The effect of hydroxyapatite nanocrystals on microvascular endothelial cell viability and functions

Abstract

To favor bone reconstitution with biomaterials endothelial cells should maintain proper functions to drive angiogenesis. To this aim nanocrystals of hydroxyapatite (HA) have been synthesized and characterized on endothelial cells. Microvascular endothelial cells have been exposed to stoichiometric HA nanocrystals. Cell morphology and organization of cytoskeletal proteins have been monitored by SEM analysis and immunofluorescence. Biochemical markers of physiological and pathological responses of endothelial cells, endothelial constitutive nitric oxide synthase, and cycloxygenase-2 (ecNOS and COX-2, respectively) have been measured by immunofluorescence. Crystallized HA sustained endothelial survival without any cytotoxic effect. At the observation with SEM, endothelial cell morphology was maintained in the presence of HA. The localization and organization of beta-actin documented the formation of stress fibers, indicating an activation of endothelial cells induced by HA nanocrystals. Immunohistochemistry for biochemical key signaling pathways in endothelium demonstrated that nanocrystals of HA maintained the expression of ecNOS and did not increase COX-2 expression. In conclusion, the present findings indicate that HA nanocrystals exhibit high biocompatibility for microvascular endothelium. In the presence of HA nanocrystals endothelial cells maintain biochemical markers of healthy endothelium. They do not acquire a proinflammatory or thrombogenic phenotype, but express markers of functioning endothelium that might contribute to angiogenesis.

Enhancing the bioactivity of Poly(lactic-co-glycolic acid) scaffold with a nano-hydroxyapatite coating for the treatment of segmental bone defect in a rabbit model

“…It can promote the proliferation and metabolism of osteoblasts on the nanoscale because of its similar structure to natural bone. 41,42 Therefore, HA is a beneficial composition for use in bone defect repairing. 43 However crystalline HA degrades over a long period in vivo and a large amount of undegraded HA may thus hinder or slow complete bone reconstruction.…”

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

“…It has been reported that ECs maintain biochemical and morphological markers of healthy endothelium in the presence of HAP nanocrystals. 14 Holmes et al 15 conjugated polylactic acid (PLA) scaffolds with nano-HAP. Their experiments showed that ECs could grow on the surface of the scaffolds, and nano-HAP improved cell adhesion.…”

Molecular, Cellular and Pharmaceutical Aspects of Synthetic Hydroxyapatite Bone Substitutes for Oral and Maxillofacial Grafting

“…These vessels may transport osteoblastic precursor cells into HA granules, as already discussed for the vessel ingrowth into the nanostructured bone substitute NanoBone® [60,78]. Positive effects of HA on angiogenesis are supported by in vitro studies showing a high biocompatibility of microvascular endothelial cell son HA nanocrystals [79].…”