Foto del docente

Valeria Franceschini

Full Professor

Department of Biological, Geological, and Environmental Sciences

Academic discipline: BIO/06 Comparative Anatomy and Cytology


Keywords: Acoustic system regeneration immunohistochemistry Olfactory system toxic compounds

1-Studies on the ability of human cord blood-selected CD133+ stem cells (HSC) to repair the sensory epithelium damaged by toxic agents and on the culture conditions that direct multipotent monkey rhesus ESC differentiation along different lineages. 2- Studies on the molecular characterization of glycoconjuguates in the membrane of olfactory neurons from Vertebrates using the binding of lectins. 3- Studies on the amphibiams and reptiles brain angioarchitecture and cytochemical analysis of the capillars encephalique in the development of the brain blood barrier. 4- Studies on the distribution of GFAP and vimentin in the glial cells of Dipnoan and reptiles brain.

Valeria Franceschini has studied the ability of human cord blood-selected CD133+ stem cells (HSC) to repair the sensory epithelium damaged by toxic agents.
She investigated whether human umbilical cord blood CD133+ stem cells (HSC) injected intravenously to nod-scid mice pre-treated with dichlobenil, an herbicide that selectively causes permanent damage of the dorso-medial part of the olfactory neuroepithelium (NE), may engraft the olfactory mucosa and contribute to the regeneration of the damaged NE. She looked for the presence of HLA-DQα1 DNA and three human microsatellites (CODIS) as indicators of engrafted cells, finding PCR evidence of chimaerism in various tissues of the host, including the olfactory mucosa and bulb, at 7 and 31 days following HSC transplantation. Detailed histology, immunohistochemistry and lectin staining revealed the morphological recovery of the dorso-medial region of the NE in dichlobenil-treated mice that received HSC in contrast with the lack of regeneration in similarly injured areas as these remained damaged in control non-transplanted mice. Multi-colour FISH analysis, to detect five human genomic sequences from different chromosomes, confirmed persistent engraftment of the regenerating olfactory area with chimaeric cells. These findings support the concept that transplanted HSC migrating to the damaged olfactory area provide conditions facilitating the recovery from olfactory receptor cell loss.
She also investigated the fate of HSC transplanted intravenously into irradiated nod-scid mice previously made deaf by ototoxic treatment with kanamycin and/or intense noise. PCR analysis, used for traceability of engrafted cells, revealed that HSC migrated to various host tissues, including the organ of Corti (OC). By histology, antibody and lectin-staining analysis, she confirmed that HSC i.v. transplantation in mice previously damaged by ototoxic agents, correlated with the repair process and stimulation  ex novo of morphological recovery in the inner ear, while the cochlea of control oto-injured, non- transplanted mice, remained seriously damaged. Dual color-FISH-analysis provided also evidence of positive engraftment in the inner ear and in various mouse tissues, also revealing small numbers of heterokaryons, probably derived from fusion of donor with endogenous cells, for up to two months following transplantation. These observations offer the first evidence that transplanted human HSC migrating to the inner ear of oto-injured mice may provide conditions for the resumption of deafened cochlea, emerging as a potential strategy for inner ear rehabilitation.
Moreover she studied the culture conditions that direct multipotent monkey rhesus ESC differentiation along different lineages. In 2D culture systems, ESC different condition was induced and cells formed a mixed population with elements of 3 embryonic germ lines. On the contrary in 3D cultural system, in normal embryos or in teratomas in nude mice ESC migration and interaction with their microenvironment are required for multicellular structures formation. Therefore, ESCs were co-cultured in collagen matrixes with irradiated human dermal fibroblasts or keratinocytes as feeder cells. Cell-cell multiple interactions and soluble factors led to ESC differentiation forming complex tubular or spherical gland-like structures and endogenous extra-cellular matrix (ECM) production. ESC ultimately generated differentiated progenies showing characteristics mainly of epithelial or neural lineages. In the presence of feeder cells and exogenous cytokines, differentiation could be selectively directed into a particular lineage. The deposition of endogenous ECMs preceded detectable expression of the lineage specific markers of ESC differentiation. The effects on ESC self-renewal or differentiation depended on subtle shifts in the type and concentration of endogenous regulatory proteins in the microenvironment, indicating that the amount of differentiated cells and their lineage may be determined by culture systems.
Moreover Valeria Franceschini has studied the distribution and density of the glycoconjugates on the cellular membrane of the olfactory receptor cells in many vertebrates. In contrast to most neurons, the olfactory neurons are directly exposed to a large number of environmental factors and are continuously replaced throughout the lifetime of the animal. New neurons originate from globose basal cells, migrate to the upper third of the epithelium during differentiation, and re-establish contacts with the lumen of the nasal cavity through terminal knobs and via synaptic connections to the glomerular layer in the bulbs. Glycoconjugates located on olfactory receptors cell membrane pay a crucial role in these mechanisms of cell-cell recognition and fasciculation. The lectin binding was used as a molecular probe to identify the carbohydrate moieties of the olfactory neurons. Lectins are proteins or glycoproteins that bind specifically to different terminal sugars or sugar sequences in complex carbohydrates, therefore are able to discriminate neurons on the basis of their cellular membrane glycoproteins composition. The research was performed on numerous species representative of vertebrates, from cyclostomes to mammals except avians. The studies pointed out that the vertebrate olfactory system is quite conservative for both the structural organization and the carbohydrate moieties of the olfactory receptor membranes.
Given that low levels of copper are known to specifically cause neuron death in fish olfactory epithelium, she also investigated the morphological changes in the olfactory mucosa of the cichlid Tilapia mariae, after a 4-day exposure to different doses of Cu2+ (20, 40 and 100 microg/l), and the regeneration time-frame, when fishes exposed to 20 microg/l were returned to dechlorinated tap water. Light microscopy, combined with Fluoro-Jade B staining, allowed the observation of a dose-dependent damage, which became less severe and more circumscribed to receptor cells when Cu2+ concentration decreased. The regeneration process in the olfactory tissue was examined in fishes after 0, 3, and 10 days of recovering in well water. Immunostaining with PCNA showed a massive mitotic activity in the basal region of the mucosa immediately after exposure was terminated. These new elements were immature neurons since they expressed the neural growth-associated phosphoprotein GAP-43. After 3 days of recovery the nuclei had already completed their migration to the upper portion of the epithelium and mitotic activity was much less intensive. After 10 days the olfactory tissue did not present differences respect to the control one. These results suggest that after 10 days the regeneration seems to be completed and the integrity of the tissue restored.
Valeria Franceschini has also studied the distribution of glial fibrillary acidic protein (GFAP) and vimentin as molecular markers in the glial intermediate filament in the brain and spinal cord of some vertebrate (African lungfish, lizards, turtle, and amphibian urodels). In Protopterus and urodels she demonstrated the presence of only one type of astroglial lineage throughout the brain: ependymal radial glia or tanycytes. Radial glia consists of cellular elements with a complex shape. Their pear- or spindle-shaped cell bodies are located in the ependymal or periependymal layer constituting the ependymal or periependymal radial glia, respectively. They give rise to long radial cytoplasmic processes that spread over the central nervous system (CNS) to terminate with endfeet apposed to the vascular and pial surface where they form the perivascular and submeningeal glial layers. These cells are GFAP-positive and vimentin-negative both in Protopterus and in Ambystoma. The contrary holds for Triturus. In reptiles, CNS immunoperoxidase cytochemistry demonstrated the presence besides the radial glia, also of star-shaped astrocytes located in the optic tectum and spinal cord. Moreover the staining intensity is different in the same cell type. Notwithstanding this condition appears morphologically more primitive than that found in avians and mammals. This condition supports that reptiles represent a fundamental step in the phylogenetic evolution of vertebrate astroglial cells.