IMMUNOHISTOCHEMICAL STUDIES OF SENSORY NEURONS IN RAT OLFACTORY EPITHELIUM

The olfactory sensory neurons undergo continuous turnover under normal physiological conditions. Injured olfactory sensory neurons are also replaceable. In this study, we investigated cellular differentiation and growth of sensory neurons in the rat's olfactory epithelium after nerve transection by using immunohistochemical staining with polyclonal or monoclonal anti-olfactory marker protein (OMP), anti-c-jun protein and anti-p53 protein antibodies. OMP is found exclusively in olfactory sensory neurons, while c-jun functions as a transcription factor. p53 protein functions as a negative regulator of cellular proliferation related to the apoptotic pathway induced by DNA damage. The olfactory epithelium sections incubated with anti-OMP antibody showed staining of mature neurons and axons in the epithelium. Nerve transection resulted in a significant reduction in neurons labelled with OMP. On the 9th day after operation, our study indicated some recovery with an increasing number of neurons expressing OMP. In control animals without nerve lesions, c-jun protein immunoreactive neurons were present in the olfactory epithelium adjacent to the basal region. Following days 1 and 3 after nerve transection, no expression of c-jun protein was seen in neurons of the epithelium. On day 9 after transection, neurons in some basal areas indicated expression of c-jun protein. The immunolocalization demonstrated that p53 protein was present in some neurons located on the upper part of the olfactory epithelium. In contrast, an abundance of neurons expressing p53 protein was evident in the olfactory epithelium 1 and 3 days after nerve transection, indicating more cell deaths. Nine days following the lesions, the epithelium showed the number of neurons expressing p53 protein declining to that of control animals. The present findings suggest that OMP, c-jun protein and p53 protein can serve as useful markers for identifying subclasses of olfactory neurons and determining the existence of a neurological disorder in olfactory epithelium.