Research Articles, Development/Plasticity/Repair Sofia Håglin, Anna Berghard and Staffan Bohm Journal of Neuroscience 20 May 2020, 40 (21) 4116-4129; DOI: https://doi.org/10.1523/JNEUROSCI.2468-19.2020 Abstract The cellular and molecular basis of metaplasia and declining neurogenesis in the aging olfactory epithelium (OE) remains unknown. The horizontal basal cell (HBC) is a dormant tissue-specific stem cell presumed to only be forced into self-renewal and differentiation by injury.