Cell migration on 2D surfaces is governed by a balance between counteracting tractile and adhesion forces. Although biochemical factors such as adhesion receptor and ligand concentration and binding, signaling through cell adhesion complexes, and cytoskeletal structure assembly/disassembly have been studied in detail in a 2D context, the critical biochemical and biophysical parameters that affect cell migration in 3D matrices have not been quantitatively investigated. We demonstrate that, in addition to adhesion and tractile forces, matrix stiffness is a key factor that influences cell movement in 3D. Cell migration assays in which Matrigel density, fibronectin concentration, and β1 integrin binding are systematically varied show that at a specific Matrigel density the migration speed of DU-145 human prostate carcinoma cells is a balance between tractile and adhesion forces. However, when biochemical parameters such as matrix ligand and cell integrin receptor levels are held constant, maximal cell movement shifts to matrices exhibiting lesser stiffness. This behavior contradicts current 2D models but is predicted by a recent force-based computational model of cell movement in a 3D matrix. As expected, this 3D motility through an extracellular environment of pore size much smaller than cellular dimensions does depend on proteolytic activity as broad-spectrum matrix metalloproteinase (MMP) inhibitors limit the migration of DU-145 cells and also HT-1080 fibrosarcoma cells. Our experimental findings here represent, to our knowledge, discovery of a previously undescribed set of balances of cell and matrix properties that govern the ability of tumor cells to migration in 3D environments.

Several surfactant-like peptides undergo self-assembly to form nanotubes and nanovesicles having an average diameter of 30 -50 nm with a helical twist. The peptide monomer contains 7-8 residues and has a hydrophilic head composed of aspartic acid and a tail of hydrophobic amino acids such as alanine, valine, or leucine. The length of each peptide is Ϸ2 nm, similar to that of biological phospholipids. Dynamic light-scattering studies showed structures with very discrete sizes. The distribution becomes broader over time, indicating a very dynamic process of assembly and disassembly. Visualization with transmission electron microscopy of quickfreeze͞deep-etch sample preparation revealed a network of openended nanotubes and some vesicles, with the latter being able to ''fuse'' and ''bud'' out of the former. The structures showed some tail sequence preference. Many three-way junctions that may act as links between the nanotubes have been observed also. Studies of peptide surfactant molecules have significant implications in the design of nonlipid biological surfactants and the understanding of the complexity and dynamics of the self-assembly processes.amino acids ͉ charged and hydrophobic residues ͉ nonlipid surfactants ͉ simplicity to complexity ͉ prebiotic enclosures M olecular self-assembly recently has attracted considerable attention for its use in the design and fabrication of nanostructures leading to the development of advanced materials (1, 2). The self-assembly of biomolecular building blocks plays an increasingly important role in the discovery of new materials and scaffolds (3, 4), with a wide range of applications in nanotechnology and medical technologies such as regenerative medicine and drug delivery systems (5, 6). Recently, Hartgerink et al. (7) reported the design of a chimeric material consisting of a hydrophobic alkyl tail and a hydrophilic peptide containing phosphorylated serine with an RGD motif that facilitates directional alignment of mineralization of hydroxyapatite.We previously described a class of ionic self-complementary peptide that spontaneously self-assemble to form interwoven nanofibers in the presence of monovalent cations (8 -10). These nanofibers further form a hydrogel consisting of greater than 99.5% water. The constituent of the hydrogel scaffold is made of peptides with alternating hydrophilic and hydrophobic amino acids. Such a sequence has a tendency to form an unusually stable ␤-sheet structure in water (8 -10). When the peptides form a ␤-sheet, they exhibit two surfaces, a hydrophilic surface consisting of charged ionic side chains and a hydrophobic surface with hydrophobic side chains. As a result, the self-assembly of these peptides is facilitated by electrostatic interactions on one side and the hydrophobic interaction on the other, in addition to the conventional ␤-sheet hydrogen bond along the backbones. The self-assembling peptide scaffolds have been demonstrated to serve as substrate for tissuecell attachment, extensive neurite outgrowth, and formation of active n...

Cultured trabecular meshwork (TM) cells are a valuable model system to study the cellular mechanisms involved in the regulation of conventional outflow resistance and thus intraocular pressure; and their dysfunction resulting in ocular hypertension. In this review, we describe the standard procedures used for the isolation of TM cells from several animal species including humans, and the methods used to validate their identity. Having a set of standard practices for TM cells will increase the scientific rigor when used as a model, and enable other researchers to replicate and build upon previous findings.