Neogenesis of skeletal muscle in the postinflammatory rat peritoneum

During the healing phase of a chemical peritonitis, one or several skeletal muscle fibers develop, de novo, in the peritoneum of the adult of weanling rat diaphragm. One week after the initial injury the new muscle fibers are narrow and have central nuclei and cross-striations. The fibers increase progressively in caliber and the nuclei take up a subsarcolemmal location. The newly formed muscle fibers are separated from the intrinsic diaphragmatic muscle by an elastic membrane and by a hand of hyaline connective tissue. They are separated from the peritoneal surface by a zone of granulation tissue. Most new fibers are oriented at right angles to the intrinsic diaphragmatic muscle fibers. Their location and orientation suggest an origin from mesothelium or from fibroblasts in the granulation tissue rather than from the intrinsic diaphragmatic muscle. A similar phenomenon can be induced in the pleura on the other side of the diaphragm. In contrast, damage to the diaphragmatic muscle by injection of aluminum lactate does not engender myogenesis in the location described despite active regeneration in the intrinsic muscle.