Figure 8.

Histological pictures and a schematic model of increased bone formation in sclerosteosis due to sclerostin deficiency. Representative Goldner staining of calvarial bones of a control (A) and a patient with sclerosteosis (B). Schematic model of sclerostin's mechanism of action in bone remodeling (C). Sclerostin produced by osteocytes may be transported through lacunae to the bone surface, where it inhibits osteoblastic bone formation. In sclerosteosis, loss of sclerostin may prolong the active bone-forming phase of osteoblasts and thereby increase the amount of bone formed by osteoblasts. The increased osteoid levels in sclerosteosis reflect this. In the absence of increased osteoclastic bone resorption, the increased bone formation results in a positive bone balance and, subsequently, in the excess bone mass of normal architecture and increased strength found in sclerosteosis. LC, lining cell. OB, osteoblast. OC, osteoclast. OCYT, osteocyte.