Stem Cell Transplantation Supports the Repair of Injured Olfactory Neuroepithelium After Permanent Lesion Valeria Franceschini, Simone Bettini, Riccardo Saccardi, and Roberto P. Revoltella Abstract We investigated whether human cord blood-selected CD133 + stem cells (HSC) may engraft the olfactory mucosa and contribute to restoration of neuro-olfactory epithelium (NE) in nod-scid mice damaged by dichlobenil. The herbicide dichlobenil selectively causes necrosis of the dorsomedial part of the NE and underlying mucosa, while the lateral part of the olfactory region remains undamaged. The aim of this research was to demonstrate that HSC stimulate self-renewal of neuronal stem cells and promote their differentiation into bipolar olfactory neurons to replace the injured NE. By PCR, we tested the presence of three human-specific microsatellites (CODIS; Combined DNS Index System), used as DNA markers for traceability of the engrafted cells, demonstrating their pres- ence in various tissues of the host, including the olfactory mucosa, 1 month after transplantation. By immunohistochemistry and lectin staining, we demonstrated that, in injured mice, HSC contributed to stimulating residual endogenous olfac- tory neurons, promoting recovery of the original phenotype of the NE, in contrast to the lack of spontaneous regeneration in similar injured areas always seen in the nontransplanted control mice. Multiple colour fluorescence in situ hybridisation (M-FISH) analysis detected seven human genomic sequences present in different chromosomes and provided further evidence of positive prolonged engraftment of chimeric cells in the olfactory mucosa. This study provides the first evidence that transplanted HSC migrating to the neuro-olfactory mucosa may contribute to NE structure restoration with resumption of the sensorineural olfactory loss. Keywords Olfaction • Neuro-olfactory epithelium • Stem cell • Transplantation • Tissue regeneration V. Franceschini, S. Bettini, R. Saccardi, and R.P. Revoltella () Foundation “Stem Cells & Life” onlus; IPCF-CNR, Molecular Modelling Lab., Via G. Moruzzi 1, 56124, Pisa, Italy. e-mail: roberto.revoltella@itb.cnr.it e-mail: rrevoltella@yahoo.it H. Baharvand (ed.), Trends in Stem Cell Biology and Technology, 283 DOI 10.1007/ 978-1-60327-905-5_16, © Humana Press, a Part of Springer Science + Business Media, LLC 2009