Abstract
Background
Microglia and tumour associated macrophages (TAMs) constitute up to half of the total tumour mass of glioblastomas. Despite these myeloid populations being ontogenetically distinct, they have been largely conflated. Recent single-cell transcriptomic studies have identified genes that distinguish microglia from TAMs. Here we investigated whether the transcribed proteins of genes enriched in microglial or TAM populations can be used to differentiate these myeloid cells in immunohistochemically stained human glioblastoma tissue.
Methods
Tissue sections from resected low-grade, meningioma, and glioblastoma (grade IV) tumours and epilepsy tissues were immunofluorescently triple-labelled for Iba1 (pan-myeloid marker), CD14 or CD163 (preferential TAM-markers) and either P2RY12 or TMEM119 (microglial-specific markers). Using a single cell-based image analysis pipeline, we quantified the abundance of each marker within single myeloid cells, allowing the identification and analysis of myeloid populations.
Results
P2RY12 and TMEM119 successfully discriminated microglia from TAMs in glioblastoma. In contrast, CD14 and CD163 expression were not restricted to invading TAMs, and were upregulated by tumour microglia. Notably, a higher ratio of microglia-to-TAMs significantly correlated with increased patient survival.
Conclusions
We demonstrate the validity of previously defined microglial-specific genes P2RY12 and TMEM119 as robust discriminators of microglia and TAMs at the protein level in human tissue. Moreover, our data suggests that a higher proportion of microglia may be beneficial for patient survival in glioblastoma. Accordingly, this tissue-based method for myeloid population differentiation could serve as a useful prognostic tool.
ME-VAE: Multi-Encoder Variational AutoEncoder for Controlling Multiple Transformational Features in Single Cell Image Analysis
