Autologous bone-marrow stem-cell transplantation for myocardial regeneration

Advanced cell and gene therapies in cardiology

We review the evidence for the presence of stem/progenitor cells in the heart and the preclinical and clinical data using diverse cell types for the therapy of cardiac diseases. We highlight the failure of adult stem/progenitor cells to ameliorate heart function in most cardiac diseases, with the possible exception of refractory angina. The use of pluripotent stem cell-derived cardiomyocytes is analysed as a viable alternative therapeutic option but still needs further research at preclinical and clinical stages. We also discuss the use of direct reprogramming of cardiac fibroblasts into cardiomyocytes and the use of extracellular vesicles as therapeutic agents in ischemic and non-ischemic cardiac diseases. Finally, gene therapies and genome editing for the treatment of hereditary cardiac diseases, ablation of genes responsible for atherosclerotic disease, or modulation of gene expression in the heart are discussed.

Human Cord Blood Endothelial Progenitor Cells and Pregnancy Complications (Preeclampsia, Gestational Diabetes Mellitus, and Fetal Growth Restriction)

Hemangioblasts give rise to endothelial progenitor cells (EPCs), which also express the cell surface markers CD133 and c-kit. They may differentiate into the outgrowth endothelial cells (OECs) that control neovascularization in the developing embryo. According to numerous studies, reduced levels of EPCs in circulation have been linked to human cardiovascular disorders. Furthermore, preeclampsia and senescence have been linked to levels of EPCs produced from cord blood. Uncertainties surround how preeclampsia affects the way EPCs function. It is reasonable to speculate that preeclampsia may have an impact on the function of fetal EPCs during the in utero period; however, the present literature suggests that maternal vasculopathies, including preeclampsia, damage fetal circulation. Additionally, the differentiation potential and general activity of EPCs may serve as an indicator of the health of the fetal vascular system as they promote neovascularization and repair during pregnancy. Thus, the purpose of this review is to compare-through the assessment of their quantity, differentiation potency, angiogenic activity, and senescence-the angiogenic function of fetal EPCs obtained from cord blood for normal and pregnancy problems (preeclampsia, gestational diabetes mellitus, and fetal growth restriction). This will shed light on the relationship between the angiogenic function of fetal EPCs and pregnancy complications, which could have an effect on the management of long-term health issues like metabolic and cardiovascular disorders in offspring with abnormal vasculature development.

Cardiomyocyte precursors generated by direct reprogramming and molecular beacon selection attenuate ventricular remodeling after experimental myocardial infarction

BACKGROUND

Direct cardiac reprogramming is currently being investigated for the generation of cells with a true cardiomyocyte (CM) phenotype. Based on the original approach of cardiac transcription factor-induced reprogramming of fibroblasts into CM-like cells, various modifications of that strategy have been developed. However, they uniformly suffer from poor reprogramming efficacy and a lack of translational tools for target cell expansion and purification. Therefore, our group has developed a unique approach to generate proliferative cells with a pre-CM phenotype that can be expanded in vitro to yield substantial cell doses.

METHODS

Cardiac fibroblasts were reprogrammed toward CM fate using lentiviral transduction of cardiac transcriptions factors (GATA4, MEF2C, TBX5, and MYOCD). The resulting cellular phenotype was analyzed by RNA sequencing and immunocytology. Live target cells were purified based on intracellular CM marker expression using molecular beacon technology and fluorescence-activated cell sorting. CM commitment was assessed using 5-azacytidine-based differentiation assays and the therapeutic effect was evaluated in a mouse model of acute myocardial infarction using echocardiography and histology. The cellular secretome was analyzed using mass spectrometry.

RESULTS

We found that proliferative CM precursor-like cells were part of the phenotype spectrum arising during direct reprogramming of fibroblasts toward CMs. These induced CM precursors (iCMPs) expressed CPC- and CM-specific proteins and were selectable via hairpin-shaped oligonucleotide hybridization probes targeting Myh6/7-mRNA-expressing cells. After purification, iCMPs were capable of extensive expansion, with preserved phenotype when under ascorbic acid supplementation, and gave rise to CM-like cells with organized sarcomeres in differentiation assays. When transplanted into infarcted mouse hearts, iCMPs prevented CM loss, attenuated fibrotic scarring, and preserved ventricular function, which can in part be attributed to their substantial secretion of factors with documented beneficial effect on cardiac repair.

CONCLUSIONS

Fibroblast reprogramming combined with molecular beacon-based cell selection yields an iCMP-like cell population with cardioprotective potential. Further studies are needed to elucidate mechanism-of-action and translational potential.

Cells and Materials for Cardiac Repair and Regeneration

After more than 20 years following the introduction of regenerative medicine to address the problem of cardiac diseases, still questions arise as to the best cell types and materials to use to obtain effective clinical translation. Now that it is definitively clear that the heart does not have a consistent reservoir of stem cells that could give rise to new myocytes, and that there are cells that could contribute, at most, with their pro-angiogenic or immunomodulatory potential, there is fierce debate on what will emerge as the winning strategy. In this regard, new developments in somatic cells' reprogramming, material science and cell biophysics may be of help, not only for protecting the heart from the deleterious consequences of aging, ischemia and metabolic disorders, but also to boost an endogenous regeneration potential that seems to be lost in the adulthood of the human heart.

Image-based cell sorting using focused travelling surface acoustic waves

Sorting cells is an essential primary step in many biological and clinical applications such as high-throughput drug screening, cancer research and cell transplantation. Cell sorting based on their mechanical properties has long been considered as a promising label-free biomarker that could revolutionize the isolation of cells from heterogeneous populations. Recent advances in microfluidic image-based cell analysis combined with subsequent label-free sorting by on-chip actuators demonstrated the possibility of sorting cells based on their physical properties. However, the high purity of sorting is achieved at the expense of a sorting rate that lags behind the analysis throughput. Furthermore, stable and reliable system operation is an important feature in enabling the sorting of small cell fractions from a concentrated heterogeneous population. Here, we present a label-free cell sorting method, based on the use of focused travelling surface acoustic wave (FTSAW) in combination with real-time deformability cytometry (RT-DC). We demonstrate the flexibility and applicability of the method by sorting distinct blood cell types, cell lines and particles based on different physical parameters. Finally, we present a new strategy to sort cells based on their mechanical properties. Our system enables the sorting of up to 400 particles per s. Sorting is therefore possible at high cell concentrations (up to 36 million per ml) while retaining high purity (>92%) for cells with diverse sizes and mechanical properties moving in a highly viscous buffer. Sorting of small cell fraction from a heterogeneous population prepared by processing of small sample volume (10 μl) is also possible and here demonstrated by the 667-fold enrichment of white blood cells (WBCs) from raw diluted whole blood in a continuous 10-hour sorting experiment. The real-time analysis of multiple parameters together with the high sensitivity and high-throughput of our method thus enables new biological and therapeutic applications in the future.

Intracoronary transplantation of pluripotent stem cell-derived cardiomyocytes: Inefficient procedure for cardiac regeneration

Advances in stem cell biology have facilitated cardiac regeneration, and many animal studies and several initial clinical trials have been conducted using human pluripotent stem cell-derived cardiomyocytes (PSC-CMs). Most preclinical and clinical studies have typically transplanted PSC-CMs via the following two distinct approaches: direct intramyocardial injection or epicardial delivery of engineered heart tissue. Both approaches present common disadvantages, including a mandatory thoracotomy and poor engraftment. Furthermore, a standard transplantation approach has yet to be established. In this study, we tested the feasibility of performing intracoronary administration of PSC-CMs based on a commonly used method of transplanting somatic stem cells. Six male cynomolgus monkeys underwent intracoronary administration of dispersed human PSC-CMs or PSC-CM aggregates, which are called cardiac spheroids, with multiple cell dosages. The recipient animals were sacrificed at 4 weeks post-transplantation for histological analysis. Intracoronary administration of dispersed human PSC-CMs in the cynomolgus monkeys did not lead to coronary embolism or graft survival. Although the transplanted cardiac spheroids became partially engrafted, they also induced scar formation due to cardiac ischemic injury. Cardiac engraftment and scar formation were reasonably consistent with the spheroid size or cell dosage. These findings indicate that intracoronary transplantation of PSC-CMs is an inefficient therapeutic approach.

Roles of TRPV4 in Regulating Circulating Angiogenic Cells to Promote Coronary Microvascular Regeneration

To clarify the mechanisms underlying TRPV4 regulating angiogenesis by enhancing the activity of CACs, we detected the angiogenesis ability of HUVEC co-cultured with CACs, the effects of ILK on TRPV4 expression and CACs activity, and the impacts of TRPV4 agonist or inhibitor on cardio-protection of AMI rats with or without CAC transplantation. ILK overexpression or TRPV4 agonist promoted the angiogenesis in HUVEC co-cultured with CACs. ILK overexpression or activation upregulated TRPV4 expression in CACs, while TRPV4 agonist stimulation also regulated ILK expression. TRPV4 agonist effectively improved the myocardial function of AMI rats. Moreover, this effect could be strengthened when combined with CAC transplantation, as CAC transplantation dramatically upregulated the expression of ILK and TRPV4 in heart tissues of AMI rats. Thus, the application of TRPV4 agonist may maintain the activity of CACs to promote angiogenesis and microcirculation reconstruction in the area of myocardial infarction and substantially improve the therapeutic effect.

In Vivo Multimodal Imaging of Stem Cells Using Nanohybrid Particles Incorporating Quantum Dots and Magnetic Nanoparticles

The diagnosis of the dynamics, accumulation, and engraftment of transplanted stem cells in vivo is essential for ensuring the safety and the maximum therapeutic effect of regenerative medicine. However, in vivo imaging technologies for detecting transplanted stem cells are not sufficient at present. We developed nanohybrid particles composed of dendron-baring lipids having two unsaturated bonds (DLU2) molecules, quantum dots (QDs), and magnetic nanoparticles in order to diagnose the dynamics, accumulation, and engraftment of transplanted stem cells, and then addressed the labeling and in vivo fluorescence and magnetic resonance (MR) imaging of stem cells using the nanohybrid particles (DLU2-NPs). Five kinds of DLU2-NPs (DLU2-NPs-1-5) composed of different concentrations of DLU2 molecules, QDs525, QDs605, QDs705, and ATDM were prepared. Adipose tissue-derived stem cells (ASCs) were labeled with DLU2-NPs for 4 h incubation, no cytotoxicity or marked effect on the proliferation ability was observed in ASCs labeled with DLU2-NPs (640- or 320-fold diluted). ASCs labeled with DLU2-NPs (640-fold diluted) were transplanted subcutaneously onto the backs of mice, and the labeled ASCs could be imaged with good contrast using in vivo fluorescence and an MR imaging system. DLU2-NPs may be useful for in vivo multimodal imaging of transplanted stem cells.

The Progress of Stem Cell Therapy in Myocardial-Infarcted Heart Regeneration: Cell Sheet Technology

Various tissues, including the heart, cornea, bone, esophagus, bladder and liver, have been vascularized using the cell sheet technique. It overcomes the limitations of existing techniques by allowing small layers of the cell sheet to generate capillaries on their own, and it can also be used to vascularize tissue-engineered transplants. Cell sheets eliminate the need for traditional tissue engineering procedures such as isolated cell injections and scaffold-based technologies, which have limited applicability. While cell sheet engineering can eliminate many of the drawbacks, there are still a few challenges that need to be addressed. The number of cell sheets that can be layered without triggering core ischemia or hypoxia is limited. Even when scaffold-based technologies are disregarded, strategies to tackle this problem remain a substantial impediment to the efficient regeneration of thick, living three-dimensional cell sheets. In this review, we summarize the cell sheet technology in myocardial infarcted tissue regeneration.

Endothelial Progenitor Cells as Biomarkers of Cardiovascular Pathologies: A Narrative Review

Endothelial progenitor cells (EPC) may influence the integrity and stability of the vascular endothelium. The association of an altered total EPC number and function with cardiovascular diseases (CVD) and risk factors (CVF) was discussed; however, their role and applicability as biomarkers for clinical purposes have not yet been defined. Endothelial dysfunction is one of the key mechanisms in CVD. The assessment of endothelial dysfunction in vivo remains a major challenge, especially for a clinical evaluation of the need for therapeutic interventions or for primary prevention of CVD. One of the main challenges is the heterogeneity of this particular cell population. Endothelial cells (EC) can become senescent, and the majority of circulating endothelial cells (CEC) show evidence of apoptosis or necrosis. There are a few viable CECs that have properties similar to those of an endothelial progenitor cell. To use EPC levels as a biomarker for vascular function and cumulative cardiovascular risk, a correct definition of their phenotype, as well as an update on the clinical application and practicability of current isolation methods, are an urgent priority.

LPS-pretreated MSC-conditioned medium optimized with 10-kDa filter attenuates the injury of H9c2 cardiomyocytes in a model of hypoxia/reoxygenation

Mesenchymal stem cell-derived conditioned medium (MSC-CM) improves cardiac function, which is partly attributed to released paracrine factors. Since such cardioprotection is moderate and transient, it's essential to optimize MSC-CM effective components to alleviate myocardial injury. To optimize MSC-CM, MSCs were treated with or without lipopolysaccharides (LPSs) for 48 h (serum-free), and the supernatant was collected. Then, LPS-CM (MSC stimulated by LPS) was further treated with LPS remover (LPS Re-CM) or was concentrated with a 10-kDa cutoff filter (10 kDa-CM). ELISA showed that all pretreatments increased levels of VEGF, HGF, and IGF except LPS remover; 10 kDa-CM was superior to other-CM. CCK-8 displayed that viability of injured H9c2 cells enhanced with the increase of MSC-CM concentration. We also found 10 kDa-CM significantly alleviated H9c2 hypoxia/reoxygenation (H/R) injury, as evidenced by increased Bcl-2/Bax ratio, decreased the levels of LDH and cTn. TEM, TUNEL, and H&E staining confirmed 10 kDa-CM inhibited H/R-induced H9c2 morphological changes. Proteomic analysis identified 41 differentially expressed proteins in 10 kDa-CM, among which anti-inflammation, pro-angiogenesis, and anti-apoptosis were related to cardiac protection. This study indicates that 10 kDa-CM protects H9c2 cardiomyocytes from H/R injury by preserving most of the protective factors, such as VEGF, HGF, and IGF, in MSC-CM.

Thematic trend mapping and hotspot analysis in bone marrow aspirate concentrate therapy: A scientometric literature analysis and advances in osteoarthritis

Bone marrow aspirate concentrate (BMAC) therapy has been spotlighted as a promising regenerative tool with its abundant source of mesenchymal stromal cells (MSCs) and growth factors. The spectrum of the utility of BMAC therapy has been expanding day by day to harness the potential for varied therapeutic purposes. In the due course of its evolution, it is often essential to have a comprehensive summary of progress to have a greater understanding and refine our future directives. With technological developments such as data mining, graphic drawing and information analytics combined with computational statistics, visualization of scientific metrology has become a reality. With this newer perspective, we intend to use scientometric tools including text mining, cocitation analysis, keyword analysis and cluster network analysis to perform thematic trend mapping and hotspot analysis of the literature on BMAC therapy and evaluate its progress in the management of osteoarthritis.

Kardiale Zelltherapie – „lost in translation?“

Die kardiale Zelltherapie hat über zwei Dekaden bewegter Geschichte hinter sich, in denen sich die Wahrnehmung des Herzens als Organ, bestehend aus einer fixierten Zahl terminal differenzierter Kardiomyozyten, fundamental geändert hat. Plötzlich galt bzw. gilt das Myokard als regenerierbar – durch intrinsische Vorläuferzellen, induzierbare Proliferation, aber v. a. durch exogene, transplantierte Zellen. Während die klinische Translation echter Kardiomyozyten, gewonnen durch zelluläre Reprogrammierung, nur langsam vorankommt, wurde eine Vielzahl klinischer Studien mit Zellprodukten somatischen Ursprungs durchgeführt. Diese beruhten zumeist auf Annahmen bzw. experimentell erhobenen Daten bezüglich der Plastizität adulter Vorläuferzellen, die sich im Nachhinein als nichthaltbar erwiesen haben. Dementsprechend waren auch der Ergebnisse der klinischen Studien bei genauer Betrachtung wenig überzeugend, wurden jedoch trotzdem oft ausgesprochen optimistisch dargestellt. Mittlerweile gilt die kardiale Zelltherapie mit Zellen somatischen Ursprungs als gescheitert. Die Etappen dieser Ära zu rekapitulieren, kann helfen, derartige Fehlentwicklungen in Zukunft frühzeitig zu erkennen und zu verhindern.

A chitosan-vitamin C based injectable hydrogel improves cell survival under oxidative stress

Stem cell transplantation technology provides the cell reconstruction of damaged heart a completely new therapy approach. Due to the inappropriate microenvironment such as reactive oxygen radicals caused by ischemic infarct, the survival and retention rates of cell transplantation are not desirable. A thermo sensitive chitosan-vitamin C (CSVC) hydrogel scaffold was developed to reduce oxidative stress injury after myocardial infarction, thereby increasing the cell survival rate of cell transplantation. Vitamin C was conjugated on the chitosan chain by electrostatic adsorption. Compared to chitosan, CSVC complex had a higher solubility and stronger antioxidant property. CSVC hydrogel has suitable gelation time and injectable properties. Scanning electron microscopy showed that chitosan hydrogels had three-dimensional porous structure with irregular pores interconnected throughout the construct. Live/dead and H&E staining results showed that CSVC hydrogel can support the survival and adhesion of cardiomyocytes. Compared with chitosan hydrogel, CSVC hydrogel can clearly improve the survival of cardiomyocytes and reduce the ROS level under H₂O₂-induced oxidative stress conditions. These results suggest that CSVC hydrogel has the potential to support the survival of cardiomyocytes in tissue engineering.

Potential of Bone-Marrow-Derived Mesenchymal Stem Cells for Maxillofacial and Periodontal Regeneration: A Narrative Review

Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are one of the most widely studied postnatal stem cell populations and are considered to utilize more frequently in cell-based therapy and cancer. These types of stem cells can undergo multilineage differentiation including blood cells, cardiac cells, and osteogenic cells differentiation, thus providing an alternative source of mesenchymal stem cells (MSCs) for tissue engineering and personalized medicine. Despite the ability to reprogram human adult somatic cells to induced pluripotent stem cells (iPSCs) in culture which provided a great opportunity and opened the new door for establishing the in vitro disease modeling and generating an unlimited source for cell base therapy, using MSCs for regeneration purposes still have a great chance to cure diseases. In this review, we discuss the important issues in MSCs biology including the origin and functions of MSCs and their application for craniofacial and periodontal tissue regeneration, discuss the potential and clinical applications of this type of stem cells in differentiation to maxillofacial bone and cartilage in vitro, and address important future hopes and challenges in this field.

Stem cell therapy for dilated cardiomyopathy

BACKGROUND

Stem cell therapy (SCT) has been proposed as an alternative treatment for dilated cardiomyopathy (DCM), nonetheless its effectiveness remains debatable.

OBJECTIVES

To assess the effectiveness and safety of SCT in adults with non-ischaemic DCM.

SEARCH METHODS

We searched CENTRAL in the Cochrane Library, MEDLINE, and Embase for relevant trials in November 2020. We also searched two clinical trials registers in May 2020.

SELECTION CRITERIA

Eligible studies were randomized controlled trials (RCT) comparing stem/progenitor cells with no cells in adults with non-ischaemic DCM. We included co-interventions such as the administration of stem cell mobilizing agents. Studies were classified and analysed into three categories according to the comparison intervention, which consisted of no intervention/placebo, cell mobilization with cytokines, or a different mode of SCT. The first two comparisons (no cells in the control group) served to assess the efficacy of SCT while the third (different mode of SCT) served to complement the review with information about safety and other information of potential utility for a better understanding of the effects of SCT.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all references for eligibility, assessed trial quality, and extracted data. We undertook a quantitative evaluation of data using random-effects meta-analyses. We evaluated heterogeneity using the I² statistic. We could not explore potential effect modifiers through subgroup analyses as they were deemed uninformative due to the scarce number of trials available. We assessed the certainty of the evidence using the GRADE approach. We created summary of findings tables using GRADEpro GDT. We focused our summary of findings on all-cause mortality, safety, health-related quality of life (HRQoL), performance status, and major adverse cardiovascular events.

MAIN RESULTS

We included 13 RCTs involving 762 participants (452 cell therapy and 310 controls). Only one study was at low risk of bias in all domains. There were many shortcomings in the publications that did not allow a precise assessment of the risk of bias in many domains. Due to the nature of the intervention, the main source of potential bias was lack of blinding of participants (performance bias). Frequently, the format of the continuous data available was not ideal for use in the meta-analysis and forced us to seek strategies for transforming data in a usable format. We are uncertain whether SCT reduces all-cause mortality in people with DCM compared to no intervention/placebo (mean follow-up 12 months) (risk ratio (RR) 0.84, 95% confidence interval (CI) 0.54 to 1.31; I² = 0%; studies = 7, participants = 361; very low-certainty evidence). We are uncertain whether SCT increases the risk of procedural complications associated with cells injection in people with DCM (data could not be pooled; studies = 7; participants = 361; very low-certainty evidence). We are uncertain whether SCT improves HRQoL (standardized mean difference (SMD) 0.62, 95% CI 0.01 to 1.23; I² = 72%; studies = 5, participants = 272; very low-certainty evidence) and functional capacity (6-minute walk test) (mean difference (MD) 70.12 m, 95% CI -5.28 to 145.51; I² = 87%; studies = 5, participants = 230; very low-certainty evidence). SCT may result in a slight functional class (New York Heart Association) improvement (data could not be pooled; studies = 6, participants = 398; low-certainty evidence). None of the included studies reported major adverse cardiovascular events as defined in our protocol. SCT may not increase the risk of ventricular arrhythmia (data could not be pooled; studies = 8, participants = 504; low-certainty evidence). When comparing SCT to cell mobilization with granulocyte-colony stimulating factor (G-CSF), we are uncertain whether SCT reduces all-cause mortality (RR 0.46, 95% CI 0.16 to 1.31; I² = 39%; studies = 3, participants = 195; very low-certainty evidence). We are uncertain whether SCT increases the risk of procedural complications associated with cells injection (studies = 1, participants = 60; very low-certainty evidence). SCT may not improve HRQoL (MD 4.61 points, 95% CI -5.62 to 14.83; studies = 1, participants = 22; low-certainty evidence). SCT may improve functional capacity (6-minute walk test) (MD 140.14 m, 95% CI 119.51 to 160.77; I² = 0%; studies = 2, participants = 155; low-certainty evidence). None of the included studies reported MACE as defined in our protocol or ventricular arrhythmia. The most commonly reported outcomes across studies were based on physiological measures of cardiac function where there were some beneficial effects suggesting potential benefits of SCT in people with non-ischaemic DCM. However, it is unclear if this intermediate effects translates into clinical benefits for these patients. With regard to specific aspects related to the modality of cell therapy and its delivery, uncertainties remain as subgroup analyses could not be performed as planned, making it necessary to wait for the publication of several studies that are currently in progress before any firm conclusion can be reached.

AUTHORS' CONCLUSIONS

We are uncertain whether SCT in people with DCM reduces the risk of all-cause mortality and procedural complications, improves HRQoL, and performance status (exercise capacity). SCT may improve functional class (NYHA), compared to usual care (no cells). Similarly, when compared to G-CSF, we are also uncertain whether SCT in people with DCM reduces the risk of all-cause mortality although some studies within this comparison observed a favourable effect that should be interpreted with caution. SCT may not improve HRQoL but may improve to some extent performance status (exercise capacity). Very low-quality evidence reflects uncertainty regarding procedural complications. These suggested beneficial effects of SCT, although uncertain due to the very low certainty of the evidence, are accompanied by favourable effects on some physiological measures of cardiac function. Presently, the most effective mode of administration of SCT and the population that could benefit the most is unclear. Therefore, it seems reasonable that use of SCT in people with DCM is limited to clinical research settings. Results of ongoing studies are likely to modify these conclusions.

Regenerative Potential of Platelet-Rich Fibrin Releasate Combined with Adipose Tissue-Derived Stem Cells in a Rat Sciatic Nerve Injury Model

Sciatic nerve injuries, not uncommon in trauma with a limited degree of functional recovery, are considered a persistent clinical, social, and economic problem worldwide. Accumulating evidence suggests that stem cells can promote the tissue regeneration through various mechanisms. The aim of the present study was to investigate the role of adipose tissue–derived stem cells (ADSCs) and combine with platelet-rich fibrin releasate (PRFr) in the regeneration of sciatic nerve injury in rats. Twenty-four Sprague-Dawley rats were randomly assigned to four groups, a blade was used to transect the left hindlimb sciatic nerve, and silicon tubes containing one of the following (by injection) were used to bridge the nerve proximal and distal ends (10-mm gap): group 1: untreated controls; group 2: PRFr alone; group 3: ADSCs alone; group 4: PRFr + ADSCs-treated. Walking function was assessed in horizontal rung ladder apparatus to compare the demands of the tasks and test sensitivity at 1-mo interval for a total of 3 mo. The gross inspection and histological examination was performed at 3 mo post transplantation. Overall, PRFr + ADSCs-treated performed better compared with PRFr or ADSCs injections alone. Significant group differences of neurological function were observed in ladder rung walking tests in all treated groups compared to that of untreated controls (P < 0.05). This injection approach may provide a successfully employed technique to target sciatic nerve defects in vivo, and the combined strategy of ADSCs with PRFr appears to have a superior effect on nerve repair.

Callus Formation in Fractured Femur of Rats Treated with Injection of Human Umbilical Cord Mesenchymal Stem Cell-Conditioned Medium

Mesenchymal stem cells-conditioned medium (MSC-CM) is the extraction from stem cell medium containing biological substances, including growth factors and cytokines. These substances play roles in the various functions of body regulatory, including bone formation. However, the effect of MSC-CM derived from human umbilical cord injection in femur fracture healing of rats has not been reported previously. This study aims to see the effect of MSC-CM derived from human umbilical cord injection on the callus formation of bone fracture healing in Wistar rats (Rattus norvegicus). A femur fracture in 54 Wistar rats was made by surgery according to the procedure under sterile conditions. After the surgery, rats were divided into 2 groups of 27, respectively. Injection in the control (0.1 mL/kg body weight NaCl) and MSC-CM group (0.1 mL/kg body weight MSC-CM) was performed on weeks 0, 1, 2, 3, 4, 5, 6, 7, and 8 after surgery. Radiographic images and the femur bone samples were taken and collected on days 1, 7, 14, 21, 28, 35, and 60 after surgery. Bone samples were then fixed in Bouin solution. Histologic preparations were done by the paraffin method, by cutting the tissue blocks into 5 μm thickness and then staining with Mallory aniline blue staining. The results were analyzed descriptively and quantitatively. The result showed that the soft callus formation occurred rapidly and got wider in the MSC-CM group than that of the control group. The administration of MSC-CM injection postfracture surgery to femur fracture cases in rats was capable to accelerate the callus formation.

Mesenchymal stem cells: Biological characteristics and application in disease therapy

Mesenchymal stem cells (MSCs) are multipotent stem cells. In addition to the capacity for self-renewal and multipotential differentiation, MSCs also have the following characteristics. MSCs can exert immunomodulatory functions through interaction with innate or adaptive immune cells, MSCs with poor immunogenicity can be used for allogeneic transplantation, and MSCs can "home" to inflammation and tumour sites. Based on these biological properties, MSCs demonstrate broad clinical application prospects in the treatment of tissue injury, autoimmune diseases, transplantation, cancer and other inflammation-related diseases. In this review we describe the biological characteristics of MSCs and discuss the research advances of MSCs in regenerative medicine, immunomodulation, oncology, and COVID-19, to fully understand the range of diseases in which MSC therapy may be beneficial.

Cell augmentation strategies for cardiac stem cell therapies

Myocardial infarction (MI) has been the primary cause of death in developed countries, resulting in a major psychological and financial burden for society. Current treatments for acute MI are directed toward rapid restoration of perfusion to limit damage to the myocardium, rather than promoting tissue regeneration and subsequent contractile function recovery. Regenerative cell therapies (CTs), in particular those using multipotent stem cells (SCs), are in the spotlight for treatment post‐MI. Unfortunately, the efficacy of CTs is somewhat limited by their poor long‐term viability, homing, and engraftment to the myocardium. In response, a range of novel SC‐based technologies are in development to provide additional cellular modalities, bringing CTs a step closer to the clinic. In this review, the current landscape of emerging CTs and their augmentation strategies for the treatment post‐MI are discussed. In doing so, we highlight recent advances in cell membrane reengineering via genetic modifications, recombinant protein immobilization, and the utilization of soft biomimetic scaffold interfaces.

Role of prostaglandin E2 in allogeneic mesenchymal stem cell therapy for cardiac repair

Ischemic heart disease is among the primary causes of cardiovascular-related deaths worldwide. Conventional treatments including surgical interventions and medical therapies aid in preventing further damage to heart muscle but are unable to provide a permanent solution. In recent years, stem cell therapy has emerged as an attractive alternative to restore damaged myocardium after myocardial injury. Allogeneic (donor-derived) mesenchymal stem cells (MSCs) have shown great promise in preclinical and clinical studies, making them the most widely accepted candidates for cardiac cell therapy. MSCs promote cardiac repair by modulating host immune system and secreting various soluble factors, of which prostaglandin E2 (PGE2) is an important one. PGE2 plays a significant role in regulating cardiac remodeling following myocardial injury. In this review, we provide an overview of allogeneic MSCs as candidates for myocardial regeneration with a focus on the role of the PGE2/cyclooxygenase-2 (COX2) pathway in mediating these effects.

Surface-Anchored Nanogel Coating Endows Stem Cells with Stress Resistance and Reparative Potency via Turning Down the Cytokine-Receptor Binding Pathways

Stem cell-based therapy has great potential in regenerative medicine. However, the survival and engraftment rates of transplanted stem cells in disease regions are poor and limit the effectiveness of cell therapy due to the fragility of stem cells. Here, an approach involving a single-cell coating of surface-anchored nanogel to regulate stem cell fate with anti-apoptosis capacity in the hypoxic and ischemic environment of infarcted hearts is developed for the first time. A polysialic acid-based system is used to anchor microbial transglutaminase to the external surface of the cell membrane, where it catalyzes the crosslinking of gelatin. The single-cell coating with surface-anchored nanogel endows mesenchymal stem cells (MSCs) with stress resistance by blocking the activity of apoptotic cytokines including the binding of tumor necrosis factor α (TNFα) to tumor necrosis factor receptor, which in turn maintains mitochondrial integrity, function and protects MSCs from TNFα-induces apoptosis. The administration of surface engineered MSCs to hearts results in significant improvements in engraftment, cardiac function, infarct size, and vascularity compared with using uncoated MSCs in treating myocardial infarction. The surface-anchored, biocompatible cell surface engineering with nanogel armor provides a new way to produce robust therapeutic stem cells and may explore immense potentials in cell-based therapy.

D-galactose-induced toxicity associated senescence mitigated by alpinate oxyphyllae fructus fortified adipose-derived mesenchymal stem cells

This study addresses the effect of D-galactose-induced toxicity associated senescence mitigated by alpinate oxyphyllae fructus (AOF; Alpinia oxyphylla Miq) extracts fortified with adipose-derived mesenchymal stem cells (ADMSCs) in rats. Male 18 week-old Wistar Kyoto (WKY) rats were used in this study. We analyzed cardiac fibrosis by Masson's trichrome staining. The tissue sections were dyed using hematoxylin and eosin (H&E). Tissue sections were stained for the restoration of Nrf2 expression in treatment groups by immunohistochemistry. Immunohistochemistry and western blotting analysis showed that AOF with ADMSCs could significantly reduce aging-induced oxidative stress in D-galactose-induced aging rat hearts by inducing Nrf2 pathway. Reduction in ROS resulted in the suppression of inflammatory signals (p-NF-κB and IL-6). Histopathological studies were showed an increased interstitium and collagen accumulation in aging-induced heart sections. However, AOF and ADMSCs treated hearts were recovered from cardiac remodeling. Furthermore, hypertrophy and fibrosis associated markers were also significantly reduced (P < .05) in treatment groups. We speculate that ADMSCs might activate certain paracrine factors, which could target the upstream activator of aging associated cardiac complications and AOF might provide homing for these stem cells.

Exosomes in disease and regeneration: biological functions, diagnostics, and beneficial effects

Exosomes are a subtype of extracellular vesicles. They range from 30 to 150 nm in diameter and originate from intraluminal vesicles. Exosomes were first identified as the mechanism for releasing unnecessary molecules from reticulocytes as they matured to red blood cells. Since then, exosomes have been shown to be secreted by a broad spectrum of cells and play an important role in the cardiovascular system. Different stimuli are associated with increased exosome release and result in different exosome content. The release of harmful DNA and other molecules via exosomes has been proposed as a mechanism to maintain cellular homeostasis. Because exosomes contain parent cell-specific proteins on the membrane and in the cargo that is delivered to recipient cells, exosomes are potential diagnostic biomarkers of various types of diseases, including cardiovascular disease. As exosomes are readily taken up by other cells, stem cell-derived exosomes have been recognized as a potential cell-free regenerative therapy to repair not only the injured heart but other tissues as well. The objective of this review is to provide an overview of the biological functions of exosomes in heart disease and tissue regeneration. Therefore, state-of-the-art methods for exosome isolation and characterization, as well as approaches to assess exosome functional properties, are reviewed. Investigation of exosomes provides a new approach to the study of disease and biological processes. Exosomes provide a potential "liquid biopsy," as they are present in most, if not all, biological fluids that are released by a wide range of cell types.

Current Status of Cell-Based Therapy in Patients with Critical Limb Ischemia

(1) Background: The treatment of peripheral arterial disease (PAD) is focused on improving perfusion and oxygenation in the affected limb. Standard revascularization methods include bypass surgery, endovascular interventional procedures, or hybrid revascularization. Cell-based therapy can be an alternative strategy for patients with no-option critical limb ischemia who are not eligible for endovascular or surgical procedures. (2) Aims: The aim of this narrative review was to provide an up-to-date critical overview of the knowledge and evidence-based medicine data on the position of cell therapy in the treatment of PAD. The current evidence on the cell-based therapy is summarized and future perspectives outlined, emphasizing the potential of exosomal cell-free approaches in patients with critical limb ischemia. (3) Methods: Cochrane and PubMed databases were searched for keywords “critical limb ischemia and cell therapy”. In total, 589 papers were identified, 11 of which were reviews and 11 were meta-analyses. These were used as the primary source of information, using cross-referencing for identification of additional papers. (4) Results: Meta-analyses focusing on cell therapy in PAD treatment confirm significantly greater odds of limb salvage in the first year after the cell therapy administration. Reported odds ratio estimates of preventing amputation being mostly in the region 1.6–3, although with a prolonged observation period, it seems that the odds ratio can grow even further. The odds of wound healing were at least two times higher when compared with the standard conservative therapy. Secondary endpoints of the available meta-analyses are also included in this review. Improvement of perfusion and oxygenation parameters in the affected limb, pain regression, and claudication interval prolongation are discussed. (5) Conclusions: The available evidence-based medicine data show that this technique is safe, associated with minimum complications or adverse events, and effective.

Hematopoietic Stem Cells and Mesenchymal Stromal Cells in Acute Radiation Syndrome

With the extensive utilization of radioactive materials for medical, industrial, agricultural, military, and research purposes, medical researchers are trying to identify new methods to treat acute radiation syndrome (ARS). Radiation may cause injury to different tissues and organs, but no single drug has been proven to be effective in all circumstances. Radioprotective agents are always effective if given before irradiation, but many nuclear accidents are unpredictable. Medical countermeasures that can be beneficial to different organ and tissue injuries caused by radiation are urgently needed. Cellular therapy, especially stem cell therapy, has been a promising approach in ARS. Hematopoietic stem cells (HSCs) and mesenchymal stromal cells (MSCs) are the two main kinds of stem cells which show good efficacy in ARS and have attracted great attention from researchers. There are also some limitations that need to be investigated in future studies. In recent years, there are also some novel methods of stem cells that could possibly be applied on ARS, like "drug" stem cell banks obtained from clinical grade human induced pluripotent stem cells (hiPSCs), MSC-derived products, and infusion of HSCs without preconditioning treatment, which make us confident in the future treatment of ARS. This review focuses on major scientific and clinical advances of hematopoietic stem cells and mesenchymal stromal cells on ARS.

Chimeric antigen receptor T-cell therapy beyond cancer: current practice and future prospects

Adoptive cell therapy with chimeric antigen receptor T (CAR-T) cells has achieved remarkable efficacy in the treatment of hematological malignancies, which has inspired researchers to expand the application of CAR-T-cell therapy to other medical conditions. Here, we review the current understanding and development of CAR-T-cell therapy for infectious diseases, autoimmune diseases and allotransplantation. The limitations and challenges of CAR-T-cell therapy in the treatment of these diseases and potential solutions to overcome these shortcomings are also discussed. With the development of novel designs of CARs and preclinical/clinical investigations, CAR-T-cell therapy is expected to be a potential cure option in a wide array of disease settings in the future.

Dose-Independent Therapeutic Benefit of Bone Marrow Stem Cell Transplantation after MI in Mice

Several cell populations derived from bone marrow (BM) have been shown to possess cardiac regenerative potential. Among these are freshly isolated CD133⁺ hematopoietic as well as culture-expanded mesenchymal stem cells. Alternatively, by purifying CD271⁺ cells from BM, mesenchymal progenitors can be enriched without an ex vivo cultivation. With regard to the limited available number of freshly isolated BM-derived stem cells, the effect of the dosage on the therapeutic efficiency is of particular interest. Therefore, in the present pre-clinical study, we investigated human BM-derived CD133⁺ and CD271⁺ stem cells for their cardiac regenerative potential three weeks post-myocardial infarction (MI) in a dose-dependent manner. The improvement of the hemodynamic function as well as cardiac remodeling showed no therapeutic difference after the transplantation of both 100,000 and 500,000 stem cells. Therefore, beneficial stem cell transplantation post-MI is widely independent of the cell dose and detrimental stem cell amplification in vitro can likely be avoided.

GLP: A requirement in cell therapies - perspectives for the cardiovascular field

In biomedical research, enormous progress is being made and new candidates for putative medicinal products emerge. However, most published preclinical data are not conducted according to the standard Good Laboratory Practice (GLP). GLP is mandatory for preclinical analysis of Advanced Therapy Medicinal Products (ATMP) and thereby a prerequisite for planning and conduction of clinical trials. Not inconsiderable numbers of clinical trials are terminated earlier or fail - do inadequate testing strategies or missing specialized assays during the preclinical development contribute to this severe complex of problems? Unfortunately, there is also a lack of access to GLP testing results and OECD (Organisation for Economic Co-operation and Development) GLP guidelines are not yet adjusted to ATMP specialties. Ultimately, GLP offers possibilities to generate reliable and reproducible data. Therefore, this review elucidates different GLP aspects in drug development, speculates on reasons of putative low GLP acceptance in the scientific community and mentions solution proposals.

Systemic and local delivery of mesenchymal stem cells for heart renovation: Challenges and innovations

In the beginning stage of heart disease, the blockage of blood flow frequently occurs due to the persistent damage and even death of myocardium. Cicatricial tissue developed after the death of myocardium can affect heart function, which ultimately leads to heart failure. In recent years, several studies carried out about the use of stem cells such as embryonic, pluripotent, cardiac and bone marrow-derived stem cells as well as myoblasts to repair injured myocardium. Current studies focus more on finding appropriate measures to enhance cell homing and survival in order to increase paracrine function. Until now, there is no universal delivery route for mesenchymal stem cells (MSCs) for different diseases. In this review, we summarize the advantages and challenges of the systemic and local pathways of MSC delivery. In addition, we also describe some advanced measures of cell delivery to improve the efficiency of transplantation. The combination of cells and therapeutic substances could be the most reliable method, which allows donor cells to deliver sufficient amounts of paracrine factors and provide long-lasting effects. The cardiac support devices or tissue engineering techniques have the potential to facilitate the controlled release of stem cells on local tissue for a sustained period. A novel promising epicardial drug delivery system is highlighted here, which not only provides MSCs with a favorable environment to promote retention but also increases the contact area and a number of cells recruited in the heart muscle.

Recovery of hibernating myocardium using stem cell patch with coronary bypass surgery

OBJECTIVE

This study aims to investigate the utility of mesenchymal stem cells (MSCs) applied as an epicardial patch during coronary artery bypass graft (CABG) to target hibernating myocardium; that is, tissue with persistently decreased myocardial function, in a large animal model.

METHODS

Hibernating myocardium was induced in juvenile swine (n = 12) using a surgically placed constrictor on the left anterior descending artery, causing stenosis without infarction. After 12 weeks, single-vessel CABG was performed using left internal thoracic artery to left anterior descending artery graft. During CABG, an epicardial patch was applied to the hibernating myocardium region consisting either of MSCs grown onto a polyglactin mesh (n = 6), or sham polyglactin mesh without MSCs (n = 6). Four weeks after CABG and patch placement, cardiac magnetic resonance imaging was performed and cardiac tissue was examined by gross inspection, including coronary dilators for vessel stenosis and patency, electron microscopy, protein assays, and proteomic analysis.

RESULTS

CABG + MSC myocardium showed improvement in contractile function (78.24% ± 19.6%) compared with sham patch (39.17% ± 5.57%) during inotropic stimulation (P < .05). Compared with sham patch control, electron microscopy of CABG + MSC myocardium showed improvement in mitochondrial size, number, and morphology; protein analysis similarly showed increases in expression of the mitochondrial biogenesis marker peroxisome proliferator-activated receptor gamma coactivator 1-alpha (0.0022 ± 0.0009 vs 0.023 ± 0.009) (P < .01) along with key components of the electron transport chain, including succinate dehydrogenase (complex II) (0.06 ± 0.02 vs 0.14 ± 0.03) (P < .05) and adenosine triphosphate synthase (complex V) (2.7 ± 0.4 vs 4.2 ± 0.26) (P < .05).

CONCLUSIONS

In hibernating myocardium, placement of a stem cell patch during CABG shows promise in improving myocardial function by improving mitochondrial morphology and function.

Systemic Infusion of Expanded CD133+ Cells and Expanded CD133+ Cell-Derived EVs for the Treatment of Ischemic Cardiomyopathy in a Rat Model of AMI

Myocardial infarction is a leading cause of death among all cardiovascular diseases. Cell therapies using a cell population enriched with endothelial progenitor cells (EPCs), expanded CD133⁺ cells, have promise as a therapeutic option for the treatment of ischemic areas after infarction. Recently, secreted membrane vesicles, including exosomes and microvesicles, have been recognized as new therapeutic candidates with important roles in intercellular and tissue communication. Expanded CD133⁺ cells have the ability to produce extracellular vesicles (EVs); however, their effect in the context of the heart is unknown. In the present study, we evaluated the effectiveness of the systemic application of expanded CD133⁺ cells and expanded CD133⁺ cell-derived EVs for the treatment of ischemic cardiomyopathy in a rat model of acute myocardial infarction (AMI) and examined the hypothesis that the EVs, because of their critical role in transferring regenerative signals from stem cells to the injured tissues, might elicit an equal or better therapeutic response than the expanded CD133⁺ cells. We demonstrate that the systemic application of expanded CD133⁺ cells and EVs has similar effects in infarcted rats. Few animals per group showed improvements in several heart and kidney parameters analyzed, but not significant differences were observed when comparing the groups. The systemic route may not be effective to treat ischemic cardiomyopathy; nonetheless, it may be a beneficial therapy to treat the side effects of AMI such as kidney damage.

Cellular therapy in periodontal regeneration

Periodontitis is a chronic inflammatory condition leading to destruction of the tooth supporting tissues, which if left untreated may cause tooth loss. The treatment of periodontitis mainly aims to arrest the inflammatory process by infection control measures, although in some specific lesions a limited periodontal regeneration can also be attained. Current regenerative approaches are aimed to guide the cells with regenerative capacity to repopulate the lesion and promote new cementum and new connective tissue attachment. The first phase in periodontal tissue regeneration involves the differentiation of mesenchymal cells into cementoblasts to promote new cementum, thus facilitating the attachment of new periodontal ligament fibers to the root and the alveolar bone. Current regenerative approaches limit themselves to the confines of the lesion by promoting the self-regenerative potential of periodontal tissues. With the advent of bioengineered therapies, several studies have investigated the potential use of cell therapies, mainly the use of undifferentiated mesenchymal cells combined with different scaffolds. The understanding of the origin and differentiation patterns of these cells is, therefore, important to elucidate their potential therapeutic use and their comparative efficacy with current technologies. This paper aims to review the in vitro and experimental studies using cell therapies based on application of cementoblasts and mesenchymal stem cells isolated from oral tissues when combined with different scaffolds.

Stem Cells: The Game Changers of Human Cardiac Disease Modelling and Regenerative Medicine

A comprehensive understanding of the molecular basis and mechanisms underlying cardiac diseases is mandatory for the development of new and effective therapeutic strategies. The lack of appropriate in vitro cell models that faithfully mirror the human disease phenotypes has hampered the understanding of molecular insights responsible of heart injury and disease development. Over the past decade, important scientific advances have revolutionized the field of stem cell biology through the remarkable discovery of reprogramming somatic cells into induced pluripotent stem cells (iPSCs). These advances allowed to achieve the long-standing ambition of modelling human disease in a dish and, more interestingly, paved the way for unprecedented opportunities to translate bench discoveries into new therapies and to come closer to a real and effective stem cell-based medicine. The possibility to generate patient-specific iPSCs, together with the new advances in stem cell differentiation procedures and the availability of novel gene editing approaches and tissue engineering, has proven to be a powerful combination for the generation of phenotypically complex, pluripotent stem cell-based cellular disease models with potential use for early diagnosis, drug screening, and personalized therapy. This review will focus on recent progress and future outcome of iPSCs technology toward a customized medicine and new therapeutic options.

Predicting Angiogenesis by Endothelial Progenitor Cells Relying on In-Vitro Function Assays and VEGFR-2 Expression Levels

Clinical trials have demonstrated the safety and efficacy of autologous endothelial progenitor cell (EPC) therapy in various diseases. Since EPCs' functions are influenced by genetic, systemic and environmental factors, the therapeutic potential of each individual EPCs is unknown and may affect treatment outcome. Therefore, our aim was to compare EPCs function among healthy donors in order to predict blood vessel formation (angiogenesis) before autologous EPC transplantation. Human EPCs were isolated from the blood of ten volunteers. EPCs proliferation rate, chemoattractant ability, and CXCR4 mRNA levels were different among donors (p < 0.0001, p < 0.01, p < 0.001, respectively). A positive correlation was found between SDF-1, CXCR4, and EPCs proliferation (R = 0.736, p < 0.05 and R = 0.8, p < 0.01, respectively). In-vivo, blood vessels were counted ten days after EPCs transplantation in a subcutaneous mouse model. Mean vessel density was different among donors (p = 0.0001); nevertheless, donors with the lowest vessel densities were higher compared to control (p < 0.05). Finally, using a linear regression model, a mathematical equation was generated to predict blood vessel density relying on: (i) EPCs chemoattractivity, and (ii) VEGFR-2 mRNA levels. Results reveal differences in EPCs functions among healthy individuals, emphasizing the need for a potency assay to pave the way for standardized research and clinical use of human EPCs.

CoCl2 induced hypoxia enhances osteogenesis of rat bone marrow mesenchymal stem cells through cannabinoid receptor 2

OBJECTIVES

This study aims to investigate the role of Cannabinoid receptor 2 (CB2) on osteogenesis of bone marrow-derived mesenchymal stem cells (BMSCs) under hypoxia.

MATERIALS AND METHODS

BMSCs were isolated from Sprague-Dawley rats and cultured in the presence of cobalt chloride (CoCl₂) to induce intracellular hypoxia. Cell proliferation was measured with MTT assay. Quantitative real-time PCR and western blot were applied to evaluate the mRNA and protein expressions of CB2 and osteogenic indicators including osteocalcin, RUNX2, collagen-1 and osterix (SP7). The osteogenic differentiation of BMSCs was further examined by ALP assay and alizarin red S (ARS) staining. Moreover, the activation of MAPKs signaling pathways was analyzed by western blot.

RESULTS

CoCl₂ dose-dependently increased hypoxia inducible factor while higher concentrations (200 and 400 μM) of CoCl₂ markedly inhibited cell proliferation. CoCl₂ induced hypoxia significantly increased the protein and mRNA expressions of osteocalcin, RUNX2, collagen-1 and osterix, along with enhanced ALP and ARS staining. Interestingly, such effects can be inhibited by the addition of CB2 inhibitor AM630. Moreover, AM630 partially inhibited hypoxia-induced p38 and ERK pathways, which may lead to a decrease in the osteogenic transcripts of RUNX2, collagen-1 and osterix.

CONCLUSIONS

CoCl₂ induced hypoxia could promote osteogenesis of rat BMSCs possibly through CB2.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

Multipotent fetal-derived Cdx2 cells from placenta regenerate the heart

There is a critical need to identify accessible stem cells that can form spontaneously beating cardiomyocytes (CMs) and enable regeneration. Here, we establish that intravenous delivery of placental Cdx2 cells resulted in directed homing, sustained engraftment, and differentiation into CMs and vascular cells in damaged hearts, significantly improving cardiac function. This study unveils a distinctive functional significance of Cdx2 beyond its established role in embryonic patterning. Therapeutic use of Cdx2 cells may represent a vital advance, as these cells are multipotent and immunologically naive, with a unique proteome, compared with embryonic stem cells. Moreover, they exhibit the ability to selectively home to sites of injury. These characteristics pave the way for novel allogeneic stem cell therapy for cardiac disease.

The extremely limited regenerative potential of adult mammalian hearts has prompted the need for novel cell-based therapies that can restore contractile function in heart disease. We have previously shown the regenerative potential of mixed fetal cells that were naturally found migrating to the injured maternal heart. Exploiting this intrinsic mechanism led to the current hypothesis that Caudal-type homeobox-2 (Cdx2) cells in placenta may represent a novel cell type for cardiac regeneration. Using a lineage-tracing strategy, we specifically labeled fetal-derived Cdx2 cells with enhanced green fluorescent protein (eGFP). Cdx2-eGFP cells from end-gestation placenta were assayed for cardiac differentiation in vitro and in vivo using a mouse model of myocardial infarction. We observed that these cells differentiated into spontaneously beating cardiomyocytes (CMs) and vascular cells in vitro, indicating multipotentiality. When administered via tail vein to infarcted wild-type male mice, they selectively and robustly homed to the heart and differentiated to CMs and blood vessels, resulting in significant improvement in contractility as noted by MRI. Proteomics and immune transcriptomics studies of Cdx2-eGFP cells compared with embryonic stem (ES) cells reveal that they appear to retain “stem”-related functions of ES cells but exhibit unique signatures supporting roles in homing and survival, with an ability to evade immune surveillance, which is critical for cell-based therapy. Cdx2-eGFP cells may potentially represent a therapeutic advance in allogeneic cell therapy for cardiac repair.

Regulation of Redox Homeostasis by Nonthermal Biocompatible Plasma Discharge in Stem Cell Differentiation

Recently, a growing body of evidence has shown the role of reactive species as secondary messengers in cell proliferation and differentiation, as opposed to the harmful metabolism byproducts that they were previously solely recognized as. Thus, the balance of intracellular reduction-oxidation (redox) homeostasis plays a vital role in the regulation of stem cell self-renewal and differentiation. Nonthermal biocompatible plasma (NBP) has emerged as a novel tool in biomedical applications. Recently, NBP has also emerged as a powerful tool in the tissue engineering field for the surface modification of biomaterial and the promotion of stem cell differentiation by the regulation of intracellular redox biology. NBP can generate various kinds of reactive oxygen species (ROS) and reactive nitrogen species (RNS), which may play the role of the second passenger in the cell signaling network and active antioxidant system in cells. Herein, we review the current knowledge on mechanisms by which NBP regulates cell proliferation and differentiation through redox modification. Considering the importance of redox homeostasis in the regulation of stem cell differentiation, understanding the underlying molecular mechanisms involved will provide important new insights into NBP-induced stem cell differentiation for tissue engineering.

Exercise and Cardiovascular Progenitor Cells

Autologous stem/progenitor cell-based methods to restore blood flow and function to ischemic tissues are clinically appealing for the substantial proportion of the population with cardiovascular diseases. Early preclinical and case studies established the therapeutic potential of autologous cell therapies for neovascularization in ischemic tissues. However, trials over the past ∼15 years reveal the benefits of such therapies to be much smaller than originally estimated and a definitive clinical benefit is yet to be established. Recently, there has been an emphasis on improving the number and function of cells [herein generally referred to as circulating angiogenic cells (CACs)] used for autologous cell therapies. CACs include of several subsets of circulating cells, including endothelial progenitor cells, with proangiogenic potential that is largely exerted through paracrine functions. As exercise is known to improve CV outcomes such as angiogenesis and endothelial function, much attention is being given to exercise to improve the number and function of CACs. Accordingly, there is a growing body of evidence that acute, short-term, and chronic exercise have beneficial effects on the number and function of different subsets of CACs. In particular, recent studies show that aerobic exercise training can increase the number of CACs in circulation and enhance the function of isolated CACs as assessed in ex vivo assays. This review summarizes the roles of different subsets of CACs and the effects of acute and chronic exercise on CAC number and function, with a focus on the number and paracrine function of circulating CD34+ cells, CD31+ cells, and CD62E+ cells. © 2019 American Physiological Society. Compr Physiol 9:767-797, 2019.

Efficacy of Cellular Therapy for Diabetic Foot Ulcer: A Meta-Analysis of Randomized Controlled Clinical Trials

Diabetes mellitus is a widely spread chronic disease with growing incidence worldwide, and diabetic foot ulcer is one of the most serious complications of diabetes. Cellular therapy has shown promise in the management of diabetic foot ulcer in many preclinical experiments and clinical researches. Here, we performed a meta-analysis to evaluate the efficacy and safety of cellular therapy in the management of diabetic foot ulcer. We systematically searched PubMed, MEDLINE, EMBASE, and Cochrane Library databases from inception to May 2017 for randomized controlled trials assessing the efficacy of cellular therapy in diabetic foot ulcer, and a meta-analysis was conducted. A total of 6 randomized controlled clinical trials involving 241 individuals were included in this meta-analysis. The results suggested that cellular therapy could help accelerating the healing of diabetic foot ulcer, presented as higher ankle-brachial index (mean difference = 0.17, 95% confidence interval [CI] = 0.11 to 0.23), higher transcutaneous oxygen pressure (standardized mean difference [SMD] = 1.43; 95% CI, 1.09– to 1.78), higher ulcer healing rate (relative risk [RR] = 1.78; 95% CI, 1.41 to 2.25), higher amputation-free survival (RR = 1.25; 95% CI, 1.11 to 1.40), and lower scale of pain (SMD = −1.69; 95% CI, −2.05 to −1.33). Furthermore, cellular therapy seemed to be safe, with no serious complications and low risk of short-term slight complications. Cellular therapy could accelerate the rate of diabetic foot ulcer healing and may be more efficient than standard therapy for diabetic foot treatment.

Bone marrow cell therapy and cardiac reparability: better cell characterization will enhance clinical success

Nearly two decades of experimental and clinical research with bone marrow cells have paved the way for Phase III pivotal trials in larger groups of heart patients. Despite immense advancements, a multitude of factors are hampering the acceptance of bone marrow cell-based therapy for routine clinical use. These include uncertainties regarding purification and characterization of the cell preparation, delivery protocols, mechanistic understanding and study end points and their methods of assessment. Clinical data show mediocre outcomes in terms of sustained cardiac pump function. This review reasons that the modest outcomes observed in trials thus far are based on quality of the cell preparation with a focus on the chronological aging of cells when autologous cells are used for transplantation in elderly patients.

The use of stem cells in ischemic heart disease treatment

Ischemic heart disease is a major cause of death and disabilities worldwide. Unfortunately, not all patients are suitable for direct revascularization. Cell-based therapies may be alternative options because of their potential to promote neovascularisation and endothelial repair, improving myocardial perfusion. The success of cell-based therapies depends on the type of implanted stem cells, delivery method and underlying disease. Several different cell populations including bone marrow-derived mononuclear cells (MNCs), mesenchymal stromal cells (MSCs), CD34+, CD133+, endothelial progenitor cells, adipose-derived mesenchymal stromal cells (ASCs) and stem cells from placenta and umbilical cord have been investigated. Presently, no consensus exists about the best cell type for clinical regenerative therapy. Because the system of coronary arteries in the ischemic area is poor and most of the coronary artery is significantly narrowed or closed, direct implantation of stem cells in the ischemic area of the heart muscle appears an attractive method.