In vitro 30 nm silver nanoparticles promote chondrogenesis of human mesenchymal stem cells

Silver nanoparticles (Ag NPs) are one of the most widely used products in nano-medicine due to their broad-spectrum antimicrobial activity. In tissue engineering, Ag NPs are often incorporated as antibacterial agents in scaffolds, which are subsequently loaded with human bone marrow-derived mesenchymal stem cells (hMSCs). In this study, we investigated the effect of Ag NPs on chondrogenesis of hMSCs. The synthesized Ag NPs were spherical in shape, with a mean diameter of similar to 30 nm. After 24 h exposure, Ag NPs were taken up into hMSCs and mainly distributed in the cytoplasm, the nucleus and different sized vesicles. We examined the chondrogenesis through several methods, including glycosaminoglycan (GAG) detection, immunohistochemical staining for type II collagen and aggrecan and real-time PCR for Sry-related high-mobility-group box 9 (SOX9), cartilage oligomeric matrix protein (COMP) and type X collagen. The present results indicate that long-term exposure to Ag NPs (at a concentration of 10 mu g mL(-1) and 20 mu g mL(-1)) led to an increased expression of SOX9, COMP and GAG, while type II collagen expression was unaffected. Short-term exposure to Ag NPs (at a concentration of 30 mu g mL(-1) and 40 mu g mL(-1)) resulted in a slight increase in SOX9 expression, while no change in GAG, aggrecan, type II collagen or COMP content was found. Expression of type X collagen, a marker for hypertrophic chondrocytes, was reduced after both long-and short-term exposure. In conclusion, 30 nm Ag NPs have positive effects on chondrogenesis since they can promote the expression of chondrogenic markers while reducing hypertrophy of hMSCs.