Effect of Specific Surface Area and Hydrophobicity of Electrospun Nanofibers on the Sustained Release Performance of Diclofenac Sodium.

Nanofibers produced by electrospinning are suitable options for slow-release materials. Diclofenac sodium (DS) is a nonsteroidal anti-inflammatory medication with a brief half-life that can serve as an effective sustained-release agent. This paper presents a novel method for producing DS-sustained release nanofibers by electrostatic spinning processes. During the preparation, the slow-release capabilities of biodegradable materials poly(lactic acid) (PLA) and polycaprolactone (PCL) are investigated. A composite drug-carrying scaffold is prepared to enhance the sustained-release performance. The sustained release ability is affected by the specific surface area of the nanofibers and the hydrophobicity of the polymer. The findings indicate that the composite nanofiber with a PLA/PCL ratio of 1:1 demonstrates the most effective sustained-release performance. The release rate is mostly influenced by the hydrophobicity of the polymer at this point. Sustained-release kinetic simulations were performed and revealed that the release of nanofibers follows a first-order release paradigm. This work presents a straightforward approach for creating a sustained-release formulation of DS.

Optimizing cell therapy by sorting cells with high extracellular vesicle secretion.

Critical challenges remain in clinical translation of extracellular vesicle (EV)-based therapeutics due to the absence of methods to enrich cells with high EV secretion. Current cell sorting methods are limited to surface markers that are uncorrelated to EV secretion or therapeutic potential. Here, we utilize a nanovial technology for enrichment of millions of single cells based on EV secretion. This approach is applied to select mesenchymal stem cells (MSCs) with high EV secretion as therapeutic cells for improving treatment. The selected MSCs exhibit distinct transcriptional profiles associated with EV biogenesis and vascular regeneration and maintain high levels of EV secretion after sorting and regrowth. In a mouse model of myocardial infarction, treatment with high-secreting MSCs improves heart functions compared to treatment with low-secreting MSCs. These findings highlight the therapeutic importance of EV secretion in regenerative cell therapies and suggest that selecting cells based on EV secretion could enhance therapeutic efficacy.

Molecular distinctions of bronchoalveolar and alveolar organoids under differentiation conditions.

The bronchoalveolar organoid (BAO) model is increasingly acknowledged as an ex-vivo platform that accurately emulates the structural and functional attributes of proximal airway tissue. The transition from bronchoalveolar progenitor cells to alveolar organoids is a common event during the generation of BAOs. However, there is a pressing need for comprehensive analysis to elucidate the molecular distinctions characterizing the pre-differentiated and post-differentiated states within BAO models. This study established a murine BAO model and subsequently triggered its differentiation. Thereafter, a suite of multidimensional analytical procedures was employed, including the morphological recognition and examination of organoids utilizing an established artificial intelligence (AI) image tracking system, quantification of cellular composition, proteomic profiling and immunoblots of selected proteins. Our investigation yielded a detailed evaluation of the morphologic, cellular, and molecular variances demarcating the pre- and post-differentiation phases of the BAO model. We also identified of a potential molecular signature reflective of the observed morphological transformations. The integration of cutting-edge AI-driven image analysis with traditional cellular and molecular investigative methods has illuminated key features of this nascent model.

Inhalation of ACE2-expressing lung exosomes provides prophylactic protection against SARS-CoV-2.

Continued emergence of SARS-CoV-2 variants of concern that are capable of escaping vaccine-induced immunity highlights the urgency of developing new COVID-19 therapeutics. An essential mechanism for SARS-CoV-2 infection begins with the viral spike protein binding to the human ACE2. Consequently, inhibiting this interaction becomes a highly promising therapeutic strategy against COVID-19. Herein, we demonstrate that ACE2-expressing human lung spheroid cells (LSC)-derived exosomes (LSC-Exo) could function as a prophylactic agent to bind and neutralize SARS-CoV-2, protecting the host against SARS-CoV-2 infection. Inhalation of LSC-Exo facilitates its deposition and biodistribution throughout the whole lung in a female mouse model. We show that LSC-Exo blocks the interaction of SARS-CoV-2 with host cells in vitro and in vivo by neutralizing the virus. LSC-Exo treatment protects hamsters from SARS-CoV-2-induced disease and reduced viral loads. Furthermore, LSC-Exo intercepts the entry of multiple SARS-CoV-2 variant pseudoviruses in female mice and shows comparable or equal potency against the wild-type strain, demonstrating that LSC-Exo may act as a broad-spectrum protectant against existing and emerging virus variants.

Optimizing Cell Therapy by Sorting Cells with High Extracellular Vesicle Secretion.

Critical challenges remain in clinical translation of extracellular vesicle (EV)-based therapeutics due to the absence of methods to enrich cells with high EV secretion. Current cell sorting methods are limited to surface markers that are uncorrelated to EV secretion or therapeutic potential. We developed a nanovial technology for enrichment of millions of single cells based on EV secretion. This approach was applied to select mesenchymal stem cells (MSCs) with high EV secretion as therapeutic cells for improving treatment. The selected MSCs exhibited distinct transcriptional profiles associated with EV biogenesis and vascular regeneration and maintained high levels of EV secretion after sorting and regrowth. In a mouse model of myocardial infarction, treatment with high-secreting MSCs improved heart functions compared to treatment with low-secreting MSCs. These findings highlight the therapeutic importance of EV secretion in regenerative cell therapies and suggest that selecting cells based on EV secretion could enhance therapeutic efficacy.

Free nitrous acid prediction in ANAMMOX process using hybrid deep neural network model.

Free nitrous acid (FNA) is a critical metric for stabilization of ANAMMOX but can not be directly and immediately measured by sensors or chemical measurement method, which hinders the effective management and operation for ANAMMOX. This study focuses on FNA prediction using hybrid model based on temporal convolutional network (TCN) combined with attention mechanism (AM) optimized by multiobjective tree-structured parzen estimator (MOTPE), called MOTPE-TCNA. A case study in an ANAMMOX reactor is carried out. Results show that nitrogen removal rate (NRR) is highly correlated with FNA concentration, indicating that it can forecast the operational status by predicting FNA. Then, MOTPE successfully optimizes the hyperparameters of TCN, helping TCN achieve a high prediction accuracy, and AM furtherly improves model accuracy. MOTPE-TCNA obtains the highest prediction accuracy, whose R2 value gets 0.992, increasing 1.71-11.80% compared to other models. As a deep neural network model, MOTPE-TCNA has more advantages than traditional machine learning methods in FNA prediction, which is beneficial to maintain the stable operation and easy control for ANAMMOX process.

Multistimuli-responsive fluorescence behaviours of aggregation-induced emission small-molecule and electrospun nanofibre films for acid-base vapour sensing.

Multistimuli-responsive fluorescent materials have garnered great research interest benefited from their practical applications. Two twisted-structure compounds containing tetraphenylethylene (TPE) as the aggregation-induced emission (AIE) group and a pyridine unit as the acid reaction site to obtain new multistimuli-responsive fluorescent compounds (namely, TPECNPy: TPECNPy-2 and TPECNPy-3) were successfully synthesized through a one-step Knoevenagel condensation reaction. The multiple-stimuli response process of TPECNPy was investigated by means of photoluminescence (PL) spectra and emission colour. The results showed that both TPECNPy compounds with excellent AIE abilities displayed reversible emission wavelength and colour changes in response to multiple external stimuli, including grinding-fuming by CH2 Cl2 or annealing and HCl-NH3 vapour fuming. More importantly, fluorescent nanofibre films were prepared by electrospinning a solution of TPECNPy mixed with cellulose acetate (CA), and these exhibited reversible acid-induced discolouration, even with only 1 wt% TPECNPy. The results of this study may inspire strategies for designing multistimuli-responsive materials and preparing fluorescent sensing nanofibre films.

Comparison of extruded cell nanovesicles and exosomes in their molecular cargos and regenerative potentials.

Extracellular vesicles (EVs) generated from mesenchymal stem cells (MSCs) play an essential role in modulating cell-cell communication and tissue regeneration. The clinical translation of EVs is constrained by the poor yield of EVs. Extrusion has recently become an effective technique for producing a large scale of nanovesicles (NVs). In this study, we systematically compared MSC NVs (from extrusion) and EVs (from natural secretion). Proteomics and RNA sequencing data revealed that NVs resemble MSCs more closely than EVs. Additionally, microRNAs in NVs are related to cardiac repair, fibrosis repression, and angiogenesis. Lastly, intravenous delivery of MSC NVs improved heart repair and cardiac function in a mouse model of myocardial infarction. Electronic Supplementary Material: Supplementary material (Figs. S1-S4) is available in the online version of this article at 10.1007/s12274-023-5374-3.

Intrapericardial long non-coding RNA-Tcf21 antisense RNA inducing demethylation administration promotes cardiac repair.

AIMS: Epicardium and epicardium-derived cells are critical players in myocardial fibrosis. Mesenchymal stem cell-derived extracellular vesicles (EVs) have been studied for cardiac repair to improve cardiac remodelling, but the actual mechanisms remain elusive. The aim of this study is to investigate the mechanisms of EV therapy for improving cardiac remodelling and develop a promising treatment addressing myocardial fibrosis. METHODS AND RESULTS: Extracellular vesicles were intrapericardially injected for mice myocardial infarction treatment. RNA-seq, in vitro gain- and loss-of-function experiments, and in vivo studies were performed to identify targets that can be used for myocardial fibrosis treatment. Afterward, a lipid nanoparticle-based long non-coding RNA (lncRNA) therapy was prepared for mouse and porcine models of myocardial infarction treatment. Intrapericardial injection of EVs improved adverse myocardial remodelling in mouse models of myocardial infarction. Mechanistically, Tcf21 was identified as a potential target to improve cardiac remodelling. Loss of Tcf21 function in epicardium-derived cells caused increased myofibroblast differentiation, whereas forced Tcf21 overexpression suppressed transforming growth factor-ß signalling and myofibroblast differentiation. LncRNA-Tcf21 antisense RNA inducing demethylation (TARID) that enriched in EVs was identified to up-regulate Tcf21 expression. Formulated lncRNA-TARID-laden lipid nanoparticles up-regulated Tcf21 expression in epicardium-derived cells and improved cardiac function and histology in mouse and porcine models of myocardial infarction. CONCLUSION: This study identified Tcf21 as a critical target for improving cardiac fibrosis. Up-regulating Tcf21 by using lncRNA-TARID-laden lipid nanoparticles could be a promising way to treat myocardial fibrosis. This study established novel mechanisms underlying EV therapy for improving adverse remodelling and proposed a lncRNA therapy for cardiac fibrosis.

An inhaled bioadhesive hydrogel to shield non-human primates from SARS-CoV-2 infection.

The surge of fast-spreading SARS-CoV-2 mutated variants highlights the need for fast, broad-spectrum strategies to counteract viral infections. In this work, we report a physical barrier against SARS-CoV-2 infection based on an inhalable bioadhesive hydrogel, named spherical hydrogel inhalation for enhanced lung defence (SHIELD). Conveniently delivered via a dry powder inhaler, SHIELD particles form a dense hydrogel network that coats the airway, enhancing the diffusional barrier properties and restricting virus penetration. SHIELD's protective effect is first demonstrated in mice against two SARS-CoV-2 pseudo-viruses with different mutated spike proteins. Strikingly, in African green monkeys, a single SHIELD inhalation provides protection for up to 8 hours, efficiently reducing infection by the SARS-CoV-2 WA1 and B.1.617.2 (Delta) variants. Notably, SHIELD is made with food-grade materials and does not affect normal respiratory functions. This approach could offer additional protection to the population against SARS-CoV-2 and other respiratory pathogens.

Intrapericardial Exosome Therapy Dampens Cardiac Injury via Activating Foxo3.

BACKGROUND: Mesenchymal stem cell (MSC)-derived exosomes are well recognized immunomodulating agents for cardiac repair, while the detailed mechanisms remain elusive. The Pericardial drainage pathway provides the heart with immunosurveillance and establishes a simplified model for studying the mechanisms underlying the immunomodulating effects of therapeutic exosomes. METHODS: Myocardial infarction (MI) models with and without pericardiectomy (corresponding to Tomy MI and NonTomy MI) were established to study the functions of pericardial drainage pathway in immune activation of cardiac-draining mediastinal lymph node (MLN). Using the NonTomy MI model, MSC exosomes or vehicle PBS was intrapericardially injected for MI treatment. Via cell sorting and RNA-seq (RNA-sequencing) analysis, the differentially expressed genes were acquired for integrated pathway analysis to identify responsible mechanisms. Further, through functional knockdown/inhibition studies, application of cytokines and neutralizing antibodies, western blot, flow cytometry, and cytokine array, the molecular mechanisms were studied. In addition, the therapeutic efficacy of intrapericardially injected exosomes for MI treatment was evaluated through functional and histological analyses. RESULTS: We show that the pericardial draining pathway promoted immune activation in the MLN following MI. Intrapericardially injected exosomes accumulated in the MLN and induced regulatory T cell differentiation to promote cardiac repair. Mechanistically, uptake of exosomes by major histocompatibility complex (MHC)-II+ antigen-presenting cells (APCs) induced Foxo3 activation via the protein phosphatase (PP)-2A/p-Akt/forkhead box O3 (Foxo3) pathway. Foxo3 dominated APC cytokines (IL-10, IL-33, and IL-34) expression and built up a regulatory T cell (Treg)-inducing niche in the MLN. The differentiation of Tregs as well as their cardiac deployment were elevated, which contributed to cardiac inflammation resolution and cardiac repair. CONCLUSIONS: This study reveals a novel mechanism underlying the immunomodulation effects of MSC exosomes and provides a promising candidate (PP2A/p-Akt/Foxo3 signaling pathway) with a favorable delivery route (intrapericardial injection) for cardiac repair.

Inhalable dry powder mRNA vaccines based on extracellular vesicles.

Respiratory diseases are a global burden, with millions of deaths attributed to pulmonary illnesses and dysfunctions. Therapeutics have been developed, but they present major limitations regarding pulmonary bioavailability and product stability. To circumvent such limitations, we developed room-temperature-stable inhalable lung-derived extracellular vesicles or exosomes (Lung-Exos) as mRNA and protein drug carriers. Compared with standard synthetic nanoparticle liposomes (Lipos), Lung-Exos exhibited superior distribution to the bronchioles and parenchyma and are deliverable to the lungs of rodents and nonhuman primates (NHPs) by dry powder inhalation. In a vaccine application, severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein encoding mRNA-loaded Lung-Exos (S-Exos) elicited greater immunoglobulin G (IgG) and secretory IgA (SIgA) responses than its loaded liposome (S-Lipo) counterpart. Importantly, S-Exos remained functional at room-temperature storage for one month. Our results suggest that extracellular vesicles can serve as an inhaled mRNA drug-delivery system that is superior to synthetic liposomes.

Nanoparticles functionalized with stem cell secretome and CXCR4-overexpressing endothelial membrane for targeted osteoporosis therapy.

BACKGROUND: Osteoporosis is a chronic condition affecting patients' morbidity and mortality and represents a big socioeconomic burden. Because stem cells can proliferate and differentiate into bone-forming cells, stem cell therapy for osteoporosis has been widely studied. However, cells as a live drug face multiple challenges because of their instability during preservation and transportation. In addition, cell therapy has potential adverse effects such as embolism, tumorigenicity, and immunogenicity. RESULTS: Herein, we sought to use cell-mimicking and targeted therapeutic nanoparticles to replace stem cells. We fabricated nanoparticles (NPs) using polylactic-co-glycolic acid (PLGA) loaded with the secretome (Sec) from mesenchymal stem cells (MSCs) to form MSC-Sec NPs. Furthermore, we cloaked the nanoparticles with the membranes from C-X-C chemokine receptor type 4 (CXCR4)-expressing human microvascular endothelial cells (HMECs) to generate MSC-Sec/CXCR4 NP. CXCR4 can target the nanoparticles to the bone microenvironment under osteoporosis based on the CXCR4/SDF-1 axis. CONCLUSIONS: In a rat model of osteoporosis, MSC-Sec/CXCR4 NP were found to accumulate in bone, and such treatment inhibited osteoclast differentiation while promoting osteogenic proliferation. In addition, our results showed that MSC-Sec/CXCR4 NPs reduce OVX-induced bone mass attenuation in OVX rats.

A fluid-powered refillable origami heart pouch for minimally invasive delivery of cell therapies in rats and pigs.

BACKGROUND: Cardiac repair after heart injury remains a big challenge and current drug delivery to the heart is suboptimal. Repeated dosing of therapeutics is difficult due to the invasive nature of such procedures. METHODS: We developed a fluid-driven heart pouch with a memory-shaped microfabricated lattice structure inspired by origami. The origami structure allowed minimally invasive delivery of the pouch to the heart with two small incisions and can be refilled multiple times with the therapeutic of choice. FINDINGS: We tested the pouch's ability to deliver mesenchymal stem cells (MSCs) in a rodent model of acute myocardial infarction and demonstrated the feasibility of minimally invasive delivery in a swine model. The pouch's semi-permeable membrane successfully protected delivered cells from their surroundings, maintaining their viability while releasing paracrine factors to the infarcted site for cardiac repair. CONCLUSIONS: In summary, we developed a fluid-driven heart pouch with a memory-shaped microfabricated lattice structure inspired by origami. The origami structure allowed minimally invasive delivery of the pouch to the heart with two small incisions and can be refilled with the therapeutic of choice.

Extruded Mesenchymal Stem Cell Nanovesicles Are Equally Potent to Natural Extracellular Vesicles in Cardiac Repair.

Mesenchymal stem cells (MSCs) repair injured tissues mainly through their paracrine actions. One of the important paracrine components of MSC secretomes is the extracellular vesicle (EV). The therapeutic potential of MSC-EVs has been established in various cardiac injury preclinical models. However, the large-scale production of EVs remains a challenge. We sought to develop a scale-up friendly method to generate a large number of therapeutic nanovesicles from MSCs by extrusion. Those extruded nanovesicles (NVs) are miniature versions of MSCs in terms of surface marker expression. The yield of NVs is 20-fold more than that of EVs. In vitro, cell-based assays demonstrated the myocardial protective effects and therapeutic potential of NVs. Intramyocardial delivery of NVs in the injured heart after ischemia-reperfusion led to a reduction in scar sizes and preservation of cardiac functions. Such therapeutic benefits are similar to those injected with natural EVs from the same MSC parental cells. In addition, NV therapy promoted angiogenesis and proliferation of cardiomyocytes in the post-injury heart. In summary, extrusion is a highly efficient method to generate a large quantity of therapeutic NVs that can potentially replace extracellular vesicles in regenerative medicine applications.

Zoledronate alters natural progression of tissue-engineered vascular grafts.

Macrophages are a critical driver of neovessel formation in tissue-engineered vascular grafts (TEVGs), but also contribute to graft stenosis, a leading clinical trial complication. Macrophage depletion via liposomal delivery of clodronate, a first-generation bisphosphonate, mitigates stenosis, but simultaneously leads to a complete lack of tissue development in TEVGs. This result and the associated difficulty of utilizing liposomal delivery means that clodronate may not be an ideal means of preventing graft stenosis. Newer generation bisphosphonates, such as zoledronate, may have differential effects on graft development with more facile drug delivery. We sought to examine the effect of zoledronate on TEVG neotissue formation and its potential application for mitigating TEVG stenosis. Thus, mice implanted with TEVGs received zoledronate or no treatment and were monitored by serial ultrasound for graft dilation and stenosis. After two weeks, TEVGs were explanted for histological examination. The overall graft area and remaining graft material (polyglycolic-acid) were higher in the zoledronate treatment group. These effects were associated with a corresponding decrease in macrophage infiltration. In addition, zoledronate affected the deposition of collagen in TEVGs, specifically, total and mature collagen. These differences may be, in part, explained by a depletion of leukocytes within the bone marrow that subsequently led to a decrease in the number of tissue-infiltrating macrophages. TEVGs from zoledronate-treated mice demonstrated a significantly greater degree of smooth muscle cell presence. There was no statistical difference in graft patency between treatment and control groups. While zoledronate led to a decrease in the number of macrophages in the TEVGs, the severity of stenosis appears to have increased significantly. Zoledronate treatment demonstrates that the process of smooth muscle cell-mediated neointimal hyperplasia may occur separately from a macrophage-mediated mechanism.

A stem cell-derived ovarian regenerative patch restores ovarian function and rescues fertility in rats with primary ovarian insufficiency.

Rationale: Primary ovarian insufficiency (POI) normally occurs before age 40 and is associated with infertility. Hormone replacement therapy is often prescribed to treat vasomotor symptom, but it cannot restore ovarian function or fertility. Stem cell therapy has been studied for the treatment of POI. However, the application of live stem cells has suffered from drawbacks, such as low cell retention/engraftment rate, risks for tumorigenicity and immunogenicity, and lack of off-the-shelf feasibility. Methods: We developed a therapeutic ovarian regenerative patch (ORP) that composed of clinically relevant hydrolysable scaffolds and synthetic mesenchymal stem cells (synMSCs), which are microparticles encapsulating the secretome from MSCs. The therapeutic potency of ORP was tested in rats with cisplatin induced POI injury. Results:In vitro studies revealed that ORP stimulated proliferation of ovarian somatic cells (OSCs) and inhibited apoptosis under injury stress. In a rat model of POI, implantation of ORP rescued fertility by restoring sexual hormone secretion, estrus cycle duration, and follicle development. Conclusion: ORP represents a cell-free, off-the-shelf, and clinically feasible treatment for POI.

Platelet membrane and stem cell exosome hybrid enhances cellular uptake and targeting to heart injury.

Exosomes from mesenchymal stem cells have been largely studied as therapeutics to treat myocardial infarctions. However, exosomes injected for therapeutic purposes face a number of challenges, including competition from exosomes already in circulation, and the internalization/clearance by the mononuclear phagocyte system. In this study, we hybrid exosomes with platelet membranes to enhance their ability to target the injured heart and avoid being captured by macrophages. Furthermore, we found that encapsulation by the platelet membranes induces macropinocytosis, enhancing the cellular uptake of exosomes by endothelial cells and cardiomyocytes strikingly. In vivo studies showed that the cardiac targeting ability of hybrid exosomes in a mice model with myocardial infarction injury. Last, we tested cardiac functions and performed immunohistochemistry to confirm a better therapeutic effect of platelet membrane modified exosomes compared to non-modified exosomes. Our studies provide proof-of-concept data and a universal approach to enhance the binding and accumulation of exosomes in injured tissues.

A Minimally Invasive Exosome Spray Repairs Heart after Myocardial Infarction.

Myocardial infarction (MI) remains the most common cause of death worldwide. Many MI survivors will suffer from recurrent heart failure (HF), which has been recognized as a determinant of adverse prognosis. Despite the success of improved early survival after MI by primary percutaneous coronary intervention, HF after MI is becoming the major driver of late morbidity, mortality, and healthcare costs. The development of regenerative medicine has brought hope to MI treatment in the past decade. Mesenchymal stem cell (MSC)-derived exosomes have been established as an essential part of stem cell paracrine factors for heart regeneration. However, its regenerative power is hampered by low delivery efficiency to the heart. We designed, fabricated, and tested a minimally invasive exosome spray (EXOS) based on MSC exosomes and biomaterials. In a mouse model of acute myocardial infarction, EXOS improved cardiac function and reduced fibrosis, and promoted endogenous angiomyogenesis in the post-injury heart. We further tested the feasibility and safety of EXOS in a pig model. Our results indicate that EXOS is a promising strategy to deliver therapeutic exosomes for heart repair.

All Roads Lead to Rome (the Heart): Cell Retention and Outcomes From Various Delivery Routes of Cell Therapy Products to the Heart.

In the past decades, numerous preclinical studies and several clinical trials have evidenced the feasibility of cell transplantation in treating heart diseases. Over the years, different delivery routes of cell therapy have emerged and broadened the width of the field. However, a common hurdle is shared by all current delivery routes: low cell retention. A myriad of studies confirm that cell retention plays a crucial role in the success of cell-mediated cardiac repair. It is important for any delivery route to maintain donor cells in the recipient heart for enough time to not only proliferate by themselves, but also to send paracrine signals to surrounding damaged heart cells and repair them. In this review, we first undertake an in-depth study of primary theories of cell loss, including low efficiency in cell injection, "washout" effects, and cell death, and then organize the literature from the past decade that focuses on cell transplantation to the heart using various cell delivery routes, including intracoronary injection, systemic intravenous injection, retrograde coronary venous injection, and intramyocardial injection. In addition to a recapitulation of these approaches, we also clearly evaluate their strengths and weaknesses. Furthermore, we conduct comparative research on the cell retention rate and functional outcomes of these delivery routes. Finally, we extend our discussion to state-of-the-art bioengineering techniques that enhance cell retention, as well as alternative delivery routes, such as intrapericardial delivery. A combination of these novel strategies and more accurate assessment methods will help to address the hurdle of low cell retention and boost the efficacy of cell transplantation to the heart.