Mesenchymal stem cells conditioned with glucose depletion augments their ability to repair-infarcted myocardium

Therapeutic applications of mesenchymal/medicinal stem/signaling cells preconditioned with external factors: Are there more efficient approaches to utilize their regenerative potential?

Mesenchymal/medicinal stem/signaling cells (MSCs) have emerged as a promising treatment option for various disorders. However, the donor's age, advanced stage of disease, and prolonged in vitro expansion often diminish the innate regenerative potential of MSCs. Besides that, the absence of MSCs' comprehensive "pre-admission testing" can result in the injection of cells with reduced viability and function, which may negatively affect the overall outcome of MSC-based therapies. It is, therefore, essential to develop effective strategies to improve the impaired biological performance of MSCs. This review focuses on the comprehensive characterization of various methods of external MSCs stimulation (hypoxia, heat shock, caloric restriction, acidosis, 3D culture, and application of extracellular matrix) that augment their medicinal potential. To emphasize the significance of MSCs priming, we summarize the effects of individual and combined preconditioning approaches, highlighting their impact on MSCs' response to either physiological or pathological conditions. We further investigate the synergic action of exogenous factors to maximize MSCs' therapeutic potential. Not to omit the field of tissue engineering, the application of pretreated MSCs seeded on scaffolds is discussed as well.

Application of mesenchymal stem cells for anti-senescence and clinical challenges

Senescence is a hot topic nowadays, which shows the accumulation of senescent cells and inflammatory factors, leading to the occurrence of various senescence-related diseases. Although some methods have been identified to partly delay senescence, such as strengthening exercise, restricting diet, and some drugs, these only slow down the process of senescence and cannot fundamentally delay or even reverse senescence. Stem cell-based therapy is expected to be a potential effective way to alleviate or cure senescence-related disorders in the coming future. Mesenchymal stromal cells (MSCs) are the most widely used cell type in treating various diseases due to their potentials of self-replication and multidirectional differentiation, paracrine action, and immunoregulatory effects. Some biological characteristics of MSCs can be well targeted at the pathological features of aging. Therefore, MSC-based therapy is also a promising strategy to combat senescence-related diseases. Here we review the recent progresses of MSC-based therapies in the research of age-related diseases and the challenges in clinical application, proving further insight and reference for broad application prospects of MSCs in effectively combating senesce in the future.

Innovative therapeutic strategies for cardiovascular disease

As a significant non-communicable disease, cardiovascular disease is the leading cause of death for both men and women, comprises almost twenty percent of deaths in most racial and ethnic groups, can affect greater than twenty-five million individuals worldwide over the age of twenty, and impacts global economies with far-reaching financial challenges. Multiple factors can affect the onset of cardiovascular disease that include high serum cholesterol levels, elevated blood pressure, tobacco consumption and secondhand smoke exposure, poor nutrition, physical inactivity, obesity, and concurrent diabetes mellitus. Yet, addressing any of these factors cannot completely eliminate the onset or progression of cardiovascular disorders. Novel strategies are necessary to target underlying cardiovascular disease mechanisms. The silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), a histone deacetylase, can limit cardiovascular injury, assist with stem cell development, oversee metabolic homeostasis through nicotinamide adenine dinucleotide (NAD+) pathways, foster trophic factor protection, and control cell senescence through the modulation of telomere function. Intimately tied to SIRT1 pathways are mammalian forkhead transcription factors (FoxOs) which can modulate cardiac disease to reduce oxidative stress, repair microcirculation disturbances, and reduce atherogenesis through pathways of autophagy, apoptosis, and ferroptosis. AMP activated protein kinase (AMPK) also is critical among these pathways for the oversight of cardiac cellular metabolism, insulin sensitivity, mitochondrial function, inflammation, and the susceptibility to viral infections such as severe acute respiratory syndrome coronavirus that can impact cardiovascular disease. Yet, the relationship among these pathways is both intricate and complex and requires detailed insight to successfully translate these pathways into clinical care for cardiovascular disorders.

Epigenetic Modification Factors and microRNAs Network Associated with Differentiation of Embryonic Stem Cells and Induced Pluripotent Stem Cells toward Cardiomyocytes: A Review

More research is being conducted on myocardial cell treatments utilizing stem cell lines that can develop into cardiomyocytes. All of the forms of cardiac illnesses have shown to be quite amenable to treatments using embryonic (ESCs) and induced pluripotent stem cells (iPSCs). In the present study, we reviewed the differentiation of these cell types into cardiomyocytes from an epigenetic standpoint. We also provided a miRNA network that is devoted to the epigenetic commitment of stem cells toward cardiomyocyte cells and related diseases, such as congenital heart defects, comprehensively. Histone acetylation, methylation, DNA alterations, N6-methyladenosine (m⁶a) RNA methylation, and cardiac mitochondrial mutations are explored as potential tools for precise stem cell differentiation.

The role of cellular senescence in cardiac disease: basic biology and clinical relevance

Cellular senescence, classically defined as stable cell cycle arrest, is implicated in biological processes such as embryogenesis, wound healing and ageing. Senescent cells have a complex senescence-associated secretory phenotype (SASP), involving a range of pro-inflammatory factors with important paracrine and autocrine effects on cell and tissue biology. Clinical evidence and experimental studies link cellular senescence, senescent cell accumulation, and the production and release of SASP components with age-related cardiac pathologies such as heart failure, myocardial ischaemia and infarction, and cancer chemotherapy-related cardiotoxicity. However, the precise role of senescent cells in these conditions is unclear and, in some instances, both detrimental and beneficial effects have been reported. The involvement of cellular senescence in other important entities, such as cardiac arrhythmias and remodelling, is poorly understood. In this Review, we summarize the basic biology of cellular senescence and discuss what is known about the role of cellular senescence and the SASP in heart disease. We then consider the various approaches that are being developed to prevent the accumulation of senescent cells and their consequences. Many of these strategies are applicable in vivo and some are being investigated for non-cardiac indications in clinical trials. We end by considering important knowledge gaps, directions for future research and the potential implications for improving the management of patients with heart disease.

Strategies to improve regenerative potential of mesenchymal stem cells

In the last few decades, stem cell-based therapies have gained attention worldwide for various diseases and disorders. Adult stem cells, particularly mesenchymal stem cells (MSCs), are preferred due to their significant regenerative potential in cellular therapies and are currently involved in hundreds of clinical trials. Although MSCs have high self-renewal as well as differentiation potential, such abilities are compromised with “advanced age” and “disease status” of the donor. Similarly, cell-based therapies require high cell number for clinical applications that often require in vitro expansion of cells. It is pertinent to note that aged individuals are the main segment of population for stem cell-based therapies, however; autologous use of stem cells for such patients (aged and diseased) does not seem to give optimal results due to their compromised potential. In vitro expansion to obtain large numbers of cells also negatively affects the regenerative potential of MSCs. It is therefore essential to improve the regenerative potential of stem cells compromised due to “in vitro expansion”, “donor age” and “donor disease status” for their successful autologous use. The current review has been organized to address the age and disease depleted function of resident adult stem cells, and the strategies to improve their potential. To combat the problem of decline in the regenerative potential of cells, this review focuses on the strategies that manipulate the cell environment such as hypoxia, heat shock, caloric restriction and preconditioning with different factors.

LIN28a induced metabolic and redox regulation promotes cardiac cell survival in the heart after ischemic injury

RATIONALE

Cell-based therapeutics have been extensively used for cardiac repair yet underperform due to inability of the donated cells to survive in near anoxia after cardiac injury. Cellular metabolism is linked to maintenance of cardiac stem cell (CSC) renewal, proliferation and survival. Ex vivo expansion alters (CSC) metabolism increasing reliance on oxygen dependent respiration. Whether promoting 'metabolic flexibility' in CSCs augments their ability to survive in near anoxia and repair the heart after injury remains untested.

OBJECTIVE

Determine the effect of LIN28a induced metabolic flexibility on cardiac tissue derived stem like cell (CTSC) survival and repair after cardiac injury.

METHODS AND RESULTS

LIN28a expression coincides during heart development but is lost in adult CTSCs. Reintroduction of LIN28a in adult CTSC (CTSC-LIN) increased proliferation, survival, expression of pluripotency genes and reduced senescence compared to control (CTSC-GFP). Metabolomic analysis show glycolytic intermediates upregulated in CTSC-LIN together with increased lactate production, pyruvate kinase activity, glucose uptake, ECAR and expression of glycolytic enzymes compared to CTSC-GFP. Additionally, CTSC-LIN showed significantly reduced ROS generation and increase antioxidant markers. In response to H2O2 induced oxidative stress, CTSC-LIN showed increased survival and expression of glycolytic genes. LIN28a salutary effects on CTSCs were linked to PDK1/let-7 signaling pathway with loss of PDK1 or alteration of let-7 abrogating LIN28a effects. Following transplantation in the heart after myocardial infarction (MI), CTSC-LIN showed 6% survival rate at day 7 after injection compared to control cells together with increased proliferation and significant increase in cardiac structure and function 8 weeks after MI. Finally, CSTC-LIN showed enhanced ability to secrete paracrine factors under hypoxic conditions and ability to promote cardiomyocyte proliferation following ischemic cardiac injury.

CONCLUSIONS

LIN28a modification promotes metabolic flexibility in CTSCs enhancing proliferation and survival post transplantation including ability to repair the heart after myocardial injury.

Modifying strategies for SDF-1/CXCR4 interaction during mesenchymal stem cell transplantation

Mesenchymal stem cell (MSC) transplantation is regarded as a promising candidate for the treatment of ischaemic heart disease. The major hurdles for successful clinical translation of MSC therapy are poor survival, retention, and engraftment in the infarcted heart. Stromal cell-derived factor-1/chemokine receptor 4 (SDF-1/CXCR4) constitutes one of the most efficient chemokine/chemokine receptor pairs regarding cell homing. In this review, we mainly focused on previous studies on how to regulate the SDF-1/CXCR4 interaction through various priming strategies to maximize the efficacy of mesenchymal stem cell transplantation on ischaemic hearts or to facilitate the required effects. The strengthened measures for enhancing the therapeutic efficacy of the SDF-1/CXCR4 interaction for mesenchymal stem cell transplantation included the combination of chemokines and cytokines, hormones and drugs, biomaterials, gene engineering, and hypoxia. The priming strategies on recipients for stem cell transplantation included ischaemic conditioning and device techniques.

The Effect of Inflammatory Priming on the Therapeutic Potential of Mesenchymal Stromal Cells for Spinal Cord Repair

Mesenchymal stromal cells (MSC) are used for cell therapy for spinal cord injury (SCI) because of their ability to support tissue repair by paracrine signaling. Preclinical and clinical research testing MSC transplants for SCI have revealed limited success, which warrants the exploration of strategies to improve their therapeutic efficacy. MSC are sensitive to the microenvironment and their secretome can be altered in vitro by exposure to different culture media. Priming MSC with inflammatory stimuli increases the expression and secretion of reparative molecules. We studied the effect of macrophage-derived inflammation priming on MSC transplants and of primed MSC (pMSC) acute transplants (3 days) on spinal cord repair using an adult rat model of moderate-severe contusive SCI. We found a decrease in long-term survival of pMSC transplants compared with unprimed MSC transplants. With a pMSC transplant, we found significantly more anti-inflammatory macrophages in the contusion at 4 weeks post transplantation (wpt). Blood vessel presence and maturation in the contusion at 1 wpt was similar in rats that received pMSC or untreated MSC. Nervous tissue sparing and functional recovery were similar across groups. Our results indicate that macrophage-derived inflammation priming does not increase the overall therapeutic potential of an MSC transplant in the adult rat contused spinal cord.

Stem Cell Therapy Potency in Personalizing Severe COVID-19 Treatment

Currently, there are no specific and efficient vaccines or drugs for COVID-19, particularly in severe cases. A wide range of variations in the clinical symptoms of different patients attributed to genomic differences. Therefore, personalized treatments seem to play a critical role in improving these symptoms and even similar conditions. Prompted by the uncertainties in the area of COVID-19 therapies, we reviewed the published papers and concepts to gather and provide useful information to clinicians and researchers interested in personalized medicine and cell-based therapy. One novel aspect of this study focuses on the potential application of personalized medicine in treating severe cases of COVID-19. However, it is theoretical, as any real-world examples of the use of genuinely personalized medicine have not existed yet. Nevertheless, we know that stem cells, especially MSCs, have immune-modulatory effects and can be stored for future personalized medicine applications. This theory has been conjugated with some evidence that we review in the present study. Besides, we discuss the importance of personalized medicine and its possible aspects in COVID-19 treatment, then review the cell-based therapy studies for COVID-19 with a particular focus on stem cell-based therapies as a primary personalized tool medicine. However, the idea of cell-based therapy has not been accepted by several scientific communities due to some concerns of lack of satisfactory clinical studies; still, the MSCs and their clinical outcomes have been revealed the safety and potency of this therapeutic approach in several diseases, especially in the immune-mediated inflammatory diseases and some incurable diseases. Promising outcomes have resulted in that clinical studies are going to continue.

Anti-fibrotic mechanisms of exogenously-expanded mesenchymal stromal cells for fibrotic diseases

Most chronic diseases involving inflammation have a fibrotic component that involves remodeling and excess accumulation of extracellular matrix components. Left unchecked, fibrosis leads to organ failure and death. Mesenchymal stromal cells (MSCs) are emerging as a potent cell-based therapy for a wide spectrum of fibrotic conditions due to their immunomodulatory, anti-inflammatory and anti-fibrotic properties. This review provides an overview of known mechanisms by which MSCs mediate their anti-fibrotic actions and in relation to animal models of pulmonary, liver, renal and cardiac fibrosis. Recent MSC clinical trials results in liver, lung, skin, kidney and hearts are discussed and next steps for future MSC-based therapies including pre-activated or genetically-modified cells, or extracellular vesicles are also considered.

Osteogenic differentiation of preconditioned bone marrow mesenchymal stem cells with lipopolysaccharide on modified poly-l-lactic-acid nanofibers

Tissue engineering is an interdisciplinary expertise that involves the use of nanoscaffolds for repairing, modifying, and removing tissue defects and formation of new tissues. Mesenchymal stem cells (MSCs) can differentiate into a variety of cell types, and they are attractive candidates for tissue engineering. In the current study, the electrospinning process was used for nanofiber preparation, based on a poly-l-lactic-acid (PLLA) polymer. The surface was treated with O ₂ plasma to enhance hydrophilicity, cell attachment, growth, and differentiation potential. The nanoscaffolds were preconditioned with lipopolysaccharide (LPS) to enhance induction of differentiation. The nanoscaffolds were categorized by contact angle measurements and scanning electron microscopy. The MTT assay was used to analyze the rate of growth and proliferation of cells. Osteogenic differentiation of cultured MSCs was evaluated on nanofibers using common osteogenic markers, such as alkaline phosphatase activity, calcium mineral deposition, quantitative real-time polymerase chain reaction, and immunocytochemical analysis. Based on the in vitro results, primed MSCs with LPS on the PLLA nanoscaffold significantly enhanced the proliferation and osteogenesis of MSCs. Also, the combination of LPS and electrospun nanofibers can provide a new and suitable matrix to support stem cells' differentiation for bone tissue engineering.

Cardiac mesenchymal cells from diabetic mice are ineffective for cell therapy-mediated myocardial repair

Although cell therapy improves cardiac function after myocardial infarction, highly variable results and limited understanding of the underlying mechanisms preclude its clinical translation. Because many heart failure patients are diabetic, we examined how diabetic conditions affect the characteristics of cardiac mesenchymal cells (CMC) and their ability to promote myocardial repair in mice. To examine how diabetes affects CMC function, we isolated CMCs from non-diabetic C57BL/6J (CMCWT) or diabetic B6.BKS(D)-Leprdb/J (CMCdb/db) mice. When CMCs were grown in 17.5 mM glucose, CMCdb/db cells showed > twofold higher glycolytic activity and a threefold higher expression of Pfkfb3 compared with CMCWT cells; however, culture of CMCdb/db cells in 5.5 mM glucose led to metabolic remodeling characterized by normalization of metabolism, a higher NAD+/NADH ratio, and a sixfold upregulation of Sirt1. These changes were associated with altered extracellular vesicle miRNA content as well as proliferation and cytotoxicity parameters comparable to CMCWT cells. To test whether this metabolic improvement of CMCdb/db cells renders them suitable for cell therapy, we cultured CMCWT or CMCdb/db cells in 5.5 mM glucose and then injected them into infarcted hearts of non-diabetic mice (CMCWT, n = 17; CMCdb/db, n = 13; Veh, n = 14). Hemodynamic measurements performed 35 days after transplantation showed that, despite normalization of their properties in vitro, and unlike CMCWT cells, CMCdb/db cells did not improve load-dependent and -independent parameters of left ventricular function. These results suggest that diabetes adversely affects the reparative capacity of CMCs and that modulating CMC characteristics via culture in lower glucose does not render them efficacious for cell therapy.

In vitro differentiated hepatic oval-like cells enhance hepatic regeneration in CCl4 -induced hepatic injury

Hepatic oval cells are likely to be activated during advanced stage of liver fibrosis to reconstruct damaged hepatic tissue. However, their scarcity, difficulties in isolation, and in vitro expansion hampered their transplantation in fibrotic liver. This study was aimed to investigate the repair potential of in vitro differentiated hepatic oval-like cells in CCl₄ -induced liver fibrosis. BMSCs and oval cells were isolated and characterized from C57BL/6 GFP⁺ mice. BMSCs were differentiated into oval cells by preconditioning with HGF, EGF, SCF, and LIF and analyzed for the oval cells-specific genes. Efficiency of oval cells to reduce hepatocyte injury was studied by determining cell viability, release of LDH, and biochemical tests in a co-culture system. Further, in vivo repair potential of differentiated oval cells was determined in CCl₄ -induced fibrotic model by gene expression analysis, biochemical tests, mason trichrome, and Sirius red staining. Differentiated oval cells expressed hepatic oval cells-specific markers AFP, ALB, CK8, CK18, CK19. These differentiated cells when co-cultured with injured hepatocytes showed significant hepato-protection as measured by reduction in apoptosis, LDH release, and improvement in liver functions. Transplantation of differentiated oval cells like cells in fibrotic livers exhibited enhanced homing, reduced liver fibrosis, and improved liver functions by augmenting hepatic microenvironment by improved liver functions. This preconditioning strategy to differentiate BMSCs into oval cell leads to improved survival and homing of transplanted cells. In addition, reduction in fibrosis and functional improvement in mice with CCl₄ -induced liver fibrosis was achieved.

The emerging role of Notch pathway in ageing: Focus on the related mechanisms in age-related diseases

Notch signaling is an evolutionarily conserved pathway, which is fundamental for the development of all tissues, organs and systems of human body. Recently, a considerable and still growing number of studies have highlighted the contribution of Notch signaling in various pathological processes of the adult life, such as age-related diseases. In particular, the Notch pathway has emerged as major player in the maintenance of tissue specific homeostasis, through the control of proliferation, migration, phenotypes and functions of tissue cells, as well as in the cross-talk between inflammatory cells and the innate immune system, and in onset of inflammatory age-related diseases. However, until now there is a confounding evidence about the related mechanisms. Here, we discuss mechanisms through which Notch signaling acts in a very complex network of pathways, where it seems to have the crucial role of hub. Thus, we stress the possibility to use Notch pathway, the related molecules and pathways constituting this network, both as innovative (predictive, diagnostic and prognostic) biomarkers and targets for personalised treatments for age-related diseases.

Isolation, expansion and differentiation of mesenchymal stromal cells from rabbits' bone marrow

Abstract: Tissue engineering has been a fundamental technique in the regenerative medicine field, once it permits to build tri-dimensional tissue constructs associating undifferentiated mesenchymal cells (or mesenchymal stromal cells - MSCs) and scaffolds in vitro. Therefore, many studies have been carried out using these cells from different animal species, and rabbits are often used as animal model for in vivo tissue repair studies. However, most of the information available about MSCs harvesting and characterization is about human and murine cells, which brings some doubts to researchers who desire to work with a rabbit model in tissue repair studies based on MSCs. In this context, this study aimed to add and improve the information available in the scientific literature providing a complete technique for isolation, expansion and differentiation of MSCs from rabbits. Bone marrow mononuclear cells (BMMCs) from humerus and femur of rabbits were obtained and to evaluate their proliferation rate, three different culture media were tested, here referred as DMEM-P, DMEM´S and α-MEM. The BMMCs were also cultured in osteogenic, chondrogenic and adipogenic induction media to prove their multipotentiality. It was concluded that the techniques suggested in this study can provide a guideline to harvest and isolate MSCs from bone marrow of rabbits in enough amount to allow their expansion and, based on the laboratory experience where the study was developed, it is also suggested a culture media formulation to provide a better cell proliferation rate with multipotentiality preservation.

Bone Marrow-Derived Stem Cells: a Mixed Blessing in the Multifaceted World of Diabetic Complications

Diabetes is one of the main economic burdens in health care, which threatens to worsen dramatically if prevalence forecasts are correct. What makes diabetes harmful is the multi-organ distribution of its microvascular and macrovascular complications. Regenerative medicine with cellular therapy could be the dam against life-threatening or life-altering complications. Bone marrow-derived stem cells are putative candidates to achieve this goal. Unfortunately, the bone marrow itself is affected by diabetes, as it can develop a microangiopathy and neuropathy similar to other body tissues. Neuropathy leads to impaired stem cell mobilization from marrow, the so-called mobilopathy. Here, we review the role of bone marrow-derived stem cells in diabetes: how they are affected by compromised bone marrow integrity, how they contribute to other diabetic complications, and how they can be used as a treatment for these. Eventually, we suggest new tactics to optimize stem cell therapy.

Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR

Throughout the globe, diabetes mellitus (DM) is increasing in incidence with limited therapies presently available to prevent or resolve the significant complications of this disorder. DM impacts multiple organs and affects all components of the central and peripheral nervous systems that can range from dementia to diabetic neuropathy. The mechanistic target of rapamycin (mTOR) is a promising agent for the development of novel regenerative strategies for the treatment of DM. mTOR and its related signaling pathways impact multiple metabolic parameters that include cellular metabolic homeostasis, insulin resistance, insulin secretion, stem cell proliferation and differentiation, pancreatic β-cell function, and programmed cell death with apoptosis and autophagy. mTOR is central element for the protein complexes mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) and is a critical component for a number of signaling pathways that involve phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), AMP activated protein kinase (AMPK), silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), Wnt1 inducible signaling pathway protein 1 (WISP1), and growth factors. As a result, mTOR represents an exciting target to offer new clinical avenues for the treatment of DM and the complications of this disease. Future studies directed to elucidate the delicate balance mTOR holds over cellular metabolism and the impact of its broad signaling pathways should foster the translation of these targets into effective clinical regimens for DM.

Density-Dependent Metabolic Heterogeneity in Human Mesenchymal Stem Cells

Human mesenchymal stem cells (hMSCs) are intrinsically heterogeneous and comprise subpopulations that differ in their proliferation, multi-potency, and functional properties, which are commonly demonstrated by culturing hMSCs at different plating densities. The objective of this study was to investigate the metabolic profiles of different subpopulations of hMSC by testing the hypothesis that the clonogenic hMSC subpopulation, which is selectively enriched in clonal density (CD) and low density (LD) culture (10 and 100 cells per square centimeter, respectively), possesses a metabolic phenotype that differs from that of hMSC in medium- or high-density (MD: 1,000 and HD: 3,000 cells per square centimeter, respectively). Cells at CD and LD conditions exhibited elevated expression of CD146 and colony forming unit-fibroblast compared with cells at MD- or HD. Global metabolic profiles revealed by gas chromatography-mass spectrometry of cell extracts showed clear distinction between LD and HD cultures, and density-dependent differences in coupling of glycolysis to the TCA cycle. Metabolic inhibitors revealed density-dependent differences in glycolysis versus oxidative phosphorylation (OXPHOS) for ATP generation, in glutamine metabolism, in the dependence on the pentose phosphate pathway for maintaining cellular redox state, and sensitivity to exogenous reactive oxygen species. We also show that active OXPHOS is not required for proliferation in LD culture but that OXPHOS activity increases senescence in HD culture. Together, the results revealed heterogeneity in hMSC culture exists at the level of primary metabolism. The unique metabolic characteristics of the clonogenic subpopulation suggest a novel approach for optimizing in vitro expansion of hMSCs.

The Effect of Age on Osteogenic and Adipogenic Differentiation Potential of Human Adipose Derived Stromal Stem Cells (hASCs) and the Impact of Stress Factors in the Course of the Differentiation Process

Human adipose tissue is a great source of autologous mesenchymal stem cells (hASCs), which are recognized for their vast therapeutic applications. Their ability to self-renew and differentiate into several lineages makes them a promising tool for cell-based therapies in different types of degenerative diseases. Thus it is crucial to evaluate age-related changes in hASCs, as the elderly are a group that will benefit most from their considerable potential. In this study we investigated the effect of donor age on growth kinetics, cellular senescence marker levels, and osteogenic and adipogenic potential of hASCs. It also has been known that, during life, organisms accumulate oxidative damage that negatively affects cell metabolism. Taking this into consideration, we evaluated the levels of nitric oxide, reactive oxygen species, and superoxide dismutase activity. We observed that ROS and NO increase with aging, while SOD activity is significantly reduced. Moreover cells obtained from older patients displayed senescence associated features, for example, β-galactosidase activity, enlarged morphology, and p53 protein upregulation. All of those characteristics seem to contribute to decreased proliferation potential of those cells. Our results suggest that due to aging some cellular modification may be required before applying aged cells efficiently in therapies such as tissue engineering and regenerative medicine.

Mesenchymal stem cells-based therapy as a potential treatment in neurodegenerative disorders: is the escape from senescence an answer?

Aging is the most prominent risk factor contributing to the development of neurodegenerative disorders. In the United States, over 35 million of elderly people suffer from age-related diseases. Aging impairs the self-repair ability of neuronal cells, which undergo progressive deterioration. Once initiated, this process hampers the already limited regenerative power of the central nervous system, making the search for new therapeutic strategies particularly difficult in elderly affected patients. So far, mesenchymal stem cells have proven to be a viable option to ameliorate certain aspects of neurodegeneration, as they possess high proliferative rate and differentiate in vitro into multiple lineages. However, accumulating data have demonstrated that during long-term culture, mesenchymal stem cells undergo spontaneous transformation. Transformed mesenchymal stem cells show typical features of senescence, including the progressive shortening of telomers, which results in cell loss and, as a consequence, hampered regenerative potential. These evidences, in line with those observed in mesenchymal stem cells isolated from old donors, suggest that senescence may represent a limit to mesenchymal stem cells exploitation in therapy, prompting scholars to either find alternative sources of pluripotent cells or to arrest the age-related transformation. In the present review, we summarize findings from recent literature, and critically discuss some of the major hurdles encountered in the search of appropriate sources of mesenchymal stem cells, as well as benefits arising from their use in neurodegenerative diseases. Finally, we provide some insights that may aid in the development of strategies to arrest or, at least, delay the aging of mesenchymal stem cells to improve their therapeutic potential.

New Insights for Oxidative Stress and Diabetes Mellitus

The release of reactive oxygen species (ROS) and the generation of oxidative stress are considered critical factors for the pathogenesis of diabetes mellitus (DM), a disorder that is growing in prevalence and results in significant economic loss. New therapeutic directions that address the detrimental effects of oxidative stress may be especially warranted to develop effective care for the millions of individuals that currently suffer from DM. The mechanistic target of rapamycin (mTOR), silent mating type information regulation 2 homolog 1 (S. cerevisiae) (SIRT1), and Wnt1 inducible signaling pathway protein 1 (WISP1) are especially justified to be considered treatment targets for DM since these pathways can address the complex relationship between stem cells, trophic factors, impaired glucose tolerance, programmed cell death pathways of apoptosis and autophagy, tissue remodeling, cellular energy homeostasis, and vascular biology that greatly impact the biology and disease progression of DM. The translation and development of these pathways into viable therapies will require detailed understanding of their proliferative nature to maximize clinical efficacy and limit adverse effects that have the potential to lead to unintended consequences.

Effect of mild heat stress on the proliferative and differentiative ability of human mesenchymal stromal cells

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are an attractive candidate for autologous cell therapy, but regenerative potential can be compromised with extensive in vitro cell passaging. Development of viable cell therapies must address the effect of in vitro passaging to maintain overall functionality of expanded MSCs.

METHODS

We examined the effect of repeated mild heat shock on the proliferation and differentiation capability of human adipose-derived MSCs. Adipose tissue MSCs were characterized by means of fluorescence activated cell sorting analysis for expression of CD3, CD14, CD19, CD34, CD44, CD45, CD73, CD90 and CD105. Similarly, the expression of SIRT-1, p16(INK4a) and p21 was determined by means of polymerase chain reaction. Measurements of population doubling, doubling time and superoxide dismutase activity were also determined. Differentiation of expanded MSCs into bone and adipose were analyzed qualitatively and quantitatively.

RESULTS

The strategy led to an increase in expression of SIRT-1 concomitant with enhanced viability, proliferation and delayed senescence. The stressed MSCs showed better differentiation into osteoblasts and adipocytes.

CONCLUSIONS

The results indicate that mild heat shock could be used to maintain MSC proliferative and differentiation potential.

SIRT1 and stem cells: In the forefront with cardiovascular disease, neurodegeneration and cancer

Cardiovascular disease, nervous system disorders, and cancer in association with other diseases such as diabetes mellitus result in greater than sixty percent of the global annual deaths. These noncommunicable diseases also affect at least one-third of the population in low and middle-income countries and lead to hypertension, elevated cholesterol, malignancy, and neurodegenerative disorders such as Alzheimer’s disease and stroke. With the climbing lifespan of the world’s population, increased prevalence of these disorders is expected requiring the development of new therapeutic strategies against these disabling disease entities. Targeting stem cell proliferation for cardiac disease, vascular disorders, cancer, and neurodegenerative disorders is receiving great enthusiasm, especially those that focus upon SIRT1, a mammalian homologue of the yeast silent information regulator-2. Modulation of the cellular activity of SIRT1 can involve oversight by nicotinamide/nicotinic acid mononucleotide adenylyltransferase, mammalian forkhead transcription factors, mechanistic of rapamycin pathways, and cysteine-rich protein 61, connective tissue growth factor, and nephroblastoma over-expressed gene family members that can impact cytoprotective outcomes. Ultimately, the ability of SIRT1 to control the programmed cell death pathways of apoptosis and autophagy can determine not only cardiac, vascular, and neuronal stem cell development and longevity, but also the onset of tumorigenesis and the resistance against chemotherapy. SIRT1 therefore has a critical role and holds exciting prospects for new therapeutic strategies that can offer reparative processes for cardiac, vascular, and nervous system degenerative disorders as well as targeted control of aberrant cell growth during cancer.

In vitro augmentation of mesenchymal stem cells viability in stressful microenvironments : In vitro augmentation of mesenchymal stem cells viability

Mesenchymal stem cells (MSCs) are under intensive investigation for use in cell-based therapies because their differentiation abilities, immunomodulatory effects, and homing properties offer potential for significantly augmenting regenerative capacity of many tissues. Nevertheless, major impediments to their therapeutic application, such as low proliferation and survival rates remain as obstacles to broad clinical use of MSCs. Another major challenge to evolution of MSC-based therapies is functional degradation of these cells as a result of their exposure to oxidative stressors during isolation. Indeed, oxidative stress-mediated MSC depletion occurs due to inflammatory processes associated with chemotherapy, radiotherapy, and expression of pro-apoptotic factors, and the microenvironment of damaged tissue in patients receiving MSC therapy is typically therapeutic not favorable to their survival. For this reason, any strategies that enhance the viability and proliferative capacity of MSCs associated with their therapeutic use are of great value. Here, recent strategies used by various researchers to improve MSC allograft function are reviewed, with particular focus on in vitro conditioning of MSCs in preparation for clinical application. Preconditioning, genetic manipulation, and optimization of MSC culture conditions are some examples of the methodologies described in the present article, along with novel strategies such as treatment of MSCs with secretome and MSC-derived microvesicles. This topic material is likely to find value as a guide for both research and clinical use of MSC allografts and for improvement of the value that use of these cells brings to health care.

Sirtuin function in aging heart and vessels

Age is the most important risk factor for metabolic alterations and cardiovascular accidents. Although class III histone deacetylases, alias Sirtuins, have been appealed as "the fountain of youth" their role in longevity control and prevention of aging-associated disease is still under debate. Indeed, several lines of evidence indicate that sirtuin activity is strictly linked to metabolism and dependent on NAD(+) synthesis both often altered as aging progresses. During aging the cardiovascular system is attacked by a variety of environmental stresses, including those determined by high blood glucose and lipid levels, or by the presence of oxidized lipoproteins which, among others, determine important oxidative stress signals. In such a milieu, heart and vessels develop a functional impairment leading to atherosclerosis, ischemia, heart insufficiency and failure. Sirtuins, which are believed to have a positive impact on cardiovascular physiology and physiopathology, are distributed in different subcellular compartments including the nucleus, the cytoplasm and the mitochondria, where they regulate expression and function of a large variety of target genes and proteins. Remarkably, experimental animal models indicate resveratrol, the first natural compound described to positively regulate the activity of sirtuins, as able to protect the endothelium and the heart exposed to a variety of stress agents. This review will focus on the regulation and function of mammalian sirtuins with special attention paid to their role as cardiovascular "defenders" giving indication of their targets of potential relevance for the development of future therapeutics. This article is part of a Special Issue entitled CV Aging.

Programming apoptosis and autophagy with novel approaches for diabetes mellitus

According to the World Health Organization, diabetes mellitus (DM) in the year 2030 will be ranked the seventh leading cause of death in the world. DM impacts all systems of the body with oxidant stress controlling cell fate through endoplasmic reticulum stress, mitochondrial dysfunction, alterations in uncoupling proteins, and the induction of apoptosis and autophagy. Multiple treatment approaches are being entertained for DM with Wnt1 inducible signaling pathway protein 1 (WISP1), mechanistic target of rapamycin (mTOR), and silent mating type information regulation 2 homolog) 1 (S. cerevisiae) (SIRT1) generating significant interest as target pathways that can address maintenance of glucose homeostasis as well as prevention of cellular pathology by controlling insulin resistance, stem cell proliferation, and the programmed cell death pathways of apoptosis and autophagy. WISP1, mTOR, and SIRT1 can rely upon similar pathways such as AMP activated protein kinase as well as govern cellular metabolism through cytokines such as EPO and oral hypoglycemics such as metformin. Yet, these pathways require precise biological control to exclude potentially detrimental clinical outcomes. Further elucidation of the ability to translate the roles of WISP1, mTOR, and SIRT1 into effective clinical avenues offers compelling prospects for new therapies against DM that can benefit hundreds of millions of individuals throughout the globe.

Subcutaneous Adipose Tissue-Derived Stem Cell Utility Is Independent of Anatomical Harvest Site

One of the challenges for tissue engineering and regenerative medicine is to obtain suitably large cell numbers for therapy. Mesenchymal stem cells (MSCs) can easily be expanded in vitro to obtain large numbers of cells, but this approach may induce cellular senescence. The characteristics of cells are dependent on variables like age, body mass index (BMI), and disease conditions, however, and in the case of adipose tissue-derived stem cells (ASCs), anatomical harvest site is also an important variable that can affect the regenerative potential of isolated cells. We therefore had kept the parameters (age, BMI, disease conditions) constant in this study to specifically assess influence of anatomical sites of individual donors on utility of ASCs. Adipose tissue was obtained from multiple anatomical sites in individual donors, and viability and nucleated cell yield were determined. MSC frequency was enumerated using colony forming unit assay and cells were characterized by flow cytometry. Growth characteristics were determined by long-term population doubling analysis of each sample. Finally, MSCs were induced to undergo adipogenic, osteogenic, and chondrogenic differentiation. To validate the findings, these results were compared with similar single harvest sites from multiple individual patients. The results of the current study indicated that MSCs obtained from multiple harvest sites in a single donor have similar morphology and phenotype. All adipose depots in a single donor exhibited similar MSC yield, viability, frequency, and growth characteristics. Equivalent differentiation capacity into osteocytes, adipocytes, and chondrocytes was also observed. On the basis of results, we conclude that it is acceptable to combine MSCs obtained from various anatomical locations in a single donor to obtain suitably large cell numbers required for therapy, avoiding in vitro senescence and lengthy and expensive in vitro culturing and expansion steps.

Metabolic regulation of mesenchymal stem cell in expansion and therapeutic application

Human mesenchymal or stromal cells (hMSCs) isolated from various adult tissues are primary candidates in cell therapy and tissue regeneration. Despite promising results in preclinical studies, robust therapeutic responses to MSC treatment have not been reproducibly demonstrated in clinical trials. In the translation of MSC-based therapy to clinical application, studies of MSC metabolism have significant implication in optimizing bioprocessing conditions to obtain therapeutically competent hMSC population for clinical application. In addition, understanding the contribution of metabolic cues in directing hMSC fate also provides avenues to potentiate their therapeutic effects by modulating their metabolic properties. This review focuses on MSC metabolism and discusses their unique metabolic features in the context of common metabolic properties shared by stem cells. Recent advances in the fundamental understanding of MSC metabolic characteristics in relation to their in vivo origin and metabolic regulation during proliferation, lineage-specific differentiation, and exposure to in vivo ischemic conditions are summarized. Metabolic strategies in directing MSC fate to enhance their therapeutic potential in tissue engineering and regenerative medicine are discussed.

Autologous serum improves bone formation in a primary stable silica-embedded nanohydroxyapatite bone substitute in combination with mesenchymal stem cells and rhBMP-2 in the sheep model

New therapeutic strategies are required for critical size bone defects, because the gold standard of transplanting autologous bone from an unharmed area of the body often leads to several severe side effects and disadvantages for the patient. For years, tissue engineering approaches have been seeking a stable, axially vascularized transplantable bone replacement suitable for transplantation into the recipient bed with pre-existing insufficient conditions. For this reason, the arteriovenous loop model was developed and various bone substitutes have been vascularized. However, it has not been possible thus far to engineer a primary stable and axially vascularized transplantable bone substitute. For that purpose, a primary stable silica-embedded nanohydroxyapatite (HA) bone substitute in combination with blood, bone marrow, expanded, or directly retransplanted mesenchymal stem cells, recombinant human bone morphogenetic protein 2 (rhBMP-2), and different carrier materials (fibrin, cell culture medium, autologous serum) was tested subcutaneously for 4 or 12 weeks in the sheep model. Autologous serum lead to an early matrix change during degradation of the bone substitute and formation of new bone tissue. The best results were achieved in the group combining mesenchymal stem cells expanded with 60 μg/mL rhBMP-2 in autologous serum. Better ingrowth of fibrovascular tissue could be detected in the autologous serum group compared with the control (fibrin). Osteoclastic activity indicating an active bone remodeling process was observed after 4 weeks, particularly in the group with autologous serum and after 12 weeks in every experimental group. This study clearly demonstrates the positive effects of autologous serum in combination with mesenchymal stem cells and rhBMP-2 on bone formation in a primary stable silica-embedded nano-HA bone grafting material in the sheep model. In further experiments, the results will be transferred to the sheep arteriovenous loop model in order to engineer an axially vascularized primary stable bone replacement in clinically relevant size for free transplantation.

ReNCell VM conditioned medium enhances the induction of dental pulp stem cells into dopaminergic like cells

Among the debilitating diseases, neurological related diseases are the most challenging ones to be treated using cell replacement therapies. Recently, dental pulp stem cells (SHED) were found to be most suitable cell choice for neurological related diseases as evidenced with many preclinical studies. To enhance the neurological potential of SHED, we recapitulated one of the pharmacological therapeutic tools in cell replacement treatment, we pre-conditioned dental pulp stem cells (SHED) with culture medium of ReNCell VM, an immortalized neuron progenitor cell, prior to neurogenesis induction and investigated whether this practice enhances their neurogenesis potential especially towards dopaminergic neurons. We hypothesed that the integration of pharmacological practices such as co-administration of various drugs, a wide range of doses and duration as well as pre-conditioning into cell replacement may enhance the efficacy of stem cell therapy. In particular, pre-conditioning is shown to be involved in the protective effect from some membrano-tropic drugs, thereby improving the resistance of cell structures and homing capabilities. We found that cells pre-treated with ReNCell VM conditioned medium displayed bipolar structures with extensive branches resembling putative dopaminergic neurons as compared to non-treated cells. Furthermore, many neuronal related markers such as NES, NR4A2, MSI1, and TH were highly expressed (fold changes > 2; p < 0.05) in pre-treated cells. Similar observations were detected at the protein level. The results demonstrate for the first time that SHED pre-conditioning enhances neurological potential and we suggest that cells should be primed to their respective environment prior to transplantation.

Preconditioning stem cells for in vivo delivery

Stem cells have emerged as promising tools for the treatment of incurable neural and heart diseases and tissue damage. However, the survival of transplanted stem cells is reported to be low, reducing their therapeutic effects. The major causes of poor survival of stem cells in vivo are linked to anoikis, potential immune rejection, and oxidative damage mediating apoptosis. This review investigates novel methods and potential molecular mechanisms for stem cell preconditioning in vitro to increase their retention after transplantation in damaged tissues. Microenvironmental preconditioning (e.g., hypoxia, heat shock, and exposure to oxidative stress), aggregate formation, and hydrogel encapsulation have been revealed as promising strategies to reduce cell apoptosis in vivo while maintaining biological functions of the cells. Moreover, this review seeks to identify methods of optimizing cell dose preparation to enhance stem cell survival and therapeutic function after transplantation.

Transplantation of SIRT1-engineered aged mesenchymal stem cells improves cardiac function in a rat myocardial infarction model

BACKGROUND

Previous studies have demonstrated that biological aging has a negative influence on the therapeutic effects of mesenchymal stem cells (MSCs)-based therapy. Using a rat myocardial infarction (MI) model, we tested the hypothesis that silent mating type information regulation 2 homolog 1 (SIRT1) may ameliorate the phenotype and improve the function of aged MSCs and thus enhance the efficacy of aged MSCs-based therapy.

METHODS

Sixty female rats underwent left anterior descending coronary artery ligation and were randomly assigned to receiving: intramyocardial injection of cell culture medium (DMEM group); SIRT1 overexpression vector-treated aged MSCs (SIRT1-aged MSCs group) obtained from aged male SD rats or empty vector-treated aged MSCs (vector-aged MSCs group). Another 20 sham-operated rats that underwent open-chest surgery without coronary ligation or any other intervention served as controls.

RESULTS

SIRT1-aged MSC group exhibited enhanced blood vessel density in the border zone of MI hearts, which was associated with reduced cardiac remodeling, leading to improved cardiac performance. Consistent with the in vivo data, our in vitro experiments also demonstrated that SIRT1 overexpression ameliorated aged MSCs senescent phenotype and recapitulated the pro-angiogenesis property of MSCs and conferred the anti-stress response capabilities, as indicated by increases in pro-angiogenic factors, angiopoietin 1 (Ang1) and basic fibroblast growth factor (bFGF), expressions and a decrease in anti-angiogenic factor thrombospondin-1 (TBS1) at mRNA levels, and increases in Bcl-2/Bax ratio at protein level.

CONCLUSIONS

Up-regulating SIRT1 expression could enhance the efficacy of aged MSCs-based therapy for MI as it relates to the amelioration of senescent phenotype and hence improved biological function of aged MSCs.

Influence of Egr-1 in cardiac tissue-derived mesenchymal stem cells in response to glucose variations

Mesenchymal stem cells (MSCs) represent a promising cell population for cell therapy and regenerative medicine applications. However, how variations in glucose are perceived by MSC pool is still unclear. Since, glucose metabolism is cell type and tissue dependent, this must be considered when MSCs are derived from alternative sources such as the heart. The zinc finger transcription factor Egr-1 is an important early response gene, likely to play a key role in the glucose-induced response. Our aim was to investigate how short-term changes in in vitro glucose concentrations affect multipotent cardiac tissue-derived MSCs (cMSCs) in a mouse model of Egr-1 KO (Egr-1^−/−). Results showed that loss of Egr-1 does not significantly influence cMSC proliferation. In contrast, responses to glucose variations were observed in wt but not in Egr-1^−/− cMSCs by clonogenic assay. Phenotype analysis by RT-PCR showed that cMSCs Egr-1^−/− lost the ability to regulate the glucose transporters GLUT-1 and GLUT-4 and, as expected, the Egr-1 target genes VEGF, TGFβ-1, and p300. Acetylated protein levels of H3 histone were impaired in Egr-1^−/− compared to wt cMSCs. We propose that Egr-1 acts as immediate glucose biological sensor in cMSCs after a short period of stimuli, likely inducing epigenetic modifications.

Cryopreservation of whole adipose tissue for future use in regenerative medicine

BACKGROUND

Human adipose tissue (AT) is an ideal stem cell source for autologous cell-based therapies. The preferred setting for tissue engineering and regenerative medicine applications is the availability of clinically acceptable off-the-shelf cells and cell products. As AT is not always available for use, cryopreserved tissue represents an alternative approach. The aim of the present study was to compare the different properties of mesenchymal stem cells (MSCs) isolated from cryopreserved AT. We have measured cell recovery, viability, phenotype, proliferative potential, and differentiation into mesenchymal (adipogenic, osteogenic, chondrogenic) and nonmesenchymal (neuron-like cells) lineages.

MATERIALS AND METHODS

AT (n = 10) was harvested from donors and either processed fresh or cryopreserved in liquid nitrogen dewars. Both fresh and thawed tissues were enzymatically digested. MSCs were analyzed by fluorescence-activated cell sorting for CD3, CD14, CD19, CD34, CD44, CD45, CD73, CD90, and CD105 expression. Growth characteristics of both groups were investigated for population doublings, doubling time, saturation density, and plating efficiency. MSCs derived from fresh and thawed tissues were assessed for differentiation potential both qualitatively and quantitatively.

RESULTS

Adherent cells from fresh and thawed tissues displayed similar fibroblastic morphology. Cryopreservation did not alter expression of phenotypic markers. Similarly, the proliferative potential of MSCs was not compromised by cryopreservation. Furthermore, cryopreservation did not alter the differentiation capability of MSCs as determined with histochemistry, immunofluorescence, and real time reverse transcriptase-polymerase chain reaction.

CONCLUSIONS

We conclude that human AT could be successfully cryopreserved for future clinical application and the recovered MSCs were equivalent in functionality to the freshly processed MSCs.

Stem Cell Banking for Regenerative and Personalized Medicine

Regenerative medicine, tissue engineering and gene therapy offer the opportunity to treat and cure many of today’s intractable afflictions. These approaches to personalized medicine often utilize stem cells to accomplish these goals. However, stem cells can be negatively affected by donor variables such as age and health status at the time of collection, compromising their efficacy. Stem cell banking offers the opportunity to cryogenically preserve stem cells at their most potent state for later use in these applications. Practical stem cell sources include bone marrow, umbilical cord blood and tissue, and adipose tissue. Each of these sources contains stem cells that can be obtained from most individuals, without too much difficulty and in an economical fashion. This review will discuss the advantages and disadvantages of each stem cell source, factors to be considered when contemplating banking each stem cell source, the methodology required to bank each stem cell source, and finally, current and future clinical uses of each stem cell source.

Mesenchymal stromal cells for organ transplantation: different sources and unique characteristics?

PURPOSE OF THE REVIEW

In this review, recent findings on the effects of tissue and donor origin, culturing conditions and preconditioning regimens on the therapeutic effect of mesenchymal stem cells (MSC) in organ transplantation are discussed and the importance of understanding the characteristics of MSC for developing efficient therapy is stressed.

RECENT FINDINGS

MSC research in organ transplantation is currently moving from safety-feasibility studies to efficacy studies and finding the optimal MSC for therapy is therefore highly relevant. Although sharing basic properties, there are subtle differences between MSC from different tissue sources that may affect their efficacy. Furthermore, the use of MSC from diseased organ recipients, donor or third party may affect their therapeutic effect. The importance of these differences in MSC properties may however be overshadowed by the impact of culture conditions on MSC. Culture conditions dramatically change the characteristics of MSC, and this situation can be exploited by exposing MSC to preconditioning treatment to bring about the desired properties in MSC. As MSC appear to be short-lived after infusion, the specific characteristics of MSC are mostly relevant for short-term interactions between MSC and host cells, which will subsequently take over the effects of MSC. The multiple effects of MSC are by no means unique, but the full spectrum of the effects in combination with their easy isolation and expansion make MSC a suitable cell type for therapy.

SUMMARY

Tissue source, donor source and culture conditions affect the phenotypical and functional properties of MSC. The efficacy of MSC therapy will therefore depend on the source and manipulation of MSC.

Donor age negatively impacts adipose tissue-derived mesenchymal stem cell expansion and differentiation

BACKGROUND

Human adipose tissue is an ideal autologous source of mesenchymal stem cells (MSCs) for various regenerative medicine and tissue engineering strategies. Aged patients are one of the primary target populations for many promising applications. It has long been known that advanced age is negatively correlated with an organism's reparative and regenerative potential, but little and conflicting information is available about the effects of age on the quality of human adipose tissue derived MSCs (hAT-MSCs).

METHODS

To study the influence of age, the expansion and in vitro differentiation potential of hAT-MSCs from young (<30 years), adult (35-50 years) and aged (>60 years) individuals were investigated. MSCs were characterized for expression of the genes p16(INK4a) and p21 along with measurements of population doublings (PD), superoxide dismutase (SOD) activity, cellular senescence and differentiation potential.

RESULTS

Aged MSCs displayed senescent features when compared with cells isolated from young donors, concomitant with reduced viability and proliferation. These features were also associated with significantly reduced differentiation potential in aged MSCs compared to young MSCs.

CONCLUSIONS

In conclusion, advancing age negatively impacts stem cell function and such age related alterations may be detrimental for successful stem cell therapies.

Combination of BMP-2 and 5-AZA is advantageous in rat bone marrow-derived mesenchymal stem cells differentiation into cardiomyocytes

Bone morphogenetic protein-2 (BMP-2) has a crucial role in the development of cardiogenesis, and is used in inducing bone marrow mesenchymal stem cells (BMMSCs) to differentiate into cardiomyocytes. We have examined a combination of BMP-2 and 5-azacytidine (5-AZA) in inducing these differentiation effects. BMMSCs were collected and purified from bone marrow of 4-week-old Sprague-Dawley (SD) rats by density-gradient centrifugation and differential attachment. The fourth passage subculture of BMMSCs, selected by cytometry for purity and identification, was divided into four groups: a control group, BMP-2 treated, 5-AZA treated, and a combination of BMP-2 and 5-AZA treatment. Expression of cardiac Troponin I (cTnI) and Connexin 43 (CX-43) in BMMSCs after induction were detected by immunofluorescence and Western blot. Flow cytometry analysis was used for differentiation rates and apoptosis of induced BMMSCs, through the expression of cardiac Troponin T (cTnT) and Annexin V-FITC & PI kit, respectively. BMP-2 can ameliorate apoptosis of BMMSCs caused by 5-AZA and promote the differentiation of BMMSCs into cardiomyocyte-like cells. Thus a combination of BMP-2 and 5-AZA can significantly improve the cardiac differentiation with fewer cell damage effects, making it a safe and effective method of induction in vitro.

Nanofiber for cardiovascular tissue engineering

INTRODUCTION

Organ/tissue replacement therapy is inherently difficult for application in the tissue engineering field due to immune rejection that limits the long-term efficacy of implanted devices. As the application of tissue engineering in the biomedical field has steadily expanded, stem cells have emerged as a viable option to promote the immune acceptance of implantable devices and to expedite alleviation of the pathological conditions. With various novel scaffolds being introduced, nanofibers which have a three-dimensional architecture can be considered as an efficient carrier for stem cells.

AREAS COVERED

This article reviews the novel tissue engineering processes involved with nanofiber and stem cells. Topics such as the fabrication of nanofiber via electrospinning techniques, the interaction between nanofiber scaffold and specific cell and advanced techniques to enhance the stability of stem cells are delineated in detail. In addition, cardiovascular applications of nanofiber scaffolds loaded with stem cells are examined from a clinical perspective.

EXPERT OPINION

Electrospun nanofibers have been intensively explored as a tool for the architecture control of cardiovascular tissue engineering due to their tunable physicochemical properties. The modification of nanofiber with biological cues, which provide rapid differentiation of stem cells into a specific lineage and protect stem cells under the harsh conditions (i.e., hypoxia), will significantly enhance therapeutic efficacies of transplanted cells. A combination of nanofiber carriers and stem cell therapy for tissue regeneration seems to pose enormous potential for the treatment of cardiac diseases including atherosclerosis and myocardial infarction.

Rejuvenation of human cardiac progenitor cells with Pim-1 kinase

RATIONALE

Myocardial function is enhanced by adoptive transfer of human cardiac progenitor cells (hCPCs) into a pathologically challenged heart. However, advanced age, comorbidities, and myocardial injury in patients with heart failure constrain the proliferation, survival, and regenerative capacity of hCPCs. Rejuvenation of senescent hCPCs will improve the outcome of regenerative therapy for a substantial patient population possessing functionally impaired stem cells.

OBJECTIVE

Reverse phenotypic and functional senescence of hCPCs by ex vivo modification with Pim-1.

METHODS AND RESULTS

C-kit-positive hCPCs were isolated from heart biopsy samples of patients undergoing left ventricular assist device implantation. Growth kinetics, telomere lengths, and expression of cell cycle regulators showed significant variation between hCPC isolated from multiple patients. Telomere length was significantly decreased in hCPC with slow-growth kinetics concomitant with decreased proliferation and upregulation of senescent markers compared with hCPC with fast-growth kinetics. Desirable youthful characteristics were conferred on hCPCs by genetic modification using Pim-1 kinase, including increases in proliferation, telomere length, survival, and decreased expression of senescence markers.

CONCLUSIONS

Senescence characteristics of hCPCs are ameliorated by Pim-1 kinase resulting in rejuvenation of phenotypic and functional properties. hCPCs show improved cellular properties resulting from Pim-1 modification, but benefits were more pronounced in hCPC with slow-growth kinetics relative to hCPC with fast-growth kinetics. With the majority of patients with heart failure presenting advanced age, infirmity, and impaired regenerative capacity, the use of Pim-1 modification should be incorporated into cell-based therapeutic approaches to broaden inclusion criteria and address limitations associated with the senescent phenotype of aged hCPC.

Cell adhesion and mechanical stimulation in the regulation of mesenchymal stem cell differentiation

Stem cells have been shown to have the potential to provide a source of cells for applications to tissue engineering and organ repair. The mechanisms that regulate stem cell fate, however, mostly remain unclear. Mesenchymal stem cells (MSCs) are multipotent progenitor cells that are isolated from bone marrow and other adult tissues, and can be differentiated into multiple cell lineages, such as bone, cartilage, fat, muscles and neurons. Although previous studies have focused intensively on the effects of chemical signals that regulate MSC commitment, the effects of physical/mechanical cues of the microenvironment on MSC fate determination have long been neglected. However, several studies provided evidence that mechanical signals, both direct and indirect, played important roles in regulating a stem cell fate. In this review, we summarize a number of recent studies on how cell adhesion and mechanical cues influence the differentiation of MSCs into specific lineages. Understanding how chemical and mechanical cues in the microenvironment orchestrate stem cell differentiation may provide new insights into ways to improve our techniques in cell therapy and organ repair.

Preconditioning diabetic mesenchymal stem cells with myogenic medium increases their ability to repair diabetic heart

INTRODUCTION

Mesenchymal stem cells (MSCs) have the potential for treatment of diabetic cardiomyopathy; however, the repair capability of MSCs declines with age and disease. MSCs from diabetic animals exhibit impaired survival, proliferation, and differentiation and therefore require a strategy to improve their function. The aim of the study was to develop a preconditioning strategy to augment the ability of MSCs from diabetes patients to repair the diabetic heart.

METHODS

Diabetes was induced in C57BL/6 mice (6 to 8 weeks) with streptozotocin injections (55 mg/kg) for 5 consecutive days. MSCs isolated from diabetic animals were preconditioned with medium from cardiomyocytes exposed to oxidative stress and high glucose (HG/H-CCM).

RESULTS

Gene expression of VEGF, ANG-1, GATA-4, NKx2.5 MEF2c, PCNA, and eNOS was upregulated after preconditioning with HG/H-CCM, as evidenced by reverse transcriptase/polymerase chain reaction (RT-PCR). Concurrently, increased AKT phosphorylation, proliferation, angiogenic ability, and reduced levels of apoptosis were observed in HG/H-CCM-preconditioned diabetic MSCs compared with nontreated controls. HG/H-CCM-preconditioned diabetic-mouse-derived MSCs (dmMSCs) were transplanted in diabetic animals and demonstrated increased homing concomitant with augmented heart function. Gene expression of angiogenic and cardiac markers was significantly upregulated in conjunction with paracrine factors (IGF-1, HGF, SDF-1, FGF-2) and, in addition, reduced fibrosis, apoptosis, and increased angiogenesis was observed in diabetic hearts 4 weeks after transplantation of preconditioned dmMSCs compared with hearts with nontreated diabetic MSCs.

CONCLUSIONS

Preconditioning with HG/H-CCM enhances survival, proliferation, and the angiogenic ability of dmMSCs, augmenting their ability to improve function in a diabetic heart.