The concept underlying cell therapy is that cells removed from a different part of the body can be transplanted into diseased tissue to restore decreased or lost function. Cardiac muscle is a good example for this approach since the remaining cardiomyocytes that survive following injury have an extremely limited ability to regenerate. Unlike cardiac muscle, skeletal muscle is capable of robust self-repair. The inability of cardiac muscle to self-repair is thought to be a consequence of the heart being deficient in a particular cell type called a myoblast. Myoblasts are small cells located between the basal lamina and sarcolemma in the skeletal muscle fiber. They respond to injury by extensive proliferation and can differentiate into nascent muscle, thereby providing a source for growth and repair. Myoblasts display a remarkable tolerance to reduced perfusion, making them a suitable choice for repair of ischemic heart disease. In particular, autologous skeletal myoblasts (ASM) are preferred since these are isolated from the same person into whom they will be later transplanted. This avoids many issues related to ethics and transplant rejection.

Autologous skeletal myoblast transplantation is not an approved therapy by the US Food and Drug Administration (FDA). Since it is considered an investigational new drug (IND), institutions participating in this type of human research must apply to the FDA for approval prior to screening for patients. In general, the acceptance criteria for entry into these studies require that patients have a documented previous myocardial infarction and an impaired left ventricular ejection fraction.

Autologous Skeletal Myoblast Isolation and Growth
The basic outline for ASM isolation and growth is as follows: a surgeon in a surgical suite makes an incision into the quadriceps muscle and aseptically removes a biopsy between 0.5g and 5g. The biopsy is placed in a transport solution and immediately taken to a tissue culture facility. Once inside a pre-irradiated laminar flow hood, the biopsy is removed and cut into small chunks approximately 1mm3 with sterile scissors. These chunks are placed into an enzymatic solution of digestive enzymes used to degrade extracellular matrix and connective tissue releasing individual cells. After the digestive process is complete, the enzymes are inactivated and the ASM are extensively washed to remove red blood cells and debris. At this point, the cells are resuspended in a rich medium containing growth factors and necessary nutrients and seeded onto cell culture dishes.The ASM are transferred to a 37ºC incubator and grown in high humidity until they reach approximately 70% to 80% confluency.ASM cultures must be carefully monitored and split before reaching confluency since they have a tendency to convert to fibroblasts that are not thought to be of therapeutic benefit. After two to three weeks, when a sufficient number of ASM have been grown, they are harvested, loaded into a syringe, and transported to the surgical suite where the patient awaiting cell transplantation has been prepared.