Modeling and simulation of osteocyte-interstitial fluid interaction in bone

Osteocytes are specialized bone cells responsible for sensing mechanical cues and directing bone remodeling. These cells reside in small cavities called lacunae within the bone matrix and extend dendritic processes through narrow channels known as canaliculi to connect with other osteocytes. Surrounding the cell and lining the lacuno-canalicular system is an interstitial fluid and cellular coating called the pericellular matrix (PCM). Previous studies have shown that the stress and strain required to elicit a significant response in osteocytes are approximately ten times greater than those typically experienced during normal physical activity. However, the mechanism by which macroscale mechanical signals are amplified to such levels within the osteocyte network is not yet fully understood. We develop coarse-grained models to investigate fluid-osteocyte interactions. These models incorporate key components of the osteocyte and its microenvironment, including the cell body (comprising the membrane/cortex, cytoskeleton, and cytosol), cellular processes, canaliculi, lacuna, interstitial fluid, and the surrounding bone matrix. The cell membrane is represented by a cross-linked viscoelastic fiber network arranged in triangular patterns. The cellular processes are modeled by discretized curves using damped elastic springs, while the cytoskeleton is constructed from tetrahedral elements, with each edge represented by a linearly viscoelastic fiber. Both the cytosol and interstitial fluid are treated as viscous, incompressible fluids. The surrounding bone is modeled as a rigid material. Both extracellular and intracellular flows are governed by the Navier-Stokes equations and numerically solved by the lattice Boltzmann method. The fluid-osteocyte interactions are simulated using the immersed boundary method. A key finding from our simulations is that stress and strain are highly concentrated at the junctions where the cellular processes connect to the main body of the cell.

Modeling and simulation of osteocyte-interstitial fluid interaction in bone

Monday, July 14 at 6:00pm

Luoding Zhu

"Modeling and simulation of osteocyte-interstitial fluid interaction in bone"

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