Mesenchymal stromal cells (MSCs) hold considerable promise in the treatment of ischemic heart disease. Most preclinical studies of MSCs for acute myocardial infarction (AMI) have been performed either in syngeneic animal models or with human cells in xenogeneic immunodeficient animals. A preferable pre-clinical model, however, would involve human MSCs in an immunocompetent animal.
AMI was generated in adult sheep by inducing ischemia reperfusion of the second diagonal branch. Sheep (n = 10) were randomized to receive an intravenous injection of human MSCs (1 × 106 cells/kg) or phosphate buffered saline. Cardiac function and remodeling were evaluated with echocardiography. Perfusion scintigraphy was used to identify sustained myocardial ischemia. Interaction between human MSCs and ovine lymphocytes was assessed by a mixed lymphocyte response (MLR).
Sheep receiving human MSCs showed significant improvement in myocardial perfusion at 1 month compared with baseline measurements. There was no change in ventricular dimensions in either group after 1 month of AMI. No adverse events or symptoms were observed in the sheep receiving human MSCs. The MLR was negative.
The immunocompetent ovine AMI model demonstrates the clinical safety and efficacy of human MSCs. The human cells do not appear to be immunogenic, further suggesting that immunocompetent sheep may serve as a suitable pre-clinical large animal model for testing human MSCs.