Targeted disruption of the focal adhesion kinase (FAK) gene in mice is lethal at embryonic day 8.5 (E8.5). Vascular defects in FAK-/- mice result from the inability of FAK-deficient endothelial cells to organize themselves into vascular network. We found that, although fibronectin (FN) levels were similar, its organization was less fibrillar in both FAK-/- endothelial cells and mesoderm of E8.5 FAK-/- embryos, as well as in mouse embryonic fibroblasts isolated from mutant embryos. FAK catalytic activity, proline-rich domains, and location in focal contacts were all required for proper allocation and patterning of FN matrix. Cells lacking FAK in focal adhesions fail to translocate supramolecular complexes of integrin-bound FN and focal adhesion proteins along actin filaments to form mature fibrillar adhesions. Taken together, our data suggest that proper FN allocation and organization are dependent on FAK-mediated remodeling of focal adhesions.
Peritoneal dissemination in gastric cancer is a common fatal clinical condition with few effective therapies available. We studied the therapeutic effect of a tumor-targeting drug delivery system that uses cisplatin-encapsulated and Tf-conjugated PEG liposomes (Tf-PEG liposomes) in nude mice with peritoneal dissemination of human gastric cancer cells. Small unilamellar Tf-PEG, PEG or DSPC/CH liposomes (bare liposomes) encapsulating cisplatin were prepared by reversephase evaporation followed by extrusion. Electron microscopic studies revealed that Tf-PEG liposomes were internal- Key words: liposome; targeting; transferrin; peritoneal dissemination; gastric cancerPeritoneal dissemination is the most frequent noncurative factor and the most common type of recurrence after curative surgery in patients with gastric cancer. 1 Control of this metastasis is one of the most important challenges in treating gastric cancer. There have been few reports of effective treatment for peritoneal dissemination in patients with gastric cancer. 2,3 As a clinical locoregional chemotherapy, various anticancer drugs in solution form have been administered i.p. to expose the drug directly to peritoneal tumor cells. 4 However, small water-soluble molecules, such as cisplatin or mitomycin C, are absorbed easily through the large peritoneal surface into the circulating blood. It is difficult to maintain a high drug concentration for a long time in the peritoneal cavity. 5,6 Therefore, i.p. administration of anticancer drugs in solution form does not always produce the desired effect.Liposomes, known to be drug carriers, have various advantages. 7,8 First, they encapsulate various drugs such as water-soluble, lipid-soluble or high m.w. substances and release them in a sustained manner. Second, the antigenicity and toxicity of liposomes are very low because they consist of lipid, which is a natural component of organisms. Third, the biodistribution of liposomes can be controlled by the size or lipid component. Fourth, various materials, such as antibodies or chemical compounds, can modify the surfaces of liposomes. However, the therapeutic application of liposomes has been limited by their rapid clearance from the bloodstream and by their uptake by the RES. Recent efforts have been made to reformulate the liposome composition, to reduce its affinity to the RES. Liposomes modified with amphipathic PEG are not readily taken up by macrophages in the RES and, hence, stay in the circulation for a relatively long time. 9 -14 To increase the therapeutic effect and decrease side effects, tumor-specific targeting therapy has been advocated. Intracellular targeting using iron-saturated Tf as a ligand for receptor-mediated endocytosis has attracted attention. Tf is a glycoprotein that transports ferric ions in the body and the Tf receptor is internalized into cells by endocytosis through the binding of Tf. This receptormediated endocytosis is a normal physiologic process by which iron is delivered to cells. [15][16][17] Also, the Tf receptor concen...
S U M M A R YWe examined the distribution of cell adhesion-related molecules (CAMs) among mouse embryonic stem (ES) cells and the spatial distribution on cell surfaces before and during differentiation. The cell-cell heterogeneity of SSEA-1, PECAM-1, and ICAM-1 among the undifferentiated cells in the ES cell colonies was evident by immunohistochemistry and immuno-SEM, supporting the flow cytometry findings. In contrast, most undifferentiated ES cells strongly expressed CD9. SSEA-1 was located preferentially on the edge of low protuberances and microvilli and formed clusters or linear arrays of 3-20 particles. PECAM-1 and ICAM-1 were randomly localized on the free cell surfaces, whereas CD9 was preferentially localized on the microvilli or protuberances, especially in the cell periphery. Both the SSEA-1 ϩ fraction and the SSEA-1 Ϫ fraction of magnetic cell sorting (MACS) formed undifferentiated colonies after plating. Flow cytometry showed that these populations reverted separately again to a culture with a mixed phenotype. Differentiation induced by retinoic acid downregulated the expression of all CAMs. Immuno-SEM showed decreases of SSEA-1 in the differentiated ES cells, although some clustering still remained. Our findings help to elucidate the significance of these molecules in ES cell maintenance and differentiation and suggest that cell surface antigens may be useful for defining the phenotype of undifferentiated and differentiated ES cells.
Pluripotent embryonic stem (ES) cells can be a source of hepatocytes for bioartificial livers or transplantation. In this study, embryoid bodies (EBs) were formed from ES cells cultured in polypropylene conical tubes. The EBs were then inserted into a collagen scaffold three-dimensional culture system and stimulated with exogenous growth factors and hormones to induce hepatic histogenesis. The EB-derived cells expressed liver-specific genes, and albumin-positive cells formed cord-like structures that were not present in two-dimensional monolayer culture systems. However, these albumin- positive cells were not cytokeratin 18 positive. Electron microscopy showed immature hepatocyte- like cells having tight junctions, rough endoplasmic reticulum, and intercellular canaliculi. The scaffold including EB-derived hepatocyte-like cells was transplanted into the median lobes of partially hepatectomized nude mice. After 7 and 14 days, cells positive for both albumin and cytokeratin 18 appeared in the transplant and formed clustered aggregates. Thus the collagen scaffold three-dimensional culture system and the liver regeneration environment induced hepatocyte-like cells and hepatic lobule-like aggregates from EBs. Therefore, differentiating EBs in the scaffold culture system may be useful in developing bioartificial livers, secondary livers, and as pharmaceutical models.
Titanium oxide nanotubes with Ca ions on their surfaces were prepared as 2 mm cylindrical inserts and placed into surgically created bone defects in the femurs of Wistar rats. On day 3, fibroblast-like cells were present on the surface of the nanotube inserts and fibers were observed by scanning electron microscopy (SEM). On day 7, cells with alkaline phosphatase activity were present and identified as osteoblasts by SEM and transmission electron microscopy. New bone matrices were observed in and around the porous nanotube inserts by light microscopy. Compared with clinically used hydroxyapatite and tricalcium phosphate, beta-titanium oxide nanotubes promote faster acquisition and development of osteoblasts and bone tissues and have better bone regenerating ability after one week.
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