Characterization of trivalently crosslinked C-terminal telopeptide of
type I collagen (CTX) species in human plasma and serum using high
resolution mass spectrometry
Abstract
With an aging population, there has been significant progress in the
discovery and measurement of bone turnover biomarkers since the 2000s,
especially for monitoring skeletal diseases like osteoporosis. Multiple
markers derived from type I collagen, such as CTX, NTX, PINP, and ICTP,
have been developed. Extensive efforts have been devoted to
characterizing these molecules; however, their complex crosslinked
structures have posed significant analytical challenges, and to date,
these biomarkers remain poorly characterized. Previous attempts at
characterization involved gel-based separation methods and MALDI-TOF
analysis on collagen peptides directly extracted from bone. However,
using bone powder, while rich in collagen, does not represent the true
structure of the peptides in the biofluids. In this study, our goal was
to characterize plasma and serum CTX for subsequent LC-MS/MS method
development. We extracted and characterized type I collagen peptides
directly from human plasma and serum using a proteomics workflow that
integrates preparative liquid chromatography, affinity chromatography,
and high-resolution mass spectrometry. Subsequently, we successfully
identified numerous CTX species, providing valuable insights into the
characterization of these crucial biomarkers.