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Andreas F. Zehnder, MD; Joe C. Adams, PhD; Peter A. Santi, PhD; Arthur G. Kristiansen, MA; Chitsuda Wacharasindhu, MD; Sabine Mann; Raghu Kalluri, PhD; Martin C. Gregory, MD; Clifford E. Kashtan, MD; Saumil N. Merchant, MD

Arch Otolaryngol Head Neck Surg. 2005;131:1007-1013.

Objective  To determine the distribution of 1, 3, and 5 chains of type IV collagen in the cochlea in Alport syndrome.

Design  Case-control study.

Patients  Two patients with sensorineural hearing loss due to Alport syndrome. Both patients had known mutations in the COL4A5 gene.

Main Outcome Measures  Immunostaining was used to study the distribution of type IV collagen (1, 3, and 5 chains) within the cochlea. Immunostaining was also performed in the cochlear tissues of an unaffected individual used as a control.

Results  In the control ear, 1 staining was observed in the basement membrane overlying the basilar membrane, in the basement membrane of cochlear blood vessels and Schwann cells, and within the spiral limbus. In the control ear, we also observed strong staining for 3 and 5 chains in the basement membrane overlying the basilar membrane and within the spiral ligament. In both cases with Alport syndrome, no immunostaining was observed for 3 or 5 chains within the cochlea, whereas 1 staining was present in locations similar to that seen in the control ear.

Conclusions  The results indicate that isotype switching does not occur within the cochlea in Alport syndrome. The results are also consistent with the hypothesis that the sensorineural hearing loss in Alport syndrome may be due to alterations in cochlear micromechanics and/or dysfunction of the spiral ligament.

Author Affiliations: Ear, Nose, and Throat Department, University Hospital Basel, Basel, Switzerland (Dr Zehnder); Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston (Drs Zehnder, Adams, Wacharasindhu, and Merchant, Mr Kristiansen, and Ms Mann); Department of Otology and Laryngology (Drs Adams and Merchant), Harvard Medical School, and Center for Matrix Biology, Department of Medicine, Beth Israel Deaconess Medical Center (Dr Kalluri), Boston; Departments of Otolaryngology and Neuroscience (Dr Santi) and Division of Pediatric Nephrology, Department of Pediatrics (Dr Kashtan), University of Minnesota, Minneapolis; and Department of Medicine, University of Utah Medical Center, Salt Lake City (Dr Gregory).