Excessive local host-graft connectivity in aging and amyloid-loaded brain

Area of Science:

• Neuroscience
• Regenerative Medicine
• Neurodegenerative Diseases

Background:

• Cell transplantation holds promise for brain repair.
• Understanding how disease environments affect transplanted cells is crucial.
• Alzheimer's disease (AD) and aging present unique pathological conditions.

Purpose of the Study:

• To investigate the impact of amyloid pathology and aging on the connectivity of transplanted neurons.
• To analyze how the host disease environment influences graft integration and input.
• To identify molecular mechanisms underlying altered connectivity in disease states.

Main Methods:

• Monosynaptic rabies virus tracing was employed in APP/PS1 mice (modeling AD) and aged wild-type (WT) mice.
• Transplanted neurons were assessed for differentiation and integration into the host visual cortex.
• Deep proteome analysis using mass spectrometry was performed to identify molecular changes.

Main Results:

• Transplanted neurons successfully differentiated and integrated, receiving appropriate inputs.
• A significant, several-fold increase in local inputs to transplanted neurons was observed in both amyloid-loaded and aged environments.
• Complement system activation was identified as a common factor in both pathological conditions, correlating with increased local connectivity.

Conclusions:

• Host pathology, including amyloid deposition and aging, profoundly shapes the input connectome of transplanted neurons.
• Complement system activation is a key mediator of altered local connectivity in diseased brain environments.
• Results emphasize the need for caution when extrapolating findings across different pathological conditions in brain repair research.