Effect of canonical NF-κB signaling pathway on the differentiation of rat dental epithelial stem cells.

BACKGROUND: Nuclear factor-κB (NF-κB), an important transcription factor, participates in many physiological and pathological processes such as growth, differentiation, organogenesis, apoptosis, inflammation, and immune response, including tooth development. However, it is still unknown whether NF-κB participates in the regulation of dental epithelial stem cells (DESCs) in postnatal rat incisors. Here, we investigated the specific differentiation regulatory mechanisms of the canonical NF-κB signaling pathway in DESCs and provided the mechanism of cross-talk involved in DESC differentiation. METHODS: After adding the activator or inhibitor of the NF-κB signaling pathway, Western blot and quantitative real-time PCR were used to analyze the expressions of amelogenesis-related genes and proteins and canonical transforming growth factor-ß (TGF-ß) signaling. In addition, we used amelogenesis induction in vitro by adding the activator or inhibitor of the NF-κB signaling pathway to the amelogenesis-induction medium, respectively. Recombinant TGF-ß was used to activate the TGF-ß pathway, and SMAD7 siRNA was used to downregulate the expression of SMAD7 in DESCs. RESULTS: We found that the expression of amelogenesis-related genes and proteins as well as TGF-ß signaling were downregulated, while SMAD7 expression was increased in NF-κB-activated DESCs. In addition, NF-κB-inhibited DESCs exhibited opposite results compared with NF-κB-activated DESCs. Furthermore, the canonical NF-κB signaling pathway suppressed the canonical TGF-ß-SMAD signaling by inducing SMAD7 expression involved in the regulation of DESC differentiation. CONCLUSIONS: These results indicate that the canonical NF-κB signaling pathway participated in the regulation of DESC differentiation, which was through upregulating SMAD7 expression and further suppressing the canonical TGF-ß-SMAD signaling pathway.

Schwann cells secrete extracellular vesicles to promote and maintain the proliferation and multipotency of hDPCs.

OBJECTIVES: Schwann cells (SCs) are the principal glial cells in peripheral nerve system, involved in neuropathies with great regenerative potential. Dental pulp cells have been reported to maintain neurogenic potential. In contrast, the regulatory role of SCs on human dental pulp cells (hDPCs) development remains undefined. MATERIALS AND METHODS: SC secretion and SC-derived extracellular vesicles (EVs) were collected and used to treat hDPCs; and proliferation and multiple differentiation of hDPCs were detected after EVs treatments. Finally, we analysed the proteomes of SC-EVs and SCs through mass spectrum. RESULTS: In this study, we found SC secretion showed a predominantly regulatory role on the development of hDPCs. Further, we identified EVs from SC secretion with similar function as SC secretion in regulating hDPCs proliferation and multipotency. And expression of transcription factor Oct4 was upregulated after treatment of both SC secretion and EVs, as well as Sox2 and Nanog. We detected abundant enrichment of Oct4 in EVs, which might be responsible for the upregulation of stem cell-related genes in hDPCs. Through proteome and western blot analysis, we found enriched TGFßs in EVs, indicating that accelerated hDPCs proliferation may be mediated by activated TGFß-Samd and TGFß-MAPK signalling. CONCLUSIONS: In summary, our study sheds light on critical regulatory ability of SC-derived EVs on hDPCs proliferation and multipotency, suggesting great implications for seeding cells used in tissue engineering.