Calcium phosphate crystal (CaP)

Calcium phosphate crystals, primarily in the form of hydroxyapatite [Ca10(PO4)6(OH)2], are the fundamental inorganic constituents of vertebrate bone and teeth, providing essential structural support and acting as a reservoir for calcium and phosphate ions (Boskey, 2007). Under pathological conditions, these crystals can form in soft tissues, a process known as ectopic calcification, which is a major driver of diseases such as osteoarthritis, calcific tendonitis, and vascular calcification (McCarthy & Cheung, 2009). In the joints, basic calcium phosphate (BCP) crystals act as danger signals, activating the NLRP3 inflammasome and inducing the release of pro-inflammatory cytokines and matrix metalloproteinases that degrade cartilage (Ea et al., 2011). In the cardiovascular system, hydroxyapatite deposition in the arterial wall increases vascular stiffness and contributes to the progression of atherosclerosis and chronic kidney disease-related complications (Schanstra et al., 2015). Therapeutic strategies target these crystals by inhibiting their nucleation and growth using pyrophosphate analogs, chelating agents like sodium thiosulfate, or specific inhibitors like SNF472 (Perelló et al., 2018). Managing these deposits is challenging, as systemic inhibition of calcification can inadvertently interfere with healthy bone mineralization, leading to side effects like osteomalacia (Russell, 2011).

Other names

HydroxyapatiteBasic calcium phosphateBCP crystalsApatiteTricalcium phosphateOctacalcium phosphate

Inhibition of crystal nucleation, growth, and aggregation through surface adsorption, chelation of constituent calcium ions, and modulation of endogenous inhibitors like pyrophosphate.