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Vitronectin, a principal cell adhesion molecule in plasma and extracellular matrix, mediates cell adhesion and spreading via the alpha V family of integrins. In this study we demonstrate that decorin, a small dermatan sulfate proteoglycan, regulates extracellular matrix remodeling in rabbit synovial fibroblasts adhering to vitronectin. Decorin induced the expression of the matrix metalloproteinase collagenase (MMP-1) when present on the substrate with vitronectin, or with the 120-kDa cell-binding domain of fibronectin, but not when present with intact fibronectin or Type I collagen. Secreted collagenase was detected within 8 h of adhesion, there was no associated alteration in cell shape or focal contact formation in cells adhering to decorin plus vitronectin, whereas cell rounding was observed in cells adhering to decorin plus the 120-kDa fragment of fibronectin. The core protein of decorin, but not the glycosaminoglycan moiety, was sufficient to induce collagenase expression on both substrates; however, the glycosaminoglycan moiety of decorin as well as the core were required for cell rounding observed in cells adhering to the 120-kDa domain of fibronectin. The collagenase-inducing effect of decorin seems to be independent of its effects on transforming growth factor-beta, as function-blocking antibodies against transforming growth factor-beta did not interfere with the collagenase-inducing effects of decorin. These data indicate that decorin has specific gene regulatory effects in cells when present in the matrix with vitronectin or the 120-kDa fragment of fibronectin, polypeptides that are present in actively remodeling tissues. Thus, in combination, these adhesion regulatory molecules transduce novel signals that may contribute to the tissue remodeling process in morphogenesis, wound healing and disease states.

Thirteen children with difficult systemic onset juvenile rheumatoid arthritis were treated with thalidomide. At 6 months, 11 of the 13 were able to reduce their use of prednisone ( P.002), with a concurrent improvement in erythrocyte sedimentation rate ( P.0001) and an increase in hemoglobin level ( P0.005). Juvenile rheumatoid arthritis improvement scores/=50% were obtained by 10 of the 13 children.

Adhesive interactions play a central role in cell migration. The regulation of these interactions requires the coordination of a multiplicity of signals, both spatially and temporally. The role of the integrin family has received considerable recent attention. Progress has been made in the elucidation of the mechanisms by which growth factors and other motogenic factors stimulate migration. Major advances have also been made in understanding the mechanisms by which the formation and breakdown of adhesive complexes are regulated, including the participation of members of the rho family. Despite these advances, many important questions remain, and the field seems well positioned to answer them.

Integrin-based adhesion has served as a model for studying the central role of adhesion in migration. In this article, we outline modes of migration, both integrin-dependent and -independent in vitro and in vivo. We next discuss the roles of adhesion contacts as signaling centers and linkages between the ECM and actin that allows adhesions to serve as traction sites. This includes signaling complexes that regulate migration and the interplay among adhesion, signaling, and pliability of the substratum. Finally, we address mechanisms of adhesion assembly and disassembly and the role of adhesion in cellular polarity.

Loss of Hax1, which is associated with a severe congenital neutropenia syndrome, impairs neutrophil uropod detachment and directed migration., Kostmann disease is an inherited severe congenital neutropenia syndrome associated with loss-of-function mutations in an adaptor protein HS1-associated protein X-1 (Hax1). How Hax1 regulates neutrophil function remains largely unknown. In this paper, we use ribonucleic acid interference to deplete Hax1 in the neutrophil-like cell line PLB-985 and identify Hax1 as a negative regulator of integrin-mediated adhesion and chemotaxis. Using microfluidics, we show that depletion of Hax1 impairs neutrophil uropod detachment and directed migration. Hax1-deficient cells also display increased integrin-mediated adhesion and reduced RhoA activity. Moreover, depletion of RhoA induces increased neutrophil adhesion and impaired migration, suggesting that Hax1 regulates neutrophil adhesion and chemotaxis through RhoA. Accordingly, activation of RhoA is sufficient to rescue adhesion of Hax1-deficient neutrophils. Together, our findings identify Hax1 as a novel regulator of neutrophil uropod detachment and chemotaxis through RhoA.

This article describes a microfluidic device for cell culture and chemotaxis studies under various temporal and spatial concentration gradients of the medium or chemoattractant. Vertical membranes formed using in situ fabrication are employed to avoid fluid flow inside the cell observation chamber. Thus, the medium and chemoattractants are primarily provided by diffusion, maintaining cell–cell communication via secreted factors. Neutrophils were used to demonstrate the capability of the device for chemotaxis research. Experiments exhibited successful migration up a concentration gradient of interleukin 8.

While the quantification of cell movement within defined biochemical gradients is now possible with microfluidic approaches, translating this capability to biologically relevant three-dimensional microenvironments remains a challenge. We introduce an accessible platform, requiring only standard tools (e.g. pipettes), that provides robust soluble factor control within a three-dimensional biological matrix. We demonstrate long-lasting linear and non-linear concentration profiles that were maintained for up to ten days using 34.5 muL solute volume. We also demonstrate the ability to superimpose local soluble factor pulses onto existing gradients via defined dosing windows. The combination of long-term and transient gradient characteristics within a three-dimensional environment opens the door for signaling studies that investigate the migratory behavior of cells within a biologically representative matrix. To this end, we apply temporally evolving and long-lasting gradients to study the chemotactic responses of human neutrophils and the invasion of metastatic rat mammary adenocarcinoma cells (MtLN3) within three-dimensional collagen matrices.

SummaryGlucocorticoids decrease plasminogen activator (PA) activity in HTC rat hepatoma cells by inducing a specific inhibitor of PA activity (PAI). This inhibitor is similar in several biochemical properties to the PAI purified from bovine aortic endothelial cells (BAEs). We have used reverse fibrin autography and antiserum against BAE PAI to establish more fully the biochemical and immunological relationship of these inhibitors. Both inhibitors migrated with an apparent Mr of approximately 50,000, and the activity of both PAIs was stimulated by treatment with SDS suggesting that each of these molecules exists in both an active and a latent form. Antiserum to the BAE PAI immunoprecipi-tated all of the HTC PAI demonstrable by reverse fibrin autography. Finally, using this antiserum in a functional immunoassay, we have demonstrated that dexamethasone increases both active and latent PAI made by HTC cells. These results, indicate that HTC PAI and BAE PAI are antigenically as well as biochemically related molecules.

Introduction: Synovial fibroblasts invade cartilage and bone, leading to joint destruction in rheumatoid arthritis. However, the mechanisms that regulate synovial fibroblast invasion are not well understood. Focal adhesion kinase (FAK) has been implicated in cellular invasion in several cell types, and FAK inhibitors are in clinical trials for cancer treatment. Little is known about the role of FAK in inflammatory arthritis, but, given its expression in synovial tissue, its known role in invasion in other cells and the potential clinical availability of FAK inhibitors, it is important to determine if FAK contributes to synovial fibroblast invasion and inflammatory arthritis. Methods: After treatment with FAK inhibitors, invasiveness of human rheumatoid synovial fibroblasts was determined with Matrigel invasion chambers. Migration and focal matrix degradation, two components of cellular invasion, were assessed in FAK-inhibited rheumatoid synovial fibroblasts by transwell assay and microscopic examination of fluorescent gelatin degradation, respectively. Using mice with tumor necrosis factor α (TNFα)–induced arthritis in which fak could be inducibly deleted, invasion and migration by FAK-deficient murine arthritic synovial fibroblasts were determined as described above and arthritis was clinically and pathologically scored in FAK-deficient mice. Results: Inhibition of FAK in human rheumatoid synovial fibroblasts impaired cellular invasion and migration. Focal matrix degradation occurred both centrally and at focal adhesions, the latter being a novel site for matrix degradation in synovial fibroblasts, but degradation was unaltered with FAK inhibitors. Loss of FAK reduced invasion in murine arthritic synovial fibroblasts, but not migration or TNFα-induced arthritis severity and joint erosions. Conclusions: FAK inhibitors reduce synovial fibroblast invasion and migration, but synovial fibroblast migration and TNFα-induced arthritis do not rely on FAK itself. Thus, inhib ition of FAK alone is unlikely to be sufficient to treat inflammatory arthritis, but current drugs that inhibit FAK may inhibit multiple factors, which could increase their efficacy in rheumatoid arthritis.