Lithium doped calcium phosphate cement maintains physical mechanical properties and promotes osteoblast proliferation and differentiation

Lithium prevents glucocorticoid-induced osteonecrosis of the femoral head by regulating autophagy

Autophagy may play an important role in the occurrence and development of glucocorticoid-induced osteonecrosis of the femoral head (GC-ONFH). Lithium is a classical autophagy regulator, and lithium can also activate osteogenic pathways, making it a highly promising therapeutic agent for GC-ONFH. We aimed to evaluate the potential therapeutic effect of lithium on GC-ONFH. For in vitro experiments, primary osteoblasts of rats were used for investigating the underlying mechanism of lithium's protective effect on GC-induced autophagy levels and osteogenic activity dysfunction. For in vivo experiments, a rat model of GC-ONFH was used for evaluating the therapeutic effect of oral lithium on GC-ONFH and underlying mechanism. Findings demonstrated that GC over-activated the autophagy of osteoblasts and reduced their osteogenic activity. Lithium reduced the over-activated autophagy of GC-treated osteoblasts through PI3K/AKT/mTOR signalling pathway and increased their osteogenic activity. Oral lithium reduced the osteonecrosis rates in a rat model of GC-ONFH, and restrained the increased expression of autophagy related proteins in bone tissues through PI3K/AKT/mTOR signalling pathway. In conclusion, lithium can restrain over-activated autophagy by activating PI3K/AKT/mTOR signalling pathway and up-regulate the expression of genes for bone formation both in GC induced osteoblasts and in a rat model of GC-ONFH. Lithium may be a promising therapeutic agent for GC-ONFH. However, the role of autophagy in the pathogenesis of GC-ONFH remains controversial. Studies are still needed to further explore the role of autophagy in the pathogenesis of GC-ONFH, and the efficacy of lithium in the treatment of GC-ONFH and its underlying mechanisms.

Lithium ion doped carbonated hydroxyapatite compositions: Synthesis, physicochemical characterisation and effect on osteogenic response in vitro

Hydroxyapatite is a commonly researched biomaterial for bone regeneration applications. To augment performance, hydroxyapatite can be substituted with functional ions to promote repair. Here, co-substituted lithium ion (Li⁺) and carbonate ion hydroxyapatite compositions were synthesised by an aqueous precipitation method. The co-substitution of Li⁺ and CO₃^2- is a novel approach that accounts for charge balance, which has been ignored in the synthesis of Li doped calcium phosphates to date. Three compositions were synthesised: Li⁺-free (Li 0), low Li⁺ (Li 0.25), and high Li⁺ (Li 1). Synthesised samples were sintered as microporous discs (70-75 % theoretical sintered density) prior to being ground and fractionated to produce granules and powders, which were then characterised and evaluated in vitro. Physical and chemical characterisation demonstrated that lithium incorporation in Li 0.25 and Li 1 samples approached design levels (0.25 and 1 mol%), containing 0.253 and 0.881 mol% Li⁺ ions, respectively. The maximum CO₃^2- ion content was observed in the Li 1 sample, with ~8 wt% CO₃, with the carbonate ions located on both phosphate and hydroxyl sites in the crystal structure. Measurement of dissolution products following incubation experiments indicated a Li⁺ burst release profile in DMEM, with incubation of 30 mg/ml sample resulting in a Li⁺ ion concentration of approximately 140 mM after 24 h. For all compositions evaluated, sintered discs allowed for favourable attachment and proliferation of C2C12 cells, human osteoblast (hOB) cells, and human mesenchymal stem cells (hMSCs). An increase in alkaline phosphatase (ALP) activity with Li⁺ doping was demonstrated in C2C12 cells and hMSCs seeded onto sintered discs, whilst the inverse was observed in hOB cells. Furthermore, an increase in ALP activity was observed in C2C12 cells and hMSCs in response to dissolution products from Li 1 samples which related to Li⁺ release. Complementary experiments to further investigate the findings from hOB cells confirmed an osteogenic role of the surface topography of the discs. This research has shown successful synthesis of Li⁺ doped carbonated hydroxyapatite which demonstrated cytocompatibility and enhanced osteogenesis in vitro, compared to Li⁺-free controls.

Velvet antler polypeptide combined with calcium phosphate coating to protect peripheral nerve cells from oxidative stress

Functionalizing biomaterial substrates with biological signals shows promise in regulating cell behaviors through mimicking cellular microenvironment. Calcium phosphate (CaP) coating is an excellent carrier for immobilizing biological molecules due to its non-toxicity, good biocompatibility, biodegradability, and favorable affinity to plenty of molecules. In this study, we reported the adhesion, the viability and proliferation behaviors after oxidative stress injury of Schwann cells RSC96 on CaP immobilized with the Velvet Antler Peptide (VAP) isolated from velvet antler through coprecipitation process in modified Dulbecco's phosphate-buffered saline (DPBS) containing VAP. This approach provided well retention of functional molecules up to 28 days, and supported the adhesion and proliferation of RSC96 after oxidative stress injury without cytotoxicity. The simple and reproducible method of coprecipitation suggests that CaP is an ideal carrier to functionalize materials with biological molecules for peripheral nerve repair-related applications.

ICP-Mass-Spectrometry Ionic Profile of Whole Saliva in Patients with Untreated and Treated Periodontitis

Over the past decade, there has been growing interest in the association between macro and trace minerals in body fluids and systemic diseases related to chronic inflammation and oxidative stress. Due to the paucity of data in the literature on periodontitis, the aim of this cross-sectional study was to assess the relationship between mineral elements in saliva and periodontal status in patients with untreated and treated periodontitis compared to periodontally healthy controls. Salivary samples from 66 nonsmoker healthy patients (20 periodontally healthy, 24 untreated severe periodontitis and 22 treated severe periodontitis) were analyzed by using inductively coupled plasma mass-spectrometry (ICP-MS). Significant increases in copper (Cu), sodium (Na), iron (Fe) and manganese (Mn) concentrations occurred in saliva of severe periodontitis subjects compared to periodontally healthy controls. No differences were detected between healthy controls and treated periodontitis patients apart from levels of zinc (Zn) and lithium (Li) that were found to be increased and reduced, respectively, in periodontitis group. Most subjects were correctly separated by cluster analysis into active periodontitis and periodontally healthy individuals. Treated periodontitis individuals were classified as healthy subjects. Based on these preliminary results, the assessment of salivary concentration of mineral elements might be useful in discriminating periodontal health and disease.

Preparation and Characterization of Iron-Doped Tricalcium Silicate-Based Bone Cement as a Bone Repair Material

Iron is one of the trace elements required by human body, and its deficiency can lead to abnormal bone metabolism. In this study, the effect of iron ions on the properties of tricalcium silicate bone cement (Fe/C3Ss) was investigated. It effectively solved the problems of high pH value and low biological activity of calcium silicate bone cement. The mechanical properties, in vitro mineralization ability and biocompatibility of the materials were systematically characterized. The results indicate that tricalcium silicate bone cement containing 5 mol% iron displayed good self-setting ability, mechanical properties and biodegradation performance in vitro. Compared with pure calcium silicate bone cement (C3Ss), Fe/C3Ss showed lower pH value (8.80) and higher porosity (45%), which was suitable for subsequent cell growth. Immersion test in vitro also confirmed its good ability to induce hydroxyapatite formation. Furthermore, cell culture experiments performed with Fe/C3Ss ion extracts clearly stated that the material had excellent cell proliferation abilities compared to C3Ss and low toxicity. The findings reveal that iron-doped tricalcium silicate bone cement is a promising bioactive material in bone repair applications.

The Skeletal-Protecting Action and Mechanisms of Action for Mood-Stabilizing Drug Lithium Chloride: Current Evidence and Future Potential Research Areas

Lithium, the lightest natural-occurring alkali metal with an atomic number of three, stabilizes the mood to prevent episodes of acute manic and depression. Multiple lines of evidence point to lithium as an anti-suicidal, anti-viral, anti-cancer, immunomodulatory, neuroprotective and osteoprotective agent. This review article provides a comprehensive review of studies investigating the bone-enhancing effects of lithium and its possible underlying molecular mechanisms. Most of the animal experimental studies reported the beneficial effects of lithium in defective bones but not in healthy bones. In humans, the effects of lithium on bones remain heterogeneous. Mechanistically, lithium promotes osteoblastic activities by activating canonical Wingless (Wnt)/beta (β)-catenin, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) and bone morphogenetic protein-2 (BMP-2) transduction pathways but suppresses osteoclastic activities by inhibiting the receptor activator of nuclear factor-kappa B (RANK)/receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG) system, nuclear factor-kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and calcium signaling cascades. In conclusion, lithium confers protection to the skeleton but its clinical utility awaits further validation from human clinical trials.

Lithium chloride enhances bone regeneration and implant osseointegration in osteoporotic conditions

Osteoporotic patients have a high risk of dental and orthopedic implant failure. Lithium chloride (LiCl) has been reported to enhance bone formation. However, the role of LiCl in the success rate of dental and orthopedic implants in osteoporotic conditions is still unknown. We investigated whether LiCl enhances implant osseointegration, implant fixation, and bone formation in osteoporotic conditions. Sprague-Dawley female rats (n = 18) were ovariectomized (OVX) to induce osteoporosis, and another nine rats underwent sham surgery. Three months after surgery, titanium implants were implanted in the tibia of the OVX and sham group rats. After implantation, the OVX rats were gavaged with 150 mg/kg/2 days of LiCl (OVX + LiCl group) or saline (OVX group), and sham group rats were gavaged with saline for 3 months. Implant osseointegration and bone formation were analyzed using histology, biomechanical testing, and micro computed tomography (micro-CT). More bone loss was observed in the OVX group compared to the control, and LiCl treatment enhanced bone formation and implant fixation in osteoporotic rats. In the OVX group, bone-implant contact (BIC) was decreased by 81.2 % compared to the sham group. Interestingly, the OVX + LiCl group showed 4.4-fold higher BIC compared to the OVX group. Micro-CT data of tibia from the OVX + LiCl group showed higher bone volume, trabecular thickness, trabecular number, and osseointegration compared to the OVX group. Maximum push-out force and implant-bone interface shear strength were 2.9-fold stronger in the OVX + LiCl group compared to the OVX group. In conclusion, LiCl enhanced implant osseointegration, implant fixation, and bone formation in osteoporotic conditions, suggesting LiCl as a promising therapeutic agent to prevent implant failure and bone loss in osteoporotic conditions.

In Vitro Human Umbilical Vein Endothelial Cells Response to Ionic Dissolution Products from Lithium-Containing 45S5 Bioactive Glass

Since lithium (Li⁺) plays roles in angiogenesis, the localized and controlled release of Li⁺ ions from bioactive glasses (BGs) represents a promising alternative therapy for the regeneration and repair of tissues with a high degree of vascularization. Here, microparticles from a base 45S5 BG composition containing (wt %) 45% SiO₂, 24.5% Na₂O, 24.5% CaO, and 6% P₂O₅, in which Na₂O was partially substituted by 5% Li₂O (45S5.5Li), were obtained. The results demonstrate that human umbilical vein endothelial cells (HUVECs) have greater migratory and proliferative response and ability to form tubules in vitro after stimulation with the ionic dissolution products (IDPs) of the 45S5.5Li BG. The results also show the activation of the canonical Wnt/β-catenin pathway and the increase in expression of proangiogenic cytokines insulin like growth factor 1 (IGF1) and transforming growth factor beta (TGFβ). We conclude that the IDPs of 45S5.5Li BG would act as useful inorganic agents to improve tissue repair and regeneration, ultimately stimulating HUVECs behavior in the absence of exogenous growth factors.

Acceleration of bone regeneration by activating Wnt/β-catenin signalling pathway via lithium released from lithium chloride/calcium phosphate cement in osteoporosis

By virtue of its excellent bioactivity and osteoconductivity, calcium phosphate cement (CPC) has been applied extensively in bone engineering. Doping a trace element into CPC can change physical characteristics and enhance osteogenesis. The trace element lithium has been demonstrated to stimulate the proliferation and differentiation of osteoblasts. We investigated the fracture-healing effect of osteoporotic defects with lithium-doped calcium phosphate cement (Li/CPC) and the underlying mechanism. Li/CPC bodies immersed in simulated body fluid converted gradually to hydroxyapatite. Li/CPC extracts stimulated the proliferation and differentiation of osteoblasts upon release of lithium ions (Li+) at 25.35 ± 0.12 to 50.74 ± 0.13 mg/l through activation of the Wnt/β-catenin pathway in vitro. We also examined the effect of locally administered Li+ on defects in rat tibia between CPC and Li/CPC in vivo. Micro-computed tomography and histological staining showed that Li/CPC had better osteogenesis by increasing bone mass and promoting repair in defects compared with CPC (P < 0.05). Li/CPC also showed better osteoconductivity and osseointegration. These findings suggest that local release of Li+ from Li/CPC may accelerate bone regeneration from injury through activation of the Wnt/β-catenin pathway in osteoporosis.