Enhancement of calcification by osteoblasts cultured on hydroxyapatite surfaces with adsorbed inorganic polyphosphate

• Published in: In vitro cellular & developmental biology. Animal Vol. 54; no. 6; pp. 449 - 457
• Main Authors: Kato, Kan, Morita, Koji, Hirata, Isao, Doi, Kazuya, Kubo, Takayasu, Kato, Koichi, Tsuga, Kazuhiro
• Format: Journal Article
• Language: English
• Published: New York Springer Science & Business Media LLC 01.06.2018; Springer US; Society for In Vitro Biology
• Subjects: Adsorption; Alkaline phosphatase; Animal Genetics and Genomics; Animals; Biocompatibility; Biomedical and Life Sciences; Bone growth; Calcification; Calcification, Physiologic - drug effects; Calcium; Calcium ions; Cell adhesion; Cell adhesion & migration; Cell Adhesion - drug effects; CELL AND TISSUE MODELS; Cell Biology; Cell Culture; Cell differentiation; Cell Differentiation - drug effects; Cell Proliferation - drug effects; Cells, Cultured; Contact angle; Density; Developmental Biology; Differentiation (biology); Durapatite - pharmacology; Extracellular matrix; Fibroblasts; Gene expression; Hydroxyapatite; Life Sciences; Mice; Mineralization; Osteoblastogenesis; Osteoblasts; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteocalcin; Osteogenesis - drug effects; Osteopontin; Plates; Polyphosphates - pharmacology; Regeneration; Regeneration (physiology); Scanning electron microscopy; Stem Cells; Surface chemistry; Surface roughness; Surgical implants; Toluidine; Toluidine blue; Transplants & implants; Water; Osteoblast; Calcification; Inorganic polyphosphate; Hydroxyapatite; Adsorption; Bone regeneration
• ISSN: 1071-2690; 1543-706X
• DOI: 10.1007/s11626-018-0257-3

Inorganic polyphosphate has been expected to accelerate bone regeneration. However, there are limited evidences to prove that polyphosphate adsorbed on the surface of a hydroxyapatite plate enhances calcification of cultured osteoblasts. In this study, we examined the effect of polyphosphate adsorbed onto the surface of a hydroxyapatite plate on the attachment, proliferation, differentiation, and calcification of osteoblasts. After hydroxyapatite plates were soaked in solutions of polyphosphate, the plate surfaces were analyzed by scanning electron microscopy and toluidine blue staining to confirm adsorption of polyphosphate. The hydroxyapatite plates were further subjected to the measurements of surface roughness, water contact angle, and the binding capacity of calcium ions. Cell culture experiments were carried out using MC3T3-E1 pre-osteoblastic cells. It was found that soaking a hydroxyapatite plate in a polyphosphate solution gave rise to an increase in surface roughness and reduction in water contact angle in a concentration-dependent manner, suggesting the adsorption of polyphosphate onto the surface of a hydroxyapatite plate. It was further observed that surface-adsorbed polyphosphate exhibited an inhibitory effect on cell adhesion and proliferation. In contrast, cell differentiation was promoted on hydroxyapatite plates with adsorbed polyphosphate, when assessed from expression of differentiation marker genes including alkaline phosphatase, osteopontin, and osteocalcin. In addition, calcification of the culture was enhanced on hydroxyapatite plates with relatively low density of adsorbed polyphosphate. Our results as a whole provided an evidence to show that there is a narrow window with regard to the surface density of adsorbed polyphosphate for the enhancement of osteoblast calcification.