Human Bone Marrow-Derived CD133+ Cells Delivered to a Collagen Patch on Cryoinjured Rat Heart Promote Angiogenesis and Arteriogenesis

Targeting Myocardial Fibrosis—A Magic Pill in Cardiovascular Medicine?

Fibrosis, characterized by an excessive accumulation of extracellular matrix, has long been seen as an adaptive process that contributes to tissue healing and regeneration. More recently, however, cardiac fibrosis has been shown to be a central element in many cardiovascular diseases (CVDs), contributing to the alteration of cardiac electrical and mechanical functions in a wide range of clinical settings. This paper aims to provide a comprehensive review of cardiac fibrosis, with a focus on the main pathophysiological pathways involved in its onset and progression, its role in various cardiovascular conditions, and on the potential of currently available and emerging therapeutic strategies to counteract the development and/or progression of fibrosis in CVDs. We also emphasize a number of questions that remain to be answered, and we identify hotspots for future research.

Premobilization of CD133+ progenitors is associated with attenuated inflammation-induced pulmonary dysfunction following extracorporeal circulation in mice

OBJECTIVES

Progenitor cells mobilized by granulocyte colony-stimulating factor (G-CSF) have been shown to lessen acute kidney injury induced by extracorporeal circulation (ECC). Both acute kidney injury and lung injury are characterized by endothelial dysfunction. Our goal was to examine whether and how G-CSF-mobilized progenitors with endothelial capacity may help mitigate ECC-induced pulmonary dysfunction.

METHODS

G-CSF (10 μg/kg/day) was administered subcutaneously to C57BL/6 mice before or at the initiation of the ECC process, after which lung injury was assessed by measuring neutrophils in the fluid from bronchoalveolar lavage and determining the pathological score in lung tissue. CD133+ progenitors were isolated and injected into C57BL/6 mice before ECC in vivo. We incubated the CD133+ cells with pulmonary monocytes or neutrophils isolated from naïve mice in vitro.

RESULTS

Pretreatment with G-CSF for 2 days significantly decreased the number of neutrophils in the bronchoalveolar lavage fluid, and the pathological score (P < 0.01; n = 5) improved the PaO2/FiO2 ratio [193.4 ± 12.7 (ECC without G-CSF) vs 305.6 ± 22.6 mmHg (ECC with G-CSF); P = 0.03, n = 5] and suppressed neutrophil elastase and tumour necrosis factor-α levels in the circulation; we also observed increases in both circulating and pulmonary populations of CD133+ progenitors. Similar effects were observed in animals pretreated with CD133+ progenitors instead of G-CSF before ECC. The majority of CD133+/CD45- and CD133+/CD45+ progenitors were mobilized in the lung and in the circulation, respectively. Incubating CD133+ progenitors with neutrophils or pulmonary monocytes blocked lipopolysaccharide-induced release of inflammatory factors.

CONCLUSIONS

Our results suggest that pretreatment of G-CSF attenuates ECC-induced pulmonary dysfunction through inhibiting the inflammatory response in lung tissue and in the circulation with associated premobilization of CD133+ progenitors.

Cardiac fibrosis: potential therapeutic targets

Cardiovascular disease is a leading cause of mortality in the world and is exacerbated by the presence of cardiac fibrosis, defined by the accumulation of noncontractile extracellular matrix proteins. Cardiac fibrosis is directly linked to cardiac dysfunction and increased risk of arrhythmia. Despite its prevalence, there is a lack of efficacious therapies for inhibiting or reversing cardiac fibrosis, largely due to the complexity of the cell types and signaling pathways involved. Ongoing research has aimed to understand the mechanisms of cardiac fibrosis and develop new therapies for treating scar formation. Major approaches include preventing the formation of scar tissue and replacing fibrous tissue with functional cardiomyocytes. While targeting the renin-angiotensin-aldosterone system is currently used as the standard line of therapy for heart failure, there has been increased interest in inhibiting the transforming growth factor-β signaling pathway due its established role in cardiac fibrosis. Significant advances in cell transplantation therapy and biomaterials engineering have also demonstrated potential in regenerating the myocardium. Novel techniques, such as cellular direct reprogramming, and molecular targets, such as noncoding RNAs and epigenetic modifiers, are uncovering novel therapeutic options targeting fibrosis. This review provides an overview of current approaches and discuss future directions for treating cardiac fibrosis.

Fibrosis in tissue engineering and regenerative medicine: treat or trigger?

Fibrosis is a life-threatening pathological condition resulting from a dysfunctional tissue repair process. There is no efficient treatment and organ transplantation is in many cases the only therapeutic option. Here we review tissue engineering and regenerative medicine (TERM) approaches to address fibrosis in the cardiovascular system, the kidney, the lung and the liver. These strategies have great potential to achieve repair or replacement of diseased organs by cell- and material-based therapies. However, paradoxically, they might also trigger fibrosis. Cases of TERM interventions with adverse outcome are also included in this review. Furthermore, we emphasize the fact that, although organ engineering is still in its infancy, the advances in the field are leading to biomedically relevant in vitro models with tremendous potential for disease recapitulation and development of therapies. These human tissue models might have increased predictive power for human drug responses thereby reducing the need for animal testing.

Improved Left Ventricular Aneurysm Repair with Cell- and Cytokine-Seeded Collagen Patches

Background

Engineered heart tissues (EHTs) present a promising alternative to current materials for surgical ventricular restoration (SVR); however, the clinical application remains limited by inadequate vascularization postimplantation. Moreover, a suitable and economic animal model for primary screening is another important issue.

Methods

Recently, we used 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride chemistry (EDC) to initiate a strengthened, cytokine-conjugated collagenous platform with a controlled degradation speed. In vitro, the biomaterial exhibited an enhanced mechanical strength maintaining a porous ultrastructure, and the constant release of cytokines promoted the proliferation of seeded human mesenchymal stem cells (hMSCs). In vivo, with the hMSC-seeded, cytokine-immobilized patch (MSCs + GF patch), we performed modified SVR for rats with left ventricular aneurysm postmyocardial infarction (MI). Overall, the rats that underwent modified SVR lost less blood and had lower mortality. After 4 weeks, the rats repaired with this cell-seeded, cytokine-immobilized patch presented preserved cardiac function, beneficial morphology, enhanced cell infiltration, and functional vessel formation compared with the cytokine-free (MSC patch), cell-free (GF patch), or blank controls (EDC patch). Furthermore, the degradable period of the collagen patch in vivo extended up to 3 months after EDC treatment.

Conclusions

EDC may substantially modify collagen scaffold and provide a promising and practical biomaterial for SVR.

Construction of a vascularized hydrogel for cardiac tissue formation in a porcine model

Replacing cardiac tissues lost to myocardial infarction remains a therapeutic goal for regenerative therapy in recovering cardiac function. We assessed the feasibility of constructing a macrosized human cardiac tissue construct using pluripotent stem cell-derived cardiomyocytes or control fibroblasts infused fibrin/collagen hydrogel and performed ectopic implantation in peripheral vascular system of a porcine model for 3 weeks. Finally, an optimized vascularized cardiac construct was explanted and grafted onto porcine myocardium for 2 weeks. Myocardial-grafted human cardiac constructs showed a nascent tissue-like organization with aligned cardiomyocytes within the remodelled collagen matrix. Nevertheless, no significant changes in intraconstruct density of cardiomyocytes were observed in the myocardial-grafted constructs (human embryonic stem cell [hESC]-derived cardiomyocyte [n = 4]: 70.5 ± 22.8 troponin I⁺ cardiomyocytes/high power field [HPF]) as compared to peripherally implanted constructs (hESC-derived cardiomyocyte [n = 4]: 59.0 ± 19.6 troponin I⁺ cardiomyocytes/HPF; human induced pluripotent stem cell-derived cardiomyocyte [n = 3]: 50.9 ± 8.5 troponin I⁺ cardiomyocytes/HPF, p = ns). However, the myocardial-grafted constructs showed an increased in neovascularization (194.4 ± 24.7 microvessels/mm² tissue, p < .05), microvascular maturation (82.8 ± 24.7 mature microvessels/mm² , p < .05), and tissue-like formation whereas the peripherally implanted constructs of hESC-derived cardiomyocyte (168.3 ± 98.2 microvessels/mm² tissue and 68.1 ± 33.4 mature microvessels/mm² ) and human induced pluripotent stem cell-derived cardiomyocyte (86.8 ± 57.4 microvessels/mm² tissue and 22.0 ± 32.7 mature microvessels/mm² ) were not significantly different in vascularized response when compared to the control human fibroblasts (n = 3) constructs (65.6 ± 34.1 microvessels/mm² tissue and 30.7 ± 20.7 mature microvessels/mm² ). We presented results on technical feasibility and challenges of grafting vascularized centimetre-sized human cardiac construct that may spur novel approaches in cardiac tissue replacement strategy.

The Rapidly Evolving Concept of Whole Heart Engineering

Whole heart engineering represents an incredible journey with as final destination the challenging aim to solve end-stage cardiac failure with a biocompatible and living organ equivalent. Its evolution started in 2008 with rodent organs and is nowadays moving closer to clinical application thanks to scaling-up strategies to human hearts. This review will offer a comprehensive examination on the important stages to be reached for the bioengineering of the whole heart, by describing the approaches of organ decellularization, repopulation, and maturation so far applied and the novel technologies of potential interest. In addition, it will carefully address important demands that still need to be satisfied in order to move to a real clinical translation of the whole bioengineering heart concept.

The Light and Shadow of Senescence and Inflammation in Cardiovascular Pathology and Regenerative Medicine

Recent epidemiologic studies evidence a dramatic increase of cardiovascular diseases, especially associated with the aging of the world population. During aging, the progressive impairment of the cardiovascular functions results from the compromised tissue abilities to protect the heart against stress. At the molecular level, in fact, a gradual weakening of the cellular processes regulating cardiovascular homeostasis occurs in aging cells. Atherosclerosis and heart failure are particularly correlated with aging-related cardiovascular senescence, that is, the inability of cells to progress in the mitotic program until completion of cytokinesis. In this review, we explore the intrinsic and extrinsic causes of cellular senescence and their role in the onset of these cardiovascular pathologies. Additionally, we dissect the effects of aging on the cardiac endogenous and exogenous reservoirs of stem cells. Finally, we offer an overview on the strategies of regenerative medicine that have been advanced in the quest for heart rejuvenation.

Tissue Engineering Strategies for Myocardial Regeneration: Acellular Versus Cellular Scaffolds?

Heart disease remains one of the leading causes of death in industrialized nations with myocardial infarction (MI) contributing to at least one fifth of the reported deaths. The hypoxic environment eventually leads to cellular death and scar tissue formation. The scar tissue that forms is not mechanically functional and often leads to myocardial remodeling and eventual heart failure. Tissue engineering and regenerative medicine principles provide an alternative approach to restoring myocardial function by designing constructs that will restore the mechanical function of the heart. In this review, we will describe the cellular events that take place after an MI and describe current treatments. We will also describe how biomaterials, alone or in combination with a cellular component, have been used to engineer suitable myocardium replacement constructs and how new advanced culture systems will be required to achieve clinical success.

Biomaterial-Enhanced Cell and Drug Delivery: Lessons Learned in the Cardiac Field and Future Perspectives

Heart failure is a significant clinical issue. It is the cause of enormous healthcare costs worldwide and results in significant morbidity and mortality. Cardiac regenerative therapy has progressed considerably from clinical and preclinical studies delivering simple suspensions of cells, macromolecule, and small molecules to more advanced delivery methods utilizing biomaterial scaffolds as depots for localized targeted delivery to the damaged and ischemic myocardium. Here, regenerative strategies for cardiac tissue engineering with a focus on advanced delivery strategies and the use of multimodal therapeutic strategies are reviewed.

Cellular cardiomyoplasty into infracted swine's hearts by retrograde infusion through the venous coronary sinus: An experimental study

OBJECTIVES

The aim was to create a model of myocardial infarction with a borderline myocardial impairment which would enable evaluation of the retrograde cellular cardiomyoplasty through the venous coronary sinus in a large animal model.

MATERIALS AND METHODS

Fifteen (study group) and 10 juvenile farm pigs (control group) underwent distal left anterior descending artery ligation. One month later the study group animals underwent sternotomy and a murine myoblastic line C2-C12 was injected at a constant pressure of 30mmHg, into the coronary sinus. Thirty days later all animals that survived from both groups underwent transthoracic echocardiography and 99Tc scintigraphy and were later euthanized and specimens were taken for microscopic evaluation.

RESULTS

Cardiac output decreased significantly after ligation (p<0.001) and increased significantly after cardiomyoplasty (p<0.001). In all animals, the surgical induction of myocardial infarction caused a marked decline in the echocardiographic values of cardiac function; however, the cardiac function and dimensions were significantly improved in the study group after cardiomyoplasty versus the control group. All animals undergoing cardiomyoplasty demonstrated a significant reduction of the perfusion deficit in the left anterior descending artery territory, instead such data remained unchanged in the control group. The histological examination demonstrated the engrafted myoblasts could be distinguished from the activated fibroblasts in the scar tissue because they never showed any signs of collagen secretion and fiber buildup.

CONCLUSIONS

In conclusion, the venous retrograde delivery route through the coronary sinus is safe and effective, providing a significant improvement in function and viability.

Myocardial infarction: stem cell transplantation for cardiac regeneration

It is estimated that by 2030, almost 23.6 million people will perish from cardiovascular disease, according to the WHO. The review discusses advances in stem cell therapy for myocardial infarction, including cell sources, methods of differentiation, expansion selection and their route of delivery. Skeletal muscle cells, hematopoietic cells and mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs)-derived cardiomyocytes have advanced to the clinical stage, while induced pluripotent cells (iPSCs) are yet to be considered clinically. Delivery of cells to the sites of injury and their subsequent retention is a major issue. The development of supportive scaffold matrices to facilitate stem cell retention and differentiation are analyzed. The review outlines clinical translation of conjugate stem cell-based cellular therapeutics post-myocardial infarction.

Ex vivo Akt/HO-1 gene therapy to human endothelial progenitor cells enhances myocardial infarction recovery

The aim of this study was to evaluate the overexpression of genes central to cell survival and angiogenesis to enhance the function of human late outgrowth endothelial progenitor cells (EPCs) and their utility for infarct recovery. Ischemic myocardial injury creates a hostile microenvironment, which is characterized by hypoxia, oxidative stress, and inflammation. The infarct microenvironment prevents adhesion, survival, and integration of cell transplants that promote neovascularization. EPCs are dysfunctional as a result of risk factors in cardiovascular patients. Protein kinase B (Akt) and heme-oxygenase-1 (HO-1) are intracellular proteins that play an important role in angiogenesis and cell survival. Late outgrowth EPCs transduced ex vivo with Akt and HO-1 demonstrate improved adhesion to extracellular matrix, improved migration toward human cardiomyocytes, and an improved paracrine profile under stress. Enhanced late outgrowth EPCs reduce the tumor necrosis factor-α (TNF-α) burden both in vitro and in vivo, attenuating nuclear factor-κB (NF-κB) activity and promoting cell survival. Akt and HO-1 enhance late outgrowth EPC neovascularization, resulting in improved cardiac performance and reduced negative remodeling after myocardial infarction in nude mice. Alteration of the infarct microenvironment through gene modification of human late outgrowth EPCs enhances the function and integration of transplanted cells for restoration of cardiac function.

Biomaterial applications in cardiovascular tissue repair and regeneration

Cardiovascular disease physically damages the heart, resulting in loss of cardiac function. Medications can help alleviate symptoms, but it is more beneficial to treat the root cause by repairing injured tissues, which gives patients better outcomes. Besides heart transplants, cardiac surgeons use a variety of methods for repairing different areas of the heart such as the ventricular septal wall and valves. A multitude of biomaterials are used in the repair and replacement of impaired heart tissues. These biomaterials fall into two main categories: synthetic and natural. Synthetic materials used in cardiovascular applications include polymers and metals. Natural materials are derived from biological sources such as human donor or harvested animal tissues. A new class of composite materials has emerged to take advantage of the benefits of the strengths and minimize the weaknesses of both synthetic and natural materials. This article reviews the current and prospective applications of biomaterials in cardiovascular therapies.

Endothelial progenitor cells: therapeutic perspective for ischemic stroke

Endothelial progenitor cells (EPCs), which can be cultured in vitro from mononuclear cells in peripheral blood or bone marrow, express both hematopoietic stem cell and endothelial cell markers on their surface. They are believed to participate in endothelial repair and postnatal angiogenesis due to their abilities of differentiating into endothelial cells and secreting protective cytokines and growth factors. Mounting evidence suggests that circulating EPCs are reduced and dysfunctional in various diseases including hypertension, diabetes, coronary heart disease, and ischemic stroke. Therefore, EPCs have been documented to be a potential biomarker for vascular diseases and a hopeful candidate for regenerative medicine. Ischemic stroke, as the major cause of disability and death, still has limited therapeutics based on the approaches of vascular recanalization or neuronal protection. Emerging evidence indicates that transplantation of EPCs is beneficial for the recovery of ischemic cerebral injury. EPC-based therapy could open a new avenue for ischemic cerebrovascular disease. Currently, clinical trials for evaluating EPC transfusion in treating ischemic stroke are underway. In this review, we summarize the general conceptions and the characteristics of EPCs, and highlight the recent research developments on EPCs. More importantly, the rationale, perspectives, and strategies for using them to treat ischemic stroke will be discussed.

Local Transplantation of Ex Vivo Expanded Bone Marrow-Derived CD34-Positive Cells Accelerates Fracture Healing

Transplantation of bone marrow (BM) CD34+ cells, an endothelial/hematopoietic progenitor-enriched cell population, has shown therapeutic efficiency in the treatment of ischemic diseases enhancing neovascularization. However, the number of CD34+ cells obtained from bone marrow is not sufficient for routine clinical application. To overcome this issue, we developed a more efficient and clinically applicable CD34+ cell expansion method. Seven-day ex vivo expansion culture of BM CD34+ cells with a cocktail of five growth factors containing VEGF, SCF, IL-6, Flt-3 ligand, and TPO resulted in reproducible more than 20-fold increase in cell number. The favorable effect of the local transplantation of culture expanded (cEx)-BM CD34+ cells on rat unhealing fractures was equivalent or higher than that of nonexpanded (fresh) BM CD34+ cells exhibiting sufficient therapeutic outcome with frequent vasculogenic/osteogenic differentiation of transplanted cEx-BM CD34+ cells and fresh BM CD34+ cells as well as intrinsic enhancement of angiogenesis/osteogenesis at the treated fracture sites. Specifically, cEx-BM CD34+ cell treatment demonstrated the best blood flow recovery at fracture sites compared with the nonexpanded BM CD34+ cells. In vitro, cEx-BM CD34+ cells showed higher colony/tube-forming capacity than nonexpanded BM CD34+ cells. Both cells demonstrated differentiation potential into osteoblasts. Since fresh BM CD34+ cells can be easily collected from fracture sites at the time of primary operation and stored for future use, autologous cEx-BM CD34+ cell transplantation would be not only a simple but also a promising therapeutic strategy for unhealing fractures in the field of orthopedic trauma surgery.

Cardiac stem cell therapy: stemness or commitment?

Cardiac stem cell therapy to promote engraftment of de novo beating cardiac muscle cells in cardiomyopathies could potentially improve clinical outcomes for many patients with congestive heart failure. Clinical trials carried out over the last decade for cardiac regeneration have revealed inadequacy of current approaches in cell therapy. Chief among them is the choice of stem cells to achieve the desired outcomes. Initial enthusiasm of adult bone marrow stems cells for myocyte regeneration has largely been relegated to paracrine-driven, donor cell-independent, endogenous cardiac repair. However, true functional restoration in heart failure is likely to require considerable myocyte replacement. In order to match stem cell application to various clinical scenarios, we review the necessity to preprime stem cells towards cardiac fate before myocardial transplantation and if these differentiated stem cells could confer added advantage over current choice of undifferentiated stem cells. We explore differentiation ability of various stem cells to cardiac progenitors/cardiomyocytes and compare their applicability in providing targeted recovery in light of current clinical challenges of cell therapy.

Hematopoietic stem cell development, niches, and signaling pathways

Hematopoietic stem cells (HSCs) play a key role in hematopoietic system that functions mainly in homeostasis and immune response. HSCs transplantation has been applied for the treatment of several diseases. However, HSCs persist in the small quantity within the body, mostly in the quiescent state. Understanding the basic knowledge of HSCs is useful for stem cell biology research and therapeutic medicine development. Thus, this paper emphasizes on HSC origin, source, development, the niche, and signaling pathways which support HSC maintenance and balance between self-renewal and proliferation which will be useful for the advancement of HSC expansion and transplantation in the future.

Biomaterials for the treatment of myocardial infarction: a 5-year update

The first review on biomaterials for the treatment of myocardial infarction (MI) was written in 2006. In the last 5 years, the general approaches for biomaterial treatment of MI and subsequent left ventricular remodeling remain the same, namely, left ventricular restraints, epicardial patches, and injectable therapies. Nonetheless, there have been significant developments in this field, including advancement of biomaterial therapies to large animal pre-clinical studies and, more recently, to clinical trials. This review focuses on the progress made in the field of cardiac biomaterial treatments for MI over the last 5 years.

Inhibition of collagen deposit in obstructed rat bladder outlet by transplantation of superparamagnetic iron oxide-labeled human mesenchymal stem cells as monitored by molecular magnetic resonance imaging (MRI)

Bladder outlet obstruction (BOO) caused by collagen deposit is one of the most common problems in elderly males. The present study is to investigate if human mesenchymal stem cells (MSCs) are capable of inhibiting collagen deposition and improve cystometric parameters in bladder outlet obstruction in rats. Human MSCs were labeled with nanoparticles containing superparamagnetic iron oxide (SPION), and transplanted in rat BOO lesion site. Forty 6-week-old female Sprague-Dawley rats were divided into four groups (group 1: control, group 2: sham operation, group 3: BOO, and group 4: BOO rats receiving SPION-hMSCs). Two weeks after the onset of BOO, 1 × 10(6) SPION-hMSCs were injected into the bladder wall. Serial T2-weighted MR images were taken immediately after transplantation of SPION-labeled human MSCs and at 4 weeks posttransplantation. T2-weighted MR images showed a clear hypointense signal induced by the SPION-labeled MSCs. While the expression of collagen and TGF-β protein increased after BOO, the expression of both returned to the original levels after MSC transplantation. Expression of HGF and c-met protein also increased in the group with MSC transplantation. Maximal voiding pressure and residual urine volume increased after BOO but they recovered after MSC transplantation. Human MSCs transplanted in rat BOO models inhibited the bladder fibrosis and mediated recovery of bladder dysfunction. Transplantation of MSC-based cell therapy could be a novel therapeutic strategy against bladder fibrosis in patients with bladder outlet obstruction.

Autologous transplantation of amniotic fluid-derived mesenchymal stem cells into sheep fetuses

Long-term engraftment and phenotype correction has been difficult to achieve in humans after in utero stem cell transplantation mainly because of allogeneic rejection. Autologous cells could be obtained during gestation from the amniotic fluid with minimal risk for the fetus and the mother. Using a sheep model, we explored the possibility of using amniotic fluid mesenchymal stem cells (AFMSCs) for autologous in utero stem cell/gene therapy. We collected amniotic fluid (AF) under ultrasound-guided amniocentesis in early gestation pregnant sheep (n = 9, 58 days of gestation, term = 145 days). AFMSCs were isolated and expanded in all sampled fetal sheep. Those cells were transduced using an HIV vector encoding enhanced green fluorescent protein (GFP) with 63.2% (range 38.3-96.2%) transduction efficiency rate. After expansion, transduced AFMSCs were injected into the peritoneal cavity of each donor fetal sheep at 76 days under ultrasound guidance. One ewe miscarried twin fetuses after amniocentesis. Intraperitoneal injection was successful in the remaining 7 fetal sheep giving a 78% survival for the full procedure. Tissues were sampled at postmortem examination 2 weeks later. PCR analysis detected GFP-positive cells in fetal tissues including liver, heart, placenta, membrane, umbilical cord, adrenal gland, and muscle. GFP protein was detected in these tissues by Western blotting and further confirmed by cytofluorimetric and immunofluorescence analyses. This is the first demonstration of autologous stem cell transplantation in the fetus using AFMSCs. Autologous cells derived from AF showed widespread organ migration and could offer an alternative way to ameliorate prenatal congenital disease.