Aged-Related Fibroblast Activation Protein Expression in Skeletal Muscles Evaluated by PET Imaging

Area of Science:

• Oncology
• Radiology
• Gerontology

Background:

• Fibroblast activation protein (FAP) is key in cancer and tissue remodeling.
• FAP is also present in normal skeletal muscle.
• Its role in age-related muscle changes is not well understood.

Purpose of the Study:

• To investigate the relationship between FAP expression and age-related muscle characteristics.
• To utilize FAP inhibitor (FAPI) PET/CT imaging for this exploration.

Main Methods:

• Retrospective analysis of 54 cancer patients (lung and pancreatic) using FAPI PET/CT.
• Evaluation of imaging-based muscle features: SUVmean, SMI, and HU.
• Assessment of age-related FAP expression using GTEx dataset.
• Statistical analyses included Spearman's rank correlation and Kruskal-Wallis test.

Main Results:

• A positive correlation was found between FAPI SUVmean and age (ρ=0.368, p=0.006).
• Higher FAPI uptake was observed in older age groups, correlating negatively with muscle density (HU) (ρ=-0.298, p=0.029).
• GTEx data confirmed a significant age-related increase in FAP expression (p<0.001).

Conclusions:

• FAPI PET/CT reveals an age-related increase in skeletal muscle FAP uptake.
• This uptake is associated with decreased muscle density and increased fat infiltration.
• FAPI PET shows promise for evaluating age-related muscle health and quality.