Water dynamics in mammalian bone

Water constitutes 10% of mammalian bone tissues and is as such the third major component after hydroxyapatite crystals (70%) and collagen (20%). Besides nutrient and waste transport, water assists in conferring to bone its unique mechanical properties, making it a promising clinical marker of fracture risk. Indeed, Bound water protects collagen and makes bone less susceptible to fracture in the event of external stress while free water molecules are associated with bone strength (hydraulic stiffening). However, measuring bound and free water overlooks the dynamical interplay between these two populations and how this equilibrium changes across multiple length scales.

Water pathways within the various levels of organization of bone tissues, from liquid in cortical pores to loosely or tightly bound in the mineral lattice. Understanding the material properties of bone demands detailed treatment of the structure of dynamics of water from the anatomical length scale all the way down to the atomic.

The goal is to build an accurate model of the water chemistry in bone tissues and characterize its change with mineral composition. From structures of collagen/water,  hydroxyapatite/water or collagen/hydroxyapatite interfaces, we simulate water dynamics within a mixed collagen-hydroxyapatite matrix. Relevant to many burgeoning fields such as regenerative medicine and aging research, predicting the hardness of bone via its water content can assist the design of implants or slow the aging process associated with osteoporosis.