Fibroblast mitogenic activity of lung lavage fluid from infants with chronic lung disease of prematurity

Background: Lung fibrosis is thought to be important in chronic lung disease of prematurity (CLD). Methods: Fibroblast proliferative activity was assessed in 207 bronchoalveolar lavage fluid (BALF) samples from 43 infants. Sixteen developed CLD (birth weight 765 g (630-1230), gestation 26.5 weeks (23-29)), 18 developed respiratory distress syndrome (RDS) (birth weight 1415 g (430-4160), gestation 31 weeks (23-39)), and nine control infants (birth weight 21 10 g (900-3720), gestation 32 weeks (26-41)) received mechanical ventilation for non-pulmonary reasons. Results: The fibroblast proliferative activity relative to 10% fetal calf serum was 64-75% in infants with CLD, 55-86% in the RDS group, and 42-68% in control infants during the first 5 weeks of life. Only at day 3 was there a difference between the groups (CLD 72% v control 42%, p<0.01; RDS 63% v control 42%, p<0.05). With the use of neutralising antibodies, platelet derived growth factor BB PDGF-BB and epidermal growth factor were undetectable, and insulin-like growth factor I (IGF-I) accounted for 14% (p<0.05) and 11% (p<0.005) of BALF mitogenic activity from the RDS and CLD groups respectively. Conclusions: The mitogenic activity of BALF was similar in the three groups studied and was only partially accounted for by IGF-I. Growth factors other than PDGF-BB and IGF-I contribute significantly to this process.