Chondrocyte phenotype in engineered fibrous matrix is regulated by fiber size

A biomaterial scaffold acting as a functional substitute for the native extracellular matrix provides space for cell accommodation. In this study, we seeded chondrocytes, isolated from 4- to 6-month-old calves, in 2 types of poly(L-lactide) scaffolds, composed of micro- and nanofibers, and compared the effects on cellular activities. Scanning electron microscopy revealed a well-spread morphology for chondrocytes grown on microfibers. In contrast, chondrocytes on the nanofibers were found to have a rounded morphology and displayed a disorganized actin cytoskeletal structure compared to the organized cytoskeleton seen in well-spread chondrocytes culture on the microfibrous scaffold. Both scaffolds supported chondrocyte proliferation, with a higher rate seen in cultures in nanofibrous scaffold. Quantitative reverse transcription-polymerase chain reaction analysis showed that both cultures supported expression of collagen types I and II and aggrecan. Biochemical analysis showed a higher level of sulfated glycosaminoglycan in the nanofiber culture, confirmed by more intense alcian blue histologic staining. The nanofiber cultures also showed higher immunostaining for collagen types II and IX, aggrecan, and cartilage proteoglycan link protein. Based on these results, we conclude that chondrocytes respond differently to fibrous scaffolds of varying diameters, and that the scaffolds made of nanofibrous biomaterial promote efficient cell-based cartilage tissue engineering.