Surfactant Protein A can Affect the Surface Tension of the Eustachian Tube and Macrophage Migration

Objective To assess the role and possible mechanism of surfactant protein A (SPA) in the pathogenesis of otitis media with effusion (OME). Methods This was a multi-part study with both an in vivo mouse model study as well as an in vitro study. The control and study groups (OME group) received phosphate-buffered saline and inactivated Streptococcus pneumoniae, respectively, via external auditory meatus injections. Changes in the surface tension of secretions from the eustachian tube (ET) and SPA expression were measured in both groups. A transwell assay was performed to observe the effect of different concentrations of SPA on the migration ability of macrophages. We examined the differentially expressed genes related to SPA-treated macrophages using RNA-seq analysis. Results On Day 3, the surface tension of the OME group was higher than that of the control group (p = 0.014). The variation intensity of SPA in the ET of the OME group was significantly lower than that of the control group (p < 0.001). Surface tension was correlated with SPA (r = -0.525, p = 0.037). The expression of SPA and macrophages in the ET was different between the two groups. In vitro experiments revealed that macrophages showed different migration abilities with SPA concentration changes (p < 0.05). RNA-seq and western blotting were performed after macrophages were treated with SPA. The results showed that RhoA and Rac1/2/3 were differentially expressed. Conclusions SPA can change the surface tension of secretions from the ET and affect macrophage migration to alter the function of the ET. Although research in this field of OME is nascent, initial work suggests that SPA likely plays an important role in OME progression. Level of Evidence NA Laryngoscope, 2022