Recent investigations credited important roles to C-type natriuretic peptide (CNP) signaling during chondrogenesis. This study investigated the putative role of CNP in transforming growth factor (TGF)-beta 1 induced in vitro chondrogenic differentiation of mesenchymal stem cells (MSCs) in pellet culture. MSCs were derived from human trabecular bone and were characterized on the basis of their cell surface antigens and adipogenic, osteogenic, and chondrogenic differentiation potential. TGF-beta 1 induced chondrogenic differentiation and glycosaminoglycan (GAG) synthesis was analyzed on the basis of basic histology, collagen type II, Sox 9 and aggrecan expressions, and Alcian blue staining. Results revealed that human trabecular bone-derived MSCs express CNP and NPR-B analyzed on the basis of RT-PCR and immunohistochemistry. In pellet cultures of MSCs TGF-beta 1 successfully induced chondrogenic differentiation and GAG synthesis. RT-PCR analyses of both CNP and NPR-B during this process revealed an activation of this signaling pathway in response to TGF-beta 1. Similar cultures induced with TGF-beta 1 and treated with different doses of CNP showed that CNP supplementation at 10(-8) and 10(-7) M concentrations significantly increased GAG synthesis in a dose dependent manner, whereas at 10(-6) M concentration this stimulatory effect was diminished. In conclusion, CNP/NPR-B signaling pathway is activated during TGF-beta 1 induced chondrogenic differentiation of human trabecular bone-derived MSCs and may strongly be involved in GAG synthesis during this process. This effect is likely to be a dose-dependent effect.