Morphological and functional changes in RAW264 macrophage‐like cells in response to a hydrated layer of carbonate‐substituted hydroxyapatite

Abstract

Synthetic hydroxyapatite (HAp) is used clinically as a material for bone prostheses owing to its good bone-bonding ability; however, it does not contribute to bone remodeling. Carbonate-substituted hydroxyapatite (CAp) has greater bioresorption capacity than HAp while having similar bone-bonding potential, and is therefore considered as a next promising material for bone prostheses. However, the effects of the CAp instability on inflammatory and immune responses are unknown in detail. Here, we show that the surface layer of CAp is more hydrated than that of HAp and induces changes in the shape and function of macrophage-like cells. HAp and CAp were synthesized by wet method and molded into disks. The carbonate content of CAp disks was 6.2% as determined by Fourier transform (FT) infrared spectral analysis. Diffuse reflectance infrared FT analysis confirmed that physisorbed water and surface hydroxyl groups (OH ) were increased whereas structural OH was decreased on the CAp as compared to the HAp surface. The degree of hydroxylation in CAp was comparable to that in bone-apatite structures, and the CAp surface exhibited greater hydrophilicity and solubility than HAp. We investigated immune responses to these materials by culturing RAW264 cells (macrophage precursors) on their surfaces. Cell spreading on the CAp disk was suppressed and the secretion level of inflammatory cytokines was reduced as compared to cells grown on HAp. These results indicate that the greater surface hydration of CAp surface can attenuate adverse inflammatory responses to implanted bone prostheses composed of this material. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1063-1070, 2017.

An oriented hydroxyapatite film with arrayed plate‐like particles enhance chondrogenic differentiation of ATDC5 cells

“…It has been reported that hydrophilic surfaces accelerate the spread of osteoblasts, while suppressing that of macrophages (Igeta et al, 2017;Iwasa et al, 2010). Chondrogenic ATDC5 cells showed weak adhesion to the DD-HAp film and cell spreading was inhibited (Figure 4).…”

“…It has been reported that hydrophilic surfaces accelerate the spread of osteoblasts, while suppressing that of macrophages (Igeta et al, 2017;Iwasa et al, 2010). Subsequently, they become flattened and columnar and differentiate into hypertrophic chondrocytes, after which they stop proliferating.…”

“…When ATDC5 cells attach to the DD-HAp films, inhibition of cell spreading induces morphological changes, which has the potential to drive cell fate without specific factors (Igeta et al, 2017;Nobusue et al, 2014). When ATDC5 cells attach to the DD-HAp films, inhibition of cell spreading induces morphological changes, which has the potential to drive cell fate without specific factors (Igeta et al, 2017;Nobusue et al, 2014).…”

“…Fourier transform-infrared (FT-IR) spectra were acquired using the KBr pellet method (FT/IR-4000; JASCO, Tokyo, Japan) (Igeta et al, 2017). Fourier transform-infrared (FT-IR) spectra were acquired using the KBr pellet method (FT/IR-4000; JASCO, Tokyo, Japan) (Igeta et al, 2017).…”

“…The crystal phase of the specimen was analyzed using a powder X-ray diffractometer (XRD, Bruker AXS D8 Advance; Bruker, MA), using Cu-Kα radiation. Fourier transform-infrared (FT-IR) spectra were acquired using the KBr pellet method (FT/IR-4000; JASCO, Tokyo, Japan) (Igeta et al, 2017).…”