Neurochemical Research, Vol. 23, No. 8, 1998, pp. 1133-1138 Expression of Growth Factors and Their Receptors in the Postnatal Rat Cochlea Brigitte Malgrange, 1,5 Bernard Rogister, 1 Philippe P. Lefebvre, 1,2 Cecile Mazy-Servais, 1 Andrew A. Welcher, 4 Christophe Bonnet, 1 Rou-Yin Hsu, 4 Jean-Michel Rigo, 1 Thomas R. Van De Water, 2,3 and Gustave Moonen 1 (Accepted December 17, 1997) RT-PCR was used to assay for growth factors and receptors from seven different protein families in cochlea tissues of the juvenile rat. There was a broad representation of the growth factor families in all the cochlea tissues examined, though the organ of Corti and stria vascularis expressed a greater variety than the spiral ganglion. This broad expression suggests that a variety of known growth factors play significant roles in the development, maintenance, and repair of the inner ear. The results of this survey serve as a basis for the design of future in vitro experiments that will address the ability of growth factors to protect hair cells from damage and to evoke a repair- regeneration response by injured hair cells. KEY WORDS: Cochlea; growth factors; stria vascularis; organ of corti; spiral ganglion. INTRODUCTION There is increasing evidence that growth factors play key roles in development and maintenance of the neurosensory components of the peripheral auditory sys- tem. This is well established regarding the neural com- ponent, i.e. NT-3 supports the survival of more than 80% of the auditory neurons in the spiral ganglion (1). There is also suggesting evidence that growth factors are important for the sensory epithelium, including the au- ditory hair cells (2). Using a bicompartmental culture 1 Department of Human physiology and Pathophysiology 1 , University of Liege, 17 Place Delcour, B-4020 Liege, Belgium. 2 Departments of Otolaryngology and 3 Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461. 4 Department of Immunology, Amgen Inc., Thousand Oaks, CA 91320. 5 Address reprint requests to: B. Malgrange, Department of Human Physiology and Pathophysiology, University of Liege, 17 Place Del- cour, B-4020 Liege, Belgium. Tel: (32) 4 366 59 11; Fax: (32) 4 366 59 12; E-mail: bmalgrange@ulg.ac.be 1133 system, we have recently shown that the organ of Corti dissected from 3 day-old (P3) rats can be maintained in vitro for extended periods of time (i.e. several weeks) in Eagle's minimal essential medium (MEM) without any supplements (Malgrange et al., unpublished observa- tions). Hair cell integrity in these long term explants was demonstrated by both confocal laser microscopy of phal- loidin-FITC stained specimens and ultrastructural obser- vations (Malgrange et al., in preparation). Therefore, if growth factors are essential for the survival and differ- entiation of auditory hair cells, both the factor(s) and the corresponding receptor(s) are likely to be endogenous to the organ of Corti neuroepithelium. Theoretically, afferent neurons could serve as a source of growth factors that affect the auditory hair cells. However, factors of neuronal origin do not seem to be essential for postnatal hair cell survival and dif- ferentiation since: i/ when combined spiral ganglion- organ of Corti cultures were seeded in unsupplemented MEM, most of the neurons degenerated within four days, ii/ there was no difference in the survival rates of 0364-3190/98/0800-1133$15.00/0 © 1998 Plenum Publishing Corporation