To investigate whether blood cell-produced Aβ can enter the brain and induce AD-type pathology, 3-month-old C57BL/6J Wt mice were irradiated (8 Gy single-dose at ~0.4 Gy per minute from a gamma source) and then transplanted with BMCs from age- and gender-matched APP/PS1 mice (n = 9). Control experiments were performed by transplanting BMCs from Wt donors into irradiated Wt mice (n = 9). To assess the contribution of blood cell-produced Aβ to Aβ deposition in the brain, we reconstituted the bone marrow of 3-month-old APP/PS1 mice with BMCs from age- and gender-matched Wt mice (n = 14). Control experiments were performed by transplanting BMCs from APP/PS1 donors into irradiated APP/PS1 recipient mice (n = 10). BMT was performed following previously described procedures [15]. Briefly, donor BMCs were harvested from both the tibias and femurs of mice with RPMI medium 1640 basic. Then, ~1 × 107 BMCs in 200 μl were intravenously transplanted into irradiated recipients via the tail vein.

The above paragraph describes an experiment conducted to investigate whether blood cell-produced Aβ (Amyloid beta) can enter the brain and induce Alzheimer's Disease (AD) type pathology.

The experiment involved four groups of mice:

1. Wild type (Wt) mice that were irradiated and then transplanted with bone marrow cells (BMCs) from APP/PS1 mice. APP/PS1 mice are genetically modified to overproduce Aβ, a protein associated with Alzheimer's disease. There were 9 mice in this group.

2. As a control, Wt mice were irradiated and then transplanted with BMCs from other Wt mice. There were also 9 mice in this group.

3. APP/PS1 mice had their bone marrow reconstituted with BMCs from Wt mice. There were 14 mice in this group.

4. As a control, APP/PS1 mice were irradiated and then transplanted with BMCs from other APP/PS1 mice. There were 10 mice in this group.

The bone marrow transplantation was performed following previously described procedures. The BMCs were harvested from the tibias and femurs of the mice, and then approximately 10 million BMCs were intravenously transplanted into the irradiated recipients via the tail vein.

The purpose of this experiment was to assess the contribution of blood cell-produced Aβ to Aβ deposition in the brain, which is a characteristic of Alzheimer's disease.