Different Donors Mesenchymal Stromal Cells Secretomes Reveal Heterogeneous Profile of Relevance for Therapeutic Use

Therapeutic Effects of Mesenchymal Stem Cells Derived from Bone Marrow and Adipose Tissue in a Rat Model of Temporomandibular Osteoarthritis

OBJECTIVES

To examine the potential of intra-articular administration of mesenchymal stem cells (MSCs) derived from bone marrow or adipose tissue to mitigate synovial inflammation in a rat model of temporomandibular joint (TMJ) osteoarthritis (OA).

METHODS

In this experimental study, 40 rats were divided into 4 groups: (1) Control group; (2) Untreated TMJ-OA group; (3) TMJ-OA group treated with bone marrow-derived MSCs; (4) TMJ-OA group treated with adipose tissue-derived MSCs. The TMJ-OA model was established by inducing synovial inflammation through the intra-articular administration of complete Freund's adjuvant (CFA). After 8 weeks of TMJ-OA establishment, the animals were sacrificed and each mandibular condyle was extracted for histological evaluation.

RESULTS

The untreated TMJ-OA group had significantly higher synovial inflammation, as indicated microscopically by higher grades of synovial membrane hyperplasia and adhesion, vascular vasodilation, and fibrin deposition than the control group (p < 0.001). Both TMJ-OA groups treated with MSCs had lower grades of synovial inflammation and less severe synovitis than the untreated TMJ-OA group (p < 0.001). The TMJ-OA group treated with adipose tissue-derived MSCs showed lower grades of synovial membrane hyperplasia and higher grades of fibrin deposition than the that treated with bone marrow-derived MSCs (p < 0.001). Other indicators of synovial inflammation and synovitis severity were comparable between the two treatment groups.

CONCLUSIONS

Administration of CFA to the TMJ-OA rat model augmented synovial inflammation. Intra-articular administration of MSCs derived from either bone marrow or adipose tissue attenuated the microscopic manifestations of this inflammation, indicating the therapeutic potential of this treatment for TMJ-OA.

High throughput screening of mesenchymal stromal cell morphological response to inflammatory signals for bioreactor-based manufacturing of extracellular vesicles that modulate microglia

Due to their immunomodulatory function, mesenchymal stromal cells (MSCs) are a promising therapeutic with the potential to treat neuroinflammation associated with neurodegenerative diseases. This function is mediated by secreted extracellular vesicles (MSC-EVs). Despite established safety, MSC clinical translation has been unsuccessful due to inconsistent clinical outcomes resulting from functional heterogeneity. Current approaches to mitigate functional heterogeneity include 'priming' MSCs with inflammatory signals to enhance function. However, comprehensive evaluation of priming and its effects on MSC-EV function has not been performed. Furthermore, clinical translation of MSC-EV therapies requires significant manufacturing scale-up, yet few studies have investigated the effects of priming in bioreactors. As MSC morphology has been shown to predict their immunomodulatory function, we screened MSC morphological response to an array of priming signals and evaluated MSC-EV identity and potency in response to priming in flasks and bioreactors. We identified unique priming conditions corresponding to distinct morphologies. These conditions demonstrated a range of MSC-EV preparation quality and lipidome, allowing us to discover a novel MSC-EV manufacturing condition, as well as gain insight into potential mechanisms of MSC-EV microglia modulation. Our novel screening approach and application of priming to MSC-EV bioreactor manufacturing informs refinement of larger-scale manufacturing and enhancement of MSC-EV function.

The use of mesenchymal stromal cell secretome to enhance guided bone regeneration in comparison with leukocyte and platelet-rich fibrin

OBJECTIVES

Secretomes of mesenchymal stromal cells (MSC) represent a novel strategy for growth-factor delivery for tissue regeneration. The objective of this study was to compare the efficacy of adjunctive use of conditioned media of bone-marrow MSC (MSC-CM) with collagen barrier membranes vs. adjunctive use of conditioned media of leukocyte- and platelet-rich fibrin (PRF-CM), a current growth-factor therapy, for guided bone regeneration (GBR).

METHODS

MSC-CM and PRF-CM prepared from healthy human donors were subjected to proteomic analysis using mass spectrometry and multiplex immunoassay. Collagen membranes functionalized with MSC-CM or PRF-CM were applied on critical-size rat calvaria defects and new bone formation was assessed via three-dimensional (3D) micro-CT analysis of total defect volume (2 and 4 weeks) and 2D histomorphometric analysis of central defect regions (4 weeks).

RESULTS

While both MSC-CM and PRF-CM revealed several bone-related proteins, differentially expressed proteins, especially extracellular matrix components, were increased in MSC-CM. In rat calvaria defects, micro-CT revealed greater total bone coverage in the MSC-CM group after 2 and 4 weeks. Histologically, both groups showed a combination of regular new bone and 'hybrid' new bone, which was formed within the membrane compartment and characterized by incorporation of mineralized collagen fibers. Histomorphometry in central defect sections revealed greater hybrid bone area in the MSC-CM group, while the total new bone area was similar between groups.

CONCLUSION

Based on the in vitro and in vivo investigations herein, functionalization of membranes with MSC-CM represents a promising strategy to enhance GBR.

Mesenchymal Stem Cells: Their Role in the Tumor Microenvironment

Mesenchymal stem cells (MSCs) have been seen for years as great candidates for treating different diseases and an alternative to embryonic stem cells due to their differentiation capacity in vitro. More recent research has focused on their ability to modulate the immune response and regeneration at sites associated with inflammation, activities attributable to the release of trophic factors into the extracellular medium, a set of components known as the secretome. It has been possible to demonstrate the presence of these cells within the tumor microenvironment, which is associated with their tropism for sites of inflammation; however, their role here needs to be clarified. In different investigations, the feasibility of using MSCs or their secretome to treat cancer has been sought, with these results being ambiguous. It has been described that MSCs can be activated and present various phenotypes, which could explain the divergence in their action; however, these activation mechanisms and the different phenotypes still need to be well known. This review explores MSCs and their use in regenerative medicine with a targeted approach to cancer. Impact Statement This text addresses the diverging findings on the role of mesenchymal stem cells in the tumor microenvironment and discrepancies on the use of these cells as cancer treatment, separating the direct use of the cells from the use of the secretome. Multiple authors refer equally to the cells and their secretome to conclude on the positive or negative outcome, without taking into consideration how the cells are affected by their surroundings.

High throughput screening of mesenchymal stromal cell morphological response to inflammatory signals for bioreactor-based manufacturing of extracellular vesicles that modulate microglia

Due to their immunomodulatory function, mesenchymal stromal cells (MSCs) are a promising therapeutic with the potential to treat neuroinflammation associated with neurodegenerative diseases. This function can be mediated by secreted extracellular vesicles (MSC-EVs). Despite established safety, MSC clinical translation has been unsuccessful due to inconsistent clinical outcomes resulting from functional heterogeneity. Current approaches to mitigate functional heterogeneity include 'priming' MSCs with inflammatory signals to enhance function. However, comprehensive evaluation of priming and its effects on MSC-EV function has not been performed. Clinical translation of MSC-EV therapies requires significant manufacturing scale-up, yet few studies have investigated the effects of priming in bioreactors. As MSC morphology has been shown to predict their immunomodulatory function, we screened MSC morphological response to an array of priming signals and evaluated MSC-EV identity and potency in response to priming in flasks and bioreactors. We identified unique priming conditions corresponding to distinct morphologies. These conditions demonstrated a range of MSC-EV preparation quality and lipidome, allowing us to discover a novel MSC-EV manufacturing condition, as well as gain insight into potential mechanisms of MSC-EV microglia modulation. Our novel screening approach and application of priming to MSC-EV bioreactor manufacturing informs refinement of larger-scale manufacturing and enhancement of MSC-EV function.

Current status of the applications of conditioned media derived from mesenchymal stem cells for regenerative medicine

Recently published studies suggest that the paracrine substances released by mesenchymal stem cells (MSCs) are the primary motive behind the therapeutic action reported in these cells. Pre-clinical and clinical research on MSCs has produced promising outcomes. Furthermore, these cells are generally safe for therapeutic use and may be extracted from a variety of anatomical regions. Recent research has indicated, however, that transplanted cells do not live long and that the advantages of MSC treatment may be attributable to the large diversity of bioactive substances they create, which play a crucial role in the control of essential physiological processes. Secretome derivatives, such as conditioned media or exosomes, may provide significant benefits over cells in terms of manufacture, preservation, handling, longevity of the product, and potential as a ready-to-use biologic product. Despite their immunophenotypic similarities, the secretome of MSCs appears to vary greatly depending on the host's age and the niches in which the cells live. The secretome's effect on multiple biological processes such as angiogenesis, neurogenesis, tissue repair, immunomodulation, wound healing, anti-fibrotic, and anti-tumor for tissue maintenance and regeneration has been discovered. Defining the secretome of cultured cultivated MSC populations by conditioned media analysis will allow us to assess its potential as a novel treatment approach. This review will concentrate on accumulating data from pre-clinical and clinical trials pointing to the therapeutic value of the conditioned medium. At last, the necessity of characterizing the conditioned medium for determining its potential for cell-free treatment therapy will be emphasized in this study.

Towards the Standardization of Mesenchymal Stem Cell Secretome-Derived Product Manufacturing for Tissue Regeneration

Mesenchymal stem cell secretome or conditioned medium (MSC-CM) is a combination of biomolecules and growth factors in cell culture growth medium, secreted by mesenchymal stem cells (MSCs), and the starting point of several derived products. MSC-CM and its derivatives could be applied after injuries and could mediate most of the beneficial regenerative effects of MSCs without the possible side effects of using MSCs themselves. However, before the clinical application of these promising biopharmaceuticals, several issues such as manufacturing protocols and quality control must be addressed. This review aims to underline the influence of the procedure for conditioned medium production on the quality of the secretome and its derivatives and highlights the questions considering cell sources and donors, cell expansion, cell passage number and confluency, conditioning period, cell culture medium, microenvironment cues, and secretome-derived product purification. A high degree of variability in MSC secretomes is revealed based on these parameters, confirming the need to standardize and optimize protocols. Understanding how bioprocessing and manufacturing conditions interact to determine the quantity, quality, and profile of MSC-CM is essential to the development of good manufacturing practice (GMP)-compliant procedures suitable for replacing mesenchymal stem cells in regenerative medicine.

Development and characterization of Factor Xa-responsive materials for applications in cell culture and biologics delivery

Stimuli-responsive biomaterials may be used to better control the release of bioactive molecules or cells for applications involving drug delivery and controlled cell release. In this study, we developed a Factor Xa (FXa)-responsive biomaterial capable of controlled release of pharmaceutical agents and cells from in vitro culture. FXa-cleavable substrates were formed as hydrogels that degraded in response to FXa enzyme over several hours. Hydrogels were shown to release both heparin and a model protein in response to FXa. Additionally, RGD-functionalized FXa-degradable hydrogels were used to culture mesenchymal stromal cells (MSCs), enabling FXa-mediated cell dissociation from hydrogels in a manner that preserved multicellular structures. Harvesting MSCs using FXa-mediated dissociation did not influence their differentiation capacity or indoleamine 2,3-dioxygenase (IDO) activity (a measure of immunomodulatory capacity). In all, this FXa-degradable hydrogel is a novel responsive biomaterial system that may be used for on-demand drug delivery, as well as for improving processes for in vitro culture of therapeutic cells.

Mesenchymal stem cell-derived secretome enhances nucleus pulposus cell metabolism and modulates extracellular matrix gene expression in vitro

Introduction: Intradiscal mesenchymal stromal cell (MSC) therapies for intervertebral disc degeneration (IDD) have been gaining increasing interest due to their capacity to ameliorate intervertebral disc metabolism and relieve low back pain (LBP). Recently, novel investigations have demonstrated that most of MSC anabolic effects are exerted by secreted growth factors, cytokines, and extracellular vesicles, collectively defined as their secretome. In this study, we aimed to evaluate the effect of bone-marrow-MSCs (BM-MSCs) and adipose-derived stromal cells (ADSCs) secretomes on human nucleus pulposus cells (hNPCs) in vitro.

Methods: BM-MSCs and ADSCs were characterized according to surface marker expression by flow cytometry and multilineage differentiation by Alizarin red, Red Oil O and Alcian blue staining. After isolation, hNPCs were treated with either BM-MSC secretome, ADSC secretome, interleukin (IL)-1β followed by BM-MSC secretome or IL-1β followed by ADSC secretome. Cell metabolic activity (MTT assay), cell viability (LIVE/DEAD assay), cell content, glycosaminoglycan production (1,9-dimethylmethylene blue assay), extracellular matrix and catabolic marker gene expression (qPCR) were assessed.

Results: 20% BM-MSC and ADSC secretomes (diluted to normal media) showed to exert the highest effect towards cell metabolism and were then used in further experiments. Both BM-MSC and ADSC secretomes improved hNPC viability, increased cell content and enhanced glycosaminoglycan production in basal conditions as well as after IL-1β pretreatment. BM-MSC secretome significantly increased ACAN and SOX9 gene expression, while reducing the levels of IL6, MMP13 and ADAMTS5 both in basal conditions and after in vitro inflammation with IL-1β. Interestingly, under IL-1β stimulation, ADSC secretome showed a catabolic effect with decreased extracellular matrix markers and increased levels of pro-inflammatory mediators.

Discussion: Collectively, our results provide new insights on the biological effect of MSC-derived secretomes on hNPCs, with intriguing implications on the development of cell-free approaches to treat IDD.

Comparative analysis of the potential of the secretomes of cardiac resident stromal cells and fibroblasts

The secretome of different cell types has been applied on in vitro and in vivo assays, indicating considerable therapeutic potential. However, the choice of the ideal cell type and culture conditions for obtaining the best set of soluble factors, as well as the assays to assess specific effects, remain subjects of vigorous debate. In this study, we used mass spectrometry to characterize the secretomes of ventricle derived-cardiac resident stromal cells (vCRSC) and human dermal fibroblasts (HDFs) and evaluate them in an effort to understand the niche specificity of biological responses toward different cellular behaviors, such as cell proliferation, adhesion, migration, and differentiation. It was interesting to note that the HDF and vCRSC secretomes were both able to induce proliferation and cardiac differentiation of H9c2 cells, as well as to increase the adhesion activity of H9c2 cells and human umbilical vein endothelial cells. Analysis of the secretome composition showed that the vCRSCs derived from different donors secreted a similar set of proteins. Despite the differences, almost half of the proteins identified in conditioned medium were common to both HDF and vCRSC. Consequently, a high number of common biological processes were identified in the secretomes of the two cell types, which could help to explain the similar results observed in the in vitro assays. We show that soluble factors secreted by both HDF and vCRSC are able to promote proliferation and differentiation of cardiomyoblasts in vitro. Our study indicates the possible use of vCRSC or HDF secretomes in acellular therapies for regenerative medicine.

Potential applications of mesenchymal stem cells and their derived exosomes in regenerative medicine

INTRODUCTION

Regenerative medicine involves the replacement of damaged cells, tissues, or organs to restore normal function. Mesenchymal stem cells (MSCs) and exosomes secreted by MSCs have unique advantages that make them a suitable candidate in the field of regenerative medicine.

AREAS COVERED

This article provides a comprehensive overview of regenerative medicine, focusing on the use of MSCs and their exosomes as potential therapies for replacing damaged cells, tissues, or organs. This article discusses the distinct advantages of both MSCs and their secreted exosomes, including their immunomodulatory effects, lack of immunogenicity, and recruitment to damaged areas. While both MSCs and exosomes have these advantages, MSCs also have the unique ability to self-renew and differentiate. This article also assesses the current challenges associated with the application of MSCs and their secreted exosomes in therapy. We have reviewed proposed solutions for improving MSC or exosome therapy, including ex-vivo preconditioning strategies, genetic modification, and encapsulation. Literature search was conducted using Google Scholar and PubMed databases.

EXPERT OPINION

Providing insight into the future development of MSC and exosome-based therapies and to encourage the scientific community to focus on the identified gaps, develop appropriate guidelines, and enhance the clinical application of these therapies.

Bone marrow-derived mesenchymal stem cell-conditioned medium ameliorates diabetic foot ulcers in rats

OBJECTIVES

This study aimed to explore the effects of bone marrow-derived Mesenchymal Stem Cell-Conditioned Medium (MSC-CM) treating diabetic foot ulcers in rats.

METHODS

Models of T2DM rats were induced by a high-fat diet and intraperitoneal injection of STZ in SD rats. Models of Diabetic Foot Ulcers (DFUs) were made by operation on hind limbs in diabetic rats. Rats were divided into four groups (n = 6 for each group), i.e., Normal Control group (NC), Diabetes Control group (DM-C), MSC-CM group and Mesenchymal Stem Cells group (MSCs). MSC-CM group was treated with an injection of conditioned medium derived from preconditioned rats' bone marrow MSCs around ulcers. MSCs group were treated with an injection of rats' bone marrow MSCs. The other two groups were treated with an injection of PBS. After the treatment, wound closure, re-epithelialization (thickness of the stratum granulosums of the skin, by H&E staining), cell proliferation (Ki67, by IHC), angiogenesis (CD31, by IFC), autophagy (LC3B, by IFC and WB; autolysosome, by EM) and pyroptosis (IL-1β, NLRP3, Caspase-1, GSDMD and GSDMD-N, by WB) in ulcers were evaluated.

RESULTS

After the treatment wound area rate, IL-1β by ELISA, and IL-1β, Caspase-1, GSDMD and GSDMD-N by WB of MSC-CM group were less than those of DM group. The thickness of the stratum granulosums of the skin, proliferation index of Ki67, mean optic density of CD31 and LC3B by IFC, and LC3B by WB of MSC-CM group were more than those of DM group. The present analysis demonstrated that the injection of MSC-CM into rats with DFUs enhanced the wound-healing process by accelerating wound closure, promoting cell proliferation and angiogenesis, enhancing cell autophagy, and reducing cell pyroptosis in ulcers.

CONCLUSIONS

Studies conducted indicate that MSC-CM administration could be a novel cell-free therapeutic approach to treat DFUs accelerating the wound healing process and avoiding the risk of living cells therapy.

Role of Mesenchymal Stem Cells and Their Paracrine Mediators in Macrophage Polarization: An Approach to Reduce Inflammation in Osteoarthritis

Osteoarthritis (OA) is a low-grade inflammatory disorder of the joints that causes deterioration of the cartilage, bone remodeling, formation of osteophytes, meniscal damage, and synovial inflammation (synovitis). The synovium is the primary site of inflammation in OA and is frequently characterized by hyperplasia of the synovial lining and infiltration of inflammatory cells, primarily macrophages. Macrophages play a crucial role in the early inflammatory response through the production of several inflammatory cytokines, chemokines, growth factors, and proteinases. These pro-inflammatory mediators are activators of numerous signaling pathways that trigger other cytokines to further recruit more macrophages to the joint, ultimately leading to pain and disease progression. Very few therapeutic alternatives are available for treating inflammation in OA due to the condition's low self-healing capacity and the lack of clear diagnostic biomarkers. In this review, we opted to explore the immunomodulatory properties of mesenchymal stem cells (MSCs) and their paracrine mediators-dependent as a therapeutic intervention for OA, with a primary focus on the practicality of polarizing macrophages as suppression of M1 macrophages and enhancement of M2 macrophages can significantly reduce OA symptoms.

Comparison of Muscle Regeneration after BMSC-Conditioned Medium, Syngeneic, or Allogeneic BMSC Injection

For many years optimal treatment for dysfunctional skeletal muscle characterized, for example, by impaired or limited regeneration, has been searched. Among the crucial factors enabling its development is finding the appropriate source of cells, which could participate in tissue reconstruction or serve as an immunomodulating agent (limiting immune response as well as fibrosis, that is, connective tissue formation), after transplantation to regenerating muscles. MSCs, including those derived from bone marrow, are considered for such applications in terms of their immunomodulatory properties, as their naive myogenic potential is rather limited. Injection of autologous (syngeneic) or allogeneic BMSCs has been or is currently being tested and compared in many potential clinical treatments. In the present study, we verified which approach, that is, the transplantation of either syngeneic or allogeneic BMSCs or the injection of BMSC-conditioned medium, would be the most beneficial for skeletal muscle regeneration. To properly assess the influence of the tested treatments on the inflammation, the experiments were carried out using immunocompetent mice, which allowed us to observe immune response. Combined analysis of muscle histology, immune cell infiltration, and levels of selected chemokines, cytokines, and growth factors important for muscle regeneration, showed that muscle injection with BMSC-conditioned medium is the most beneficial strategy, as it resulted in reduced inflammation and fibrosis development, together with enhanced new fiber formation, which may be related to, i.e., elevated level of IGF-1. In contrast, transplantation of allogeneic BMSCs to injured muscles resulted in a visible increase in the immune response, which hindered regeneration by promoting connective tissue formation. In comparison, syngeneic BMSC injection, although not detrimental to muscle regeneration, did not result in such significant improvement as CM injection.

Dynamic Culture of Mesenchymal Stromal/Stem Cell Spheroids and Secretion of Paracrine Factors

In recent years, conditioned medium (CM) obtained from the culture of mesenchymal stromal/stem cells (MSCs) has been shown to effectively promote tissue repair and modulate the immune response in vitro and in different animal models, with potential for application in regenerative medicine. Using CM offers multiple advantages over the implantation of MSCs themselves: 1) simpler storage, transport, and preservation requirements, 2) avoidance of the inherent risks of cell transplantation, and 3) potential application as a ready-to-go biologic product. For these reasons, a large amount of MSCs research has focused on the characterization of the obtained CM, including soluble trophic factors and vesicles, preconditioning strategies for enhancing paracrine secretion, such as hypoxia, a three-dimensional (3D) environment, and biochemical stimuli, and potential clinical applications. In vitro preconditioning strategies can increase the viability, proliferation, and paracrine properties of MSCs and therefore improve the therapeutic potential of the cells and their derived products. Specifically, dynamic cultivation conditions, such as fluid flow and 3D aggregate culture, substantially impact cellular behaviour. Increased levels of growth factors and cytokines were observed in 3D cultures of MSC grown on orbital or rotatory shaking platforms, in stirred systems, such as spinner flasks or stirred tank reactors, and in microgravity bioreactors. However, only a few studies have established dynamic culture conditions and protocols for 3D aggregate cultivation of MSCs as a scalable and reproducible strategy for CM production. This review summarizes significant advances into the upstream processing, mainly the dynamic generation and cultivation of MSC aggregates, for de CM manufacture and focuses on the standardization of the soluble factor production.

Interaction of Neural Stem Cells (NSCs) and Mesenchymal Stem Cells (MSCs) as a Promising Approach in Brain Study and Nerve Regeneration

Rapid developments in stem cell research in recent years have provided a solid foundation for their use in medicine. Over the last few years, hundreds of clinical trials have been initiated in a wide panel of indications. Disorders and injuries of the nervous system still remain a challenge for the regenerative medicine. Neural stem cells (NSCs) are the optimal cells for the central nervous system restoration as they can differentiate into mature cells and, most importantly, functional neurons and glial cells. However, their application is limited by multiple factors such as difficult access to source material, limited cells number, problematic, long and expensive cultivation in vitro, and ethical considerations. On the other hand, according to the available clinical databases, most of the registered clinical trials involving cell therapies were carried out with the use of mesenchymal stem/stromal/signalling cells (MSCs) obtained from afterbirth or adult human somatic tissues. MSCs are the multipotent cells which can also differentiate into neuron-like and glia-like cells under proper conditions in vitro; however, their main therapeutic effect is more associated with secretory and supportive properties. MSCs, as a natural component of cell niche, affect the environment through immunomodulation as well as through the secretion of the trophic factors. In this review, we discuss various therapeutic strategies and activated mechanisms related to bilateral MSC–NSC interactions, differentiation of MSCs towards the neural cells (subpopulation of crest-derived cells) under the environmental conditions, bioscaffolds, or co-culture with NSCs by recreating the conditions of the neural cell niche.

Immortalized Mesenchymal Stem Cells: A Safe Cell Source for Cellular or Cell Membrane-Based Treatment of Glioma

Mesenchymal stem cells (MSCs) have emerged as putative therapeutic tools due to their intrinsic tumor tropism, and anti-tumor and immunoregulatory properties. The limited passage and self-differentiation abilities of MSCs in vitro hinder preclinical studies on them. In this study, we focused on the safety of immortalized mesenchymal stem cells (im-MSCs) and, for the first time, studied the feasibility of im-MSCs as candidates for the treatment of glioma. The im-MSCs were constructed by lentiviral transfection of genes. The proliferative capacity of im-MSCs and the proliferative phenotype of MSCs and MSCs co-cultured with glioma cells (U87) were measured using CCK-8 or EdU assays. After long-term culture, karyotyping of im-MSCs was conducted. The tumorigenicity of engineered MSCs was evaluated using soft agar cloning assays. Next, the engineered cells were injected into the brain of female BALB/c nude mice. Finally, the cell membranes of im-MSCs were labeled with DiO or DiR to detect their ability to be taken up by glioma cells and target in situ gliomas using the IVIS system. Engineered cells retained the immunophenotype of MSC; im-MSCs maintained the ability to differentiate into mesenchymal lineages in vitro; and im-MSCs showed stronger proliferative capacity than unengineered MSCs but without colony formation in soft agar, no tumorigenicity in the brain, and normal chromosomes. MSCs or im-MSCs co-cultured with U87 cells showed enhanced proliferation ability, but did not show malignant characteristics in vitro. Immortalized cells continued to express homing molecules. The cell membranes of im-MSCs were taken up by glioma cells and targeted in situ gliomas in vivo, suggesting that im-MSCs and their plasma membranes can be used as natural drug carriers for targeting gliomas, and providing a safe, adequate, quality-controlled, and continuous source for the treatment of gliomas based on whole-cell or cell membrane carriers.

The Secretome of Preconditioned Mesenchymal Stem Cells Drives Polarization and Reprogramming of M2a Macrophages toward an IL-10-Producing Phenotype

The preconditioning of mesenchymal stem cells (MSCs) has been recognized as an attractive tool to improve their regenerative and immunomodulatory capacities based on their paracrine effects. In this study, we examined the potential of an MSC-conditioned medium (MSC-CM) to alter the phenotype of murine macrophages and to drive reprogramming toward an anti-inflammatory, M2-like state in vitro. We further explored the impact of MSC cytokine preconditioning on the immunosuppressive properties of the MSC secretome. The MSC-CM suppressed the expression of proinflammatory genes in murine M1 macrophages, but only the CM from preconditioned MSCs (preMSC-CM) downregulated their expression during M1 polarization. Remarkably, only the preMSC-CM significantly increased the expression of M2a-, M2b- and M2c-specific genes and proteins during M2a polarization. Further, macrophages were found to secrete high levels of anti-inflammatory IL-10. Similarly, M2a macrophages cultured in the presence of the preMSC-CM displayed an enhanced expression of M2b/M2c-specific markers, suggesting that the secretome of preMSC promotes the repolarization of M2a-like macrophages to M2b/M2c subtypes. The preMSC-CM was found to be enriched in molecules involved in M2 polarization. Additionally, a unique downregulation of extracellular matrix components was observed. Altogether, the preMSC-CM may provide an attractive strategy to dampen inflammation by suppressing the expression of proinflammatory mediators and promoting the polarization and phenotype switch of M2a cells to IL-10-secreting M2b/M2c-like macrophages.

Equilibrium among Inflammatory Factors Determines Human MSC-Mediated Immunosuppressive Effect

Mesenchymal stem cells (MSCs) are thought to be a promising therapeutic agent due to their multiple paracrine and immunomodulatory properties, providing protection from chronic inflammation and promoting tissue repair. MSCs can regulate the balance of pro-inflammatory and anti-inflammatory factors in inflamed tissues, creating a microenvironment necessary for successful healing; however, their interactions with immune cells are still poorly studied. We examined the temporal and spatial changes in gene regulation and the paracrine milieu accompanying the MSC-mediated immunosuppression effect in mixed cultures with activated peripheral blood mononuclear cells (PBMCs). Our data reveal that the peak of suppression of PBMC proliferation was achieved within 48 h following co-culture with MSCs and subsequently did not undergo a significant change. This effect was accompanied by an increase in COX-2 expression and an induction of IDO synthesis in MSCs. At this point, the expression of IL-1, IL-6, IL-8, IFN-γ, MCP-1, and G-CSF was upregulated in co-cultured cells. On the contrary, we observed a decrease in the concentrations of IL-10, IL-13, IL-5, and MIP-1b in co-culture supernatants compared to intact cultures of activated PBMCs. The regulation of IDO, IL-1, IL-6, and G-CSF production was accomplished with the involvement of direct cell-cell contact between MSCs and PBMCs. These findings provide new insights into the use of potential precondition inducers or their combinations to obtain functionally qualified MSCs for more effective treatment of inflammatory diseases.

Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells and Their Contribution to Angiogenic Processes in Tissue Regeneration

Mesenchymal stem/stromal cells (MSCs) are widely described in the context of their regenerative and immunomodulatory activity. MSCs are isolated from various tissues and organs. The most frequently described sources are bone marrow and adipose tissue. As stem cells, MSCs are able to differentiate into other cell lineages, but they are usually reported with respect to their paracrine potential. In this review, we focus on MSCs derived from adipose tissue (AT-MSCs) and their secretome in regeneration processes. Special attention is given to the contribution of AT-MSCs and their derivatives to angiogenic processes described mainly in the context of angiogenic dysfunction. Finally, we present clinical trials registered to date that concern the application of AT-MSCs and their secretome in various medical conditions.

Dental Mesenchymal Stem Cell Secretome: An Intriguing Approach for Neuroprotection and Neuroregeneration

Mesenchymal stem cells (MSCs) are known for their beneficial effects and regenerative potential. In particular, dental-derived MSCs have the advantage of easier accessibility and a non-invasive isolation method. Moreover, thanks to their neural crest origin, dental MSCs seem to have a more prominent neuroregenerative potential. Indeed, in basal conditions they also express neuronal markers. However, it is now well known that the beneficial actions of MSCs depend, at least in part, on their secretome, referring to all the bioactive molecules released in the conditioned medium (CM) or in extracellular vesicles (EVs). In this review we focus on the applications of the secretome derived from dental MSCs for neuroregeneration and neuroprotection. The secretomes of different dental MSCs have been tested for their effects for neuroregenerative purposes, and the secretomes of dental pulp stem cells and stem cells from human exfoliated deciduous teeth are the most studied. Both the CM and EVs obtained from dental MSCs showed that they are able to promote neurite outgrowth and neuroprotective effects. Interestingly, dental-derived MSC secretome showed stronger neuroregenerative and neuroprotective effects compared to that obtained from other MSC sources. For these reasons, the secretome obtained from dental MSCs may represent a promising approach for neuroprotective treatments.

Regenerative Potential of Mesenchymal Stem Cells' (MSCs) Secretome for Liver Fibrosis Therapies

Chronic liver injuries lead to liver fibrosis and then to end-stage liver cirrhosis. Liver transplantation is often needed as a course of treatment for patients in critical conditions, but limitations associated with transplantation prompted the continuous search for alternative therapeutic strategies. Cell therapy with stem cells has emerged as an attractive option in order to stimulate tissue regeneration and liver repair. Transplanted mesenchymal stem cells (MSCs) could trans-differentiate into hepatocyte-like cells and, moreover, show anti-fibrotic and immunomodulatory effects. However, cell transplantation may lead to some uncontrolled side effects, risks associated with tumorigenesis, and cell rejection. MSCs' secretome includes a large number of soluble factors and extracellular vesicles (EVs), through which they exert their therapeutic role. This could represent a cell-free strategy, which is safer and more effective than MSC transplantation. In this review, we focus on cell therapies based on MSCs and how the MSCs' secretome impacts the mechanisms associated with liver diseases. Moreover, we discuss the important therapeutic role of EVs and how their properties could be further used in liver regeneration.

MSC Secretome as a Promising Tool for Neuroprotection and Neuroregeneration in a Model of Intracerebral Hemorrhage

Multipotent mesenchymal stromal cells (MSCs) are considered to be critical contributors to injured tissue repair and regeneration, and MSC-based therapeutic approaches have been applied to many peripheral and central neurologic disorders. It has been demonstrated that the beneficial effects of MSC are mainly mediated by the components of their secretome. In the current study, we have explored the neuroprotective potential of the MSC secretome in a rat model of intracerebral hemorrhage and shown that a 10-fold concentrated secretome of human MSC and its combination with the brain-derived neurotrophic factor (BDNF) provided a better survival and neurological outcome of rats within 14 days of intracerebral hemorrhage compared to the negative (non-treated) and positive (BDNF) control groups. We found that it was due to the ability of MSC secretome to stimulate neuron survival under conditions of glutamate-induced neurotoxicity. However, the lesion volume did not shrink in these rats, and this also correlated with prominent microglia activation. We hypothesize that this could be caused by the species-specificity of the used MSC secretome and provide evidence to confirm this. Thus, we have found that allogenic rat MSC secretome was more effective than xenogenic human MSC secretome in the rat intracerebral hemorrhage model: it reduced the volume of the lesion and promoted excellent survival and neurological outcome of the treated rats.

Local and Remote Effects of Mesenchymal Stem Cell Administration on Skin Wound Regeneration

Wound healing is an important medical problem. We evaluated the efficacy of locally administered mesenchymal stem cells (MSCs) isolated from human umbilical cords on the dynamics of skin wound healing. The study was conducted on the backs of Wistar rats, where two square wounds were created by removing all layers of the skin. Four groups were studied in two series of experiments: (1) a Control_NaCl group (the wounds were injected with 0.9% NaCl solution) and a Control_0 group (intact wounds on the opposite side of the same rat's back); (2) an MSC group (injected MSCs, local effect) and a Control_sc group (intact wounds on the opposite side of the back, remote MSC effect). The area and temperature of the wounds and the microcirculation of the wound edges were measured. Histological and morphometric studies were performed on days 3 and 7 after the wounds were created. The results showed that the injection trauma (Control_NaCl) slowed the regeneration process. In both MSC groups (unlike in either control group), we observed no increase in the area of the wounds; in addition, we observed inhibition of the inflammatory process and improved wound regeneration on days 1-3 in the remote group and days 1-5 in the local (injected) group. The MSC and Control_sc groups demonstrated improved microcirculation and suppression of leukocyte infiltration on day 3. On day 7, all the studied parameters of the wounds of the Control_0 group were the same as those of the wounds that received cell therapy, although in contrast to the results of the Control_ NaCl group, fibroblast proliferation was greater in the MSC and Control_sc groups. The dynamics of the size of the wounds were comparable for both local and remote application of MSCs. Thus, even a one-time application of MSCs was effective during the first 3-5 days after injury due to anti-inflammatory processes, which improved the regeneration process. Remote application of MSC, as opposed to direct injection, is advisable, especially in the case of multiple wounds, since the results were indistinguishable between the groups and injection trauma was shown to slow healing.

Soluble factors of mesenchimal stem cells (FS-MSC) as a potential tool to reduce inflammation in donor's lungs after hypovolemic shock

OBJECTIVE

The shortage of viable lungs is still a major obstacle for transplantation. Trauma victims who represent potential lung donors commonly present hypovolemic shock leading to pulmonary inflammation and deterioration and rejection after transplantation. Seeking to improve lung graft, new approaches to donor treatment have been tested. This study focuses on treatment with mesenchymal stem cells (MSCs) or soluble factors produced by MSCs (FS-MSC) using a rat model for lung donors after hemorrhagic shock.

METHODS

Forty-eight rats were divided into four groups: Sham (n=12), animals without induction of hypovolemic shock; Shock (n=12), animals submitted to hypovolemic shock (mean arterial pressure 40 mmHg); MSC (n=12), animals submitted to hypovolemic shock and treated with MSCs, and FS (n=12), animals submitted to hypovolemic shock and treated with FS-MSC. The animals were subjected to a 50-minute hypovolemic shock (40 mmHg) procedure. The treated animals were monitored for 115 minutes. We performed histopathology of lung tissue and quantification of inflammatory markers (TNF-α, IL-1β, IL-6, IL-10, iCAM and vCAM) in lung tissue and peripheral blood leukocytes (PBLs).

RESULTS

Hemorrhagic shock resulted in higher PBLs and neutrophil infiltrate in the lungs. FS animals had lower neutrophil density comparing with Shock and MSC animals (p<0.001). No differences in the cytokine levels in lung tissue were observed between the groups.

CONCLUSIONS

The lungs of rats submitted to hemorrhagic shock and treated with FS-MSC showed reduced inflammation indicated in a decrease in lung neutrophil infiltrate.

Neurogenic and Neuroprotective Potential of Stem/Stromal Cells Derived from Adipose Tissue

Currently, the number of stem-cell based experimental therapies in neurological injuries and neurodegenerative disorders has been massively increasing. Despite the fact that we still have not obtained strong evidence of mesenchymal stem/stromal cells’ neurogenic effectiveness in vivo, research may need to focus on more appropriate sources that result in more therapeutically promising cell populations. In this study, we used dedifferentiated fat cells (DFAT) that are proven to demonstrate more pluripotent abilities in comparison with standard adipose stromal cells (ASCs). We used the ceiling culture method to establish DFAT cells and to optimize culture conditions with the use of a physioxic environment (5% O₂). We also performed neural differentiation tests and assessed the neurogenic and neuroprotective capability of both DFAT cells and ASCs. Our results show that DFAT cells may have a better ability to differentiate into oligodendrocytes, astrocytes, and neuron-like cells, both in culture supplemented with N21 and in co-culture with oxygen–glucose-deprived (OGD) hippocampal organotypic slice culture (OHC) in comparison with ASCs. Results also show that DFAT cells have a different secretory profile than ASCs after contact with injured tissue. In conclusion, DFAT cells constitute a distinct subpopulation and may be an alternative source in cell therapy for the treatment of nervous system disorders.

Inhibition of Human Malignant Pleural Mesothelioma Growth by Mesenchymal Stromal Cells

BACKGROUND

Malignant Pleural Mesothelioma (MPM) is an aggressive tumor that has a significant incidence related to asbestos exposure with no effective therapy and poor prognosis. The role of mesenchymal stromal cells (MSCs) in cancer is controversial due to their opposite effects on tumor growth and in particular, only a few data are reported on MSCs and MPM.

METHODS

We investigated the in vitro efficacy of adipose tissue-derived MSCs, their lysates and secretome against different MPM cell lines. After large-scale production of MSCs in a bioreactor, their efficacy was also evaluated on a human MPM xenograft in mice.

RESULTS

MSCs, their lysate and secretome inhibited MPM cell proliferation in vitro with S or G0/G1 arrest of the cell cycle, respectively. MSC lysate induced cell death by apoptosis. The efficacy of MSC was confirmed in vivo by a significant inhibition of tumor growth, similar to that produced by systemic administration of paclitaxel. Interestingly, no tumor progression was observed after the last MSC treatment, while tumors started to grow again after stopping chemotherapeutic treatment.

CONCLUSIONS

These data demonstrated for the first time that MSCs, both through paracrine and cell-to-cell interaction mechanisms, induced a significant inhibition of human mesothelioma growth. Since the prognosis for MPM patients is poor and the options of care are limited to chemotherapy, MSCs could provide a potential new therapeutic approach for this malignancy.

Mesenchymal Stromal Cells and Their Secretome: New Therapeutic Perspectives for Skeletal Muscle Regeneration

Mesenchymal stromal cells (MSCs) are multipotent cells found in different tissues: bone marrow, peripheral blood, adipose tissues, skeletal muscle, perinatal tissues, and dental pulp. MSCs are able to self-renew and to differentiate into multiple lineages, and they have been extensively used for cell therapy mostly owing to their anti-fibrotic and immunoregulatory properties that have been suggested to be at the basis for their regenerative capability. MSCs exert their effects by releasing a variety of biologically active molecules such as growth factors, chemokines, and cytokines, either as soluble proteins or enclosed in extracellular vesicles (EVs). Analyses of MSC-derived secretome and in particular studies on EVs are attracting great attention from a medical point of view due to their ability to mimic all the therapeutic effects produced by the MSCs (i.e., endogenous tissue repair and regulation of the immune system). MSC-EVs could be advantageous compared with the parental cells because of their specific cargo containing mRNAs, miRNAs, and proteins that can be biologically transferred to recipient cells. MSC-EV storage, transfer, and production are easier; and their administration is also safer than MSC therapy. The skeletal muscle is a very adaptive tissue, but its regenerative potential is altered during acute and chronic conditions. Recent works demonstrate that both MSCs and their secretome are able to help myofiber regeneration enhancing myogenesis and, interestingly, can be manipulated as a novel strategy for therapeutic interventions in muscular diseases like muscular dystrophies or atrophy. In particular, MSC-EVs represent promising candidates for cell free-based muscle regeneration. In this review, we aim to give a complete picture of the therapeutic properties and advantages of MSCs and their products (MSC-derived EVs and secreted factors) relevant for skeletal muscle regeneration in main muscular diseases.

Transplantation of Dystrophin Expressing Chimeric Human Cells of Myoblast/Mesenchymal Stem Cell Origin Improves Function in Duchenne Muscular Dystrophy Model

Duchenne muscular dystrophy (DMD) is a lethal X-linked disorder caused by mutations in dystrophin gene. Currently, there is no cure for DMD. Cell therapies are challenged by limited engraftment and rejection. Thus, more effective and safer therapeutic approaches are needed for DMD. We previously reported increased dystrophin expression correlating with improved function after transplantation of dystrophin expressing chimeric (DEC) cells of myoblast origin in the mdx mouse models of DMD. This study established new DEC cell line of myoblasts and mesenchymal stem cells (MSC) origin and tested its efficacy and therapeutic potential in mdx/scid mouse model of DMD. Fifteen ex vivo cell fusions of allogenic human myoblast [normal myoblasts (MBN)] and normal human bone marrow-derived MSC (MSCN) from normal donors were performed using polyethylene glycol. Flow cytometry, confocal microscopy, polymerase chain reaction (PCR)-short tandem repeats, polymerase chain reaction-reverse sequence-specific oligonucleotide probe assessed chimeric state of fused MBN/MSCN DEC cells, whereas Comet assay assessed fusion procedure safety testing genotoxicity. Immunofluorescence and real-time PCR assessed dystrophin expression and myogenic differentiation. Mixed lymphocyte reaction (MLR) evaluated DEC's immunogenicity. To test MBN/MSCN DEC efficacy in vivo, gastrocnemius muscle of mdx/scid mice were injected with vehicle (n = 12), nonfused MBN and MSCN (n = 9, 0.25 × 106/each) or MBN/MSCN DEC (n = 9, 0.5 × 106). Animals were evaluated for 90 days using ex vivo and in vivo muscle strength tests. Histology and immunofluorescence staining assessed dystrophin expression, centrally nucleated fibers and scar tissue formation. Post-fusion, MBN/MSCN DEC chimeric state, myogenic differentiation, and dystrophin expression were confirmed. MLR reveled reduced DEC's immune response compared with controls (P < 0.05). At 90 days post-DEC transplant, increase in dystrophin expression (20.26% ± 2.5%, P < 0.05) correlated with improved muscle strength and function in mdx/scid mice. The created human MBN/MSCN DEC cell line introduces novel therapeutic approach combining myogenic and immunomodulatory properties of MB and MSC, and as such may open a universal approach for muscle regeneration in DMD.

Stem Cell-Derived Exosomes as Therapeutic Approach for Neurodegenerative Disorders: From Biology to Biotechnology

The aging population has contributed to the rapid rise in the global incidence of neurodegenerative diseases. Despite the medical advances, there are no effective treatments for these disorders. Therefore, there is an urgent need for new treatments for these diseases. In this sense, cell therapy has been recognized as the best candidate for treating incurable diseases, such as neurodegenerative disorders. However, the therapeutic use of these cells can be limited by several factors. Thus, there has been a rediscovery that extracellular vesicles, including exosomes, can be alternatively explored in the treatment of these diseases, overcoming the limits of cell-based therapy. In this sense, this review aims to revisit all areas from biology, including biogenesis and the content of exosomes, to biotechnology, proposing the minimal information required to isolate, characterize, and study the content of these vesicles for scientific and/or clinical purposes.

Proteomic Profiling of the Human Fetal Multipotent Mesenchymal Stromal Cells Secretome

Secretome of multipotent mesenchymal stromal cells (MSCs) is actively used in biomedical applications such as alveolar bone regeneration, treatment of cardiovascular disease, and neurodegenerative disorders. Nevertheless, hMSCs have low proliferative potential and production of the industrial quantity of their secretome might be challenging. Human fetal multipotent mesenchymal stromal cells (FetMSCs) isolated from early human embryo bone marrow are easy to expand and might be a potential source for pharmaceutical substances production based on their secretome. However, the secretome of FetMSCs was not previously analyzed. Here, we describe the secretome of FetMSCs using LC-MALDI shotgun proteomics. We identified 236 proteins. Functional annotation of the identified proteins revealed their involvement in angiogenesis, ossification, regulation of apoptosis, and immune response processes, which made it promising for biomedical applications. The proteins identified in the FetMSCs secretome are involved in the same biological processes as proteins from previously described adult hMSCs secretomes. Nevertheless, many of the common hMSCs secretome components (such as VEGF, FGF, Wnt and TGF-β) have not been identified in the FetMSCs secretome.

Is Stem Cell Commerce in Small Animal Therapies Scientifically and Morally Justified?

The lack of clear regulations for the use of veterinary stem cells has triggered the commercialization of unproven experimental therapies for companion animal diseases. Adult stem cells have complex biological characteristics that are directly related to the therapeutic application, but several questions remain to be answered. In order to regulate the use of these cells, well-conducted, controlled scientific studies that generate high-quality data should be performed, in order to assess the efficacy and safety of the intended treatment. This paper discusses the scientific challenges of mesenchymal stem cell therapy in veterinary regenerative medicine, and reviews published trials of adipose-tissue-derived stem cells in companion animal diseases that spontaneously occur.

The secretome of human dental pulp stem cells protects myoblasts from hypoxia‑induced injury via the Wnt/β‑catenin pathway

Human dental pulp stem cells (hDPSCs) present several advantages, including their ability to be non-invasively harvested without ethical concern. The secretome of hDPSCs can promote the functional recovery of various tissue injuries. However, the protective effects on hypoxia-induced skeletal muscle injury remain to be explored. The present study demonstrated that C2C12 myoblast coculture with hDPSCs attenuated CoCl₂-induced hypoxic injury compared with C2C12 alone. The hDPSC secretome increased cell viability and differentiation and decreased G2/M cell cycle arrest under hypoxic conditions. These results were further verified using hDPSC-conditioned medium (hDPSC-CM). The present data revealed that the protective effects of hDPSC-CM depend on the concentration ratio of the CM. In terms of the underlying molecular mechanism, hDPSC-CM activated the Wnt/β-catenin pathway, which increased the protein levels of Wnt1, phosphorylated-glycogen synthase kinase-3β and β-catenin and the mRNA levels of Wnt target genes. By contrast, an inhibitor (XAV939) of Wnt/β-catenin diminished the protective effects of hDPSC-CM. Taken together, the findings of the present study demonstrated that the hDPSC secretome alleviated the hypoxia-induced myoblast injury potentially through regulating the Wnt/β-catenin pathway. These findings may provide new insight into a therapeutic alternative using the hDPSC secretome in skeletal muscle hypoxia-related diseases.

Dental Stem Cell-Derived Secretome/Conditioned Medium: The Future for Regenerative Therapeutic Applications

Regenerative medicine literature has proposed mesenchymal stem/progenitor cell- (MSC-) mediated therapeutic approaches for their great potential in managing various diseases and tissue defects. Dental MSCs represent promising alternatives to nondental MSCs, owing to their ease of harvesting with minimally invasive procedures. Their mechanism of action has been attributed to their cell-to-cell contacts as well as to the paracrine effect of their secreted factors, namely, secretome. In this context, dental MSC-derived secretome/conditioned medium could represent a unique cell-free regenerative and therapeutic approach, with fascinating advantages over parent cells. This article reviews the application of different populations of dental MSC secretome/conditioned medium in in vitro and in vivo animal models, highlights their significant implementation in treating different tissue' diseases, and clarifies the significant bioactive molecules involved in their regenerative potential. The analysis of these recent studies clearly indicate that dental MSCs' secretome/conditioned medium could be effective in treating neural injuries, for dental tissue regeneration, in repairing bone defects, and in managing cardiovascular diseases, diabetes mellitus, hepatic regeneration, and skin injuries, through regulating anti-inflammatory, antiapoptotic, angiogenic, osteogenic, and neurogenic mediators.

Investigating the potential of the secretome of mesenchymal stem cells derived from sickle cell disease patients

Sickle cell disease (SCD) is a monogenic red cell disorder associated with multiple vascular complications, microvessel injury and wound-healing deficiency. Although stem cell transplantation with bone marrow-derived mesenchymal stem cells (BMSC) can promote wound healing and tissue repair in SCD patients, therapeutic efficacy is largely dependent on the paracrine activity of the implanted BM stromal cells. Since in vitro expansion and culture conditions are known to modulate the innate characteristics of BMSCs, the present study investigated the effects of normoxic and hypoxic cell-culture preconditioning on the BMSC secretome, in addition to the expression of paracrine molecules that induce angiogenesis and skin regeneration. BMSCs derived from SCD patients were submitted to culturing under normoxic (norCM) and hypoxic (hypoCM) conditions. We found that hypoxically conditioned cells presented increased expression and secretion of several well-characterized trophic growth factors (VEGF, IL8, MCP-1, ANG) directly linked to angiogenesis and tissue repair. The hypoCM secretome presented stronger angiogenic potential than norCM, both in vitro and in vivo, as evidenced by HUVEC proliferation, survival, migration, sprouting formation and in vivo angiogenesis. After local application in a murine wound-healing model, HypoCM showed significantly improved wound closure, as well as enhanced neovascularization in comparison to untreated controls. In sum, the secretome of hypoxia-preconditioned BMSC has increased expression of trophic factors involved in angiogenesis and skin regeneration. Considering that these preconditioned media are easily obtainable, this strategy represents an alternative to stem cell transplantation and could form the basis of novel therapies for vascular regeneration and wound healing in individuals with sickle cell disease.

The mesenchymal stem cell secretome: A new paradigm towards cell-free therapeutic mode in regenerative medicine

Mesenchymal Stem Cells (MSCs) have been shown to be a promising candidate for cell-based therapy. The therapeutic potential of MSCs, towards tissue repair and wound healing is essentially based on their paracrine effects. Numerous pre-clinical and clinical studies of MSCs have yielded encouraging results. Further, these cells have been shown to be relatively safe for clinical applications. MSCs harvested from numerous anatomical locations including the bone marrow, adipose tissue, Wharton's jelly of the umbilical cord etc., display similar immunophenotypic profiles. However, there is a large body of evidence showing that MSCs secrete a variety of biologically active molecules such as growth factors, chemokines, and cytokines. Despite the similarity in their immunophenotype, the secretome of MSCs appears to vary significantly, depending on the age of the host and niches where the cells reside. Thus, by implication, proteomics-based profiling suggests that the therapeutic potential of the different MSC populations must also be different. Analysis of the secretome points to its influence on varied biological processes such as angiogenesis, neurogenesis, tissue repair, immunomodulation, wound healing, anti-fibrotic and anti-tumour for tissue maintenance and regeneration. Though MSC based therapy has been shown to be relatively safe, from a clinical standpoint, the use of cell-free infusions can altogether circumvent the administration of viable cells for therapy. Understanding the secretome of in vitro cultured MSC populations, by the analysis of the corresponding conditioned medium, will enable us to evaluate its utility as a new therapeutic option. This review will focus on the accumulating evidence that points to the therapeutic potential of the conditioned medium, both from pre-clinical and clinical studies. Finally, this review will emphasize the importance of profiling the conditioned medium for assessing its potential for cell-free therapy therapy.

The skin regeneration potential of a pro-angiogenic secretome from human skin-derived multipotent stromal cells

Multipotent stromal cells stimulate skin regeneration after acute or chronic injuries. However, many stem cell therapy protocols are limited by the elevated number of cells required and poor cell survival after transplantation. Considering that the beneficial effects of multipotent stromal cells on wound healing are typically mediated by paracrine mechanisms, we examined whether the conditioned medium from skin-derived multipotent stromal cells would be beneficial for restoring the skin structure of mice after wounding. A proteomic characterization of skin-derived multipotent stromal cell-conditioned medium was performed, and the angiogenic function of this secretome was investigated in vitro using an endothelial cell tube formation assay. We then applied the skin-derived multipotent stromal cell-conditioned medium directly to full-thickness excisional wounds or embedded it into carrageenan or poly(vinyl alcohol) hydrogels to monitor tissue regeneration in mice. Biological processes related to wound healing and angiogenesis were highlighted by the analysis of the skin-derived multipotent stromal cell secretome, and a pro-angiogenic capacity for promoting tubule-like structures was first confirmed in vitro. Skin wounds treated with skin-derived multipotent stromal cell-conditioned medium also displayed increased angiogenesis, independently of the association of the conditioned medium with hydrogels. However, improvements in wound closure and epidermis or decreased inflammatory cell presence were not observed. Hence, the use of the secretome obtained from human skin-derived multipotent stromal cells may be a potential strategy to aid the natural skin repair of full-thickness lesions mainly based on its pro-angiogenic properties.

Persistence of fluorescent nanoparticle-labelled bone marrow mesenchymal stem cells in vitro and after intra-articular injection

Mesenchymal stem cells (MSCs) improve the osteoarthritis condition, but the fate of MSCs after intra-articular injection is unclear. We used fluorescent nanoparticles (quantum dots [QDs]) to track equine MSCs (QD-labelled MSCs [QD-MSCs]) in vivo after intra-articular injection into normal and osteoarthritic joints. One week after injection of QD-MSCs, unlabelled MSCs, or vehicle, we determined the presence of QD-MSCs in synovium and articular cartilage histologically. In vitro, we evaluated the persistence of QDs in MSCs and whether QDs affected proliferation, immunophenotype, or differentiation. In joints injected with QD-MSCs, labelled cells were identified on the synovial membrane and significantly less often on articular cartilage, without differences between normal and osteoarthritic joints. Joints injected with QD-MSCs and MSCs had increased synovial total nucleated cell count and protein compared with vehicle-injected joints. In vitro, QDs persisted in nonproliferating cells for up to 8 weeks (length of the study), but QD fluorescence was essentially absent from proliferating cells within two passages (approximately 3 to 5 days). QD labelling did not affect MSC differentiation into chondrocytes, adipocytes, and osteocytes. QD-MSCs had slightly different immunophenotype from control cells, but whether this was due to an effect of the QDs or to drift during culture is unknown. QD-MSCs can be visualized in histological sections 1 week after intra-articular injection and are more frequently found in the synovial membrane versus cartilage in both normal and osteoarthritic joints. QDs do not alter MSC viability and differentiation potential in vitro. However, QDs are not optimal markers for long-term tracking of MSCs, especially under proliferative conditions.

Pericytes Extend Survival of ALS SOD1 Mice and Induce the Expression of Antioxidant Enzymes in the Murine Model and in IPSCs Derived Neuronal Cells from an ALS Patient

Amyotrophic Lateral Sclerosis (ALS) is one of the most common adult-onset motor neuron disease causing a progressive, rapid and irreversible degeneration of motor neurons in the cortex, brain stem and spinal cord. No effective treatment is available and cell therapy clinical trials are currently being tested in ALS affected patients. It is well known that in ALS patients, approximately 50% of pericytes from the spinal cord barrier are lost. In the central nervous system, pericytes act in the formation and maintenance of the blood-brain barrier, a natural defense that slows the progression of symptoms in neurodegenerative diseases. Here we evaluated, for the first time, the therapeutic effect of human pericytes in vivo in SOD1 mice and in vitro in motor neurons and other neuronal cells derived from one ALS patient. Pericytes and mesenchymal stromal cells (MSCs) were derived from the same adipose tissue sample and were administered to SOD1 mice intraperitoneally. The effect of the two treatments was compared. Treatment with pericytes extended significantly animals survival in SOD1 males, but not in females that usually have a milder phenotype with higher survival rates. No significant differences were observed in the survival of mice treated with MSCs. Gene expression analysis in brain and spinal cord of end-stage animals showed that treatment with pericytes can stimulate the host antioxidant system. Additionally, pericytes induced the expression of SOD1 and CAT in motor neurons and other neuronal cells derived from one ALS patient carrying a mutation in FUS. Overall, treatment with pericytes was more effective than treatment with MSCs. Our results encourage further investigations and suggest that pericytes may be a good option for ALS treatment in the future. Graphical Abstract ᅟ.

Placenta-derived mesenchymal stromal cells and their exosomes exert therapeutic effects in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a degenerative lethal, X-linked disease of skeletal and cardiac muscles caused by mutations in the dystrophin gene. Cell therapy using different cell types, including mesenchymal stromal cells (MSCs), has been considered as a potential approach for the treatment of DMD. MSCs can be obtained from autologous sources such as bone marrow and adipose tissues or from allogeneic placenta and umbilical cord. The safety and therapeutic impact of these cells has been demonstrated in pre-clinical and clinical studies and their functions are attributed to paracrine effects that are mediated by secreted cytokines and extracellular vesicles. Here, we studied the therapeutic effects of placenta-derived MSCs (PL-MSCs) and their secreted exosomes using mouse and human myoblasts from healthy controls, Duchenne patients and mdx mice. Treatment of myoblasts with conditioned medium or exosomes secreted by PL-MSCs increased the differentiation of these cells and decreased the expression of fibrogenic genes in DMD patient myoblasts. In addition, these treatments also increased the expression of utrophin in these cells. Using a quantitative miR-29c reporter, we demonstrated that the PL-MSC effects were partly mediated by the transfer of exosomal miR-29c. Intramuscular transplantation of PL-MSCs in mdx mice resulted in decreased creatine kinase levels. PL-MSCs significantly decreased the expression of TGF-β and the level of fibrosis in the diaphragm and cardiac muscles, inhibited inflammation and increased utrophin expression. In vivo imaging analyses using MSCs labeled with gold nanoparticles or fluorescent dyes demonstrated localization of the cells in the muscle tissues up to 3 weeks post treatment. Altogether, these results demonstrate that PL-MSCs and their secreted exosomes have important clinical applications in cell therapy of DMD partly via the targeted delivery of exosomal miR-29c.

Articular and subcutaneous adipose tissues of rheumatoid arthritis patients represent equal sources of immunoregulatory mesenchymal stem cells

Adipose-derived mesenchymal stem cells (ASCs) have immunoregulatory properties, but their activity is dependent on signals provided by the local microenvironment. It is likely that highly inflammatory milieu of rheumatoid joint affects ASCs activity. To test this hypothesis, the function of rheumatoid ASCs derived from articular adipose tissue (AT-ASCs) and ASCs derived from subcutaneous adipose tissue (Sc-ASCs) has been analysed. Articular adipose tissue (infrapatellar fat pad) and subcutaneous adipose tissue (from the site of skin closure with sutures) were obtained from rheumatoid arthritis (RA) patients undergoing total knee joint replacement surgery. ASCs were isolated accordingly to the routinely applied procedure, expanded and treated or not with IFNγ and TNF (10 ng/ml). To evaluate immunomodulatory properties of AT- and Sc-ASCs, co-cultures with peripheral blood mononuclear cells (PBMCs) from healthy donors have been set. Proliferation of activated PBMCs (³H-thymidine incorporation method), secretion of IL-10 and IL-17A in co-culture supernatants (specific ELISA tests) and T regulatory FoxP3⁺ cells (Tregs) percentage have been evaluated (flow cytometry). Performed experiments demonstrated that ASCs from both sources have comparable properties. They suppress proliferation of activated PBMCs to the similar extent, induce IL-10 secretion by resting PBMCs and moderately induce generation of FoxP3⁺ Treg cells. Interestingly, both AT-ASCs and Sc-ASCs cause increase of IL-17A secretion by activated PBMCs as well as induce up-regulation of IL-6 concentration in co-culture supernatants. We demonstrated that AT-ASCs and Sc-ASCs obtained from RA patients possess similar immunomodulatory properties despite different localization and distinct cytokine milieu of tissue of origin. Our results indicate that ASCs derived from rheumatoid adipose tissues are not strongly immunosuppressive in vitro and that they may contribute to the pathogenesis of RA due to IL-17A secretion enhancement.

Mesenchymal Stem Cell Secretome: Toward Cell-Free Therapeutic Strategies in Regenerative Medicine

Earlier research primarily attributed the effects of mesenchymal stem cell (MSC) therapies to their capacity for local engrafting and differentiating into multiple tissue types. However, recent studies have revealed that implanted cells do not survive for long, and that the benefits of MSC therapy could be due to the vast array of bioactive factors they produce, which play an important role in the regulation of key biologic processes. Secretome derivatives, such as conditioned media or exosomes, may present considerable advantages over cells for manufacturing, storage, handling, product shelf life and their potential as a ready-to-go biologic product. Nevertheless, regulatory requirements for manufacturing and quality control will be necessary to establish the safety and efficacy profile of these products. Among MSCs, human uterine cervical stem cells (hUCESCs) may be a good candidate for obtaining secretome-derived products. hUCESCs are obtained by Pap cervical smear, which is a less invasive and painful method than those used for obtaining other MSCs (for example, from bone marrow or adipose tissue). Moreover, due to easy isolation and a high proliferative rate, it is possible to obtain large amounts of hUCESCs or secretome-derived products for research and clinical use.

Interferon γ induced compositional changes in human bone marrow derived mesenchymal stem/stromal cells

Background

Mesenchymal stem/stromal cells (MSC) display a range of immunoregulatory properties which can be enhanced by the exposure to cytokines such interferon γ (IFN-γ). However the compositional changes associated with the ‘licensing’ of these cells have not been clearly defined. The present study was undertaken to provide a detailed comparative proteomic analysis of the compositional changes that occur in human bone marrow derived MSC following 20 h treatment with IFN-γ.

Methods

2D LC MSMS analysis of control and IFN-γ treated cells from 5 different healthy donors provided confident identification of more than 8400 proteins.

Results

In total 210 proteins were shown to be significantly altered in their expression levels (≥|2SD|) following IFN-γ treatment. The changes for several of these proteins were confirmed by flow cytometry. STRING analysis determined that approximately 30% of the altered proteins physically interacted in described interferon mediated processes. Comparison of the list of proteins that were identified as changed in the proteomic analysis with data for the same proteins in the Interferome DB indicated that ~35% of these proteins have not been reported to be IFN-γ responsive in a range of cell types.

Conclusions

This data provides an in depth analysis of the proteome of basal and IFN-γ treated human mesenchymal stem cells and it identifies a number of novel proteins that may contribute to the immunoregulatory capacity if IFN-γ licensed cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-017-9161-1) contains supplementary material, which is available to authorized users.

Adipose-derived stem cell therapies for bone regeneration

INTRODUCTION

Cell-based therapies exploit the heterogeneous and self-sufficient biological environment of stem cells to restore, maintain and improve tissue functions. Adipose-derived stem cells (ASCs) are, to this aim, promising cell types thanks to advantageous isolation procedures, growth kinetics, plasticity and trophic properties. Specifically, bone regeneration represents a suitable, though often challenging, target setting to test and apply ASC-based therapeutic strategies. Areas covered: ASCs are extremely plastic and secrete bioactive peptides that mediate paracrine functions, mediating their trophic actions in vivo. Numerous preclinical studies demonstrated that ASCs improve bone healing. Clinical trials are ongoing to validate the clinical feasibility of these approaches. This review is intended to define the state-of-the-art on ASCs, encompassing the biological features that make them suitable for bone regenerative strategies, and to provide an update on existing preclinical and clinical applications. Expert opinion: ASCs offer numerous advantages over other stem cells in terms of feasibility of clinical translation. Data obtained from in vivo experimentation are encouraging, and clinical trials are ongoing. More robust validations are thus expected to be achieved during the next few years, and will likely pave the way to optimized patient-tailored treatments for bone regeneration.