Vitamin C Deficiency Impairs Mineralization of Ossicle in Mice

Abstract

Objectives:

Vitamin C-deficient (VCD) mice develop spontaneous bone fractures and exhibit hearing loss. However, the effects on the micro-architecture of the ossicles and the underlying mechanisms have not been fully understood. In this study, we test the hypothesis that vitamin deficiency impairs osteoblast differentiation and function of the ossicles.

Methods:

The morphologic characteristics of the ossicles in VCD and wild-type mice were evaluated with a stereoscopic microscope. Micro-structure of the ossicles was analyzed by micro computed tomography (µCT). Osteoblast differentiation was determined by immunostaining of the bone marker gene, osteocalcin. Sound transmission along the ossicular chain was evaluated with laser Doppler vibrometer.

Results:

The ossicles in VCD mice demonstrated thinner bone in the manubrium of malleus and stapes footplate. µCT analyses further verified that the bone volume/total volume fraction (BV/TV) was significantly reduced in the stapes footplate (51.5 ± 3.9% vs 61.2 ± 1.5%; P < .05) and the manubrium of malleus (24.9 ± 5.3% vs 39.0 ± 5.0%; P < .05) in VCD mice. The expression of osteocalcin was significantly decreased in the ossicles of VCD mice (17.8 ± 3.3 vs 32.4 ± 4.7; P < .05). However, the preliminary data revealed a modest change in sound transmission along the ossicular chain.

Conclusions:

These findings suggest that VCD decreased expression of osteoblast differentiation marker, osteocalcin, and reduced bone volume and of the ossicles without significantly altering sound transmission. These results may indicate that the pathogenesis of VCD-induced hearing loss might be due to a deficiency at the inner ear or auditory neuron level. Further studies are warranted.