Development of contractile properties of minced muscle regenerates in the rat

Abstract

To test functional properties of regenerating skeletal muscle, the triceps surae muscles of 1-month-old rats were minced into 1-mm3 pieces and replaced. Myogenic cells originating from the degenerating implanted muscle fragments form a model of the original muscle and contractile activity is first detected after 7-8 days. Early regenerates exhibited contractile properties of very slow muscles. Contraction time speeded up until by 30-40 days it approached those of the normal fast muscles. The development of contractile function closely resembles that of normal muscles during the first postnatal weeks and it thus appears that the regenerating muscle undergoes a functional "developmental recapitulation." It is concluded that, despite a quantitative deficiency in the mass of regenerating muscle, those fibers which are present rapidly approach the normal condition in functional as well as morphological characteristics.