Cellular retinol-binding protein type I is prominently and differentially expressed in the sensory epithelium of the rat cochlea and vestibular organs.
To understand the possible role of retinoic acid during inner ear development and cellular regeneration, we have examined the expression pattern of two intracellular retinoid-binding proteins, the cellular retinol- and retinoic acid-binding proteins of type I in the developing and mature rat inner ear. Expression of cellular retinol-binding protein type I was seen in the supporting cells of the organ of Corti and vestibular organs as soon as the first signs of differentiation of the adjacent hair cells were seen. In the developing organ of Corti, the expression pattern followed the basal-to-apical coil differentiation gradient. After the 1st postnatal week, detectable expression of cellular retinol-binding protein type I disappeared from the organ of Corti, but persisted in the supporting cells of vestibular organs throughout life. Expression of cellular retinoic acid-binding protein type I was not found in the inner ear sensory epithelia. Cellular retinol-binding protein type I has previously been shown to act as a substrate carrier in the synthesis of retinoic acid from its precursor, retinol. Our data suggest that retinoic acid is synthesized in the developing sensory epithelium of the cochlear and vestibular organs and that a concentration gradient formed by retinoic acid may have a role in differentiation of the cochlear sensory epithelium. Furthermore, retinoic acid may have a role in damage-induced hair cell regeneration in the developing and mature vestibular organs as well as in the developing auditory organ. The absence of cellular retinol-binding protein type I from the supporting cells of the mature organ of Corti may be associated with the inability of this organ to regenerate hair cells after damage.
Ylikoski
J
J
Department of Otolaryngology, University of Kuopio, Finland.
Pirvola
U
U
Eriksson
U
U
D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D003051:Cochlea / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D005314:Embryonic and Fetal Development; D004848:Epithelium / Q000378:metabolism; D005333:Fetus / Q000378:metabolism* / Q000502:physiology; D006198:Hair Cells, Auditory / Q000502:physiology; D007150:Immunohistochemistry; D009416:Nerve Regeneration; D051381:Rats; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D054840:Retinol-Binding Proteins, Cellular; D012677:Sensation / Q000502:physiology*; D014722:Vestibule, Labyrinth / Q000166:cytology / Q000378:metabolism*
C518458:Rbp1 protein, rat; D018168:Receptors, Retinoic Acid; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; C082927:retinoic acid binding protein I, cellular