Engineering Meniscus Form and Function via Multi-Layer Cell-Seeded Nanofibrous Scaffolds With Circumferentially Aligned Fibers

The menisci are crescent-shaped fibrocartilaginous tissues which function to transmit and distribute complex loading patterns between the femur and tibia of the knee joint. Meniscus function in tension arises from highly aligned collagen fibers which run in a circumferential manner between insertion sites on the tibial plateau (1,2). However, the meniscus is often injured, and partial removal of the meniscus represents the most commonly performed orthopaedic surgery, despite the fact that its removal increases the likelihood of osteoarthritis in the long-term (3). Tissue engineered scaffolds have emerged as a promising alternative to replace portions of the damaged meniscus (4). Toward replacement, we have developed aligned nanofibrous scaffolds that can recapitulate the mechanical anisotropy of the meniscus (5,6). More recently, we have developed an approach to replicate the circumferential macroscopic orientation of fibers using a novel electrospinning method (7). However, these organized scaffolds are relatively thin (<1 mm), and so multilayer scaffolds will be required to replicate the anatomic size of the native tissue. Moreover, cellular interactions will be crucial to the long-term function of these scaffolds. Thus, the objective of this study was to evaluate the morphological characteristics and mechanical properties of single layer and multilayer circumferentially aligned (CircAl) scaffolds seeded with mesenchymal stem cells (MSCs) and to compare them to scaffolds featuring linearly aligned (LinAL) fibers. We hypothesized that with increasing time in culture, matrix formed between layers would provide mechanical reinforcement, particularly in CircAl scaffolds where fiber rotation would be more likely to occur.