Unique Features of Cortical Bone Stem Cells Associated With Repair of the Injured Heart

miR-182/183-Rasa1 axis induced macrophage polarization and redox regulation promotes repair after ischemic cardiac injury

Few therapies have produced significant improvement in cardiac structure and function after ischemic cardiac injury (ICI). Our possible explanation is activation of local inflammatory responses negatively impact the cardiac repair process following ischemic injury. Factors that can alter immune response, including significantly altered cytokine levels in plasma and polarization of macrophages and T cells towards a pro-reparative phenotype in the myocardium post-MI is a valid strategy for reducing infarct size and damage after myocardial injury. Our previous studies showed that cortical bone stem cells (CBSCs) possess reparative effects after ICI. In our current study, we have identified that the beneficial effects of CBSCs appear to be mediated by miRNA in their extracellular vesicles (CBSC-EV). Our studies showed that CBSC-EV treated animals demonstrated reduced scar size, attenuated structural remodeling, and improved cardiac function versus saline treated animals. These effects were linked to the alteration of immune response, with significantly altered cytokine levels in plasma, and polarization of macrophages and T cells towards a pro-reparative phenotype in the myocardium post-MI. Our detailed in vitro studies demonstrated that CBSC-EV are enriched in miR-182/183 that mediates the pro-reparative polarization and metabolic reprogramming in macrophages, including enhanced OXPHOS rate and reduced ROS, via Ras p21 protein activator 1 (RASA1) axis under Lipopolysaccharides (LPS) stimulation. In summary, CBSC-EV deliver unique molecular cargoes, such as enriched miR-182/183, that modulate the immune response after ICI by regulating macrophage polarization and metabolic reprogramming to enhance repair.

Isolation of Vascular Wall Mesenchymal Stem Cells from the Thoracic Aorta of Adult Göttingen Minipigs: A New Protocol for the Simultaneous Endothelial Cell Collection

Two main classes of perivascular multipotent populations have been described: the microvascular pericytes and the vascular wall mesenchymal stem cells (VW-MSCs). VW-MSCs are isolated from large vessels in many species and they participate in vascular remodeling together with other cellular components such as endothelial cells. Considering that the Göttingen Minipigs are widely used in Europe as a translational model in the field of cardiovascular diseases, the aim of the present research was to isolate VW-MSCs from the adult aorta of Göttingen Minipigs while preserving and also collecting endothelial cells. The results obtained in the present research demonstrated that this new protocol allows us to obtain a pure population of VW-MSCs and endothelial cells. VW-MSCs from Göttingen Minipigs responded fully to the MSC minima international criteria, being positive to CD105, CD90, and CD44 and negative to CD45 and CD34. Moreover, VW-MSCs presented a differentiative potential towards osteogenic, chondrogenic, and adipogenic lineages. Overall, the present protocol, preserving the viability and phenotypic features of the two isolated populations, opens future possibilities of using minipig VW-MSCs and endothelial cells in in vitro vascular remodeling studies.

Mesenchymal Stromal Cells Overexpressing Farnesoid X Receptor Exert Cardioprotective Effects Against Acute Ischemic Heart Injury by Binding Endogenous Bile Acids

Bile acid metabolites have been increasingly recognized as pleiotropic signaling molecules that regulate cardiovascular functions, but their role in mesenchymal stromal cells (MSC)-based therapy has never been investigated. It is found that overexpression of farnesoid X receptor (FXR), a main receptor for bile acids, improves the retention and cardioprotection of adipose tissue-derived MSC (ADSC) administered by intramyocardial injection in mice with myocardial infarction (MI), which shows enhanced antiapoptotic, proangiogenic, and antifibrotic effects. RNA sequencing, LC-MS/MS, and loss-of-function studies reveal that FXR overexpression promotes ADSC paracrine angiogenesis via Angptl4. FXR overexpression improves ADSC survival in vivo but fails in vitro. By performing bile acid-targeted metabolomics using ischemic heart tissue, 19 bile acids are identified. Among them, cholic acid and deoxycholic acid significantly increase Angptl4 secretion from ADSC overexpressing FXR and further improve their proangiogenic capability. Moreover, ADSC overexpressing FXR shows significantly lower apoptosis by upregulating Nqo-1 expression only in the presence of FXR ligands. Retinoid X receptor α is identified as a coactivator of FXR. It is first demonstrated that there is a bile acid pool in the myocardial microenvironment. Targeting the bile acid-FXR axis may be a novel strategy for improving the curative effect of MSC-based therapy for MI.

Cortical bone stem cell-derived exosomes' therapeutic effect on myocardial ischemia-reperfusion and cardiac remodeling

Heart failure is the one of the leading causes of death in the United States. Heart failure is a complex syndrome caused by numerous diseases, including severe myocardial infarction (MI). MI occurs after an occlusion of a cardiac artery causing downstream ischemia. MI is followed by cardiac remodeling involving extensive remodeling and fibrosis, which, if the original insult is severe or prolonged, can ultimately progress into heart failure. There is no "cure" for heart failure because therapies to regenerate dead tissue are not yet available. Previous studies have shown that in both post-MI and post-ischemia-reperfusion (I/R) models of heart failure, administration of cortical bone stem cell (CBSC) treatment leads to a reduction in scar size and improved cardiac function. Our first study investigated the ability of mouse CBSC-derived exosomes (mCBSC-dEXO) to recapitulate mouse CBSCs (mCBSC) therapeutic effects in a 24-h post-I/R model. This study showed that injection of mCBSCs and mCBSC-dEXOs into the ischemic region of an infarct had a protective effect against I/R injury. mCBSC-dEXOs recapitulated the effects of CBSC treatment post-I/R, indicating exosomes are partly responsible for CBSC's beneficial effects. To examine if exosomes decrease fibrotic activation, adult rat ventricular fibroblasts (ARVFs) and adult human cardiac fibroblasts (NHCFs) were treated with transforming growth factor β (TGFβ) to activate fibrotic signaling before treatment with mCBSC- and human CBSC (hCBSC)-dEXOs. hCBSC-dEXOs caused a 100-fold decrease in human fibroblast activation. To further understand the signaling mechanisms regulating the protective decrease in fibrosis, we performed RNA sequencing on the NHCFs after hCBSC-dEXO treatment. The group treated with both TGFβ and exosomes showed a decrease in small nucleolar RNA (snoRNA), known to be involved with ribosome stability.NEW & NOTEWORTHY Our work is noteworthy due to the identification of factors within stem cell-derived exosomes (dEXOs) that alter fibroblast activation through the hereto-unknown mechanism of decreasing small nucleolar RNA (snoRNA) signaling within cardiac fibroblasts. The study also shows that the injection of stem cells or a stem-cell-derived exosome therapy at the onset of reperfusion elicits cardioprotection, emphasizing the importance of early treatment in the post-ischemia-reperfusion (I/R) wounded heart.

Cell Surface and Functional Features of Cortical Bone Stem Cells

The newly established mouse cortical-bone-derived stem cells (mCBSCs) are unique stem cells compared to mouse mesenchymal stem cells (mMSCs). The mCBSC-treated hearts after myocardial infarction have been reported to have greater improvement in myocardial structure and functions. In this study, we examined the stemness features, cell surface glycan profiles, and paracrine functions of mCBSCs compared with mMSCs. The stemness analysis revealed that the self-renewing capacity of mCBSCs was greater than mMSCs; however, the differentiation capacity of mCBSCs was limited to the chondrogenic lineage among three types of cells (adipocyte, osteoblast, chondrocyte). The cell surface glycan profiles by lectin array analysis revealed that α2-6sialic acid is expressed at very low levels on the cell surface of mCBSCs compared with that on mMSCs. In contrast, the lactosamine (Galβ1-4GlcNAc) structure, poly lactosamine- or poly N-acetylglucosamine structure, and α2-3sialic acid on both N- and O-glycans were more highly expressed in mCBSCs. Moreover, we found that mCBSCs secrete a greater amount of TGF-β1 compared to mMSCs, and that the TGF-β1 contributed to the self-migration of mCBSCs and activation of fibroblasts. Together, these results suggest that unique characteristics in mCBSCs compared to mMSCs may lead to advanced utility of mCBSCs for cardiac and noncardiac repair.

Cortical bone stem cells modify cardiac inflammation after myocardial infarction by inducing a novel macrophage phenotype

Acute damage to the heart, as in the case of myocardial infarction (MI), triggers a robust inflammatory response to the sterile injury that is part of a complex and highly organized wound-healing process. Cortical bone stem cell (CBSC) therapy after MI has been shown to reduce adverse structural and functional remodeling of the heart after MI in both mouse and swine models. The basis for these CBSC treatment effects on wound healing are unknown. The present experiments show that CBSCs secrete paracrine factors known to have immunomodulatory properties, most notably macrophage colony-stimulating factor (M-CSF) and transforming growth factor-β, but not IL-4. CBSC therapy increased the number of galectin-3+ macrophages, CD4+ T cells, and fibroblasts in the heart while decreasing apoptosis in an in vivo swine model of MI. Macrophages treated with CBSC medium in vitro polarized to a proreparative phenotype are characterized by increased CD206 expression, increased efferocytic ability, increased IL-10, TGF-β, and IL-1RA secretion, and increased mitochondrial respiration. Next generation sequencing revealed a transcriptome significantly different from M2a or M2c macrophage phenotypes. Paracrine factors from CBSC-treated macrophages increased proliferation, decreased α-smooth muscle actin expression, and decreased contraction by fibroblasts in vitro. These data support the idea that CBSCs are modulating the immune response to MI to favor cardiac repair through a unique macrophage polarization that ultimately reduces cell death and alters fibroblast populations that may result in smaller scar size and preserved cardiac geometry and function.NEW & NOTEWORTHY Cortical bone stem cell (CBSC) therapy after myocardial infarction alters the inflammatory response to cardiac injury. We found that cortical bone stem cell therapy induces a unique macrophage phenotype in vitro and can modulate macrophage/fibroblast cross talk.

Secreted Frizzled-Related Protein 5 Protects Against Cardiac Rupture and Improves Cardiac Function Through Inhibiting Mitochondrial Dysfunction

Background: Secreted frizzled-related protein 5 (Sfrp5) has been suggested to be a protective regulatory protein in coronary heart disease. However, the role of Sfrp5 in regulating ischemic injury and its consequences is not known. The aim of our study was to explore the effects of Sfrp5 on hearts after myocardial infarction (MI) and to investigate the underlying mechanisms.

Methods and Results: We found that Sfrp5 was downregulated over time in the heart tissue of MI mice. To further elucidate the role of Sfrp5 during MI, we established a cardiac overexpression of an Sfrp5 mouse model using the cardiotropic adeno-associated virus serotype 9 (AAV9). Overexpression of Sfrp5 significantly reduced infarct size as demonstrated by a decrease in mortality owing to cardiac rupture. Moreover, cardiac overexpression of Sfrp5 increased left ventricular function and mitochondrial biogenesis, decreased cardiomyocyte apoptosis, suppressed inflammation reaction, inhibited oxidative stress, and ameliorated cardiac remodeling as demonstrated by left ventricular ejection fraction, mitochondrial morphology, heart weight, NADH oxidase activity levels, and myocardial fibrosis at 2 weeks post-MI. At the molecular level, overexpression of Sfrp5 significantly increased the expression of p-AMPK^Thr172 protein with higher expression of mitochondrial fusion protein (MFN1 and MFN2) and lower expression of mitochondrial fission protein (p-Drp1^Ser616/Mid49/MFF/Fis-1). In isolated neonatal rat cardiac myocytes, Sfrp5 treatment attenuated hypoxia-induced mitochondrial dysfunction. Inhibition of AMPK activity with compound C abrogated this benefit.

Conclusions: Sfrp5 overexpression inhibits ischemic injury, reduces risk of cardiac rupture, ameliorates post-MI remodeling, and decreases the progression to heart failure via disrupting mitochondrial dysfunction and partly through normalizing the AMPK activity.

Bmi1 Augments Proliferation and Survival of Cortical Bone-Derived Stem Cells after Injury through Novel Epigenetic Signaling via Histone 3 Regulation

Ischemic heart disease can lead to myocardial infarction (MI), a major cause of morbidity and mortality worldwide. Multiple stem cell types have been safely transferred into failing human hearts, but the overall clinical cardiovascular benefits have been modest. Therefore, there is a dire need to understand the basic biology of stem cells to enhance therapeutic effects. Bmi1 is part of the polycomb repressive complex 1 (PRC1) that is involved in different processes including proliferation, survival and differentiation of stem cells. We isolated cortical bones stem cells (CBSCs) from bone stroma, and they express significantly high levels of Bmi1 compared to mesenchymal stem cells (MSCs) and cardiac-derived stem cells (CDCs). Using lentiviral transduction, Bmi1 was knocked down in the CBSCs to determine the effect of loss of Bmi1 on proliferation and survival potential with or without Bmi1 in CBSCs. Our data show that with the loss of Bmi1, there is a decrease in CBSC ability to proliferate and survive during stress. This loss of functionality is attributed to changes in histone modification, specifically histone 3 lysine 27 (H3K27). Without the proper epigenetic regulation, due to the loss of the polycomb protein in CBSCs, there is a significant decrease in cell cycle proteins, including Cyclin B, E2F, and WEE as well as an increase in DNA damage genes, including ataxia-telangiectasia mutated (ATM) and ATM and Rad3-related (ATR). In conclusion, in the absence of Bmi1, CBSCs lose their proliferative potential, have increased DNA damage and apoptosis, and more cell cycle arrest due to changes in epigenetic modifications. Consequently, Bmi1 plays a critical role in stem cell proliferation and survival through cell cycle regulation, specifically in the CBSCs. This regulation is associated with the histone modification and regulation of Bmi1, therefore indicating a novel mechanism of Bmi1 and the epigenetic regulation of stem cells.

High Cardiovascular Risk in Older Men with Poor Bone Microarchitecture-The Prospective STRAMBO Study

Data on the association between bone microarchitecture and cardiovascular disease (CVD) in men are scarce. We studied the link of bone microarchitecture and areal bone mineral density (aBMD) with the risk of major adverse coronary event (MACE) in a cohort of men aged 60 to 87 years followed prospectively for 8 years. At baseline, aBMD was measured using a Hologic Discovery-A device. Bone microarchitecture was assessed at distal radius and tibia by high-resolution peripheral quantitative computed tomography (XtremeCT Scanco device). During the study, 53 men had incident MACE. The analyses were adjusted for confounders related to bone and CVD. In 813 men (53 MACEs), higher aBMD at the lumbar spine, hip, whole body, and radius was associated with lower risk of MACE (hazard ratio [HR] = 0.44-0.71/SD, p < .025 to < .001). In 745 men having valid distal radius scan (47 MACEs), higher cortical density (Ct.BMD) and higher cortical thickness (Ct.Th^d ) were associated with lower risk of MACE. This risk was higher in men in the lowest quintile of cortical measures versus the four upper quintiles combined (Ct.BMD: HR = 2.12, 95% confidence interval [CI] 1.08-4.17, p < .025). Findings were similar in 779 men having valid distal tibia scan (48 MACEs). At both sites, higher estimated stiffness and higher failure load were associated with a lower risk of MACE. The risk of MACE was higher in men in the lowest quintile of the measures of bone strength versus four upper quintiles jointly (distal radius stiffness: HR = 2.46, 95% CI 1.27-4.74, p < .01). Similar results were obtained in 638 men without prior fragility fracture and in 689 men without ischemic heart disease at baseline. Thus, in older men followed prospectively for 8 years, higher aBMD, preserved cortical bone status, and higher estimated bone strength were associated with lower risk of MACE after adjustment for relevant confounders. © 2021 American Society for Bone and Mineral Research (ASBMR).

"Empowering" Cardiac Cells via Stem Cell Derived Mitochondrial Transplantation- Does Age Matter?

With cardiovascular diseases affecting millions of patients, new treatment strategies are urgently needed. The use of stem cell based approaches has been investigated during the last decades and promising effects have been achieved. However, the beneficial effect of stem cells has been found to being partly due to paracrine functions by alterations of their microenvironment and so an interesting field of research, the “stem- less” approaches has emerged over the last years using or altering the microenvironment, for example, via deletion of senescent cells, application of micro RNAs or by modifying the cellular energy metabolism via targeting mitochondria. Using autologous muscle-derived mitochondria for transplantations into the affected tissues has resulted in promising reports of improvements of cardiac functions in vitro and in vivo. However, since the targeted treatment group represents mainly elderly or otherwise sick patients, it is unclear whether and to what extent autologous mitochondria would exert their beneficial effects in these cases. Stem cells might represent better sources for mitochondria and could enhance the effect of mitochondrial transplantations. Therefore in this review we aim to provide an overview on aging effects of stem cells and mitochondria which might be important for mitochondrial transplantation and to give an overview on the current state in this field together with considerations worthwhile for further investigations.

Cardiac Adipose Tissue Contributes to Cardiac Repair: a Review

Cardiac adipose tissue is a metabolically active adipose tissue in close proximity to heart. Recent studies emphasized the benefits of cardiac adipose tissue in heart remodeling, such as reducing infarction size, enhancing neovascularization and regulating immune response, through a series of cellular mechanisms. In the present manuscript, we provide a comprehensive review regarding the role of cardiac adipose tissue in cardiac repair. We focus on different cardiac adipose tissues according to their distinguished anatomical structures. This review summarizes the latest evidence on the relationship between cardiac adipose tissue and cardiac repair. Cardiac adipose tissues (CAT) were systematically reviewed in the current manuscript which focused on the components of CAT, debates about cardiac adipose stem cells and their effect on heart.

Cortical Bone Derived Stem Cells Modulate Cardiac Fibroblast Response via miR-18a in the Heart After Injury

The adult heart following injury such as a myocardial infarction forms a fibrotic scar associated with transformation of resident cardiac fibroblasts into myofibroblast, accelerating cardiac remodeling and dysfunction. Cell therapies provide a novel direction for the enhancement of cardiac structure and function but remain poorly described in terms of the effect on resident cardiac fibroblasts. We have shown cortical bone derived stem cells (CBSCs) exhibit an ability to repair the heart after myocardial injury together with reduced scar formation. Nevertheless, whether CBSCs possess ability to modulate resident fibroblast response after myocardial injury remains untested.

Tailorable Hydrogel Improves Retention and Cardioprotection of Intramyocardial Transplanted Mesenchymal Stem Cells for the Treatment of Acute Myocardial Infarction in Mice

Background

Poor engraftment of intramyocardial stem cells limits their therapeutic efficiency against myocardial infarction (MI)‐induced cardiac injury. Transglutaminase cross‐linked Gelatin (Col‐Tgel) is a tailorable collagen‐based hydrogel that is becoming an excellent biomaterial scaffold for cellular delivery in vivo. Here, we tested the hypothesis that Col‐Tgel increases retention of intramyocardially‐injected stem cells, and thereby reduces post‐MI cardiac injury.

Methods and Results

Adipose‐derived mesenchymal stem cells (ADSCs) were co‐cultured with Col‐Tgel in a 3‐dimensional system in vitro, and Col‐Tgel encapsulated ADSCs were observed using scanning electron microscopy and confocal microscopy. Vitality, proliferation, and migration of co‐cultured ADSCs were evaluated. In addition, mice were subjected to MI and were intramyocardially injected with ADSCs, Col‐Tgel, or a combination thereof. ADSCs engraftment, survival, cardiac function, and fibrosis were assessed. In vitro MTT and Cell Counting Kit‐8 assays demonstrated that ADSCs survive and proliferate up to 4 weeks in the Col‐Tgel. In addition, MTT and transwell assays showed that ADSCs migrate outside the edge of the Col‐Tgel sphere. Furthermore, when compared with ADSCs alone, Col‐Tgel‐encapsulated ADSCs significantly enhanced the long‐term retention and cardioprotective effect of ADSCs against MI‐induced cardiac injury.

Conclusions

In the current study, we successfully established a 3‐dimensional co‐culture system using ADSCs and Col‐Tgel. The Col‐Tgel creates a suitable microenvironment for long‐term retention of ADSCs in an ischemic area, and thereby enhances their cardioprotective effects. Taken together, this study may provide an alternative biomaterial for stem cell‐based therapy to treat ischemic heart diseases.

Cardiac regenerative therapy: Many paths to repair

Cardiovascular disease remains the primary cause of death in the United States and in most nations worldwide, despite ongoing intensive efforts to promote cardiac health and treat heart failure. Replacing damaged myocardium represents perhaps the most promising treatment strategy, but also the most challenging given that the adult mammalian heart is notoriously resistant to endogenous repair. Cardiac regeneration following pathologic challenge would require proliferation of surviving tissue, expansion and differentiation of resident progenitors, or transdifferentiation of exogenously applied progenitor cells into functioning myocardium. Adult cardiomyocyte proliferation has been the focus of investigation for decades, recently enjoying a renaissance of interest as a therapeutic strategy for reversing cardiomyocyte loss due in large part to ongoing controversies and frustrations with myocardial cell therapy outcomes. The promise of cardiac cell therapy originated with reports of resident adult cardiac stem cells that could be isolated, expanded and reintroduced into damaged myocardium, producing beneficial effects in preclinical animal models. Despite modest functional improvements, Phase I clinical trials using autologous cardiac derived cells have proven safe and effective, setting the stage for an ongoing multi-center Phase II trial combining autologous cardiac stem cell types to enhance beneficial effects. This overview will examine the history of these two approaches for promoting cardiac repair and attempt to provide context for current and future directions in cardiac regenerative research.

Cortical bone-derived stem cell therapy reduces apoptosis after myocardial infarction

Ischemic heart diseases such as myocardial infarction (MI) are the largest contributors to cardiovascular disease worldwide. The resulting cardiac cell death impairs function of the heart and can lead to heart failure and death. Reperfusion of the ischemic tissue is necessary but causes damage to the surrounding tissue by reperfusion injury. Cortical bone stem cells (CBSCs) have been shown to increase pump function and decrease scar size in a large animal swine model of MI. To investigate the potential mechanism for these changes, we hypothesized that CBSCs were altering cardiac cell death after reperfusion. To test this, we performed TUNEL staining for apoptosis and antibody-based immunohistochemistry on tissue from Göttingen miniswine that underwent 90 min of lateral anterior descending coronary artery ischemia followed by 3 or 7 days of reperfusion to assess changes in cardiomyocyte and noncardiomyocyte cell death. Our findings indicate that although myocyte apoptosis is present 3 days after ischemia and is lower in CBSC-treated animals, myocyte apoptosis accounts for <2% of all apoptosis in the reperfused heart. In addition, nonmyocyte apoptosis trends toward decreased in CBSC-treated hearts, and although CBSCs increase macrophage and T-cell populations in the infarct region, the occurrence of apoptosis in CD45⁺ cells in the myocardium is not different between groups. From these data, we conclude that CBSCs may be influencing cardiomyocyte and noncardiomyocyte cell death and immune cell recruitment dynamics in the heart after MI, and these changes may account for some of the beneficial effects conferred by CBSC treatment.NEW & NOTEWORTHY The following research explores aspects of cell death and inflammation that have not been previously studied in a large animal model. In addition, apoptosis and cell death have not been studied in the context of cell therapy and myocardial infarction. In this article, we describe interactions between cell therapy and inflammation and the potential implications for cardiac wound healing.

Adiponectin determines farnesoid X receptor agonism-mediated cardioprotection against post-infarction remodelling and dysfunction

Aims

The farnesoid X receptor (FXR) is a member of the metabolic nuclear receptor superfamily that plays a critical regulatory role in cardiovascular physiology/pathology. However, the role of systemic FXR activation in the chronic phase in myocardial infarction (MI)-induced cardiac remodelling and dysfunction remains unclear. In this study, we aimed to elucidate the role of long-term FXR activation on post-MI cardiac remodelling and dysfunction.

Methods and results

Mice underwent either MI surgery or sham operation. At 1 week after MI, both sham and MI mice were gavaged with 25 mg/kg/d of a synthetic FXR agonist (GW4064) or a vehicle control for 7 weeks, and cardiac performance was assessed by consecutive echocardiography studies. Administration of GW4064 significantly increased left ventricular ejection fraction at 4 weeks and 8 weeks after MI (both P < 0.01). Moreover, GW4064 treatment increased angiogenesis and mitochondrial biogenesis, reduced cardiomyocyte loss and inflammation, and ameliorated cardiac remodelling as evidenced by heart weight, lung weight, atrial natriuretic peptide/brain natriuretic peptide levels, and myocardial fibrosis at 8 weeks post-MI. At the molecular level, GW4064 significantly increased FXR mRNA expression and transcriptional activity in heart tissue. Moreover, over-expression of myocardial FXR failed to exert significant cardioprotection in vivo, indicating that GW4064 improved post-MI heart remodelling and function independent of myocardial FXR expression/activity. Among the four down-stream soluble molecules of FXR, plasma adiponectin was most significantly increased by GW4064. In cultured adipocytes, GW4064 increased mRNA levels and protein expression of adiponectin. Conditioned medium of GW4064-treated adipocytes activated AMPK-PGC-1α signalling and reduced hypoxia-induced cardiomyocyte apoptosis, all of which were attenuated by an adiponectin neutralizing anti-body. More importantly, when knocking-out adiponectin in mice, the cardioprotective effects of GW4064 were attenuated.

Conclusions

We are the first to show that FXR agonism ameliorated post-MI cardiac dysfunction and remodelling by stimulating adiponectin secretion. Thus, we demonstrated that FXR agonism is a potential therapeutic strategy in post-MI heart failure.

Follistatin-like 1 protects mesenchymal stem cells from hypoxic damage and enhances their therapeutic efficacy in a mouse myocardial infarction model

BACKGROUND

Cell therapy remains the most promising approach against ischemic heart injury. However, poor survival of engrafted cells in ischemic sites diminishes its therapeutic efficacy. Follistatin-like 1 (Fstl1) is documented as a novel pro-survival cardiokine for cardiomyocytes, and it is protective during ischemic heart injury. In the present study, we characterize the potential of Fstl1 as an effective strategy to enhance hypoxia resistance of donor cells and optimize stem cell-based therapy.

METHODS

Murine bone marrow-derived mesenchymal stem cells (MSCs) were expanded in monolayer culture and characterized by flow cytometry. MSCs were subjected to hypoxia to mimic cardiac ischemic environment. Expression of Fstl1 was monitored 0, 24, and 48 h following hypoxia. Constitutive expression of Fstl1 in MSCs was achieved by lentivirus-mediated Fstl1 overexpression. Genetically modified MSCs were further collected for cell death and proliferation assay following 48 h of hypoxic treatment. Acute myocardial infarction (MI) model was created by ligating the left anterior descending coronary artery, while control MSCs (MSCs-mCherry) or Fstl1-overexpressing MSCs (MSCs-Fstl1) were injected into the peri-infarct zone simultaneously. Subsequently, retention of the donor cells was evaluated on post-therapy 1, 3, & 7 days. Finally, myocardial function, infarct size, inflammation, and neovascularization of the infarcted hearts were calculated thereafter.

RESULTS

Expression of Fstl1 in hypoxic MSCs declines dramatically in a time-dependent manner. In vitro study further demonstrated that Fstl1 promotes survival and proliferation of hypoxic MSCs. Moreover, Fstl1 significantly prolongs MSC survival/retention after implantation. Finally, transplantation with Fstl1-overexpressing MSCs significantly improves post-MI cardiac function by limiting scar formation, reducing inflammatory response, and enhancing neovascularization.

CONCLUSIONS

Our results suggest Fstl1 is an intrinsic cardiokine promoting survival and proliferation of MSCs, thereby optimizing their engraftment and therapeutic efficacy during cell therapy.

Resistin promotes cardiac homing of mesenchymal stem cells and functional recovery after myocardial ischemia-reperfusion via the ERK1/2-MMP-9 pathway

Stem cell therapy is a potentially effective and promising treatment for ischemic heart disease. Resistin, a type of adipokine, has been found to bind to adipose-derived mesenchymal stem cells (ADSCs). However, the effects of resistin on cardiac homing by ADSCs and on ADSC-mediated cardioprotective effects have not been investigated. ADSCs were obtained from enhanced green fluorescent protein transgenic mice. C57BL/6J mice were subjected to myocardial ischemia-reperfusion (I/R) or sham operations. Six hours after the I/R operation, mice were intravenously injected with resistin-treated ADSCs (ADSC-resistin) or vehicle-treated ADSCs (ADSC-vehicle). Cardiac homing by ADSCs and cardiomyocyte apoptosis were investigated 3 days after I/R. Cardiac function, fibrosis, and angiogenesis were evaluated 4 wk after I/R. Cellular and molecular mechanisms were investigated in vitro using cultured ADSCs. Both immunostaining and flow cytometric experiments showed that resistin treatment promoted ADSC myocardial homing 3 days after intravenous injection. Echocardiographic experiments showed that ADSC-resistin, but not ADSC-vehicle, significantly improved left ventricular ejection fraction. ADSC-resistin transplantation significantly mitigated I/R-induced fibrosis and reduced atrial natriuretic peptide/brain natriuretic peptide mRNA expression. In addition, cardiomyocyte apoptosis was reduced, whereas angiogenesis was increased by ADSC-resistin treatment. At the cellular level, resistin promoted ADSC proliferation and migration but did not affect H2O2-induced apoptosis. Molecular experiments identified the ERK1/2-matrix metalloproteinase-9 pathway as a key component mediating the effects of resistin on ADSC proliferation and migration. These results demonstrate that resistin can promote homing of injected ADSCs into damaged heart tissue and stimulate functional recovery, an effect mediated through the ERK1/2 signaling pathway and matrix metalloproteinase-9.

NEW & NOTEWORTHY First, intravenous injection of adipose-derived mesenchymal stem cells (ADSCs) treated with resistin significantly increased angiogenesis and reduced myocardial apoptosis and fibrosis in a murine model of ischemia-reperfusion, resulting in improved cardiac performance. Second, resistin treatment significantly increased myocardial homing of intravenously delivered ADSCs. Finally, the ERK1/2-matrix metalloproteinase 9 pathway contributed to the higher proliferative and migratory capacities of ADSCs treated with resistin.

New Paradigms in Cell Therapy: Repeated Dosing, Intravenous Delivery, Immunomodulatory Actions, and New Cell Types

Perhaps the most important advance in the field of cell therapy for heart disease has been the recognition that all stem/progenitor cells (both adult and embryonic) fail to engraft in the heart to a significant extent and thus work via paracrine mechanisms. This fundamental advance has led to 4 new paradigms that are discussed in this review and that may importantly shape, or even revolutionize, the future of the field: (1) repeated cell therapy, (2) intravenous cell therapy, (3) immunomodulatory actions of cell therapy, and (4) new cell types. Because virtually all of our current knowledge of cell therapy is predicated on the effects of a single cell dose, the idea that the full therapeutic effects of a cell product require repeated doses is disruptive and has far-reaching implications. For example, inadequate dosing (single-dose protocols) may be responsible, at least in part, for the borderline or disappointing results obtained to date in clinical trials; furthermore, future studies (both preclinical and clinical) may need to incorporate repeated cell administrations. Another disruptive idea, supported by emerging preclinical and clinical evidence, is that intravenously injected cells can produce beneficial effects on the heart, presumably via release of paracrine factors in extracardiac organs or endocrine factors into the systemic circulation. Intravenous administration would obviate the need for direct delivery of cells to the heart, making cell therapy simpler, cheaper, safer, more scalable, and more broadly available, even on an outpatient basis. Although the mechanism of action of cell therapy remains elusive, there is compelling in vitro evidence that transplanted cells modulate the function of various immune cell types via release of paracrine factors, such as extracellular vesicles, although in vivo evidence is still limited. Investigation of the new paradigms reviewed herein should be a top priority because it may profoundly transform cell therapy and finally make it a reality.

C1q/Tumor Necrosis Factor-Related Protein-9 Regulates the Fate of Implanted Mesenchymal Stem Cells and Mobilizes Their Protective Effects Against Ischemic Heart Injury via Multiple Novel Signaling Pathways

BACKGROUND

Cell therapy remains the most promising approach against ischemic heart injury. However, the poor survival of engrafted stem cells in the ischemic environment limits their therapeutic efficacy for cardiac repair after myocardial infarction. CTRP9 (C1q/tumor necrosis factor-related protein-9) is a novel prosurvival cardiokine with significantly downregulated expression after myocardial infarction. Here we tested a hypothesis that CTRP9 might be a cardiokine required for a healthy microenvironment promoting implanted stem cell survival and cardioprotection.

METHODS

Mice were subjected to myocardial infarction and treated with adipose-derived mesenchymal stem cells (ADSCs, intramyocardial transplantation), CTRP9, or their combination. Survival, cardiac remodeling and function, cardiomyocytes apoptosis, and ADSCs engraftment were evaluated. Whether CTRP9 directly regulates ADSCs function was determined in vitro. Discovery-drive approaches followed by cause-effect analysis were used to uncover the molecular mechanisms of CTRP9.

RESULTS

Administration of ADSCs alone failed to exert significant cardioprotection. However, administration of ADSCs in addition to CTRP9 further enhanced the cardioprotective effect of CTRP9 (P<0.05 or P<0.01 versus CTRP9 alone), suggesting a synergistic effect. Administration of CTRP9 at a dose recovering physiological CTRP9 levels significantly prolonged ADSCs retention/survival after implantation. Conversely, the number of engrafted ADSCs was significantly reduced in the CTRP9 knockout heart. In vitro study demonstrated that CTRP9 promoted ADSCs proliferation and migration, and it protected ADSCs against hydrogen peroxide-induced cellular death. CTRP9 enhances ADSCs proliferation/migration by extracellular regulated protein kinases (ERK)1/2-matrix metallopeptidase 9 signaling and promotes antiapoptotic/cell survival via ERK-nuclear factor erythroid-derived 2-like 2/antioxidative protein expression. N-cadherin was identified as a novel CTRP9 receptor mediating ADSCs signaling. Blockade of either N-cadherin or ERK1/2 completely abolished the previously noted CTRP9 effects. Although CTRP9 failed to promote ADSCs cardiogenic differentiation, CTRP9 promotes superoxide dismutase 3 expression and secretion from ADSCs, protecting cardiomyocytes against oxidative stress-induced cell death.

CONCLUSIONS

We provide the first evidence that CTRP9 promotes ADSCs proliferation/survival, stimulates ADSCs migration, and attenuates cardiomyocyte cell death by previously unrecognized signaling mechanisms. These include binding with N-cadherin, activation of ERK-matrix metallopeptidase 9 and ERK-nuclear factor erythroid-derived 2-like 2 signaling, and upregulation/secretion of antioxidative proteins. These results suggest that CTRP9 is a cardiokine critical in maintaining a healthy microenvironment facilitating stem cell engraftment in infarcted myocardial tissue, thereby enhancing stem cell therapeutic efficacy.

Mammalian MSC from selected species: Features and applications

Mesenchymal stromal/stem cells (MSC) are promising candidates for cellular therapy of different diseases in humans and in animals. Following the guidelines of the International Society for Cell Therapy, human MSC may be identified by expression of a specific panel of cell surface markers (CD105+, CD73+, CD90+, CD34-, CD14-, or CD11b-, CD79- or CD19-, HLA-DR-). In addition, multiple differentiation potential into at least the osteogenic, adipogenic, and chondrogenic lineage is a main criterion for MSC definition. Human MSC and MSC of a variety of mammals isolated from different tissues meet these criteria. In addition to the abovementioned, they express many more cell surface markers. Yet, these are not uniquely expressed by MSC. The gross phenotypic appearance like marker expression and differentiation potential is similar albeit not identical for MSC from different tissues and species. Similarly, MSC may feature different biological characteristics depending on the tissue source and the isolation and culture procedures. Their versatile biological qualities comprising immunomodulatory, anti-inflammatory, and proregenerative capacities rely largely on the migratory and secretory capabilities of MSC. They are attracted to sites of tissue lesion and secrete factors to promote self-repair of the injured tissue. This is a big perspective for clinical MSC applications in both veterinary and human medicine. Phase I/II clinical trials have been initiated to assess safety and feasibility of MSC therapies in acute and chronic disease settings. Yet, since the mode of MSC action in a specific disease environment is still unknown at large, it is mandatory to unravel the response of MSC from a given source onto a specific disease environment in suitable animal models prior to clinical applications. © 2017 International Society for Advancement of Cytometry.

Cortical Bone Stem Cell Therapy Preserves Cardiac Structure and Function After Myocardial Infarction

RATIONALE

Cortical bone stem cells (CBSCs) have been shown to reduce ventricular remodeling and improve cardiac function in a murine myocardial infarction (MI) model. These effects were superior to other stem cell types that have been used in recent early-stage clinical trials. However, CBSC efficacy has not been tested in a preclinical large animal model using approaches that could be applied to patients.

OBJECTIVE

To determine whether post-MI transendocardial injection of allogeneic CBSCs reduces pathological structural and functional remodeling and prevents the development of heart failure in a swine MI model.

METHODS AND RESULTS

Female Göttingen swine underwent left anterior descending coronary artery occlusion, followed by reperfusion (ischemia-reperfusion MI). Animals received, in a randomized, blinded manner, 1:1 ratio, CBSCs (n=9; 2×10⁷ cells total) or placebo (vehicle; n=9) through NOGA-guided transendocardial injections. 5-ethynyl-2'deoxyuridine (EdU)-a thymidine analog-containing minipumps were inserted at the time of MI induction. At 72 hours (n=8), initial injury and cell retention were assessed. At 3 months post-MI, cardiac structure and function were evaluated by serial echocardiography and terminal invasive hemodynamics. CBSCs were present in the MI border zone and proliferating at 72 hours post-MI but had no effect on initial cardiac injury or structure. At 3 months, CBSC-treated hearts had significantly reduced scar size, smaller myocytes, and increased myocyte nuclear density. Noninvasive echocardiographic measurements showed that left ventricular volumes and ejection fraction were significantly more preserved in CBSC-treated hearts, and invasive hemodynamic measurements documented improved cardiac structure and functional reserve. The number of EdU⁺ cardiac myocytes was increased in CBSC- versus vehicle- treated animals.

CONCLUSIONS

CBSC administration into the MI border zone reduces pathological cardiac structural and functional remodeling and improves left ventricular functional reserve. These effects reduce those processes that can lead to heart failure with reduced ejection fraction.

Comparative biology of tissue repair, regeneration and aging

The Symposium on the Comparative Biology of Tissue Repair, Regeneration and Aging, held 26 June to 28 June 2015 at the MDI Biological Laboratory in Salisbury Cove, Maine, brought together a diverse group of biologists with a common interest in understanding why regenerative capacity varies among animal species, why it is progressively lost in senescence, and how answers obtained from studies that address those questions might be applied in regenerative medicine.

Empowering Adult Stem Cells for Myocardial Regeneration V2.0: Success in Small Steps

Much has changed since our survey of the landscape for myocardial regeneration powered by adult stem cells 4 years ago.(1) The intervening years since that first review has witnessed an explosive expansion of studies that advance both understanding and implementation of adult stem cells in promoting myocardial repair. Painstaking research from innumerable laboratories throughout the world is prying open doors that may lead to restoration of myocardial structure and function in the wake of pathological injury. This global effort has produced deeper mechanistic comprehension coupled with an evolving appreciation for the complexity of myocardial regeneration in the adult context. Undaunted by both known and (as yet) unknown challenges, pursuit of myocardial regenerative medicine mediated by adult stem cell therapy has gathered momentum fueled by tantalizing clues and visionary goals. This concise review takes a somewhat different perspective than our initial treatise, taking stock of the business sector that has become an integral part of the field while concurrently updating state of affairs in cutting edge research. Looking retrospectively at advancement over the years as all reviews eventually must, the fundamental lesson to be learned is best explained by Jonatan Mårtensson: "Success will never be a big step in the future. Success is a small step taken just now."