Submyeloablative conditioning with busulfan permits bone marrow-derived cell accumulation in a murine model of Alzheimer's disease

Previous work has suggested that bone marrow (BM)-derived cells (BMDCs) accumulate within the CNS and could potentially associate with β-amyloid plaques in Alzheimer's disease (AD). To explore the accumulation of BMDCs in murine AD, we transplanted green fluorescent protein (GFP)-labeled BM cells into triple transgenic (3 × Tg) and wild-type (wt) mice using non-irradiative myelosuppresive conditioning with busulfan (BU). We find that BU (80 mg/kg) is sufficient to obtain adequate chimerism (>85%) in wt mice. In order to obtain appreciable non-irradiative chimerism in the 3 × Tg mice (>80%), anti-asialo ganglio-N-tetraosylceramide (α-ASGM-1) antibody was also used to reduce natural killer cell function and thereby abrogate the hybrid resistance of the 3 × Tg mouse strain. Using BU conditioning and α-ASGM-1 together, we observed sustained BM chimerism and BMDC accumulation within the CNS of the 3 × Tg and wt mice. In cortex and hippocampus, BMDC accumulation was perivascular in distribution and similar between 3 × Tg and wt mice, with no clear association between BMDCs and AD plaques. We conclude that non-irradiative BM chimerism can be achieved with BU in 3 × Tg mice, but requires α-ASGM-1 (or similar appropriate NK-cell depletion). Use of this chimerism protocol permits BMDCs accumulation in the CNS of mixed strain recipient mice although BMDCs appear to be largely perivascular within cortex and hippocampus.