Apoptosis in various organs of preterm infants: histopathologic study of lung, kidney, liver, and brain of ventilated infants.

Apoptosis, the well-characterized form of active programmed cell death, is a physiologic phenomenon in embryonal and fetal life in developing organs. Severe hypoxia, which occurs in most preterm infants, also leads to cell death, which may be necrotic or apoptotic. The aim of our study was to examine the incidence of apoptosis in various organs (such as lung, kidney, and brain) of preterm infants who suffered from clinically proven respiratory distress causing infantile respiratory distress syndrome (IRDS), cardiac failure, and periventricular leukomalacia (PVL). Twenty-four autopsy cases were studied histologically to detect the apoptotic ratio, which was performed on the basis of hematoxylin and eosin staining and validated by terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) reaction. Elevated apoptotic ratio was found in stages II, III, and IV of bronchopulmonary dysplasia (BPD) among alveolar and bronchiolar cells. The apoptotic activity was very low in stage I of BPD. High apoptotic ratio was detected in hypoxic injuries of the central nervous system (CNS) of preterm infants. Features of apoptosis were present in proximal and excreting tubules of the kidney. Significant elevation of apoptotic activity may play a role in the development of BPD, ischemic brain lesions, and renal failure.