Can we extrapolate the outcomes of in vitro studies on murine endothelium to studies of human platelet-endothelium interactions? A technical note

Alterations in the telomere length distribution and the subtelomeric methylation status in human vascular endothelial cells under elevated temperature in culture condition

Temperature-associated alteration in the telomere lengths of vascular endothelial cells has not been well investigated. Telomere length of human umbilical vein endothelial cells (HUVECs) cultured at a high temperature (42 °C) was analyzed. Here described are heat-associated phenotypical alterations of human vascular endothelial cell under prolonged heat stress in terms of telomere length, telomerase activity, and the expression of telomere associated proteins and heat shock proteins. The genomic DNA extracted from HUVECs cultured for 3 days under 42 °C was digested with methylation-sensitive and -insensitive isoschizomers and was subjected to genomic Southern blot probed with a telomere DNA fragment. Their telomere lengths and telomere length distributions were analyzed. Telomerase activity and the expressions of telomere-associated RNA, telomere-associated proteins (TERC, TERT, TRF1, and TRF2), and heat shock proteins (Hsp60, Hsp70, and Hsp90) were also analyzed. At 42 °C, cell growth was suppressed and the cell senescence rate was transiently elevated. A proportional decrease in the number of long telomeres was observed transiently at 42 °C. A trend of subtelomeric hypomethylation and lowered telomerase activity were observed at 42 °C after 3-day culture. The altered phenotypes on day 1 seemed reactive responses for cell protection to heat, and those on day 3 seemed exhausted reactions after 3-day culture. Maintained expression was observed in Hsps, TRF2, and TERC. These altered phenotypes might contribute to cell-survival under prolonged heat stress.

Enhanced endothelialization for developing artificial vascular networks with a natural vessel mimicking the luminal surface in scaffolds

Large tissue regeneration remains problematic because of a lack of oxygen and nutrient supply. An attempt to meet the metabolic needs of cells has been made by preforming branched vascular networks within a scaffold to act as channels for mass transport. When constructing functional vascular networks with channel patency, emphasis should be placed on anti-thrombogenic surface issues. The aim of this study was to develop a rapid endothelialization method for creating an anti-thrombogenic surface mimicking the natural vessel wall in the artificial vascular networks. Shear stress preconditioning and scaffold surface modification were investigated as effective approaches for promoting biomaterial endothelialization. We found that a transient increase in shear stress at the appropriate time is key to enhancing endothelialization. Moreover, surface modification with bioactive materials such as collagen and recombinant mussel adhesive protein fused with arginine-glycine-aspartic acid peptide (MAP-RGD) showed a synergetic effect with shear stress preconditioning. Platelet adhesion tests demonstrated the anti-thrombogenic potential of MAP-RGD itself without endothelialization. The rapid endothelialization method established in this study can be easily applied to preformed artificial vascular networks in porous scaffolds. Development of artificial vascular networks with an anti-thrombogenic luminal surface will open up a new chapter in tissue engineering and regenerative medicine.