Single cell RNA sequencing analysis of vestibular schwannoma reveals functionally distinct macrophage subsets

Background: Vestibular schwannomas (VS) remain a challenge due to their anatomical location and propensity to growth. Macrophages are present in VS but their roles in VS pathogenesis remains unknown. Objectives: Assess phenotypic and functional profile of macrophages in VS with single cell RNA sequencing (scRNAseq). Methods: scRNAseq was carried out in three VS samples to examine characteristics of macrophages in the tumor. RT-qPCR was carried out on ten VS samples for CD14, CD68 and CD163 and a panel of macrophage associated molecules. Results: scRNAseq revealed macrophages to be a major constituent of VS microenvironment with three distinct subclusters based on gene expression. The subclusters were also defined by expression of CD163, CD68 and IL-1ß. AREG and PLAUR were expressed in the CD68+CD163+IL-1ß+ subcluster, PLCG2 and NCKAP5 were expressed in CD68+CD163+IL-1ß- subcluster and AUTS2 and SPP1 were expressed in the CD68+CD163-IL-1ß+ subcluster. RT-qPCR showed expression of several macrophage markers in VS of which CD14, ALOX15, Interleukin-1ß, INHBA and Colony Stimulating Factor-1R were found to have a high correlation with tumor volume. Conclusions: Macrophages form an important component of VS stroma. scRNAseq reveals three distinct subsets of macrophages in the VS tissue which may have differing roles in the pathogenesis of VS. Overall design: single cell RNA sequencing analysis of vestibular schwannoma