- The alveolar epithelium is the largest surface area of the body in continuous contact with the outside environment and is critical for effective gas exchange to support metabolism. The alveolar walls consist of three distinct layers: the alveolar epithelium, comprising type I and type II alveolar epithelial cells; a matrix scaffold; and the microvascular endothelium. Most of the alveolar surface is covered by thin type I epithelial cells that cover the matrix framework and are closely opposed to microvascular endothelial cells.
- RNA modification is a new paradigm of epigenetic regulation of gene expression. This evolving field has been coined as RNA epigenetics or epitranscriptomics. Extensive studies over recent years have shown that RNA modifications affect multiple steps of RNA metabolism, including RNA export, splicing, processing, stability, degradation, and translation. Among different forms of RNA modifications, N6-methyladenosine (m6A) modification is the most prevalent form of messenger RNA modification in eukaryotes, which is critically implicated in the regulation of cellular functions.
- In healthy articular cartilage, the extracellular matrix (ECM) is properly maintained by the overall anabolic and catabolic balance of slow synthesis and degradation, a so-called homeostatic state, under the influence of synovial metabolism. Though the ECM of articular cartilage tissue contains low amounts of hyaluronan (HA), its main components are collagen, type II, IX, and XI, and proteoglycans, such as aggrecan. Nevertheless, HA plays crucial roles in cartilage, especially in retaining aggrecan in tissues.