Expression of growth factors in fetal human olfactory mucosa during development.

The olfactory epithelium is one of the unique sites in the mammalian nervous system at which there is continual neurogenesis. Constant turnover of primary sensory neurons in the periphery results in remodeling of neuronal circuits and synapses in the olfactory bulb throughout life. Most of the specific mechanisms and factors that control this process are still unknown. Recent studies suggest that growth factors and their receptors may play a significant role in the development and continuous regeneration of olfactory neurons. In this study, standard immunohistochemical methods were used to detect the presence of epidermal growth factor-receptor, transforming growth factor-alpha and nerve growth factor-beta in the human olfactory epithelium of different developmental stages (7 to 30 weeks) in formalin-fixed tissue specimens. Immunoreactivity to epidermal growth factor-receptor was seen in basal cells, supporting cells, neurons, apical cytoplasmic region of olfactory epithelium, lamina propria and gland's cell cytoplasm. Similarly transforming growth factor-alpha immunoreactivity was recognized in basal cells, supporting cells, apical cytoplasmic region of olfactory epithelium, lamina propria and gland's cell cytoplasm but not in neurons. Nerve growth factor-beta detection was restricted on olfactory nerve cells, dentritic knob and basal cell layer. So, this study confirms the development of human olfactory mucosa and shows epidermal growth factor-receptor, transforming growth factor-alpha and nerve growth factor-beta proteins are reliable markers for developing olfactory epithelium.