Concise Review: Multifaceted Characterization of Human Mesenchymal Stem Cells for Use in Regenerative Medicine

Endothelial progenitor cells promote osteogenic differentiation in co-cultured with mesenchymal stem cells via the MAPK-dependent pathway

BACKGROUND

The role of bone tissue engineering is to regenerate tissue using biomaterials and stem cell-based approaches. Combination of two or more cell types is one of the strategies to promote bone formation. Endothelial progenitor cells (EPCs) may enhance the osteogenic properties of mesenchymal stem cells (MSCs) and promote bone healing; this study aimed to investigate the possible mechanisms of EPCs on promoting osteogenic differentiation of MSCs.

METHODS

MSCs and EPCs were isolated and co-cultured in Transwell chambers, the effects of EPCs on the regulation of MSC biological properties were investigated. Real-time PCR array, and western blotting were performed to explore possible signaling pathways involved in osteogenesis. The expression of osteogenesis markers and calcium nodule formation was quantified by qRT-PCR, western blotting, and Alizarin Red staining.

RESULTS

Results showed that MSCs exhibited greater alkaline phosphatase (ALP) activity and increased calcium mineral deposition significantly when co-cultured with EPCs. The mitogen-activated protein kinase (MAPK) signaling pathway was involved in this process. p38 gene expression and p38 protein phosphorylation levels showed significant upregulation in co-cultured MSCs. Silencing expression of p38 in co-cultured MSCs reduced osteogenic gene expression, protein synthesis, ALP activity, and calcium nodule formation.

CONCLUSIONS

These data suggest paracrine signaling from EPCs influences the biological function and promotes MSCs osteogenic differentiation. Activation of the p38MAPK pathway may be the key to enhancing MSCs osteogenic differentiation via indirect interactions with EPCs.

The Crosstalk of Adipose-Derived Stem Cells (ADSC), Oxidative Stress, and Inflammation in Protective and Adaptive Responses

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties.

Emerging Prospects of Exosomes for Cancer Treatment: From Conventional Therapy to Immunotherapy

Exosomes are a class of extracellular vesicles of around 100 nm in diameter that are secreted by most cells and contain various bioactive molecules reflecting their cellular origin and mediate intercellular communication. Studies of these exosomal features in tumor pathogenesis have led to the development of therapeutic and diagnostic approaches using exosomes for cancer therapy. Exosomes have many advantages for conveying therapeutic agents such as small interfering RNAs, microRNAs, membrane-associated proteins, and chemotherapeutic compounds; thus, they are considered a prime candidate as a delivery tool for cancer treatment. Since exosomes also provide an optimal microenvironment for the effective function of immunomodulatory factors, exosomes harboring bioactive molecules have been bioengineered as cancer immunotherapies that can effectively activate each stage of the cancer immunity cycle to successfully elicit cancer-specific immunity. This review discusses the advantages of exosomes for treating cancer and the challenges that must be overcome for their successful clinical development.

Comparing the Effect of TGF-β Receptor Inhibition on Human Perivascular Mesenchymal Stromal Cells Derived from Endometrium, Bone Marrow and Adipose Tissues

Rare perivascular mesenchymal stromal cells (MSCs) with therapeutic properties have been identified in many tissues. Their rarity necessitates extensive in vitro expansion, resulting in spontaneous differentiation, cellular senescence and apoptosis, producing therapeutic products with variable quality and decreased potency. We previously demonstrated that A83-01, a transforming growth factor beta (TGF-β) receptor inhibitor, maintained clonogenicity and promoted the potency of culture-expanded premenopausal endometrial MSCs using functional assays and whole-transcriptome sequencing. Here, we compared the effects of A83-01 on MSCs derived from postmenopausal endometrium, menstrual blood, placenta decidua-basalis, bone marrow and adipose tissue. Sushi-domain-containing-2 (SUSD2⁺) and CD34⁺CD31⁻CD45⁻ MSCs were isolated. Expanded MSCs were cultured with or without A83-01 for 7 days and assessed for MSC properties. SUSD2 identified perivascular cells in the placental decidua-basalis, and their maternal origin was validated. A83-01 promoted MSC proliferation from all sources except bone marrow and only increased SUSD2 expression and prevented apoptosis in MSCs from endometrial-derived tissues. A83-01 only improved the cloning efficiency of postmenopausal endometrial MSCs (eMSCs), and expanded adipose tissue MSCs (adMSCs) underwent significant senescence, which was mitigated by A83-01. MSCs derived from bone marrow (bmMSCs) were highly apoptotic, but A83-01 was without effect. A83-01 maintained the function and phenotype in MSCs cultured from endometrial, but not other, tissues. Our results also demonstrated that cellular SUSD2 expression directly correlates with the functional phenotype.

From Mesenchymal Stromal/Stem Cells to Insulin-Producing Cells: Progress and Challenges

Mesenchymal stromal cells (MSCs) are an attractive option for cell therapy for type 1 diabetes mellitus (DM). These cells can be obtained from many sources, but bone marrow and adipose tissue are the most studied. MSCs have distinct advantages since they are nonteratogenic, nonimmunogenic and have immunomodulatory functions. Insulin-producing cells (IPCs) can be generated from MSCs by gene transfection, gene editing or directed differentiation. For directed differentiation, MSCs are usually cultured in a glucose-rich medium with various growth and activation factors. The resulting IPCs can control chemically-induced diabetes in immune-deficient mice. These findings are comparable to those obtained from pluripotent cells. PD-L1 and PD-L2 expression by MSCs is upregulated under inflammatory conditions. Immunomodulation occurs due to the interaction between these ligands and PD-1 receptors on T lymphocytes. If this function is maintained after differentiation, life-long immunosuppression or encapsulation could be avoided. In the clinical setting, two sites can be used for transplantation of IPCs: the subcutaneous tissue and the omentum. A 2-stage procedure is required for the former and a laparoscopic procedure for the latter. For either site, cells should be transplanted within a scaffold, preferably one from fibrin. Several questions remain unanswered. Will the transplanted cells be affected by the antibodies involved in the pathogenesis of type 1 DM? What is the functional longevity of these cells following their transplantation? These issues have to be addressed before clinical translation is attempted. Graphical Abstract Bone marrow MSCs are isolated from the long bone of SD rats. Then they are expanded and through directed differentiation insulin-producing cells are formed. The differentiated cells are loaded onto a collagen scaffold. If one-stage transplantation is planned, a drug delivery system must be incorporated to ensure immediate oxygenation, promote vascularization and provide some growth factors. Some mechanisms involved in the immunomodulatory function of MSCs. These are implemented either by cell to cell contact or by the release of soluble factors. Collectively, these pathways results in an increase in T-regulatory cells.

Mesenchymal stem cells: amazing remedies for bone and cartilage defects

Skeletal disorders are among the leading debilitating factors affecting millions of people worldwide. The use of stem cells for tissue repair has raised many promises in various medical fields, including skeletal disorders. Mesenchymal stem cells (MSCs) are multipotent stromal cells with mesodermal and neural crest origin. These cells are one of the most attractive candidates in regenerative medicine, and their use could be helpful in repairing and regeneration of skeletal disorders through several mechanisms including homing, angiogenesis, differentiation, and response to inflammatory condition. The most widely studied sources of MSCs are bone marrow (BM), adipose tissue, muscle, umbilical cord (UC), umbilical cord blood (UCB), placenta (PL), Wharton's jelly (WJ), and amniotic fluid. These cells are capable of differentiating into osteoblasts, chondrocytes, adipocytes, and myocytes in vitro. MSCs obtained from various sources have diverse capabilities of secreting many different cytokines, growth factors, and chemokines. It is believed that the salutary effects of MSCs from different sources are not alike in terms of repairing or reformation of injured skeletal tissues. Accordingly, differential identification of MSCs' secretome enables us to make optimal choices in skeletal disorders considering various sources. This review discusses and compares the therapeutic abilities of MSCs from different sources for bone and cartilage diseases.

Mesenchymal Stem Cells (MSCs) as a Potential Therapeutic Strategy in COVID-19 Patients: Literature Research

In 2019, an outbreak of an unknown coronavirus - SARS-CoV-2 - responsible for COVID-19 disease, was first reported in China, and evolved into a pandemic of huge dimensions and raised serious concerns for global health. The number of critical cases continues to increase dramatically, while vaccines and specific treatments are not yet available. There are several strategies currently being studied for the treatment of adverse symptoms of COVID-19, that encompass Acute Lung Injury (ALI)/Acute Respiratory Distress Syndrome (ARDS), extensive pulmonary inflammation, cytokine storm, and pulmonary edema, due to virus-induced pneumonia. Mesenchymal stem cells (MSCs) are at the origin of new revolutionary treatments, which may come to be applied in such as Regenerative Medicine, Immunotherapy, Tissue Engineering, and Cell and Molecular Biology due to immunomodulation and anti-inflammatory activity. MSCs have already been studied with positive outcomes for other lung pathologies, thus representing and being identified as an important opportunity for the treatment of COVID-19. It has recently been shown that these cells allow hopeful and effective therapies for serious or critical COVID-19, minimizing its adverse symptoms. In this study we will analyze the MSCs, their origin, differentiation, and therapeutic potential, making a bridge with the COVID-19 disease and its characteristics, as a potential therapeutic strategy but also reporting recent studies where these cell-based therapies were used for the treatment of COVID-19 patients.

Autophagy: a promising therapeutic target for improving mesenchymal stem cell biological functions

Mesenchymal stem cells (MSCs) are considered to be a promising therapeutic material due to their capacities for self-renewal, multilineage differentiation, and immunomodulation and have attracted great attention in regenerative medicine. However, MSCs may lose their biological functions because of donor age or disease and environmental pressure before and after transplantation, which hinders the application of MSC-based therapy. As a major intracellular lysosome-dependent degradative process, autophagy plays a pivotal role in maintaining cellular homeostasis and withstanding environmental pressure and may become a potential therapeutic target for improving MSC functions. Recent studies have demonstrated that the regulation of autophagy is a promising approach for improving the biological properties of MSCs. More in-depth investigations about the role of autophagy in MSC biology are required to contribute to the clinical application of MSCs. In this review, we focus on the role of autophagy regulation by various physical and chemical factors on the biological functions of MSCs in vitro and in vivo, and provide some strategies for enhancing the therapeutic efficacy of MSCs.

Long-term and label-free monitoring for osteogenic differentiation of mesenchymal stem cells using force sensor and impedance measurement

Stem cells have attracted increasing research interest in the field of regenerative medicine due to their unique abilities to differentiate into multiple cell lineages. Label-free, real-time, and long-term monitoring for stem cell differentiation is requisite in studying directional differentiation and development mechanisms for tissue engineering applications, but a great challenge because of the rigorous demands for sensitivity, stability and biocompatibility of devices. In this article, a label-free and real-time monitoring approach using a zinc oxide (ZnO) nanorod field effect transistor (FET) is proposed to detect cell traction forces (CTFs) exerted by cells on underlying substrates. The ZnO nanorod FET with the approach of difference-frequency lock-in detection achieves high sensitivity, good stability, and excellent biocompatibility, by which real-time and long-term (over 20 days) monitoring of cellular mechanical changes in osteogenic differentiation of mesenchymal stem cells (MSCs) is successfully achieved. We also employ electrical impedance monitoring using microelectrode array chips and microscopic observation to investigate cell migration and nodular aggregation behaviors of MSCs in osteogenic differentiation. Various biochemical assays including alkaline phosphatase (ALP), osteopontin expression and alizarin red staining are utilized to verify osteogenic differentiation of MSCs. We propose a combination of cell traction force measurement, impedance measurement and microscopic observation to provide multimodal profiling of cell morphology, and cellular biomechanical and electrophysiological phenotypes, which can track cellular dynamics in stem cell development and help to deeply understand the mechanism of osteogenic differentiation.

Acute Lung Injury: Disease Modelling and the Therapeutic Potential of Stem Cells

Acute lung injury (ALI) is a severe clinical condition with high morbidity and mortality that usually results in the development of multiple organ dysfunction. The complex pathophysiology of ALI seems to provide a wide range of targets that offer numerous therapeutic options. However, despite extensive studies of ALI pathophysiology and treatment, no effective pharmacotherapy is available. Increasing evidence from both preclinical and clinical studies supports the preventive and therapeutic effects of mesenchymal stem cells (MSCs) for treating ALI. As cell-based therapy poses the risk of occlusion in microvasculature or unregulated growth, MSC-derived extracellular vesicles (MSC-EVs) have been extensively studied as a new therapeutic strategy for non-cell based therapy. It is widely accepted that the therapeutic properties of MSCs are derived from soluble factors with paracrine or endocrine effects, and EVs are among the most important paracrine or endocrine vehicles that can deliver various soluble factors with a similar phenotype as the parent cell. Therapeutic effects of MSCs have been reported for various delivery approaches, diverse doses, multiple origins, and different times of administration, and MSC-EVs treatment may include but is not limited to these choices. The mechanisms by which MSCs and MSC-EVs may contribute to ALI treatment remain elusive and need further exploration. This review provides an overview of preclinical studies that support the application of MSC-EVs for treating ALI, and it discusses emerging opportunities and their associated challenges.

The MSC-MCF-7 Duet Playing Tumor Vasculogenesis and Angiogenesis onto the Chick Embryo Chorioallantoic Membrane

BACKGROUND/AIM

Human mesenchymal stem cells (hMSC) represent a versatile cell population, able to modulate the tumor microenvironment. Our aim was to recreate an open scene for the in vivo interaction between hMSC and the MCF-7 breast cancer cells (MCF-7), in order to enlighten the intimate involvement of hMSC in tumor vasculogenesis and angiogenesis.

MATERIALS AND METHODS

hMSC and MCF-7 were seeded onto the chick embryo chorioallantoic membrane (CAM) and incubated for 7 days. Consecutively, the morphology and the immunohistochemical profile of CAM were assessed.

RESULTS

Following this complex interaction, MCF-7 acquired a more aggressive phenotype, hMSC switched to a vascular precursor phenotype, while CAM underwent a major reset to an earlier stage, with hotspots of angiogenesis, vasculogenesis and hematopoiesis.

CONCLUSION

The hallmark of this study was the establishment of a veritable in vivo experimental model of MSC involvement in tumor vasculogenesis and angiogenesis, allowing further analysis in the field.

Sensory nerves in the spotlight of the stem cell niche

Niches are specialized tissue microenvironments that control stem cells functioning. The bone marrow mesenchymal stem cell niche defines a location within the marrow in which mesenchymal stem cells are retained and produce new cells throughout life. Deciphering the signaling mechanisms by which the niche regulates stem cell fate will facilitate the use of these cells for therapy. Recent studies, by using state-of-the-art methodologies, including sophisticated in vivo inducible genetic techniques, such as lineage-tracing Cre/loxP mediated systems, in combination with pharmacological inhibition, provide evidence that sensory neuron is an important component of the bone marrow mesenchymal stem cell niche. Strikingly, knockout of a specific receptor in sensory neurons blocked stem cell function in the bone marrow. The knowledge arising from these discoveries will be crucial for stem cell manipulation in the future. Here, we review recent progress in our understanding of sensory nerves biology in the stem cell niche.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Vessel Wall-Derived Mesenchymal Stromal Cells Share Similar Differentiation Potential and Immunomodulatory Properties with Bone Marrow-Derived Stromal Cells

Purpose

This study is aimed at investigating the phenotype, differentiation potential, immunomodulatory properties, and responsiveness of saphenous vein vessel wall-derived mesenchymal stromal cells (SV-MSCs) to various TLR ligands and proinflammatory cytokines, as well as comparing their features to those of their bone marrow-derived counterparts (BM-MSCs).

Methods

SV-MSCs were isolated by enzymatic digestion of the saphenous vein vessel wall. Phenotype analysis was carried out by flow cytometry and microscopy, whereas adipogenic, chondrogenic, and osteogenic differentiation potentials were tested in in vitro assays. For comparative analysis, the expression of different stemness, proliferation, and differentiation-related genes was determined by Affymetrix gene array. To compare the immunomodulatory properties of SV-MSCs and BM-MSCs, mixed lymphocyte reaction was applied. To investigate their responses to various activating stimuli, MSCs were treated with TLR ligands (LPS, PolyI:C) or proinflammatory cytokines (TNFα, IL-1β, IFNγ), and the expression of various early innate immune response-related genes was assessed by qPCR, while secretion of selected cytokines and chemokines was measured by ELISA.

Results

The isolated SV-MSCs were able to differentiate into bone, fat, and cartilage cells/direction in vitro. SV-MSCs expressed the most important MSC markers (CD29, CD44, CD73, CD90, and CD105) and shared almost identical phenotypic characteristics with BM-MSCs. Their gene expression pattern and activation pathways were close to those of BM-MSCs. SV-MSCs showed better immunosuppressive activity inhibiting phytohemagglutinin-induced T lymphocyte proliferation in vitro than BM-MSCs. Cellular responses to treatments mimicking inflammatory conditions were comparable in the bone marrow- and saphenous vein-derived MSCs. Namely, similar to BM-MSCs, SV-MSCs secreted increased amount of IL-6 and IL-8 after 12- or 24-hour treatment with LPS, PolyI:C, TNFα, or IL-1β, compared to untreated controls. Interestingly, a different CXCL-10/IP-10 secretion pattern could be observed under inflammatory conditions in the two types of MSCs.

Conclusion

Based on our results, cells isolated from saphenous vein vessel wall fulfilled the ISCT's (International Society for Cellular Therapy) criteria for multipotent mesenchymal stromal cells, and no significant differences in the phenotype, gene expression pattern, and responsiveness to inflammatory stimuli could be observed between BM-MSCs and SV-MSCs, while the latter cells have more potent immunosuppressive activity in vitro. Further functional assays have to be performed to reveal whether SV-MSCs could be useful for certain regenerative therapeutic applications or tissue engineering purposes.

Differentiation Potential of Early- and Late-Passage Adipose-Derived Mesenchymal Stem Cells Cultured under Hypoxia and Normoxia

With an increasing focus on the large-scale expansion of mesenchymal stem cells (MSCs) required for clinical applications for the treatment of joint and bone diseases such as osteoarthritis, the optimisation of conditions for in vitro MSC expansion requires careful consideration to maintain native MSC characteristics. Physiological parameters such as oxygen concentration, media constituents, and passage numbers influence the properties of MSCs and may have major impact on their therapeutic potential. Cells grown under hypoxic conditions have been widely documented in clinical use. Culturing MSCs on large scale requires bioreactor culture; however, it is challenging to maintain low oxygen and other physiological parameters over several passages in large bioreactor vessels. The necessity to scale up the production of cells in vitro under normoxia may affect important attributes of MSCs. For these reasons, our study investigated the effects of normoxic and hypoxic culture condition on early- and late-passage adipose-derived MSCs. We examined effect of each condition on the expression of key stem cell marker genes POU5F1, NANOG, and KLF4, as well as differentiation genes RUNX2, COL1A1, SOX9, COL2A1, and PPARG. We found that expression levels of stem cell marker genes and osteogenic and chondrogenic genes were higher in normoxia compared to hypoxia. Furthermore, expression of these genes reduced with passage number, with the exception of PPARG, an adipose differentiation marker, possibly due to the adipose origin of the MSCs. We confirmed by flow cytometry the presence of cell surface markers CD105, CD73, and CD90 and lack of expression of CD45, CD34, CD14, and CD19 across all conditions. Furthermore, in vitro differentiation confirmed that both early- and late-passage adipose-derived MSCs grown in hypoxia or normoxia could differentiate into chondrogenic and osteogenic cell types. Our results demonstrate that the minimal standard criteria to define MSCs as suitable for laboratory-based and preclinical studies can be maintained in early- or late-passage MSCs cultured in hypoxia or normoxia. Therefore, any of these culture conditions could be used when scaling up MSCs in bioreactors for allogeneic clinical applications or tissue engineering for the treatment of joint and bone diseases such as osteoarthritis.

Spatio-Temporal Metabolokinetics and Efficacy of Human Placenta-Derived Mesenchymal Stem/Stromal Cells on Mice with Refractory Crohn's-like Enterocutaneous Fistula

Crohn's disease (CD) with externally fistulizing openings indicates the aggressive and relapsing manifestation and results in undesirable long-term outcomes of patients. MSC-based approach combined with multidisciplinary strategy has mandated a redefinition of the administration and management of numerous recurrent and refractory diseases whereas the spatio-temporal evaluation of the metabolokinetics and efficacy of MSCs on intractable CD with enterocutaneous fistula (EF) are largely inaccessible and dauntingly complex. Herein, we primitively established dual-fluorescence expressing placenta-derived MSCs (DF-MSCs) and explored their multidimensional attributes, including cytomorphology, immunophenotying, multilineage differentiation and long-term proliferation, together with the recognition of bifluorescence intensity (BLI). Then, with the aid of in vivo living imaging, clinicopathological or inflammatory cytokine examinations and in vitro analyses, we systematically and meticulously dissected the metabolokinetics and curative effect of MSCs on mice with refractory Crohn's-like EF (EF mice), together with revealing the underlying mechanism including reactive oxygen species (ROS) and neovascularization. Strikingly, the DF-MSCs exhibited stabilized BLI and biological properties. The spatio-temporal distribution and therapeutic process of MSCs in EF mice were intuitively delineated. Meanwhile, our data indicated the curative mechanisms of DF-MSCs by simultaneously downregulating ROS and accelerating neovascularization. Collectively, we systematically illuminated the spatio-temporal biofunction and mechanism of DF-MSCs on EF mice. Our findings have supplied new references for safety and effectiveness assessments as well as the establishment of guidelines for optimal administrations of MSC-based cytotherapy in preclinical studies, which collectively indicates the prospect of P-MSC administration in clinical trials during a wide spectrum of disease remodeling including the fistulizing CD. Graphical abstract.

Characterising Vascular Cell Monolayers Using Electrochemical Impedance Spectroscopy and a Novel Electroanalytical Plot

INTRODUCTION

Biological research relies on the culture of mammalian cells, which are prone to changes in phenotype during experiments involving several passages of cells. In regenerative medicine, specifically, there is an increasing need to expand the characterisation landscape for stem cells by identifying novel stable markers. This paper reports on a novel electric cell-substrate impedance sensing-based electroanalytical diagram which can be used for the "electrical characterisation" of cell monolayers consisting of smooth muscle cells, endothelial cells or co-culture.

MATERIALS AND METHODS

Interdigitated electrodes were microfabricated using standard cleanroom procedures and integrated into cell chambers. Electrochemical impedance spectroscopy data were acquired for 2 vascular cell types after they formed monolayers on the electrodes.

RESULTS AND DISCUSSION

A Mean impedance per unit area vs Mean phase plots provided a reproducible, visually obvious and statistically significant method of characterising cell monolayers. This electroanalytic diagram has never been used in previous papers, but it confirms findings by other research groups using similar approaches that the complex impedance spectra of different cell type are different. Further work is required to determine whether this method could be extended to other cell types, and if this is the case, a library of "signature spectra" could be generated for "electrical characterisation" of cells.

Mesenchymal Stromal Cell Immunology for Efficient and Safe Treatment of Osteoarthritis

Mesenchymal stem cell (MSC) therapy represents a promising approach for the treatment of osteoarthritis (OA). MSCs can be readily isolated from multiple sources and expanded ex vivo for possible clinical application. They possess a unique immunological profile and regulatory machinery that underline their therapeutic effects. They also have the capacity to sense the changes within the tissue environment to display the adequate response. Indeed, there is a close interaction between MSCs and the host cells. Accordingly, MSCs demonstrate encouraging results for a variety of diseases including OA. However, their effectiveness needs to be improved. In this review, we selected to discuss the importance of the immunological features of MSCs, including the type of transplantation and the immune and blood compatibility. It is important to consider MSC immune evasive rather than immune privileged. We also highlighted some of the actions/mechanisms that are displayed during tissue healing including the response of MSCs to injury signals, their interaction with the immune system, and the impact of their lifespan. Finally, we briefly summarized the results of clinical studies reporting on the application of MSCs for the treatment of OA. The research field of MSCs is inspiring and innovative but requires more knowledge about the immunobiological properties of these cells. A better understanding of these features will be key for developing a safe and efficient medicinal product for clinical use in OA.

Hurdles to uptake of mesenchymal stem cells and their progenitors in therapeutic products

Twenty-five years have passed since the first clinical trial utilising mesenchymal stomal/stem cells (MSCs) in 1995. In this time academic research has grown our understanding of MSC biochemistry and our ability to manipulate these cells in vitro using chemical, biomaterial, and mechanical methods. Research has been emboldened by the promise that MSCs can treat illness and repair damaged tissues through their capacity for immunomodulation and differentiation. Since 1995, 31 therapeutic products containing MSCs and/or progenitors have reached the market with the level of in vitro manipulation varying significantly. In this review, we summarise existing therapeutic products containing MSCs or mesenchymal progenitor cells and examine the challenges faced when developing new therapeutic products. Successful progression to clinical trial, and ultimately market, requires a thorough understanding of these hurdles at the earliest stages of in vitro pre-clinical development. It is beneficial to understand the health economic benefit for a new product and the reimbursement potential within various healthcare systems. Pre-clinical studies should be selected to demonstrate efficacy and safety for the specific clinical indication in humans, to avoid duplication of effort and minimise animal usage. Early consideration should also be given to manufacturing: how cell manipulation methods will integrate into highly controlled workflows and how they will be scaled up to produce clinically relevant quantities of cells. Finally, we summarise the main regulatory pathways for these clinical products, which can help shape early therapeutic design and testing.

Microchip with Single-Cell Impedance Measurements for Monitoring Osteogenic Differentiation of Mesenchymal Stem Cells under Electrical Stimulation

Effective induction methods and in situ monitoring are essential for studying the mechanism of biological responses in stem cell differentiation. This article proposes an induction method incorporating electrical stimulation under an inhomogeneous field with single-cell impedance monitoring for studying osteogenic differentiation of mesenchymal stem cells (MSCs) using a microchip. The microchip contains an array of sextupole-electrode units for implementing a combination of controllable electrical stimulation and single-cell impedance measurements. MSCs are inducted to osteogenic differentiation under electrical stimulation using quadrupole electrodes and single-cell impedances are monitored in situ using a pair of microelectrodes at each unit center. The proposed microchip adopts an array design to monitor a number of MSCs in parallel, which improves measurement throughput and facilitates to carry out statistic tests. We perform osteogenic differentiation of MSCs on the microchip with and without electrical stimulation meanwhile monitoring single-cell impedance in real time for 21 days. The recorded impedance results show the detailed characteristic change of MSCs at the single-cell level during osteogenic differentiation, which demonstrates a significant difference between the conditions with and without electrical stimulation. The cell morphology and various staining analyses are also used to validate osteogenesis and correlate with the impedance expression. Correlation analysis of the impedance measurement, cell morphology, and various staining assays proves the great acceleration effect of the proposed electrical stimulation on osteogenic differentiation of MSCs. The proposed impedance method can monitor the dynamic process of cell development and study heterogeneity of stem cell differentiation at the single-cell level.

Analysis of Time to Form Colony Units for Connective Tissue Progenitor Cells (Stem Cells) Harvested From Concentrated Bone Marrow Aspirate and Subacromial Bursa Tissue in Patients Undergoing Rotator Cuff Repair

Purpose

To evaluate the time required for colonies to develop from concentrated bone marrow aspirate (cBMA) and subacromial bursal tissue samples.

Methods

Samples of cBMA and subacromial bursa tissue were harvested from patients undergoing rotator cuff repair surgery between November 2014 and December 2019. Samples were analyzed for time to form colonies and number of colonies formed. The impact of age, sex, and cellularity (cBMA only) was analyzed. Samples were cultured and evaluated daily for colony formation in accordance with the guidelines of the International Society for Cellular Therapy. Demographic factors were analyzed for impact on time to form colonies and number of colonies formed.

Results

Samples of cBMA were obtained from 92 patients. Subacromial bursa tissue was obtained from 54 patients. For cBMA, older age was associated with more days to form colonies (P = .003), but sex (P = .955) and cellularity (P = .623) were not. For bursa, increased age was associated with longer time to form colonies (P = .002) but not sex (P = .804). Conclusions: Increased age (in cBMA and subacromial bursa tissue) and lower initial cellularity (in cBMA) are associated with longer time to form colonies in culture.

Clinical Relevance

Although connective tissue progenitor cells are widely used in orthopaedic practice, there are few metrics to determine their efficacy. Time to form colonies may serve as an important measurement for determining connective tissue progenitor cell viability for augmentation of rotator cuff repair. Subacromial bursa tissue may represent a viable alternative to cBMA for augmentation of rotator cuff repair, capable of forming colonies expediently in vivo.

Placental scaffolds have the ability to support adipose-derived cells differentiation into osteogenic and chondrogenic lineages

Prudent choices of cell sources and biomaterials, as well as meticulous cultivation of the tissue microenvironment, are essential to improving outcomes of tissue engineering treatments. With the goal of providing a high-quality alternative for bone and cartilage tissue engineering, we investigated the capability of bovine placental scaffolds to support adipose-derived cell differentiation into osteogenic and chondrogenic lineages. Decellularized bovine placenta, a high-quality scaffold with practical scalability, was chosen as the biomaterial due to its rich extracellular matrix, well-developed vasculature, high availability, low cost, and simplicity of collection. Adipose-derived cells were chosen as the cell source as they are easy to isolate, nontumorigenic, and flexibly differentiable. The bovine model was chosen for its advantages in translational medicine over the mouse model. When seeded onto the scaffolds, the isolated cells adhered to the scaffolds with cell projections, established cell-scaffold communication and proliferated while maintaining cell-cell communication. Throughout a 21-day culture period, osteogenically differentiated cells secreted mineralized matrix, and calcium deposits were observed throughout the scaffold. Under chondrogenic specific differentiation conditions, the cells modified their morphology from fibroblast-like to round cells and cartilage lacunas were observed as well as the deposit of cartilaginous matrix on the placental scaffolds. This experiment provides evidence, for the first time, that bovine placental scaffolds have the potential to support bovine mesenchymal stem cell adherence and differentiation into osteogenic and chondrogenic lineages. Therefore, the constructed material could be used for bone and cartilage tissue engineering.

In utero treatment of myelomeningocele with placental mesenchymal stromal cells - Selection of an optimal cell line in preparation for clinical trials

BACKGROUND

We determined whether in vitro potency assays inform which placental mesenchymal stromal cell (PMSC) lines produce high rates of ambulation following in utero treatment of myelomeningocele in an ovine model.

METHODS

PMSC lines were created following explant culture of three early-gestation human placentas. In vitro neuroprotection was assessed with a neuronal apoptosis model. In vivo, myelomeningocele defects were created in 28 fetuses and repaired with PMSCs at 3 × 10⁵ cells/cm² of scaffold from Line A (n = 6), Line B (n = 7) and Line C (n = 5) and compared to no PMSCs (n = 10). Ambulation was scored as ≥13 on the Sheep Locomotor Rating Scale.

RESULTS

In vitro, Line A and B had higher neuroprotective capability than no PMSCs (1.7 and 1.8 respectively vs 1, p = 0.02, ANOVA). In vivo, Line A and B had higher large neuron densities than no PMSCs (25.2 and 27.9 respectively vs 4.8, p = 0.03, ANOVA). Line C did not have higher neuroprotection or larger neuron density than no PMSCs. In vivo, Line A and B had ambulation rates of 83% and 71%, respectively, compared to 60% with Line C and 20% with no PMSCs.

CONCLUSION

The in vitro neuroprotection assay will facilitate selection of optimal PMSC lines for clinical use.

LEVEL OF EVIDENCE

n/a.

TYPE OF STUDY

Basic science.

The COVID-19: Current understanding

In December 2019, China reported several cases of a new coronavirus disease (COVID-19). The COVID-19 outbreak, which was initially limited to Wuhan, China, has rapidly spread worldwide. Infection of the disease occurs through exposure to the virus through inhalation of respiratory droplets or if a person touches a mucosal surface after touching an object with the virus on it. The common symptoms of COVID-19 are fever, dry cough, dyspnea (difficult or labored breathing), fatigue, chest pain, and myalgia (muscle pain), etc. Real-time polymerase chain reaction is used to detect the virus in sputum, throat, nasal swabs, and secretion of lower respiratory samples. Early diagnosis, isolation, and supportive care are necessary for the treatment of the patients. The present review aims to provide recent information on COVID-19 related to its epidemiology, clinical symptoms, and management. This article also summarizes the current understanding of severe acute respiratory syndrome coronavirus-2 and its history of origin.

Anti-Fibrotic Effect of Human Wharton's Jelly-Derived Mesenchymal Stem Cells on Skeletal Muscle Cells, Mediated by Secretion of MMP-1

Extracellular matrix (ECM) components play an important role in maintaining skeletal muscle function, but excessive accumulation of ECM components interferes with skeletal muscle regeneration after injury, eventually inducing fibrosis. Increased oxidative stress level caused by dystrophin deficiency is a key factor in fibrosis in Duchenne muscular dystrophy (DMD) patients. Mesenchymal stem cells (MSCs) are considered a promising therapeutic agent for various diseases involving fibrosis. In particular, the paracrine factors secreted by MSCs play an important role in the therapeutic effects of MSCs. In this study, we investigated the effects of MSCs on skeletal muscle fibrosis. In 2–5-month-old mdx mice intravenously injected with 1 × 10⁵ Wharton’s jelly (WJ)-derived MSCs (WJ-MSCs), fibrosis intensity and accumulation of calcium/necrotic fibers were significantly decreased. To elucidate the mechanism of this effect, we verified the effect of WJ-MSCs in a hydrogen peroxide-induced fibrosis myotubes model. In addition, we demonstrated that matrix metalloproteinase-1 (MMP-1), a paracrine factor, is critical for this anti-fibrotic effect of WJ-MSCs. These findings demonstrate that WJ-MSCs exert anti-fibrotic effects against skeletal muscle fibrosis, primarily via MMP-1, indicating a novel target for the treatment of muscle diseases, such as DMD.

Cell culture media notably influence properties of human mesenchymal stroma/stem-like cells from different tissues

BACKGROUND AIMS

Mesenchymal stroma/stem-like cells (MSCs) are a popular cell source and hold huge therapeutic promise for a broad range of possible clinical applications. However, to harness their full potential, current limitations in harvesting, expansion and characterization have to be overcome. These limitations are related to the heterogeneity of MSCs in general as well as to inconsistent experimental protocols. Here we aim to compare in vitro methods to facilitate comparison of MSCs generated from various tissues.

METHODS

MSCs from 3 different tissues (bone marrow, dental pulp, adipose tissue), exemplified by cells from 3 randomly chosen donors per tissue, were systematically compared with respect to their in vitro properties after propagation in specific in-house standard media, as established in the individual laboratories, or in the same commercially available medium.

RESULTS

Large differences were documented with respect to the expression of cell surface antigens, population doubling times, basal expression levels of 5 selected genes and osteogenic differentiation. The commercial medium reduced differences in these parameters with respect to individual human donors within tissue and between tissues. The extent, size and tetraspanin composition of extracellular vesicles were also affected.

CONCLUSIONS

The results clearly demonstrate the extreme heterogeneity of MSCs, which confirms the problem of reproducibility of results, even when harmonizing experimental conditions, and questions the significance of common parameters for MSCs from different tissues in vitro.

Intrauterine transplantation of autologous menstrual blood stem cells increases endometrial thickness and pregnancy potential in patients with refractory intrauterine adhesion

AIM

This study was designed to evaluate the effects of intrauterine transplantation of menstrual blood stem cells (MenSCs) on endometrial thickness and pregnancy outcomes in patients with refractory intrauterine adhesion (IUA).

METHODS

This study included a group of infertile women (n = 12, age 22-40 years), with refractory IUA. Autologous MenSCs isolated from the women's menstrual blood were expanded in vitro and transplanted into their uteruses, followed by hormone replacement therapy. Transvaginal ultrasound examination was performed to assess the endometrial thickness. Transabdominal ultrasound was conducted to detect pregnancy outcome.

RESULTS

Autologous MenSCs were successfully isolated and expanded from menstrual blood and transplanted into the uterus of each patient. A significant improvement of the endometrial thickness was observed from 3.9 ± 0.9 to 7.5 ± 0.6 mm (P < 0.001). No adverse reaction was observed. The duration of menstruation was increased from 2.4 ± 0.7 to 5.3 ± 0.6 days (P < 0.001). Five out of 12 patients achieved clinical pregnancy and the pregnancy rate was 41.7%.

CONCLUSIONS

Intrauterine transplantation of autologous MenSCs results in regeneration of endometrium, a prolongation of menstrual duration and an increase rate of pregnancy in patients with refractory IUA.

Trimodal Cell Tracking In Vivo: Combining Iron- and Fluorine-Based Magnetic Resonance Imaging with Magnetic Particle Imaging to Monitor the Delivery of Mesenchymal Stem Cells and the Ensuing Inflammation

The therapeutic potential of mesenchymal stem cells (MSCs) is limited, as many cells undergo apoptosis following administration. In addition, the attraction of immune cells (predominately macrophages) to the site of implantation can lead to MSC rejection. We implemented a trimodal imaging technique to monitor the fate of transplanted MSCs and infiltrating macrophages in vivo. MSCs were labeled with an iron oxide nanoparticle (ferumoxytol) and then implanted within the hind limb muscle of 10 C57BI/6 mice. Controls received unlabeled MSCs (n = 5). A perfluorocarbon agent was administered intravenously for uptake by phagocytic macrophages in situ; 1 and 12 days later, the ferumoxytol-labeled MSCs were detected by proton (¹H) magnetic resonance imaging (MRI) and magnetic particle imaging (MPI). Perfluorocarbon-labeled macrophages were detected by fluorine-19 (¹⁹F) MRI. ¹H/¹⁹F MRI was acquired on a clinical scanner (3 T) using a dual-tuned surface coil and balanced steady-state free precession (bSSFP) sequence. The measured volume of signal loss and MPI signal declined over 12 days, which is consistent with the death and clearance of iron-labeled MSCs. ¹⁹F signal persisted over 12 days, suggesting the continuous infiltration of perfluorocarbon-labeled macrophages. Because MPI and ¹⁹F MRI signals are directly quantitative, we calculated estimates of the number of MSCs and macrophages present over time. The presence of MSCs and macrophages was validated with histology following the last imaging session. This is the first study to combine the use of iron- and fluorine-based MRI with MPI cell tracking.

Mesenchymal Stem Cell-Derived Extracellular Vesicles and Their Therapeutic Potential

Extracellular vesicles (EVs) are cell-derived membrane-bound nanoparticles, which act as shuttles, delivering a range of biomolecules to diverse target cells. They play an important role in maintenance of biophysiological homeostasis and cellular, physiological, and pathological processes. EVs have significant diagnostic and therapeutic potentials and have been studied both in vitro and in vivo in many fields. Mesenchymal stem cells (MSCs) are multipotent cells with many therapeutic applications and have also gained much attention as prolific producers of EVs. MSC-derived EVs are being explored as a therapeutic alternative to MSCs since they may have similar therapeutic effects but are cell-free. They have applications in regenerative medicine and tissue engineering and, most importantly, confer several advantages over cells such as lower immunogenicity, capacity to cross biological barriers, and less safety concerns. In this review, we introduce the biogenesis of EVs, including exosomes and microvesicles. We then turn more specifically to investigations of MSC-derived EVs. We highlight the great therapeutic potential of MSC-derived EVs and applications in regenerative medicine and tissue engineering.

Clinical study using mesenchymal stem cells for the treatment of patients with severe COVID-19

The Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 was identified in December 2019. The symptoms include fever, cough, dyspnea, early symptom of sputum, and acute respiratory distress syndrome (ARDS). Mesenchymal stem cell (MSC) therapy is the immediate treatment used for patients with severe cases of COVID-19. Herein, we describe two confirmed cases of COVID-19 in Wuhan to explore the role of MSC in the treatment of COVID-19. MSC transplantation increases the immune indicators (including CD4 and lymphocytes) and decreases the inflammation indicators (interleukin-6 and C-reactive protein). High-flow nasal cannula can be used as an initial support strategy for patients with ARDS. With MSC transplantation, the fraction of inspired O₂ (FiO₂) of the two patients gradually decreased while the oxygen saturation (SaO₂) and partial pressure of oxygen (PO₂) improved. Additionally, the patients’ chest computed tomography showed that bilateral lung exudate lesions were adsorbed after MSC infusion. Results indicated that MSC transplantation provides clinical data on the treatment of COVID-19 and may serve as an alternative method for treating COVID-19, particularly in patients with ARDS.

Differentiation Potential of Synovial Mesenchymal Stem Cells Isolated From Hip Joints Affected by Femoroacetabular Impingement Syndrome Versus Osteoarthritis

PURPOSE

To establish the characteristics of synovium-derived mesenchymal stem cells (MSCs) from the hip joints of patients with femoroacetabular impingement syndrome (FAIS) and osteoarthritis (OA), particularly their proliferation and differentiation potentials. We further investigated their functional differences.

METHODS

Synovium samples were harvested from 21 patients with FAIS who underwent hip arthroscopic surgery and from 14 patients with OA who underwent total hip arthroplasty. The MSC number, colony-forming units, cell viability, and differentiation potential were compared. Real-time polymerase chain reaction assessed the differentiation potential into adipose, bone, and cartilage tissues.

RESULTS

The number of colonies at a density of 10⁴ at passage 0 from OA synovium was significantly greater than that from FAIS synovium (P < .01). However, their proliferation and viability were significantly lower than those of FAIS synovium cells (P = .0495). The expression of lipoprotein lipase mRNA in OA synovium cells was greater than that in FAIS synovium cells (P < .01). Meanwhile, the fraction of colonies positive for von Kossa and alkaline phosphatase staining, as well as the level of bone gamma-carboxyglutamate protein expression in OA synovium cells, were greater than those in FAIS synovium cells (P < .01). In chondrogenic pellet culture experiments, the expression of COL10A1 mRNA was lower in OA synovium than in FAIS synovium (P < .01).

CONCLUSIONS

Synovial MSCs from patients with OA had greater colony numbers but less viability and proliferative potential. They also showed greater osteogenic and adipogenic potentials, whereas those from patients with FAIS showed greater chondrogenic potential.

CLINICAL RELEVANCE

MSCs from patients with FAIS exhibited good potential as cell sources for stem cell therapy in case of cartilage damage in the hip joint.

Adipose Tissue-Derived Stem Cells from Type 2 Diabetics Reveal Conservative Alterations in Multidimensional Characteristics

Background and Objectives

Adipose tissue-derived mesenchymal stem cells (ASCs) are recognized as an advantaged source for the prevention and treatment of diverse diseases including type 2 diabetes mellitus (T2DM). However, alterations in characteristics of ASCs from the aforementioned T2DM patients are still obscure, which also hinder the rigorous and systematic illumination of progression and pathogenesis.

Methods and Results

In this study, we originally isolated peripancreatic adipose tissue-derived mesenchymal stem cells from both human type 2 diabetic and non-diabetic donors (T2DM-ASCs, ND-ASCs) with the parental consent, respectively. We noticed that T2DM-ASCs exhibited indistinguishable immunophenotype, cell vitality, chondrogenic differentiation and stemness as ND-ASCs. Simultaneously, there’s merely alterations in migration and immunoregulatory capacities in T2DM-ASCs. However, differing from ND-ASCs, T2DM-ASCs exhibited deficiency in adipogenic and osteogenic differentiation, and in particular, the delayed cell cycle and different cytokine expression spectrum.

Conclusions

The conservative alterations of T2DM-ASCs in multifaceted characteristics indicated the possibility of autologous application of ASCs for cell-based T2DM treatment in the future.

Functional heterogeneity of mesenchymal stem cells from natural niches to culture conditions: implications for further clinical uses

Mesenchymal stem cells (MSC) are present in all organs and tissues. Several studies have shown the therapeutic potential effect of MSC or their derived products. However, the functional heterogeneity of MSC constitutes an important barrier for transferring these capabilities to the clinic. MSC heterogeneity depends on their origin (biological niche) or the conditions of potential donors (age, diseases or unknown factors). It is accepted that many culture conditions of the artificial niche to which they are subjected, such as O₂ tension, substrate and extracellular matrix cues, inflammatory stimuli or genetic manipulations can influence their resulting phenotype. Therefore, to attain a more personalized and precise medicine, a correct selection of MSC is mandatory, based on their functional potential, as well as the need to integrate all the existing information to achieve an optimal improvement of MSC features in the artificial niche.

Antimicrobial activity of mesenchymal stem cells against Staphylococcus aureus

Introduction

There have been limited advances in the treatment of bone and joint infections, which currently involves a combination of surgery and antibiotic administration. There is a timely need in orthopedics to develop more effective and less invasive forms of antimicrobial prophylaxis and treatment. The antibacterial effect of adult tissue-derived mesenchymal stem cells (MSCs) has recently been investigated against Escherichia coli and Staphylococcus aureus. The main mechanism of action is postulated to be via MSC production of the cationic antimicrobial peptide, LL-37.

Methods

This study examines the antimicrobial activity of adipose-derived human MSCs (ASCs) on S. aureus, specifically examining the role of LL-37 and regulation of its expression. Bacteria colony-forming unit (CFU) assay was used to assess antimicrobial activity.

Results

Our results showed that the ASC-conditioned medium significantly inhibited the growth of S. aureus under standard culture conditions with or without the continued presence of ASCs. Also, the treatment of ASCs with 1,25-dihydroxy vitamin D₃ elevated LL-37 expression and enhanced their antimicrobial activity. In support, treatment with the vitamin D receptor inhibitor, GW0742, blocked the antimicrobial activity of ASCs.

Conclusion

Our findings clearly demonstrate the antimicrobial activity of adult ASCs against S. aureus and implicate a key regulatory role for vitamin D. Further testing in in vivo models is being pursued to assess the potential application of ASCs as a biocompatible, adjunct treatment for musculoskeletal infections.

The Coronavirus Pandemic (SARS-CoV-2): New Problems Demand New Solutions, the Alternative of Mesenchymal (Stem) Stromal Cells

Mesenchymal (stem) stromal cells (MSC) can be a therapeutic alternative for COVID-19 considering their anti-inflammatory, regenerative, angiogenic, and even antimicrobial capacity. Preliminary data point to therapeutic interest of MSC for patients with COVID-19, and their effect seems based on the MSC's ability to curb the cytokine storm caused by COVID-19. In fact, promising clinical studies using MSC to treat COVID-19, are currently underway. For this reason, now is the time to firmly consider new approaches to MSC research that addresses key issues, like selecting the most optimal type of MSC for each indication, assuming the heterogeneity of the donor-dependent MSC and the biological niche where MSC are located.

The omentum harbors unique conditions in the peritoneal cavity to promote healing and regeneration for diaphragm muscle repair in mdx mice

Although the primary cause of Duchenne muscular dystrophy (DMD) is a genetic mutation, the inflammatory response contributes directly to severity and exacerbation of the diaphragm muscle pathology. The omentum is a lymphoid organ with unique structural and immune functions serving as a sanctuary of hematopoietic and mesenchymal progenitors that coordinate immune responses in the peritoneal cavity. Upon activation, these progenitors expand and the organ produces large amounts of growth factors orchestrating tissue regeneration. The omentum of mdx mouse, a DMD murine model, is rich in milky spots and produces growth factors that promote diaphragm muscle regeneration. The present review summarizes the current knowledge of the omentum as an important immunologic structure and highlights its contribution to resolution of dystrophic muscle injury by providing an adequate environment for muscle regeneration, thus being a potential site for therapeutic interventions in DMD.

Adipogenesis, Osteogenesis, and Chondrogenesis of Human Mesenchymal Stem/Stromal Cells: A Comparative Transcriptome Approach

Adipogenesis, osteogenesis and chondrogenesis of human mesenchymal stem/stromal cells (MSC) are complex and highly regulated processes. Over the years, several studies have focused on understanding the mechanisms involved in the MSC commitment to the osteogenic, adipogenic and/or chondrogenic phenotypes. High-throughput methodologies have been used to investigate the gene expression profile during differentiation. Association of data analysis of mRNAs, microRNAs, circular RNAs and long non-coding RNAs, obtained at different time points over these processes, are important to depict the complexity of differentiation. This review will discuss the results that were highlighted in transcriptome analyses of MSC undergoing adipogenic, osteogenic and chondrogenic differentiation. The focus is to shed light on key molecules, main signaling pathways and biological processes related to different time points of adipogenesis, osteogenesis and chondrogenesis.

Improved harmonization of critical characterization assays across cell therapies

The field of cell therapy has blossomed, providing exciting new options for treating a variety of diseases. While few cell therapy products have US FDA approval, there are thousands of cell treatments at various stages of development, pointing to a potential revolutionary shift in patient care. The expanding number and nature of cellular therapies necessitate greater standardization. Several international organizations are collaborating to pursue some level of global standardization, especially concerning cell banking. However, less harmonization surrounds assays used for critical quality characterization including: identity, purity, safety and potency. Frequently, there is divergence regarding the terms describing the characterization assays across regulatory authorities and guidances. This review summarizes the critical quality assays currently used for different categories of cell therapies. Areas of harmonization and an absence of standardization are highlighted. We propose potential solutions to facilitate harmonization of critical quality characterization assays and the language used to describe them.

Recent trends in stem cell therapy for premature ovarian insufficiency and its therapeutic potential: a review

Stem cell therapy is attracting attention in the field of regenerative medicine and is advancing rapidly. Many recent studies have applied stem cell therapy to treat reproductive system diseases; however, data are not yet available as to whether this therapy shows enhanced therapeutic effects. This paper analyzes recent preclinical studies on stem cell therapy for ovarian dysfunction in several types of animal models. Several clinical trials and pending projects are also discussed. This review will provide a background for developing stem cell therapies to enhance ovarian function.

Induction of ASC pyroptosis requires gasdermin D or caspase-1/11-dependent mediators and IFNβ from pyroptotic macrophages

Mesenchymal stem cells (MSCs) have been used in cell-based therapies for a variety of disorders. Some factors such as inflammatory mediators in the diseased area might damage the survival of MSCs and affect their efficacy. Pyroptosis is a form of programmed necrosis as a response for immune cells to cytosolic pathogenic stimuli. Whether MSCs develop pyroptosis under pathological stimulation, its underlying mechanism and biological significance are still unclear. Here, we found that LPS, flagellin, dsDNA, nigericin (NIG), or LPS combined with nigericin (LPS/NIG) could not induce pyroptosis in adipose-tissue-derived mesenchymal stem cells (ASCs). However, when applied the culture media collected from LPS/NIG-induced pyroptotic bone marrow-derived macrophages (BMDMs) to incubate ASCs, ASCs developed pyroptosis. Inhibition of caspases or deletion of Caspase-1/11 in ASCs did not affect the pyroptotic macrophage media-triggered ASC pyroptosis while ablation of Caspase-1/11 abolished BMDM pyroptosis induced by LPS/NIG. Media collected from LPS/NIG stimulated Gsdmd^−/− or Caspase-1/11^−/− BMDMs could not induce pyroptosis of ASCs. In addition, RNA-seq analysis showed that interferon (IFN)-stimulated genes were upregulated in pyroptotic ASCs. Adding IFNβ could boost LPS/NIG stimulated BMDM media-induced ASC pyroptosis. Surprisingly, the pyroptotic ASCs had a lower bactericidal ability to P. Aeruginosa. Taken together, induction of ASC pyroptosis requires gasdermin D or caspase-1/11-dependent mediators and IFNβ from pyroptotic macrophages.

Immortalizing Mesenchymal Stromal Cells from Aged Donors While Keeping Their Essential Features

Human bone marrow-derived mesenchymal stromal cells (MSCs) obtained from aged patients are prone to senesce and diminish their differentiation potential, therefore limiting their usefulness for osteochondral regenerative medicine approaches or to study age-related diseases, such as osteoarthiritis (OA). MSCs can be transduced with immortalizing genes to overcome this limitation, but transduction of primary slow-dividing cells has proven to be challenging. Methods for enhancing transduction efficiency (such as spinoculation, chemical adjuvants, or transgene expression inductors) can be used, but several parameters must be adapted for each transduction system. In order to develop a transduction method suitable for the immortalization of MSCs from aged donors, we used a spinoculation method. Incubation parameters of packaging cells, speed and time of centrifugation, and valproic acid concentration to induce transgene expression have been adjusted. In this way, four immortalized MSC lines (iMSC#6, iMSC#8, iMSC#9, and iMSC#10) were generated. These immortalized MSCs (iMSCs) were capable of bypassing senescence and proliferating at a higher rate than primary MSCs. Characterization of iMSCs showed that these cells kept the expression of mesenchymal surface markers and were able to differentiate towards osteoblasts, adipocytes, and chondrocytes. Nevertheless, alterations in the CD105 expression and a switch of cell fate-commitment towards the osteogenic lineage have been noticed. In conclusion, the developed transduction method is suitable for the immortalization of MSCs derived from aged donors. The generated iMSC lines maintain essential mesenchymal features and are expected to be useful tools for the bone and cartilage regenerative medicine research.

Cox2-mediated PGE2 production via p38/JNK-c-fos signaling inhibits cell apoptosis in 3D floating culture clumps of mesenchymal stem cell/extracellular matrix complexes

Mesenchymal stem cells (MSCs), a class of adult stem cells, have attracted scientific and medical attention due to their self-renewing properties, multipotency, and trophic factor production. Although MSCs were originally studied on classical two-dimensional (2D) plastic plates, extensive scientific efforts have developed three-dimensional (3D) MSC culture systems, including MSCs spheroids and organoids that can mimic physical conditions. Moreover, we have recently developed 3D culture clumps of MSCs/extracellular matrix (ECM) complexes (C-MSCs) for novel bone regenerative cell therapy. Of note, even though it is widely accepted that cell detachment from the culture plate causes cell apoptosis, so called anoikis, these 3D MSCs constructs can be maintained in floating culture conditions. Currently, it is unclear why 3D floating-cultured MSCs constructs can escape from anoikis. To answer this question, the present study explored trophic factor production in 3D floating-cultured C-MSCs that play a cytoprotective role against anoikis and clarified the underlying molecular mechanism in vitro. Compared with cells cultured on 2D plastic plates, PGE2 production mediated by COX2 was significantly increased, and its inhibition drastically induced cell apoptosis in 3D floating-cultured C-MSCs. In the process of C-MSCs preparation, detachment of the cell sheet from culture plate activated the p38/JNK-c-Fos signaling pathway. Moreover, blockage of this signaling by chemical inhibitors abrogated COX2/PGE2 expressions and induced severe apoptosis. These results demonstrated that cell detachment facilitates cytoprotective COX2-mediated PGE2 synthesis via p38/JNK-c-Fos signaling, revealing a possible mechanism that allows resistance against anoikis in floating-cultured 3D MSCs constructs.

Mesenchymal stem cells for the treatment of psoriasis: a comprehensive review

Mesenchymal stem cells (MSCs) have recently been shown to have not only regenerative capabilities but also immunomodulating properties. For this reason, they are currently under investigation in clinical trials for the treatment of several autoimmune systemic disorders. Psoriasis is a systemic immune-mediated disease for which MSCs could have therapeutic potential. We analysed the existing literature with regard to MSC-based strategies for the treatment of psoriasis, using the MEDLINE, Embase, Scopus and Cochrane Library electronic databases from inception to the date of study. A number of studies confirm the involvement of MSCs in psoriasis pathogenesis and therefore designate MSCs as an important potential therapeutic tool in this setting. Preclinical data are mostly based on imiquimod-induced murine models of psoriasis, and confirm the anti-inflammatory and immunomodulatory action of MSCs in the setting of psoriasis. Six patients affected by psoriasis were described in four clinical studies. Despite significant differences in terms of therapeutic protocols and clinical outcomes, the MSC-based regimens were efficacious in 100% of the cases. Despite more data still being needed, MSCs could be a promising therapy for psoriasis.

Use of Stem Cell Extracellular Vesicles as a "Holistic" Approach to CNS Repair

Neurodegeneration is a hallmark of many diseases and disorders of the central nervous system (CNS). High levels of neuroinflammation are often associated with irreparable damage to CNS cells due to the dysregulation of signaling cascades that are unable to restore a homeostatic balance. Due to the inherent complexity of the CNS, development of CNS-related therapeutics has met limited success. While stem cell therapy has been evaluated in the context of CNS repair, the mechanisms responsible for their functional properties have not been clearly defined. In recent years, there has been growing interest in the use of stem cell extracellular vesicles (EVs) for the treatment of various CNS pathologies as these vesicles are believed to mediate many of the functional effects associated with their donor stem cells. The potency of stem cell EVs is believed to be largely driven by their biological cargo which includes various types of RNAs, proteins, and cytokines. In this review, we describe the characteristic properties of stem cell EVs and summarize their reported neuroprotective and immunomodulatory functions. A special emphasis is placed on the identification of specific biological cargo, including proteins and non-coding RNA molecules, that have been found to be associated with stem cell EVs. Collectively, this review highlights the potential of stem cell EVs as an alternative to traditional stem cell therapy for the repair of cellular damage associated with diverse CNS pathologies.

Bone marrow mesenchymal stem cell-derived endothelial cells increase capillary density and accelerate angiogenesis in mouse hindlimb ischemia model

Background

Mesenchymal stem cells (MSCs) can improve limb perfusion and increase vessel density in a murine model of hindlimb ischemia. But low engraftment rate of those cells limited their therapeutic effect. Endothelial cells (ECs) play an important role in neovascularization. And MSCs can differentiate into ECs in vitro. The aim of this study is to investigate if EC differentiation of MSCs in vitro before transplantation is effective in improving therapeutic outcomes in the treatment of ischemic disease in a murine ischemia animal model.

Methods

MSCs were isolated from the bone marrow of EGFP-transgenic mice by density gradient centrifugation. The identity of the MSCs was determined by their cluster of differentiation (CD) marker profile by flow cytometry. Inducing medium containing a few cytokines was applied to induce the MSCs to differentiate into ECs. Endothelial differentiation was quantitatively evaluated using flow cytometry, quantitative real-time PCR (qRT-PCR), immunofluorescence, Matrigel tube formation assay, and Dil-labeled acetylated low-density lipoprotein uptake assay. Mouse hindlimb ischemia model was made by excision of the femoral artery. Uninduced EGFP+ MSCs, induced EGFP+ MSCs, and PBS were intramuscularly injected into the gastrocnemius following ischemia no later than 24 h after operation. Restoration of blood flow and muscle function was evaluated by laser Doppler perfusion imaging. Immunofluorescence was conducted to evaluate the engraftment of transplanted MSCs. Histological analysis was performed to evaluate blood vessel formation.

Results

Induced EGFP+ MSCs expressed endothelial markers and exhibited tube formation capacity. Mice in the induced EGFP+ MSCs group had a better blood perfusion recovery, enhanced vessel densities, higher engraftment, and improved function of the ischemic limb than those in the uninduced EGFP+ MSCs or PBS groups.

Conclusions

This study reveals that after short-term pre-treatment in the EC-inducing medium, induced MSCs acquire stronger vessel formation capability and enhanced angiogenic therapeutic effect in the murine hindlimb ischemia model.

Skeletal Stem Cells for Bone Development and Repair: Diversity Matters

PURPOSE OF REVIEW

Skeletal stem cells (SSCs) are considered to play important roles in bone development and repair. These cells have been historically defined by their in vitro potential for self-renewal and differentiation into "trilineage" cells; however, little is known about their in vivo identity. Here, we discuss recent progress on SSCs and how they potentially contribute to bone development and repair.

RECENT FINDINGS

Bone is composed of diverse tissues, which include cartilage and its perichondrium, cortical bone and its periosteum, and bone marrow and its trabecular bone and stromal compartment. We are now at the initial stage of understanding the precise identity of SSCs in each bone tissue. The emerging concept is that functionally dedicated SSCs are encased by their own unique cellular and extracellular matrix microenvironment, and locally support its own compartment. Diverse groups of SSCs are likely to work in concert to achieve development and repair of the highly functional skeletal organ.

Mesenchymal stromal cell and bone marrow concentrate therapies for musculoskeletal indications: a concise review of current literature

The interest on applying mesenchymal stromal cells (MSCs) in orthopedic disorders has risen tremendously in the last years due to scientific successes in preclinical in vitro and animal model studies. In a wide range of diseases and injuries of the musculoskeletal system, MSCs are currently under evaluation, but so far have found access to clinical use only in few cases. The current assignment is to translate the acquired knowledge into clinical practice. Therefore, this review aims at presenting a synopsis of the up-to-date status of the use of MSCs and MSC related cell products in musculoskeletal indications. Clinical studies were included, whereas preclinical and animal study data not have been considered. Most studies published so far investigate the final outcome applying bone marrow derived MSCs. In fewer trials the use of adipose tissue derived MSCs and allogenic MSCs was investigated in different applications. Although the reported results are equivocal in the current literature, the vast majority of the studies shows a benefit of MSC based therapies depending on the cell sources and the indication in clinical use. In summary, the clinical use of MSCs in patients in orthopedic indications has been found to be safe. Standardized protocols and clear definitions of the mechanisms of action and the mode and timing of application as well as further coordinated research efforts will be necessary for finally adding MSC based therapies in standard operating procedures and guidelines for the clinicians treating orthopedic disorders.