The individual variation may also relate to differential Aβ clearance in 2D and 3D systems. Compared to four subjects AD2-5, we found relatively higher Aβ levels in 2D neuronal culture derived from subject AD1 (Fig 7); however, this difference was diminished in 3D culture (Fig 9). While we do not have a clear understanding of this difference, this phenomenon could be related to Aβ clearance. In 2D neurons, Aβ clearance may be reduced in subject AD1, leading to higher levels of Aβ remaining in the system. Aβ clearance among five 3D neuronal lines might be similar, and no significant difference could be observed. Such cell functional variations between 2D and 3D neuronal culture are critical pieces of the puzzle; linking them together will improve our understanding of the outcomes of drug trials in individual-derived neuronal cultures and support the development of pharmacogenetic markers for AD treatment. Our pilot study included only five subjects, and additional subjects will be required to generate sufficient power to probe for genetic markers. Nevertheless, the methodology we developed here can be readily expanded.
