Organized nanofibrous scaffolds that mimic the macroscopic and microscopic architecture of the knee meniscus

The menisci are crescent-shaped fibrocartilaginous tissues whose structural organization consists of dense collagen bundles that are locally aligned but show a continuous change in macroscopic directionality. This circumferential patterning is necessary for load transmission across the knee joint and is a key design parameter for tissue engineered constructs. To address this issue we developed a novel electrospinning method to produce scaffolds composed of circumferentially aligned (CircAl) nanofibers, quantified their structure and mechanics, and compared them with traditional linearly aligned (LinAl) scaffolds. Fibers were locally oriented in CircAl scaffolds, but their orientation varied considerably as a function of position (P<0.05). LinAl fibers did not change in orientation over a similar length scale (P>0.05). Cell seeding of CircAl scaffolds resulted in a similar cellular directionality. Mechanical analysis of CircAl scaffolds revealed significant interactions between scaffold length and region (P<0.05), with the tensile modulus near the edge of the scaffolds decreasing with increasing scaffold length. No such differences were detected in LinAl specimens (P>0.05). Simulation of the fiber deposition process produced "theoretical" fiber populations that matched the fiber organization and mechanical properties observed experimentally. These novel scaffolds, with spatially varying local orientations and mechanics, will enable the formation of functional anatomic meniscus constructs.