Hamster Bone Marrow Macrophages

Hamster Bone Marrow-Derived, Macrophage-Like Cells (Hambmdms) Express Macrophage Characteristics and Show High Phagocytic Capacity

The basis for differential susceptibility to Leishmania donovani infection remains poorly understood. To identify intrinsic cellular features contributing to host-specific outcomes, Jenkins et al. compared bone marrow-derived macrophages from susceptible hamsters (hamBMDMs) and resistant mice (mBMDMs).

Large-scale production of quiescent macrophages requires CSF1-mediated differentiation of BMPCs rather than primary cell isolation, which alters activation states. Adapting mBMDM protocols to hamsters-critical for visceral leishmaniasis research-is hindered by lack of autologous CSF1. They therefore screened alternative CSF1 sources (Fig. 1A). E. coli-derived recombinant CSF1 yielded poor recovery, whereas HEK293-produced rhCSF1 (100 ng/ml) supported robust differentiation, indicating post-translational modifications enhance activity (Fig. 1B). BHK conditioned medium achieved comparable recovery, with 60% improvement using rhCSF1 plus 5% CM. Differentiation was assessed by RT-qPCR for CD68, CSF1r, and CD14 using hamBMPCs as calibrator and hamPMs as controls (Fig. 1C). CD68 and CSF1r reached hamPM levels under all conditions, while CD14 remained lower-a known macrophage subpopulation heterogeneity. Using BHK cells as calibrator revealed high baseline CD14 in hamBMPCs, explaining modest enrichment. They selected rhCSF1 alone to avoid CM confounders (Fig. 1C). Comparative profiling of hamBMDMs, hamPMs, mBMDMs, and mPMs confirmed similar macrophage marker expression between species, with minimal fibroblast contamination (FSP1, CD90; Fig. 1D). Both BMDM types exhibited characteristic morphology-flat, irregular bodies with round-to-oval nuclei (Fig. 1E)-comparable to human PBMC-derived macrophages. Functional validation using fluorescent zymosan particles demonstrated equivalent phagocytic capacity, with 92% of both hamBMDMs and mBMDMs internalizing particles at lowest concentration (Fig. 1F, G). These results validate rhCSF1-differentiated hamBMDMs as bona fide macrophages that faithfully reproduce mBMDM morphology, gene expression, and phagocytic function, providing a robust platform for comparative studies of Leishmania susceptibility.