Endothelin Receptor-A Inhibition Decreases Ductular Reaction, Liver Fibrosis, and Angiogenesis in a Model of Cholangitis

Mgp High-Expressing MSCs Orchestrate the Osteoimmune Microenvironment of Collagen/Nanohydroxyapatite-Mediated Bone Regeneration

Activating autologous stem cells after the implantation of biomaterials is an important process to initiate bone regeneration. Although several studies have demonstrated the mechanism of biomaterial-mediated bone regeneration, a comprehensive single-cell level transcriptomic map revealing the influence of biomaterials on regulating the temporal and spatial expression patterns of mesenchymal stem cells (MSCs) is still lacking. Herein, the osteoimmune microenvironment is depicted around the classical collagen/nanohydroxyapatite-based bone repair materials via combining analysis of single-cell RNA sequencing and spatial transcriptomics. A group of functional MSCs with high expression of matrix Gla protein (Mgp) is identified, which may serve as a pioneer subpopulation involved in bone repair. Remarkably, these Mgp high-expressing MSCs (MgphiMSCs) exhibit efficient osteogenic differentiation potential and orchestrate the osteoimmune microenvironment around implanted biomaterials, rewiring the polarization and osteoclastic differentiation of macrophages through the Mdk/Lrp1 ligand-receptor pair. The inhibition of Mdk/Lrp1 activates the pro-inflammatory programs of macrophages and osteoclastogenesis. Meanwhile, multiple immune-cell subsets also exhibit close crosstalk between MgphiMSCs via the secreted phosphoprotein 1 (SPP1) signaling pathway. These cellular profiles and interactions characterized in this study can broaden the understanding of the functional MSC subpopulations at the early stage of biomaterial-mediated bone regeneration and provide the basis for materials-designed strategies that target osteoimmune modulation.

Quercetin, a Flavonoid with Great Pharmacological Capacity

Quercetin is a flavonoid with a low molecular weight that belongs to the human diet's phenolic phytochemicals and nonenergy constituents. Quercetin has a potent antioxidant capacity, being able to capture reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive chlorine species (ROC), which act as reducing agents by chelating transition-metal ions. Its structure has five functional hydroxyl groups, which work as electron donors and are responsible for capturing free radicals. In addition to its antioxidant capacity, different pharmacological properties of quercetin have been described, such as carcinostatic properties; antiviral, antihypertensive, and anti-inflammatory properties; the ability to protect low-density lipoprotein (LDL) oxidation, and the ability to inhibit angiogenesis; these are developed in this review.

Cellular Interactions and Crosstalk Facilitating Biliary Fibrosis in Cholestasis

Biliary fibrosis is seen in cholangiopathies, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). In PBC and PSC, biliary fibrosis is associated with worse outcomes and histologic scores. Within the liver, both hepatic stellate cells (HSCs) and portal fibroblasts (PFs) contribute to biliary fibrosis, but their roles can differ. PFs reside near the bile ducts and may be the first responders to biliary damage, whereas HSCs may be recruited later and initiate bridging fibrosis. Indeed, different models of biliary fibrosis can activate PFs and HSCs to varying degrees. The portal niche can be composed of cholangiocytes, HSCs, PFs, endothelial cells, and various immune cells, and interactions between these cell types drive biliary fibrosis. In this review, we discuss the mechanisms of biliary fibrosis and the roles of PFs and HSCs in this process. We will also evaluate cellular interactions and mechanisms that contribute to biliary fibrosis in different models and highlight future perspectives and potential therapeutics.