Intravenous Followed by X-ray Fused with MRI-Guided Transendocardial Mesenchymal Stem Cell Injection Improves Contractility Reserve in a Swine Model of Myocardial Infarction

Preclinical Evaluation of the Safety and Efficacy of Cryopreserved Bone Marrow Mesenchymal Stromal Cells for Corneal Repair

Purpose

Mesenchymal stromal cells (MSCs) have been shown to enhance tissue repair as a cell-based therapy. In preparation for a phase I clinical study, we evaluated the safety, dosing, and efficacy of bone marrow–derived MSCs after subconjunctival injection in preclinical animal models of mice, rats, and rabbits.

Methods

Human bone marrow–derived MSCs were expanded to passage 4 and cryopreserved. Viability of MSCs after thawing and injection through small-gauge needles was evaluated by vital dye staining. The in vivo safety of human and rabbit MSCs was studied by subconjunctivally injecting MSCs in rabbits with follow-up to 90 days. The potency of MSCs on accelerating wound healing was evaluated in vitro using a scratch assay and in vivo using 2-mm corneal epithelial debridement wounds in mice. Human MSCs were tracked after subconjunctival injection in rat and rabbit eyes.

Results

The viability of MSCs after thawing and immediate injection through 27- and 30-gauge needles was 93.1% ± 2.1% and 94.9% ± 1.3%, respectively. Rabbit eyes demonstrated mild self-limiting conjunctival inflammation at the site of injection with human but not rabbit MSCs. In scratch assay, the mean wound healing area was 93.5% ± 12.1% in epithelial cells co-cultured with MSCs compared with 40.8% ± 23.1% in controls. At 24 hours after wounding, all MSC-injected murine eyes had 100% corneal wound closure compared with 79.9% ± 5.5% in controls. Human MSCs were detectable in the subconjunctival area and peripheral cornea at 14 days after injection.

Conclusions

Subconjunctival administration of MSCs is safe and effective in promoting corneal epithelial wound healing in animal models.

Translational Relevance

These results provide preclinical data to support a phase I clinical study.

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.

Human MuStem Cell Grafting into Infarcted Rat Heart Attenuates Adverse Tissue Remodeling and Preserves Cardiac Function

Myocardial infarction is one of the leading causes of mortality and morbidity worldwide. Whereas transplantation of several cell types into the infarcted heart has produced promising preclinical results, clinical studies using analogous human cells have shown limited structural and functional benefits. In dogs and humans, we have described a type of muscle-derived stem cells termed MuStem cells that efficiently promoted repair of injured skeletal muscle. Enhanced survival rate, long-term engraftment, and participation in muscle fiber formation were reported, leading to persistent tissue remodeling and clinical benefits. With the consideration of these features that are restricted or absent in cells tested so far for myocardial infarction, we wanted to investigate the capacity of human MuStem cells to repair infarcted hearts. Their local administration in immunodeficient rats 1 week after induced infarction resulted in reduced fibrosis and increased angiogenesis 3 weeks post-transplantation. Importantly, foci of human fibers were detected in the infarct site. Treated rats also showed attenuated left-ventricle dilation and preservation of contractile function. Interestingly, no spontaneous arrhythmias were observed. Our findings support the potential of MuStem cells, which have already been proposed as therapeutic candidates for dystrophic patients, to treat myocardial infarction and position them as an attractive tool for muscle-regenerative medicine.

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.

Quantitative Efficacy and Fate of Mesenchymal Stromal Cells Targeted to Cardiac Sites by Radiofrequency Catheter Ablation

Engraftment and functional integration of stem cells or stem cell-derived cells within cardiac tissue is an important prerequisite for cell replacement therapy aiming at the treatment of heart disease. Recently, a novel intravenous approach for application of mesenchymal stromal cells (MSCs) to cardiac sites has been established using radiofrequency catheter ablation (RFCA)-guided targeting, bypassing the need for open chest surgery or direct myocardial cell injection. However, little is known about the quantitative efficacy and longevity of this strategy. We performed selective power-controlled RFCA with eight ablation pulses (30 W, 60 s each) to induce heat-mediated lesions at the right atrial appendices (RAAs) of pigs. Different concentrations of human bone marrow-derived MSCs (10⁵ to 1.6 × 10⁶ cells/kg bodyweight) labeled with superparamagnetic iron oxide (SPIO) particles were infused intravenously in nine pigs one d after RFCA treatment and hearts were explanted 8 d later to quantify the number of engrafted cells. Prussian blue staining revealed high numbers of SPIO-labeled cells in areas surrounding the RFCA-induced lesions. Cell numbers were evaluated by quantitative real-time polymerase chain reaction using specific primers for human MSCs (hMSCs), which indicated that up to 10⁶ hMSCs, corresponding to ∼3.9% of the systemically applied human cells, engrafted within the RAAs of RFCA-treated pigs. Of note, infused hMSCs were observed in nontargeted organs, as well, but appeared at very low concentrations. To assess long-term deposition of MSCs, RAAs of three pigs were analyzed after 6 months, which revealed few persisting hMSCs at targeted sites. RFCA-mediated targeting of MSCs provides a novel minimal invasive strategy for cardiac stem cell engraftment. Qualitative and quantitative results of our large animal experiments indicate an efficient guidance of MSCs to selected cardiac regions, although only few cells remained at targeted sites 6 mo after cell transplantation.

Beneficial effects of mesenchymal stem cell delivery via a novel cardiac bioscaffold on right ventricles of pulmonary arterial hypertensive rats

Right ventricular failure (RVF) is a common cause of death in patients suffering from pulmonary arterial hypertension (PAH). The current treatment for PAH only moderately improves symptoms, and RVF ultimately occurs. Therefore, it is necessary to develop new treatment strategies to protect against right ventricle (RV) maladaptation despite PAH progression. In this study, we hypothesize that local mesenchymal stem cell (MSC) delivery via a novel bioscaffold can improve RV function despite persistent PAH. To test our hypothesis, we induced PAH in adult rats with SU5416 and chronic hypoxia exposure; treated with rat MSCs delivered by intravenous injection, intramyocardial injection, or epicardial placement of a bioscaffold; and then examined treatment effectiveness by in vivo pressure-volume measurement, echocardiography, histology, and immunohistochemistry. Our results showed that compared with other treatment groups, only the MSC-seeded bioscaffold group resulted in RV functional improvement, including restored stroke volume, cardiac output, and improved stroke work. Diastolic function indicated by end-diastolic pressure-volume relationship was improved by the local MSC treatments or bioscaffold alone. Cardiomyocyte hypertrophy and RV fibrosis were both reduced, and von Willebrand factor expression was restored by the MSC-seeded bioscaffold treatment. Overall, our study suggests a potential new regenerative therapy to rescue the pressure-overload failing RV with persistent pulmonary vascular disease, which may improve quality of life and/or survival of PAH patients. NEW & NOTEWORTHY We explored the effects of mesenchymal stem cell-seeded bioscaffold on right ventricles (RVs) of rats with established pulmonary arterial hypertension (PAH). Some beneficial effects were observed despite persistent PAH, suggesting that this may be a new therapy for RV to improve quality of life and/or survival of PAH patients.

Enhancement of Functionality and Therapeutic Efficacy of Cell-Based Therapy Using Mesenchymal Stem Cells for Cardiovascular Disease

Cardiovascular disease usually triggers coronary heart disease, stroke, and ischemic diseases, thus promoting the development of functional failure. Mesenchymal stem cells (MSCs) are cells that can be isolated from various human tissues, with multipotent and immunomodulatory characteristics to help damaged tissue repair and avoidance of immune responses. Much research has proved the feasibility, safety, and efficiency of MSC-based therapy for cardiovascular disease. Despite the fact that the precise mechanism of MSCs remains unclear, their therapeutic capability to treat ischemic diseases has been tested in phase I/II clinical trials. MSCs have the potential to become an effective therapeutic strategy for the treatment of ischemic and non-ischemic cardiovascular disorders. The molecular mechanism underlying the efficacy of MSCs in promoting engraftment and accelerating the functional recovery of injury sites is still unclear. It is hypothesized that the mechanisms of paracrine effects for the cardiac repair, optimization of the niche for cell survival, and cardiac remodeling by inflammatory control are involved in the interaction between MSCs and the damaged myocardial environment. This review focuses on recent experimental and clinical findings related to cardiovascular disease. We focus on MSCs, highlighting their roles in cardiovascular disease repair, differentiation, and MSC niche, and discuss their therapeutic efficacy and the current status of MSC-based cardiovascular disease therapies.

Role of Extracellular Matrix in Cardiac Cellular Therapies

The extracellular matrix (ECM) is an essential regulator of homeostasis at the cellular, tissue, and organ level. It is now very well known that ECM dynamic remodeling is indispensable not only for normal growth and development but also recovery from tissue injuries. Indeed, abnormal remodeling of the ECM plays a major role in many pathophysiological processes and contributes to many different pathologies including cardiovascular disorders. Recently, cellular therapies have emerged as a potential therapeutic strategy for restoration of lost cardiomyocytes or their rejuvenation after cardiac damage and injuries. Harnessing the biological properties of ECM could be a viable strategy to enhance the therapeutic effects of cellular therapies by improving the engraftment, integration, survival, and functional adaptation of newly transplanted cells in many different platforms. Conversely, transplanted cells could restore the functionality and original composition of damaged ECM by secreting and depositing new ECM or stimulating normal ECM production by cardiac tissue native cells. Although the ultimate role of cell therapy in treatment of cardiac disorders is still a matter of great debate, the potential utility of ECM in improving the therapeutic effect of transplanted cells and vice versa the potential role of cell therapy as a means to restore the structure and functionality of damaged ECM should be carefully considered in implementation of future clinical cardiovascular cell therapy trials.

Biodistribution and Clearance of Human Mesenchymal Stem Cells by Quantitative Three-Dimensional Cryo-Imaging After Intravenous Infusion in a Rat Lung Injury Model

To study three-dimensional (3D) cryo-imaging to measure cell biodistribution and clearance after intravenous infusion, the authors established a lung injury model in rats. Human mesenchymal stem cells (hMSCs) labeled with QTracker were infused via jugular vein. Organs were cryopreserved, followed by 3D cryo-imaging. At 60 minutes, 82 ± 9.7% of cells were detected, and at day 2, 0.06% of cells were detected. hMSCs were retained primarily in the liver, with fewer detected in lungs and spleen.

Cell tracking is a critical component of the safety and efficacy evaluation of therapeutic cell products. To date, cell-tracking modalities have been hampered by poor resolution, low sensitivity, and inability to track cells beyond the shortterm. Three-dimensional (3D) cryo-imaging coregisters fluorescent and bright-field microcopy images and allows for single-cell quantification within a 3D organ volume. We hypothesized that 3D cryo-imaging could be used to measure cell biodistribution and clearance after intravenous infusion in a rat lung injury model compared with normal rats. A bleomycin lung injury model was established in Sprague-Dawley rats (n = 12). Human mesenchymal stem cells (hMSCs) labeled with QTracker655 were infused via jugular vein. After 2, 4, or 8 days, a second dose of hMSCs labeled with QTracker605 was infused, and animals were euthanized after 60, 120, or 240 minutes. Lungs, liver, spleen, heart, kidney, testis, and intestine were cryopreserved, followed by 3D cryo-imaging of each organ. At 60 minutes, 82% ± 9.7% of cells were detected; detection decreased to 60% ± 17% and 66% ± 22% at 120 and 240 minutes, respectively. At day 2, 0.06% of cells were detected, and this level remained constant at days 4 and 8 postinfusion. At 60, 120, and 240 minutes, 99.7% of detected cells were found in the liver, lungs, and spleen, with cells primarily retained in the liver. This is the first study using 3D cryo-imaging to track hMSCs in a rat lung injury model. hMSCs were retained primarily in the liver, with fewer detected in lungs and spleen.

Significance

Effective bench-to-bedside clinical translation of cellular therapies requires careful understanding of cell fate through tracking. Tracking cells is important to measure cell retention so that delivery methods and cell dose can be optimized and so that biodistribution and clearance can be defined to better understand potential off-target toxicity and redosing strategies. This article demonstrates, for the first time, the use of three-dimensional cryo-imaging for single-cell quantitative tracking of intravenous infused clinical-grade mesenchymal stem cells in a clinically relevant model of lung injury. The important information learned in this study will help guide future clinical and translational stem cell therapies for lung injuries.