Unveiling the Differences of Secretome of Human Bone Marrow Mesenchymal Stem Cells, Adipose Tissue-Derived Stem Cells, and Human Umbilical Cord Perivascular Cells: A Proteomic Analysis

Concise Review: Mesenchymal Stem Cells in Neurodegenerative Diseases

Stem cell-based therapies for neurodegenerative diseases aim at halting clinical deterioration by regeneration and by providing local support for damaged tissue. Mesenchymal stem cells (MSCs) hold great potential for cell therapy as they can be efficiently derived from adult tissue, ex vivo expanded in culture and safely transplanted autologously. MSCs were also shown to be able to differentiate toward neural fates and to secrete a broad range of factors able to promote nervous tissue maintenance and repair. Moreover, upon transplantation, MSCs were shown capable of homing toward lesioned areas, implying their potential use as vehicles for therapeutic agents administration. Indeed, various advantageous effects were reported following human MSCs transplantation into rodent models of neurodegenerative diseases, such as neurotrophic factor-mediated protection, enhanced neurogenesis, modulation of inflammation, and abnormal protein aggregate clearance. Recent studies have also used ex vivo manipulation for enhanced expression of potentially favorable factors, by so exploiting the homing capacity of MSCs for effective expression at the lesion site. Here, we will summarize current advancements in MSCs-based therapies for neurodegenerative diseases. We will examine the roles of central mechanisms suggested to mediate the beneficial effects of MSCs-based therapy and consider the augmentation of these mechanisms for superior clinical outcomes in rodent models of neurodegeneration as well as in clinical trials.

Concise Review: Mesenchymal Stem Cells in Neurodegenerative Diseases

Stem cell-based therapies for neurodegenerative diseases aim at halting clinical deterioration by regeneration and by providing local support for damaged tissue. Mesenchymal stem cells (MSCs) hold great potential for cell therapy as they can be efficiently derived from adult tissue, ex vivo expanded in culture and safely transplanted autologously. MSCs were also shown to be able to differentiate toward neural fates and to secrete a broad range of factors able to promote nervous tissue maintenance and repair. Moreover, upon transplantation, MSCs were shown capable of homing toward lesioned areas, implying their potential use as vehicles for therapeutic agents administration. Indeed, various advantageous effects were reported following human MSCs transplantation into rodent models of neurodegenerative diseases, such as neurotrophic factor-mediated protection, enhanced neurogenesis, modulation of inflammation, and abnormal protein aggregate clearance. Recent studies have also used ex vivo manipulation for enhanced expression of potentially favorable factors, by so exploiting the homing capacity of MSCs for effective expression at the lesion site. Here, we will summarize current advancements in MSCs-based therapies for neurodegenerative diseases. We will examine the roles of central mechanisms suggested to mediate the beneficial effects of MSCs-based therapy and consider the augmentation of these mechanisms for superior clinical outcomes in rodent models of neurodegeneration as well as in clinical trials.

Dynamics of plasma membrane surface related to the release of extracellular vesicles by mesenchymal stem cells in culture

Extracellular vesicles (exosomes and shedding vesicles) released by mesenchymal stem cells (MSCs) are regarded as a storable, cell-free alternative with comparable therapeutic potential to their parent cells. Shedding vesicles originate as bulges on the cell surface but little is known about their turnover or how their formation can be stimulated. We have used atomic force microscopy (AFM) to follow the formation dynamics of bulges in living adipose tissue-derived MSCs. AFM images showed that, in general, MSCs present hundreds of nanosized protrusions on their surface with life spans of 10-20 min. Scanning electron microscopy confirmed those images and showed that bulges are also formed on filamentous processes. Extracellular vesicles deposited on the culture surface have comparable sizes to those of bulges showing up on the cell surface. The amount of protrusions on cells treated with progesterone or PDGF-BB, two treatments that stimulate the secretion of extracellular vesicles in MSCs, was evaluated by AFM. Measurements of the cross-area at 50 nm over the cell surface provided estimates of the amount of protrusions and showed that these values increased with the stimulating treatments. Our study suggests that shedding vesicles constitute a large population of the extracellular vesicle pool.

Umbilical cord: an unlimited source of cells differentiable towards dopaminergic neurons

Cell replacement therapy utilizing mesenchymal stem cells as its main resource holds great promise for ultimate treatment of human neurological disorders. Parkinson's disease (PD) is a common, chronic neurodegenerative disorder hallmarked by localized degeneration of a specific set of dopaminergic neurons within a midbrain sub-region. The specific cell type and confined location of degenerating neurons make cell replacement therapy ideal for PD treatment since it mainly requires replenishment of lost dopaminergic neurons with fresh and functional ones. Endogenous as well as exogenous cell sources have been identified as candidate targets for cell replacement therapy in PD. In this review, umbilical cord mesenchymal stem cells (UCMSCs) are discussed as they provide an inexpensive unlimited reservoir differentiable towards functional dopaminergic neurons that potentially lead to long-lasting behavioral recovery in PD patients. We also present miRNAs-mediated neuronal differentiation of UCMSCs. The UCMSCs bear a number of outstanding characteristics including their non-tumorigenic, low-immunogenic properties that make them ideal for cell replacement therapy purposes. Nevertheless, more investigations as well as controlled clinical trials are required to thoroughly confirm the efficacy of UCMSCs for therapeutic medical-grade applications in PD.

Concise Review: Mesenchymal Stem Cells in Neurodegenerative Diseases

Stem cell-based therapies for neurodegenerative diseases aim at halting clinical deterioration by regeneration and by providing local support for damaged tissue. Mesenchymal stem cells (MSCs) hold great potential for cell therapy as they can be efficiently derived from adult tissue, ex vivo expanded in culture and safely transplanted autologously. MSCs were also shown to be able to differentiate toward neural fates and to secrete a broad range of factors able to promote nervous tissue maintenance and repair. Moreover, upon transplantation, MSCs were shown capable of homing toward lesioned areas, implying their potential use as vehicles for therapeutic agents administration. Indeed, various advantageous effects were reported following human MSCs transplantation into rodent models of neurodegenerative diseases, such as neurotrophic factor-mediated protection, enhanced neurogenesis, modulation of inflammation, and abnormal protein aggregate clearance. Per journal style, most nonstandard abbreviations must be used at least two times in the abstract to be retained; NTF was used once and thus has been deleted. Recent studies have also used ex vivo manipulation for enhanced expression of potentially favorable factors, by so exploiting the homing capacity of MSCs for effective expression at the lesion site. Here, we will summarize current advancements in MSCs-based therapies for neurodegenerative diseases. We will examine the roles of central mechanisms suggested to mediate the beneficial effects of MSCs-based therapy and consider the augmentation of these mechanisms for superior clinical outcomes in rodent models of neurodegeneration as well as in clinical trials. Stem Cells 2017;35:1867-1880.

Mesenchymal Stromal Cells as Anti-Inflammatory and Regenerative Mediators for Donor Kidneys During Normothermic Machine Perfusion

There is great demand for transplant kidneys for the treatment of end-stage kidney disease patients. To expand the donor pool, organs from older and comorbid brain death donors, so-called expanded criteria donors (ECD), as well as donation after circulatory death donors, are considered for transplantation. However, the quality of these organs may be inferior to standard donor organs. A major issue affecting graft function and survival is ischemia/reperfusion injury, which particularly affects kidneys from deceased donors. The development of hypothermic machine perfusion has been introduced in kidney transplantation as a preservation technique and has improved outcomes in ECD and marginal organs compared to static cold storage. Normothermic machine perfusion (NMP) is the most recent evolution of perfusion technology and allows assessment of the donor organ before transplantation. The possibility to control the content of the perfusion fluid offers opportunities for damage control and reparative therapies during machine perfusion. Mesenchymal stromal cells (MSC) have been demonstrated to possess potent regenerative properties via the release of paracrine effectors. The combination of NMP and MSC administration at the same time is a promising procedure in the field of transplantation. Therefore, the MePEP consortium has been created to study this novel modality of treatment in preparation for human trials. MePEP aims to assess the therapeutic effects of MSC administered ex vivo by NMP in the mechanisms of injury and repair in a porcine kidney autotransplantation model.

Mesenchymal stem cells secretome-induced axonal outgrowth is mediated by BDNF

Mesenchymal stem cells (MSCs) have been used for cell-based therapies in regenerative medicine, with increasing importance in central and peripheral nervous system repair. However, MSCs grafting present disadvantages, such as, a high number of cells required for transplantation and low survival rate when transplanted into the central nervous system (CNS). In line with this, MSCs secretome which present on its composition a wide range of molecules (neurotrophins, cytokines) and microvesicles, can be a solution to surpass these problems. However, the effect of MSCs secretome in axonal elongation is poorly understood. In this study, we demonstrate that application of MSCs secretome to both rat cortical and hippocampal neurons induces an increase in axonal length. In addition, we show that this growth effect is axonal intrinsic with no contribution from the cell body. To further understand which are the molecules required for secretome-induced axonal outgrowth effect, we depleted brain-derived neurotrophic factor (BDNF) from the secretome. Our results show that in the absence of BDNF, secretome-induced axonal elongation effect is lost and that axons present a reduced axonal growth rate. Altogether, our results demonstrate that MSCs secretome is able to promote axonal outgrowth in CNS neurons and this effect is mediated by BDNF.

Effect of the Microenvironment on Mesenchymal Stem Cell Paracrine Signaling: Opportunities to Engineer the Therapeutic Effect

Cues from the extracellular environment, including physical stimuli, are well known to affect mesenchymal stem cell (MSC) properties in terms of proliferation and differentiation. Many therapeutic strategies are now targeting this knowledge to increase the efficacy of cell therapies, typically employed to repair tissue functions in the event of injury, either by direct engraftment into the target tissue or differentiation into mature tissues. However, it is now envisioned that harnessing the repertoire of factors secreted by MSCs (termed the secretome) may provide an alternate to these cell therapies. Of current interest are both direct protein secretions and two major subpopulations of bioactive extracellular vesicles (EVs), namely exosomes and microvesicles. EVs released by MSCs are reflective of their cells of origin, able to impact upon the activities of other cells in the local microenvironment, making the rational design of MSC paracrine activities an encouraging strategy to reproducibly modulate cell therapies. The precise mechanisms by which the secretome is modulated by the microenvironment, however, remain elusive. Controlling MSC growth conditions with oxygen tension, growth factor composition, and mechanical properties may serve to directly influence paracrine activity. Our growing understanding implicates components of the mechanotransduction machinery in translating both mechanical and chemical cues from the environment into alterations in gene regulation and varied paracrine activity. As technologies are developed to manufacture MSCs, advances in bioengineering and novel insight of how the extracellular environment affects MSC paracrine activity will play a pivotal role in the generation of widespread, successful, clinical MSC therapies.

Blockade of Neuroglobin Reduces Protection of Conditioned Medium from Human Mesenchymal Stem Cells in Human Astrocyte Model (T98G) Under a Scratch Assay

Previous studies have indicated that paracrine factors (conditioned medium) increase wound closure and reduce reactive oxygen species in a traumatic brain injury in vitro model. Although the beneficial effects of conditioned medium from human adipose tissue-derived mesenchymal stem cells (hMSCA-CM) have been previously suggested for various neurological diseases, their actions on astrocytic cells are not well understood. In this study, we have explored the effect of hMSCA-CM on human astrocyte model (T98G cells) subjected to scratch assay. Our results indicated that hMSCA-CM improved cell viability, reduced nuclear fragmentation, attenuated the production of reactive oxygen species, and preserved mitochondrial membrane potential and ultrastructural parameters. In addition, hMSCA-CM upregulated neuroglobin in T98G cells and the genetic silencing of this protein prevented the protective action of hMSCA-CM on damaged cells, suggesting that neuroglobin is mediating, at least in part, the protective effect of hMSCA-CM. Overall, this evidence suggests that the use of hMSCA-CM is a promising therapeutic strategy for the protection of astrocytic cells in central nervous system (CNS) pathologies.

A Glycovariant of Human CD44 is Characteristically Expressed on Human Mesenchymal Stem Cells

The clinical effectiveness of systemically administered human mesenchymal stem cells (hMSCs) depends on their capacity to engage vascular endothelium. hMSCs derived from bone marrow (BM-hMSCs) natively lack endothelial binding capacity, but express a CD44 glycovariant containing N-linked sialyllactosamines that can be α(1,3)-fucosylated using fucosyltransferase-VI (FTVI) to enforce sLe^X decorations, thereby creating hematopoietic cell E-/L-selectin ligand (HCELL). HCELL expression programs potent shear-resistant adhesion of circulating cells to endothelial beds expressing E-selectin. An alternative source of hMSCs is adipose tissue (A-hMSCs), and we assessed whether A-hMSCs bind E-selectin and/or possess sialyllactosamine-decorated CD44 accessible to α(1,3)-fucosylation. Similar to BM-hMSCs, we found that A-hMSCs natively lack E-selectin ligands, but FTVI-mediated cell surface α(1,3)-fucosylation induces sLe^X expression and robust E-selectin binding secondary to conversion of CD44 into HCELL. Moreover, treatment with the α(1,3)-fucosyltransferase-FTVII also generated expression of HCELL on both BM-hMSCs and A-hMSCs, with sLe^X decorations created on N-linked glycans of the "standard" CD44 (CD44s) isoform. The finding that hMSCs from both source tissues each lack native E-selectin ligand expression prompted examination of the expression of glycosyltransferases that direct lactosaminyl glycan synthesis. These studies reveal that both types of hMSCs conspicuously lack transcripts encoding α(1,3)-fucosyltransferases, but equally express glycosyltransferases critical to creation of sialyllactosamines. Collectively, these data indicate that assembly of a sialyllactosaminyl-decorated CD44s glycovariant is a conserved feature of hMSCs derived from adipose tissue and marrow, thus identifying a CD44 glycosignature of these cells and supporting the applicability of cell surface α(1,3)-fucosylation in programming migration of systemically administered A-hMSCs to sites of tissue injury/inflammation. Stem Cells 2017;35:1080-1092.