Absence of bone sialoprotein (BSP) impairs primary bone formation and resorption: The marrow ablation model under PTH challenge

► Marrow ablation in BSP knockout mice: less medullary bone, resorbed more slowly. ► Lower levels of markers for mature osteoblasts and active osteoclasts in mutants. ► PTH maintained the medullary bone of wild type but not BSP−/− marrow ablated mice. ► PTH increased formation in both genotypes, reduced osteoclasts only in wild type. ► BSP is crucial for primary bone formation, modeling and response to PTH.