Yuanzhi Xu

Cross-Talking Between PPAR and WNT Signaling and its Regulation in Mesenchymal Stem Cell Differentiation

The pluripotent mesenchymal stem cells (MSC) are common precursors to adipocytes and osteoblasts. Large numbers of extracellular and intracellular signals and transcription factors moderate adipogenesis and osteoblastogenesis. Importantly, between adipogenic and osteogenic lineage commitment and differentiation, differentiation of MSCs into one lineage will inhibit their differentiation toward the other lineage. This balance is regulated by numerous signaling pathways. As we know, the peroxisome-proliferator-activated receptor-γ (PPAR-γ) and Wnt/β-catenin pathway are regarded as the master moderators of adipogenesis and osteogenesis. Moreover, governing the differentiation of MSCs to adipogenesis and osteoblastogenesis has significant implications in diverse areas of human health, from obesity to regenerative medicine to osteoporosis. Rivalry roles have been reported of the two pathways since the downstream products activated by Wnt-5a repress PPAR-γ transactivation through the H3K9 histone methyltransferase protein complexes. This review will discuss the inductive and inhibitive role of PPAR-γ in adipogenesis and osteoblastogenesis respectively, as well as the canonical Wnt/β-catenin pathway.

Toxicity of carbon nanotubes.

Carbon nanotubes (CNTs) find their extensive application as a promising material in medicine due to unique characteristics. However, such materials have been accompanied with potentially hazardous effects on human health. The toxicity of CNTs may vary depending on their structural characteristics, surface properties and chemical composition. To gain insight into the toxicity of CNTs in vivo and in vitro, we summarize contributing factors for the toxic effects of CNTs in this review. In addition, we elaborate on the toxic effects and mechanisms in target sites at systemic, organic, cellular, and biomacromolecule levels. Various issues are reported to be effected when exposed to CNTs including (1) blood circulation, (2) lymph circulation, (3) lung, (4) heart, (5) kidney, (6) spleen, (7) bone marrow, and (8) blood brain barrier. Though there have been published reports on the toxic effects of CNTs to date, more studies will still be needed to gain full understanding of their potential toxicity and underlying mechanisms.

Biomaterial and Mesenchymal Stem Cell for Articular Cartilage Reconstruction

Cartilage has poor ability of spontaneous repair. Traditional treatments such as microfracture, bone drilling and autologous osteochondral graft were not fully satisfactory to fulfill the clinical needs. The idea of mesenchymal stem cell (MSCs-based cartilage regeneration has been put forward for decades. Large number of studies have been conducted on the biological properties of MSCs, the factors which might facilitate chondrogenic differentiation of MSCs, as well as the scaffold materials for tissue engineering. Promising results have been reported for cartilage repair in animal models. But before massive clinical application of MSCs, more efforts are needed on: differentiation improvement toward mature cartilage chondrocytes instead of hypertrophic chondrocyes and in vitro/in vivo phenotype maintenance; engineering an ideal biomaterial, which can meet the needs of the cartilage regeneration; and performing more studies on critical defects of large animals.

Effect of storage temperature on the viability of human periodontal ligament fibroblasts

BACKGROUND The viability of periodontal ligament fibroblasts (PDLF) can affect the long-term prognosis of replanted avulsed teeth. When immediate replantation of an avulsed tooth is not possible, the cells should be incubated in a physiological storage medium instantly to maintain their biological activity. The ability of different storage media to preserve PDLF viability has been previously evaluated. However, few studies have showed the effect of temperature on the viability of PDLF cultured with various storage media in vitro. MATERIAL AND METHODS This study was designed to measure PDLF activity by CCK-8 assay to compare the effectiveness at 4, 22 (room temperature), and 37°C under various storage media. RESULTS Statistical analysis demonstrated that tap water, saline, and saliva decreased cell viability as the storage temperature increased. But the temperature played only a minor role on cell viability when cells were incubated in Hanks balanced salt solution (HBSS), Dubelcos modified Eagles medium (DMEM), or milk. CONCLUSIONS Within the parameters of this study, it seems that room temperature is adequate for storing the avulsed teeth in HBSS, DMEM, or milk in the extra-alveolar period.

Recent advances in cell sheet technology for periodontal regeneration.

Tissue engineering has yielded several successes in early clinical trials of regenerative medicine with grafting therapeutic cells seeded into biodegradable scaffolds. However this conventional cell delivery method has limited the fields progress. In recent decades, we have developed a novel cell transferring method, cell sheet technology that allows for controlled attachment and detachment of cells via simple temperature variations of a surface-intelligent temperatureresponsive polymer:poly (N-isopropylacrylamide). It has been widely applied to create functional tissue sheets with cells derived from various tissues to treat a wide range of diseases. Periodontal cell sheets non-invasively harvested from temperature- responsive culture surfaces have been successfully manufactured, resulting in communicative multilayered constructs. Transplantation of cell sheets onto periodontal defects has improved bone and tissue regeneration in animal models and humans and shows low immunogenicity. In this review, we summarize the recent advances of techniques in cell sheet engineering and its application for periodontal regeneration.

Review of and Perspectives on the Toxicology of Graphene-based Materials

Graphene possesses a wide range of potential biomedical applications because of the unique physical and chemical properties. However, the side effects of grapheme and its derivatives on a number of biological models even on human body are still not very clear. Therefore, to properly assess the potential risk of grapheme and its derivatives, we summarize the current state of academic knowledge on their toxicity.

DNA methylation is critical for tooth agenesis: implications for sporadic non-syndromic anodontia and hypodontia

Hypodontia is caused by interactions among genetic, epigenetic, and environmental factors during tooth development, but the actual mechanism is unknown. DNA methylation now appears to play a significant role in abnormal developments, flawed phenotypes, and acquired diseases. Methylated DNA immunoprecipitation (MeDIP) has been developed as a new method of scanning large-scale DNA-methylation profiles within particular regions or in the entire genome. Here, we performed a genome-wide scan of paired DNA samples obtained from 4 patients lacking two mandibular incisors and 4 healthy controls with normal dentition. We scanned another female with non-syndromic anodontia and her younger brother with the same gene mutations of the PAX9,MSX1,AXIN2 and EDA, but without developmental abnormalities in the dentition. Results showed significant differences in the methylation level of the whole genome between the hypodontia and the normal groups. Nine genes were spotted, some of which have not been associated with dental development; these genes were related mainly to the development of cartilage, bone, teeth, and neural transduction, which implied a potential gene cascade network in hypodontia at the methylation level. This pilot study reveals the critical role of DNA methylation in hypodontia and might provide insights into developmental biology and the pathobiology of acquired diseases.

The Correlations between Health-Related Quality of Life Changes and Pain and Anxiety in Orthodontic Patients in the Initial Stage of Treatment

This study aimed to assess generic health-related quality of life (HRQoL), pain intensity, and anxiety levels and the relationship between the three aspects in healthy young Chinese orthodontic patients in the early stage of orthodontic treatment. We enrolled 252 eligible participants (10–29 years old) to complete validated Chinese versions of questionnaires, including the State-Trait Anxiety Inventory (S-AI), the visual analogue scale (VAS), and the Short-Form 36-Item Health Survey (SF-36) at baseline and on days 1, 2, 3, 7, 14, and 30 after initial archwire placement (SF-36 only at baseline and day 30). The response rate was 96% (243 of 252). SF-36 had moderate reliability (Cronbachs alpha coefficient exceeding 0.7, good fit on day 30). Statistical significant changes were observed in physical function (P < 0.01), body pain (P = 0.01), and general health (P < 0.01) domains. Spearman correlation coefficients for SF-36 with S-AI were −0.131~−0.515 (P < 0.05); SF-36 with VAS were −0.141~−0.273 (P < 0.05), indicating significant but moderate negative correlations between HRQoL and pain/anxiety. Overall, the application of SF-36 in assessing HRQoL is reluctantly suitable for young Chinese orthodontic patients in the early stage of orthodontic treatment. Early treatment-related pain and anxiety are important factors in HRQoL.

Emerging roles of microRNAs in neural stem cells.

Neural stem cells (NSCs) are a small subset of primitive precursors that generate and maintain the main phenotypes of the nervous system. Their ability to undergo long-term proliferation and neural differentiation endows them with great potential in regenerative medicine. Therefore, the mechanisms by which NSCs are regulated have been widely explored to improve their therapeutic efficacy in treating neurologic disorders. Recent progress has highlighted the significance of microRNAs (miRNAs) in the regulation of NSC behavior. Thus, to sketch out a comprehensive image of the regulatory mechanisms of miRNAs in NSCs, we here summarize existing evidence of the regulatory roles of diversified miRNAs in the proliferation and neural differentiation of NSCs during embryonic neurodevelopment and adult brain maintenance.

The effect of delta-like 1 homologue on the proliferation and odontoblastic differentiation in human dental pulp stem cells

This study aimed to investigate the functions of delta‐like homologue 1 (DLK1) in the proliferation and differentiation of human dental pulp stem cells (hDPSCs).