Cdc42 is essential for the polarized movement and adhesion of human dental pulp stem cells

A novel Cdc42-YAP-fibronectin signaling axis regulates ameloblast differentiation during early enamel formation

Enamel formation is a developmental event governed by intricate molecular signal pathways. Cdc42 is proven to regulate enamel development yet its underlying role and molecular mechanism in early amelogenesis remain elusive. The extracellular matrix of tooth germ basement membrane is critical for the regulation of ameloblast differentiation. Present study investigated whether Cdc42 influences amelogenesis by affecting ECM synthesis and how Cdc42 regulates ameloblasts differentiation. Epithelial-specific knockout of Cdc42 (Cdc42-cKO) mice model was employed to study the ECM expression including Fibronectin (Fn) and amelogenesis markers. Cdc42-cKO mice results in retarded ameloblast differentiation and enamel matrix decrease. Fn synthesis in the enamel organ and basal membrane was totally diminished along with Cdc42 knockdown. YAP acting as the Cdc42 downstream transcription factor, its distribution in ameloblasts was synchronously attenuated by Cdc42 knockdown and nuclear localization progressively decreased with tooth germ development. Cdc42 unidirectionally controls the Fn synthesis via YAP regulation. Overall, ameloblast differentiation inhibition by silencing of Cdc42 was successfully rescued by YAP activation. We demonstrated that Cdc42 as an initiator, mediated downstream pathway through transcriptional activator YAP, thereby affecting ameloblast differentiation by controlling Fn synthesis. The Cdc42-YAP-Fn signaling axis are elucidated to act critical role during the early amelogenesis.

Cannabidiol alleviates LPS-inhibited odonto/osteogenic differentiation in human dental pulp stem cells in vitro

AIM

Cannabidiol (CBD), derived from the Cannabis sativa plant, exhibits benefits in potentially alleviating a number of oral and dental pathoses, including pulpitis and periodontal diseases. This study aimed to explore the impact of CBD on several traits of human dental pulp stem cells (hDPSC), such as their proliferation, apoptosis, migration and odonto/osteogenic differentiation.

METHODOLOGY

hDPSCs were harvested from human dental pulp tissues. The cells were treated with CBD at concentrations of 1.25, 2.5, 5, 10, 25 and 50 μg/mL. Cell responses in terms of cell proliferation, colony-forming unit, cell cycle progression, cell migration, apoptosis and odonto/osteogenic differentiation of hDPSCs were assessed in the normal culture condition and P. gingivalis lipopolysaccharide (LPS)-induced 'inflammatory' milieus. RNA sequencing and proteomic analysis were performed to predict target pathways impacted by CBD.

RESULTS

CBD minimally affects hDPSCs' behaviour under normal culture growth milieu in normal conditions. However, an optimal concentration of 1.25 μg/mL CBD significantly countered the harmful effects of LPS, indicated by the promoting cell proliferation and restoring the odonto/osteogenic differentiation potential of hDPSCs under LPS-treated conditions. The proteomic analysis demonstrated that several proteins involved in cell proliferation and differentiation were upregulated following CBD exposure, including CCL8, CDC42 and KFL5. RNA sequencing data indicated that CBD upregulated the Notch signalling pathway. In an inhibitory experiment, DAPT, a Notch inhibitor, reduced the effect of CBD-rescued LPS-attenuated mineralization in hDPSCs, suggesting that CBD potentially mediates Notch activation to exert its impact on odonto/osteogenic differentiation of hDPSCs.

CONCLUSIONS

CBD recovers the proliferation and survival of hDPSCs following exposure to LPS. Additionally, we report that CBD-mediated Notch activation effectively restores the odonto/osteogenic differentiation ability of hDPSCs under inflamed conditions. These results underscore the potential role of CBD as a therapeutic option to enhance dentine regeneration.

Staphylococcal Enterotoxin C2 Mutant-Induced Antitumor Immune Response Is Controlled by CDC42/MLC2-Mediated Tumor Cell Stiffness

As a biological macromolecule, the superantigen staphylococcal enterotoxin C2 (SEC2) is one of the most potent known T-cell activators, and it induces massive cytotoxic granule production. With this property, SEC2 and its mutants are widely regarded as immunomodulating agents for cancer therapy. In a previous study, we constructed an MHC-II-independent mutant of SEC2, named ST-4, which exhibits enhanced immunocyte stimulation and antitumor activity. However, tumor cells have different degrees of sensitivity to SEC2/ST-4. The mechanisms of immune resistance to SEs in cancer cells have not been investigated. Herein, we show that ST-4 could activate more powerful human lymphocyte granule-based cytotoxicity than SEC2. The results of RNA-seq and atomic force microscopy (AFM) analysis showed that, compared with SKOV3 cells, the softer ES-2 cells could escape from SEC2/ST-4-induced cytotoxic T-cell-mediated apoptosis by regulating cell softness through the CDC42/MLC2 pathway. Conversely, after enhancing the stiffness of cancer cells by a nonmuscle myosin-II-specific inhibitor, SEC2/ST-4 exhibited a significant antitumor effect against ES-2 cells by promoting perforin-dependent apoptosis and the S-phase arrest. Taken together, these data suggest that cell stiffness could be a key factor of resistance to SEs in ovarian cancer, and our findings may provide new insight for SE-based tumor immunotherapy.

Trio cooperates with Myh9 to regulate neural crest-derived craniofacial development

Trio is a unique member of the Rho-GEF family that has three catalytic domains and is vital for various cellular processes in both physiological and developmental settings. TRIO mutations in humans are involved in craniofacial abnormalities, in which patients present with mandibular retrusion. However, little is known about the molecular mechanisms of Trio in neural crest cell (NCC)-derived craniofacial development, and there is still a lack of direct evidence to assign a functional role to Trio in NCC-induced craniofacial abnormalities. Methods: In vivo, we used zebrafish and NCC-specific knockout mouse models to investigate the phenotype and dynamics of NCC development in Trio morphants. In vitro, iTRAQ, GST pull-down assays, and proximity ligation assay (PLA) were used to explore the role of Trio and its potential downstream mediators in NCC migration and differentiation. Results: In zebrafish and mouse models, disruption of Trio elicited a migration deficit and impaired the differentiation of NCC derivatives, leading to craniofacial growth deficiency and mandibular retrusion. Moreover, Trio positively regulated Myh9 expression and directly interacted with Myh9 to coregulate downstream cellular signaling in NCCs. We further demonstrated that disruption of Trio or Myh9 inhibited Rac1 and Cdc42 activity, specifically affecting the nuclear export of β-catenin and NCC polarization. Remarkably, craniofacial abnormalities caused by trio deficiency in zebrafish could be partially rescued by the injection of mRNA encoding myh9, ca-Rac1, or ca-Cdc42. Conclusions: Here, we identified that Trio, interacting mostly with Myh9, acts as a key regulator of NCC migration and differentiation during craniofacial development. Our results indicate that trio morphant zebrafish and Wnt1-cre;Trio^fl/fl mice offer potential model systems to facilitate the study of the pathogenic mechanisms of Trio mutations causing craniofacial abnormalities.