Similar characteristics and roles of human brain border immune cells in stem cell models

Postnatal transplantation of induced pluripotent stem cell-derived hematopoietic progenitors to the murine brain enables the functional study of human border-associated macrophages (BAMs).

• Human BAMs, or xenotransplanted BAMs (xBAMs), are found lining the leptomeninges and brain vasculature beyond the glia limitans.
• A conserved transcriptional signature differentiates BAMs from microglia, regardless of species origin, age, or genetic background.
• Both xBAMs and murine BAMs show a hyper-endocytic phenotype, which may enhance their ability to scavenge amyloid-beta (Aβ) compared to other brain macrophages.
• iPS-derived BAM-like cells (iBAMs) exhibit a hyper-endocytic phenotype and greater engulfment capacity than iPS-derived microglia-like cells (iMGLs).
• These findings suggest a conserved hyper-endocytic BAM phenotype that could be useful for studying human BAMs.

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