Cardiac Progenitor Cells: The Matrix Has You

Decellularized diseased tissues: current state-of-the-art and future directions

Decellularized matrices derived from diseased tissues/organs have evolved in the most recent years, providing novel research perspectives for understanding disease occurrence and progression and providing accurate pseudo models for developing new disease treatments. Although decellularized matrix maintaining the native composition, ultrastructure, and biomechanical characteristics of extracellular matrix (ECM), alongside intact and perfusable vascular compartments, facilitates the construction of bioengineered organ explants in vitro and promotes angiogenesis and tissue/organ regeneration in vivo, the availability of healthy tissues and organs for the preparation of decellularized ECM materials is limited. In this paper, we review the research advancements in decellularized diseased matrices. Considering that current research focuses on the matrices derived from cancers and fibrotic organs (mainly fibrotic kidney, lungs, and liver), the pathological characterizations and the applications of these diseased matrices are mainly discussed. Additionally, a contrastive analysis between the decellularized diseased matrices and decellularized healthy matrices, along with the development in vitro 3D models, is discussed in this paper. And last, we have provided the challenges and future directions in this review. Deep and comprehensive research on decellularized diseased tissues and organs will promote in-depth exploration of source materials in tissue engineering field, thus providing new ideas for clinical transformation.

Human Cardiac Progenitor Cell-Derived Extracellular Vesicles Exhibit Promising Potential for Supporting Cardiac Repair in Vitro

Although human Cardiac Progenitor Cells (hCPCs) are not retained by host myocardium they still improve cardiac function when injected into ischemic heart. Emerging evidence supports the hypothesis that hCPC beneficial effects are induced by paracrine action on resident cells. Extracellular vesicles (EVs) are an intriguing mechanism of cell communication based on the transport and transfer of peptides, lipids, and nucleic acids that have the potential to modulate signaling pathways, cell growth, migration, and proliferation of recipient cells. We hypothesize that EVs are involved in the paracrine effects elicited by hCPCs and held accountable for the response of the infarcted myocardium to hCPC-based cell therapy. To test this theory, we collected EVs released by hCPCs isolated from healthy myocardium and evaluated the effects they elicited when administered to resident hCPC and cardiac fibroblasts (CFs) isolated from patients with post-ischemic end-stage heart failure. Evidence emerging from our study indicated that hCPC-derived EVs impacted upon proliferation and survival of hCPCs residing in the ischemic heart and regulated the synthesis and deposition of extracellular-matrix by CFs. These findings suggest that beneficial effects exerted by hCPC injection are, at least to some extent, ascribable to the delivery of signals conveyed by EVs.

The Microenvironment of Decellularized Extracellular Matrix from Heart Failure Myocardium Alters the Balance between Angiogenic and Fibrotic Signals from Stromal Primitive Cells

Cardiac adverse remodeling is characterized by biological changes that affect the composition and architecture of the extracellular matrix (ECM). The consequently disrupted signaling can interfere with the balance between cardiogenic and pro-fibrotic phenotype of resident cardiac stromal primitive cells (CPCs). The latter are important players in cardiac homeostasis and can be exploited as therapeutic cells in regenerative medicine. Our aim was to compare the effects of human decellularized native ECM from normal (dECM-NH) or failing hearts (dECM-PH) on human CPCs. CPCs were cultured on dECM sections and characterized for gene expression, immunofluorescence, and paracrine profiles. When cultured on dECM-NH, CPCs significantly upregulated cardiac commitment markers (CX43, NKX2.5), cardioprotective cytokines (bFGF, HGF), and the angiogenesis mediator, NO. When seeded on dECM-PH, instead, CPCs upregulated pro-remodeling cytokines (IGF-2, PDGF-AA, TGF-β) and the oxidative stress molecule H₂O₂. Interestingly, culture on dECM-PH was associated with impaired paracrine support to angiogenesis, and increased expression of the vascular endothelial growth factor (VEGF)-sequestering decoy isoform of the KDR/VEGFR2 receptor. Our results suggest that resident CPCs exposed to the pathological microenvironment of remodeling ECM partially lose their paracrine angiogenic properties and release more pro-fibrotic cytokines. These observations shed novel insights on the crosstalk between ECM and stromal CPCs, suggesting also a cautious use of non-healthy decellularized myocardium for cardiac tissue engineering approaches.

Building an Artificial Cardiac Microenvironment: A Focus on the Extracellular Matrix

The increased knowledge in cell signals and stem cell differentiation, together with the development of new technologies, such as 3D bioprinting, has made the generation of artificial tissues more feasible for in vitro studies and in vivo applications. In the human body, cell fate, function, and survival are determined by the microenvironment, a rich and complex network composed of extracellular matrix (ECM), different cell types, and soluble factors. They all interconnect and communicate, receiving and sending signals, modulating and responding to cues. In the cardiovascular field, the culture of stem cells in vitro and their differentiation into cardiac phenotypes is well established, although differentiated cardiomyocytes often lack the functional maturation and structural organization typical of the adult myocardium. The recreation of an artificial microenvironment as similar as possible to the native tissue, though, has been shown to partly overcome these limitations, and can be obtained through the proper combination of ECM molecules, different cell types, bioavailability of growth factors (GFs), as well as appropriate mechanical and geometrical stimuli. This review will focus on the role of the ECM in the regulation of cardiac differentiation, will provide new insights on the role of supporting cells in the generation of 3D artificial tissues, and will also present a selection of the latest approaches to recreate a cardiac microenvironment in vitro through 3D bioprinting approaches.

On the Road to Regeneration: "Tools" and "Routes" Towards Efficient Cardiac Cell Therapy for Ischemic Cardiomyopathy

PURPOSE OF REVIEW

Cardiac regenerative medicine is a field bridging together biotechnology and surgical science. In this review, we present the explored surgical roads to cell delivery and the known effects of each delivery method on cell therapy efficiency. We also list the more recent clinical trials, exploring the safety and efficacy of delivery routes used for cardiac cell therapy approaches.

RECENT FINDINGS

There is no consensus in defining which way is the most suitable for the delivery of the different therapeutic cell types to the damaged heart tissue. In addition, it emerged that the "delivery issue" has not been systematically addressed in each clinical trial and for each and every cell type capable of cardiac repair. Cardiac damage occurring after an ischemic insult triggers a cascade of cellular events, eventually leading to heart failure through fibrosis and maladaptive remodelling. None of the pharmacological or medical interventions approved so far can rescue or reverse this phenomenon, and cardiovascular diseases are still the leading cause of death in the western world. Therefore, for nearly 20 years, regenerative medicine approaches have focused on cell therapy as a promising road to pursue, with numerous preclinical and clinical testing of cell-based therapies being studied and developed. Nonetheless, consistent clinical results are still missing to reach consensus on the most effective strategy for ischemic cardiomyopathy, based on patient selection, diagnosis and stage of the disease, therapeutic cell type, and delivery route.

Anti-fibrotic Effects of Cardiac Progenitor Cells in a 3D-Model of Human Cardiac Fibrosis

Cardiac fibroblasts play a key role in chronic heart failure. The conversion from cardiac fibroblast to myofibroblast as a result of cardiac injury, will lead to excessive matrix deposition and a perpetuation of pro-fibrotic signaling. Cardiac cell therapy for chronic heart failure may be able to target fibroblast behavior in a paracrine fashion. However, no reliable human fibrotic tissue model exists to evaluate this potential effect of cardiac cell therapy. Using a gelatin methacryloyl hydrogel and human fetal cardiac fibroblasts (hfCF), we created a 3D in vitro model of human cardiac fibrosis. This model was used to study the possibility to modulate cellular fibrotic responses. Our approach demonstrated paracrine inhibitory effects of cardiac progenitor cells (CPC) on both cardiac fibroblast activation and collagen synthesis in vitro and revealed that continuous cross-talk between hfCF and CPC seems to be indispensable for the observed anti-fibrotic effect.

The Biological Mechanisms of Action of Cardiac Progenitor Cell Therapy

PURPOSE OF REVIEW

Cell therapy for cardiovascular diseases is regarded as a rapidly growing field within regenerative medicine. Different cellular populations enriched for cardiac progenitor cells (CPCs), or derivate a-cellular products, are currently under preclinical and clinical evaluation. Here, we have reviewed the described mechanisms whereby resident post-natal CPCs, isolated in different ways, act as a therapeutic product on the damaged myocardium.

RECENT FINDINGS

Several biological mechanisms of action have been described which can explain the multiple therapeutic effects of CPC treatment observed on cardiac function and remodelling. These mechanisms span from direct cardiovascular differentiation, through induction of resident progenitor proliferation, to paracrine effects on cardiac and non-cardiac cells mediated by exosomes and non-coding RNAs. All the reported mechanisms of action support an integrated view including cardiomyogenesis, cardioprotection, and anti-fibrotic effects. Moreover, future developments of CPC therapy approaches may support cell-free strategies, exploiting effective pleiotropic cell-derived products, such as exosomes.