Mass Spectrometry Characterization of the Human Ankle and Hindfoot Fracture Microenvironment in Young and Aged Subjects

Bone regeneration following a fracture is dependent on multiple factors including skeletal stem cells (SSCs). Recruitment, proliferation, and differentiation of the SSCs is guided by the proteins and metabolites found within the fracture microenvironment. Understanding how intrinsic factors affect the fracture microenvironment has been a topic of ongoing investigation. This study sought to determine whether the levels of select proteins and metabolites within the fracture hematoma would be differentially expressed depending on the age of the patient. We hypothesized that a distinct set of proteins and metabolites found within the fracture hematoma microenvironment would be present at varying levels depending on patient age.

The research study was reviewed and approved by an Institutional Review Board. Hematomas were collected from subjects aged 18 years old or older undergoing surgical intervention for a fracture. Hematoma samples were selected from the biorepository and assigned to one of two fracture groups including young ankle/hindfoot and aged ankle/hindfoot. Protein and metabolite levels within each hematoma were analyzed by liquid chromatography-mass spectrometry.

A total of seven hematomas were included in each the young ankle/hindfoot and aged ankle/hindfoot groups. From the global metabolomic analysis, creatine, 2-methylindoline, and acetyl-L-carnitine were identified as being differentially expressed between both groups. An untargeted metabolomic analysis of the two groups identified significant differences in the levels of an additional 66 metabolites. Proteomic analysis identified 34 proteins that were expressed at significantly different levels.

The level of metabolites and proteins found within the local fracture environment vary by patient age. Future investigations will focus on identifying a role for these proteins and metabolites in bone homeostasis and fracture healing.

N/A, basic science investigation.