Neurite outgrowth inhibitor A(Nogo-A)is a major player in neural development and regeneration and the target of clinical trials aiming at promoting the regeneration of the central nervous system upon traumatic and ischemic injury.In this work,we investigated the functions of Nogo-A during tooth development to determine its role in dental physiology and pathology.Using immunohistochemistry and in situ hybridization techniques,we showed that Nogo-A is highly expressed in the developing mouse teeth and,most specifically,in the ameloblasts that are responsible for the formation of enamel.Using both Nogo-A knockout and K14-Cre;Nogo-A fl/fltransgenic mice,we showed that Nogo-A deletion in the dental epithelium leads to the formation of defective enamel.This phenotype is associated with overexpression of a set of specific genes involved in ameloblast differentiation and enamel matrix production,such as amelogenin,ameloblastin and enamelin.By characterising the interactome of Nogo-A in the dental epithelium of wild-type and mutant animals,we found that Nogo-A directly interacts with molecules important for regulating gene expression,and its deletion disturbs their cellular localisation.Furthermore,we demonstrated that inhibition of the intracellular,but not cell-surface,Nogo-A is responsible for gene expression modulation in ameloblasts.Taken together,these results reveal an unexpected function for Nogo-A in tooth enamel formation by regulating gene expression and cytodifferentiation events.

Neurite outgrowth inhibitor A(Nogo-A)is a major player in neural development and regeneration and the target of clinical trials aiming at promoting the regeneration of the central nervous system upon traumatic and ischemic injury.In this work,we investigated the functions of Nogo-A during tooth development to determine its role in dental physiology and pathology.Using immunohistochemistry and in situ hybridization techniques,we showed that Nogo-A is highly expressed in the developing mouse teeth and,most specifically,in the ameloblasts that are responsible for the formation of enamel.Using both Nogo-A knockout and K14-Cre;Nogo-A fl/fltransgenic mice,we showed that Nogo-A deletion in the dental epithelium leads to the formation of defective enamel.This phenotype is associated with overexpression of a set of specific genes involved in ameloblast differentiation and enamel matrix production,such as amelogenin,ameloblastin and enamelin.By characterising the interactome of Nogo-A in the dental epithelium of wild-type and mutant animals,we found that Nogo-A directly interacts with molecules important for regulating gene expression,and its deletion disturbs their cellular localisation.Furthermore,we demonstrated that inhibition of the intracellular,but not cell-surface,Nogo-A is responsible for gene expression modulation in ameloblasts.Taken together,these results reveal an unexpected function for Nogo-A in tooth enamel formation by regulating gene expression and cytodifferentiation events.

Carious lesions are bacteria-caused destructions of the mineralised dental tissues, marked by the simultaneous activation of immune responses and regenerative events within the soft dental pulp tissue. While major molecular players in tooth decay have been uncovered during the past years, a detailed map of the molecular and cellular landscape of the diseased pulp is still missing. In this study we used single-cell RNA sequencing analysis, supplemented with immunostaining, to generate a comprehensive single-cell atlas of the pulp of carious human teeth. Our data demonstrated modifications in the various cell clusters within the pulp of carious teeth, such as immune cells, mesenchymal stem cells (MSC) and fibroblasts, when compared to the pulp of healthy human teeth. Active immune response in the carious pulp tissue is accompanied by specific changes in the fibroblast and MSC clusters. These changes include the upregulation of genes encoding extracellular matrix (ECM) components, including COL1A1 and Fibronectin (FN1), and the enrichment of the fibroblast cluster with myofibroblasts. The incremental changes in the ECM composition of carious pulp tissues were further confirmed by immunostaining analyses. Assessment of the Fibronectin fibres under mechanical strain conditions showed a significant tension reduction in carious pulp tissues, compared to the healthy ones. The present data demonstrate molecular, cellular and biomechanical alterations in the pulp of human carious teeth, indicative of extensive ECM remodelling, reminiscent of fibrosis observed in other organs. This comprehensive atlas of carious human teeth can facilitate future studies of dental pathologies and enable comparative analyses across diseased organs.
Humans ; Dental Pulp ; Fibronectins ; Extracellular Matrix/pathology* ; Dental Caries ; Sequence Analysis, RNA