Expression of intrapulmonary surfactant apoprotein-A in autopsied lungs: Comparative study of cases with or without pulmonary hypoplasia

To investigate the functional maturity of the lungs of infants with pulmona ry hypoplasia, we measured the expression of surfactant apoprotein-A (SP-A) in the autopsied lungs. Autopsied lungs were taken from 16 infants who die d at birth or soon after. A lung-to-body weight ratio of less than 1.2% was defined as pulmonary hypoplasia. Eight infants were classified as belongin g to the normal group, and eight as belonging to the pulmonary hypoplasia g roup. Many of the pulmonary hypoplasia group were complicated not only by p ulmonary hypoplasia, but also by amniotic fluid volume abnormalities or an anatomical malformation. We measured the expression of SP-A immunologically using murine anti-human SP-A MAb in the autopsied lung tissue, and subject ed the tissue to SP-A staining by the direct staining method. The expressio n of SP-A was assessed as one of four grades: -, +/-, 1+, 2+. The staining intensity of SP-A was high at if or stronger in five infants of the normal group. SP-A expression was significantly reduced, however, in all infants o f the pulmonary hypoplasia group except for one infant with normal amniotic fluid volume and relatively mild pulmonary hypoplasia. There was a signifi cant negative correlation between the staining intensity of SP-A and two fa ctors: pulmonary hypoplasia and abnormal amniotic fluid volume (p = 0.039 a nd p = 0.0063, respectively). In the present study, we demonstrated that SP -A expression was significantly reduced in infants with pulmonary hypoplasi a. We speculate that the functional maturity of the lungs of infants with p ulmonary hypoplasia is also suppressed.