Lif Deficiency Leads to Iron Transportation Dysfunction in Ameloblasts

Leukemia inhibitory factor (LIF), a member of the interleukin 6 family of cytokines, is involved in skeletal metabolism, blastocyst implantation, and stem cell pluripotency maintenance. However, the role of LIF in tooth development needs to be elucidated. The aim of the present study was to investigate the effect of Lif deficiency on tooth development and to elucidate the functions of Lif during tooth development and the underlying mechanisms. First, it was found that the incisors of Lif-knockout mice had a much whiter color than those of wild-type mice. Although there were no structural abnormalities or defective mineralization according to scanning electronic microscopy and computed tomography analysis, 3-dimensional images showed that the length of incisors was shorter in Lif^-/- mice. Microhardness and acid resistance assays showed that the hardness and acid resistance of the enamel surface of Lif^-/- mice were decreased compared to those of wild-type mice. In Lif^-/- mice, whose general iron status was comparable to that of the control mice, the iron content of the incisors was significantly reduced, as confirmed by energy-dispersive X-ray spectroscopy (EDS) and Prussian blue staining. Histological staining showed that the cell length of maturation-stage ameloblasts was shorter in Lif^-/- mice. Likewise, decreased expression of Tfrc and Slc40a1, both of which are crucial proteins for iron transportation, was observed in Lif^-/- mice and Lif-knockdown ameloblast lineage cell lines, according to quantitative reverse transcription polymerase chain reaction, immunohistochemistry, and Western blot. Moreover, the upregulation of Tfrc and Slc40a1 induced by Lif stimulation was blocked by Stattic, a signal transducer and activator of transcription 3 (Stat3) signaling inhibitor. These results suggest that Lif deficiency inhibits iron transportation in the maturation-stage ameloblasts, and Lif modulates expression of Tfrc and Slc40a1 through the Stat3 signaling pathway during enamel development.

Green apatites: hydride ions, electrons and their interconversion in the crystallographic channel

Hydride (H(-)) ions and electrons in channel sites of the lattice of calcium phosphate apatites are characterized. Solid-state chemical reduction using TiH2 is effective for doping of H(-) ions into apatites. Irradiation of the H(-) ion-doped apatite with ultraviolet (UV) light induces green coloration. Electron paramagnetic resonance (EPR) reveals that this colour centre is attributed to electrons captured at a vacant anion site in the crystallographic channel, forming F(+) centres. Transient H(0) atoms are detected at low temperatures by EPR. The concentration of UV-induced electrons in the apatite at room temperature decays according to second-order kinetics because of the chemical reactions involving two electrons; overall, electron generation and thermal decay can be described as: H(-) + O(2-) ↔ 2e(-) + OH(-). (1)H magic angle spinning nuclear magnetic resonance spectroscopy is used to identify H(-) ions in the apatite, which are characterized by a chemical shift of +3.4 ppm. Various types of O-H groups including OH(-) ions in the channel and protons bound to phosphate groups are concurrently formed, and are identified by considering the relationship between the O-H stretching frequency and the (1)H chemical shift. The complementary results obtained by EPR and NMR reveal that the H(-) ions and transient H(0) atoms are located at the centre of Ca3 triangles in the apatite, while the electrons are located in the centre of Ca6 octahedra. These findings provide an effective approach for identifying new classes of mixed-oxide-hydride or -electride crystals.

Trace elements can influence the physical properties of tooth enamel

In previous studies, we showed that the size of apatite nanocrystals in tooth enamel can influence its physical properties. This important discovery raised a new question; which factors are regulating the size of these nanocrystals? Trace elements can affect crystallographic properties of synthetic apatite, therefore this study was designed to investigate how trace elements influence enamel's crystallographic properties and ultimately its physical properties. The concentration of trace elements in tooth enamel was determined for 38 extracted human teeth using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The following trace elements were detected: Al, K, Mg, S, Na, Zn, Si, B, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se and Ti. Simple and stepwise multiple regression was used to identify the correlations between trace elements concentration in enamel and its crystallographic structure, hardness, resistance to crack propagation, shade lightness and carbonate content. The presence of some trace elements in enamel was correlated with the size (Pb, Ti, Mn) and lattice parameters (Se, Cr, Ni) of apatite nanocrystals. Some trace elements such as Ti was significantly correlated with tooth crystallographic structure and consequently with hardness and shade lightness. We conclude that the presence of trace elements in enamel could influence its physical properties.

A simple route to full structural analysis of biophosphates and their application to materials discovery

An integrated suite of synthesis and characterisation techniques that includes synchrotron-based single crystal, powder X-ray diffraction, nuclear magnetic resonance and electron diffraction have been employed to uncover two new distinct structures in the Ca(x)Ba(2-x)P(2)O(7) polymorphic phosphate system. These materials have particular relevance for their application as both biomaterials and phosphors. Calcium barium pyrophosphate, CaBaP(2)O(7), was shown by a combination of spectroscopic and diffraction techniques to have two polymorphs distinct in structure from all of the five previously reported polymorphs of Ca, Sr and Ba pyrophosphate. A high temperature polymorph HT-CaBaP(2)O(7) prepared at 1200 °C is orthorhombic, of space group P(212121) with a = 13.0494 Å, b = 8.9677 Å, c = 5.5444 Å. A low temperature polymorph LT-CaBaP(2)O(7), prepared below 1000 °C, is monoclinic with space group P2(1)/c and dimensions a = 12.065 Å, b = 10.582 Å, c = 9.515 Å, β = 94.609°.