Reversely immortalized mouse salivary gland cells presented a promising metabolic and fibrotic response upon BMP9/Gdf2 stimulation.

The submandibular gland (SMG) and the sublingual gland (SLG) are two of the three major salivary glands in mammals. In mice, they are adjacent to each other and open into the oral cavity, producing saliva to lubricate the mouth and aid in food digestion. Though salivary gland dysfunction accompanied with fibrosis and metabolic disturbance is common in clinic, in-depth mechanistic research is lacking. Currently, research on how to rescue salivary function is challenging, as it must resort to using terminally differentiated acinar cells or precursor acinar cells with unknown differentiation. In this study, we established reversely immortalized mouse primary SMG cells (iSMGCs) and SLG cells (iSLGCs) on the first postnatal day (P0). The iSMGCs and iSLGCs grew well, exhibited many salivary gland characteristics, and retained the metabolism-related genes derived from the original tissue as demonstrated using transcriptome sequencing (RNA-seq) analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of these two cell lines, which overlapped with those of the SMG and SLG, were enriched in cysteine and methionine metabolism. Furthermore, we investigated the role of bone morphogenetic protein 9 (BMP9), also known as growth differentiation factor 2(Gdf2), on metabolic and fibrotic functions in the SMG and SLG. We demonstrated that iSMGCs and iSLGCs presented promising adipogenic and fibrotic responses upon BMP9/Gdf2 stimulation. Thus, our findings indicate that iSMGCs and iSLGCs faithfully reproduce characteristics of SMG and SLG cells and present a promising prospect for use in future study of salivary gland metabolism and fibrosis upon BMP9/Gdf2 stimulation.

STAC: Spatial-Temporal Attention on Compensation Information for Activity Recognition in FPV.

Egocentric activity recognition in first-person video (FPV) requires fine-grained matching of the camera wearer's action and the objects being operated. The traditional method used for third-person action recognition does not suffice because of (1) the background ego-noise introduced by the unstructured movement of the wearable devices caused by body movement; (2) the small-sized and fine-grained objects with single scale in FPV. Size compensation is performed to augment the data. It generates a multi-scale set of regions, including multi-size objects, leading to superior performance. We compensate for the optical flow to eliminate the camera noise in motion. We developed a novel two-stream convolutional neural network-recurrent attention neural network (CNN-RAN) architecture: spatial temporal attention on compensation information (STAC), able to generate generic descriptors under weak supervision and focus on the locations of activated objects and the capture of effective motion. We encode the RGB features using a spatial location-aware attention mechanism to guide the representation of visual features. Similar location-aware channel attention is applied to the temporal stream in the form of stacked optical flow to implicitly select the relevant frames and pay attention to where the action occurs. The two streams are complementary since one is object-centric and the other focuses on the motion. We conducted extensive ablation analysis to validate the complementarity and effectiveness of our STAC model qualitatively and quantitatively. It achieved state-of-the-art performance on two egocentric datasets.

Hierarchical Optimization of 3D Point Cloud Registration.

Rigid registration of 3D point clouds is the key technology in robotics and computer vision. Most commonly, the iterative closest point (ICP) and its variants are employed for this task. These methods assume that the closest point is the corresponding point and lead to sensitivity to the outlier and initial pose, while they have poor computational efficiency due to the closest point computation. Most implementations of the ICP algorithm attempt to deal with this issue by modifying correspondence or adding coarse registration. However, this leads to sacrificing the accuracy rate or adding the algorithm complexity. This paper proposes a hierarchical optimization approach that includes improved voxel filter and Multi-Scale Voxelized Generalized-ICP (MVGICP) for 3D point cloud registration. By combining traditional voxel sampling with point density, the outlier filtering and downsample are successfully realized. Through multi-scale iteration and avoiding closest point computation, MVGICP solves the local minimum problem and optimizes the operation efficiency. The experimental results demonstrate that the proposed algorithm is superior to the current algorithms in terms of outlier filtering and registration performance.

Single-Cell RNA-Seq Analysis Identifies Angiotensinogen and Galanin as Unique Molecular Markers of Acinar Cells in Murine Salivary Glands.

The submandibular gland (SMG) and sublingual gland (SLG) are two of three major salivary glands in mammals and comprise serous and mucous acinar cells. The two glands share some functional properties, which are largely dependent on the types of acinar cells. In recent years, while ScRNA-seq (single-cell sequencing) with a 10 × platform has been used to explore molecular markers in salivary glands, few studies have examined the acinar heterogeneity and unique molecular markers between SMG and SLG. This study aimed to identify the molecular markers of acinar cells in the SLG and SMG. We performed ScRNA-seq analyses in 4-week-old mice and verified the screened molecular markers using reverse transcription-quantitative real-time PCR, immunohistochemistry, and immunofluorescence. Our results showed prominently heterogeneous acinar cells, although there was great similarity in the cluster composition between the two glands at 4 weeks. Furthermore, we demonstrated that Agt is a specific marker of SMG serous acinar cells, whereas Gal is a specific marker of SLG mucous acinar cells. Trajectory inference revealed that Agt and Gal represent two types of differential acinar cell clusters during late development in adults. Thus, we reveal previously unknown specific markers for salivary acinar cell diversity, which has extensive implications for their further functional research.

Validation of superior reference genes in mouse submandibular glands under developmental and functional regeneration states.

Saliva is crucial for lubricating the mouth and aiding in food digestion. However, the occurrence of oral dysfunction, such as xerostomia, dysphagia or oral infection can markedly reduce the quality of life of affected individuals. The major salivary glands include the submandibular gland (SMG), and sublingual and parotid glands; they are the larger glands in mammals that produce the majority of the saliva. The SMG serves as an effective model for the study of branching morphogenesis and functional regeneration. In order to better understand the key dynamic gene expression patterns during salivary gland development and functional regeneration, it is crucial to search for a panel of reliable reference genes. The present study thus aimed to identify superior reference genes to normalize gene expression data in the SMG under states of development and functional regeneration. First, the developmental SMG samples were harvested from mice in the embryonic and post­natal periods. Functional regeneration samples from a ductal ligation/de­ligation model were obtained at several stages. A total of 12 reference genes (Actb, Actg1, Ubc, Uba1, Uba52, Ube2c, Tuba1a, Tuba1b, Tubb5, H2afy, H2afx and Gapdh) from 430 candidates involving tubulin, histone, actin, ubiquitin and GAPDH family members were screened via transcriptome sequencing (RNA­seq) analysis. RT­qPCR (SYBR­Green) and western blot analysis were then used to semi­quantitatively assess gene and protein expression. The stability of expression was evaluated using the ΔCq, geNorm, BestKeeper, NormFinder and RefFinder methods and software. Actg1 exhibited the highest stability in the SMG developmental stage, while Tubb5 was recommended as the most stable reference gene for the SMG regenerative stage. In summary, the present study provides evidence­based selections for superior reference genes in the SMG during the stages of development and functional regeneration.

The submandibular and sublingual glands maintain oral microbial homeostasis through multiple antimicrobial proteins.

Introduction: Oral microbial homeostasis is a key factor affecting oral health, and saliva plays a significant role in maintaining oral microbial homeostasis. The submandibular gland (SMG) and sublingual gland (SLG) together produce the most saliva at rest. Organic ingredients, including antimicrobial proteins, are rich and distinctive and depend on the type of acinar cells in the SMG and SLG. However, the functions of the SMG and SLG in maintaining oral microbial homeostasis have been difficult to identify and distinguish, given their unique anatomical structures. Methods: In this study, we independently removed either the SMG or SLG from mouse models. SMGs were aseptically removed in three mice in the SMG-removal group, and SLGs were aseptically removed in three mice in the SLG-removal group. Three mice from the sham-operated group were only anesthetized and incised the skin. After one month, we analyzed their oral microbiome through 16S rRNA sequencing. And then, we analyzed each gland using proteomics and single-cell RNA sequencing. Results: Our study revealed that the microbiome balance was significantly disturbed, with decreased bacterial richness, diversity, and uniformity in the groups with the SMG or SLG removed compared with the sham-operated group. We identified eight secreted proteins in the SMG and two in the SLG that could be involved in maintaining oral microbial homeostasis. Finally, we identified multiple types of cells in the SMG and SLG (including serous acinar, mucinous acinar, ductal epithelial, mesenchymal, and immune cells) that express potential microbiota homeostasis regulatory proteins. Our results suggest that both the SMG and SLG play crucial roles in maintaining oral microbial homeostasis via excretion. Furthermore, the contribution of the SMG in maintaining oral microbial homeostasis appears to be superior to that of the SLG. These findings also revealed the possible antimicrobial function of gland secreta. Discussion: Our results suggest that control of oral microbial dysbiosis is necessary when the secretory function of the SMG or SLG is impaired. Our study could be the basis for further research on the prevention of oral diseases caused by microbial dysbiosis.