Poroelastic Bulk Properties of the Tectorial Membrane Measured with Osmotic Stress

Abstract

The equilibrium stress-strain relation and the pore radius of the isolated tectorial membrane (TM) of the mouse were determined. Polyethylene glycol (PEG), with molecular mass (MM) in the range 20-511 kDa, added to the TM bathing solution was used to exert an osmotic pressure. Strain on the TM induced by isosmotic PEG solutions of different molecular masses was approximately the same for MM > or = 200 kDa. However, for MM < or = 100 kDa, the TM strain was appreciably smaller. We infer that for the smaller molecular mass, PEG entered the TM and exerted a smaller effective osmotic pressure. The pore radius of the TM was estimated as 22 nm. The equilibrium stress-strain relation of the TM was measured using PEG with a molecular mass of 511 kDa. This relation was nonlinear and was fit with a power function. In the radial cochlear direction, the transverse stiffness of the TM was 20% stiffer in the inner than in the outer region. TM segments from the basal region had a larger transverse stiffness on average compared to sections from the apical-middle region. These measurements provide a quantitative basis for a poroelastic model of the TM.

Basilar Membrane and Tectorial Membrane Stiffness in the CBA/CaJ Mouse

“…To compare their data with values previously reported in the literature, Masaki et al used their longitudinal modulus data to estimate transverse stiffness. The transverse stiffness estimate was 0.009 N/m, which is close to the lower end of the previously published data (Masaki et al 2006). The value compares with the values obtained in this study.…”

“…Masaki and coworkers (Masaki et al 2006) used osmotic stress to determine the poroelastic bulk properties of the mouse TM. The equilibrium stressstrain relation of the TM was determined by adding polyethylene glycol (molecular weight of 511 kDa) to the bathing solution.…”

Electrokinetic properties of the mammalian tectorial membrane

“…This model predicts that electrostatic repulsion due to the −7.1 mmol/L of fixed charge density may contribute up to 0.35 kPa to the equilibrium bulk modulus κ, accounting for ∼70% of compressive rigidity of the TM at equilibrium (21). Under dynamic conditions, the contribution of charge to mechanical properties also is important.…”

“…However, these models exclude important phenomena, such as longitudinal coupling (17)(18)(19)(20), and assume that only mechanical properties of the TM are important. It now is clear that the TM is a biphasic poroelastic tissue (21), which manifests longitudinal coupling in the form of traveling waves (18)(19)(20).…”

“…Furthermore, TM macromolecules comprise not only mechanical constituents (21)(22)(23)(24)(25)(26) such as collagen fibrils, but also charged constituents such as glycosaminoglycans (GAGs), which might affect mechanical properties ( Fig. 1) (27)(28)(29)(30)(31)(32)(33)(34)(35).…”