biglycan

Biglycan is a small leucine-rich proteoglycan (SLRP) of the extracellular matrix. It is encoded by the BGN gene and is widely expressed in connective tissues, including skin, tendon, bone, cartilage, and vasculature. In the pericellular matrix, biglycan contributes to the organization and structure of the extracellular matrix.

The proteoglycan consists of a core protein rich in leucine-rich repeats, bearing glycosaminoglycan (GAG) chains. Typically, biglycan carries two GAG chains, usually chondroitin sulfate or dermatan sulfate, with some isoforms capable of bearing keratan sulfate. This combination supports interactions with other matrix components and signaling molecules.

Biglycan interacts with collagens, particularly type I and II, and influences collagen fibrillogenesis and matrix assembly. It also binds and modulates signaling molecules such as transforming growth factor-beta (TGF-β) and fibroblast growth factors, linking extracellular matrix organization to cellular responses.

In addition to structural roles, biglycan can function in innate immunity. When present in the extracellular environment, it can engage Toll-like receptors TLR2 and TLR4 on immune cells, promoting inflammatory signaling under certain conditions.

Biological and clinical relevance of biglycan spans development, bone formation, cartilage health, vascular remodeling, and fibrotic processes. Altered biglycan expression or function has been associated with osteoarthritis, fibrosis, and other connective tissue disorders in research contexts, making it a focus of study for understanding ECM dynamics and potential therapeutic targets.