Sarcoma derived from cultured mesenchymal stem cells

Revisiting the role of mesenchymal stromal cells in cancer initiation, metastasis and immunosuppression

Immune checkpoint blockade (ICB) necessitates a thorough understanding of intricate cellular interactions within the tumor microenvironment (TME). Mesenchymal stromal cells (MSCs) play a pivotal role in cancer generation, progression, and immunosuppressive tumor microenvironment. Within the TME, MSCs encompass both resident and circulating counterparts that dynamically communicate and actively participate in TME immunosurveillance and response to ICB. This review aims to reevaluate various facets of MSCs, including their potential self-transformation to function as cancer-initiating cells and contributions to the creation of a conducive environment for tumor proliferation and metastasis. Additionally, we explore the immune regulatory functions of tumor-associated MSCs (TA-MSCs) and MSC-derived extracellular vesicles (MSC-EVs) with analysis of potential connections between circulating and tissue-resident MSCs. A comprehensive understanding of the dynamics of MSC-immune cell communication and the heterogeneous cargo of tumor-educated versus naïve MSCs may unveil a new MSC-mediated immunosuppressive pathway that can be targeted to enhance cancer control by ICB.

Recent advances in mesenchymal stem cell therapy for myocardial infarction

Myocardial infarction refers to the ischemic necrosis of myocardium, characterized by a sharp reduction or interruption of blood flow in the coronary arteries due to the coronary artery occlusion, resulting in severe and prolonged ischemia in the corresponding myocardium and ultimately leading to ischemic necrosis of the myocardium. Given its high risk, it is considered as one of the most serious health threats today. In current clinical practice, multiple approaches have been explored to diminish myocardial oxygen consumption and alleviate symptoms, but notable success remains elusive. Accumulated clinical evidence has showed that the implantation of mesenchymal stem cell for treating myocardial infarction is both effective and safe. Nevertheless, there persists controversy and variability regarding the standardizing MSC transplantation protocols, optimizing dosage, and determining the most effective routes of administration. Addressing these remaining issues will pave the way of integration of MSCs as a feasible mainstream cardiac treatment.

Function of GSK‑3 signaling in spinal cord injury (Review)

Spinal cord injury (SCI) is a major social problem with a heavy burden on patient physiology and psychology. Glial scar formation and irreversible neuron loss are the two key points during SCI progression. During the acute phase of spinal cord injury, glial scars form, limiting the progression of inflammation. However, in the subacute or chronic phase, glial scarring inhibits axon regeneration. Following spinal cord injury, irreversible loss of neurons leads to further aggravation of spinal cord injury. Several therapies have been developed to improve either glial scar or neuron loss; however, few therapies reach the stage of clinical trials and there are no mainstream therapies for SCI. Exploring the key mechanism of SCI is crucial for finding further treatments. Glycogen synthase kinase-3 (GSK-3) is a widely expressed kinase with important physiological and pathophysiological functions in vivo. Dysfunction of the GSK-3 signaling pathway during SCI has been widely discussed for controlling neurite growth in vitro and in vivo, improving the proliferation and neuronal differentiation of endogenous neural stem cells and functional recovery from spinal cord injury. SCI can decrease the phosphorylated (p)/total (t)-GSK-3β ratio, which leads to an increase in apoptosis, whereas treatment with GSK-3 inhibitors can promote neurogenesis. In addition, several therapies for the treatment of SCI involve signaling pathways associated with GSK-3. Furthermore, signaling pathways associated with GSK-3 also participate in the pathological process of neuropathic pain that remains following SCI. The present review summarized the roles of GSK-3 signaling in SCI to aid in the understanding of GSK-3 signaling during the pathological processes of SCI and to provide evidence for the development of comprehensive treatments.

Progress in Research on Stem Cells in Neonatal Refractory Diseases

With the development and progress of medical technology, the survival rate of premature and low-birth-weight infants has increased, as has the incidence of a variety of neonatal diseases, such as hypoxic-ischemic encephalopathy, intraventricular hemorrhage, bronchopulmonary dysplasia, necrotizing enterocolitis, and retinopathy of prematurity. These diseases cause severe health conditions with poor prognoses, and existing control methods are ineffective for such diseases. Stem cells are a special type of cells with self-renewal and differentiation potential, and their mechanisms mainly include anti-inflammatory and anti-apoptotic properties, reducing oxidative stress, and boosting regeneration. Their paracrine effects can affect the microenvironment in which they survive, thereby affecting the biological characteristics of other cells. Due to their unique abilities, stem cells have been used in treating various diseases. Therefore, stem cell therapy may open up the possibility of treating such neonatal diseases. This review summarizes the research progress on stem cells and exosomes derived from stem cells in neonatal refractory diseases to provide new insights for most researchers and clinicians regarding future treatments. In addition, the current challenges and perspectives in stem cell therapy are discussed.

Liver Disease and Cell Therapy: Advances Made and Remaining Challenges

The limited availability of organs for liver transplantation, the ultimate curative treatment for end stage liver disease, has resulted in a growing and unmet need for alternative therapies. Mesenchymal stromal cells (MSCs) with their broad ranging anti-inflammatory and immunomodulatory properties have therefore emerged as a promising therapeutic agent in treating inflammatory liver disease. Significant strides have been made in exploring their biological activity. Clinical application of MSC has shifted the paradigm from using their regenerative potential to one which harnesses their immunomodulatory properties. Reassuringly, MSCs have been extensively investigated for over 30 years with encouraging efficacy and safety data from translational and early phase clinical studies, but questions remain about their utility. Therefore, in this review, we examine the translational and clinical studies using MSCs in various liver diseases and their impact on dampening immune-mediated liver damage. Our key observations include progress made thus far with use of MSCs for clinical use, inconsistency in the literature to allow meaningful comparison between different studies and need for standardized protocols for MSC manufacture and administration. In addition, the emerging role of MSC-derived extracellular vesicles as an alternative to MSC has been reviewed. We have also highlighted some of the remaining clinical challenges that should be addressed before MSC can progress to be considered as therapy for patients with liver disease.

Potential functions and therapeutic implications of glioma-resident mesenchymal stem cells

Mesenchymal stem cells (MSCs) are emerging crucial regulators in the tumor microenvironment (TME), which contributes to tumor progression and therapeutic resistance. MSCs are considered to be the stromal components of several tumors, their ultimate contribution to tumorigenesis and their potential to drive tumor stem cells, especially in the unique microenvironment of gliomas. Glioma-resident MSCs (GR-MSCs) are non-tumorigenic stromal cells. The phenotype of GR-MSCs is similar to that of prototype bone marrow-MSCs and GR-MSCs enhance the GSCs tumorigenicity via the IL-6/gp130/STAT3 pathway. The higher percentage of GR-MSCs in TME results in the poor prognosis of glioma patients and illuminate the tumor-promoting roles for GR-MSCs by secreting specific miRNA. Furthermore, the GR-MSC subpopulations associated with CD90 expression determine their different functions in glioma progression and CD90low MSCs generate therapeutic resistance by increasing IL-6-mediated FOXS1 expression. Therefore, it is urgent to develop novel therapeutic strategies targeting GR-MSCs for GBM patients. Despite that several functions of GR-MSCs have been confirmed, their immunologic landscapes and deeper mechanisms associated with the functions are not still expounded. In this review, we summarize the progress and potential function of GR-MSCs, as well as highlight their therapeutic implications based on GR-MSCs in GBM patients.

Self-Renewal and Pluripotency in Osteosarcoma Stem Cells' Chemoresistance: Notch, Hedgehog, and Wnt/β-Catenin Interplay with Embryonic Markers

Osteosarcoma is a highly malignant bone tumor derived from mesenchymal cells that contains self-renewing cancer stem cells (CSCs), which are responsible for tumor progression and chemotherapy resistance. Understanding the signaling pathways that regulate CSC self-renewal and survival is crucial for developing effective therapies. The Notch, Hedgehog, and Wnt/β-Catenin developmental pathways, which are essential for self-renewal and differentiation of normal stem cells, have been identified as important regulators of osteosarcoma CSCs and also in the resistance to anticancer therapies. Targeting these pathways and their interactions with embryonic markers and the tumor microenvironment may be a promising therapeutic strategy to overcome chemoresistance and improve the prognosis for osteosarcoma patients. This review focuses on the role of Notch, Hedgehog, and Wnt/β-Catenin signaling in regulating CSC self-renewal, pluripotency, and chemoresistance, and their potential as targets for anti-cancer therapies. We also discuss the relevance of embryonic markers, including SOX-2, Oct-4, NANOG, and KLF4, in osteosarcoma CSCs and their association with the aforementioned signaling pathways in overcoming drug resistance.

Stem Cell Therapy in Diabetic Polyneuropathy: Recent Advancements and Future Directions

Diabetic polyneuropathy (DPN) is the most frequent, although neglected, complication of long-term diabetes. Nearly 30% of hospitalized and 20% of community-dwelling patients with diabetes suffer from DPN; the incidence rate is approximately 2% annually. To date, there has been no curable therapy for DPN. Under these circumstances, cell therapy may be a vital candidate for the treatment of DPN. The epidemiology, classification, and treatment options for DPN are disclosed in the current review. Cell-based therapies using bone marrow-derived cells, embryonic stem cells, pluripotent stem cells, endothelial progenitor cells, mesenchymal stem cells, or dental pulp stem cells are our primary concern, which may be a useful treatment option to ease or to stop the progression of DPN. The importance of cryotherapies for treating DPN has been observed in several studies. These findings may help for the future researchers to establish more focused, accurate, effective, alternative, and safe therapy to reduce DPN. Cell-based therapy might be a permanent solution in the treatment and management of diabetes-induced neuropathy.

Preclinical Evaluation of interferon-gamma primed human Wharton's jelly-derived mesenchymal stem cells

The potential of human mesenchymal stem cells (MSCs) for cell therapy has been investigated in numerous immune-mediated conditions; MSCs are considered one of the most promising cellular therapeutics to treat intractable diseases. Recently, approaches to prime MSCs have been investigated, thereby generating cellular products with enhanced potential for a variety of clinical applications. Interferon-gamma (IFN-γ) priming is a current approach used to increase the therapeutic efficacy of MSCs. In this study, we determined the systemic toxicity, tumorigenicity and biodistribution of IFN-γ-primed Wharton's jelly-derived (WJ)-MSCs in male and female BALB/c-nu/nu mice. There were no deaths or pathologic lesions in the mice treated with 5 × 10⁶ cells/kg IFN-γ-primed MSCs in the repeated dose study. In the tumorigenicity study, one of the subcutaneously treated mice showed bronchioloalveolar adenoma in the lung but tested negative for human-specific anti-mitochondrial antibody, suggesting the spontaneous murine origin of the adenoma. A biodistribution study using real-time quantitative polymerase chain reaction demonstrated the systemic IFN-γ-primed MSC clearance by day 28. Based on the toxicity, biodistribution, and tumorigenicity studies, we concluded that IFN-γ-primed MSCs at 5 × 10⁶ cells/kg do not induce tumor formation and adverse changes.

The Therapeutic Potential of Mesenchymal Stem Cells in the Treatment of Diabetes Mellitus

Mesenchymal stem cells (MSCs) exist in many tissues and can differentiate into cells of multiple lineages, such as adipocytes, osteoblasts, or chondrocytes. MSC administration has demonstrated therapeutic potential in various degenerative and inflammatory diseases (e.g., graft-vs.-host disease, multiple sclerosis, Crohn's disease, organ fibrosis, and diabetes mellitus [DM]). The mechanisms involved in the therapeutic effects of MSCs are multifaceted. Generally, implanted MSCs can migrate to sites of injury, where they establish an anti-inflammatory and regenerative microenvironment in damaged tissues. In addition, MSCs can modulate innate and adaptive immune responses through immunosuppressive mechanisms that involve immune cells, inflammatory cytokines, chemokines, and immunomodulatory factors. DM has a high prevalence worldwide; it also contributes to a high rate of mortality worldwide. MSCs offer a promising therapeutic agent to prevent or repair damage from DM and diabetic complications through properties such as multilineage differentiation, homing, promotion of angiogenesis, and immunomodulation (e.g., prevention of oxidative stress, fibrosis, and cell death). In this study, we review current findings regarding the immunomodulatory and regenerative mechanisms of MSCs, as well as their therapeutic applications in DM and DM-related complications.

MiR-134-5p/Stat3 Axis Modulates Proliferation and Migration of MSCs Co-Cultured with Glioma C6 Cells by Regulating Pvt1 Expression

Mesenchymal stem cells (MSCs) are critical in regenerating tissues because they can differentiate into various tissue cells. MSCs interact closely with cells in the tissue microenvironment during the repair of damaged tissue. Although regarded as non-healing wounds, tumors can be treated by MSCs, which showed satisfactory treatment outcomes in previous reports. However, it is largely unknown whether the biological behaviors of MSCs would be affected by the tumor microenvironment. Exploring the truth of tumor microenvironmental cues driving MSCs tumor “wound” regeneration would provide a deeper understanding of the biological behavior of MSCs. Therefore, we mimicked the tumor microenvironment using co-cultured glioma C6 cells and rat MSCs, aiming to assess the proliferation and migration of MSCs and the associated effects of Stat3 in this process. The results showed that co-cultured MSCs significantly exhibited enhanced tumorigenic, migratory, and proliferative abilities. Both up-regulation of Stat3 and down-regulation of miR-134-5p were detected in co-cultured MSCs. Furthermore, miR-134-5p directly regulated Stat3 by binding to the sequence complementary to microRNA response elements in the 3′-UTR of its mRNA. Functional studies showed that both the migration and proliferation abilities of co-cultured MSCs were inhibited by miR-134-5p, whereas Stat3 gain-of-function treatment reversed these effects. In addition, Pvt1 was confirmed to be regulated by miR-134-5p through Stat3 and the suppression of Pvt1 reduced the migration and proliferation abilities of co-cultured MSCs. To sum up, these results demonstrate a suppressive role of miR-134-5p in tumor-environment-driven malignant transformation of rat MSCs through directly targeting Stat3, highlighting a crucial role of loss-of-function of miR-134-5p/Stat3 axis in the malignant transformation, providing a reference to the potential clinic use of MSCs.

Genetic profiling of human bone marrow mesenchymal stromal cells after in vitro expansion in clinical grade human platelet lysate

Mesenchymal stromal cells (MSCs) are non-hematopoietic cells that have a broad therapeutic potential. To obtain sufficient cells for clinical application, they must be expanded ex vivo. In the initial expansion protocols described, fetal calf serum (FCS) was used as the reference growth supplement, but more recently different groups started to replace FCS with platelet lysate (PL). We investigated in this study the impact of the culture supplement on gene expression of MSCs. Human bone marrow derived MSCs were expanded in vitro in FCS and PL supplemented medium. We found that MSCs expanded in PL-containing medium (PL-MSCs) express typical MSC immunomorphological features and can migrate, as their counterparts expanded in FCS-containing medium, through a layer of endothelial cells in vitro. Additionally, they show an increased proliferation rate compared to MSCs expanded in FCS medium (FCS-MSCs). RNA sequencing performed for MSCs cultured in both types of expansion medium revealed a large impact of the choice of growth supplement on gene expression: 1974 genes were at least twofold up- or downregulated. We focused on impact of genes involved in apoptosis and senescence. Our data showed that PL-MSCs express more anti-apoptotic genes and FCS-MSCs more pro-apoptotic genes. FCS-MSCs showed upregulation of senescence-related genes after four passages whereas this was rarer in PL-MSCs at the same timepoint. Since PL-MSCs show higher proliferation rates and anti-apoptotic gene expression, they might acquire features that predispose them to malignant transformation. We screened 10 MSC samples expanded in PL-based medium for the presence of tumor-associated genetic variants using a 165 gene panel and detected only 21 different genetic variants. According to our analysis, none of these were established pathogenic mutations. Our data show that differences in culture conditions such as growth supplement have a significant impact on the gene expression profile of MSCs and favor the use of PL over FCS for expansion of MSCs.

Advances in mesenchymal stromal cell therapy for acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) develops rapidly and has high mortality. ALI/ARDS is mainly manifested as acute or progressive hypoxic respiratory failure. At present, there is no effective clinical intervention for the treatment of ALI/ARDS. Mesenchymal stromal cells (MSCs) show promise for ALI/ARDS treatment due to their biological characteristics, easy cultivation, low immunogenicity, and abundant sources. The therapeutic mechanisms of MSCs in diseases are related to their homing capability, multidirectional differentiation, anti-inflammatory effect, paracrine signaling, macrophage polarization, the polarization of the MSCs themselves, and MSCs-derived exosomes. In this review, we discuss the pathogenesis of ALI/ARDS along with the biological characteristics and mechanisms of MSCs in the treatment of ALI/ARDS.

The secretome obtained under hypoxic preconditioning from human adipose-derived stem cells exerts promoted anti-apoptotic potentials through upregulated autophagic process

BACKGROUND

Hypoxic preconditioning (HP) is a stem cell preconditioning modality designed to augment the therapeutic effects of mesenchymal stem cells (MSCs). Although autophagy is expected to play a role in HP, very little is known regarding the relationship between HP and autophagy.

METHODS AND RESULTS

The adipose-derived stem cell (ASC)-secretome obtained under normoxia (NCM) and ASC-secretome obtained under HP (HCM) were obtained by culturing ASCs for 24 h under normoxic (21% partial pressure of O₂) and hypoxic (1% partial pressure of O₂) conditions, respectively. Subsequently, to determine the in vivo effects of HCM, each secretome was injected into 70% partially hepatectomized mice, and liver specimens were obtained. HCM significantly reduced the apoptosis of thioacetamide-treated AML12 hepatocytes and promoted the autophagic processes of the cells (P < 0.05). Autophagy blockage by either bafilomycin A1 or ATG5 siRNA significantly abrogated the anti-apoptotic effect of HCM (P < 0.05), demonstrating that HCM exerts its anti-apoptotic effect by promoting autophagy. The effect of HCM - reduction of cell apoptosis and promotion of autophagic process - was also demonstrated in a mouse model.

CONCLUSIONS

HP appears to induce ASCs to release a secretome with enhanced anti-apoptotic effects by promoting the autophagic process of ASCs.

Mesenchymal stromal cell-derived extracellular vesicles: novel approach in hematopoietic stem cell transplantation

Bone marrow mesenchymal stromal cells (MSCs) play a crucial role in the regulation of hematopoiesis. These cells affect the process through direct cell–cell contact, as well as releasing various trophic factors and extracellular vehicles (EVs) into the bone marrow microenvironment. MSC-derived EVs (MSC-EVs) are prominent intercellular communication tolls enriched with broad-spectrum bioactive factors such as proteins, cytokines, lipids, miRNAs, and siRNAs. They mimic some effects of MSCs by direct fusion with hematopoietic stem cells (HSC) membranes in the bone marrow (BM), thereby affecting HSC fate. MSC-EVs are attractive scope in cell-free therapy because of their unique capacity to repair BM tissue and regulate proliferation and differentiation of HSCs. These vesicles modulate the immune system responses and inhibit graft-versus-host disease following hematopoietic stem cell transplantation (HSCT). Recent studies have demonstrated that MSC-EVs play an influential role in the BM niches because of their unprecedented capacity to regulate HSC fate. Therefore, the existing paper intends to speculate upon the preconditioned MSC-EVs as a novel approach in HSCT.

Systemic Treatment of Soft Tissue Sarcomas in the Geriatric Population

OPINION STATEMENT

As the population ages, there will be an increase in the incidence and prevalence of soft tissue sarcoma (STS) within the geriatric population. As this disease disproportionately affects older adults, the percentage of adults >65 years old is expected to increase in the coming years. Geriatric patients are often more vulnerable to disease-related symptoms and have more difficulty tolerating treatment-related side effects. While there are no formal existing guidelines to direct the care of this geriatric patient population, it is of utmost importance to consider each patients' fitness and co-morbidities when selecting treatment plans. This review focuses on the current state of research of older adults with advanced or metastatic soft tissue sarcoma, highlighting the lack of representation of this patient population in clinical trials. Given that chronological age does not necessarily equate to physiologic age, integration of comprehensive geriatric and quality of life assessments is needed in the care of geriatric patients to help guide therapeutic decisions.

Advances in the Research of Osteosarcoma Stem Cells and its Related Genes

Osteosarcoma is a malignant tumor that often occurs in adolescents. There is an urgent need of new treatment options for osteosarcoma due to its poor prognosis after metastasis. Cancer stem cell theory states that cancer stem cells represent a small proportion of cancer cells. These cancer stem cells have self-renewal ability and are closely associated with cancer growth and metastasis as well as chemotherapy resistance. Similarly, osteosarcoma stem cells (OSCs) play an important role in the growth, metastasis, and chemotherapy resistance of osteosarcoma cells. Targeting OSCs may represent a future treatment of osteosarcoma. Furthermore, some genes have shown to regulate the growth, metastasis, and chemotherapy resistance of osteosarcoma cells by altering the stemness of OSCs. Targeting these genes may help in the treatment of osteosarcoma. This review mainly discusses recent advances in the research of OSCs and its related genes. This article is protected by copyright. All rights reserved.

Mesenchymal stem cell transfusion: Possible beneficial effects in COVID-19 patients

SARS-CoV-2 attaches to the angiotensin-converting enzyme 2 (ACE-2) receptor on human cells. The virus causes hypercytokinemia, capillary leak, pulmonary edema, acute respiratory distress syndrome, acute cardiac injury, and leads to death. Mesenchymal stem cells (MSCs) are ACE-2 negative cells; therefore, can escape from SARS-CoV-2. MSCs prevent hypercytokinemia and help the resolution of the pulmonary edema and other damages occurred during the course of COVID-19. In addition, MSCs enhance the regeneration of the lung and other tissues affected by SARS-CoV-2. The case series reported beneficial effect of MSCs in COVID-19 treatment. However, there are some concerns about the safety of MSCs, particularly referring to the increased risk of disseminated intravascular coagulation, and thromboembolism due to the expression of TF/CD142. Prospective, randomized, large scale studies are needed to reveal the optimum dose, administration way, time, efficacy, and safety of MSCs in the COVID-19 treatment.

Extracellular Vesicles in Osteosarcoma: Antagonists or Therapeutic Agents?

Osteosarcoma (OS) is a skeletal tumor affecting mainly children and adolescents. The presence of distance metastasis is frequent and it is localized preferentially to the lung, representing the main reason for death among patients. The therapeutic approaches are based on surgery and chemotherapeutics. However, the drug resistance and the side effects associated with the chemotherapy require the identification of new therapeutic approaches. The understanding of the complex biological scenario of the osteosarcoma will open the way for the identification of new targets for its treatment. Recently, a great interest of scientific community is for extracellular vesicles (EVs), that are released in the tumor microenvironment and are important regulators of tumor proliferation and the metastatic process. At the same time, circulating extracellular vesicles can be exploited as diagnostic and prognostic biomarkers, and they can be loaded with drugs as a new therapeutic approach for osteosarcoma patients. Thus, the characterization of OS-related EVs could represent a way to convert these vesicles from antagonists for human health into therapeutic and/or diagnostic agents.

Breast cancer dormancy is associated with a 4NG1 state and not senescence

Reactivation of dormant cancer cells can lead to cancer relapse, metastasis, and patient death. Dormancy is a nonproliferative state and is linked to late relapse and death. No targeted therapy is currently available to eliminate dormant cells, highlighting the need for a deeper understanding and reliable models. Here, we thoroughly characterize the dormant D2.OR and ZR-75-1, and proliferative D2A1 breast cancer cell line models in vivo and/or in vitro, and assess if there is overlap between a dormant and a senescent phenotype. We show that D2.OR but not D2A1 cells become dormant in the liver of an immunocompetent model. In vitro, we show that D2.OR and ZR-75-1 cells in response to a 3D environment or serum-free conditions are growth-arrested in G1, of which a subpopulation resides in a 4NG1 state. The dormancy state is reversible and not associated with a senescence phenotype. This will aid future research on breast cancer dormancy.

Extracellular vesicles from adipose tissue-derived stem cells alleviate osteoporosis through osteoprotegerin and miR-21-5p

Osteoporosis is one of the most common skeletal disorders caused by the imbalance between bone formation and resorption, resulting in quantitative loss of bone tissue. Since stem cell-derived extracellular vesicles (EVs) are growing attention as novel cell-free therapeutics that have advantages over parental stem cells, the therapeutic effects of EVs from adipose tissue-derived stem cells (ASC-EVs) on osteoporosis pathogenesis were investigated. ASC-EVs were isolated by a multi-filtration system based on the tangential flow filtration (TFF) system and characterized using transmission electron microscopy, dynamic light scattering, zeta potential, flow cytometry, cytokine arrays, and enzyme-linked immunosorbent assay. EVs are rich in growth factors and cytokines related to bone metabolism and mesenchymal stem cell (MSC) migration. In particular, osteoprotegerin (OPG), a natural inhibitor of receptor activator of nuclear factor-κB ligand (RANKL), was highly enriched in ASC-EVs. We found that the intravenous administration of ASC-EVs attenuated bone loss in osteoporosis mice. Also, ASC-EVs significantly inhibited osteoclast differentiation of macrophages and promoted the migration of bone marrow-derived MSCs (BM-MSCs). However, OPG-depleted ASC-EVs did not show anti-osteoclastogenesis effects, demonstrating that OPG is critical for the therapeutic effects of ASC-EVs. Additionally, small RNA sequencing data were analysed to identify miRNA candidates related to anti-osteoporosis effects. miR-21-5p in ASC-EVs inhibited osteoclast differentiation through Acvr2a down-regulation. Also, let-7b-5p in ASC-EVs significantly reduced the expression of genes related to osteoclastogenesis. Finally, ASC-EVs reached the bone tissue after they were injected intravenously, and they remained longer. OPG, miR-21-5p, and let-7b-5p in ASC-EVs inhibit osteoclast differentiation and reduce gene expression related to bone resorption, suggesting that ASC-EVs are highly promising as cell-free therapeutic agents for osteoporosis treatment.

Mesenchymal Stem/Stromal Cell-Derived Extracellular Vesicles for Chronic Kidney Disease: Are We There Yet?

Mesenchymal stem/stromal cells (MSCs) are the most utilized cell type for cellular therapy, partly due to their important proliferative potential and ability to differentiate into various cell types. MSCs produce large amounts of extracellular vesicles (EVs), which carry genetic and protein cargo to mediate MSC paracrine function. Recently, MSC-derived EVs have been successfully used in several preclinical models of chronic kidney disease. However, uncertainty remains regarding EV fate, safety, and long-term effects, which might impose important limitations on their path to clinical translation. This review discusses the therapeutic application of MSC-derived EV therapy for renal disease, with particular emphasis on potential mechanisms of kidney repair and major translational barriers. Emerging evidence indicates that the cargo of MSC-derived EVs is capable of modulating several pathways responsible for renal injury, including inflammation, oxidative stress, apoptosis, fibrosis, and microvascular remodeling. EV-induced modulation of these pathways has been associated with important renoprotective effects in experimental studies. However, scarce clinical data are available, and several challenges need to be addressed as we move toward clinical translation, including standardization of methods for EV isolation and characterization, EV fate, duration of EV effects, and effects of cardiovascular risk factors. MSC-derived EVs have the potential to preserve renal structure and function, but further experimental and clinical evidence is needed to confirm their protective effects in patients with chronic kidney disease.

Novel cell sources for bone regeneration

A plethora of both acute and chronic conditions, including traumatic, degenerative, malignant, or congenital disorders, commonly induce bone disorders often associated with severe persisting pain and limited mobility. Over 1 million surgical procedures involving bone excision, bone grafting, and fracture repair are performed each year in the U.S. alone, resulting in immense levels of public health challenges and corresponding financial burdens. Unfortunately, the innate self-healing capacity of bone is often inadequate for larger defects over a critical size. Moreover, as direct transplantation of committed osteoblasts is hindered by deficient cell availability, limited cell spreading, and poor survivability, an urgent need for novel cell sources for bone regeneration is concurrent. Thanks to the development in stem cell biology and cell reprogramming technology, many multipotent and pluripotent cells that manifest promising osteogenic potential are considered the regenerative remedy for bone defects. Considering these cells' investigation is still in its relative infancy, each of them offers their own particular challenges that must be conquered before the large-scale clinical application.

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

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

Transformed Canine and Murine Mesenchymal Stem Cells as a Model for Sarcoma with Complex Genomics

Simple Summary

Sarcomas are rare cancers of mesenchymal origin, the majority of which are characterized by many copy number alterations, amplifications, or deletions. Because of these complex genomics, it is notoriously difficult to identify driver events of malignant transformation. In this study, we show that murine and canine mesenchymal stem cells (MSCs) can be used to model spontaneous malignant transformation towards sarcomas with complex genomics. We show that these MSCs have an abnormal karyotype, many structural variants, and point mutations at whole genome sequencing analysis, and form sarcomas after injection into mice. Our cross-species analysis reveals that p53 loss is an early event in sarcomagenesis, and it was shown that MSCs with a knock-out in Trp53 transform earlier compared to wild-type MSCs. Our study points to the importance of p53 loss in the transformation process towards sarcomas with complex genomics.

Abstract

Sarcomas are rare mesenchymal tumors with a broad histological spectrum, but they can be divided into two groups based on molecular pathology: sarcomas with simple or complex genomics. Tumors with complex genomics can have aneuploidy and copy number gains and losses, which hampers the detection of early, initiating events in tumorigenesis. Often, no benign precursors are known, which is why good models are essential. The mesenchymal stem cell (MSC) is the presumed cell of origin of sarcoma. In this study, MSCs of murine and canine origin are used as a model to identify driver events for sarcomas with complex genomic alterations as they transform spontaneously after long-term culture. All transformed murine but not canine MSCs formed sarcomas after subcutaneous injection in mice. Using whole genome sequencing, spontaneously transformed murine and canine MSCs displayed a complex karyotype with aneuploidy, point mutations, structural variants, inter-chromosomal translocations, and copy number gains and losses. Cross-species analysis revealed that point mutations in Tp53/Trp53 are common in transformed murine and canine MSCs. Murine MSCs with a cre-recombinase induced deletion of exon 2–10 of Trp53 transformed earlier compared to wild-type murine MSCs, confirming the contribution of loss of p53 to spontaneous transformation. Our comparative approach using transformed murine and canine MSCs points to a crucial role for p53 loss in the formation of sarcomas with complex genomics.

Therapeutic Potential of Mesenchymal Stem Cells and Their Products in Lung Diseases-Intravenous Administration versus Inhalation

The number of publications studying the therapeutic use of stem cells has steadily increased since 2000. Compared to other applications, there has been little interest in the evaluation of mesenchymal stem cells (MSCs) and MSC-derived products (mostly extracellular vesicles) for the treatment of respiratory diseases. Due to the lack of efficient treatments for acute respiratory distress syndrome caused by infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the action of MSCs has also been studied. This review describes mode of action and use of MSCs and MSC-derived products in the treatment of lung diseases including the respective advantages and limitations of the products. Further, issues related to standardized production are addressed. Administration by inhalation of MSCs, compared to intravenous injection, could decrease cell damage by shear stress, eliminate the barrier to reach target cells in the alveoli, prevent thrombus formation in the pulmonary vasculature and retention in filter for extracorporeal membrane oxygenation. There is more feasible to deliver extracellular vesicles than MSCs with inhalers, offering the advantage of non-invasive and repeated administration by the patient. Major obstacles for comparison of results are heterogeneity of the products, differences in the treatment protocols and small study cohorts.

Immunopathology of Type 1 Diabetes and Immunomodulatory Effects of Stem Cells: A Narrative Review of the Literature

Type 1 Diabetes (T1D) is a complex autoimmune disorder which occurs as a result of an intricate series of pathologic interactions between pancreatic β-cells and a wide range of components of both the innate and the adaptive immune systems. Stem-cell therapy, a recently-emerged potentially therapeutic option for curative treatment of diabetes, is demonstrated to cause significant alternations to both different immune cells such as macrophages, natural killer (NK) cells, dendritic cells, T cells, and B cells and non-cellular elements including serum cytokines and different components of the complement system. Although there exists overwhelming evidence indicating that the documented therapeutic effects of stem cells on patients with T1D is primarily due to their potential for immune regulation rather than pancreatic tissue regeneration, to date, the precise underlying mechanisms remain obscure. On the other hand, immune-mediated rejection of stem cells remains one of the main obstacles to regenerative medicine. Moreover, the consequences of efferocytosis of stem-cells by the recipients' lung-resident macrophages have recently emerged as a responsible mechanism for some immune-mediated therapeutic effects of stem-cells. This review focuses on the nature of the interactions amongst different compartments of the immune systems which are involved in the pathogenesis of T1D and provides explanation as to how stem cell-based interventions can influence immune system and maintain the physiologic equilibrium.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Potential Therapeutic Strategy for Acute Kidney Injury

Acute kidney injury (AKI) is a common and potential life-threatening disease in patients admitted to hospital, affecting 10%-15% of all hospitalizations and around 50% of patients in the intensive care unit. Severe, recurrent, and uncontrolled AKI may progress to chronic kidney disease or end-stage renal disease. AKI thus requires more efficient, specific therapies, rather than just supportive therapy. Mesenchymal stem cells (MSCs) are considered to be promising cells for cellular therapy because of their ease of harvesting, low immunogenicity, and ability to expand in vitro. Recent research indicated that the main therapeutic effects of MSCs were mediated by MSC-derived extracellular vesicles (MSC-EVs). Furthermore, compared with MSCs, MSC-EVs have lower immunogenicity, easier storage, no tumorigenesis, and the potential to be artificially modified. We reviewed the therapeutic mechanism of MSCs and MSC-EVs in AKI, and considered recent research on how to improve the efficacy of MSC-EVs in AKI. We also summarized and analyzed the potential and limitations of EVs for the treatment of AKI to provide ideas for future clinical trials and the clinical application of MSC-EVs in AKI.

Endoglin Targeting: Lessons Learned and Questions That Remain

Approximately 30 years ago, endoglin was identified as a transforming growth factor (TGF)-β coreceptor with a crucial role in developmental biology and tumor angiogenesis. Its selectively high expression on tumor vessels and its correlation with poor survival in cancer patients led to the exploration of endoglin as a therapeutic target for cancer. The endoglin neutralizing antibody TRC105 (Carotuximab^®, Tracon Pharmaceuticals (San Diego, CA, USA) was subsequently tested in a wide variety of preclinical cancer models before being tested in phase I-III clinical studies in cancer patients as both a monotherapy and in combination with other chemotherapeutic and anti-angiogenic therapies. The combined data of these studies have revealed new insights into the role of endoglin in angiogenesis and its expression and functional role on other cells in the tumor microenvironment. In this review, we will summarize the preclinical work, clinical trials and biomarker studies of TRC105 and explore what these studies have enabled us to learn and what questions remain unanswered.

Therapeutic potential of mesenchymal stem cells in treating both types of diabetes mellitus and associated diseases

Diabetes mellitus is a common lifestyle disease which can be classified into type 1 diabetes mellitus and type 2 diabetes mellitus. While both result in hyperglycemia due to lack of insulin action and further associated chronic ailments, there is a marked distinction in the cause for each type due to which both require a different prophylaxis. As observed, type 1 diabetes is caused due to the autoimmune action of the body resulting in the destruction of pancreatic islet cells. On the other hand, type 2 diabetes is caused either due to insulin resistance of target cells or lack of insulin production as per physiological requirements. Attempts to cure the disease have been made by bringing drastic changes in the patients' lifestyle; parenteral administration of insulin; prescription of drugs such as biguanides, meglitinides, and amylin; pancreatic transplantation; and immunotherapy. While these attempts cause a certain degree of relief to the patient, none of these can cure diabetes mellitus. However, a new treatment strategy led by the discovery of mesenchymal stem cells and their unique immunomodulatory and multipotent properties has inspired therapies to treat diabetes by essentially reversing the conditions causing the disease. The current review aims to enumerate the role of various mesenchymal stem cells and the different approaches to treat both types of diabetes and its associated diseases as well.

Mesenchymal Stem Cell Therapy for Diabetic Kidney Disease: A Review of the Studies Using Syngeneic, Autologous, Allogeneic, and Xenogeneic Cells

Diabetic kidney disease (DKD) is a microvascular complication of diabetes mellitus (DM) and comprises multifactorial pathophysiologic mechanisms. Despite current treatment, around 30-40% of individuals with type 1 and type 2 DM (DM1 and DM2) have progressive DKD, which is the most common cause of end-stage chronic kidney disease worldwide. Mesenchymal stem cell- (MSC-) based therapy has important biological and therapeutic implications for curtailing DKD progression. As a chronic disease, DM may impair MSC microenvironment, but there is compelling evidence that MSC derived from DM1 individuals maintain their cardinal properties, such as potency, secretion of trophic factors, and modulation of immune cells, so that both autologous and allogeneic MSCs are safe and effective. Conversely, MSCs derived from DM2 individuals are usually dysfunctional, exhibiting higher rates of senescence and apoptosis and a decrease in clonogenicity, proliferation, and angiogenesis potential. Therefore, more studies in humans are needed to reach a conclusion if autologous MSCs from DM2 individuals are effective for treatment of DM-related complications. Importantly, the bench to bedside pathway has been constructed in the last decade for assessing the therapeutic potential of MSCs in the DM setting. Laboratory research set the basis for establishing further translation research including preclinical development and proof of concept in model systems. Phase I clinical trials have evaluated the safety profile of MSC-based therapy in humans, and phase II clinical trials (proof of concept in trial participants) still need to answer important questions for treating DKD, yet metabolic control has already been documented. Therefore, randomized and controlled trials considering the source, optimal cell number, and route of delivery in DM patients are further required to advance MSC-based therapy. Future directions include strategies to reduce MSC heterogeneity, standardized protocols for isolation and expansion of those cells, and the development of well-designed large-scale trials to show significant efficacy during a long follow-up, mainly in individuals with DKD.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Alleviation of acute radiation-induced bone marrow failure in mice with human fetal placental stromal cell therapy

Purpose

Selected placental mesenchymal stromal cells isolated from the fetal mesenchymal placental tissues (f-hPSCs) were tested as cell therapy of lethal acute radiation syndrome (ARS) with bone marrow regeneration and induced extramedullary hematopoiesis.

Methods and materials

f-hPSCs were isolated from the chorionic plate of human placentae and further expanded in regular culture conditions. 2 × 10⁶ f-hPSCs were injected on days 1 and 4 to 8-Gy total body irradiated (TBI) C3H mice, both intramuscularly and subcutaneously. Pre-splenectomized TBI mice were used to test the involvement of extramedullary spleen hematopoiesis in the f-hPSC-induced hematopoiesis recovery in the TBI mice. Weight and survival of the mice were followed up within the morbid period of up to 23 days following irradiation. The role of hematopoietic progenitors in the recovery of treated mice was evaluated by flow cytometry, blood cell counts, and assay of possibly relevant growth factors.

Results and conclusions

The survival rate of all groups of TBI f-hPSC-treated mice at the end of the follow-up was dramatically elevated from < 10% in untreated to ~ 80%, with a parallel regain of body weight, bone marrow (BM) recovery, and elevated circulating progenitors of blood cell lineages. Blood erythropoietin levels were elevated in all f-hPSC-treated mice. Extramedullary splenic hematopoiesis was recorded in the f-hPSC-treated mice, though splenectomized mice still had similar survival rate. Our findings suggest that the indirect f-hPSC life-saving therapy of ARS may also be applied for treating other conditions with a failure of the hematopoietic system and severe pancytopenia.

The Application of MSCs-Derived Extracellular Vesicles in Bone Disorders: Novel Cell-Free Therapeutic Strategy

Bone is crucial for supporting the body, protecting other organs, providing minerals, and secreting hormone to regulate other organ's function. Bone disorders result in pain and disability, severely affecting human health, reducing the quality of life and increasing costs to society. With the rapid increase in the aging population worldwide, bone disorders have become one major disease. As a result, efficacious therapies of bone disorders have become the focus of attention worldwide. Mesenchymal stem cells (MSCs) have been widely explored as a new therapeutic method for numerous diseases. Recent evidence suggests that the therapeutic effects of MSCs are mainly mediated by their extracellular vesicles (EV). MSCs-derived extracellular vesicles (MSCs-EV) is indicated as a novel cell-free alternative to cell therapy with MSCs in regenerative medicine. Here, we review the current knowledge of EV and highlight the application studies of MSCs-EV in bone disorders by focusing on osteoarthritis (OA), rheumatoid arthritis (RA), osteoporosis (OP), and bone fracture. Moreover, we discuss the key issues and perspectives of MSCs-EV as a clinical therapeutic strategy for bone diseases.

Mesenchymal Stromal Cells, a New Player in Reducing Complications From Liver Transplantation?

In response to the global burden of liver disease there has been a commensurate increase in the demand for liver transplantation. However, due to a paucity of donor organs many centers have moved toward the routine use of marginal allografts, which can be associated with a greater risk of complications and poorer clinical outcomes. Mesenchymal stromal cells (MSC) are a multi-potent progenitor cell population that have been utilized to modulate aberrant immune responses in acute and chronic inflammatory conditions. MSC exert an immunomodulatory effect on innate and adaptive immune systems through the release of both paracrine soluble factors and extracellular vesicles. Through these routes MSC can switch the regulatory function of the immune system through effects on macrophages and T regulatory cells enabling a switch of phenotype from injury to restoration. A key benefit seems to be their ability to tailor their response to the inflammatory environment without compromising the host ability to fight infection. With over 200 clinical trials registered to examine MSC therapy in liver disease and an increasing number of trials of MSC therapy in solid organ transplant recipients, there is increasing consideration for their use in liver transplantation. In this review we critically appraise the potential role of MSC therapy in the context of liver transplantation, including their ability to modulate reperfusion injury, their role in the reduction of medium term complications in the biliary tree and their potential to enhance tolerance in transplanted organs.

Epidemiology and Risk Factors of Osteosarcoma

Osteosarcoma is a rare tumor diagnosed at any age; however younger age is a common risk factor. In addition, multiple factors are believed to contribute to higher rates of osteosarcoma, particularly race and gender. Although diagnosed worldwide, osteosarcoma is found to be more prevalent in Africa with high numbers of cases reported in Nigeria, Uganda, and Sudan. Additionally, higher rates are detected in African Americans, suggesting a genetic predisposition linked to race. This review focuses on identifying high risk factors of osteosarcoma with an emphasis on sarcoma epidemiology and risk factors in African countries.

Interplay between mesenchymal stem cell and tumor and potential application

Mesenchymal stem cells (MSCs) possess the capabilities of self-renewal and multipotent differentiation. Firstly isolated from bone marrow, MSCs are subsequently identified from various post-natal tissue types. Based the differentiation into tissue-specific cells, MSCs were capable of replacing damaged and diseased tissues. In addition, MSCs have been demonstrated to possess important immunomodulatory properties. Increasing data showed that MSCs exhibited tropism for sites of the tumor microenvironment and interacted with tumor cells closely through paracrine signaling. Therefore, better understanding of crosstalk between MSCs and tumor cells will be able to develop potential strategies in the treatment of tumors in the future. Herein, we summarize the research progress of the influence of MSCs on tumor cells and the prospect of their application in tumor therapy in this review.

Stammzellen in der Regenerativen Medizin – Translationale Hürden und Möglichkeiten zur Überwindung

Der Einsatz von mesenchymalen Stammzellen in der regenerativen Medizin wird immer populärer. Nichtsdestotrotz ist ihre Anwendung im klinischen Alltag noch immer limitiert. Zahlreiche ethische, rechtliche und translationale Probleme sowie Ungewissheit bzgl. der Sicherheit hemmen noch immer die Entstehung von entsprechenden Therapien aus vielversprechenden wissenschaftlichen Ansätzen.

Diese Arbeit soll die Hauptprobleme bei der Translation von stammzellbasierten Therapien aus der Grundlagenforschung und Präklinik in den klinischen Alltag darstellen, sowie Ansätze aufzeigen, diese zu überwinden.

Generation of induced secretome from adipose-derived stem cells specialized for disease-specific treatment: An experimental mouse model

BACKGROUND

Recently, the exclusive use of mesenchymal stem cell (MSC)-secreted molecules, named as the secretome, have been evaluated for overcoming the limitations of cell-based therapy while maintaining its advantages.

AIM

To improve cell-free therapy by adding disease-specificity through stimulation of MSCs using disease-causing materials.

METHODS

We collected the secretory materials (named as inducers) released from AML12 hepatocytes that had been pretreated with thioacetamide (TAA) and generated the TAA-induced secretome (TAA-isecretome) after stimulating adipose-derived stem cells with the inducers. The TAA-isecretome was intravenously administered to mice with TAA-induced hepatic failure and those with partial hepatectomy.

RESULTS

TAA-isecretome infusion showed higher therapeutic potential in terms of (1) restoring disorganized hepatic tissue to normal tissue; (2) inhibiting proinflammatory cytokines (interleukin-6 and tumor necrosis factor-α); and (3) reducing abnormally elevated liver enzymes (aspartate aminotransferase and alanine aminotransferase) compared to the naïve secretome infusion in mice with TAA-induced hepatic failure. However, the TAA-isecretome showed inferior therapeutic potential for restoring hepatic function in partially hepatectomized mice. Proteomic analysis of TAA-isecretome identified that antioxidant processes were the most predominant enriched biological networks of the proteins exclusively identified in the TAA-isecretome. In addition, peroxiredoxin-1, a potent antioxidant protein, was found to be one of representative components of TAA-isecretome and played a central role in the protection of TAA-induced hepatic injury.

CONCLUSION

Appropriate stimulation of adipose-derived stem cells with TAA led to the production of a secretome enriched with proteins, especially peroxiredoxin-1, with higher antioxidant activity. Our results suggest that appropriate stimulation of MSCs with pathogenic agents can lead to the production of a secretome specialized for protecting against the pathogen. This approach is expected to open a new way of developing various specific therapeutics based on the high plasticity and responsiveness of MSCs.

Harnessing the anti-inflammatory properties of stem cells for transplant therapy in hemorrhagic stroke

Hemorrhagic stroke is a global health crisis plagued by neuroinflammation in the acute and chronic phases. Neuroinflammation approximates secondary cell death, which in turn robustly contributes to stroke pathology. Both the physiological and behavioral symptoms of stroke correlate with various inflammatory responses in animal and human studies. That slowing the secondary cell death mediated by this inflammation may attenuate stroke pathology presents a novel treatment strategy. To this end, experimental therapies employing stem cell transplants support their potential for neuroprotection and neuroregeneration after hemorrhagic stroke. In this review, we evaluate experiments using different types of stem cell transplants as treatments for stroke-induced neuroinflammation. We also update this emerging area by examining recent preclinical and clinical trials that have deployed these therapies. While further investigations are warranted to solidify their therapeutic profile, the reviewed studies largely posit stem cells as safe and potent biologics for stroke, specifically owing to their mode of action for sequestering neuroinflammation and promoting neuroregenerative processes.

An Update on the Progress of Isolation, Culture, Storage, and Clinical Application of Human Bone Marrow Mesenchymal Stem/Stromal Cells

Bone marrow mesenchymal stem/stromal cells (BMSCs), which are known as multipotent cells, are widely used in the treatment of various diseases via their self-renewable, differentiation, and immunomodulatory properties. In-vitro and in-vivo studies have supported the understanding mechanisms, safety, and efficacy of BMSCs therapy in clinical applications. The number of clinical trials in phase I/II is accelerating; however, they are limited in the size of subjects, regulations, and standards for the preparation and transportation and administration of BMSCs, leading to inconsistency in the input and outcome of the therapy. Based on the International Society for Cellular Therapy guidelines, the characterization, isolation, cultivation, differentiation, and applications can be optimized and standardized, which are compliant with good manufacturing practice requirements to produce clinical-grade preparation of BMSCs. This review highlights and updates on the progress of production, as well as provides further challenges in the studies of BMSCs, for the approval of BMSCs widely in clinical application.

The Importance of Stem Cell Senescence in Regenerative Medicine

Mesenchymal stem cells (MSCs) are an interesting tool in regenerative medicine and a unique cell-based therapy to treat aging-associated diseases. Successful MSC therapy needs a large-scale cell culture, and requires a prolonged in vitro cell culture that subsequently leads to cell senescence. Administration of senescent MSCs results in inefficient cell differentiation in the clinical setting. Therefore, it is of utmost importance to enhance our knowledge about the aging process and methods to detect cell senescence in order to overcome this challenge. Numerous studies have addressed senescence in various aspects. Here, we review the characteristics of MSCs, how aging affects their features, mechanisms involved in aging of MSCs, and potential approaches to detect MSC senescence in vitro.

Convergence of Cell Pharmacology and Drug Delivery

Cellular therapy is enabling new approaches to tackle significant unmet needs in areas such as regenerative medicine and immunotherapy. The pharmacology of cell therapeutics becomes of critical importance to assure that these new drugs work reproducibly and effectively. Cell pharmacology can benefit from adapting principles of classical molecular drug pharmacokinetics (PK) and pharmacodynamics (PD) to quantitatively understand rate-limiting constraints of cell fate after administration. Future innovations focused on improvements in drug delivery using a PK/PD perspective can aid in designing a cell therapeutic product to overcome any pharmacological barriers for a given disease application. Herein, we present a perspective on the development of an ex vivo mesenchymal stromal therapeutic using a PK/PD framework and also present examples of general cell engineering techniques that implicitly influence the PK/PD curve by genetically modifying cells to regulate their in vivo duration, biodistribution, and activity. Stem Cells Translational Medicine 2019;8:874&879.

A Comparison of Phenotypic and Functional Properties of Mesenchymal Stromal Cells and Multipotent Adult Progenitor Cells

Both Multipotent Adult Progenitor Cells and Mesenchymal Stromal Cells are bone-marrow derived, non-haematopoietic adherent cells, that are well-known for having immunomodulatory and pro-angiogenic properties, whilst being relatively non-immunogenic. However, they are phenotypically and functionally distinct cell types, which has implications for their efficacy in different settings. In this review we compare the phenotypic and functional properties of these two cell types, to help in determining which would be the superior cell type for different applications.

Transplantation of induced pluripotent stem cell-derived mesenchymal stem cells improved erectile dysfunction induced by cavernous nerve injury

Erectile dysfunction (ED) is an important kind of postoperative complication of pelvic surgery that affects patients' quality of life. Transplantation of mesenchymal stem cells (MSC) has been found to alleviate ED caused by cavernous nerve injury (CNI) in rats. However, little is known about whether induced pluripotent stem cell-derived mesenchymal stem cells (iMSC) have a therapeutic effect on CNI ED. We established an ED model on rats and evaluated the effect of iMSC on it. Methods: Eight-week-old male Sprague-Dawley rats were assigned to four groups and received following operation: sham operation (sham group); bilateral CNI and phosphate-buffered saline (PBS) injections (PBS group); bilateral CNI and adipose-derived mesenchymal stem cells transplantation (adMSC group); or bilateral CNI and iMSC injection (iMSC group). After therapy, the cavernous nerve was stimulated by electricity and the intracavernous pressure (IAP)/mean arterial blood pressure (MAP) was measured. The endothelial and smooth muscle tissue in the penis was assessed histologically with Masson's trichrome stain. Immunofluorescence/immunohistochemical stains were applied for the detection of nNOS, vWF, eNOS, SMA, Desmin, S100β, and caspase-3. Nude rats CNI ED model was established for the evaluation of iMSC longevity and differentiation capacity. The paracrine factors were assessed by real-time PCR. Results: Transplantation of iMSC significantly restored the IAP/MAP in this CNI ED model and showed long-term effects. It could rescue the expression of vWF, eNOS, SMA, and Desmin, which indicated the alleviation of endothelial and smooth muscle tissues of the penis. iMSC therapy also could increase the expression of nNOS in the cavernosum and S100β in the major pelvic ganglia (MPG) which contributed to the erectile function. Moreover, the level of BAX and caspase-3 were reduced and Bcl-2 was increased, which indicated the anti-apoptosis effects of iMSC. The iMSC showed little transdifferentiation and exerted their function by activating the secretome of the host. Conclusion: Transplantation of iMSC significantly improved ED induced by CNI. The iMSC may exert their effects via paracrine factors and may be a promising therapeutic candidate for treating CNI ED in the future.

Tumor Formation of Adult Stem Cell Transplants in Rodent Arthritic Joints

PURPOSE

While imaging matrix-associated stem cell transplants aimed for cartilage repair in a rodent arthritis model, we noticed that some transplants formed locally destructive tumors. The purpose of this study was to determine the cause for this tumor formation in order to avoid this complication for future transplants.

PROCEDURES

Adipose-derived stem cells (ADSC) isolated from subcutaneous adipose tissue were implanted into 24 osteochondral defects of the distal femur in ten athymic rats and two immunocompetent control rats. All transplants underwent serial magnetic resonance imaging (MRI) up to 6 weeks post-transplantation to monitor joint defect repair. Nine transplants showed an increasing size over time that caused local bone destruction (group 1), while 11 transplants in athymic rats (group 2) and 4 transplants in immunocompetent rats did not. We compared the ADSC implant size and growth rate on MR images, macroscopic features, histopathologic features, surface markers, and karyotypes of these presumed neoplastic transplants with non-neoplastic ADSC transplants.

RESULTS

Implants in group 1 showed a significantly increased two-dimensional area at week 2 (p = 0.0092), 4 (p = 0.003), and 6 (p = 0.0205) compared to week 0, as determined by MRI. Histopathological correlations confirmed neoplastic features in group 1 with significantly increased size, cellularity, mitoses, and cytological atypia compared to group 2. Six transplants in group 1 were identified as malignant chondrosarcomas and three transplants as fibromyxoid sarcomas. Transplants in group 2 and immunocompetent controls exhibited normal cartilage features. Both groups showed a normal ADSC phenotype; however, neoplastic ADSC demonstrated a mixed population of diploid and tetraploid cells without genetic imbalance.

CONCLUSIONS

ADSC transplants can form tumors in vivo. Preventive actions to avoid in vivo tumor formations may include karyotyping of culture-expanded ADSC before transplantation. In addition, serial imaging of ADSC transplants in vivo may enable early detection of abnormally proliferating cell transplants.

Long-term culture of mesenchymal stem cells impairs ATM-dependent recognition of DNA breaks and increases genetic instability

BACKGROUND

Mesenchymal stem cells (MSCs) are attracting increasing interest for cell-based therapies, making use of both their immuno-modulating and regenerative potential. For such therapeutic applications, a massive in vitro expansion of donor cells is usually necessary to furnish sufficient material for transplantation. It is not established to what extent the long-term genomic stability and potency of MSCs can be compromised as a result of this rapid ex vivo expansion. In this study, we investigated the DNA damage response and chromosomal stability (indicated by micronuclei induction) after sub-lethal doses of gamma irradiation in murine MSCs at different stages of their in vitro expansion.

METHODS

Bone-marrow-derived tri-potent MSCs were explanted from 3-month-old female FVB/N mice and expanded in vitro for up to 12 weeks. DNA damage response and repair kinetics after gamma irradiation were quantified by the induction of γH2AX/53BP1 DSB repair foci. Micronuclei were counted in post-mitotic, binucleated cells using an automated image analyzer Metafer4. Involvement of DNA damage response pathways was tested using chemical ATM and DNA-PK inhibitors.

RESULTS

Murine bone-marrow-derived MSCs in long-term expansion culture gradually lose their ability to recognize endogenous and radiation-induced DNA double-strand breaks. This impaired DNA damage response, indicated by a decrease in the number of γH2AX/53BP1 DSB repair foci, was associated with reduced ATM dependency of foci formation, a slower DNA repair kinetics, and an increased number of residual DNA double-strand breaks 7 h post irradiation. In parallel with this impaired efficiency of DNA break recognition and repair in older MSCs, chromosomal instability after mitosis increased significantly as shown by a higher number of micronuclei, both spontaneously and induced by γ-irradiation. Multifactorial regression analysis demonstrates that in vitro aging reduced DNA damage recognition in MSCs after irradiation by a multiplicative interaction with dose (p < 0.0001), whereas the increased frequency of micronuclei was caused by an additive interaction between in vitro aging and radiation dose.

CONCLUSION

The detrimental impact of long-term in vitro expansion on DNA damage response of MSCs warrants a regular monitoring of this process during the ex vivo growth of these cells to improve therapeutic safety and efficiency.