Inclusion Criteria
* Phase 1A: Age greater than or equal to 18 years and less than 30 years (≥18 years, \<30 years).
* Phase 1B: Age greater than or equal to 4 years and less than 18 years (≥4 years, \<18 years)
* Subjects must be able to sign their own consent for Phase 1A of the study.
* Diagnosis of dilated cardiomyopathy (DCM) defined as
* Any Congenital Cardiac Malformation with systemic ventricular systolic dysfunction; Idiopathic Cardiomyopathy; Familial/Inherited and/or Genetic Cardiomyopathy; History of Myocarditis; Acquired (Chemotherapy, Iatrogenic, Infection, Rheumatic, Nutritional); Ischemic (e.g. Kawasaki Disease, post-operative); Left ventricular noncompaction; Coronary Artery Disease
* Left ventricular ejection fraction less than or equal to 45% documented by two-dimensional echocardiogram or cardiac MRI within the prior six months.
* Left ventricular dilation as defined by echocardiography left ventricular and end-diastolic dimension Z score \> +2.0
* Biventricular physiology with systemic left ventricle
* Must receive guideline directed heart failure as defined by the American Heart Association, American College of Cardiology, and Heart Failure Society of America 118
* Have been unresponsive or poorly responsive to at least 3 months of maximum guideline directed treatments.
Exclusion Criteria
* Listed for heart transplantation (as UNOS status 1A) or hospitalized while waiting for transplant (while on inotropes or with ventricular assist device)
* Cardiovascular surgery of percutaneous intervention to palliate or correct congenital cardiovascular malformations within 3 months of the screening visit. Patients anticipated to undergo corrective heart surgery during the 12 months after entry into Part 1A/1B.
* Previous heart transplant recipient
* Unoperated primary obstructive or severe regurgitant valve (aortic, pulmonary, or tricuspid) disease, or significant systemic ventricular outflow obstruction or aortic arch obstruction.
* Severe mitral valve disease
* Restrictive or hypertrophic cardiomyopathy
* Cardiogenic shock
* Currently on extracorporeal membrane oxygenation support
* Ventricular assist device support
* Lethal, uncontrollable arrhythmia defined as an arrhythmia resulting in hemodynamic instability requiring need for defibrillation, continuous intravenous anti-arrhythmic medication or mechanical circulatory support
* Patients with persistent atrial fibrillation requiring specific pharmacotherapy
* Amyloidosis
* Ischemic dilated cardiomyopathy
* Clinical history of malignant neoplasm within 5 years (with the exception of curatively treated basal cell carcinoma, squamous cell carcinoma, or cervical carcinoma)
* Serious neurologic disorder including loss of vision, stroke, or paralysis
* High-grade pulmonary embolism requiring interventional catheter procedure or pulmonary hypertension requiring use of pulmonary vasodilators including phosphodiesterase inhibitor or nitric oxide
* High-grade renal failure \[eGFR\<45\] mL/min/1.73 m2 - serum potassium \>5.3 mmol/L
* Multiple organ failure
* Non-cardiac condition that limits life span for \<1 year
* Uncontrolled diabetes (HbA1c \>9%) at screening
* Active infection (including endocarditis) requiring pharmacotherapy
* Sepsis
* Active hemorrhagic disease (e.g., gastrointestinal bleeding, injury)
* History of cardiac transplantation
* Immune system-altering medications, or immunosuppressive therapy at the time of enrolment or within the prior 12 weeks
* Dystrophin-associated cardiomyopathy confirmed by standard cardiomyopathy panel testing
* Confirmed myocarditis at time of screening
* Elevated LFTs greater than 2 times upper limit of normal at time of consent
* Elevated WBC greater than upper limit of normal as defined by local lab at time of consent
* Presence of HLA antibodies specific for therapeutic study product
* History of noncompliance, alcohol abuse, recreational drug use, or incarceration within the last year
* Currently pregnant or breastfeeding
