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Abstract Dental implants are widely used to replace missing teeth, providing patients with unparalleled levels of effectiveness, convenience, and affordability. The biological basis for the clinical success of dental implants is osseointegration. Bone aging is a high-risk factor for the reduced osseointegration and survival rates of dental implants. In aged individuals, mesenchymal stem cells (MSCs) in the bone marrow show imbalanced differentiation with a reduction in osteogenesis and an increase in adipogenesis. This leads to impaired osseointegration and implant failure. This review focuses on the molecular mechanisms underlying the dysfunctional differentiation of aged MSCs, which primarily include autophagy, transcription factors, extracellular vesicle secretion, signaling pathways, epigenetic modifications, microRNAs, and oxidative stress. Furthermore, this review addresses the pathological changes in MSCs that affect osseointegration and discusses potential therapeutic interventions to enhance osseointegration by manipulating the mechanisms underlying MSC aging.

Abstract Background The biomaterial integration depends on its interaction with the host immune system. Monocyte-macrophage lineage cells are immediately recruited to the implant site, polarized into different phenotypes, and fused into multinucleated cells, thus playing roles in tissue regeneration. IL-1R-associated kinase 4 (IRAK4) inhibition was reported to antagonize inflammatory osteolysis and regulate osteoclasts and foreign body giant cells (FBGCs), which may be a potential target in implant osseointegration. Methods In in-vitro experiments, we established simulated physiological and inflammatory circumstances in which bone-marrow-derived macrophages were cultured on sand-blasted and acid-etched (SLA) titanium surfaces to evaluate the induced macrophage polarization, multinucleated cells formation, and biological behaviors in the presence or absence of IRAK4i. Then, bone marrow stromal stem cells (BMSCs) were cultured in the conditioned media collected from the aforementioned induced osteoclasts or FBGCs cultures to clarify the indirect coupling effect of multinucleated cells on BMSCs. We further established a rat implantation model, which integrates IRAK4i treatment with implant placement, to verify the positive effect of IRAK4 inhibition on the macrophage polarization, osteoclast differentiation, and ultimately the early peri-implant osseointegration in vivo. Results Under inflammatory conditions, by transforming the monocyte-macrophage lineage cells from M1 to M2, IRAK4i treatment could down-regulate the formation and activity of osteoclast and relieve the inhibition of FBGC generation, thus promoting osteogenic differentiation in BMSCs and improve the osseointegration. Conclusion This study may improve our understanding of the function of multinucleated cells and offer IRAK4i as a therapeutic strategy to improve early implant osseointegration and help to eliminate the initial implant failure.

Pto interaction (Pti) proteins are a group of proteins that can be phosphorylated by serine/threonine protein kinase Pto, which have diverse functions in plant development and stress response. In this study, we analyzed the phylogenetic relationship, gene structure, and conserved motifs of Pti1s and predicted the potential cis-elements in the promoters of Pti1 genes using bioinformatics methods. Importantly, we systematically summarized the diverse functions of Pti1s in tomato, rice, Arabidopsis, potato, apple, and cucumber. The potential cis-elements in promoters of Pti1s decide their functional diversity in response to various biotic and abiotic stresses. The protein kinase Pti1 was phosphorylated by Pto and then modulated the downstream signaling pathways for PTI and ETI in the disease insistence process. In addition, some transcription factors have been defined as Ptis (e.g., Pti4, Pti5, and Pti6) originally, which actually were ethylene-response factors (ERFs). Pti4, Pti5, and Pti6 were modulated by salicylic acid (SA), jasmonate (JA), and ethylene signaling pathways and regulated diverse defense-related gene expression to cope with Pst infection and insect wounding.

To examine the influence of mesoscale eddy on the natural phytoplankton community and its sinking rate changes, a comprehensive investigation cruise was carried out in the western South China Sea in autumn 2016. A total of 108 phytoplankton species were found, which belong to 54 phytoplankton genera; most of them were dominated by Dinophyta (54 genera), followed by Bacillariophyta (50 genera), Cyanophyta (3 genera), and Chrysophyta (1 genus). Bacillariophyta and Dinophyta were the main phytoplankton communities in the investigated sea area. The sinking rate of phytoplankton ranged from 0.12 to 3.17 m day–1, determined by the SETCOL method. The highest phytoplankton sinking rate was found in the 200-m water layer, followed by the DCM layer. No significant correlation was found between phytoplankton sinking rates and most of the environmental parameters during this cruise. At a similar time, we have carried out the estimation of carbon flux in the investigated sea area by using the sinking rate of phytoplankton, which showed that the carbon flux ranged from 2.41 × 10–6 to 0.006 mg C m–2 day–1; in addition, the maximum was at the 200-m layer. Phytoplankton community and sinking rate were significantly affected by the mesoscale eddy processes. The cold eddy could affect the community distribution of diatom and dinoflagellate, and the upwelling mainly affects the community of dinoflagellate. Both of them could contribute to a higher sedimentation rate of phytoplankton in the surface and DCM layers. Warm eddy could reduce the abundance of phytoplankton in the surface layer; simultaneously, the sinking rate of phytoplankton in the shallow water layer above 100 m is also reduced. These results can fill in the knowledge gap of mesoscale eddy processes in the study of phytoplankton community change and sinking rate; furthermore, it can provide insights into phytoplankton carbon and its implementation in further carbon sink.

The variability of size-fractionated chlorophyll a (Chl a) biomass and related environmental variables was investigated in a survey conducted in the northeastern South China Sea (NESCS), to assess their responses to upwelling, Kuroshio, and nutrients in the summer of 2017. The depth-weighted total Chl a concentration varied from 0.057 to 0.496 μg/L. The contribution of size-fractionated Chl a to total Chl a biomass was determined, with the contributions of pico-Chl a (0.2–2 μm), nano-Chl a (2–20 μm), and micro-Chl a (>20 μm) found to be 52.87%, 38.54%, and 8.59%, respectively. We found that nano-Chl a contributes more to total-Chl a than pico-Chl a in areas affected by upwelling. In addition, the results indicated an upward shift in the deep chlorophyll maximum (DCM) content in the upwelling area and the Kuroshio intrusion area. The Chl a biomass was increased in the physical process. Overall, correlation analysis showed that environmental variables (temperature, salinity, phosphate, silicate, nitrate, nitrite, ammonium) significantly influenced the phytoplankton biomass. However, physical processes determined the changes in environmental variables, with upwelling and Kuroshio being the main factors regulating the distribution of Chl a.

The influence of typhoon and Kuroshio intrusion process on the natural phytoplankton assemblages in the northeastern South China Sea (neSCS) was examined during a cruise in summer 2017. One hundred ninety-six seawater samples were collected and analyzed in the neSCS. In total, 299 species were identified belonging to 82 genera, mostly dominated by Bacillariophyta (159), followed by Dinophyta (132), Cyanophyta (4) and Chrysophyta (4). Among all, Thalassionema nitzschioides, Thalassionema frauenfeldii, Thalassiosira minima, in Bacillariophyta, Prorocentrum lenticulatum, Prorocentrum compressum in Dinophyta, and Trichodesmium thiebautii, in the Cyanophyta were the most dominated species, respectively. Correlation analysis shows compared with other groups Bacillariophyta was mostly influenced by silicate, whereas, Dinophyta and Cyanophyta showed significant correlation with temperature, salinity, phosphate, and nitrate. After the typhoon, the higher abundance of Dinophyta was observed, whereas it was lower in case of Bacillariophyta and Cyanophyta, shows typhoon “Roke“ and ”Haitang” had a significant influence on the phytoplankton assemblages, which could be manifested by the variations of total phytoplankton abundance in the surface water of neSCS. Overall, our present study provides the latest in-depth information about how the environmental factors influencing the phytoplankton density and diversity in the neSCS during summer.