Composite articular cartilage engineered on a chondrocyte-seeded aliphatic polyurethane sponge

Cartilage engineering using cell-derived extracellular matrix scaffold in vitro

A cell-derived extracellular matrix (ECM) scaffold was constructed using cultured porcine chondrocytes via a freeze-drying method, and its ability to promote cartilage formation was evaluated in vitro. Scanning electron microscope (SEM) revealed that the scaffold had highly uniform porous microstructure. Then, rabbit chondrocytes were seeded dynamically on ECM scaffold and cultured for 2 days, 1, 2, and 4 weeks in vitro for analysis. Polyglycolic acid (PGA) scaffold was used as a control. On gross observation of neocartilage tissue, a silvery white cartilage-like tissue was observed after 1 week of culture in ECM scaffold, while similar morphology was seen only after 4 weeks in PGA scaffold. The volume of neocartilage-like tissue was significantly increased in both ECM and PGA groups. The compressive strength was gradually increased with time in ECM group, while gradually decreased in PGA group. DNA, glycosaminoglycan (GAG) and collagen contents also increased gradually with time in both groups, but showed more significant increase in ECM group. Histological staining for GAG (Safranin O staining) and type II collagen (immunohistochemistry) showed sustained accumulation of ECM molecules with time, which gradually and uniformly filled porous space in ECM scaffold. On the contrary, they accumulated only at the peripheral area of PGA scaffold. These results suggest that a novel cell-derived ECM scaffold can provide a promising environment for generating a high quality cartilage in vitro.

Synthesis and Characterization of Elastin-Mimetic Hybrid Polymers with Multiblock, Alternating Molecular Architecture and Elastomeric Properties

We are interested in developing elastin-mimetic hybrid polymers (EMHPs) that capture the multiblock molecular architecture of tropoelastin as well as the remarkable elasticity of mature elastin. In this study, multiblock EMHPs containing flexible synthetic segments based on poly(ethylene glycol) (PEG) alternating with alanine-rich, lysine-containing peptides were synthesized by step-growth polymerization using α,ω-azido-PEG and alkyne-terminated AKA(3)KA (K = lysine, A = alanine) peptide, employing orthogonal click chemistry. The resulting EMHPs contain an estimated three to five repeats of PEG and AKA(3)KA and have an average molecular weight of 34 kDa. While the peptide alone exhibited α-helical structures at high pH, the fractional helicity for EMHPs was reduced. Covalent cross-linking of EMHPs with hexamethylene diisocyanate (HMDI) through the lysine residue in the peptide domain afforded an elastomeric hydrogel (xEMHP) with a compressive modulus of 0.12 MPa when hydrated. The mechanical properties of xEMHP are comparable to a commercial polyurethane elastomer (Tecoflex SG80A) under the same conditions. In vitro toxicity studies showed that while the soluble EMHPs inhibited the growth of primary porcine vocal fold fibroblasts (PVFFs) at concentrations ≥0.2 mg/mL, the cross-linked hybrid elastomers did not leach out any toxic reagents and allowed PVFFs to grow and proliferate normally. The hybrid and modular approach provides a new strategy for developing elastomeric scaffolds for tissue engineering.

Engineering cartilage tissue

Cartilage tissue engineering is emerging as a technique for the regeneration of cartilage tissue damaged due to disease or trauma. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials, and signaling factors to the defect site. The objective of this review is to discuss the approaches that have been taken in this area, with an emphasis on various cell sources, including chondrocytes, fibroblasts, and stem cells. Additionally, biomaterials and their interaction with cells and the importance of signaling factors on cellular behavior and cartilage formation will be addressed. Ultimately, the goal of investigators working on cartilage regeneration is to develop a system that promotes the production of cartilage tissue that mimics native tissue properties, accelerates restoration of tissue function, and is clinically translatable. Although this is an ambitious goal, significant progress and important advances have been made in recent years.