The developmental roles of the extracellular matrix: beyond structure to regulation

Nanotechnological strategies for engineering complex tissues

Tissue engineering aims at developing functional substitutes for damaged tissues and organs. Before transplantation, cells are generally seeded on biomaterial scaffolds that recapitulate the extracellular matrix and provide cells with information that is important for tissue development. Here we review the nanocomposite nature of the extracellular matrix, describe the design considerations for different tissues and discuss the impact of nanostructures on the properties of scaffolds and their uses in monitoring the behaviour of engineered tissues. We also examine the different nanodevices used to trigger certain processes for tissue development, and offer our view on the principal challenges and prospects of applying nanotechnology in tissue engineering.

Biomimetics of the Extracellular Matrix: An Integrated Three-Dimensional Fiber-Hydrogel Composite for Cartilage Tissue Engineering

The native extracellular matrix (ECM) consists of an integrated fibrous protein network and proteoglycan-based ground (hydrogel) substance. We designed a novel electrospinning technique to engineer a three dimensional fiber-hydrogel composite that mimics the native ECM structure, is injectable, and has practical macroscale dimensions for clinically relevant tissue defects. In a model system of articular cartilage tissue engineering, the fiber-hydrogel composites enhanced the biological response of adult stem cells, with dynamic mechanical stimulation resulting in near native levels of extracellular matrix. This technology platform was expanded through structural and biochemical modification of the fibers including hydrophilic fibers containing chondroitin sulfate, a significant component of endogenous tissues, and hydrophobic fibers containing ECM microparticles.

Genetics of extracellular matrix remodeling during organ growth using the Caenorhabditis elegans pharynx model

The organs of animal embryos are typically covered with an extracellular matrix (ECM) that must be carefully remodeled as these organs enlarge during post-embryonic growth; otherwise, their shape and functions may be compromised. We previously described the twisting of the Caenorhabditis elegans pharynx (here called the Twp phenotype) as a quantitative mutant phenotype that worsens as that organ enlarges during growth. Mutations previously known to cause pharyngeal twist affect membrane proteins with large extracellular domains (DIG-1 and SAX-7), as well as a C. elegans septin (UNC-61). Here we show that two novel alleles of the C. elegans papilin gene, mig-6(et4) and mig-6(sa580), can also cause the Twp phenotype. We also show that overexpression of the ADAMTS protease gene mig-17 can suppress the pharyngeal twist in mig-6 mutants and identify several alleles of other ECM-related genes that can cause or influence the Twp phenotype, including alleles of fibulin (fbl-1), perlecan (unc-52), collagens (cle-1, dpy-7), laminins (lam-1, lam-3), one ADAM protease (sup-17), and one ADAMTS protease (adt-1). The Twp phenotype in C. elegans is easily monitored using light microscopy, is quantitative via measurements of the torsion angle, and reveals that ECM components, metalloproteinases, and ECM attachment molecules are important for this organ to retain its correct shape during post-embryonic growth. The Twp phenotype is therefore a promising experimental system to study ECM remodeling and diseases.