Hydroxyapatite accelerates differentiation and suppresses growth of MC3T3‐E1 osteoblasts

Abstract

Hydroxyapatite describes both the natural mineral phase of bone as well as the widely used calcium-phosphate implant substitute. Given that hydroxyapatite is a major component of the in vivo surface with which osteoblasts interact, it is surprising that most studies examining the regulation of osteoblast growth and differentiation utilize plastic surfaces. Here we demonstrate that the phenotype of mouse MC3T3-E1 osteoblasts is significantly altered on hydroxyapatite compared with plastic surfaces. Specifically, alkaline phosphatase activity and messenger RNA levels, markers of early stages of osteoblast differentiation, are increased in osteoblasts cultured on hydroxyapatite. The precocious appearance of alkaline phosphatase activity on the hydroxyapatite surface suggests that osteoblast differentiation is activated earlier compared with plastic surfaces. Osteocalcin expression, a marker of late-stage differentiation, is also increased on hydroxyapatite and further demonstrates enhanced differentiation. Cell counts indicate that fewer osteoblasts are present on hydroxyapatite versus plastic surfaces 24 h after plating. Measurement of osteoblast attachment, apoptosis, and necrosis indicated no differences between surfaces. In contrast, the number of bromodeoxyuridine-incorporating cells was significantly decreased on hydroxyapatite compared with plastic surfaces. Taken together, our findings indicate that hydroxyapatite enhances osteoblast differentiation while also suppressing growth.

Suppression of apoptosis by enhanced protein adsorption on polymer/hydroxyapatite composite scaffolds

“…In addition to PLLA/HAP scaffolds, poly(lactic-co-glycolic acid)/HAP (PLGA/HAP) scaffolds were also found to protect osteoblasts against apoptosis (data not shown). Consistent with our findings, Shu et al [26] recently reported that MC3T3-E1 cells cultured on sintered dense HAP disks were more differentiated than those on polystyrene plastic culture dishes as measured by osteogenic markers. However, they reported that the cell attachment and apoptosis were similar on these two different surfaces.…”

Combined Effect of Three Types of Biophysical Stimuli for Bone Regeneration

“…Both double-and triple-combination stimulation accelerated osteogenic differentiation compared with the unstimulated (control) or the single-stimulation groups because a higher expression of ALP and RUNX2 is reflective of more rapid osteogenic differentiation of ASCs. 31,32 Surprisingly, our in vivo data indicated that the higher expression of osteogenic markers in vitro did not guarantee a higher degree of bone formation in vivo. Although the osteogenic marker expression level in the CEU group was the highest in vitro, the E (single) and CE (double) groups showed a higher degree of new bone formation than the CEU group (triple) in vivo.…”

Medical Application of Calcium Orthophosphate Bioceramics

“…These observations underscore an expected bioactivity of HA and make HA bioceramics well suited for bone reconstruction. Osteoblasts cultured on porous HA bioceramics appeared to exhibit a higher adhesion, an enhanced differentiation and suppressed proliferation rates when compared to the non-porous controls [643,644]. Furthermore, formation of distinct resorption pits on HA [645] and β-TCP [634] surfaces in the presence of osteoclasts was observed.…”