Activation of Notch1 signalling promotes multi-lineage differentiation of c-Kit(POS)/NKX2.5(POS) bone marrow stem cells: implication in stem cell translational medicine

Application and challenges of stem cells in cardiovascular aging

With the rapid development of society and the economy, population aging has become a common challenge faced by many countries in the world today. Structural and functional changes in the cardiovascular system can occur with age, increasing the incidence and severity of cardiovascular diseases in older adults. Due to the limited regenerative capacity of myocardial cells, myocardial infarction and its resulting heart failure and congenital heart disease have become the number one killer of human health. At present, the treatment of cardiovascular diseases includes drug therapy and nondrug therapy. Nondrug therapy mainly includes minimally invasive interventional therapy, surgical diagnosis and treatment, and cell therapy. Long-term drug treatment may cause headache due to vasodilation, lower blood pressure, digestive system dysfunction and other side effects. Surgical treatment is traumatic, difficult to treat, and expensive. In recent years, stem cell therapy has exhibited broad application prospects in basic and clinical research on cardiovascular disease because of its plasticity, self-renewal and multidirectional differentiation potential. Therefore, this paper looks at stem cell therapy for diseases, reviews recent advances in the mechanism and clinical transformation of cardiovascular aging and related diseases in China, and briefly discusses the development trend and future prospects of cardiovascular aging research.

Intervention effects of traditional Chinese medicine on stem cell therapy of myocardial infarction

Cardiovascular diseases are the leading cause of global mortality, in which myocardial infarction accounts for 46% of total deaths. Although good progress has been achieved in medication and interventional techniques, a proven method to repair the damaged myocardium has not yet been determined. Stem cell therapy for damaged myocardial repair has evolved into a promising treatment for ischemic heart disease. However, low retention and poor survival of the injected stem cells are the major obstacles to achieving the intended therapeutic effects. Chinese botanical and other natural drug substances are a rich source of effective treatment for various diseases. As such, numerous studies have revealed the role of Chinese medicine in stem cell therapy for myocardial infarction treatment, including promoting proliferation, survival, migration, angiogenesis, and differentiation of stem cells. Here, we discuss the potential and limitations of stem cell therapy, as well as the regulatory mechanism of Chinese medicines underlying stem cell therapy. We focus on the evidence from pre-clinical trials and clinical practices, and based on traditional Chinese medicine theories, we further summarize the mechanisms of Chinese medicine treatment in stem cell therapy by the commonly used prescriptions. Despite the pre-clinical evidence showing that traditional Chinese medicine is helpful in stem cell therapy, there are still some limitations of traditional Chinese medicine therapy. We also systematically assess the detailed experimental design and reliability of included pharmacological research in our review. Strictly controlled animal models with multi-perspective pharmacokinetic profiles and high-grade clinical evidence with multi-disciplinary efforts are highly demanded in the future.

PSME4 Degrades Acetylated YAP1 in the Nucleus of Mesenchymal Stem Cells

Intensive research has focused on minimizing the infarct area and stimulating endogenous regeneration after myocardial infarction. Our group previously elucidated that apicidin, a histone deacetylase (HDAC) inhibitor, robustly accelerates the cardiac commitment of naïve mesenchymal stem cells (MSCs) through acute loss of YAP1. Here, we propose the novel regulation of YAP1 in MSCs. We found that acute loss of YAP1 after apicidin treatment resulted in the mixed effects of transcriptional arrest and proteasomal degradation. Subcellular fractionation revealed that YAP1 was primarily localized in the cytoplasm. YAP1 was acutely relocalized into the nucleus and underwent proteasomal degradation. Interestingly, phosphor-S127 YAP1 was shuttled into the nucleus, suggesting that a mechanism other than phosphorylation governed the subcellular localization of YAP1. Apicidin successfully induced acetylation and subsequent dissociation of YAP1 from 14-3-3, an essential molecule for cytoplasmic restriction. HDAC6 regulated both acetylation and subcellular localization of YAP1. An acetylation-dead mutant of YAP1 retarded nuclear redistribution upon apicidin treatment. We failed to acquire convincing evidence for polyubiquitination-dependent degradation of YAP1, suggesting that a polyubiquitination-independent regulator determined YAP1 fate. Nuclear PSME4, a subunit of the 26 S proteasome, recognized and degraded acetyl YAP1 in the nucleus. MSCs from PSME4-null mice were injected into infarcted heart, and aberrant sudden death was observed. Injection of immortalized human MSCs after knocking down PSME4 failed to improve either cardiac function or the fibrotic scar area. Our data suggest that acetylation-dependent proteasome subunit PSME4 clears acetyl-YAP1 in response to apicidin treatment in the nucleus of MSCs.

Combination Therapy of Stem Cell-derived Exosomes and Biomaterials in the Wound Healing

Wound healing is a serious obstacle due to the complexity of evaluation and management. While novel approaches to promoting chronic wound healing are of critical interest at the moment, several studies have demonstrated that combination therapy is critical for the treatment of a variety of diseases, particularly chronic wounds. Among the various approaches that have been proposed for wound care, regenerative medicine-based methods have garnered the most attention. As is well known, regenerative medicine's three primary tools are gene/cell therapy, biomaterials, and tissue engineering. Multifunctional biomaterials composed of synthetic and natural components are highly advantageous for exosome carriers, which utilizing them is an exciting wound healing method. Recently, stem cell-secreted exosomes and certain biomaterials have been identified as critical components of the wound healing process, and their combination therapy appears to produce significant results. This paper presents a review of literature and perspectives on the use of stem cell-derived exosomes and biomaterials in wound healing, particularly chronic wounds, and discusses the possibility of future clinical applications.

The effect of shear stress on cardiac differentiation of mesenchymal stem cells

BACKGROUND

Stem cell therapy is developing as a valuable therapeutic trend for heart diseases. Most recent studies are aimed to find the most appropriate types of stem cells for the treatment of myocardial infarction (MI). The animal models have shown that bone marrow-derived mesenchymal stem cells (BMSCs) are a possible, safe, and efficient type of stem cell used in MI. The previous study demonstrated that 5-Azacytidine (5-Aza) could promote cardiac differentiation in stem cells.

METHODS

This study used 5-Aza to induce cardiomyocyte differentiation in BMSCs both in static and microfluidic cell culture systems. For this purpose, we investigated the differentiation by using real-time PCR and Immunocytochemistry (ICC) Analysis.

RESULTS

Our results showed that 5-Aza could cause to express cardiac markers in BMSCs as indicated by real-time PCR and immunocytochemistry (ICC). However, BMSCs are exposed to both 5-Aza and shear stress, and their synergistic effects could significantly induce cardiac gene expressions in BMSCs. This level of gene expression was observed neither in 5-Aza nor in shear stress groups only.

CONCLUSIONS

These results demonstrate that when BMSCs expose to 5-Aza as well as mechanical cues such as shear stress, the cardiac gene expression can be increased dramatically.

Role of Signaling Pathways during Cardiomyocyte Differentiation of Mesenchymal Stem Cells

Multipotent stem cells, including mesenchymal stem cells (MSCs), represent a promising source to be used by regenerative medicine. They are capable of performing myogenic, chondrogenic, osteogenic and adipogenic differentiation. Also, MSCs are characterized by the expression of multiple surface antigens, but none of them appears to be particularly expressed on MSCs. Moreover, the prospect of monitoring and controlling MSC differentiation is a scientifically crucial regulatory and clinical requirement. Different transcription factors and signaling pathways are involved in cardiomyocyte differentiation. Due to the paucity of studies exclusively focused on cardiomyocyte differentiation of MSCs, present study aims at describing the roles of various signaling pathways (FGF, TGF, Wnt, Notch, etc.) in cardiomyocytes differentiation of MSCs. Understanding the signaling pathways that control the commitment and differentiation of cardiomyocyte cells not only will expand our basic understanding of molecular mechanisms of heart development, but also will enable us to develop therapeutic means of intervention in cardiovascular diseases.

Pathologic role of peptidyl-prolyl isomerase Pin1 in pulmonary artery remodeling

Peptidyl-prolyl isomerase Pin1 is crucial for cell proliferation, but its role in pulmonary artery remodeling (PAR) is unclear. In the present study, we aimed to evaluate the expression and contribution of Pin1 in PAR. Treatment with Pin1 inhibitor Juglone or Pin1-specific siRNAs ameliorated the expression of Pin1 and proliferating cell nuclear antigen (PCNA) in human pulmonary artery smooth muscle cells (PASMCs) in vitro, and Juglone treatment arrested the cell cycle at the G1 phase. Treatment with transforming growth factor β1 (TGF-β1) also enhanced Pin1 expression and PASMC proliferation. Immunohistochemical staining revealed that Pin1 and PCNA expression levels were increased and positively correlated with each other in PAR samples from humans and monocrotaline-treated Sprague-Dawley rats; these proteins were mainly localized in arteries undergoing remodeling, as well as inflammatory cells, and hyperplastic bronchial epithelial cells. Intraperitoneal injection of Juglone also led to morphologic and hemodynamic changes in PAR rats. Additionally, PAR rats displayed higher serum and lung TGF-β1 levels compared with controls, while administration of Juglone to PAR rats suppressed serum and lung TGF-β1 levels. The findings in this study suggest that TGF-β1 and Pin1 constitute a positive feedback loop, which plays an important role in the pathophysiology of PAR.

Stromal cell-derived factor-1 promotes osteoblastic differentiation of human bone marrow mesenchymal stem cells via the lncRNA-H19/miR-214-5p/BMP2 axis

BACKGROUND

Stromal cell-derived factor-1 (SDF-1) plays an important role in the osteoblastic differentiation of human bone marrow mesenchymal stem cells (hBMMSCs), but the specific mechanism remains unclear. Our study aimed to clarify the role of the lncRNA-H19/miR-214-5p/BMP2 axis in the osteoblastic differentiation of hBMMSCs induced by SDF-1.

METHODS

We used reverse-transcriptase polymerase chain reaction, western blotting, alkaline phosphatase activity test, and Alizarin red staining to evaluate the osteoblastic differentiation of primary hBMMSCs and the luciferase reporter assay to determine if lncRNA-H19 binds with miR-214-5p.

RESULTS

Our results indicated that SDF-1 (50 ng/mL) promotes the osteoblastic differentiation of hBMMSCs, significantly upregulates osteoblastogenic genes (OCN, OSX, RUNX2, and ALP), and increases Alizarin red staining, alkaline phosphatase activity, and lncRNA-H19 expression. Luciferase reporter assay verified that lncRNA-H19 binds with and represses miR-214-5p, thereby upregulating BMP2 expression. Use of miR-214-5p inhibitor or overexpression of lncRNA-H19 can promote the osteoblastic differentiation of hBMMSCs, but miR-214-5p or shH19 inhibits the osteoblastic differentiation of hBMMSCs. Treatment with an miR-214-5p inhibitor could rescue the inhibitory effect of shH19 on the osteoblastic differentiation of hBMMSCs.

CONCLUSIONS

Taken together, SDF-1 promotes the osteoblastic differentiation of hBMMSCs through the lncRNA-H19/miR-214-5p/BMP2 axis. Increased osteoblastic differentiation by an miR-214-5p inhibitor reveals a new possible strategy for the treatment of bone defect and osteoporosis.

Inhibition of Notch Signaling Promotes the Differentiation of Epicardial Progenitor Cells into Adipocytes

Background

The role of Notch signaling pathway in the differentiation of epicardial progenitor cells (EPCs) into adipocytes is unclear. The objective is to investigate the effects of Notch signaling on the differentiation of EPCs into adipocytes.

Methods

Frozen sections of C57BL/6J mouse hearts were used to observe epicardial adipose tissue (EAT), and genetic lineage methods were used to trace EPCs. EPCs were cultured in adipogenic induction medium with Notch ligand jagged-1 or γ-secretase inhibitor DAPT. The adipocyte markers, Notch signaling, and adipogenesis transcription factors were determined.

Results

There was EAT located at the atrial-ventricular groove in mouse. By using genetic lineage tracing methods, we found that EPCs were a source of epicardial adipocytes. EPCs had lipid droplet accumulation, and the expression of adipocyte markers FABP-4 and perilipin-1 was upregulated under adipogenic induction. Activating the Notch signaling with jagged-1 attenuated the adipogenic differentiation of EPCs and downregulated the key adipogenesis transcription factor peroxisome proliferator activated receptor-γ (PPAR-γ), while inhibiting the signaling promoted adipogenic differentiation and upregulated PPAR-γ. When blocking PPAR-γ, the role of Notch signaling in promoting adipogenic differentiation was inhibited.

Conclusions

EPCs are a source of epicardial adipocytes. Downregulation of the Notch signaling pathway promotes the differentiation of EPCs into adipocytes via PPAR-γ.

SETD4 in the Proliferation, Migration, Angiogenesis, Myogenic Differentiation and Genomic Methylation of Bone Marrow Mesenchymal Stem Cells

Epigenetic modification is a crucial mechanism affecting the biological function of stem cells. SETD4 is a histone methyltransferase, and its biological role in bone marrow mesenchymal stem cells (BMSCs) is currently unknown. In this study, we employed CRISPR/Cas9 technology edited mouse model and found that SETD4 knockout significantly promoted the proliferation of BMSCs, impaired BMSCs migration and differentiation potentials of lineages of cardiacmyocyte and smooth muscle cell, and even the angiogenesis via paracrine of VEGF. Through Reduced Representation Bisulfite Sequencing (RRBS) method, we verified that the overall genomic methylation of BMSCs in the SETD4 knockout group only was decreased by 0.47 % compared with wild type. However, the changed genomic methylation covers a total of 96,331 differential methylated CpG sites and 8,692 differential methylation regions (DMRs), with part of them settled in promoter regions. Bioinformatic analysis revealed that differential CpG islands and DMRs in promoter impacted 270 GO functions and 34 KEGG signaling pathways, with some closely related to stem cell biology. Mechanismly, SETD4 knockout inhibited sets of monomethylases and dimethylases for histone lysine, along with significant changes in some factors including Nkx2.5, Gata4, Gli2, Grem2, E2f7, Map7, Nr2f2 and Shox2 that associated with stem cell biology. These results are the first to reveal that even though SETD4 changes the genome's overall methylation to a limited extent in BMSCs, it still affects the numerous cellular functions and signaling pathways, implying SETD4-altered genomic methylation serves a crucial molecular role in BMSCs' biological functions.

Umbilical cord mesenchymal stromal cells engraft and transdifferentiate into cardiomyocyte-like cells following acute myocardial ischemia⋆

OBJECTIVE

Human umbilical cord-derived mesenchymal stromal cells (hUC-MSCs) gained importance in acute/chronic ischemic cardiomyopathy because of their outstanding regenerative potential in various pathologic conditions. The present study was designed to determine to what extent hUC-MSCs contribute to myocardial regeneration in acute experimental myocardial infarction (MI) in rats.

METHODS

Animals were assigned into two groups; the control group received intramyocardial PBS injections, while the hUC-MSC group received calcein-AM-labeled 8.8 × 10⁶/kg hUC-MSCs. Three weeks following the acute MI induction, rats were sacrificed after assessing the left ventricular (LV) function using echocardiography. For the assessment of infarct size, the triphenyl tetrazolium chloride (TTC) test was used in isolated hearts. Collagen-rich scar tissue was demonstrated using Masson's trichrome staining, followed by the detection of cardiac troponin I (cTnI), α-sarcomeric actin (α-SA), von Willebrand factor (vWF), CD68 and CD206 expressions in control and cell-injected sections.

RESULTS

Echocardiography revealed a significant difference (P = 0.037) in the LV ejection fraction between groups. TTC assays demonstrated a significant difference (P = 0.006) between the groups regarding the ratio of the infarcted LV area. Calcein-AM-loaded cells were identified mostly in ischemic myocardium. Transplanted cells also expressed human-specific cTnI, providing concrete proof of transdifferentiation into cardiomyocytes, and α-SA. vWF⁺ cells verified the neovascularization in the ischemic myocardium. Finally, a slight shift from pro-inflammatory to anti-inflammatory macrophages (CD68⁺/CD206⁺) was noted in both groups.

CONCLUSIONS

We found that the intramyocardial transplanted hUC-MSCs engrafted and partially transdifferentiated into cardiomyocytes, reduced scar formation, and induced angiogenesis through the association of pro/anti-inflammatory macrophages.

Macrophage-derived MMP-8 determines smooth muscle cell differentiation from adventitia stem/progenitor cells and promotes neointima hyperplasia

AIMS

Emerging evidence has suggested that adventitia stem/progenitor cells (AdSPCs) migrate into the intima of arteries in response to injury, where they differentiate towards smooth muscle cells (SMCs) and participate in neointimal hyperplasia. We have previously identified matrix metalloproteinase-8 (MMP8) as a key player in atherogenesis. In this study, we aimed to investigate the functional roles of macrophage-derived MMP8 in AdSPC differentiation and injury-induced arterial remodelling.

METHODS AND RESULTS

We first observed an important role for MMP8 in SMC differentiation from embryonic stem cells, but this effect was not seen in AdSPCs. Instead, through macrophages/AdSPCs co-culture and macrophage conditional culture medium studies, we have demonstrated that the MMP8 protein secreted from macrophages promotes SMC differentiation from AdSPCs. Mechanistically, we showed that macrophage-derived MMP8 promotes SMC differentiation from AdSPCs through modulating transforming growth factor-β activity and a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10)/Notch1 signalling. We further demonstrated that the binding site for CBF1, Suppressor of Hairless, and Lag-1 (CSL) within SMC gene promoters is responsible for Notch1 mediated SMC differentiation. Finally, we demonstrated that macrophage-derived MMP8 increased injury-induced neointimal SMC hyperplasia by activating ADAM10/Notch1 signalling.

CONCLUSIONS

We have identified macrophage-derived MMP8 as a regulator in SMC differentiation from AdSPCs and neointimal SMC hyperplasia in response to injury. Our data provide new insights into the roles of MMP8 in AdSPC differentiation and the pathogenesis of neointima formation in the context of angiographic restenosis, and therefore may aid in the development of novel therapeutic agents for the prevention of this disease.

The therapeutic potential of mesenchymal stem cells for cardiovascular diseases

Mesenchymal stem cells (MSCs) are derived from a wide range of sources and easily isolated and cultured. MSCs have the capacity for in vitro amplification and self-renewal, low immunogenicity and immunomodulatory properties, and under certain conditions, MSCs can be differentiated into a variety of cells. In the cardiovascular system, MSCs can protect the myocardium by reducing the level of inflammation, promoting the differentiation of myocardial cells around infarct areas and angiogenesis, increasing apoptosis resistance, and inhibiting fibrosis, which are ideal qualities for cardiovascular repair. Preclinical studies have shown that MSCs can be transplanted and improve cardiac repair, but challenges, such as their low rate of migration to the ischemic myocardium, low tissue retention, and low survival rate after transplantation, remain. This article reviews the potential and methods of MSC transplantation in the treatment of cardiovascular diseases (CVDs) and the challenges of the clinical use of MSCs.

Mechanisms supporting potential use of bone marrow-derived mesenchymal stem cells in psychocardiology

Despite great efforts made in recent years, globally cardiovascular disease (CVD) remains the most common and devastating disease. Pharmacological, interventional and surgical treatments have proved to be only partly satisfactory for the majority of patients. A major underlying cause of poor prognosis is a high comorbidity rate between CVD and mental illness, which calls for the approaches of psychocardiology. As psychiatric disorders and CVD can influence each other bidirectionally, it is necessary to develop novel therapies targeting both systems simultaneously. Therefore, innovative stem cell (SC) therapy has become the most promising treatment strategy in psychocardiology. Bone marrow-derived mesenchymal stem/stromal cells (BM-MSCs), among all different types of SCs, have drawn the most attention due to unique advantages in terms of ethical considerations, low immunogenicity and simplicity of preparation. In this review, we survey recent publications and clinical trials to summarize the knowledge and progress gained so far. Moreover, we discuss the feasibility of the clinical application of BM-MSCs in the area of psychocardiology.

Combination of Ligusticum Chuanxiong and Radix Paeonia Promotes Angiogenesis in Ischemic Myocardium through Notch Signalling and Mobilization of Stem Cells

Objective

To study the cardioprotective mechanism by which the combination of Chuanxiong (CX) and Chishao (CS) promotes angiogenesis.

Methods

Myocardial infarction (MI) mouse models were induced by ligation of the left anterior descending coronary artery. The effects on cardiac function were evaluated in the perindopril tert-butylamine group (PB group) (3 mg/kg/d), CX group (55 mg/kg/d), CS group (55 mg/kg/d), and CX and CS combination (CX-CS) group (27.5 mg/kg/d CX plus 27.5 mg/kg/d CS). RO4929097, an inhibitor of Notch γ secretase, was used (10 mg/kg/d) to explore the role of Notch signalling in the CX-CS-induced promotion of angiogenesis in the myocardial infarcted border zone (IBZ). The left ventricular ejection fraction (LVEF) and percentage of MI area were evaluated with animal ultrasound and Masson staining. The average optical densities (AODs) of CD31 and vWF in the myocardial IBZ were detected by immunofluorescence. Angiogenesis-related proteins including hypoxia-inducible factor 1-alpha (HIF-1α), fibroblast growth factor receptor 1 (FGFR-1), Notch1 and Notch intracellular domain (NICD), and stem cell mobilization-related proteins including stromal cell-derived factor 1 (SDF-1), C-X-C chemokine receptor type 4 (CXCR-4), and cardiotrophin1 were detected by western blot analysis.

Results

Compared with the model group, the CX-CS and PB groups both showed markedly improved LVEF and decreased percentage of MI area after 21 days of treatment. Although the CX group and CS group showed increased LVEF and decreased MI areas compared with the model group, the difference was not significant. The AOD of CD31 in the IBZ in both the model and the CX-CS-I group was markedly reduced compared with that in the sham group. CX-CS significantly increased the CD31 AOD in the IBZ and decreased the AODs of CD31 and vWF in the infarct zone compared with those in the model group. The expression of HIF-1α in both the model group and the CX-CS group was higher than that in the sham group. Compared with the model group, the expression of FGFR-1, SDF-1, cardiotrophin1, Notch1, and NICD was increased in the CX-CS group. Notch1 and NICD expression in the CX-CS-I group was reduced compared with that in the CX-CS group.

Conclusions

The combination of CX and CS protected cardiomyocytes in the IBZ better than CX or CS alone. The mechanism by which CX-CS protects ischemic myocardium may be related to the proangiogenesis effect of CX-CS exerted through Notch signalling and the mobilization of stem cells to the IBZ.

HMGB1 and repair: focus on the heart

High-mobility group box 1 (HMGB1) is one of the most abundant proteins in eukaryotes and the best characterized damage-associated molecular pattern (DAMP). The biological activities of HMGB1 depend on its subcellular location, context and post-translational modifications. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription regulation and genome stability; in the cytoplasm, its main function is to regulate the autophagic flux while in the extracellular environment, it possesses more complicated functions and it is involved in a large variety of different processes such as inflammation, migration, invasion, proliferation, differentiation and tissue regeneration. Due to this pleiotropy, the role of HMGB1 has been vastly investigated in various pathological diseases and a large number of studies have explored its function in cardiovascular pathologies. However, in this contest, the precise mechanism of action of HMGB1 and its therapeutic potential are still very controversial since is debated whether HMGB1 is involved in tissue damage or plays a role in tissue repair and regeneration. The main focus of this review is to provide an overview of the effects of HMGB1 in different ischemic heart diseases and to discuss its functions in these pathological conditions.

Hypoxia-stressed cardiomyocytes promote early cardiac differentiation of cardiac stem cells through HIF-1α/Jagged1/Notch1 signaling

Hypoxia is beneficial for the differentiation of stem cells transplanted for myocardial injury, but mechanisms underlying this benefit remain unsolved. Here, we report the impact of hypoxia-induced Jagged1 expression in cardiomyocytes (CMs) for driving the differentiation of cardiac stem cells (CSCs). Forced hypoxia-inducible factor 1α (HIF-1α) expression and physical hypoxia (5% O₂) treatment could induce Jagged1 expression in neonatal rat CMs. Pharmacological inhibition of HIF-1α by YC-1 attenuated hypoxia-promoted Jagged1 expression in CMs. An ERK inhibitor (PD98059), but not inhibitors of JNK (SP600125), Notch (DAPT), NF-κB (PTDC), JAK (AG490), or STAT3 (Stattic) suppressed hypoxia-induced Jagged1 protein expression in CMs. c-Kit⁺ CSCs isolated from neonatal rat hearts using a magnetic-activated cell sorting method expressed GATA4, SM22α or vWF, but not Nkx2.5 and cTnI. Moreover, 87.3% of freshly isolated CSCs displayed Notch1 receptor expression. Direct co-culture of CMs with BrdU-labeled CSCs enhanced CSCs differentiation, as evidenced by an increased number of BrdU⁺/Nkx2.5⁺ cells, while intermittent hypoxia for 21 days promoted co-culture-triggered differentiation of CSCs into CM-like cells. Notably, YC-1 and DAPT attenuated hypoxia-induced differentiation. Our results suggest that hypoxia induces Jagged1 expression in CMs primarily through ERK signaling, and facilitates early cardiac lineage differentiation of CSCs in CM/CSC co-cultures via HIF-1α/Jagged1/Notch signaling.

The cardiac niche role in cardiomyocyte differentiation of rat bone marrow-derived stromal cells: comparison between static and microfluidic cell culture methods

Due to the restricted potential of the heart to regenerate its damaged region, stem cell therapy is a promising treatment modality for myocardial infarction. It has been shown that incubation of bone marrow-derived stromal cells (BMSCs) with initial steps of cardiac differentiation in vitro, can have a significant effect on their therapeutic potential to treat myocardial infarction. Based on these well-established principals we were encouraged to study the direct co-culture of rat BMSCs with neonatal mouse almost pure cardiomyocytes (APCs) and cardiac niche cells (CNCs) in static 2D and microfluidic cell culture systems. Our results showed that the difference regarding the beating rate in isolated APCs and CNCs in both 2D and the microfluidic system was not statistically significant for 30 days. No beat rate could be observed in induced BMSCs in all groups during experiment time. Except for BMSCs cultured alone in both experimental culture conditions, data obtained from Real-time PCR analysis showed that differentiated BMSCs in all co-cultured groups expressed GATA4, Nkx2.5, CX43, cTnI, cTnT, and β-MHC during 4 weeks. BMSCs demonstrated a higher expression of these cardiac factors in microfluidic chips than those co-cultured in 24 well plates. Moreover, immunocytochemistry (ICC), also revealed the GATA4 expression in differentiated BMSCs in all co-cultured groups. It was found that, when combined with shear stress, co-culture with cardiomyocyte can differentiate BMSCs significantly toward cardiomyocyte rather than co-culture alone.

Thioredoxin-1 Protects Bone Marrow-Derived Mesenchymal Stromal Cells from Hyperoxia-Induced Injury In Vitro

Background

The poor survival rate of mesenchymal stromal cells (MSC) transplanted into recipient lungs greatly limits their therapeutic efficacy for diseases like bronchopulmonary dysplasia (BPD). The aim of this study is to evaluate the effect of thioredoxin-1 (Trx-1) overexpression on improving the potential for bone marrow-derived mesenchymal stromal cells (BMSCs) to confer resistance against hyperoxia-induced cell injury.

Methods

80% O₂ was used to imitate the microenvironment surrounding-transplanted cells in the hyperoxia-induced lung injury in vitro. BMSC proliferation and apoptotic rates and the levels of reactive oxygen species (ROS) were measured. The effects of Trx-1 overexpression on the level of antioxidants and growth factors were investigated. We also investigated the activation of apoptosis-regulating kinase-1 (ASK1) and p38 mitogen-activated protein kinases (MAPK).

Result

Trx-1 overexpression significantly reduced hyperoxia-induced BMSC apoptosis and increased cell proliferation. We demonstrated that Trx-1 overexpression upregulated the levels of superoxide dismutase and glutathione peroxidase as well as downregulated the production of ROS. Furthermore, we illustrated that Trx-1 protected BMSCs against hyperoxic injury via decreasing the ASK1/P38 MAPK activation rate.

Conclusion

These results demonstrate that Trx-1 overexpression improved the ability of BMSCs to counteract hyperoxia-induced injury, thus increasing their potential to treat hyperoxia-induced lung diseases such as BPD.

A brief review: the therapeutic potential of bone marrow mesenchymal stem cells in myocardial infarction

Myocardial infarction (MI) results in dysfunction and irreversible loss of cardiomyocytes and is among the most serious health threats today. Bone marrow mesenchymal stem cells (BMSCs), with their capacity for multidirectional differentiation, low immunogenicity, and high portability, can serve as ideal seed cells in cardiovascular disease therapy. In this review, we examine recent literature concerning the application of BMSCs for the treatment of MI and consider the following aspects: activity of transplanted cells, migration and homing of BMSCs, immunomodulatory and anti-inflammatory effects of BMSCs, anti-fibrotic activity of BMSCs, the role of BMSCs in angiogenesis, and differentiation of BMSCs into cardiomyocyte-like cells and endothelial cells. Each aspect is complementary to the others and together they promote the repair of cardiomyocytes by BMSCs after MI. Although transplantation of BMSCs has enabled new options for MI treatment, the critical issue we must now address is the reduced viability of transplanted BMSCs due to inadequate blood supply, poor nourishment of cells, and generation of free radicals. More clinical trials are needed to prove the therapeutic potential of BMSCs in MI.

Single-cell analysis of the fate of c-kit-positive bone marrow cells

The plasticity of c-kit-positive bone marrow cells (c-kit-BMCs) in tissues different from their organ of origin remains unclear. We tested the hypothesis that c-kit-BMCs are functionally heterogeneous and only a subgroup of these cells possesses cardiomyogenic potential. Population-based assays fall short of identifying the properties of individual stem cells, imposing on us the introduction of single cell-based approaches to track the fate of c-kit-BMCs in the injured heart; they included viral gene-tagging, multicolor clonal-marking and transcriptional profiling. Based on these strategies, we report that single mouse c-kit-BMCs expand clonally within the infarcted myocardium and differentiate into specialized cardiac cells. Newly-formed cardiomyocytes, endothelial cells, fibroblasts and c-kit-BMCs showed in their genome common sites of viral integration, providing strong evidence in favor of the plasticity of a subset of BMCs expressing the c-kit receptor. Similarly, individual c-kit-BMCs, which were infected with multicolor reporters and injected in infarcted hearts, formed cardiomyocytes and vascular cells organized in clusters of similarly colored cells. The uniform distribution of fluorescent proteins in groups of specialized cells documented the polyclonal nature of myocardial regeneration. The transcriptional profile of myogenic c-kit-BMCs and whole c-kit-BMCs was defined by RNA sequencing. Genes relevant for engraftment, survival, migration, and differentiation were enriched in myogenic c-kit-BMCs, a cell subtype which could not be assigned to a specific hematopoietic lineage. Collectively, our findings demonstrate that the bone marrow comprises a category of cardiomyogenic, vasculogenic and/or fibrogenic c-kit-positive cells and a category of c-kit-positive cells that retains an undifferentiated state within the damaged heart.

Y Chromosome Missing Protein, TBL1Y, May Play an Important Role in Cardiac Differentiation

Despite evidence for sex-specific cardiovascular physiology and pathophysiology, the biological basis for this dimorphism remains to be explored. Apart from hormonal factors, gender-related characteristics may reside in the function of sex chromosomes during cardiac development. In this study, we investigated the differential expression of the male-specific region of the Y chromosome (MSY) genes and their X counterparts during cardiac differentiation of human embryonic stem cells (hESC). We observed alterations in mRNA and protein levels of TBL1Y, PCDH11Y, ZFY, KDM5D, USP9Y, RPS4Y1, DDX3Y, PRY, XKRY, BCORP1, RBMY, HSFY, and UTY, which accompanied changes in intracellular localization. Of them, the abundance of a Y chromosome missing protein, TBL1Y, showed a significant increase during differentiation while the expression level of its X counterpart decreased. Consistently, reducing TBL1Y cellular level using siRNA approach influenced cardiac differentiation by reducing its efficacy as well as increasing the probability of impaired contractions. TBL1Y knockdown may have negatively impacted cardiogenesis by CtBP stabilization. Furthermore, we presented compelling experimental evidence to distinguish TBL1Y from TBL1X, its highly similar X chromosome homologue, and proposed reclassification of TBL1Y as "found missing protein" (PE1). Our results demonstrated that MSY proteins may play an important role in cardiac development.

High glucose promotes vascular smooth muscle cell proliferation by upregulating proto-oncogene serine/threonine-protein kinase Pim-1 expression

Serine/threonine kinase proviral integration site for Moloney murine leukemia virus 1 (Pim-1) plays an essential role in arterial wall cell proliferation and associated vascular diseases, including pulmonary arterial hypertension and aortic wall neointima formation. Here we tested a role of Pim-1 in high-glucose (HG)-mediated vascular smooth muscle cell (VSMC) proliferation. Pim-1 and proliferating cell nuclear antigen (PCNA) expression levels in arterial samples from streptozotocin-induced hyperglycemia rats were increased, compared with their weak expression in normoglycemic groups. In cultured rat VSMCs, HG led to transient Pim-1 expression decline, followed by sustained expression increase at both transcriptional and translational levels. Immunoblot analysis demonstrated that HG increased the expression of the 33-kDa isoform of Pim-1, but at much less extent to its 44-kDa plasma membrane isoform. D-glucose at a concentration of 25 mmol/L showed highest activity in stimulating Pim-1 expression. Both Pim-1 inhibitor quercetagetin and STAT3 inhibitor stattic significantly attenuated HG-induced VSMC proliferation and arrested cell cycle progression at the G1 phase. Quercetagetin showed no effect on Pim-1 expression but decreased the phosphorylated-Bad (T112)/Bad ratio in HG-treated VSMCs. However, stattic decreased phosphorylated-STAT3 (Y705) levels and caused transcriptional and translational down-regulation of Pim-1 in HG-treated VSMCs. Our findings suggest HG-mediated Pim-1 expression contributes to VSMC proliferation, which may be partly due to the activation of STAT3/Pim-1 signaling.

Key transcription factors in the differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells that represent a promising source for regenerative medicine. MSCs are capable of osteogenic, chondrogenic, adipogenic and myogenic differentiation. Efficacy of differentiated MSCs to regenerate cells in the injured tissues requires the ability to maintain the differentiation toward the desired cell fate. Since MSCs represent an attractive source for autologous transplantation, cellular and molecular signaling pathways and micro-environmental changes have been studied in order to understand the role of cytokines, chemokines, and transcription factors on the differentiation of MSCs. The differentiation of MSC into a mesenchymal lineage is genetically manipulated and promoted by specific transcription factors associated with a particular cell lineage. Recent studies have explored the integration of transcription factors, including Runx2, Sox9, PPARγ, MyoD, GATA4, and GATA6 in the differentiation of MSCs. Therefore, the overexpression of a single transcription factor in MSCs may promote trans-differentiation into specific cell lineage, which can be used for treatment of some diseases. In this review, we critically discussed and evaluated the role of transcription factors and related signaling pathways that affect the differentiation of MSCs toward adipocytes, chondrocytes, osteocytes, skeletal muscle cells, cardiomyocytes, and smooth muscle cells.