MORPHOMETRIC CHARACTERIZATION OF THE FINE-STRUCTURE OF HUMAN TYPE-II PNEUMOCYTES

Background: Pulmonary type II pneumocytes have been examined by scanni ng electron microscopy (SEM), transmission electron microscopy (TEM), and morphometry in numerous mammals. Until now, the fine structure of the human type II pneumocyte has not been studied by means of morphome try. Methods: Eleven human donor lungs, which could not be made availa ble for a suitable recipient, were preserved with Euro Collins solutio n (ECS) according to clinical organ preservation techniques. The lungs were fixed via the airways. Systematic random samples were analyzed b y SEM, TEM, and classical stereological methods. Results: Type II pneu mocytes showed normal fine structural characteristics. Morphometry rev ealed that although inter-individual variation due to some oedematous swelling was present, the cells were in a normal size range as indicat ed by an estimated mean volume of 763 +/- 64 mu m(3). The volume densi ties were: nucleus 21.9 +/- 2.2%, mitochondria 5.8 +/- 0.9%, lamellar bodies 9.8 +/- 3.6%, and remaining cytoplasmic components 62.4 +/- 2.9 % of the cell volume. Since the inter-individual variations in the vol ume densities referred to the cell may, to variable degrees, reflect t he variation in the reference space, the volume densities referred to the constant test point system and the respective volume-to-surface ra tios were used for interindividual comparisons. These parameters indic ate that lamellar bodies were independent of cellular swelling, while mitochondria < nucleus < remaining cytoplasmic components increased in size with increasing cell size. Conclusions: Two to 7.5 hours of cold ischemia following ECS preservation do not deteriorate the fine struc ture of type II pneumocytes of human donor lungs. For reliable assessm ent of fine structural variations, morphometric parameters are require d that are independent of variations in cell size. (C) 1995 Wiley-Liss , Inc.