LAMININ, A MAJOR BASEMENT-MEMBRANE COMPONENT OF THE BLOOD-VESSEL, AS A NEGATIVE REGULATOR OF OSTEOCLASTOGENESIS

Laminin, the major basement membrane glycoprotein of the blood vessel, inducing many cellular responses, inhibited the differentiation of os teoclasts in a rat bone marrow culture system when immobilized on the surface of the culture wells, showing that laminin acts as a negative regulator of osteoclast differentiation in a nonsolubilized form. Lami nin inhibited the process of preosteoclast formation from early progen itor cells in bone marrow. This laminin-mediated inhibition of osteocl astogenesis was blocked by the addition of laminin fragment YIGSR, ind icating that the inhibitory effect of laminin was mediated via laminin receptors. This finding suggests a significant role of basement membr ane laminin of the blood vessels as a negative regulator of osteoclast ogenesis.