Age-Related Changes in Matrix Metalloproteinase-9 Expression in Spinal Motor Neurons of Normal Mice

Area of Science:

• Neuroscience
• Molecular Biology
• Aging Research

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting motor neurons (MNs).
• The exact cause of MN degeneration in ALS remains unknown, but certain MN types are preserved.
• Adenosine deaminase acting on RNA 2 (ADAR2) deficiency contributes to ALS pathogenesis by affecting GluA2 Q/R site editing.

Purpose of the Study:

• To investigate the expression patterns and role of matrix metalloproteinase-9 (MMP-9) in normal aging and its potential link to ALS.
• To determine if MMP-9 serves as a marker for vulnerable motor neurons.

Main Methods:

• Generated mice with selective ADAR2 knockout in cholinergic neurons (AR2 mice) to model ALS.
• Analyzed MMP-9 expression in spinal motor neurons of normal mice at six and 12 months of age.
• Examined the relationship between MMP-9, aging, and TAR DNA-binding protein 43 (TDP-43) pathology.

Main Results:

• Motor neuron numbers and MMP-9 positive motor neurons decreased with age in normal mice.
• Aging induced abnormal TDP-43 localization in MMP-9 positive motor neurons, indicating vulnerability.
• ADAR2 deficiency in AR2 mice led to increased death of fast-fatigable motor neurons (FF MNs), similar to aging.

Conclusions:

• MMP-9 is a marker for fast-fatigable motor neurons and potentially for motor neurons prone to degeneration.
• MMP-9 may serve as an early degeneration marker in physiological aging and age-related diseases like ALS.
• Further investigation of MMP-9 in ALS patients and models is crucial for understanding disease pathogenesis.