Calcium phosphate (CaP)

Calcium phosphate refers to a family of inorganic minerals, primarily in the form of hydroxyapatite, that constitute the structural matrix of vertebrate bones and teeth [13, 18]. It serves as a vital reservoir for calcium and phosphate ions, playing a central role in mineral homeostasis and skeletal integrity [1, 7]. In clinical pharmacology, calcium phosphate is recognized as a primary therapeutic target for bisphosphonates, a class of drugs used to treat osteoporosis and Paget's disease by binding to the mineral surface and inhibiting bone resorption [2, 18]. Beyond its structural and physiological roles, the pathological deposition of basic calcium phosphate (BCP) crystals in soft tissues, such as joints and arteries, is a key driver of osteoarthritis and vascular calcification [3, 5, 16]. In these contexts, BCP microcrystals act as pro-inflammatory and mitogenic agents, stimulating the production of matrix metalloproteinases and cytokines that lead to tissue damage [4, 5]. Therefore, targeting the formation, dissolution, and biological activity of calcium phosphate minerals is a significant strategy in both bone health and the management of crystal-associated degenerative diseases [3, 8].

Other names

HydroxyapatiteBasic calcium phosphateTricalcium phosphateBone mineralApatiteOctacalcium phosphate

Drugs such as bisphosphonates interact with calcium phosphate through high-affinity chemisorption to hydroxyapatite crystals, allowing the drugs to selectively accumulate on the bone surface where they are subsequently internalized by osteoclasts to inhibit bone resorption [2, 18]. In pathological states like osteoarthritis, basic calcium phosphate crystals interact with synovial cells and chondrocytes to trigger mitogenic signaling pathways and the production of inflammatory cytokines and matrix metalloproteinases [4, 5].