NEOGENESIS OF SKELETAL-MUSCLE IN THE POSTINFLAMMATORY RAT PERITONEUM

During the healing phase of a chemical peritonitis, one or several ske letal muscle fibers develop, de novo, in the peritoneum of the adult o r weanling rat diaphragm. One week after the initial injury the new mu scle fibers are narrow and have central nuclei and cross-striations. T he fibers increase progressively in caliber and the nuclei take up a s ubsarcolemmal location. The newly formed muscle fibers are separated f rom the intrinsic diaphragmatic muscle by an elastic membrane and by a band of hyaline connective tissue. They are separated from the perito neal surface by a zone of granulation tissue. Most new fibers are orie nted at right angles to the intrinsic diaphragmatic muscle fibers. The ir 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 pleur a on the other side of the diaphragm. In contrast, damage to the diaph ragmatic muscle by injection of aluminum lactate does not engender myo genesis in the location described despite active regeneration in the i ntrinsic muscle. (C) 1994 Academic Press, Inc.