Collagen synthesis by endothelial cells in culture

Immune Modulatory Properties of Collagen in Cancer

During tumor growth the extracellular matrix (ECM) undergoes dramatic remodeling. The normal ECM is degraded and substituted with a tumor-specific ECM, which is often of higher collagen density and increased stiffness. The structure and collagen density of the tumor-specific ECM has been associated with poor prognosis in several types of cancer. However, the reason for this association is still largely unknown. Collagen can promote cancer cell growth and migration, but recent studies have shown that collagens can also affect the function and phenotype of various types of tumor-infiltrating immune cells such as tumor-associated macrophages (TAMs) and T cells. This suggests that tumor-associated collagen could have important immune modulatory functions within the tumor microenvironment, affecting cancer progression as well as the efficacy of cancer immunotherapy. The effects of tumor-associated collagen on immune cells could help explain why a high collagen density in tumors is often correlated with a poor prognosis. Knowledge about immune modulatory functions of collagen could potentially identify targets for improving current cancer therapies or for development of new treatments. In this review, the current knowledge about the ability of collagen to influence T cell activity will be summarized. This includes direct interactions with T cells as well as induction of immune suppressive activity in other immune cells such as macrophages. Additionally, the potential effects of collagen on the efficacy of cancer immunotherapy will be discussed.

Vitamin C deficiency in guinea pigs differentially affects the expression of type IV collagen, laminin, and elastin in blood vessels

Vitamin C deficiency causes morphologic changes in the endothelial and smooth muscle compartments of guinea pig blood vessels. Endothelial cells synthesize the basement membrane components, type IV collagen and laminin, and smooth muscle cells synthesize elastin in blood vessels. Therefore, we examined the possibility that vitamin C deficiency affects the expression of these proteins. Decreased expression of types I and II collagens in other tissues of vitamin C-deficient guinea pigs is associated with weight loss and the consequent induction of insulin-like growth factor binding proteins; thus we also used food deprivation to induce weight loss. Female guinea pigs received a vitamin C-free diet, supplemented orally with ascorbate. Vitamin C-deficient guinea pigs received the same diet but no ascorbate, and the food-deprived group received no food, but were supplemented with vitamin C. Concentrations of mRNAs for basement membrane components and elastin in blood vessels were measured by Northern blotting; overall basement membrane metabolism was assessed by measuring immunoreactive laminin and type IV 7S collagen in serum. Laminin mRNA in blood vessels and serum laminin concentrations were unaffected by vitamin C deficiency. Concentrations of type IV collagen and elastin mRNAs in blood vessels were not significantly affected in moderately scorbutic guinea pigs (0-7% weight loss), but with increased weight loss, type IV collagen mRNA was 57% (P < 0.05) and elastin mRNA was 3% (P < 0. 01) of normal values. In food-deprived guinea pigs, type IV collagen mRNA was 51% (P < 0.05) and elastin mRNA was 35% (P < 0.05) of normal. Serum type IV 7S collagen concentrations were 25% of normal in scorbutic guinea pigs with extensive weight loss. The lower expression of type IV collagen and elastin mRNAs in blood vessels may contribute to defects observed in blood vessels during scurvy.

Synthesis of type VIII collagen by epithelial cells of human gingiva

The composition of the extracellular matrix produced by epithelial cells in contact with metabolically inert substrata was studied with antibodies specific for type VIII collagen. Type VIII collagen was present in the cell layer of cultured gingival epithelial cells, and at the epithelium-substratum interface of an explant culture model for junctional epithelium. Samples of the epithelial attachment apparatus (EAA) in vivo were collected by removing the junctional cells directly attached to the tooth (DAT cells) and the associated EAA matrix. The amount of material collected was sufficient for biochemical analysis of both intra- and extracellular components of the junctional cell-EAA complex. Immunological examination of the samples revealed that type VIII collagen was associated with epithelial cells forming the EAA in vivo. We suggest that this collagen type functions in the extracellular space as an attachment-promoting factor for gingival epithelial cells at the tooth surface.

Microvascular endothelial cell heterogeneity: interactions with leukocytes and tumor cells

Endothelium constitutes a highly specialized organ that lines the vascular system and lymphatic channels. This organ is a complex network of arteries, veins, and microvessels that differ in size, structure, and function. The unique and strategic location imposes functional demands on the endothelium that are far greater than just being a passive barrier. Endothelial cells have the ability to differentiate both in structure and function in response to the needs of diverse tissue environments, making this organ extremely heterogeneous. Although vascular endothelial cells share certain common properties, they differ in regard to structure, antigenic and cell surface determinants, adhesion molecules, and metabolic function. The unique cell surface profiles expressed by endothelial cells in different tissue locations can be recognized by specific populations of circulating leukocytes or tumor cells, which contribute to their arrest and invasion patterns. This article attempts to review our current understanding of endothelial cell heterogeneity and its significance to patterns of leukocyte and tumor cell trafficking.

Flow loaded canine carotid artery. II. Ultrastructural changes in the subendothelial layer

To study the subendothelial layer of the flow loaded arteries, blood flow changes were produced by constructing an arterio-venous shunt between the common carotid artery and the external jugular vein using eleven adult beagle dogs. One week after operation, the subendothelial layer of the flow loaded canine carotid arteries was observed with a transmission electron microscope. In the arteries loaded by highly elevated blood flow, the subendothelial layer showed thick subendothelial space (300 to 500 nm) with multilayered basement membrane. The microfilaments and microfibrils increased significantly. There were no collagen fibers. Spindle to cylindrical elastic fibers appeared in the luminal margin of the internal elastic lamina. On the other hand, in the control arteries, the subendothelial layer was thin (about 50 nm) with scanty basement-membrane-like material. There were a few microfilaments and microfibrils, but no collagen fibers. The luminal margin of the internal elastic lamina was smooth. It is suggested that these are the wall shear stress dependent subendothelial changes, which would be partly due to the increased protein synthesis by the endothelial cells stimulated by the wall shear stress and be partly due to the wall shear dependent mechanical stress transmitted from the endothelial surface.