms by MSC is necessary for their use as immunotherapy in clinical applications for several diseases.     

Are coelenterate cells permeable to large anions?

• 1.1. Substitution of chloride by isethionate, a bulky anion, did not modify the intracellular cation or water content in cells of tentacles, and only slightly decreased sodium content in body wall cells of the coelenterate Condylactis gigantea, in contrast with the appreciable reductions expected in the case of impenneant anions.
• 2.2. As isethionic acid is a strong acid, the salt should be almost totally ionized at the pH of seawater (8.6) and at the presumably close to neutral intracellular pH. Therefore, the anion, rather than the undissociated acid, would appear to be the permeating species.
• 3.3. Isethionate ion appears to distribute across the cell membrane as does chloride: according to the transmembrane potential difference.

     

Effect of bone marrow–derived mesenchymal stromal cells on hepatoma

Background aimsThe aim of the study was to evaluate the effect of mesenchymal stromal cells (MSCs) on tumor cell growth in vitro and in vivo and to elucidate the apoptotic and anti-proliferative mechanisms of MSCs on a hepatocellular carcinoma (HCC) murine model.MethodsThe growth-inhibitory effect of MSCs on the Hepa 1–6 cell line was tested by means of methyl thiazolyl diphenyl-tetrazolium assay. Eighty female mice were randomized into four groups: group 1 consisted of 20 mice that received MSCs only by intrahepatic injection; group 2 consisted of 20 HCC mice induced by inoculation of Hepa 1–6 cells into livers without MSC treatment; group 3 consisted of 20 mice that received MSCs after induction of liver cancer; group 4 consisted of 20 mice that received MSCs after induction of liver cancer on top of induced biliary cirrhosis.ResultsMSCs exhibited a growth-inhibitory effect on Hepa 1–6 murine cell line in vitro. Concerning in vivo study, decreases of serum alanine transaminase, aspartate transaminase and albumin levels after MSC transplantation in groups 2 and 3 were found. Gene expression of α-fetoprotein was significantly downregulated after MSC injection in the HCC groups. We found that gene expression of caspase 3, P21 and P53 was significantly upregulated, whereas gene expression of Bcl-2 and survivin was downregulated in the HCC groups after MSC injection. Liver specimens of the HCC groups confirmed the presence of dysplasia. The histopathological picture was improved after administration of MSCs to groups 2 and 3.ConclusionsMSCs upregulated genes that help apoptosis and downregulated genes that reduce apoptosis. Therefore, MSCs could inhibit cell division of HCC and potentiate their death.     

Are non-directional simple cells constructed from directional subunits?

Experiments by Schiller et al. have suggested that non-directional edge-specific simple cells are constructed from two directionally selective subunits with opposite preferred direction. This hierarchical notion was based on the fact that the responses of such units to edges moving in opposite directions are spatially displaced with respect to each other.An alternative explanation of the observed response separation is the delay between the responses of the center and surround mechanisms at the retinal level. Measurements of the response separation as a function of stimulus speed support this explanation and argues against the hierarchical notion of Schiller et al.     

Manufacturing and characterization of extracellular vesicles from umbilical cord–derived mesenchymal stromal cells for clinical testing

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) may deliver therapeutic effects that are comparable to their parental cells. MSC-EVs are promising agents for the treatment of a variety of diseases. To reach the intermediate goal of clinically testing safety and efficacy of EVs, strategies should strive for efficient translation of current EV research. On the basis of our in vitro an in vivo findings regarding the biological actions of EVs and our experience in manufacturing biological stem cell therapeutics for routine use and clinical testing, we discuss strategies of manufacturing and quality control of umbilical cord–derived MSC-EVs. We introduce guidelines of good manufacturing practice and their practicability along the path from the laboratory to the patient. We present aspects of manufacturing and final product quality testing and highlight the principle of “The process is the product.” The approach presented in this perspective article may facilitate translational research during the development of complex biological EV-based therapeutics in a very early stage of manufacturing as well as during early clinical safety and proof-of-concept testing.     

Are mesenchymal stem cells in rheumatoid arthritis the good or bad guys?

The advancements in our understanding of the inflammatory and immune mechanisms in rheumatoid arthritis (RA) have fuelled the development of targeted therapies that block cytokine networks and pathogenic immune cells, leading to a considerable improvement in the management of RA patients. Nonetheless, no therapy is curative and clinical remission does not necessarily correspond to non-progression of joint damage. Hence, the biomedical community has redirected scientific efforts and resources towards the investigation of other biological aspects of the disease, including the mechanisms driving tissue remodelling and repair. In this regard, stem cell research has attracted extraordinary attention, with the ultimate goal to develop interventions for the biological repair of damaged tissues in joint disorders, including RA. The recent evidence that mesenchymal stem cells (MSCs) with the ability to differentiate into cartilage are present in joint tissues raises an opportunity for therapeutic interventions via targeting intrinsic repair mechanisms. Under physiological conditions, MSCs in the joint are believed to contribute to the maintenance and repair of joint tissues. In RA, however, the repair function of MSCs appears to be repressed by the inflammatory milieu. In addition to being passive targets, MSCs could interact with the immune system and play an active role in the perpetuation of arthritis and progression of joint damage. Like MSCs, fibroblast-like synoviocytes (FLSs) are part of the stroma of the synovial membrane. During RA, FLSs undergo proliferation and contribute to the formation of the deleterious pannus, which mediates damage to articular cartilage and bone. Both FLSs and MSCs are contained within the mononuclear cell fraction in vitro, from which they can be culture expanded as plastic-adherent fibroblast-like cells. An important question to address relates to the relationship between MSCs and FLSs. MSCs and FLSs could be the same cell type with functional specialisation or represent different functional stages of the same stromal lineage. This review will discuss the roles of MSCs in RA and will address current knowledge of the relative identity between MSCs and FLSs. It will also examine the immunomodulatory properties of the MSCs and the potential to harness such properties for the treatment of RA.     

Are mesenchymal stem cells major sources of safe signals in immune system?

Numerous reports have shown that mesenchymal stem cells (MSCs) are implicated in immuno-regulation. Several factors expressed from MSCs, especially indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2), are of importance in immuno-regulation on immune cells. In current minireview, we provided evidences to support a novel notion that MSCs may be a major source of "safe signals" in the immune system to balance "dangerous signals" based on a well accepted theory of "danger model". Furthermore, MSCs are of lifecycle characterized by age-and diseased-related changes, such as decreased growth rate, increased senescence, and altered morphology. Thus, defected and abnormal MSCs are implicated in auto-immune diseases, such as systemic lupus erythematosus (SLE). Clinically, it is important to determine clinical benefits and sides effects of cell therapies using autologous self-MSCs or healthy allogeneic MSCs in treatment of autoimmune diseases.     

Are plant communities on the Canary Islands resistant to plant invasion?

Oceanic islands are renowned for their unique flora and high levels of endemism. Native island plants, however, are imperilled by non-native species that can become invasive by outcompeting natives. The threat of native island assemblages generally increases with isolation and the number of endemics featured, but also with human-associated disturbance and land use. Based on this, the Canary Island native plant systems should be highly threatened by invasives, similar to other oceanic islands globally. However, Canarian native plant systems are only weakly infiltrated and are rarely directly threatened by invasive plants. Further, highly disturbed areas, usually among the first colonized by invasives on islands, are recolonized here by natives. Based on this, we postulate four hypotheses (climatic filter, well-preservation status, human legacy and permanent colonization) for explaining this unusual behaviour of plant systems on the Canary Islands, providing an opportunity to understand the drivers and processes behind invasion into plant communities on islands.