Concerted action of gammaherpesvirus infection and moderate hyperoxia on lung structural development including effects on critical lung fibroblast functions in neonatal mice.

BACKGROUND: The development of chronic lung disease, also known as Bronchopulmonary Dysplasia (BPD), is the most prevalent complication after premature birth. Viral infections are discussed to drive or aggravate lung disease, but only little is known about their role in BPD pathophysiology. We therefore used a preclinical model as well as primary neonatal mouse lung fibroblasts to study the impact of viral infection on disease development in the presence or absence of hyperoxia induced lung injury. METHODS: Neonatal C57BL/6 mice (PND 5-7) were infected with murine gammaherpesvirus-68 (MHV-68) by intranasal inoculation with or without pre-exposure to moderate hyperoxia (40%, 24 h). Next to the assessment of infection and replication (lytic and latent phase), lung histology and growth factor signaling were investigated together with indicators of proliferation and apoptosis early and late after infection. In vitro, these experiments were mirrored by exposing hyperoxia challenged and unchallenged primary neonatal mouse lung fibroblasts to MHV-68 (24 h). Analyses included cell function and developmentally relevant signaling. RESULTS: MHV-68 infection in neonatal mice resulted in acute lung inflammation early after infection, followed by histopathologic abnormalities at 5 months of age and altered growth factor signaling in hyperoxia and virus exposed mice. In primary neonatal mouse lung fibroblasts, MHV-68 infection impaired critical developmental functions including migration and proliferation together with a decrease in Pdgfr-α expression that was reproduced in vivo in the lung periphery. Interestingly, in vitro virus-induced effects were only partially augmented by pre-exposure to clinically relevant levels of hyperoxia. CONCLUSIONS: The present study highlights the potential of MHV-68 to perturb fibroblast functions with a critical role in structural lung development. These effects are virus-dependent with longer-term effects being partially augmented by oxygen exposure. Our pilot study is the first that combines a relatively mild virus infection with exposure to only moderate levels of oxygen and underscores the importance to identify and better understand early, pathophysiologically relevant insults that impact on the dynamics of lung development and the need to verify these drivers in clinical studies.