Osteoclasters

Osteoclasters is a term with limited standard usage. In most scientific contexts, the correct term for the bone-resorbing cells is osteoclasts; osteoclasters is sometimes encountered as a nonstandard plural or, in historical or surgical language, as a reference to tools or methods used to induce controlled bone fracture. The article below covers both senses where relevant.

Biology and function: Osteoclasts are large, multinucleated cells derived from the monocyte–macrophage lineage. They resorb mineralized bone by attaching to the bone surface and creating a sealed resorption compartment. Within this space they acidify the area through proton pumps and secrete proteolytic enzymes such as cathepsin K that degrade the organic matrix. Osteoclast activity is regulated by signaling pathways involving RANKL, RANK, and osteoprotegerin, as well as cytokines and hormones. Osteoclasts work in concert with osteoblasts in the bone remodeling cycle, balancing bone formation and resorption to maintain skeletal strength and mineral homeostasis.

Clinical relevance: Excessive osteoclast activity contributes to diseases such as osteoporosis and osteolytic metastases, while insufficient activity can impair bone remodeling. Therapeutic strategies to inhibit osteoclasts include bisphosphonates and monoclonal antibodies such as denosumab, which decrease bone resorption. Adverse effects can include hypocalcemia and, with some therapies, osteonecrosis of the jaw.

Surgical context: In historical or orthopaedic terminology, osteoclasters can refer to techniques or instruments used to perform osteoclasis, the deliberate fracturing of a bone to correct deformities. Modern practice more commonly uses osteotomy with fixation, though osteoclasis remains a concept in certain deformity-correction procedures.

See also: Osteoclast, bone remodeling, osteoclasis, osteolysis.