Interaction of hydroxyapatite nanoparticles with endothelial cells: internalization and inhibition of angiogenesis in vitro through the PI3K/Akt pathway

Abstract

Nano-hydroxyapatite (nano-HAP) has been proposed as a better candidate for bone tissue engineering; however, the interactions of nano-HAP with endothelial cells are currently unclear. In this study, HAP nanoparticles (HANPs; 20 nm np20 and 80 nm np80) and micro-sized HAP particles (m-HAP; 12 μm) were employed to explore and characterize cellular internalization, subcellular distribution, effects of HANPs on endothelial cell function and underlying mechanisms using human umbilical vein endothelial cells (HUVECs) as an in vitro model. It was found that HANPs were able to accumulate in the cytoplasm, and both adhesion and uptake of the HANPs followed a function of time; compared to np80, more np20 had been uptaken at the end of the observation period. HANPs were mainly uptaken via clathrin- and caveolin-mediated endocytosis, while macropinocytosis was the main pathway for m-HAP uptake. Unexpectedly, exposure to HANPs suppressed the angiogenic ability of HUVECs in terms of cell viability, cell cycle, apoptosis response, migration and capillary-like tube formation. Strikingly, HANPs reduced the synthesis of nitric oxide (NO) in HUVECs, which was associated with the inhibition of phosphatidylinositol 3-kinase (PI3K) and phosphorylation of eNOS. These findings provide additional insights into specific biological responses as HANPs interface with endothelial cells.

Endocytic mechanisms and osteoinductive profile of hydroxyapatite nanoparticles in human umbilical cord Wharton’s jelly-derived mesenchymal stem cells

“…Using human umbilical vein endothelial cells, we have previously shown that a large amount of HANPs was taken up during observation. 26 Comparatively, in the present study, less HANPs were internalized by hWJ-MSCs ( Figure 6B). Moreover, HANPs accumulated throughout the interior of electron-dense vacuoles ( Figure 4); consequently, at the same dose, there were fewer HANPs containing vacuoles in the cytoplasm.…”

The effect of glucose modification of hydroxyapatite nanoparticles on gene delivery

“…Our results of the transfection assay indicated that HAp nanoparticles were internalized into ECs via caveolae‐mediated endocytosis rather than clathrin‐mediated endocytosis or micropinocytosis. Given their nanosizes and negatively charged surfaces, HAp particles could enter the ECs by caveolae‐mediated endocytosis . Caveola appears as a minute invagination on the cell membrane, especially ECs and adipocytes.…”

Role of Sirtuins in Tumor Angiogenesis

“…Novel approaches like employing various metal (160)(161)(162) and inorganic NPs (163)(164)(165) have been reported to modulate angiogenesis. Many studies revealed that the shape, size and surface charge of the nanoparticles plays a crucial role in their angiogenic behavior (166,167). Recently our group has reported that carbon-based nanoparticles (carbon quantum dots) with size <6 nm, inhibit angiogenic process and significantly reduce the expression level of VEGF, VEGFR2, and FGF (168).…”