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165 his is the first manuscript to demonstrate that skeletal myoblasts can develop into muscle tissue when grafted into injured rat heart. A cell suspension of fibroblasts and myoblasts (≥ 22% myoblasts as assessed by immunohistochemistry) was initially prepared and cultured from the limb muscles of 1-to 3-day-old Fischer rats. Freeze-thaw injury, using a pre-cooled aluminum rod, was then used to create a disc-shaped region of coagulation necrosis on the anterior surface of rodent left ventricle. Following this, the cells suspended in culture media were injected into the center of the injured myocardium. In group 1, injection immediately followed injury, while in group 2 it was delayed by 1 week. Shams consisted of freeze-thaw injury followed by saline injection. Rats in group 1 were examined between 1 day and 3 months and those in group 2 between 1 day and 7 weeks.

Using superfused myocardial strips harvested from the area of injury, force-voltage, and force-frequency relationships, Lmax, and fatigability were all determined. The force-voltage relationship was staircased, implying continued fiber recruitment and lack of electrical coupling. Such uncoupling could lead to areas of functional block and consequent dysrhythmia complicating the potential therapeutic utility of skeletal myoblasts.