Elastic fiber‐mediated enthesis in the human middle ear

Abstract

Adaptation to constant vibration (acoustic oscillation) is likely to confer a specific morphology at the bonetendon and bone-ligament interfaces at the ear ossicles, which therefore represent an exciting target of enthesis research. We histologically examined (i) the bone attachments of the tensor tympani and stapedius muscles and (ii) the annular ligament of the incudostapedial joint obtained from seven elderly donated cadavers. Notably, both aldehyde-fuchsin and elastic-Masson staining demonstrated that the major fibrous component of the entheses was not collagen fibers but mature elastic fibers. The positive controls for elastic fiber staining were the arterial wall elastic laminae included in the temporal bone materials. The elastic fibers were inserted deeply into the type II collagen-poor fibrocartilage covering the ear ossicles. The muscle tendons were composed of an outer thin layer of collagen fibers and an inner thick core of elastic fibers near the malleus or stapes. In the unique elastic fiber-mediated entheses, hyaluronan, versican and fibronectin were expressed strongly along the elastic fibers. The hyaluronan seemed to act as a friction-reducing lubricant for the elastic fibers. Aggrecan was labeled strongly in a disk-or plica-like fibrous mass on the inner side of the elastic fiber-rich ligament, possibly due to compression stress from the ligament. Tenascin-c was not evident in the entheses. The elastic fibermediated entheses appeared resistant to tissue destruction in an environment exposed to constant vibration. The morphology was unlikely to be the result of age-related degeneration.

Hearing loss in ankylosing spondylitis

“…The possible mechanism of conductive HL could be arthritis of joints between the ossicles, defect in the supporting ligaments or the fixation of stapes footplate (otosclerosis). There are entheses in the middle ear which could possibly be involved in AS patients . To localize the cause of conductive HL in our patients we did impedance audiometry in 10 patients with conductive HL.…”

The Urethral Rhabdosphincter, Levator Ani Muscle, and Perineal Membrane: A Review

“…Unlike the usual interface or enthesis between locomotive structures, mechanical roles of elastic fibers have been described in the vocal cord as well as the joints between ear ossicle [11–13]. In these tissues, hyaluronan seems to play a critical role in lubrication between elastic fibers.…”

Expression of carbonic anhydrase in the fetal eye and extra-ocular tissues

“…We considered this set of substances as an essential minimum for discussion (e.g., Kawase et al, 2012). The staining for hyaluronan was performed using a biotinated hyaluronan binding protein (2 micro gram/ml; Seikagaku Corp, Tokyo, Japan) after immersion of sections in chondroitinase ABC (10 micron unit/ml; Sikagaku Corp, Tokyo, Japan) in 0.1 M tris-acetate buffer (pH 8.0, 37 C) during 30 min (Shibata et al, 2003).…”