Mesenchymal stem cell treatments in rheumatology: a glass half full?

Efficiently directing differentiation and homing of mesenchymal stem cells to boost cartilage repair in osteoarthritis via a nanoparticle and peptide dual-engineering strategy

Mesenchymal stem cells (MSCs) are expected to be useful therapeutics in osteoarthritis (OA), the most common joint disorder characterized by cartilage degradation. However, evidence is limited with regard to cartilage repair in clinical trials because of the uncontrolled differentiation and weak cartilage-targeting ability of MSCs after injection. To overcome these drawbacks, here we synthesized CuO@MSN nanoparticles (NPs) to deliver Sox9 plasmid DNA (favoring chondrogenesis) and recombinant protein Bmp7 (inhibiting hypertrophy). After taking up CuO@MSN/Sox9/Bmp7 (CSB NPs), the expressions of chondrogenic markers were enhanced while hypertrophic markers were decreased in response to these CSB-engineered MSCs. Moreover, a cartilage-targeted peptide (designated as peptide W) was conjugated onto the surface of MSCs via a click chemistry reaction, thereby prolonging the residence time of MSCs in both the knee joint cavity of mice and human-derived cartilage. In a surgery-induced OA mouse model, the NP and peptide dual-modified W-CSB-MSCs showed an enhancing therapeutic effect on cartilage repair in knee joints compared with other engineered MSCs after intra-articular injection. Most importantly, W-CSB-MSCs accelerated cartilage regeneration in damaged cartilage explants derived from OA patients. Thus, this new peptide and NPs dual engineering strategy shows potential for clinical applications to boost cartilage repair in OA using MSC therapy.

Extracellular vesicles are key players in mesenchymal stem cells' dual potential to regenerate and modulate the immune system

MSCs are used for treatment of inflammatory conditions or for regenerative purposes. MSCs are complete cells and allogenic transplantation is in principle possible, but mostly autologous use is preferred. In recent years, it was discovered that cells secrete extracellular vesicles. These are active budded off vesicles that carry a cargo. The cargo can be miRNA, protein, lipids etc. The extracellular vesicles can be transported through the body and fuse with target cells. Thereby, they influence the phenotype and modulate the disease. The extracellular vesicles have, like the MSCs, immunomodulatory or regenerative capacities. This review will focus on those features of extracellular vesicles and discuss their dual role. Besides the immunomodulation, the regeneration will concentrate on bone, cartilage, tendon, vessels and nerves. Current clinical trials with extracellular vesicles for immunomodulation and regeneration that started in the last five years are highlighted as well. In summary, extracellular vesicles have a great potential as disease modulating entity and treatment. Their dual characteristics need to be taken into account and often are both important for having the best effect.

Mesenchymal stem cell therapy in diabetic foot ulcer: An updated comprehensive review

Background

Diabetes has evolved into a worldwide public health issue. One of the most serious complications of diabetes is diabetic foot ulcer (DFU), which frequently creates a significant financial strain on patients and lowers their quality of life. Up until now, there has been no curative therapy for DFU, only symptomatic relief or an interruption in the disease's progression. Recent studies have focused attention on mesenchymal stem cells (MSCs), which provide innovative and potential treatment candidates for several illnesses as they can differentiate into various cell types. They are mostly extracted from the placenta, adipose tissue, umbilical cord (UC), and bone marrow (BM). Regardless of their origin, they show comparable features and small deviations. Our goal is to investigate MSCs' therapeutic effects, application obstacles, and patient benefit strategies for DFU therapy.

Methodology

A comprehensive search was conducted using specific keywords relating to DFU, MSCs, and connected topics in the databases of Medline, Scopus, Web of Science, and PubMed. The main focus of the selection criteria was on English-language literature that explored the relationship between DFU, MSCs, and related factors.

Results and Discussion

Numerous studies are being conducted and have demonstrated that MSCs can induce re-epithelialization and angiogenesis, decrease inflammation, contribute to immunological modulation, and subsequently promote DFU healing, making them a promising approach to treating DFU. This review article provides a general snapshot of DFU (including clinical presentation, risk factors and etiopathogenesis, and conventional treatment) and discusses the clinical progress of MSCs in the management of DFU, taking into consideration the side effects and challenges during the application of MSCs and how to overcome these challenges to achieve maximum benefits.

Conclusion

The incorporation of MSCs in the management of DFU highlights their potential as a feasible therapeutic strategy. Establishing a comprehensive understanding of the complex relationship between DFU pathophysiology, MSC therapies, and related obstacles is essential for optimizing therapy outcomes and maximizing patient benefits.

Dental pulp stem cell-derived exosomes revitalize salivary gland epithelial cell function in NOD mice via the GPER-mediated cAMP/PKA/CREB signaling pathway

BACKGROUND

Restoration of salivary gland function in Sjogren's syndrome (SS) is still a challenge. Dental pulp stem cells (DPSCs) derived exosomes had shown anti-inflammatory, anti-oxidative, immunomodulatory, and tissue function restorative abilities. However, the salivary gland function restoration potential of DPSCs-derived exosomes (DPSC-Exos) during SS has not been investigated yet.

METHODS

DPSC-Exos was isolated by ultracentrifugation methods and characterized. Salivary gland epithelial cells (SGEC) were treated with interferon-gamma (IFN-γ) to mimic SS in vitro and cultured with or without DPSC-Exos. SGEC survival and aquaporin 5 (AQP5) expression were analyzed. mRNA sequencing and bioinformatics analysis were performed in IFN-γ vs. DPSC-Exos+ IFN-γ treated SGEC. Non-obese diabetic (NOD)/ltj female mice (SS model), were intravenously administered with DPSC-Exos, and salivary gland functions and SS pathogenicity were analyzed. Furthermore, the mRNA sequencing and bioinformatics predicted mechanism of the therapeutic effect of DPSC-Exos was further investigated both in vitro and in vivo using RT-qPCR, Western blot, immunohistochemistry, immunofluorescence, flowcytometry analysis.

RESULTS

DPSC-Exos partially rescued IFN-γ triggered SGEC death. IFN-γ inhibited AQP5 expression in SGEC and DPSC-Exos reversed this effect. Transcriptome analysis showed GPER was the upregulated DEG in DPSC-Exos-treated SGEC with a positive correlation with salivary secretion-related DEGs. Pathway enrichment analysis revealed that DEGs were mainly attributed to estrogen 16 alpha-hydroxylase activity, extracellular exosome function, cAMP signaling, salivary secretion, and estrogen signaling. Intravenous injection of DPSC-Exos in NOD/ltj mice alleviated the SS syndrome as indicated by the increased salivary flow rate, attenuated glandular inflammation, and increased AQP5 expression. GPER was also upregulated in the salivary gland of DPSC-Exos-treated NOD/ltj mice compared with the PBS-treated NOD/ltj mice. IFN-γ+DPSC-Exos-treated SGEC showed higher expression of AQP5, p-PKA, cAMP, and intracellular Ca²⁺ levels compared with IFN-γ-treated SGEC. These effects were reversed by the inhibition of GPER.

CONCLUSIONS

Our results showed that DPSC-Exos revitalize salivary gland epithelial cell function during SS via the GPER-mediated cAMP/PKA/CREB pathway suggesting the possible therapeutic potential of DPSC-Exos in SS-treatment.

Biology and therapeutic potential of mesenchymal stem cell extracellular vesicles in axial spondyloarthritis

Axial spondyloarthritis (AxSpA) is a chronic, inflammatory, autoimmune disease that predominantly affects the joints of the spine, causes chronic pain, and, in advanced stages, may result in spinal fusion. Recent developments in understanding the immunomodulatory and tissue-differentiating properties of mesenchymal stem cell (MSC) therapy have raised the possibility of applying such treatment to AxSpA. The therapeutic effectiveness of MSCs has been shown in numerous studies spanning a range of diseases. Several studies have been conducted examining acellular therapy based on MSC secretome. Extracellular vesicles (EVs) generated by MSCs have been proven to reproduce the impact of MSCs on target cells. These EVs are associated with immunological regulation, tissue remodeling, and cellular homeostasis. EVs' biological effects rely on their cargo, with microRNAs (miRNAs) integrated into EVs playing a particularly important role in gene expression regulation. In this article, we will discuss the impact of MSCs and EVs generated by MSCs on target cells and how these may be used as unique treatment strategies for AxSpA.

Labial Gland Mesenchymal Stem Cell Derived Exosomes-Mediated miRNA-125b Attenuates Experimental Sjogren's Syndrome by Targeting PRDM1 and Suppressing Plasma Cells

The pathogenesis of the prototypical chronic autoimmune disorder primary Sjögren syndrome (pSS) has been thought to be B-cell-centric, based on serum autoantibodies, the increased risk of B cell lymphoma, and altered B cell subsets in patients with pSS. Over the last 10 years, therapies targeting B cells have been investigated for pSS; however, current evidence for the efficacy of B cell targeted therapies in pSS is still sparse. Mesenchymal stem cells (MSCs) might represent a promising strategy for cell therapy of autoimmune diseases via regulation of immune cells. MSC-released exosomes carry various bioactive molecules and thus have been studied in MSC-based therapy. The newly discovered labial gland MSCs (LGMSCs) have exhibited enhanced performance. Herein, we aimed to determine the effects of LGMSC-derived exosomes (LGMSC-Exos) on the symptoms of a mouse model of pSS and their regulatory effect and mechanism on B cell subsets. In vivo, treatment of the spontaneous mouse model of pSS with LGMSC-Exos resulted in reduced inflammatory infiltration and restored saliva secretion in salivary glands. In vitro, coculture of LGMSC-Exos with peripheral blood mononuclear cells of patients with pSS markedly reduced the proportions of CD19⁺CD20^-CD27⁺CD38⁺ plasma cells among peripheral blood mononuclear cells. Further investigations provided evidence that LGMSC-Exo-derived microRNA-125b affected plasma cells of pSS by directly binding to its target gene, PRDM1 (PR domain zinc finger protein 1, also known as BLIMP1), which might be developed as a target to treat pSS. Overall, these findings provided a possible exploitable therapeutic target in pSS and provide new insights into the potential therapeutic application of exosomes in pSS and other disease mediated by B-cells.

Two-Dimensional and Three-Dimensional Cartilage Model Platforms for Drug Evaluation and High-Throughput Screening Assays

Osteoarthritis (OA) is a severely painful and debilitating disease of the joint, which brings about degradation of the articular cartilage and currently has few therapeutic solutions. Two-dimensional (2D) high-throughput screening (HTS) assays have been widely used to identify candidate drugs with therapeutic potential for the treatment of OA. A number of small molecules which improve the chondrogenic differentiation of progenitor cells for tissue engineering applications have also been discovered in this way. However, due to the failure of these models to accurately represent the native joint environment, the efficacy of these drugs has been limited in vivo. Screening systems utilizing three-dimensional (3D) models, which more closely reflect the tissue and its complex cell and molecular interactions, have also been described. However, the vast majority of these systems fail to recapitulate the complex, zonal structure of articular cartilage and its unique cell population. This review summarizes current 2D HTS techniques and addresses the question of how to use existing 3D models of tissue-engineered cartilage to create 3D drug screening platforms with improved outcomes. Impact statement Currently, the use of two-dimensional (2D) screening platforms in drug discovery is common practice. However, these systems often fail to predict efficacy in vivo, as they do not accurately represent the complexity of the native three-dimensional (3D) environment. This article describes existing 2D and 3D high-throughput systems used to identify small molecules for osteoarthritis treatment or in vitro chondrogenic differentiation, and suggests ways to improve the efficacy of these systems based on the most recent research.

Strategies for improving adipose-derived stem cells for tissue regeneration

Adipose-derived stem cells (ADSCs) have promising applications in tissue regeneration. Currently, there are only a few ADSC products that have been approved for clinical use. The clinical application of ADSCs still faces many challenges. Here, we review emerging strategies to improve the therapeutic efficacy of ADSCs in tissue regeneration. First, a great quantity of cells is often needed for the stem cell therapies, which requires the advanced cell expansion technologies. In addition cell-derived products are also required for the development of ‘cell-free’ therapies to overcome the drawbacks of cell-based therapies. Second, it is necessary to strengthen the regenerative functions of ADSCs, including viability, differentiation and paracrine ability, for the tissue repair and regeneration required for different physiological and pathophysiological conditions. Third, poor delivery efficiency also restricts the therapeutic effect of ADSCs. Effective methods to improve cell delivery include alleviating harsh microenvironments, enhancing targeting ability and prolonging cell retention. Moreover, we also point out some critical issues about the sources, effectiveness and safety of ADSCs. With these advanced strategies to improve the therapeutic efficacy of ADSCs, ADSC-based treatment holds great promise for clinical applications in tissue regeneration.

Human umbilical cord mesenchymal stem cell-derived small extracellular vesicles ameliorate collagen-induced arthritis via immunomodulatory T lymphocytes

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease for which there are currently no effective therapies. Although mesenchymal stem cells (MSCs) can prevent arthritis through immunomodulatory mechanisms, there are several associated risks. Alternatively, MSC-derived small extracellular vesicles (sEVs) can mimic the effects of MSCs, while reducing the risk of adverse events. However, few studies have examined sEVs in the context of RA. Here, we evaluate the immunomodulatory effects of human umbilical cord MSC (hUCMSC)-derived sEVs on T lymphocytes in a collagen-induced arthritis (CIA) rat model to elucidate the possible mechanism of sEVs in RA treatment. We then compare these mechanisms to those of MSCs and methotrexate (MTX).

METHODS

The arthritis index and synovial pathology were assessed. T lymphocyte proliferation and apoptosis, Th17 and Treg proportions, and interleukin (IL)-17, IL-10, and transforming growth factor (TGF)-β expression were detected using flow cytometry. Retinoic acid receptor-related orphan receptor gamma t (RORγt) and forkhead box P3 (FOXP3), which are master transcriptional regulators of Th17 and Treg differentiation, were also assessed using immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

sEV treatment ameliorated arthritis and inhibited synovial hyperplasia in a dose-dependent manner. These effects were mediated by inhibiting T lymphocyte proliferation and promoting their apoptosis, while decreasing Th17 cell proportion and increasing that of Treg cells in the spleen, resulting in decreased serum IL-17, and enhanced IL-10 and TGF-β expression. Transcriptionally, sEVs decreased RORγt and increased FOXP3 expression in the spleen, and decreased RORγt and FOXP3 expression in the joints. In some aspects sEVs were more effective than MSCs and MTX in treating CIA.

CONCLUSIONS

hUCMSC-derived sEVs ameliorate CIA via immunomodulatory T lymphocytes, and might serve as a new therapy for RA.

In Vitro Generation of Vascular Wall-Typical Mesenchymal Stem Cells (VW-MSC) from Murine Induced Pluripotent Stem Cells Through VW-MSC-Specific Gene Transfer

Among the adult stem cells, multipotent mesenchymal stem cells (MSCs) turned out to be a promising option for cell-based therapies for the treatment of various diseases including autoimmune and cardiovascular disorders. MSCs bear a high proliferation and differentiation capability and exert immunomodulatory functions while being still clinically safe. As tissue-resident stem cells, MSCs can be isolated from various tissue including peripheral or umbilical cord blood, placenta, blood, fetal liver, lung, adipose tissue, and blood vessels, although the most commonly used source for MSCs is the bone marrow. However, the proportion of MSCs in primary isolates from adult tissue biopsies is rather low, and therefore MSCs must be intensively expanded in vitro before the MSCs find particular use in therapies that may require extensive and repetitive cell replacement. Therefore, more easily accessible sources of MSCs are needed. Here, we present a detailed protocol to generate tissue-typical MSCs by direct linage conversion using transcription factors defining target MSC identity from murine induced pluripotent stem cells (iPSCs).

Multifaceted Optimization of MSC-Based Formulation upon Sodium Iodoacetate-Induced Osteoarthritis Models by Combining Advantageous HA/PG Hydrogel and Fluorescent Tracer

Owing to the boundedness of conventional remedies upon articular cartilage for self-rehabilitation and the incrementally senior citizens, the incidence of osteoarthritis (OA) is increasing worldwide. Empirical studies have revealed the advantageous and promising potentials of mesenchymal stem/stromal cells (MSCs) on the refractory OA, whereas the deficiency of systematic and detailed exploration of MSC-based therapy largely hampers the large-scale applications in regenerative medicine. Herein, we initially utilized the monosodium iodoacetate- (MIA-) induced OA rabbit models and investigated the therapeutic effect of human umbilical cord-derived UC-MSCs at serial dose gradients with the splendid hyaluronic acid and/or propylene glycol hydrogels (HA, HA/PG), respectively. Afterwards, we turned to a dual-luciferase reporter tracing system and evaluated the spatiotemporal distribution and metabolokinetics of bifluorescence expressing UC-MSCs (BF-MSCs) in OA rats. Of the aforementioned trials, we verified that the combination of HA/PG and middle-dose MSCs ( $0.5\times {10}^7$ cells/ml) eventually manifested the optimal efficacy on OA rabbits. Furthermore, with the aid of the bioluminescence imaging (BLI) technology for dynamic in vitro and in vivo tracking, we intuitively delineated the spatiotemporal distribution and therapeutic process of BF-MSCs in OA rats, which substantially confirmed the reinforcement of HA/PG on BF-MSCs for OA treatment. Collectively, our data conformably demonstrated that the middle dose of UC-MSCs combined with HA/PG hydrogel was sufficient for optimal MSC-based formulation for blocking OA progression and promoting cartilage repair, which supplied overwhelming new references and enlightened MSC-based therapeutic strategies for cartilage defects.

High-efficient generation of VCAM-1+ mesenchymal stem cells with multidimensional superiorities in signatures and efficacy on aplastic anaemia mice

OBJECTIVE

Longitudinal studies have indicated VCAM-1⁺ mesenchymal stem/stromal cells (MSCs) as promising resources in regenerative medicine, yet the abundance in gene expression is far from adequate in the advantaged and "discarded" hUC-MSCs. Thus, high-efficient preparation and systematic dissection of the signatures and biofunctions of the subpopulation is the prerequisite for large-scale clinical applications.

MATERIALS AND METHODS

We primarily took advantage of a cytokine-based programming strategy for large-scale VCAM-1⁺ hUC-MSC generation (III-MSCs). Thereafter, we conducted multifaceted analyses including cytomorphology, immunophenotype, cell vitality, multilineage differentiation, whole-genome analysis, tube formation and Matrigel plug assay, lymphocyte activation and differentiation, and systemic transplantation for aplastic anaemia (AA) treatment.

RESULTS

III-MSCs with high-proportioned VCAM-1 expression were obtained by combining IL-1β, IL-4 with IFN-γ, which exhibited comparable immunophenotype with untreated hUC-MSCs (NT-MSCs) but revealed multidimensional superiorities both at the cellular and molecular levels. Simultaneously, systemic infusion of III-MSCs could significantly ameliorate clinicopathological features and finally help facilitate haematopoietic reconstruction and immunoregulation in AA mice.

CONCLUSIONS

We have established a high-efficient procedure for large-scale generation of III-MSCs with preferable signatures and efficacy upon aplastic anaemia in mice. Our findings suggested that III-MSCs were advantageous sources with multifaceted characteristics for regenerative medicine.

Preclinical Evaluation of a Single Intravenous Infusion of hUC-MSC (BX-U001) in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory disease of the joints, which causes severe pain and excessive systemic circulation of harmful inflammatory cytokines. Current treatments are limited, with some patients not responding well, and some experiencing severe and detrimental side effects. Mesenchymal stem cells (MSC) are cell-based therapeutics being evaluated as potent immunomodulators in RA and may provide relief to patients not responding well to drug-based treatments. We evaluated the safety and efficacy of BX-U001 human umbilical cord tissue-derived mesenchymal stem cells (hUC-MSC) to treat RA, in support of a successful investigational new drug application. A collagen-induced arthritis (CIA) mouse model of RA was established in DBA/1 J mice. Mice from the treatment assessment group were given a tail vein infusion of hUC-MSC 24 days after primary RA induction, while control assessment (CA) group mice were given cell-free carrier solution. All animals were evaluated daily for RA symptoms via clinical scoring, blood was taken periodically for cytokine analysis, and mice were dissected at end point for histological analysis. A linear mixed model was used to compare the rate of change among groups. The clinical scores of TA group were significantly reduced compared with CA group (P < 0.01), indicating therapeutic effects. The histological scores of the joints in TA group were significantly lower than those in the CA group (P < 0.05), but had no significant difference compared with Healthy groups (P > 0.05). The concentration of (interleukin) IL-6 in TA group was significantly reduced by 80.0% (P < 0.0001) 2 days after treatment and by 93.4% at the experimental endpoint compared with levels prior to hUC-MSC injection. A single intravenous infusion of hUC-MSC (2 × 106 cells/mouse), to CIA-induced DBA/1 J mice, resulted in significant alleviation of RA symptoms and may provide significant therapeutic benefits in humans.

Systematic comparison of hUC-MSCs at various passages reveals the variations of signatures and therapeutic effect on acute graft-versus-host disease

BACKGROUND

Mesenchymal stem cells are heterogenous populations with hematopoietic supporting and immunomodulating capacities. Enormous studies have focused on their preclinical or clinical therapeutic effects, yet the systematic study of continuous in vitro passages on signatures and functions of UC-MSCs at both the cellular and molecular levels is still lacking.

METHODS

In this study, to systematically evaluate the biological properties of MSCs at various passages, we analyzed biomarker expression, cell proliferation and apoptosis, chromosome karyotype, and tri-lineage differentiation potential. Subsequently, we took advantage of whole-exome sequencing to compare the somatic hypermutation of hUC-MSCs at P3, P6, and P15 including SNV and INDEL mutations. In addition, to explore the safety of the abovementioned hUC-MSCs, we performed metabolic pathway enrichment analysis and in vivo transplantation analysis. Furthermore, we cocultured the abovementioned hUC-MSCs with UCB-CD34⁺ HSCs to evaluate their hematopoietic supporting capacity in vitro. Finally, we transplanted the cells into acute graft-versus-host disease (aGVHD) mice to further evaluate their therapeutic effect in vivo.

RESULTS

The hUC-MSCs at P3, P6, and P15 showed similar morphology, biomarker expression, and cytokine secretion. hUC-MSCs at P15 had advantages on adipogenic differentiation and some cytokine secretion such as IL-6 and VEGF, with disadvantages on cell proliferation, apoptosis, and osteogenic and chondrogenic differentiation potential. Based on the SNP data of 334,378 exons and bioinformatic analyses, we found the somatic point mutations could be divided into 96 subsets and formed 30 kinds of signatures but did not show correlation with risk of tumorigenesis, which was confirmed by the in vivo transplantation experiments. However, hUC-MSCs at P15 showed impaired hematologic supporting effect in vitro and declined therapeutic effect on aGVHD in vivo.

CONCLUSIONS

In this study, we systematically evaluated the biological and genetic properties of hUC-MSCs at various passages. Our findings have provided new references for safety and effectiveness assessments, which will provide overwhelming evidence for the safety of hUC-MSCs after continuous in vitro passages both at the cellular and molecular levels for the first time. Taken together, our studies could help understand the controversial effects of disease treatment and benefit the clinical research of UC-MSCs.

Meta-analysis of preclinical studies of mesenchymal stromal cells to treat rheumatoid arthritis

BACKGROUND

This study aims to evaluate the quality of preclinical data, determine the effect sizes, and identify experimental measures that inform efficacy using mesenchymal stromal (or stem) cells (MSC) therapy in animal models of rheumatoid arthritis (RA).

METHODS

Literature searches were performed on MSC preclinical studies to treat RA. MSC treatment effect sizes were determined by the most commonly used outcome measures, including paw thickness, clinical score, and histological score.

FINDINGS

A total of 48 studies and 94 treatment arms were included, among which 42 studies and 79 treatment arms reported that MSC improved outcomes. The effect sizes of RA treatments using MSC, when compared to the controls, were: paw thickness was ameliorated by 53.6% (95% confidence interval (CI): 26.7% -80.4%), histological score was decreased by 44.9% (95% CI: 33.3% -56.6%), and clinical score was decreased by 29.9% (95% CI: 16.7% -43.0%). Specifically, our results indicated that human umbilical cord derived MSC led to large improvements of the clinical score (-42.1%) and histological score (-51.4%).

INTERPRETATION

To the best of our knowledge, this meta-analysis is to quantitatively answer whether MSC represent a robust RA treatment in animal models. It suggests that in preclinical studies, MSC have consistently exhibited therapeutic benefits. The findings demonstrate a need for considering variations in different animal models and treatment protocols in future studies using MSC to treat RA in humans to maximise the therapeutic gains in the era of precision medicine.

FUNDS

NIH [1DP2CA195763], Baylx Inc.: BI-206512, NINDS/NIH Training Grant [Award# NS082174].

Enhancing Mesenchymal Stromal Cell Immunomodulation for Treating Conditions Influenced by the Immune System

Mesenchymal stromal cells (MSCs), formerly known as mesenchymal stem cells, are nonhematopoietic multipotent cells and are emerging worldwide as the most clinically used and promising source for allogeneic cell therapy. MSCs, initially obtained from bone marrow, can be derived from several other tissues, such as adipose tissue, placenta, and umbilical cord. Diversity in tissue sourcing and manufacturing procedures has significant effects on MSC products. However, in 2006, a minimal set of standard criteria has been issued by the International Society of Cellular Therapy for defining derived MSCs. These include adherence to plastic in conventional culture conditions, particular phenotype, and multilineage differentiation capacity in vitro. Moreover, MSCs have trophic capabilities, a high in vitro self-renewal ability, and immunomodulatory characteristics. Thus, immunosuppressive treatment with MSCs has been proposed as a potential therapeutic alternative for conditions in which the immune system cells influence outcomes, such as inflammatory and autoimmune diseases. The precise mechanism by which MSCs affect functions of most immune effector cells is not completely understood but involves direct contact with immune cells, soluble mediators, and local microenvironmental factors. Recently, it has been shown that their homeostatic resting state requires activation, which can be achieved in vitro with various cytokines, including interferon-γ. In the present review, we focus on the suppressive effect that MSCs exert on the immune system and highlight the significance of in vitro preconditioning and its use in preclinical studies. We discuss the clinical aspects of using MSCs as an immunomodulatory treatment. Finally, we comment on the risk of interfering with the immune system in regard to cancer formation and development.

Immunomodulatory effect of human umbilical cord mesenchymal stem cells on T lymphocytes in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease which is lack of effective therapies. Abnormal activation, proliferation, and differentiation of T lymphocytes are closely related to RA. Mesenchymal stem cells (MSCs) can be used for RA treatment due to their immunoregulatory effects. However, the specific molecular mechanisms have not been fully elucidated and the therapeutic effect has been inconsistent. This study investigated the immunomodulatory effect of human umbilical cord MSCs (hUCMSCs) on T lymphocytes in collagen-induced arthritis (CIA) rats and RA patients to clarify the possible mechanism of hUCMSCs in RA treatment. The effects of hUCMSCs on arthritis index, radiological and synovial pathological changes, T lymphocyte proliferation and apoptosis, RORγt and Foxp3 expression, Th17 and Treg cell ratios, and IL-17 and TGF-β levels were assessed in CIA rats. Further, we verified the effect of hUCMSCs in RA patients, and compared the effect of hUCMSCs with that of hUCMSC derived extracellular vesicles (EVs). The results showed that hUCMSCs inhibited the proliferation and promoted apoptosis in T lymphocytes, downregulated RORγt mRNA and protein expression, decreased Th17 cell ratio, upregulated Foxp3 mRNA and protein expression, and increased Treg cell ratio in the spleen. Furthermore, they downregulated RORγt and Foxp3 expression in the joints, and inhibited IL-17 and promoted TGF-β expression in the serum, thereby improving arthritis, delaying radiological progression, and inhibiting synovial hyperplasia in CIA rats. In vitro the effects of hUCMSCs and EVs were consistent with those in vivo. Therefore, hUCMSCs may be expected to serve as a new therapy for RA.

MSC Therapy for Osteoarthritis: An Unfinished Story

Mesenchymal stromal cells (MSCs) have firmly occupied the attention of orthopedic clinicians and scientists for most of the last 25 years. Hundreds of laboratories worldwide have carried out research aimed at unraveling the biological characteristics of these cells and probing the manner in which they potentially contribute to cartilage and bone repair. Clinical trials registries indicate that they are also being tested in patient studies for a wide range of conditions such as osteoarthritis, rheumatoid arthritis, fracture repair, regeneration of articular cartilage, tendon repair, and for treatment of degenerative disc disease. Despite these efforts, the effectiveness of MSCs as a treatment modality for these conditions is still uncertain and market authorizations have been limited. In addition, critical and clear phenotypic parameters for defining MSCs are uncertain and a coherent biological framework surrounding the therapeutic mechanism of action is not yet available. Added to this, cell manufacturing protocols are complex and costly and present substantial challenges in terms of regulatory oversight and standardization. Despite these obstacles, MSCs still remain at the forefront of efforts in Regenerative Medicine, based on a conviction that this technology can provide an effective treatment paradigm for major diseases where there is still an unmet need. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1229-1235, 2019.

Production of Mesenchymal Stem Cells Through Stem Cell Reprogramming

Mesenchymal stem cells (MSCs) possess a broad spectrum of therapeutic applications and have been used in clinical trials. MSCs are mainly retrieved from adult or fetal tissues. However, there are many obstacles with the use of tissue-derived MSCs, such as shortages of tissue sources, difficult and invasive retrieval methods, cell population heterogeneity, low purity, cell senescence, and loss of pluripotency and proliferative capacities over continuous passages. Therefore, other methods to obtain high-quality MSCs need to be developed to overcome the limitations of tissue-derived MSCs. Pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are considered potent sources for the derivation of MSCs. PSC-derived MSCs (PSC-MSCs) may surpass tissue-derived MSCs in proliferation capacity, immunomodulatory activity, and in vivo therapeutic applications. In this review, we will discuss basic as well as recent protocols for the production of PSC-MSCs and their in vitro and in vivo therapeutic efficacies. A better understanding of the current advances in the production of PSC-MSCs will inspire scientists to devise more efficient differentiation methods that will be a breakthrough in the clinical application of PSC-MSCs.

Injection of Adipose-Derived Stromal Cells in the Knee of Patients with Severe Osteoarthritis has a Systemic Effect and Promotes an Anti-Inflammatory Phenotype of Circulating Immune Cells

Rationale: Recent studies confirmed that osteoarthritis (OA) is associated with systemic inflammation. Adipose-derived stromal cells (ASCs) could become the most promising cell-based therapy in OA, based not only on their differentiation capacities and trophic and paracrine effects on the existing cartilage, but also on their immunomodulatory properties. Here, we wanted to determine the biological effect of autologous ASC intra-articular (IA) injection.

Method: To this aim, we monitored the profile of immune cells in fresh peripheral blood after IA injection of autologous ASCs in the knee of 18 patients with severe OA (ADIPOA phase I study). Specifically, we used 8-color flow cytometry antibody panels to characterize the frequencies of innate and adaptive immune cell subsets (monocytes, dendritic cells, regulatory T cells and B cells) in blood samples at baseline (before injection) and one week, one month and three months after ASC injection.

Results: We found that the percentage of CD4⁺CD25^highCD127^lowFOXP3⁺ regulatory T cells was significantly increased at 1 month after ASC injection, and this effect persisted for at least 3 months. Moreover, CD24^highCD38^high transitional B cells also were increased, whereas the percentage of classical CD14⁺ monocytes was decreased, at 3 months after ASC injection. These results suggest a global switch toward regulatory immune cells following IA injection of ASCs, underscoring the safety of ASC-based therapy. We did not find any correlation between the scores for the Visual Analogic Scale for pain, the Western Ontario and McMaster Universities Osteoarthritis Index (pain subscale and total score) at baseline and the immune cell profile changes, but this could be due to the small number of analyzed patients.

Conclusion: ASCs may drive an immediate local response by releasing paracrine factors and cytokines, and our results suggest that ASCs could also initiate a cascade resulting in a long-lasting systemic immune modulation.

Characterization of embryonic stem cell-differentiated fibroblasts as mesenchymal stem cells with robust expansion capacity and attenuated innate immunity

BACKGROUND

Mesenchymal stem cells (MSCs) isolated from adult tissues (Ad-MSCs) have shown great promise for use in regenerative medicine. However, their poor in vitro expansion capacity and tissue scarcity have been major limitations. In this study, we demonstrate that mouse embryonic stem cells (mESCs) can differentiate into cells with MSC properties.

METHODS

Using previously established methods that characterize Ad-MSCs, we analyzed mESC-differentiated fibroblasts (mESC-FBs), including plastic adherence, clonogenic growth, MSC marker expression, tri-lineage differentiation potential, and the capacity to express immunomodulators.

RESULTS

Although previously characterized as mESC-differentiated fibroblasts (mESC-FBs), these cells exhibit major properties of Ad-MSCs. However, mESC-FBs also display unique features inherited from ESCs, including robust expansion capacity, senescence resistance, and attenuated innate immunity. In particular, mESC-FBs are insensitive to bacterial endotoxin (lipopolysaccharide, LPS) and do not express LPS-induced inflammatory molecules, in contrast to bone marrow (BM)-MSCs. We further demonstrate that mESC-FBs are resistant to the cytotoxicity associated with inflammatory cytokines, bacterial endotoxins (LPS and heat-killed bacteria), and macrophage-mediated inflammation.

CONCLUSIONS

While it remains to be determined how the unique properties of mESC-FBs will affect their immunoregulatory activity under an in vivo condition, our findings demonstrate that ESCs could be used as an alternative source to generate a new class of ESC-MSCs with unique features potentially useful in regenerative medicine.

Mesenchymal stem cells alleviate experimental autoimmune cholangitis through immunosuppression and cytoprotective function mediated by galectin-9

Background

Mesenchymal stem cells (MSCs) play an anti-inflammatory role by secreting certain bioactive molecules to exert their therapeutic effects for disease treatment. However, the underlying mechanism of MSCs in chronic autoimmune liver diseases—primary biliary cholangitis (PBC), for example—remains to be elucidated.

Methods

Human umbilical cord–derived MSCs (UC-MSCs) were injected intravenously into 2-octynoic acid coupled to bovine serum albumin (2OA-BSA)-induced autoimmune cholangitis mice. Serum levels of biomarkers and autoantibodies, histologic changes in the liver, diverse CD4⁺ T-cell subsets in different tissues, and chemokine activities were analyzed. Moreover, we investigated galectin-9 (Gal-9) expression and its function in UC-MSCs.

Results

In this study, UC-MSC transplantation (UC-MSCT) significantly ameliorated liver inflammation, primarily by diminishing T helper 1 (Th1) and Th17 responses as well as modifying liver chemokine activities in experimental autoimmune cholangitis mice. Mechanistically, UC-MSCs significantly repressed the proliferation of CD4⁺ T cells and suppressed the differentiation of Th1 and Th17 cells, which was likely dependent on Gal-9. Furthermore, the signal transducer and activator of transcription (STAT) and c-Jun N-terminal kinase (JNK) signaling pathways were involved in the production of Gal-9 in UC-MSCs.

Conclusions

These results suggest that Gal-9 contributes significantly to UC-MSC–mediated therapeutic effects and improve our understanding of the immunomodulatory mechanisms of MSCs in the treatment of PBC.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0979-x) contains supplementary material, which is available to authorized users.

Current Strategies to Generate Human Mesenchymal Stem Cells In Vitro

Mesenchymal stem cells (MSCs) are heterogeneous multipotent stem cells that are involved in the development of mesenchyme-derived evolving structures and organs during ontogeny. In the adult organism, reservoirs of MSCs can be found in almost all tissues where MSCs contribute to the maintenance of organ integrity. The use of these different MSCs for cell-based therapies has been extensively studied over the past years, which highlights the use of MSCs as a promising option for the treatment of various diseases including autoimmune and cardiovascular disorders. However, the proportion of MSCs contained in primary isolates of adult tissue biopsies is rather low and, thus, vigorous ex vivo expansion is needed especially for therapies that may require extensive and repetitive cell substitution. Therefore, more easily and accessible sources of MSCs are needed. This review summarizes the current knowledge of the different strategies to generate human MSCs in vitro as an alternative method for their applications in regenerative therapy.

Approaches in Immunotherapy, Regenerative Medicine, and Bioengineering for Type 1 Diabetes

Recent advances on using immune and stem cells as two-pronged approaches for type 1 diabetes mellitus (T1DM) treatment show promise for advancement into clinical practice. As T1DM is thought to arise from autoimmune attack destroying pancreatic β-cells, increasing treatments that use biologics and cells to manipulate the immune system are achieving better results in pre-clinical and clinical studies. Increasingly, focus has shifted from small molecule drugs that suppress the immune system nonspecifically to more complex biologics that show enhanced efficacy due to their selectivity for specific types of immune cells. Approaches that seek to inhibit only autoreactive effector T cells or enhance the suppressive regulatory T cell subset are showing remarkable promise. These modern immune interventions are also enabling the transplantation of pancreatic islets or β-like cells derived from stem cells. While complete immune tolerance and body acceptance of grafted islets and cells is still challenging, bioengineering approaches that shield the implanted cells are also advancing. Integrating immunotherapy, stem cell-mediated β-cell or islet production and bioengineering to interface with the patient is expected to lead to a durable cure or pave the way for a clinical solution for T1DM.

Mesenchymal stromal cells from human umbilical cord prevent the development of lung fibrosis in immunocompetent mice

Lung fibrosis is a severe condition resulting from several interstial lung diseases (ILD) with different etiologies. Current therapy of ILD, especially those associated with connective tissue diseases, is rather limited and new anti-fibrotic strategies are needed. In this study, we investigated the anti-fibrotic activity in vivo of human mesenchymal stromal cells obtained from whole umbilical cord (hUC-MSC). Adult immunocompetent C57BL/6 mice (n. = 8 for each experimental condition) were injected intravenously with hUC-MSC (n. = 2.5 × 10⁵) twice, 24 hours and 7 days after endotracheal injection of bleomycin. Upon sacrifice at days 8, 14, 21, collagen content, inflammatory cytokine profile, and hUC-MSC presence in explanted lung tissue were analyzed. Systemic administration of a double dose of hUC-MSC significantly reduced bleomycin-induced lung injury (inflammation and fibrosis) in mice through a selective inhibition of the IL6-IL10-TGFβ axis involving lung M2 macrophages. Only few hUC-MSC were detected from explanted lungs, suggesting a “hit and run” mechanism of action of this cellular therapy. Our data indicate that hUC-MSC possess strong in vivo anti-fibrotic activity in a mouse model resembling an immunocompetent human subject affected by inflammatory ILD, providing proof of concept for ad-hoc clinical trials.

Update on research and clinical translation on specific clinical areas from biology to bedside: Unpacking the mysteries of juvenile idiopathic arthritis pathogenesis

In the past decades, we have gained important insights into the mechanisms of disease and therapy underlying chronic inflammation in juvenile idiopathic arthritis (JIA). These insights have resulted in several game-changing therapeutic modalities for many patients. However, additional progress still has to be made with regard to efficacy, cost reduction, minimization of side effects, and dose-tapering and stop strategies of maintenance drugs. Moreover, to really transform the current therapeutic strategies into personalized medicine, we need validated biomarkers to translate increased insights into clinical practice. In this article, we describe recent developments in JIA research and outline how clinical innovations need to go hand in hand with basic discoveries to really effect care for patients. Facilitating the transition from bench to bedside is crucial for addressing the major current challenges in JIA management. When successful, it will set new standards for a safe, targeted, and personalized medicine in JIA.

Differentiation of Mesenchymal Stem Cells from Human Induced Pluripotent Stem Cells Results in Downregulation of c-Myc and DNA Replication Pathways with Immunomodulation Toward CD4 and CD8 Cells

Multilineage tissue-source mesenchymal stem cells (MSCs) possess strong immunomodulatory properties and are excellent therapeutic agents, but require constant isolation from donors to combat replicative senescence. The differentiation of human induced pluripotent stem cells (iPSCs) into MSCs offers a renewable source of MSCs; however, reports on their immunomodulatory capacity have been discrepant. Using MSCs differentiated from iPSCs reprogrammed using diverse cell types and protocols, and in comparison to human embryonic stem cell (ESC)-MSCs and bone marrow (BM)-MSCs, we performed transcriptome analyses and assessed for functional immunomodulatory properties. Differentiation of MSCs from iPSCs results in decreased c-Myc expression and its downstream pathway along with a concomitant downregulation in the DNA replication pathway. All four lines of iPSC-MSCs can significantly suppress in vitro activated human peripheral blood mononuclear cell (PBMC) proliferation to a similar degree as ESC-MSCs and BM-MSCs, and modulate CD4 T lymphocyte fate from a type 1 helper T cell (Th1) and IL-17A-expressing (Th17) cell fate to a regulatory T cell (Treg) phenotype. Moreover, iPSC-MSCs significantly suppress cytotoxic CD8 T proliferation, activation, and differentiation into type 1 cytotoxic T (Tc1) and IL-17-expressing CD8 T (Tc17) cells. Coculture of activated PBMCs with human iPSC-MSCs results in an overall shift of secreted cytokine profile from a pro-inflammatory environment to a more immunotolerant milieu. iPSC-MSC immunomodulation was also validated in vivo in a mouse model of induced inflammation. These findings support that iPSC-MSCs possess low oncogenicity and strong immunomodulatory properties regardless of cell-of-origin or reprogramming method and are good potential candidates for therapeutic use. Stem Cells 2018;36:903-914.

Hematopoietic and mesenchymal stem cells: a promising new therapy for spondyloarthritis?

In the last years, a considerable progress has been made in the treatment of spondyloarthritides. Nonetheless, there remain a considerable number of patients who are unresponsive to all current therapies. Since the late 1990s, numerous trials have investigated the use of stem cell transplantation as a new approach for the treatment of autoimmune disease, particularly with hematopoietic stem cell transplantation. More recently, the research has focused on mesenchymal stem cell application due to their low immunogenicity and immunomodulatory properties. In this article, we summarize available data on hematopoietic stem cell and mesenchymal stem cell use for the treatment of spondyloarthritides and discuss the data gaps and possible research agenda in this area.

The roles of dermal white adipose tissue loss in scleroderma skin fibrosis

PURPOSE OF REVIEW

Dermal white adipose tissue (DWAT) is distinct from subcutaneous white adipose tissue and is lost in scleroderma skin fibrosis. The roles of DWAT loss in scleroderma skin fibrosis have not been well understood, and here we discuss recent findings that begin to provide insight into the multiple mechanisms involved.

RECENT FINDINGS

The DWAT loss in part reflects the direct contribution of DWAT cells to the fibrotic tissue, with the reprogramming of adipocytes to myofibroblasts. The DWAT contains reparative adipose-derived stromal cells and expresses antifibrotic cytokines such as adiponectin, and the loss of these skin-protective mechanisms with DWAT loss further contributes to skin fibrosis and injury.

SUMMARY

Potentially, halting or reversing the transdifferentiation of adipocytes to myofibroblasts along with improving survival of reparative adipose-derived stromal cells (ADSCs) and expression of antifibrotic cytokines may be effective therapeutic avenues.

Mesenchymal stem cell therapy to promote corneal allograft survival: current status and pathway to clinical translation

PURPOSE OF REVIEW

This article reviews the literature on the therapeutic potential of mesenchymal stem cells (MSCs) to prolong corneal allograft survival.

RECENT FINDINGS

To date, only small numbers studies have investigated the MSC ability to modulate corneal allograft survival. Most reports have shown positive results, which is encouraging, however as different MSC-application strategies (time point of injection, cell number/number of injections, route of injection, MSC source, MSC licensing) have been employed in various animal models it is difficult to compare and validate the results. The MSC ability to promote graft survival has been attributed to their modulation of the recipient immune system, altering the Th1/Th2 balance, expanding Foxp3 regulatory T cells, polarizing macrophages and inhibiting intra-graft infiltration of antigen presenting cells. More in depth analysis is required to elucidate the mechanism of MSC-immunomodulation in vivo.

SUMMARY

MSCs have shown the potential to modulate corneal allograft rejection in various models using MSCs from different species. In particular for high-risk patients with poor prognosis MSC therapy might be a promising approach to promote corneal allograft survival. First-in-man clinical trials with MSC will hopefully shed new light on MSC-mediated immunomodulation in vivo and contribute to the restoration of vision in patients receiving corneal allografts.

TREM-2 negatively regulates LPS-mediated inflammatory response in rat bone marrow-derived MSCs

To the best of our knowledge, our previous study demonstrated the expression of triggering receptor expressed on myeloid cells 2 (TREM-2) in human bone marrow mesenchymal stem cells (MSCs) for the first time. However, the inflammation regulatory role of TREM-2 in MSCs remain elusive. The aim of the present study was to investigate the immune regulation and the underlying mechanism of TREM-2 in rat bone marrow MSCs. MSCs were divided into three groups: ^NullMSCs, ^TREM-2MSCs, and ^NormMSCs. TREM-2 was expressed in MSCs at the mRNA and protein level. Following stimulation by lipopolysaccharide (LPS), the gene transcription levels of TREM-2 and inflammatory cytokines were increased. The expression levels of inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), in the ^TREM-2MSCs lentiviral vector group were significantly downregulated, and the expression of IL-10 was significantly upregulated compared with the controls. Western blot analysis revealed that TREM-2 downregulated the LPS-induced inflammatory response in MSCs, which was probably associated with regulating AKT serine/threonine kinase and p38 mitogen-activated protein kinase downstream signaling proteins. The results of the current study demonstrated that TREM-2 negatively regulates the LPS-mediated inflammatory response in MSCs suggesting that TREM-2 is a potential target of immune regulation in rat MSCs.

Serum IFN-γ Predicts the Therapeutic Effect of Mesenchymal Stem Cells Transplantation in Systemic Lupus Erythematosus Patients

Umbilical cord (UC)-derived mesenchymal stem cells (MSCs) show immunoregulatory properties on various immune cells and display therapeutic effects on various autoimmune diseases such as systemic lupus erythematosus (SLE). The aim of this study was to investigate the effect of the SLE environment on UC MSCs and to identify a potential serum biomarker to predict the therapeutic effect. UC MSCs were cocultured with peripheral blood mononuclear cells (PBMCs) from active lupus patients, and the proliferation, apoptosis and surface markers of UC MSCs were observed. UC MSC functional molecules were assessed by real-time polymerase chain reaction, and the signaling pathways were analyzed by Western blot. The clinical effect of MSC transplantation (MSCT) for lupus patients was followed-up, whereas baseline serum cytokines were analyzed by enzyme-linked immunosorbent assay. The coculture of PBMC from lupus patients promoted MSC proliferation. Lupus PBMCs were more potent in stimulating UC MSCs to secrete vascular endothelial growth factor (VEGF) and CXCL-12. Furthermore, lupus PBMCs activated Akt, IκB, and Stat5 signaling pathways in UC MSCs but did not affect Erk1/2 and Smad1/5/8 pathways. Moreover, our clinical study showed that higher baseline levels of IFN-γ might predict a good response to MSCT in active lupus patients. Baseline IFN-γ levels may predict clinical response to MSC therapy for active lupus patients, which will help to choose suitable patients for clinical transplantation. Stem Cells Translational Medicine 2017;6:1777-1785.

Hypoxia Impairs Mesenchymal Stromal Cell-Induced Macrophage M1 to M2 Transition

The transition of macrophages from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype is crucial for the progression of normal wound healing. Persistent M1 macrophages within the injury site may lead to an uncontrolled macrophage-mediated inflammatory response and ultimately a failure of the wound healing cascade, leading to chronic wounds. Mesenchymal stromal cells (MSCs) have been widely reported to promote M1 to M2 macrophage transition; however, it is unclear whether MSCs can drive this transition in the hypoxic environment typically observed in chronic wounds. Here we report on the effect of hypoxia (1% O₂) on MSCs' ability to transition macrophages from the M1 to the M2 phenotype. While hypoxia had no effect on MSC secretion, it inhibited MSC-induced M1 to M2 macrophage transition, and suppressed macrophage expression and production of the anti-inflammatory mediator interleukin-10 (IL-10). These results suggest that hypoxic environments may impede the therapeutic effects of MSCs.

In Vitro Generation of Vascular Wall-Resident Multipotent Stem Cells of Mesenchymal Nature from Murine Induced Pluripotent Stem Cells

The vascular wall (VW) serves as a niche for mesenchymal stem cells (MSCs). In general, tissue-specific stem cells differentiate mainly to the tissue type from which they derive, indicating that there is a certain code or priming within the cells as determined by the tissue of origin. Here we report the in vitro generation of VW-typical MSCs from induced pluripotent stem cells (iPSCs), based on a VW-MSC-specific gene code. Using a lentiviral vector expressing the so-called Yamanaka factors, we reprogrammed tail dermal fibroblasts from transgenic mice containing the GFP gene integrated into the Nestin-locus (NEST-iPSCs) to facilitate lineage tracing after subsequent MSC differentiation. A lentiviral vector expressing a small set of recently identified human VW-MSC-specific HOX genes then induced MSC differentiation. This direct programming approach successfully mediated the generation of VW-typical MSCs with classical MSC characteristics, both in vitro and in vivo.

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In vitro generation of (VW)-typical MSCs from iPSCs based on a specific HOX code

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Reprogrammed fibroblasts (NEST-iPSCs) facilitated lineage tracing

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A lentiviral vector expressing HOXB7, HOXC6, and HOXC8 induced MSC differentiation

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Generated VW-MSCs showed classical MSC characteristics in vitro and in vivo

Human Umbilical Cord Mesenchymal Stem Cells Inhibit T Follicular Helper Cell Expansion Through the Activation of iNOS in Lupus-Prone B6.MRL-Faslpr Mice

The aberrant generation or activation of T follicular helper (Tfh) cells contributes to the pathogenesis of systemic lupus erythematosus (SLE), yet little is known about how these cells are regulated. In this study, we demonstrated that the frequency of Tfh cells was increased in lupus-prone B6.MRL-Faslpr (B6.lpr) mice and positively correlated to plasma cell proportions and serum total IgG as well as anti-dsDNA antibody levels. Transplantation of mesenchymal stem cells derived from Wharton's jelly of human umbilical cords (hUC-MSCs) ameliorated lupus symptoms in B6.lpr mice, along with decreased percentages of Tfh cells. In vitro studies showed that the differentiation and proliferation of Tfh cells were markedly suppressed by hUC-MSCs. The production of inducible nitric oxide synthase (iNOS) was dramatically upregulated in hUC-MSCs when cocultured with CD4+ T cells directly, while adding the specific inhibitor of iNOS into the coculture system significantly reversed the inhibitory effect of hUC-MSCs on Tfh cell generation. Interestingly, the efficacy of hUC-MSCs in inhibiting Tfh cells was impaired in the Transwell system, with the reduction of iNOS in both mRNA and protein levels. Taken together, our findings suggest that hUC-MSCs could effectively inhibit Tfh cell expansion through the activation of iNOS in lupus-prone B6.lpr mice, which is highly dependent on cell-to-cell contacts.

Proliferation and osteogenic differentiation of amniotic fluid-derived stem cells

The osteogenic differentiation of stem cells.

Lung regeneration: steps toward clinical implementation and use

PURPOSE OF REVIEW

Whole lung tissue engineering is a relatively new area of investigation. In a short time, however, the field has advanced quickly beyond proof of concept studies in rodents and now stands on the cusp of wide-spread scale up to large animal studies. Therefore, this technology is ever closer to being directly clinically relevant.

RECENT FINDINGS

The main themes in the literature include refinement of the fundamental components of whole lung engineering and increasing effort to direct induced pluripotent stem cells and lung progenitor cells toward use in lung regeneration. There is also increasing need for and emphasis on functional evaluation in the lab and in vivo, and the use of all of these tools to construct and evaluate forthcoming clinically scaled engineered lung.

SUMMARY

Ultimately, the goal of the research described herein is to create a useful clinical product. In the intermediate time, however, the tools described here may be employed to advance our knowledge of lung biology and the organ-specific regenerative capacity of lung stem and progenitor cells.

Human mesenchymal stem cells (MSCs) for treatment towards immune- and inflammation-mediated diseases: review of current clinical trials

Human mesenchymal stem cells (MSCs) are multilineage somatic progenitor/stem cells that have been shown to possess immunomodulatory properties in recent years. Initially met with much skepticism, MSC immunomodulation has now been well reproduced across tissue sources and species to be clinically relevant. This has opened up the use of these versatile cells for application as 3rd party/allogeneic use in cell replacement/tissue regeneration, as well as for immune- and inflammation-mediated disease entities. Most surprisingly, use of MSCs for in immune-/inflammation-mediated diseases appears to yield more efficacy than for regenerative medicine, since engraftment of the exogenous cell does not appear necessary. In this review, we focus on this non-traditional clinical use of a tissue-specific stem cell, and highlight important findings and trends in this exciting area of stem cell therapy.

Stem Cell Extracellular Vesicles: Extended Messages of Regeneration

Stem cells are critical to maintaining steady-state organ homeostasis and regenerating injured tissues. Recent intriguing reports implicate extracellular vesicles (EVs) as carriers for the distribution of morphogens and growth and differentiation factors from tissue parenchymal cells to stem cells, and conversely, stem cell-derived EVs carrying certain proteins and nucleic acids can support healing of injured tissues. We describe approaches to make use of engineered EVs as technology platforms in therapeutics and diagnostics in the context of stem cells. For some regenerative therapies, natural and engineered EVs from stem cells may be superior to single-molecule drugs, biologics, whole cells, and synthetic liposome or nanoparticle formulations because of the ease of bioengineering with multiple factors while retaining superior biocompatibility and biostability and posing fewer risks for abnormal differentiation or neoplastic transformation. Finally, we provide an overview of current challenges and future directions of EVs as potential therapeutic alternatives to cells for clinical applications.

Dendritic cells maintain dermal adipose-derived stromal cells in skin fibrosis

Scleroderma is a group of skin-fibrosing diseases for which there are no effective treatments. A feature of the skin fibrosis typical of scleroderma is atrophy of the dermal white adipose tissue (DWAT). Adipose tissue contains adipose-derived mesenchymal stromal cells (ADSCs) that have regenerative and reparative functions; however, whether DWAT atrophy in fibrosis is accompanied by ADSC loss is poorly understood, as are the mechanisms that might maintain ADSC survival in fibrotic skin. Here, we have shown that DWAT ADSC numbers were reduced, likely because of cell death, in 2 murine models of scleroderma skin fibrosis. The remaining ADSCs showed a partial dependence on dendritic cells (DCs) for survival. Lymphotoxin β (LTβ) expression in DCs maintained ADSC survival in fibrotic skin by activating an LTβ receptor/β1 integrin (LTβR/β1 integrin) pathway on ADSCs. Stimulation of LTβR augmented the engraftment of therapeutically injected ADSCs, which was associated with reductions in skin fibrosis and improved skin function. These findings provide insight into the effects of skin fibrosis on DWAT ADSCs, identify a DC-ADSC survival axis in fibrotic skin, and suggest an approach for improving mesenchymal stromal cell therapy in scleroderma and other diseases.

Dynamic Tracking Human Mesenchymal Stem Cells Tropism following Smoke Inhalation Injury in NOD/SCID Mice

Multiple preclinical evidences have supported the potential value of mesenchymal stem cells (MSCs) for treatment of acute lung injury (ALI). However, few studies focus on the dynamic tropism of MSCs in animals with acute lung injury. In this study, we track systemically transplanted human bone marrow-derived mesenchymal stem cells (hBMSCs) in NOD/SCID mice with smoke inhalation injury (SII) through bioluminescence imaging (BLI). The results showed that hBMSCs systemically delivered into healthy NOD/SCID mouse initially reside in the lungs and then partially translocate to the abdomen after 24 h. Compared with the uninjured control group treated with hBMSCs, higher numbers of hBMSCs were found in the lungs of the SII NOD/SCID mice. In both the uninjured and SII mice, the BLI signals in the lungs steadily decreased over time and disappeared by 5 days after treatment. hBMSCs significantly attenuated lung injury, elevated the levels of KGF, decreased the levels of TNF-α in BALF, and inhibited inflammatory cell infiltration in the mice with SII. In conclusion, our findings demonstrated that more systemically infused hBMSCs localized to the lungs in mice with SII. hBMSC xenografts repaired smoke inhalation-induced lung injury in mice. This repair was maybe due to the effect of anti-inflammatory and secreting KGF of hMSCs but not associated with the differentiation of the hBMSCs into alveolar epithelial cells.

In Vivo Tracking of Systemically Administered Allogeneic Bone Marrow Mesenchymal Stem Cells in Normal Rats through Bioluminescence Imaging

Recently, mesenchymal stem cells (MSCs) are increasingly used as a panacea for multiple types of disease short of effective treatment. Dozens of clinical trials published demonstrated strikingly positive therapeutic effects of MSCs. However, as a specific agent, little research has focused on the dynamic distribution of MSCs after in vivo administration. In this study, we track systemically transplanted allogeneic bone marrow mesenchymal stem cells (BMSCs) in normal rats through bioluminescence imaging (BLI) in real time. Ex vivo organ imaging, immunohistochemistry (IHC), and RT-PCR were conducted to verify the histological distribution of BMSCs. Our results showed that BMSCs home to the dorsal skin apart from the lungs and kidneys after tail vein injection and could not be detected 14 days later. Allogeneic BMSCs mainly appeared not at the parenchymatous organs but at the subepidermal connective tissue and adipose tissue in healthy rats. There were no significant MSCs-related adverse effects except for transient decrease in neutrophils. These findings will provide experimental evidences for a better understanding of the biocharacteristics of BMSCs.

Stem cell transplantation and mesenchymal cells to treat autoimmune diseases

Since the start of the international stem cell transplantation project in 1997, over 2000 patients have received a haematopoietic stem cell transplant (HSCT), mostly autologous, as treatment for a severe autoimmune disease, the majority being multiple sclerosis (MS), systemic sclerosis (SSc) and Crohn's disease. There was an overall 85% 5-year survival and 43% progression-free survival. Around 30% of patients in all disease subgroups had a complete response, often durable despite full immune reconstitution. In many cases, e.g. systemic sclerosis, morphological improvement such as reduction of skin collagen and normalization of microvasculature was documented, beyond any predicted known effects of intense immunosuppression alone. It is hoped that the results of the three running large prospective randomized controlled trials will allow modification of the protocols to reduce the high transplant-related mortality which relates to regimen intensity, age of patient, and comorbidity. Mesenchymal stromal cells (MSC), often incorrectly called stem cells, have been the intense focus of in vitro studies and animal models of rheumatic and other diseases over more than a decade. Despite multiple plausible mechanisms of action and a plethora of positive in vivo animal studies, few randomised controlled clinical trials have demonstrated meaningful clinical benefit in any condition so far. This could be due to confusion in cell product terminology, complexity of clinical study design and execution or agreement on meaningful outcome measures. Within the rheumatic diseases, SLE and rheumatoid arthritis (RA) have received most attention. Uncontrolled multiple trial data from over 300 SLE patients have been published from one centre suggesting a positive outcome; one single centre comparative study in 172 RA was positive. In addition, small numbers of patients with Crohn's disease, multiple sclerosis, primary Sjögren's disease, polymyositis/dermatomyositis and type II diabetes mellitus have received MSC therapeutically. The possible reasons for this apparent mismatch between expectation and clinical reality will be discussed.

Factors secreted from dental pulp stem cells show multifaceted benefits for treating experimental rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial hyperplasia and chronic inflammation, which lead to the progressive destruction of cartilage and bone in the joints. Numerous studies have reported that administrations of various types of MSCs improve arthritis symptoms in animal models, by paracrine mechanisms. However, the therapeutic effects of the secreted factors alone, without the cell graft, have been uncertain. Here, we show that a single intravenous administration of serum-free conditioned medium (CM) from human deciduous dental pulp stem cells (SHED-CM) into anti-collagen type II antibody-induced arthritis (CAIA), a mouse model of rheumatoid arthritis (RA), markedly improved the arthritis symptoms and joint destruction. The therapeutic efficacy of SHED-CM was associated with an induction of anti-inflammatory M2 macrophages in the CAIA joints and the abrogation of RANKL expression. SHED-CM specifically depleted of an M2 macrophage inducer, the secreted ectodomain of sialic acid-binding Ig-like lectin-9 (ED-Siglec-9), exhibited a reduced ability to induce M2-related gene expression and attenuate CAIA. SHED-CM also inhibited the RANKL-induced osteoclastogenesis in vitro. Collectively, our findings suggest that SHED-CM provides multifaceted therapeutic effects for treating CAIA, including the ED-Siglec-9-dependent induction of M2 macrophage polarization and inhibition of osteoclastogenesis. Thus, SHED-CM may represent a novel anti-inflammatory and reparative therapy for RA.

Are clinical trials with mesenchymal stem/progenitor cells too far ahead of the science? Lessons from experimental hematology

The cells referred to as mesenchymal stem/progenitor cells (MSCs) are currently being used to treat thousands of patients with diseases of essentially all the organs and tissues of the body. Strikingly positive results have been reported in some patients, but there have been few prospective controlled studies. Also, the reasons for the beneficial effects are frequently unclear. As a result there has been a heated debate as to whether the clinical trials with these new cell therapies are too far ahead of the science. The debate is not easily resolved, but important insights are provided by the 60-year history that was required to develop the first successful stem cell therapy, the transplantation of hematopoietic stem cells. The history indicates that development of a dramatically new therapy usually requires patience and a constant dialogue between basic scientists and physicians carrying out carefully designed clinical trials. It also suggests that the field can be moved forward by establishing better records of how MSCs are prepared, by establishing a large supply of reference MSCs that can be used to validate assays and compare MSCs prepared in different laboratories, and by continuing efforts to establish in vivo assays for the efficacy of MSCs. Stem Cells2014;32:3055–3061

The developmental basis of mesenchymal stem/stromal cells (MSCs)

BACKGROUND

Mesenchymal Stem/Stromal Cells (MSCs) define a population of progenitor cells capable of giving rises to at least three mesodermal lineages in vitro, the chondrocytes, osteoblasts and adipocytes. The validity of MSCs in vivo has been questioned because their existence, either as a homogeneous progenitor cell population or as a stem cell lineage, has been difficult to prove. The wide use of primary MSCs in regenerative and therapeutic applications raises ethical and regulatory concerns in many countries. In contrast to hematopoietic stem cells, a parallel concept which carries an embryological emphasis from its outset, MSCs have attracted little interest among developmental biologists and the embryological basis for their existence, or lack thereof, has not been carefully evaluated.

METHODS

This article provides a brief, embryological overview of these three mesoderm cell lineages and offers a framework of ontological rationales for the potential existence of MSCs in vivo.

RESULTS

Emphasis is given to the common somatic lateral plate mesoderm origin of the majority of body's adipose and skeletal tissues and of the major sources used for MSC derivation clinically. Support for the MSC hypothesis also comes from a large body of molecular and lineage analysis data in vivo.

CONCLUSIONS

It is concluded that despite the lack of a definitive proof, the MSC concept has a firm embryological basis and that advances in MSC research can be facilitated by achieving a better integration with developmental biology.

The regulation of the Treg/Th17 balance by mesenchymal stem cells in human systemic lupus erythematosus

BACKGROUND AND OBJECTIVE

Umbilical cord (UC)-derived mesenchymal stem cells (MSCs) have shown immunoregulation of various immune cells. The aim of this study was to investigate the mechanism of UC MSCs in the regulation of peripheral regulatory T cells (Treg) and T helper 17 (Th17) cells in patients with systemic lupus erythematosus (SLE).

METHODS

Thirty patients with active SLE, refractory to conventional therapies, were given UC MSCs infusions. The percentages of peripheral blood CD4+CD25+Foxp3+ regulatory T cells (Treg) and CD3+CD8-IL17A+ Th17 cells and the mean fluorescence intensities (MFI) of Foxp3 and IL-17 were measured at 1 week, 1 month, 3 months, 6 months, and 12 months after MSCs transplantation (MSCT). Serum cytokines, including transforming growth factor beta (TGF-β), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and IL-17A were detected using ELISA. Peripheral blood mononuclear cells from patients were collected and co-cultured with UC MSCs at ratios of 1:1, 10:1, and 50:1, respectively, for 72 h to detect the proportions of Treg and Th17 cells and the MFIs of Foxp3 and IL-17 were determined by flow cytometry. The cytokines in the supernatant solution were detected using ELISA. Inhibitors targeting TGF-β, IL-6, indoleamine 2,3-dioxygenase (IDO), and prostaglandin E2 were added to the co-culture system, and the percentages of Treg and Th17 cells were observed.

RESULTS

The percentage of peripheral Treg and Foxp3 MFI increased 1 week, 1 month, and 3 months after UC MSCs transplantation, while the Th17 proportion and MFI of IL-17 decreased 3 months, 6 months, and 12 months after the treatment, along with an increase in serum TGF-β at 1 week, 3 months, and 12 months and a decrease in serum TNF-α beginning at 1 week. There were no alterations in serums IL-6 and IL-17A before or after MSCT. In vitro studies showed that the UC MSCs dose-dependently up-regulated peripheral Treg proportion in SLE patients, which was not depended on cell-cell contact. However, the down-regulation of Th17 cells was not dose-dependently and also not depended on cell-cell contact. Supernatant TGF-β and IL-6 levels significantly increased, TNF-α significantly decreased, but IL-17A had no change after the co-culture. The addition of anti-TGF-β antibody significantly abrogated the up-regulation of Treg, and the addition of PGE2 inhibitor significantly abrogated the down-regulation of Th17 cells. Both anti-IL-6 antibody and IDO inhibitor had no effects on Treg and Th17 cells.

CONCLUSIONS

UC MSCs up-regulate Treg and down-regulate Th17 cells through the regulation of TGF-β and PGE2 in lupus patients.