Transforming Perspectives in Cardiac Cell Therapy: Hypothesis and Commentary Following Updated Results of a Pilot Study Investigating Very Long-Term Clinical Outcomes in Severe AMI Patients Following Trans-Epicardial Injection of Peripheral Blood CD34+ Cells

Ischemic heart attack is the leading cause of death worldwide. Ten percent of cases will die within an hour. Of the survivors, around 30% will have suffered a severe infarction which will lead to the irreparable destruction of 1 to 2 billion myocardial cells, causing an irreversible secondary heart failure with a poor prognosis in the short. The heart is a totally differentiated organ with a very low capacity for self-regeneration. No current treatment can prevent this fatal outcome, but only slow it down. For these reasons, cell therapy has generated enormous hope, but achieved somewhat disappointing results, depending on the type/source of cells which were used. From the end of 2002, our group conducted a Pilot study using immuno-selected autologous peripheral-blood (PB) CD34+ cells in a small cohort of patients who had experienced a heart attack with poor prognosis. Three of these patients were immediately considered for heart transplant but lacked a readily available donor. CD34+ cells were trans-epicardially delivered at the end of a coronary artery by-pass graft (CABG) operation without reperfusing the ischemic area, which was performed on a compassionate basis. All but one patient showed a marked and sustained improvement in their cardiac function parameters from the baseline values, associated with both cardiac tissue repair and revascularization, as demonstrated by PetScan examination. The patients' outcomes have been recently updated. Six out of seven patients have survived in good enough conditions for at least 12 years after cell therapy, including those three initially recommended for heart transplant and who have avoided it. Presently, five out of seven patients are still alive with an average follow-up of 17 years (range 16-20 years), which is very unusual after CABG for patients with such a poor initially prognosis.

Dissemination of Multipotent Stromal Cells in the Organism after Their Injection into Intact and Resected Liver in the Experiment

The possibility of dissemination of bone marrow multipotent stromal cells stained with Vybrant CM-Dil after injection into an intact and resected liver was studied using luminescence microscopy. Labeled cells were found in the kidneys, spleen, lungs, axillary, mesenteric, and inguinal lymph nodes. We observed dissemination of multipotent stromal cells and their detritus throughout the body that occurred only after filtration in the lungs, where most cells underwent destruction. Perivascularly located macrophages in various organs can phagocytize multipotent stromal cells and their detritus from blood vessels. The content of objects labeled with Vybrant CM-Dil in distant organs was significantly lower after multipotent stromal cell injection into the resected liver, which was associated with the deposition of cells in the damaged area of the organ and their partial entry into the abdominal cavity.

Hyaluronan and elastin-like protein (HELP) gels significantly improve microsphere retention in the myocardium

Heart disease is the leading cause of death globally, and delivery of therapeutic cargo (e.g., particles loaded with proteins, drugs, or genes and cells) through direct injection into the myocardium is a promising clinical intervention. However, retention of deliverables to the contracting myocardium is low, with as much as 60-90% of payload being lost within 24 hr. Commercially-available injectable hydrogels, including Matrigel, have been hypothesized to increase payload retention but have not yielded significant improvements in quantified analyses. Here, we assess a recombinant hydrogel composed of chemically modified hyaluronan and elastin-like protein (HELP) as an alternative injectable carrier to increase cargo retention. HELP is crosslinked using dynamic covalent bonds, and tuning the hyaluronan chemistry significantly alters hydrogel mechanical properties including stiffness, stress relaxation rate, and ease of injectability through a needle or catheter. These materials can be injected even after complete crosslinking, extending the time window for surgical delivery. We show that HELP gels significantly improve in vivo retention of microsphere cargo compared to Matrigel, both 1 day and 7 days post-injection directly into the rat myocardium. These data suggest that HELP gels may assist with the clinical translation of therapeutic cargo designed for delivery into the contracting myocardium by preventing acute cargo loss.

Prototype device for endoventricular beta-emitting radiotracer detection and molecularly-guided intervention

BACKGROUND

We have set out to develop a catheter-based theranostic system that: (a) identifies diseased and at-risk myocardium via endocardial detection of systemically delivered β-emitting radiotracers and (b) utilizes molecular signals to guide delivery of therapeutics to appropriate tissue via direct intramyocardial injection.

METHODS

Our prototype device consists of a miniature β-radiation detector contained within the tip of a flexible intravascular catheter. The catheter can be adapted to incorporate an injection port and retractable needle for therapeutic delivery. The performance of the β-detection catheter was assessed in vitro with various β-emitting radionuclides and ex vivo in hearts of pigs following systemic injection of 18F-fluorodeoxyglucose (18F-FDG) at 1-week post-myocardial infarction. Regional catheter-based endocardial measurements of 18F activity were compared to regional tissue activity from PET/CT images and gamma counting.

RESULTS

The β-detection catheter demonstrated sensitive in vitro detection of β-radiation from 22Na (β+), 18F (β+), and 204Tl (β-), with minimal sensitivity to γ-radiation. For 18F, the catheter demonstrated a sensitivity of 4067 counts/s/μCi in contact and a spatial resolution of 1.1 mm FWHM. Ex vivo measurements of endocardial 18F activity with the β-detection catheter in the chronic pig infarct model demonstrated good qualitative and quantitative correlation with regional tissue activity from PET/CT images and gamma counting.

CONCLUSION

The prototype β-detection catheter demonstrates sensitive and selective detection of β- and β+ emissions over a wide range of energies and enables high-fidelity ex vivo characterization of endocardial activity from systemically delivered 18F-FDG.

Dare to dream? Cell-based therapies for heart failure after DREAM-HF: Review and roadmap for future clinical study

Clinical trials of cell-based therapies for heart failure have resulted in significant strides forward in our understanding of the potential the failing heart has for regeneration and repair. Yet, two decades on, the need for novel cell-based therapies for heart failure has never been greater. The DREAM-HF trial, which was presented as a late-breaking trial at the American Heart Association Scientific Sessions 2021 did not meet the primary heart failure outcome, but did show a large, clinically significant reduction in major adverse cardiovascular events (MACE) in patients receiving cells, an effect that was most pronounced in patients with evidence of maladaptive inflammation. These results represent an important step forward in our understanding of how cell-based therapies can exert beneficial effects in patients with heart failure and should serve as a guide for future clinical efforts. In light of the results of DREAM-HF, this review serves to provide an understanding of the current state of cell-based therapies for heart failure, as well as to highlight major knowledge gaps and suggest guiding principles for clinical trials of cell therapy going forward. Using the knowledge gained from DREAM-HF along with the trials that preceded it, the potential for breakthrough cell-based therapies for heart failure in the coming decade is immense.

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.

Hypoimmune induced pluripotent stem cell-derived cell therapeutics treat cardiovascular and pulmonary diseases in immunocompetent allogeneic mice

The emerging field of regenerative cell therapy is still limited by the few cell types that can reliably be differentiated from pluripotent stem cells and by the immune hurdle of commercially scalable allogeneic cell therapeutics. Here, we show that gene-edited, immune-evasive cell grafts can survive and successfully treat diseases in immunocompetent, fully allogeneic recipients. Transplanted endothelial cells improved perfusion and increased the likelihood of limb preservation in mice with critical limb ischemia. Endothelial cell grafts transduced to express a transgene for alpha1-antitrypsin (A1AT) successfully restored physiologic A1AT serum levels in mice with genetic A1AT deficiency. This cell therapy prevented both structural and functional changes of emphysematous lung disease. A mixture of endothelial cells and cardiomyocytes was injected into infarcted mouse hearts, and both cell types orthotopically engrafted in the ischemic areas. Cell therapy led to an improvement in invasive hemodynamic heart failure parameters. Our study supports the development of hypoimmune, universal regenerative cell therapeutics for cost-effective treatments of major diseases.

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.

Multipotent Stromal Cell Extracellular Vesicle Distribution in Distant Organs after Introduction into a Bone Tissue Defect of a Limb

When administered intravenously, extracellular vesicles derived from multipotent stromal cells (MSC EVs) immediately pass through the lungs along with the blood and regularly spread to all organs. When administered intraperitoneally, they are absorbed either into the blood or into the lymph and are quickly disseminated throughout the body. The possibility of generalized spread of MSC EVs to distant organs in case of local intratissular administration remains unexplored. However, it is impossible to exclude MSC EV influence on tissues distant from the injection site due to the active or passive migration of these injected nanoparticles through the vessels. The research is based on findings obtained when studying the samples of lungs, heart, spleen, and liver of outbred rabbits of both sexes weighing 3-4 kg at various times after the injection of EVs derived from MSCs of bone marrow origin and labeled by PKH26 into an artificially created defect of the proximal condyle of the tibia. MSC EVs were isolated by serial ultracentrifugation and characterized by transmission electron microscopy and flow cytometry. After the introduction of MSC EVs into the damaged proximal condyle of the tibia of rabbits, these MSC EVs can be found most frequently in the lungs, myocardium, liver, and spleen. MSC EVs enter all of these organs with the blood flow. The lungs contained the maximum number of labeled MSC EVs; moreover, they were often associated with detritus and were located in the lumen of the alveoli. In the capillary network of various organs except the myocardium, MSC EVs are adsorbed by paravasal phagocytes; in some cases, specifically labeled small dust-like objects can be detected throughout the entire experiment-up to ten days of observation. Therefore, we can conclude that the entire body, including distant organs, is effected both by antigenic detritus, which appeared in the bloodstream after extensive surgery, and MSC EVs introduced from the outside.

Point of care, bone marrow mononuclear cell therapy in ischemic heart failure patients personalized for cell potency: 12-month feasibility results from CardiAMP heart failure roll-in cohort

AIM

Heart failure following myocardial infarction (MI) is a potentially lethal problem with a staggering incidence. The CardiAMP Heart Failure trial represents the first attempt to personalize marrow-derived cell-based therapy to individuals with cell characteristics associated with beneficial responses in prior trials. Before the initiation of the randomized pivotal trial, an open-label "roll-in cohort" was completed to ensure the feasibility of the protocol's procedures.

METHODS

Patients with chronic post-MI heart failure (NYHA class II-III) receiving stable, guideline-directed medical therapy with a left ventricular ejection fraction between 20 and 40% were eligible. Two weeks prior to treatment, a ~ 5 mL bone marrow aspiration was performed to examine "cell potency". On treatment day, a 60 mL bone marrow aspiration, bone marrow mononuclear cell (BM MNC) enrichment and transendocardial injection of 200 million BM MNC's was performed in a single, point of care encounter. Patients were then followed to assess clinical outcomes.

RESULTS

The cell potency small volume bone marrow aspirate, the 60 mL bone marrow aspirate, and transendocardial injections were well tolerated in 10 patients enrolled. There were no serious adverse events related to bone marrow aspiration or cell delivery. Improvement in 6-min walk distance was observed at 6 months (+47.8 m, P = 0.01) and trended to improvement at 12 months (+46.4, P = 0.06). Similarly, trends to improved NYHA heart failure functional class, quality of life, left ventricular ejection fraction and recruitment of previously akinetic left ventricular wall segments were observed.

CONCLUSION

All CardiAMP HF protocol procedures were feasible and well tolerated. Favorable functional, echo and quality of life trends suggest this approach may offer promise for patients with post MI heart failure. The randomized CardiAMP Heart Failure pivotal trial is underway to confirm the efficacy of this approach.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT02438306.

Clinical Safety Profile of Transendocardial Catheter Injection Systems: A Plea for Uniform Reporting

OBJECTIVES

The aim of this study was to characterize the clinical safety profile of transendocardial injection catheters (TIC) reported in the published literature.

BACKGROUND

Transendocardial delivery is a minimally invasive approach to deliver potential therapeutic agents directly into the myocardium. The rate of adverse events across TIC is uncertain.

METHODS

A systematic search was performed for trial publications using TIC. Procedure-associated adverse event data were abstracted, pooled and compared across catheters for active treatment and placebo injected patients. The transendocardial injection associated serious adverse events (TEI-SAE) was defined as the composite of death, myocardial infarction, stroke or transient ischemic attack within 30 days and cardiac perforation causing death or requiring evacuation, serious intraprocedural arrhythmias and serious coronary artery or peripheral vascular complications.

RESULTS

The search identified 4 TIC systems: a helical needle (HN), an electro-anatomically tracked straight needle (EAM-SN), a straight needle without tracking elements (SN), and a curved needle (CN). Of 1799 patients who underwent transendocardial injections, the combined TEI-SAE was 3.4% across all catheters, and 1.1%, 3.3%, 7.1%, and 8.3% for HN, EAM-SN, SN and CN, respectively. However, TIC procedure duration and post procedural cardiac biomarker levels were reported in only 24% and 36% of published trials, respectively.

CONCLUSIONS

Transendocardial injection is associated with varied TEI-SAE but the data are very limited. The HN catheter appeared to be associated with lower TEI-SAE, versus other catheters. Procedure duration and post procedure cardiac biomarker levels were under-reported. Clearly, standardized, procedure-related event reporting for trials involving transcatheter delivery would improve our understanding of complications across different systems.

Key Success Factors for Regenerative Medicine in Acquired Heart Diseases

Stem cell therapy offers a breakthrough opportunity for the improvement of ischemic heart diseases. Numerous clinical trials and meta-analyses appear to confirm its positive but variable effects on heart function. Whereas these trials widely differed in design, cell type, source, and doses reinjected, cell injection route and timing, and type of cardiac disease, crucial key factors that may favour the success of cell therapy emerge from the review of their data. Various types of cell have been delivered. Injection of myoblasts does not improve heart function and is often responsible for severe ventricular arrythmia occurrence. Using bone marrow mononuclear cells is a misconception, as they are not stem cells but mainly a mix of various cells of hematopoietic lineages and stromal cells, only containing very low numbers of cells that have stem cell-like features; this likely explain the neutral results or at best the modest improvement in heart function reported after their injection. The true existence of cardiac stem cells now appears to be highly discredited, at least in adults. Mesenchymal stem cells do not repair the damaged myocardial tissue but attenuate post-infarction remodelling and contribute to revascularization of the hibernated zone surrounding the scar. CD34+ stem cells - likely issued from pluripotent very small embryonic-like (VSEL) stem cells - emerge as the most convincing cell type, inducing structural and functional repair of the ischemic myocardial area, providing they can be delivered in large amounts via intra-myocardial rather than intra-coronary injection, and preferentially after myocardial infarct rather than chronic heart failure.

Cell therapy trials for heart regeneration - lessons learned and future directions

The effects of cell therapy on heart regeneration in patients with chronic cardiomyopathy have been assessed in several clinical trials. These trials can be categorized as those using noncardiac stem cells, including mesenchymal stem cells, and those using cardiac-committed cells, including KIT⁺ cardiac stem cells, cardiosphere-derived cells, and cardiovascular progenitor cells derived from embryonic stem cells. Although the safety of cell therapies has been consistently reported, their efficacy remains more elusive. Nevertheless, several lessons have been learned that provide useful clues for future studies. This Review summarizes the main outcomes of these studies and draws some perspectives for future cell-based regenerative trials, which are largely based on the primary therapeutic target: remuscularization of chronic myocardial scars by exogenous cells or predominant use of these cells to activate host-associated repair pathways though paracrine signalling. In the first case, the study design should entail delivery of large numbers of cardiac-committed cells, supply of supportive noncardiac cells, and promotion of cell survival and appropriate coupling with endogenous cardiomyocytes. If the primary objective is to harness endogenous repair pathways, then the flexibility of cell type is greater. As the premise is that the transplanted cells need to engraft only transiently, the priority is to optimize their early retention and possibly to switch towards the sole administration of their secretome.

STAT3 Phosphorylation Mediating DMSO's Function on Fetal Cardiomyocyte Proliferation with Developmental Changes

Endogenous cardiac regeneration has been focused for decades as a potential therapy for heart diseases with cell loss, and dimethyl sulfoxide (DMSO) has been proposed as a treatment for many diseases. In this study, we aimed to investigate the function of DMSO on fetal cardiomyocyte proliferation. By tracing BrdU⁺/α actinin⁺ cells or Ki67⁺/α actinin⁺ cells with immunohistochemical staining, we found that DMSO remarkably promoted fetal cardiomyocytes proliferation, and at the late developmental stage (LDS), such effects were more efficient than that at early developmental stage (EDS). Western blot data revealed a significant increase in STAT3 phosphorylation under DMSO treatments at LDS, while not at EDS. Consistently, STAT3 phosphorylation blocker STA21 could greatly reverse DMSO's function at LDS whereas hardly at EDS. Moreover, hearts at the EDS had less total STAT3 protein, but relatively much higher level of phosphorylated STAT3. This suggests that DMSO promote fetal cardiomyocytes proliferation, and STAT3 phosphorylation play a pivotal role in DMSO's function. With maturation, DMSO exerted a better ability to favor cardiomyocyte proliferation depending on STAT3 phosphorylation. Therefore, DMSO could serve as an effective, economic, and safe therapy for heart diseases with cell loss.

Linking cell function with perfusion: insights from the transcatheter delivery of bone marrow-derived CD133+ cells in ischemic refractory cardiomyopathy trial (RECARDIO)

Background

Cell therapy with bone marrow (BM)-derived progenitors has emerged as a promising therapeutic for refractory angina (RA) patients. In the present study, we evaluated the safety and preliminary efficacy of transcatheter delivery of autologous BM-derived advanced therapy medicinal product CD133⁺ cells (ATMP-CD133) in RA patients, correlating perfusion outcome with cell function.

Methods

In the phase I “Endocavitary Injection of Bone Marrow Derived CD133⁺ Cells in Ischemic Refractory Cardiomyopathy” (RECARDIO) trial, a total of 10 patients with left ventricular (LV) dysfunction (ejection fraction ≤ 45%) and evidence of reversible ischemia, as assessed by single-photon emission computed tomography (SPECT), underwent BM aspiration and fluoroscopy-based percutaneous endomyocardial delivery of ATMP-CD133. Patients were evaluated at 6 and 12 months for safety and preliminary efficacy endpoints. ATMP-CD133 samples were used for in vitro correlations.

Results

Patients were treated safely with a mean number of 6.57 ± 3.45 ×  10⁶ ATMP-CD133. At 6-month follow-up, myocardial perfusion at SPECT was significantly ameliorated in terms of changes in summed stress (from 18.2 ± 8.6 to 13.8 ± 7.8, p = 0.05) and difference scores (from 12.0 ± 5.3 to 6.1 ± 4.0, p = 0.02) and number of segments with inducible ischemia (from 7.3 ± 2.2 to 4.0 ± 2.7, p = 0.003). Similarly, Canadian Cardiovascular Society and New York Heart Association classes significantly improved at follow-up vs baseline (p ≤ 0.001 and p = 0.007, respectively). Changes in summed stress score changes positively correlated with ATMP-CD133 release of proangiogenic cytokines HGF and PDGF-bb (r = 0.80, p = 0.009 and r = 0.77, p = 0.01, respectively) and negatively with the proinflammatory cytokines RANTES (r = − 0.79, p = 0.01) and IL-6 (r = − 0.76, p = 0.02).

Conclusion

Results of the RECARDIO trial suggested safety and efficacy in terms of clinical and perfusion outcomes in patients with RA and LV dysfunction. The observed link between myocardial perfusion improvements and ATMP-CD133 secretome may represent a proof of concept for further mechanistic investigations.

Trial registration

ClinicalTrials.gov, NCT02059681. Registered 11 February 2014.

The CardiAMP Heart Failure trial: A randomized controlled pivotal trial of high-dose autologous bone marrow mononuclear cells using the CardiAMP cell therapy system in patients with post-myocardial infarction heart failure: Trial rationale and study design

BACKGROUND

Heart failure following myocardial infarction is a common, disabling, and deadly condition. Direct injection of autologous bone marrow mononuclear cells into the myocardium may result in improved functional recovery, relieve symptoms, and improve other cardiovascular outcomes.

METHODS

CardiAMP-HF is a randomized, double-blind, sham-controlled, pivotal trial designed to investigate the safety and efficacy of autologous bone marrow mononuclear cells treatment for patients with medically refractory and symptomatic ischemic cardiomyopathy. The primary end point is change in 6-minute walk distance adjusted for major adverse cardiovascular events at 12 months following treatment. Particularly novel aspects of this trial include a cell potency assay to screen subjects who have bone marrow cell characteristics that suggest a favorable response to treatment, a point-of-care treatment method, a high target dose of 200 million cells, and an efficient transcatheter intramyocardial delivery method that is associated with high cell retention.

CONCLUSIONS

This novel approach may lead to a new treatment for those with ischemic heart disease suffering from medically refractory heart failure.

HCN4-Overexpressing Mouse Embryonic Stem Cell-Derived Cardiomyocytes Generate a New Rapid Rhythm in Rats with Bradycardia

A biological pacemaker is expected to solve the persisting problems of an artificial cardiac pacemaker including short battery life, lead breaks, infection, and electromagnetic interference. We previously reported HCN4 overexpression enhances pacemaking ability of mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) in vitro. However, the effect of these cells on bradycardia in vivo has remained unclear. Therefore, we transplanted HCN4-overexpressing mESC-CMs into bradycardia model animals and investigated whether they could function as a biological pacemaker. The rabbit Hcn4 gene was transfected into mouse embryonic stem cells and induced HCN4-overexpressing mESC-CMs. Non-cardiomyocytes were removed under serum/glucose-free and lactate-supplemented conditions. Cardiac balls containing 5 × 10³ mESC-CMs were made by using the hanging drop method. One hundred cardiac balls were injected into the left ventricular free wall of complete atrioventricular block (CAVB) model rats. Heart beats were evaluated using an implantable telemetry system 7 to 30 days after cell transplantation. The result showed that ectopic ventricular beats that were faster than the intrinsic escape rhythm were often observed in CAVB model rats transplanted with HCN4-overexpressing mESC-CMs. On the other hand, the rats transplanted with non-overexpressing mESC-CMs showed sporadic single premature ventricular contraction but not sustained ectopic ventricular rhythms. These results indicated that HCN4-overexpressing mESC-CMs produce rapid ectopic ventricular rhythms as a biological pacemaker.