Bone marrow-derived macrophage

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Bone-marrow-derived macrophages (BMDMs) are macrophage cells grown in the lab from mouse bone marrow. They become mature macrophages when exposed to M-CSF (CSF-1), a growth factor that tells bone marrow cells to become monocytes, which then turn into macrophages. To make BMDMs, researchers collect bone marrow from a mouse’s leg bones, remove cells already on other paths, and culture the remaining cells with CSF-1. Sometimes additional growth factors like IL-3 and IL-1 are added to boost yield and speed up differentiation. The process takes about 5–8 days, and millions of BMDMs can come from one mouse. They can also be frozen for long-term storage.

Once thawed, BMDMs respond to signals such as LPS, IFN-γ, and other stimuli. This triggers gene activity that makes cytokines and helps determine whether the macrophages behave as M1 (pro-inflammatory) or M2 (anti-inflammatory). If not frozen, BMDMs age and lose viability as CSF-1 and other nutrients in their medium decline. Their growth depends on CSF-1 signaling through its receptor, so blocking this pathway or using certain reagents can stop their proliferation. Also, without a maturation signal like LPS, monocytes can accumulate, which is less useful for macrophage-focused research.