Strain dependent diffusivities of glucose and lactate in the human temporomandibular joint disc.

The temporomandibular joint (TMJ) disc is crucial in joint articulation and subjected to sustained compressive deformation during clenching. Compressive strain impedes metabolite diffusion in fibrocartilaginous tissues by reducing interstitial space and permeability. Due to its avascularity and metabolic demand, the TMJ disc is susceptible to nutrient insufficiency, making metabolite diffusivity essential for tissue homeostasis. This study quantified the effects of compressive strain on solute transport in human TMJ discs by determining glucose and lactate diffusivity under 0%, 10%, and 20% strain. TMJ discs were collected from cadaveric donors. Samples were prepared from the five regions of the disc and subjected to controlled confined compression within a diffusion chamber. Glucose and lactate diffusivities were determined from measured concentrations. Water volume fraction and glycosaminoglycan content were evaluated to characterize extracellular matrix composition. Computational Modeling simulated unloaded and mechanically loaded conditions to show effects of sustained loading on human TMJ disc's metabolic environment. Results from this study demonstrate that mechanical compression markedly limits glucose and lactate diffusivity, with diffusivity significantly decreasing as strain magnitude increased from 0% to 20%. Water volume fraction decreased as strain increased, correlating with restricted solute transport. No significant differences in diffusivities and water volume fraction between regions were found. Computational modeling revealed that mechanical loading elevated lactate concentrations while reducing glucose and oxygen concentrations and suppressing ATP synthesis. Comparisons with porcine studies indicated species-specific differences in strain-dependent diffusivities. These findings highlight the role of mechanical strain in modulating metabolite transport and cellular energy metabolism within human TMJ discs.