Caduceus Clinical Trial One-Year Update


The CADUCEUS clinical trial, which stands for CArdiosphere-Derived aUtologous stem CElls, to reverse ventricUlar dySfunction) was the brainchild of Cedar-Sinai cardiologist Eduardo Marbán and his colleagues. 

This CADUCEUS trial used a heart-specific stem cell called CDCs or cardiosphere-derived cells to treat patients who had recently suffered a heart attack.  CDCs are extracted from the patient’s own heart and they can be grown in culture, expanded, and then implanted back into the patient’s heart. The initial assessments of those patients who had received the stem cell treatments was published in 2012 in the Journal Lancet (R.R. Makkar, R.R. Smith, K. Cheng et al. Intracoronary cardiosphere-derived cells for heart regeneration after myocardial infarction (CADUCEUS): a prospective, randomised phase 1 trial. Lancet, 379 (2012), pp. 895–904). The initial assessments of these patients showed shrinkage of their heart scars.  However, these patients showed regional improvements in heart function but no significant differences in global heart function.  Despite these caveats, the initial results were hopeful. 

Now the one-year follow-up of these patients has been published in the Journal of the American College of Cardiology.  The results of this examination are even more exciting.

CDCs were extracted from patients by means of heart biopsies of the inner part of the heart muscle (myocardium). After the cells were grown in culture to larger numbers, they were reintroduced to the hearts of the patients by means of “stop-flow” technique. This procedure utilizes the same technology as stents in that an over-the-wire balloon angioplasty catheter that was positioned in the blood vessels on the heart that were blocked. The figure below shows the cultured cardiospheres.

Specimen processing for human cardiosphere growth and CDC expansion. a, Schematic depicts the steps involved in specimen processing. b, Endomyocardial biopsy fragment on day 1. c, Explant 3 days after plating. d, Edge of explant 13 days after plating showing stromal-like and phase-bright cells. e, Cardiosphere-forming cells collected from the explant after 13 days and plated on poly-d-lysine for 2 days. f, Fully formed cardiospheres on day 25, 12 days after collection of cardiosphere-forming cells. g, CDCs during passage 2, plated on fibronectin for expansion. h and i, Cell growth is expressed as number of population doublings from the time of the first harvest for specimens from nontransplant patients (h) and specimens from transplant patients (i).
Specimen processing for human cardiosphere growth and CDC expansion. a, Schematic depicts the steps involved in specimen processing. b, Endomyocardial biopsy fragment on day 1. c, Explant 3 days after plating. d, Edge of explant 13 days after plating showing stromal-like and phase-bright cells. e, Cardiosphere-forming cells collected from the explant after 13 days and plated on poly-d-lysine for 2 days. f, Fully formed cardiospheres on day 25, 12 days after collection of cardiosphere-forming cells. g, CDCs during passage 2, plated on fibronectin for expansion. h and i, Cell growth is expressed as number of population doublings from the time of the first harvest for specimens from nontransplant patients (h) and specimens from transplant patients (i).

The initial assessment of these patients showed shrinkage of the heart scar and regional improvements in heart function. However in the one-year follow-up the scar showed even more drastic shrinkage (-11.9 grams or -11.1% of the left ventricle). Also, several of the indicators of global heart function showed substantial improvements (end-diastolic volume – -12.7 mls and end-systolic volume – -13.2 mls).

When it come to the all-important ejection fraction, which is the percentage of blood pumped from the left ventricle, the results are a little more complicated. When the ejection factions of each patient was compared with the size of their heart scars, there was a tight correlation between the increase in ejection fraction and the shrinkage of the heart scar. See the figure below for a scatter plot of ejection fraction versus heart scar size.

(A) Scatterplot showing the natural relationship between scar size and left ventricular ejection fraction ∼5 months post-myocardial infarction (circles). Each cross symbol represents the mean values (at the intersection of the vertical and horizontal bars [obtained from all patients with magnetic resonance imaging measurements]), whereas the width of each bar equals ±SEM of scar size and left ventricular ejection fraction of CADUCEUS patients at baseline, 6 months, and 1 year; the crosses are superimposed onto the scatterplot showing prior data from post-myocardial infarction patients with variable scar sizes. The changes in left ventricular ejection fraction in CDC-treated subjects are consistent with the natural relationship between scar size and ejection fraction in convalescent myocardial infarction, whereas the changes in left ventricular ejection fraction in controls fall within the margins of variability. (B) Changes in end-diastolic volume from baseline to 1 year. (C) Changes in end-systolic volume from baseline to 1 year. CDCs = cardiosphere-derived cells; EDV = end-diastolic volume; EF = ejection fraction; ESV = end-systolic volume; LV = left ventricle.
(A) Scatterplot showing the natural relationship between scar size and left ventricular ejection fraction ∼5 months post-myocardial infarction (circles). Each cross symbol represents the mean values (at the intersection of the vertical and horizontal bars [obtained from all patients with magnetic resonance imaging measurements]), whereas the width of each bar equals ±SEM of scar size and left ventricular ejection fraction of CADUCEUS patients at baseline, 6 months, and 1 year; the crosses are superimposed onto the scatterplot showing prior data from post-myocardial infarction patients with variable scar sizes. The changes in left ventricular ejection fraction in CDC-treated subjects are consistent with the natural relationship between scar size and ejection fraction in convalescent myocardial infarction, whereas the changes in left ventricular ejection fraction in controls fall within the margins of variability. (B) Changes in end-diastolic volume from baseline to 1 year. (C) Changes in end-systolic volume from baseline to 1 year. CDCs = cardiosphere-derived cells; EDV = end-diastolic volume; EF = ejection fraction; ESV = end-systolic volume; LV = left ventricle.

Other observations included safety assessments. When the number of adverse events between the control group and CDC-receiving group were measured, there were no differences between the two groups. The patients in the CDC-receiving group were more likely to be hospitalized and had transient cases of fast heartbeats, and there was also one death in this group. However the incidence of these events were not statistically different from the control group.

From these assessments, it is clear that the CDC treatments are safe, and decreased the scar size and regional function of infarcted heart muscle. From these results, the researchers state that “These findings motivate the further exploration of CDCs in future clinical studies.

Reducing the Heart Scar After a Heart Attack


After a heart attack, inflammation in the heart kills off heart muscle cells and fibroblasts in the heart make a protein called collagen, which forms a heart scar. The heart scar does not contract and does not conduct electrochemical signals. The scar will contract over time, but its presence can lead to abnormal heart rhythms, also known as arrhythmias. Arrythmias can be fatal, since they can cause a heart attack. To prevent a heart attack, physicians will treat heart attack patients with a group of drugs called beta-blockers that slow down the heart rate and protect the heart from the deleterious effects of norepinephrine (secreted by the sympathetic nerve inputs to the heart). An alternative treatment is digoxin or digitalis, which is a chemical found in foxglove. Digitalis inhibits ion pumps in heart muscle cells and slows the heart and the force of its contractions. Digitalis, however, interacts with a whole shoe box fill of drugs, has a very long half-life, and is hard to dose. Therefore it is not the first choice.

Given all this, helping the heart to make a smaller heart scar is a better strategy for treating a heart after a heart attack. To accomplish this, you need to inhibit the heart fibroblasts that make the heart scar in the first place. Secondly, you must move something into the place of the dead cells. Otherwise, the heart could burst or scar tissue will move into the area anyway.

To that end, Yigang Wang and his colleagues at the University of Cincinnati Medical Center in Ohio have published an ingenious paper in which they tried two different strategies to reduce the size of the heart scar, which concomitantly increased the colonization of the heart by induced pluripotent stem cells engineered to express a sodium-calcium exchange pump.

Previously, Wang and his colleagues used a patch to heal the heart after a heart attack. The patch consisted of endothelial cells, which make blood vessels, induced pluripotent stem cells engineered to make a sodium-calcium exchange pump called NCX1, and embryonic fibroblasts. This so-called tri-cell patch makes new blood vessels, establishes new heart muscle, and the foundational matrix molecules to form a platform for beating heart muscle.

In order to get these cells to spread throughout the injured heart, Wang and others used a reagent that specifically inhibits heart fibroblasts. They used a small non-coding RNA molecule. A group of microRNAs called miR-29 family are downregulated after a heart attack. As it turns out, these microRNAs inhibit a group of genes that involved in collagen deposition. Therefore, by overexpressing miR-29 microRNAs, they could prevent collagen deposition and reduce scar formation.

The experimental design in this paper is rather complex. Therefore, I will go through it slowly. First, they tried to overexpress miR-29 microRNAs in cultured heart fibroblasts and sure enough, they inhibited collagen synthesis. Cells overexpressing miR-29 made less than a third of the collagen of their normal counterparts. When they placed these fibroblasts into the heart and induced heart attacks, again, they made significantly less collagen when they were expressing miR-29.

Then they used their miR-29 RNAs by injecting them directly into the heart before inducing a heart attack, and then after the heart attack, they applied the tri-patch. Their results were significant. The scar size was smaller (almost one-third the size of the controls), and the density of blood vessels was much higher in the tri-patched hearts treated with miR-29. The induced pluripotent stem cells differentiated into heart muscle cells and spread throughout the heart. Heart function measures also consistently went up too.  The echiocardiograph before more normal, the ejection fraction went up, the % shortening of the heart muscle fibers was increased, and the relaxation phase of the heart (diastole) also was not so puffy (see graphs and figures below).

(A): M-mode echocardiograph data in three groups. (B): Quantification analysis for heart function. Quantitative data for LVDd (B-1), LVDs (B-2), EF (B-3), and FS (B-4) 4 weeks after Tri-P implantation. *p,0.05 vs. Ctrl+MI+Tri-P group; {p,0.05 vs. Anti-29b+MI+Tri-P group. LVDd, left ventricular enddiastolic diameters; LVDs, left ventricular end-systolic diameters; EF, ejection fraction index; FS, fractional shortening. All values expressed as mean 6 SEM. n = 6 for each group. (C): Two-D mode echocardiograph data in three groups, analyzed by long-axis and short-axis views. *p,0.05 vs. Ctrl+MI+Tri-P group; {p,0.05 vs. miR-29b+MI+Tri-P group. Ctrl, control mimic pretreatd rat with Tri-cell patch graft; miR-29b, miR- 29b mimic pretreated rat with Tri-cell patch graft; Anti-29b, miR-29b inhibitor pretreated rat with Tri-cell patch graft. White dotted lines indicate endocardium and epicardium.
(A): M-mode echocardiograph data in three groups. (B): Quantification analysis for heart function. Quantitative data for LVDd (B-1), LVDs (B-2), EF (B-3), and FS (B-4) 4 weeks after Tri-P implantation. *p,0.05 vs. Ctrl+MI+Tri-P group; {p,0.05 vs. Anti-29b+MI+Tri-P group. LVDd, left ventricular enddiastolic diameters; LVDs, left ventricular end-systolic diameters; EF, ejection fraction index; FS, fractional shortening. All values expressed as mean 6 SEM. n = 6 for each group. (C): Two-D mode echocardiograph data in three groups, analyzed by long-axis and short-axis views. *p,0.05 vs. Ctrl+MI+Tri-P group; {p,0.05 vs. miR-29b+MI+Tri-P group. Ctrl, control mimic pretreatd rat with Tri-cell patch graft; miR-29b, miR-29b mimic pretreated rat with Tri-cell patch graft; Anti-29b, miR-29b inhibitor pretreated rat with Tri-cell patch graft. White dotted lines indicate endocardium and epicardium.

There is a cautionary note to this study. Inhibiting collagen formation after a heart attack could create soft fragile regions of the heart that are subject to rupture should the vascular systolic pressure increase. While that threat was not observed in this study, human hearts, which are much larger, would be much more susceptible to such a mishap. Therefore, while this study is interesting and suggest a strategy in humans, it requires more testing and refinement before anyone can even think about applying it to humans.