Cell-nanofiber-based cartilage tissue engineering using improved cell seeding, growth factor, and bioreactor technologies

Biodegradable nanofibrous scaffolds serving as an extracellular matrix substitute have been shown to be applicable for cartilage tissue engineering. However, a key challenge in using nanofibrous scaffolds for tissue engineering is that the small pore size limits the infiltration of cells, which may result in uneven cell distribution throughout the scaffold. This study describes an effective method of chondrocyte loading into nanofibrous scaffolds, which combines cell seeding, mixing, and centrifugation to form homogeneous, packed cell-nanofiber composites (CNCs). When the effects of different growth factors are compared, CNCs cultured in medium containing a combination of insulin-like growth factor-1 and transforming growth factor-beta 1 express the highest mRNA levels of collagen type II and aggrecan. Radiolabeling analyses confirm the effect on collagen and sulfated-glycosaminoglycans (sGAG) production. Histology reveals chondrocytes with typical morphology embedded in lacuna-like space throughout the entire structure of the CNC. Upon culturing using a rotary wall vessel bioreactor, CNCs develop into a smooth, glossy cartilage-like tissue, compared to a rough-surface tissue when maintained in a static environment. Bioreactor-grown cartilage constructs produce more total collagen and sGAG, resulting in greater gain in net tissue weight, as well as express cartilage-associated genes, including collagen types II and IX, cartilage oligomeric matrix protein, and aggrecan. In addition, dynamic culture enhances the mechanical property of the engineered cartilage. Taken together, these results indicate the applicability of nanofibrous scaffolds, combined with efficient cell loading and bioreactor technology, for cell-based cartilage tissue engineering.