Neuropeptidergic regulation of bone resorption and bone formation.

Immunohistochemical studies have revealed an extensive network of nerve fibers in the vicinity and within the skeleton, not only in the periosteum of bone but also in cortical and trabecular bone as well as in the bone marrow. Phenotyping of the skeletal nerve fibers have demonstrated the expression of a restrictive panel of different signalling molecules including neuropeptides, neurotransmitters and neurotrophins. In this review, the presence of receptors for the neuropeptides vasoactive intestinal peptide, calcitonin gene-related peptide and substance P on osteoblasts and osteoclasts and the capacity of these receptors to regulate bone formation, osteoclast formation and activity are described. These findings, together with data obtained by chemically and surgically targeted nerve deletion and observations made in paraplegic patients, strongly suggest that neuro-osteogenic interactions play an important role in skeletal function.