Novel bioactivities of phosvitin in bone formation, collagen synthesis and bio-mineralization

Abstract

Egg yolk phosvitin is one of the most highly phosphorylated extracellular matrix proteins known in nature with unique physico-chemical properties deem ed to be critical during ex-vivo egg embryo development. We have utilized our unique live m ouse calvarial bone organ culture models under conditions which dissociates the two bone remodeling stages, viz., resorption by osteoclasts and formation by osteoblasts, to highlight important and to date unknown critical biological functions of egg phosvitin. In our resorption model live bone cultures were grown in the absence of ascorbate and were stimulated by parathyroid hormone (PTH) to undergo rapid osteoclast formation/differentiation with bone resorption. In this resorption model native phosvitin potently inhibited PTH-induced osteoclastic bone resorption with simultaneous new osteoid/bone formation in the absence of ascorbate (vitamin C). These surprising and critical observations were extended using the bone formation model in the absence o f ascorbate and in the presence of phosvitin which supported the above results. The results were corroborated by analyses for calcium release or uptake, tartrate-resistant acid phosphatase activity ... [TRUNCATED]