Intermediate-size Expanded Access Program (EAP), Mesenchymal Stromal Cells (MSC) for Multisystem Inflammatory Syndrome in Children (MIS-C) Associated With Coronavirus Disease (COVID-19)

Inclusion Criteria 1. 2 months to 17 years of age, inclusive 2. Positive for current or recent SARS-CoV-2 (COVID-19) infection by real-time reverse transcription polymerase chain reaction (RT-PCR), serology, or antigen test; or COVID-19 exposure within the 4 weeks prior to the onset of symptoms AND no alternative plausible diagnoses 3. Presenting with: * Fever (\>38.0°C or \>100.4°F for ≥24 hours) or reporting subjective fever lasting ≥24 hours * Laboratory evidence of inflammation with high sensitivity C-reactive protein (hsCRP) ≥4.0 milligrams per deciliter (mg/dL) and associated abnormalities of at least one of the following: * elevated erythrocyte sedimentation rate (ESR) * elevated fibrinogen * elevated procalcitonin * elevated d-dimer * elevated ferritin * elevated lactic dehydrogenase (LDH) * elevated interleukin 6 (IL-6) * elevated neutrophils * reduced lymphocytes * low albumin * Clinically severe multisystem illness requiring hospitalization with evidence for cardiac involvement plus at least one other organ involvement (renal, respiratory, hematologic, gastrointestinal, dermatologic or neurological) * Cardiac involvement is defined as reduced left ventricular ejection fraction (\<55%) in addition to at least one of the following: * increased troponin I, * increased N-terminal pro-B-type natriuretic peptide (NT-proBNP) or BNP and/or * echocardiographic and/or other imaging evidence of left anterior descending coronary artery (LAD) and/or right coronary artery (RCA) dilation associated with a z-score \> 2.5 4. If on mechanical ventilation or ECMO, ≤72 hours post initiation of the respiratory support device Exclusion Criteria 1. Documented other microbial cause for MIS-C including bacterial sepsis, staphylococcal or streptococcal shock syndromes, or infections associated with myocarditis such as enterovirus. Of importance, waiting for results of these investigations should not delay initiation of remestemcel-L therapy. 2. Females who are pregnant or lactating 3. Body mass index (BMI) ≥40 kilograms per square meter (kg/m\^2) 4. Known hypersensitivity to dimethyl sulfoxide (DMSO) or to porcine or bovine proteins 5. Aspartate aminotransferase/alanine transaminase (AST/ALT) ≥5x upper limit of normal (ULN) 6. Creatinine clearance \<30 mL/min 7. Serum creatinine \>2 mg/dL 8. Any end-stage organ disease which in the opinion of the treating physician may possibly affect the safety of the remestemcel-L treatment.