Immunohistochemical distribution of surfactant apoprotein-A in congenital diaphragmatic hernia

The high mortality for congenital diaphragmatic hernia (CDH) has been attributed to a combination of pulmonary hypoplasia and persistent pulmonary hypertension. Recent experimental studies suggest that surfactant deficiency may also contribute to CDH pathophysiology. In this report, the authors immunohistochemically and morphometrically examined whether or not the hypoplastic lungs of CDH are associated with the immaturity of the surfactant system, especially alveolar type II cell function. Nine autopsy cases with CDH were immunohistochemically examined for the expression of surfactant apoprotein, using anti-IgG against human surfactant apoprotein A (SP-A), and the findings were compared with those in a gestational and postnatal age-matched control group. The lung/body weight ratio in the CDH was less than that in the controls (0.010 +/- 0.005 versus 0.021 +/- 0.013, P < .01). The radial alveolar count (RAC) of the CDH cases were also significantly less than that of the control cases (2.10 +/- 0.52 versus 3.48 +/- 0.39, P < .01). In the CDH cases, the RAC of the lung on the affected side were also significantly less than that of the lung on the unaffected side (1.71 +/- 0.34 versus 2.50 +/- 0.26, P < .01). In the immunohistochemical distribution of SP-A, compared with the control cases, the number of SP-A-positive cells on the alveolar septa of the CDH cases decreased in number, and this immunohistochemical reaction was weak even in positive type II cells. In addition, the immunoreaction observed in the alveolar type II cells of the unaffected side lungs in the four CDH cases was stronger than that of the unaffected side lungs. These results suggest that in the lungs of the CDH cases, especially on the affected side, there is a possible delay in both the structural growth and functional maturation or development of SP-A synthesis by alveolar type II cells, and this retardation of the functional maturation in alveolar type II cells is also considered to play a role in postnatal respiratory insufficiency in CDH patients.