Regulation of the Catabolic Cascade in Osteoarthritis by the Zinc-ZIP8-MTF1 Axis

SummaryOsteoarthritis (OA), primarily characterized by cartilage degeneration, is caused by an imbalance between anabolic and catabolic factors. Here, we investigated the role of zinc (Zn2+) homeostasis, Zn2+ transporters, and Zn2+-dependent transcription factors in OA pathogenesis. Among Zn2+ transporters, the Zn2+ importer ZIP8 was specifically upregulated in OA cartilage of humans and mice, resulting in increased levels of intracellular Zn2+ in chondrocytes. ZIP8-mediated Zn2+ influx upregulated the expression of matrix-degrading enzymes (MMP3, MMP9, MMP12, MMP13, and ADAMTS5) in chondrocytes. Ectopic expression of ZIP8 in mouse cartilage tissue caused OA cartilage destruction, whereas Zip8 knockout suppressed surgically induced OA pathogenesis, with concomitant modulation of Zn2+ influx and matrix-degrading enzymes. Furthermore, MTF1 was identified as an essential transcription factor in mediating Zn2+/ZIP8-induced catabolic factor expression, and genetic modulation of Mtf1 in mice altered OA pathogenesis. We propose that the zinc-ZIP8-MTF1 axis is an essential catabolic regulator of OA pathogenesis

Dropout alignment allows homology recognition and evolutionary analysis of rDNA intergenic spacers

Subrepeats within the ribosomal gene (rDNA) intergenic spacer (IGS) play an important role in enhancing RNA polymerase I transcription. Despite this functional role and presumed selective constraint, there is surprisingly little sequence similarity among IGS subrepeats of different species. This sequence dissimilarity corresponds with the fast insertion-deletion (indel) rates observed in short mononucleotide microsatellites (here referred to as poly[N] runs, where N is any nucleotide), which are relatively abundant in rDNA IGS subrepeats. Some species have different types of IGS subrepeats that share species-specific poly(N) run patterns. This finding indicates that many IGS subrepeats within species share a common evolutionary history. Furthermore, by aligning sequences after modifying them by the dropout method, i.e., by disregarding poly(N) runs during the sequence aligning step, we sought to uncover evolutionarily shared similarities that fail to be recognized by current alignment programs. To ensure that the improved similarities in the computed alignments are not a chance artifact, we calibrated and corrected the IGS subrepeat sequences for the influence of repeat length and estimated the statistical significance of the alignments (in terms of a stringent p-value) obtained by the dropout method by comparing them to null models constructed using random sequence sets from the same genomes. We found that most diverse kinds of rDNA IGS subrepeats in one species must have been derived from a common ancestral subrepeat, and that it is possible to infer the evolutionary relationships among the IGS subrepeats of different species by comparative genomics methods based on dropout alignments.close3

Dynamic tuft cell expansion during gastric metaplasia and dysplasia

Abstract Tuft cells are chemosensory cells associated with luminal homeostasis, immune response, and tumorigenesis in the gastrointestinal tract. We aimed to elucidate alterations in tuft cell populations during gastric atrophy and tumorigenesis in humans with correlative comparison to relevant mouse models. Tuft cell distribution was determined in human stomachs from organ donors and in gastric pathologies including Ménétrier's disease, Helicobacter pylori gastritis, intestinal metaplasia (IM), and gastric tumors. Tuft cell populations were examined in Lrig1‐KrasG12D, Mist1‐KrasG12D, and MT‐TGFα mice. Tuft cells were evenly distributed throughout the entire normal human stomach, primarily concentrated in the isthmal region in the fundus. Ménétrier's disease stomach showed increased tuft cells. Similarly, Lrig1‐Kras mice and mice overexpressing TGFα showed marked foveolar hyperplasia and expanded tuft cell populations. Human stomach with IM or dysplasia also showed increased tuft cell numbers. Similarly, Mist1‐Kras mice had increased numbers of tuft cells during metaplasia and dysplasia development. In human gastric cancers, tuft cells were rarely observed, but showed positive associations with well‐differentiated lesions. In mouse gastric cancer xenografts, tuft cells were restricted to dysplastic well‐differentiated mucinous cysts and were lost in less differentiated cancers. Taken together, tuft cell populations increased in atrophic human gastric pathologies, metaplasia, and dysplasia, but were decreased in gastric cancers. Similar findings were observed in mouse models, suggesting that, while tuft cells are associated with precancerous pathologies, their loss is most associated with the progression to invasive cancer

Antibacterial and Antibiofilm Activity and Mode of Action of Magainin 2 against Drug-Resistant Acinetobacter baumannii

Antimicrobial peptides (AMPs) are promising therapeutic agents for treating antibiotic-resistant bacterial infections. Previous studies showed that magainin 2 (isolated from African clawed fogs Xenopus laevis) has antimicrobial activity against gram-positive and gram-negative bacteria. The present study was conducted to investigate the antibacterial activity of magainin 2 against Acinetobacter baumannii. Magainin 2 showed excellent antibacterial activity against A. baumannii strains and high stability at physiological salt concentrations. This peptide was not cytotoxic towards HaCaT cells and showed no hemolytic activity. Biofilm inhibition and elimination were significantly induced in all A. baumannii strains exposed to magainin 2. We confirmed the mechanism of magainin 2 on the bacterial outer and inner membranes. Collectively, these results suggest that magainin 2 is an effective antimicrobial and antibiofilm agent against A. baumannii strains

Apposition of Fibroblasts With Metaplastic Gastric Cells Promotes Dysplastic Transition

Background & aimsElements of field cancerization, including atrophic gastritis, metaplasia, and dysplasia, promote gastric cancer development in association with chronic inflammation. However, it remains unclear how stroma changes during carcinogenesis and how the stroma contributes to progression of gastric preneoplasia. Here we investigated heterogeneity of fibroblasts, one of the most important elements in the stroma, and their roles in neoplastic transformation of metaplasia.MethodsWe used single-cell transcriptomics to evaluate the cellular heterogeneity of mucosal cells from patients with gastric cancer. Tissue sections from the same cohort and tissue microarrays were used to identify the geographical distribution of distinct fibroblast subsets. We further evaluated the role of fibroblasts from pathologic mucosa in dysplastic progression of metaplastic cells using patient-derived metaplastic gastroids and fibroblasts.ResultsWe identified 4 subsets of fibroblasts within stromal cells defined by the differential expression of PDGFRA, FBLN2, ACTA2, or PDGFRB. Each subset was distributed distinctively throughout stomach tissues with different proportions at each pathologic stage. The PDGFRα+ subset expanded in metaplasia and cancer compared with normal, maintaining a close proximity with the epithelial compartment. Co-culture of metaplasia- or cancer-derived fibroblasts with gastroids showing the characteristics of spasmolytic polypeptide-expressing metaplasia-induced disordered growth, loss of metaplastic markers, and increases in markers of dysplasia. Culture of metaplastic gastroids with conditioned media from metaplasia- or cancer-derived fibroblasts also promoted dysplastic transition.ConclusionsThese findings indicate that fibroblast associations with metaplastic epithelial cells can facilitate direct transition of metaplastic spasmolytic polypeptide-expressing metaplasia cell lineages into dysplastic lineages