Early human fetal lung atlas reveals the temporal dynamics of epithelial cell plasticity.

Studying human fetal lungs can inform how developmental defects and disease states alter the function of the lungs. Here, we sequenced >150,000 single cells from 19 healthy human pseudoglandular fetal lung tissues ranging between gestational weeks 10-19. We capture dynamic developmental trajectories from progenitor cells that express abundant levels of the cystic fibrosis conductance transmembrane regulator (CFTR). These cells give rise to multiple specialized epithelial cell types. Combined with spatial transcriptomics, we show temporal regulation of key signalling pathways that may drive the temporal and spatial emergence of specialized epithelial cells including ciliated and pulmonary neuroendocrine cells. Finally, we show that human pluripotent stem cell-derived fetal lung models contain CFTR-expressing progenitor cells that capture similar lineage developmental trajectories as identified in the native tissue. Overall, this study provides a comprehensive single-cell atlas of the developing human lung, outlining the temporal and spatial complexities of cell lineage development and benchmarks fetal lung cultures from human pluripotent stem cell differentiations to similar developmental window.

PRX1-positive mesenchymal stem cells drive molar morphogenesis.

Mammalian teeth, developing inseparable from epithelial-mesenchymal interaction, come in many shapes and the key factors governing tooth morphology deserve to be answered. By merging single-cell RNA sequencing analysis with lineage tracing models, we have unearthed a captivating correlation between the contrasting morphology of mouse molars and the specific presence of PRX1+ cells within M1. These PRX1+ cells assume a profound responsibility in shaping tooth morphology through a remarkable divergence in dental mesenchymal cell proliferation. Deeper into the mechanisms, we have discovered that Wnt5a, bestowed by mesenchymal PRX1+ cells, stimulates mesenchymal cell proliferation while orchestrating molar morphogenesis through WNT signaling pathway. The loss of Wnt5a exhibits a defect phenotype similar to that of siPrx1. Exogenous addition of WNT5A can successfully reverse the inhibited cell proliferation and consequent deviant appearance exhibited in Prx1-deficient tooth germs. These findings bestow compelling evidence of PRX1-positive mesenchymal cells to be potential target in regulating tooth morphology.

Piezo Mediates the Mechanosensation and Injury-Repair of Pulpo-Dentinal Complex.

OBJECTIVES: The aim of this research was to investigate the functions of Piezo channels in dentin defect, including mechanical signalling and odontoblast responses. METHODS: Rat dentin-defect models were constructed, and spatiotemporal expression of Piezo proteins was detected in the pulpo-dentinal complex. Real-time polymerase chain reaction (rtPCR) was used to investigate the functional expression pattern of Piezo channels in odontoblasts. Moreover, RNA interference technology was employed to uncover the underlying mechanisms of the Piezo-driven inflammatory response and repair under fluid shear stress (FSS) conditions in vitro. RESULTS: Piezo1 and Piezo2 were found to be widely expressed in the odontoblast layer and dental pulp in the rat dentin-defect model during the end stage of reparative dentin formation. The expression levels of the Piezo1 and Piezo2 genes in MDPC-23 cells were high in the initial stage under FSS loading and then decreased over time. Moreover, the expression trends of inflammatory, odontogenic, and mineralisation genes were generally contrary to those of Piezo1 and Piezo2 over time. After silencing of Piezo1/Piezo2, FSS stimulation resulted in significantly higher expression of inflammatory, odontogenesis, and mineralisation genes in MDPC-23 cells. Finally, the expression of genes involved in the integrin ß1/ERK1 and Wnt5b/ß-catenin signalling pathways was changed in response to RNA silencing of Piezo1 and Piezo2. CONCLUSIONS: Piezo1 and Piezo2 may be involved in regulating the expression of inflammatory and odontogenic genes in odontoblasts stimulated by FSS.

Primary cilia support cartilage regeneration after injury.

In growing children, growth plate cartilage has limited self-repair ability upon fracture injury always leading to limb growth arrest. Interestingly, one type of fracture injuries within the growth plate achieve amazing self-healing, however, the mechanism is unclear. Using this type of fracture mouse model, we discovered the activation of Hedgehog (Hh) signaling in the injured growth plate, which could activate chondrocytes in growth plate and promote cartilage repair. Primary cilia are the central transduction mediator of Hh signaling. Notably, ciliary Hh-Smo-Gli signaling pathways were enriched in the growth plate during development. Moreover, chondrocytes in resting and proliferating zone were dynamically ciliated during growth plate repair. Furthermore, conditional deletion of the ciliary core gene Ift140 in cartilage disrupted cilia-mediated Hh signaling in growth plate. More importantly, activating ciliary Hh signaling by Smoothened agonist (SAG) significantly accelerated growth plate repair after injury. In sum, primary cilia mediate Hh signaling induced the activation of stem/progenitor chondrocytes and growth plate repair after fracture injury.

Tooth number abnormality: from bench to bedside.

Tooth number abnormality is one of the most common dental developmental diseases, which includes both tooth agenesis and supernumerary teeth. Tooth development is regulated by numerous developmental signals, such as the well-known Wnt, BMP, FGF, Shh and Eda pathways, which mediate the ongoing complex interactions between epithelium and mesenchyme. Abnormal expression of these crutial signalling during this process may eventually lead to the development of anomalies in tooth number; however, the underlying mechanisms remain elusive. In this review, we summarized the major process of tooth development, the latest progress of mechanism studies and newly reported clinical investigations of tooth number abnormality. In addition, potential treatment approaches for tooth number abnormality based on developmental biology are also discussed. This review not only provides a reference for the diagnosis and treatment of tooth number abnormality in clinical practice but also facilitates the translation of basic research to the clinical application.

A novel strategy combining Mini-CEX and OSCE to assess standardized training of professional postgraduates in department of prosthodontics.

OBJECTIVE: Mini clinical evaluation exercise (mini-CEX) and objective structured clinical examination (OSCE) are widely acknowledged as effective measures of resident standardization training (RST) in European and American countries. However, in China primary mini-CEX and OSCE forms are mainly limited in undergraduate clinical examination. Little knowledge is available regarding the validity and right way of mini-CEX /OSCE evaluation system in advanced dental clinical education so far. This study aimed to explore whether combination of mini-CEX and OSCE represents a global-dimension assessment for postgraduate clinical competence in RST. METHODS: Postgraduates who received RST from June 2017 to June 2019 were selected and evaluated by modified mini-CEX/OSCE scales. Each student received evaluations at least twice in the initial and final stages of training (tested every 4 months). A questionnaire was conducted to investigate the satisfaction with the arrangement of RST. RESULTS: Mini-CEX/OSCE test results indicated that postgraduates have significantly improved their comprehensive competence in RST projects in the department of prosthodontics (P < 0.05). Compared to other master of Stomatology students, postgraduates taking up prosthodontics master's degree have made more progresses through a training period of up to 1 year and four sessions of face-to-face feedback tutoring (P < 0.05). Survey results revealed high level of satisfaction on clinical practice evaluation. CONCLUSION: Modified mini-CEX/OSCE combined evaluation system is an effective and reliable assessment tool for clinical comprehensive ability in the RST of professional graduates and can fully highlight their respective advantages on the improvement of students' clinical competency, especially after several rounds of assessments.

Tracing PRX1+ cells during molar formation and periodontal ligament reconstruction.

Neural crest-derived mesenchymal stem cells (MSCs) are known to play an essential function during tooth and skeletal development. PRX1+ cells constitute an important MSC subtype that is implicated in osteogenesis. However, their potential function in tooth development and regeneration remains elusive. In the present study, we first assessed the cell fate of PRX1+ cells during molar development and periodontal ligament (PDL) formation in mice. Furthermore, single-cell RNA sequencing analysis was performed to study the distribution of PRX1+ cells in PDL cells. The behavior of PRX1+ cells during PDL reconstruction was investigated using an allogeneic transplanted tooth model. Although PRX1+ cells are spatial specific and can differentiate into almost all types of mesenchymal cells in first molars, their distribution in third molars is highly limited. The PDL formation is associated with a high number of PRX1+ cells; during transplanted teeth PDL reconstruction, PRX1+ cells from the recipient alveolar bone participate in angiogenesis as pericytes. Overall, PRX1+ cells are a key subtype of dental MSCs involved in the formation of mouse molar and PDL and participate in angiogenesis as pericytes during PDL reconstruction after tooth transplantation.

A genome-wide multiphenotypic association analysis identified candidate genes and gene ontology shared by four common risky behaviors.

BACKGROUND: Risky behaviors can lead to huge economic and health losses. However, limited efforts are paid to explore the genetic mechanisms of risky behaviors. RESULT: MASH analysis identified a group of target genes for risky behaviors, such as APBB2, MAPT and DCC. For GO enrichment analysis, FUMA detected multiple risky behaviors related GO terms and brain related diseases, such as regulation of neuron differentiation (adjusted P value = 2.84×10-5), autism spectrum disorder (adjusted P value =1.81×10-27) and intelligence (adjusted P value =5.89×10-15). CONCLUSION: We reported multiple candidate genes and GO terms shared by the four risky behaviors, providing novel clues for understanding the genetic mechanism of risky behaviors. METHODS: Multivariate Adaptive Shrinkage (MASH) analysis was first applied to the GWAS data of four specific risky behaviors (automobile speeding, drinks per week, ever-smoker, number of sexual partners) to detect the common genetic variants shared by the four risky behaviors. Utilizing genomic functional annotation data of SNPs, the SNPs detected by MASH were then mapped to target genes. Finally, gene set enrichment analysis of the identified candidate genes were conducted by the FUMA platform to obtain risky behaviors related gene ontology (GO) terms as well as diseases and traits, respectively.