Evaluation of recombinant human SP-D in the rat premature lung model

The lungs of premature and term babies are structurally different from the adult lungs. Preterm lungs are underdeveloped, non-compliant in terms of breathing, often need mechanical ventilation and these patients commonly develop syndromes as a consequence of their prematurity, such as bronchopulmonary dysplasia (BPD). Surfactant protein SP-D could be a therapy for BPD. However, there is a need for an animal model that resembles the structural characteristics of premature lungs to test SP-D and future molecules that will target the newborn population. The aim of this study was to develop and validate a pre-clinical model of early alveolarization and structurally premature lungs in 10-day-old rats, and establish the dose safety and distribution of rhSP-D administered intratracheally to premature lungs.Ten-day-old Sprague Dawley rats were selected to develop the lung model. SP-D was administered intratracheally. Bronchoalveolar lavage fluid and lungs were collected to evaluate inflammation and SP-D distribution.The 10-day-old rat pup demonstrates early alveolarization features of premature lung development and it tolerates daily intratracheal injections for up to 14 days. The intratracheal administration of rhSP-D, at a dose of 8 mg/kg, does not induce an inflammatory response or histological signs of toxicity in the premature lung, even with a daily administration for 14 days. The pharmacokinetic distribution of rhSP-D in premature lungs has a half-life of ∼9 h, and the incorporation into blood is minimal.10-day-old rats are a good pre-clinical animal model of premature lungs, and rhSP-D can be intratracheally administered at doses up to 8 mg/kg without expecting adverse reactions.