Calcium ion-induced formation of β-sheet/-turn structure leading to alteration of osteogenic activity of bone morphogenetic protein-2

Abstract

Preserving bioactivity of bone morphogenetic protein 2 (BMP-2) still remains a challenge in protein-based therapy. It is not known how Ca2+ released from extracellular matrix or existing in physiological environment influences bioactivity in situ till now. Here, effects of extracellular Ca2+ on conformation and osteogenic bioactivity of recombinant human BMP-2 (rhBMP-2) were investigated systematically. In vitro results indicated that Ca2+ could bind rhBMP-2 rapidly and had no obvious effect on cell behaviors. Low concentration of Ca2+ (0.18 mM) enhanced rhBMP-2-induced osteogenic differentiation, while high Ca2+ concentration (>1.80 mM) exerted negative effect. In vivo ectopic bone formation exhibited similar trend. Further studies by circular dichroism spectroscopy, fluorescence spectroscopy, together with cell culture experiments revealed at low concentration, weak interaction of Ca2+ and rhBMP-2 slightly increased β-sheet/-turn content and facilitated recognition of BMP-2 and BMPRIA. But, high Ca2+ concentration (>1.8 mM) induced formation of Ca-rhBMP-2 complex and markedly increased content of β-sheet/-turn, which led to inhibition binding of rhBMP-2 and BMPRIA and thus suppression of downstream Smad1/5/8, ERK1/2 and p38 mitogen-associated protein kinase signaling pathways. Our work suggests osteogenic bioactivity of BMP-2 can be adjusted via extracellular Ca2+, which should provide guide and assist for development of BMP-2-based materials for bone regeneration.

Synthesis and characterization of CaSr-Metal Organic Frameworks for biodegradable orthopedic applications

“…These data suggest that the CaSr-MOFs may release Ca and Sr from the matrix and with a cumulative effect on osteoinduction. These results are supported by previous studies performed with alloys of Mg-Ca-Sr, which suggested that Ca and Sr by themselves may lead to osteoinduction 8,9 .…”

“…The alloys were also able to upregulate several osteogenic genes such as RUNX2, OSX, and ALP 7 . Additionally, Zhang et al and Berglund et al demonstrated that the presence of Ca, Mg and Sr cations simultaneously can lead to bone regeneration 8,9 . Therefore, materials that can release Ca and Sr simultaneously for extended periods of time can provide osteogenic signals.…”

Using biomimetically mineralized collagen membranes with different surface stiffness to guide regeneration of bone defects

“…Although it has been proved that a certain amount of surface chemical composition (e.g. Ca 2+ ) could affect proliferation and differentiation of MSCs (Hu et al, ; Shie, Chiang, Chen, Liu, & Chen, ; Zhang et al, ), the changes of surface chemical composition in different mineralized collagen groups in this study influenced the MSCs in aspects of proliferation and differentiation indistinctively and erratically. It may be due to the minor changes of chemical content among the different groups, which did not reach the effective dose.…”

Calcium-containing scaffolds induce bone regeneration by regulating mesenchymal stem cell differentiation and migration

“…Smad3 and Smad6 have an inhibitory effect on BMP signaling during osteoblast differentiation by targeting the BMP-responsive Smad1/5/8 complex [ 49 , 54 ]. It has been demonstrated that high extracellular calcium decreased the levels of phosphorylated SMAD1, ERK 1/2, and p38 and that Ca 2+ could bind BMP-2 extracellularly [ 55 , 56 ]. In contrast, low concentrations of extracellular calcium (0.18 mM) enhanced BMP-2-induced osteogenic differentiation [ 55 ].…”