Postembryonic production of inner ear hair cells occurs after insult in nonmammalian vertebrates. Recent studies suggest that the fibroblast family of growth factors may play a role in stimulating cell proliferation in mature inner ear sensory epithelium. Effects of acidic fibroblast growth factor (FGF-1) and basic fibroblast growth factor (FGF-2) were tested on progenitor cell division in cultured auditory and vestibular sensory epithelia taken from posthatch chickens. The effects of heparin, a glycosaminoglycan that often potentiates the effects of the FGFs, were also assessed. Tritiated-thymidine autoradiographic techniques and 5-bromo-2;-deoxyuridine (BrdU) immunocytochemistry were used to identify cells synthesizing DNA. The terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-biotin nick-end-label (TUNEL) method was used to identify apoptotic cells. TUNEL and overall counts of sensory epithelial cell density were used to assess possible cytotoxic effects of the growth factors. FGF-2 inhibited DNA synthesis in vestibular and auditory sensory epithelia and was not cytotoxic at the concentrations employed. FGF-1 did not significantly alter sensory epithelial cell proliferation. Heparin by itself inhibited DNA synthesis in the vestibular sensory epithelia and failed to potentiate the effects of FGF-1 or FGF-2. Heparin was not cytotoxic at the concentrations employed. Results presented here suggest that FGF-2 may be involved in inhibiting cell proliferation or stimulating precursor cell differentiation in avian inner ear sensory epithelia.
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http://dx.doi.org/10.1002/1096-9861(20000821)424:2<307::aid-cne9>3.0.co;2-m | DOI Listing |
J Otol
October 2024
Department of Otolaryngology-Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China.
The inner ear sensory epithelium consists of two major types of cells: hair cells (HCs) and supporting cells (SCs). Critical functions of HCs in the perception of mechanical stimulation and mechanosensory transduction have long been elucidated. SCs are indispensable components of the sensory epithelia, and they maintain the structural integrity and ionic environment of the inner ear.
View Article and Find Full Text PDFElife
January 2025
Department of Otorhinolaryngology - Head & Neck Surgery, University of Maryland School of Medicine, Baltimore, United States.
Calcium and integrin-binding protein 2 (CIB2) and CIB3 bind to transmembrane channel-like 1 (TMC1) and TMC2, the pore-forming subunits of the inner-ear mechano-electrical transduction (MET) apparatus. These interactions have been proposed to be functionally relevant across mechanosensory organs and vertebrate species. Here, we show that both CIB2 and CIB3 can form heteromeric complexes with TMC1 and TMC2 and are integral for MET function in mouse cochlea and vestibular end organs as well as in zebrafish inner ear and lateral line.
View Article and Find Full Text PDFDev Biol
January 2025
Biology Department, Texas A&M University, College Station, TX, 7843-3258, USA. Electronic address:
During development of the vertebrate inner ear, sensory epithelia and neurons of the statoacoustic ganglion (SAG) arise from lineage-restricted progenitors that proliferate extensively before differentiating into mature post-mitotic cell types. Development of progenitors is regulated by Fgf, Wnt and Notch signaling, but how these pathways are coordinated to achieve an optimal balance of proliferation and differentiation is not well understood. Here we investigate the role in zebrafish of Foxm1, a transcription factor commonly associated with proliferation in developing tissues and tumors.
View Article and Find Full Text PDFFront Allergy
October 2024
Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL, United States.
It is well understood that odorants interact with specialized G-protein coupled receptors embedded in the ciliary membrane of olfactory sensory neurons (OSN) which initiates a voltage-generating intracellular cascade of signal transduction events that can be recorded at the epithelial level as an electroolfactogram (EOG). While the depolarizing excitatory pathway in vertebrates involving cyclic adenosine monophosphate (cAMP)-induced Na/Ca influx and calcium-induced Cl efflux is well established, there is evidence of potassium-associated inhibitory currents that correspond with cellular activation. While several Ca-dependent feedback mechanisms contribute to cellular deactivation which have been commonly attributed to these inhibitory currents, the frequently observed positive ionic conductance prior to excitatory depolarization have led many to suggest an additional earlier inhibitory mechanism at the receptor level that may be independent of downstream calcium influx.
View Article and Find Full Text PDFNeuropeptides
December 2024
King's College London, Wolfson Sensory, Pain and Regeneration Centre, Hodgkin Building, Guy's Campus, London SE1 1UL, UK. Electronic address:
Long chain fatty acids are sensed by enteroendocrine L cells that express free-fatty acid receptors, including FFA1, FFA4 and the acylethanolamine receptor GPR119. Here we investigated the acute effects of single or multiple agonism at these G protein-coupled receptors in intestinal mucosae where L cell-derived peptide YY (PYY) is anti-secretory and acts via epithelial Y receptors. Mouse ileal or colonic mucosae were mounted in Ussing chambers, voltage-clamped and the resultant short-circuit current (I) recorded continuously.
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