Role of Active and Latent Transforming Growth Factor Beta in Bone Formation

At first reading the statement "TGF beta stimulates bone formation but inhibits mineralization" may appear to be an oxymoron. However, the bone formation process can take weeks to months to complete, and the unique properties of TGF beta allow this factor to be stored in bone matrix in a latent form, ready to be activated and inactivated at key, pivotal stages in this long process. TGF beta may act to trigger the cascade of events that ultimately leads to new bone formation. However, once this process is initiated, TGF beta must then be inactivated or removed because if present in the later stages of bone formation, mineralization will be inhibited. The unique properties of TGF beta and its role in bone remodeling are the subject of this review.