CYTOKINES AND OSTEOPOROSIS

Bone remodeling is a complex process that involves cells from various lineages, the calcified extracellular bone matrix and a multitude of r egulation factors that act at both the tissular and cellular levels, R esorption and formation of bone are regulated at various levels during the series of events that lead from stem cell proliferation to differ entiation of mature cells, These events are controlled by calciotropic hormones, whose indirect cellular effects are mediated by the product ion of local factors, A host of cytokines and growth factors influence the proliferation and differentiation of bone cells, and their activi ties are modulated by a large number of hormones, Resorption by osteoc lasts is regulated at various stages of the differentiation process by cytokines produced by osteoblasts or stromal cells, Experimental stud ies in mice suggest that these local factors play a role in postoophor ectomy bone loss, although their exact mechanisms of action are not kn own, Evidence that these factors are involved in postmenopausal bone l oss is beginning to accumulate, opening up a vast field of investigati on.