Nanomechanical and molecular characterization of aging in dentinal collagen

Abstract

Methylglyoxal (MGO) is an important molecule derived from glucose metabolism with the capacity of attaching to collagen and generating advanced glycation end-products (AGEs), which accumulate in tissues over time and are associated to aging and diseases. However, the accumulation of MGO-derived AGEs in dentin and their effect on the nanomechanical properties of dentinal collagen remain unknown. Thus, the aim of the present study was to quantify MGO-based AGEs in the organic matrix of human dentin as a function of age and associate these changes with alterations in the nanomechanical and ultrastructural properties of dentinal collagen. For this, twelve healthy teeth from <26 year-old and >50 year-old patients were collected and prepared to obtain crown and root dentin discs. Following demineralization, MGO-derived AGEs were quantified with a competitive ELISA assay. In addition, atomic force microscopy (AFM) nano-indentation was utilized to measure changes in elastic modulus in both peritubular (PT) and intertubular (IT) collagen fibrils. Finally, principal component analysis (PCA) was carried out to determine aging profiles for both crown and root dentin. Results showed increased presence of MGO AGEs in the organic matrix of dentin in the >50 year-old compared to <26 year-old samples in both crown and root. Furthermore, an overall increase in PT and IT collagen elasticity was observed in the >50 year-old group associated to ultrastructural changes in the organic matrix determined by AFM analysis. Furthermore, PCA loading plots suggested different aging profiles in both crown and root dentin, which could potentially have important therapeutic implications in restorative and adhesive dentistry approaches. Overall, these results demonstrate that the organic matrix of human dentin undergoes aging-related changes due to MGO-derived AGEs with important changes in nanomechanical behavior of collagen that may impact diagnostic and restorative procedures in the elderly.