Sustained zinc release in cooperation with CaP scaffold promoted bone regeneration via directing stem cell fate and triggering a pro-healing immune stimuli. Huang Xin,Huang Donghua,Zhu Ting,Yu Xiaohua,Xu Kaicheng,Li Hengyuan,Qu Hao,Zhou Zhiyuan,Cheng Kui,Wen Wenjian,Ye Zhaoming Journal of nanobiotechnology Metal ions have been identified as important bone metabolism regulators and widely used in the field of bone tissue engineering, however their exact role during bone regeneration remains unclear. Herein, the aim of study was to comprehensively explore the interactions between osteoinductive and osteo-immunomodulatory properties of these metal ions. In particular, the osteoinductive role of zinc ions (Zn), as well as its interactions with local immune microenvironment during bone healing process, was investigated in this study using a sustained Zn delivery system incorporating Zn into β-tricalcium phosphate/poly(L-lactic acid) (TCP/PLLA) scaffolds. The presence of Zn largely enhanced osteogenic differentiation of periosteum-derived progenitor cells (PDPCs), which was coincident with increased transition from M1 to M2 macrophages (M[Formula: see text]s). We further confirmed that induction of M2 polarization by Zn was realized via PI3K/Akt/mTOR pathway, whereas marker molecules on this pathway were strictly regulated by the addition of Zn. Synergically, this favorable immunomodulatory effect of Zn further improved the osteogenic differentiation of PDPCs induced by Zn in vitro. Consistently, the spontaneous osteogenesis and pro-healing osteoimmunomodulation of the scaffolds were thoroughly identified in vivo using a rat air pouch model and a calvarial critical-size defect model. Taken together, Zn-releasing bioactive ceramics could be ideal scaffolds in bone tissue engineering due to their reciprocal interactions between osteoinductive and immunomodulatory characteristics. Clarification of this synergic role of Zn during osteogenesis could pave the way to develop more sophisticated metal-ion based orthopedic therapeutic strategies. 10.1186/s12951-021-00956-8

Runx2/Osterix and Zinc Uptake Synergize to Orchestrate Osteogenic Differentiation and Citrate Containing Bone Apatite Formation. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Citrate is essential to biomineralization of the bone especially as an integral part of apatite nanocomposite. Citrate precipitate of apatite is hypothesized to be derived from mesenchymal stem/stromal cells (MSCs) upon differentiation into mature osteoblasts. Based on C-labeled signals identified by solid-state multinuclear magnetic resonance analysis, boosted mitochondrial activity and carbon-source replenishment of tricarboxylic acid cycle intermediates coordinate to feed forward mitochondrial anabolism and deposition of citrate. Moreover, zinc (Zn) is identified playing dual functions: (i) Zn influx is influenced by ZIP1 which is regulated by Runx2 and Osterix to form a zinc-Runx2/Osterix-ZIP1 regulation axis promoting osteogenic differentiation; (ii) Zn enhances citrate accumulation and deposition in bone apatite. Furthermore, age-related bone loss is associated with Zn and citrate homeostasis; whereas, restoration of Zn uptake alleviates age-associated declining osteogenic capacity and amount of citrate deposition. Together, these results indicate that citrate is not only a key metabolic intermediate meeting the emerging energy demand of differentiating MSCs but also participates in extracellular matrix mineralization, providing mechanistic insight into Zn homeostasis and bone formation. 10.1002/advs.201700755

Real-Time Fluorescence Visualization of the Dynamic Distribution of Zn Ions during Osteoblast Differentiation. Analytical chemistry The differentiation and maturation of osteoblasts are essential for bone formation. Zn plays a crucial role in cell differentiation and is involved in osteogenic differentiation. The concentration and distribution of Zn in the nucleus and cytoplasm indicate the differentiation states of osteoblasts. However, there is an absence of a real-time method for monitoring the dynamic fluctuations of endogenous Zn within the nucleus. Here, a novel Zn fluorescent probe () with nuclear membrane permeability was designed and developed, allowing for distribution throughout the entire cell, including the nucleus. The probe successfully showed the dynamic distribution and concentration changes of Zn in the nucleus and cytoplasm of preosteoblast MC3T3-E1 during the 21-day differentiation period. The results showed that free Zn increased significantly during differentiation of osteoblasts (2-21 days). Importantly, after 4 days of differentiation, osteoblasts are mainly distributed in the nucleus, which is confirmed by metallothionein expression. Subsequently, the level of free Zn in the cytoplasm remained at a high level, which promoted the increase in alkaline phosphatase activity and inhibited the activity of cis-aconitase in the tricarboxylic acid cycle, resulting in the accumulation of citric acid. This series of events promotes the formation of mineralized nodules. In the process of osteoblast differentiation, the detection time of Zn (≤7 days) is ahead of the late marker of alkaline phosphatase (14 days) and mineralized nodules (14-21 days). This indicates that Zn can be used as a biomarker and an intervention point for early differentiation of osteoblasts. 10.1021/acs.analchem.4c03996