Phenotype of in vitro human otosclerotic cells and its modulation by TGF beta.

A study was carried out to obtain a more detailed picture of the phenotypes of human otosclerotic and normal bone cells and to analyse the response of both populations to treatment with TGF beta 1. Total collagen synthesis was found to be decreased, but fibronectin secretion increased in otosclerotic with respect to normal cells. Although overall glycosaminoglycan (GAG) synthesis was lower in otosclerotic cells, the sulphated GAG to hyaluronic acid (HA) ratio was higher, in particular there was greater expression of chondroitin (CS) and dermatan sulphates (DS). TGF beta 1 induced a more marked increase in collagen and fibronectin release and greater production of sulphated GAGs as DS and heparan sulphate (HS) in the otosclerotic cells. The fact that the phenotype of the otosclerotic cells differed from that of the normal cells and could be modified by TGF beta 1 treatment, suggests that TGF beta 1 is implicated in the pathogenesis of otosclerosis.