Endothelial cells from hematopoietic stem cells are functionally different from those of human umbilical vein

Effect of high-dose dexamethasone on endothelial haemostatic gene expression and neutrophil adhesion

Glucocorticoid usage especially at high doses is complicated by adverse outcomes such as thrombotic events or acceleration of inflammatory response in conditions like myeloma and osteonecrosis. The mechanism(s) through which high-dose dexamethasone (HDDEXA) causes vascular injury remains unclear. We hypothesized that HDDEXA sensitizes endothelial cells (EC) to the effect of inflammatory mediators and modulates endothelial haemostatic gene expression and leukocyte adhesion. Human umbilical vein endothelial cells (HUVECs) were grown in the absence or presence of HDDEXA and were also tested in the presence or absence of tumor necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS) or thrombin. mRNA and protein expression were measured and the functional consequences of HDDEXA preconditioning on cell adhesion molecules (CAM) were determined by agonist-mediated leukocyte adhesion assay. Treatment with HDDEXA resulted in an increased induction of CAM, tissue factor and von Willebrand factor, while down-regulating thrombomodulin and urokinase. HDDEXA alone had no effect on adhesion but resulted in enhanced TNF-alpha- and LPS-mediated adhesion of neutrophils. Together, these findings suggest that HDDEXA sensitizes HUVEC to the effect of inflammatory mediators and induces a pro-adhesive environment in primary EC. This finding is of importance when glucocorticoid usage is required at therapeutic high doses in patients with or without thrombotic risk factors.

Isolation and Characterization of Human Bone-Derived Endothelial Cells

Historically, the etiology of local bone pathologies, such as avascular necrosis, has been related to intravascular occlusion. Recent reports have highlighted the occlusion of arteries, venules, and/or capillaries in bone tissue. Endothelium of bone presumably participates locally in the formation of the microvascular thrombosis. It is also known that endothelial cells (ECs) play a central role in angiogenesis, a process seen in osteosarcoma, amongst other bone diseases. Given the well-recognized heterogeneity of ECs throughout the body, investigations of local bone disease related to endothelium processes may be more appropriately targeted on bone ECs rather than other primary ECs or an immortalized EC line. In the current study, mechanical and enzymatic methods are described to isolate ECs from cancellous human bone tissue followed by immunomagnetic bead separation to purify the cell populations. The human bone-derived endothelial cells (hBDECs) were characterized based on endothelial cell antigen expression and functional assays. This study is the first report of isolation and expansion of ECs from human bone tissue. Isolation of hBDECs in human vascular bone diseases may facilitate the study of the molecular and/or genetic abnormalities in the vasculature system that contributes to the initiation and/or progression of the disease.

Adult endothelial progenitor cells from human peripheral blood maintain monocyte/macrophage function throughout in vitro culture

Mononuclear cells (MNCs) isolated from peripheral blood by density gradient centrifugation were plated on human fibronectin-coated culture plates and cultured in EGM-2 medium. Attached spindle-shaped cells, reported as endothelial progenitor cells (EPCs) by some investigators, had elongated from adherent round cells, but had not proliferated from a small number of cells as supposed previously. The growth curve of the primary EPCs showed that the cells had little proliferative capacity. Flow cytometry analysis showed that the cells could express some of the endothelial lineage markers, while they could also express CD14, which is considered a marker of monocyte/macrophage lineages throughout culture. In endothelial function assays, the cells demonstrated a lower level of expression of eNOS than mature endothelial cells in the reverse transcription-polymerase chain reaction and did not show an ability to develop tube-like structures in angiogenesis assay in vitro. In this study, we identified the monocytoid function of EPCs by the combined Dil-labeled acetylated low-density lipoprotein (Dil-Ac-LDL) and Indian ink uptake tests. All the cells were double positive for Dil-Ac-LDL and Indian ink uptake at days 4, 14 and 28 of culture, which means the EPCs maintained monocytoid function throughout the culture. Therefore, although adult EPCs from peripheral MNCs have some endothelial lineage properties, they maintain typical monocytic function and have little proliferative capacity.

Tissue engineering of cultured skin substitutes

Skin replacement has been a challenging task for surgeons ever since the introduction of skin grafts by Reverdin in 1871. Recently, skin grafting has evolved from the initial autograft and allograft preparations to biosynthetic and tissue-engineered living skin replacements. This has been fostered by the dramatically improved survival rates of major burns where the availability of autologous normal skin for grafting has become one of the limiting factors. The ideal properties of a temporary and a permanent skin substitute have been well defined. Tissue-engineered skin replacements: cultured autologous keratinocyte grafts, cultured allogeneic keratinocyte grafts, autologous/allogeneic composites, acellular biological matrices, and cellular matrices including such biological substances as fibrin sealant and various types of collagen, hyaluronic acid etc. have opened new horizons to deal with such massive skin loss. In extensive burns it has been shown that skin substitution with cultured grafts can be a life-saving measure where few alternatives exist. Future research will aim to create skin substitutes with cultured epidermis that under appropriate circumstances may provide a wound cover that could be just as durable and esthetically acceptable as conventional split-thickness skin grafts. Genetic manipulation may in addition enhance the performance of such cultured skin substitutes. If cell science, molecular biology, genetic engineering, material science and clinical expertise join their efforts to develop optimized cell culture techniques and synthetic or biological matrices then further technical advances might well lead to the production of almost skin like new tissue-engineered human skin products resembling natural human skin.

The role of circulating precursors in vascular repair and lesion formation

The accumulation of smooth muscle cells (SMCs) plays a principal role in atherogenesis, post-angioplasty restenosis and transplantation-associated vasculopathy. Therefore, much effort has been expended in targeting the migration and proliferation of medial smooth muscle cells to prevent occlusive vascular remodeling. Recent evidence suggests that bone marrow-derived circulating precursors can also give rise to endothelial cells and smooth muscle cells that contribute to vascular repair, remodeling, and lesion formation under physiological and pathological conditions. This article overviews recent findings on circulating vascular progenitor cells and describes potential therapeutic strategies that target these cells to treat occlusive vascular diseases.

Temperature-dependent cell detachment on Pluronic gels

Cell culture on gels made of poly(ethylene oxide) and poly(propylene oxide) (Pluronic), which has a lower critical solution temperature around 30 degrees C, could be performed for 48 h. However, the Pluronic gels were highly hydrophilic and tended to dissolve in the culture medium. We achieved temperature-dependent detachment of cells from Pluronic gels containing or lacking extracellular matrix (ECM) by cooling the gels to 4 degrees C. Using normal human umbilical vein endothelial cells (HUVECs) grown on and released from Pluronic gels lacking ECM, we further found that the expression ratio of the surface markers CD34 and CD105 was twofold higher than for cells grown on polystyrene and removed with trypsin. In addition, the expression ratios for CD34 and CD105 on HUVECs cultivated on the Pluronic gels containing higher concentrations of ECM were lower, which may be due to ECM coating of the cell surface and, thus, interference with antibody binding. In summary, temperature-dependent detachment of cells from Pluronic gels allows the isolation of cells under mild conditions. This can be a powerful tool for surface marker analysis by flow cytometry.