The main focus of this article is the role of lipids in biomineralization. Much of the discussion on biomineralization focuses on proteins in these decades. Indeed, collagen and acidic noncollagenous proteins effectively serve as templates for mineralization. However, other macromolecules such as lipids and polysaccharides have received less attention despite their abundance at mineralization sites. The matrix vesicle (MV) theory is widely accepted as the induction of early mineralization. Although ion concentration within the vesicles has been discussed in the initial mineralization in this theory, the role of phospholipids that constitute the vesicle membrane has not been discussed much. Comprehensive considerations, including pathological mineralization, exist regardless of the localization of MVs, the involvement of bacteria in dental calculus formation, and biomineralization caused by marine organisms such as corals, suggesting that initial mineralization found in these biological conditions might be a common reaction relating to lipids. In contrast, despite the abundance of lipids, mineralization occurs only in the limited tissue within our body. In other words, gathering knowledge and creating a path to understanding about lipid-based mineralization is extremely important in proposing new bone disease treatment methods. This article describes how lipids influence nucleation, mineralization, and expansion during hard tissue formation. Impact statement Recent studies have accumulated evidence of mineralization involving phospholipids and the matrix vesicle (MV) theory. Mineralization occurs not only in the conventional vesicle form but also in flat membranes arrested by the matrix. The flat membrane is derived not only from MVs but also from various causes, such as cell rupture and cell apoptosis. Mineralization is greatly affected by alkaline phosphatases derived from cell membranes. By understanding phospholipid-based mineralization, it will be possible to design new mineralization-inducing materials centered on cellular components for early bone formation. This article is important for developing new strategies to induce bone mineralization.
Keywords: biomineralization; hierarchical mineralization; lipid; lipid mineral interactions; nonprotein molecules.