A recombinant fragment of human surfactant protein D reduces lung inflammation in preterm lambs

Background Bronchopulmonary dysplasia (BPD), the major chronic respiratory morbidity in extremely preterm infants, is largely driven by inflammation. Preterm lungs are deficient of surfactant protein D (SP-D), an immunomodulatory protein absent in current commercial surfactant preparations. We hypothesised that using a recombinant fragment of human SP-D (rfhSP-D) as an adjuvant to exogenous surfactant therapy would reduce ventilator-induced inflammation. Methods We utilised a preterm lamb model of ventilator-associated lung injury. Mechanically ventilated preterm lambs were randomised into control and two treated groups, receiving endotracheal surfactant at 15 min post-delivery. Physiological parameters were measured throughout the experiment. Lung tissue was analysed for changes in alveolar architecture and expression levels of pro-inflammatory cytokines. Bronchioalveolar lavage (BAL) was analysed for SP-D concentration, and inflammatory cells. Results Intratracheal administration of rfhSP-D improved respiratory outcomes, significantly increased airspace and lung compliance in treated groups. Treated lambs also showed a reduction in lung tissue gene expression of inflammatory cytokines and inflammatory cell counts. Conclusion Intratracheal administration of rfhSP-D did not negatively impact standard surfactant therapy and appeared to complement it. The administration of rfhSP-D as an adjuvant to standard surfactant therapy effectively reduced lung inflammation supporting the potential therapeutic use of rfhSP-D for preterm infants at risk of developing BPD. Impact We have successfully developed and tested a novel recombinant fragment of human surfactant protein D (rfhSP-D) capable of reducing ventilator-associated lung inflammation in a pre-term lamb model. These results suggest rfhSP-D may be a novel potentially useful therapy for Bronchopulmonary dysplasia (BPD) in combination with currently available surfactant replacement therapies and serves as justification for a first in human clinical trial in mechanically ventilated infants. If successful, rfhSP-D could become a therapeutic candidate to mitigate pulmonary inflammation and improve lung outcomes, potentially offering a novel therapeutic avenue in the prevention or management of BPD.