Synthetic small diameter vascular grafts with mechanical properties of native arteries, resistance to thrombosis and capacity to stimulate in situ endothelialization are an unmet clinical need. Poly(vinyl alcohol) hydrogel (PVA) is an excellent candidate as a vascular graft due to its tunable mechanical properties. However, the hydrophilicity and bio-inertness of PVA prevents endothelialization in vivo. We hypothesize that the modification of PVA with biomolecules and topographies creates a hemocompatible environment that also enhances bioactivity. PVA modified with fibronectin, RGDS peptide, cyclicRGD (cRGD) peptide, or heparin provided cell-adhesion motifs, which were confirmed by detection of nitrogen through X-ray photoelectron spectroscopy. Protein-and peptide-modified surfaces showed a slight increase in human vascular endothelial cell proliferation over unmodified PVA. With the exception of fibronectin modification, modified surfaces showed in vitro hemocompatibility comparable with unmodified PVA. To further improve bioactivity, cRGD-PVA was combined with gratings and microlens topographies. Combined modifications of 2µm gratings or convex topography and cRGD significantly improved human vascular endothelial cell viability on PVA. In vitro hemocompatibility testing showed that topography on cRGD-PVA did not significantly trigger an increase of platelet adhesion or activation compared with unpatterned PVA. Using the more physiologically relevant ex vivo hemocompatibility testing, all PVA grafts tested showed similar platelet adhesion to ePTFE and significantly lower platelet accumulation compared to collagen-coated ePTFE grafts. The

Costal cartilage is commonly harvested for various types of facial reconstructive surgery. The ability of costal chondrocytes (CCs) to produce relevant extracellular matrix, including glycosaminoglycans (GAGs), collagen type I, and collagen type II, makes them an appealing cell source for fibrocartilage tissue engineering. In order to obtain enough cells for tissue engineering, however, cell expansion will likely be necessary. This study examined CCs at passages 0, 1, 3, and 5, as well as temporomandibular (TMJ) disc cells, in a scaffoldless tissue engineering approach. TMJ disc constructs had over twice the collagen content of any other group, as well as the largest tensile properties; however, the substantial contraction of the constructs and limited cell numbers make it a non-feasible cell source for tissue engineering. In general, statistical differences in mechanical properties or total collagen content of the various CC groups were not observed; however, significantly more GAG was produced in the passaged CCs than the primary CCs. More collagen type II was also observed in some of the passaged cell groups than in passage 0. These results suggest not only feasibility but potential superiority of passaged CCs over primary CCs, which may lead to a functional engineered fibrocartilage tissue.

The effects of flow on endothelial cells have been widely examined for the ability of fluid shear stress to alter cell morphology and function; however, the effects of endothelial cell morphology without flow have only recently been observed. An increase in lithographic techniques in cell culture spurred a corresponding increase in research aiming to confine cell morphology. These studies lead to a better understanding of how morphology and cytoskeletal configuration affect the structure and function of the cells. This review examines endothelial cell micropatterning research by exploring both the many alternative methods used to alter endothelial cell morphology and the resulting changes in cellular shape and phenotype. Micropatterning induced changes in endothelial cell proliferation, apoptosis, cytoskeletal organization, mechanical properties, and cell functionality. Finally, the ways these cellular manipulation techniques have been applied to biomedical engineering research, including angiogenesis, cell migration, and tissue engineering, is discussed.

Objective-This study examines the tissue engineering potential of passaged (P3) and primary (P0) articular chondrocytes (ACs) and costal chondrocytes (CCs) from skeletally-mature goats for use in the temporomandibular joint (TMJ).Design-These four cell types were assembled into scaffoldless tissue engineered constructs and cultured for 4 wks. The constructs were then tested for cell, collagen, and glycosaminoglycan (GAG) content with biochemical assays, and collagen types I and II with enzyme-linked immunosorbent assays. Constructs were also tested under tension and compression to determine biomechanical properties.Results-Both primary and passaged CC constructs had greater GAG/wet weight than AC constructs. Primary AC constructs had significantly less total collagen and contained no collagen type I. AC P3 constructs had the largest collagen I/collagen II ratio, which was also greater in passaged CC constructs relative to primary groups. Primary AC constructs were not mechanically testable, while passaged AC and CC constructs had significantly greater tensile properties than primary CC constructs. Conclusions-PrimaryCCs are considerably better than primary ACs and have potential use in tissue engineering when larger quantities of collagen type II are desired. The poor performance of the ACs, in this study, which contradicts the results seen with previous studies using immature bovine ACs, may thus be attributed to the animals' maturity. However, CC P3 cells appear particularly wellsuited for tissue engineering fibrocartilage of the TMJ due to the high quantity of collagen and GAG, and tensile and compressive mechanical properties.

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