Differential Expression of Cell-Specific Molecules in Olfactory Receptor Neurons of Humans of Different Ages

Abstract

Human olfactory receptor neurons (ORNs) express the neuron-specific molecules neuron-specific enolase (NSE; [1]) and protein gene product (PGP) 9.5 [2], as well as the olfactory-specific molecule olfactory marker protein (OMP [3–5]). To determine the relative frequency of expression of these markers throughout the human life span, to investigate the relationship between the expression of these markers and ongoing cell death, and to initiate studies on immune involvement in ORN death, double-staining immunofluorescence techniques with antibodies to NSE or PGP 9.5 and OMP were applied to tissue obtained at autopsy from 16 subjects (10 males, 6 females). Subjects included a 16-week-old fetus, a 24-week-old fetus, a 10-week-old infant, 4 young and middle-aged subjects (24–59 years old; mean, 45 years), 5 old subjects (63–90 years old; mean, 75 years old), and 4 subjects (52–85 years old; mean, 70 years old) in whom the diagnosis of Alzheimer’s disease (AD) was confirmed by brain histopathology. Post-mortem intervals (range, 2–22 h; median, 8 h) did not differ significantly. The numbers of OMP-immunoreactive and NSE- or PGP 9.5-immunoreactive ORNs in each microscopic field that contained at least one OMP-immunoreactive ORN were counted; the densities of neurons expressing each marker and the ratios of OMP: NSE or PGP 9.5-immunoreactive neurons were calculated. Statistical analyses were performed with Kruskal-Wallis and Dunn’s multiple comparison tests.