Creating a spectrum of fibrocartilages through different cell sources and biochemical stimuli

In this study a scaffoldless approach was employed with two different cell sources and biochemical stimuli to engineer a spectrum of fibrocartilages representative of the different regions of the knee meniscus. Constructs composed of 100% fibrochondrocytes (FC) or a 50:50 co‐culture of fibrochondrocytes and chondrocytes (CC) were cultured in 10% fetal bovine serum medium or serum‐free “chondrogenic” medium, each ±10 ng/mL TGF‐β1 (+T). Constructs from these two cell groups and four culture conditions were cultured for 6 weeks. By varying the cell type and presence of the growth factor, GAG per dry weight of the constructs spanned that of native tissue, ranging 16–45% and 1–7% in the CC and FC groups, respectively. Collagen density was most dependent on cell type and was significantly lower than tissue values. The collagen I/II ratio could be manipulated by cell type and serum presence to span the native range, from 3.5 in the serum‐free CC group to over 1,000 in the FC groups treated with serum‐containing medium. Using the CC cell group in the presence of serum‐free medium dramatically increased the compressive stiffness to 128 ± 34 kPa, similar to native tissue. Similarly, serum‐free medium or TGF‐β1 treatment enhanced the tensile modulus by an order of magnitude, up to 3,000 kPa. Using two cell sources and manipulating biochemical stimuli, a range of fibrocartilaginous neotissues was engineered. Fibrocartilages such as the knee meniscus are characterized by heterogeneity in matrix and functional properties, and this work demonstrates a strategy for recreating these heterogeneous tissues. Biotechnol. Bioeng. 2008;100: 587–598. © 2007 Wiley Periodicals, Inc.