Basic Pattern of Tissue Repair in Human Lungs Following Unspecific Injury

¹ Department of Anesthesia, Inselspital, Bern, Switzerland
² Department of Anatomy, University of Bern, Bern, Switzerland

A method is described by which tissue samples from postmortem human lungs may be adequately fixed for electron microscopy.

An electron microscopy and morphometry study of lungs of patients dying of adult respiratory distress syndrome revealed that the alveolar epithelium was transformed to a vastly cuboidal epithelium irrespective of the inspired oxygen concentration, which in several cases did not exceed 40 percent. This constant change in alveolar epithelium, resulting in a consistent overall thickening of the epithelial barrier by a factor of 4:5 in all cases, was interpreted to represent a characteristic reaction pattern of alveolar epithelium to various kinds of injury. Arguments are presented to indicate that hypertrophy of cuboidal type 2 epithelial cells is a necessary step in the repair process, since type 1 cells are unable to divide by mitosis.