Activating a Reserve Neural Stem Cell Population In Vitro Enables Engraftment and Multipotency after Transplantation

Abstract

Summary: The olfactory epithelium (OE) regenerates after injury via two types of tissue stem cells: active globose cells (GBCs) and dormant horizontal basal cells (HBCs). HBCs are roused to activated status by OE injury when P63 levels fall. However, an in-depth understanding of activation requires a system for culturing them that maintains both their self-renewal and multipotency while preventing spontaneous differentiation. Here, we demonstrate that mouse, rat, and human HBCs can be cultured and passaged as P63+ multipotent cells. HBCs in vitro closely resemble HBCs in vivo based on immunocytochemical and transcriptomic comparisons. Genetic lineage analysis demonstrates that HBCs in culture arise from both tissue-derived HBCs and multipotent GBCs. Treatment with retinoic acid induces neuronal and non-neuronal differentiation and primes cultured HBCs for transplantation into the lesioned OE. Engrafted HBCs generate all OE cell types, including olfactory sensory neurons, confirming that HBC multipotency and neurocompetency are maintained in culture. : In this article, Peterson and colleagues show that the reserve stem cells of the mammalian olfactory epithelium, the horizontal basal cells (HBCs), are maintained and expanded in vitro and closely resemble HBCs in vivo. Many HBCs are generated from transdifferentiation of globose basal cells during culturing. Retinoic acid induces differentiation and permits their engraftment back into the olfactory epithelium. Keywords: olfactory epithelium, adult stem cell, horizontal basal cell, retinoic acid, transplantation