Fluid shear force and hydrostatic pressure jointly promote osteogenic differentiation of BMSCs by activating YAP1 and NFAT2.

Natural bone tissue features a complex mechanical environment, with cells responding to diverse mechanical stimuli, including fluid shear stress (FSS) and hydrostatic pressure (HP). However, current in vitro experiments commonly employ a singular mechanical stimulus to simulate the mechanical environment in vivo. The understanding of the combined effects and mechanisms of multiple mechanical stimuli remains limited. Hence, this study constructed a mechanical stimulation device capable of simultaneously applying FSS and HP to cells. This study investigated the impact of FSS and HP on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and examined the distinctions and interactions between the two mechanisms. The results demonstrated that both FSS and HP individually enhanced the osteogenic differentiation of BMSCs, with a more pronounced effect observed through their combined application. BMSCs responded to external FSS and HP stimulation through the integrin-cytoskeleton and Piezo1 ion channel respectively. This led to the activation of downstream biochemical signals, resulting in the dephosphorylation and nuclear translocation of the intracellular transcription factors Yes Associated Protein 1 (YAP1) and nuclear factor of activated T cells 2 (NFAT2). Activated YAP1 could bind to NFAT2 to enhance transcriptional activity, thereby promoting osteogenic differentiation of BMSCs more effectively. This study highlights the significance of composite mechanical stimulation in BMSCs' osteogenic differentiation, offering guidance for establishing a complex mechanical environment for in vitro functional bone tissue construction.

Auto-suppression of Tet dioxygenases protects the mouse oocyte genome from oxidative demethylation.

DNA cytosine methylation plays a vital role in repressing retrotransposons, and such derepression is linked with developmental failure, tumorigenesis and aging. DNA methylation patterns are formed by precisely regulated actions of DNA methylation writers (DNA methyltransferases) and erasers (TET, ten-eleven translocation dioxygenases). However, the mechanisms underlying target-specific oxidation of 5mC by TET dioxygenases remain largely unexplored. Here we show that a large low-complexity domain (LCD), located in the catalytic part of Tet enzymes, negatively regulates the dioxygenase activity. Recombinant Tet3 lacking LCD is shown to be hyperactive in converting 5mC into oxidized species in vitro. Endogenous expression of the hyperactive Tet3 mutant in mouse oocytes results in genome-wide 5mC oxidation. Notably, the occurrence of aberrant 5mC oxidation correlates with a consequent loss of the repressive histone mark H3K9me3 at ERVK retrotransposons. The erosion of both 5mC and H3K9me3 causes ERVK derepression along with upregulation of their neighboring genes, potentially leading to the impairment of oocyte development. These findings suggest that Tet dioxygenases use an intrinsic auto-regulatory mechanism to tightly regulate their enzymatic activity, thus achieving spatiotemporal specificity of methylome reprogramming, and highlight the importance of methylome integrity for development.

Novel subsets of peripheral immune cells associated with promoting stroke recovery in mice.

AIMS: Peripheral immune cells infiltrating into the brain trigger neuroinflammation after an ischemic stroke. Partial immune cells reprogram their function for neural repair. Which immune cells promote ischemic brain recovery needs further identification. METHODS: We performed single-cell transcriptomic profiling of CD45high immune cells isolated from the ischemic hemisphere at subacute (5 days) and chronic (14 days) stages after ischemic stroke. RESULTS: A subset of phagocytic macrophages was associated with neuron projection regeneration and tissue remodeling. We also identified a unique type of T cells with highly expressed macrophage markers, including C1q, Apoe, Hexb, and Fcer1g, which showed high abilities in tissue remodeling, myelination regulation, wound healing, and anti-neuroinflammation. Moreover, natural killer cells decreased cytotoxicity and increased energy and metabolic function in the chronic stage after ischemic stroke. Two subgroups of neutrophils upregulated CCL signals to recruit peripheral immune cells and released CXCL2 to keep self-recruiting at the chronic stage. CONCLUSIONS: We identified subsets of peripheral immune cells that may provide potential therapeutic targets for promoting poststroke recovery.

Socioeconomic inequality in teenage pregnancy in Papua New Guinea: a decomposition analysis.

BACKGROUND: Teenage pregnancy is a global public health issue, and it poses a serious threat to the health and socioeconomic status of mothers and their newborn children. Although Papua New Guinea has recorded one of the highest teenage pregnancy rates among Asia-Pacific countries, few studies have conducted research on the related inequality in the country. Therefore, this study aimed to assess socioeconomic inequality in teenage pregnancy and its contributing factors in Papua New Guinea. METHODS: Data for this cross-sectional study were obtained from the 2016-2018 Papua New Guinea Demographic and Health Survey. The analytical sample consisted of 2,864 girls aged 15-19 years. We employed Erreygers normalized concentration index (ECI) and concentration curves to measure and depict socioeconomic inequality in teenage pregnancy. Decomposition analysis was likewise performed to identify the contributions of determinants to the observed inequality. RESULTS: Weighted ECI for teenage pregnancy was - 0.0582 (P < 0.001), thereby indicating that teenage pregnancy in Papua New Guinea is disproportionately concentrated among poor girls. Decomposition analysis suggested that education level (65.2%), wealth index (55.2%), early sexual debut (25.1%), region (8.5%), and sex of household head (4.1%) are the main determinants explaining the pro-poor socioeconomic inequality in teenage pregnancy. CONCLUSIONS: A pro-poor socioeconomic inequality of teenage pregnancy was present in Papua New Guinea. This inequality may be alleviated by such interventions as ensuring that teenage girls receive education; implementing poverty alleviation projects, eliminating child, early, and forced marriages; strengthening promotion for household head to support teenagers in accessing sexual and reproductive health education; improving geographical accessibility to health facilities on contraceptive services, and taking necessary precautions and responses to sexual misconduct.

Synergetic effect of 3D porous microsphere structure and activation of adenosine A2B receptor signal on promoting osteogenic differentiation of BMSCs.

Biodegradable microspheres offer great potential as functional building blocks for bottom-up bone tissue engineering. However, it remains challenging to understand and regulate cell behaviors in fabrication of injectable bone microtissues using microspheres. The study aims to develop an adenosine functionalized poly (lactide-co-glycolide) (PLGA) microsphere to enhance cell loading efficiency and inductive osteogenesis potential, and subsequently to investigate adenosine signaling-mediated osteogenic differentiation in cells grown on three-dimensional (3D) microspheres and flat control. Adenosine was loaded on PLGA porous microspheres via polydopamine coating, and the cell adhesion and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were improved on these microspheres. It was found that adenosine A2B receptor (A2BR) was further activated by adenosine treatment, which consequently enhanced osteogenic differentiation of BMSCs. This effect was more obvious on 3D microspheres compared to 2D flats. However, the promotion of osteogenesis on the 3D microspheres was not eliminated by blocking the A2BR with antagonist. Finally, adenosine functionalized microspheres could fabricate injectable microtissues in vitro, and improve cell delivery and osteogenic differentiation after injection in vivo. Therefore, it is considered that adenosine loaded PLGA porous microspheres will be of good value in minimally invasive injection surgery and bone tissue repair.

The influence of natural environment in residential areas on subjective well-being of the elderly.

Objectives: The aim of this study is to explore the relationship between the natural environment of residential areas and the subjective wellbeing of the elderly and the role of elderly's evaluation of the government's environmental protection work in both. Methods: Based on the China Social Survey Database in 2013, 2015, 2017, 2019, Stata were used to process the data screened according to the restricted conditions. Ordered Probit Model and Sobel were used to test the effect relationship among the variables. Results: The subjective wellbeing of the elderly is roughly increasing. The natural environment of the living area has a significant positive effect on the subjective wellbeing of the elderly. The evaluation of the elderly on the government's environmental protection work has a positive impact on the elderly's subjective wellbeing similarly and plays an increasingly important intermediary role in the impact of the natural environment in the residential area on the elderly's subjective wellbeing. Conclusion: To improve the subjective wellbeing of the elderly, the government should continue to play a leading role in coordinating environmental protection and pollution control, strengthen publicity of environmental protection work. Moreover, improve the residential environment governance and protection system oriented by the elderly's evaluation of the government's environmental protection work.

Aged microglia promote peripheral T cell infiltration by reprogramming the microenvironment of neurogenic niches.

BACKGROUND: The immune cell compartment of the mammalian brain changes dramatically and peripheral T cells infiltrate the brain parenchyma during normal aging. However, the mechanisms underlying age-related T cell infiltration in the central nervous system remain unclear. RESULTS: Chronic inflammation and peripheral T cell infiltration were observed in the subventricular zone of aged mice. Cell-cell interaction analysis revealed that aged microglia released CCL3 to recruit peripheral CD8+ memory T cells. Moreover, the aged microglia shifted towards a pro-inflammation state and released TNF-α to upregulate the expression of VCAM1 and ICAM1 in brain venous endothelial cells, which promoted the transendothelial migration of peripheral T cells. In vitro experiment reveals that human microglia would also transit to a chemotactic phenotype when treated with CSF from the elderly. CONCLUSIONS: Our research demonstrated that microglia play an important role in the aging process of brain by shifting towards a pro-inflammation and chemotactic state. Aged microglia promote T cell infiltration by releasing chemokines and upregulating adhesion molecules on venous brain endothelial cells.

Controllable manipulation of alginate-gelatin core-shell microcarriers for HUMSCs expansion.

Human umbilical cord mesenchymal stem cells (HUMSCs) are one of the most attractive sources of stem cells, and it is meaningful to design and develop a type of microcarriers with suitable mechanical strength for HUMSCs proliferation in order to acquire enough cells for cell-based therapy. Alginate-gelatin core-shell (AG) soft microcarriers were thus fabricated via a microfluidic device with droplet shearing/gelation facilities and surface coating for in vitro expansion of HUMSCs. The attachment and proliferation of HUMSCs on AG microcarriers with different mechanical strengths modulated by gelatin coating was studied, and the harvested cells were characterized to verity their differentiation potential. The obtained core-shell microcarriers were all uniform in size with a high mono-dispersity (CV < 5 %). An increase in the gelatin surface coating concentration from 0.5 % to 1.5 % would lead to the reduction in both the particle size of the microcarriers and swelling ratio upon the contact of culture medium, but increased elastic modulus. Microcarriers of 245.12 µm with a gelatin coating elastic modulus of 27.5 kPa (AG10) were found to be the optimal substrate for HUMSCs with an initial attachment efficiency of 44.41 % and a 5-day expansion efficiency of 647 %. The cells harvested from AG10 still reserved their outstanding pluripotency. Fresh AG10 could smoothly transfer cells from a running microcarrier-cell system of confluence to serve as a convenient way of scaling-up the existing culture. The current study thus developed suitable microcarriers, AG10, for in vitro HUMSCs expansion with well reserve of cell multipotency, and also provided a manufacturing and surface manipulating strategy of precise production and fine regulation of microcarrier properties.

InterCellDB: A User-Defined Database for Inferring Intercellular Networks.

Recent advances in single cell RNA sequencing (scRNA-seq) empower insights into cell-cell crosstalk within specific tissues. However, customizable data analysis tools that decipher intercellular communication from gene expression in association with biological functions are lacking. The authors have developed InterCellDB, a platform that allows a user-defined analysis of intercellular communication using scRNA-seq datasets in combination with protein annotation information, including cellular localization and functional classification, and protein interaction properties. The application of InterCellDB in tumor microenvironment research is exemplified using two independent scRNA-seq datasets from human and mouse and it is demonstrated that InterCellDB-inferred cell-cell interactions and ligand-receptor pairs are experimentally valid.

Caproic Acid-Producing Bacteria in Chinese Baijiu Brewing.

Caproic acid can be used as spices, preservatives, animal feed additives, and biofuels. At the same time, caproic acid plays an important role in Chinese Baijiu. It is the precursor substance for the synthesis of ethyl caproate, which directly affects the quality of Chinese Baijiu. Caproic acid-producing bacteria are the main microorganisms that synthesize caproic acid in Chinese Baijiu, and the most common strain is Clostridium kluyveri. Caproic acid-producing bacteria synthesize n-caproic acid through reverse ß-oxidation to extend the carboxylic acid chain. This method mainly uses ethanol and lactic acid as substrates. Ethanol and lactic acid are converted into acetyl-CoA, and acetyl-CoA undergoes a series of condensation, dehydrogenation, dehydration, and reduction to extend the carboxylic acid chain. This review addresses the important issues of caproic acid-producing bacteria in the brewing process of Baijiu: the common caproic acid-producing bacteria that have been reported metabolic pathways, factors affecting acid production, biological competition pathways, and the effect of mixed bacteria fermentation on acid production. It is hoped that this will provide new ideas for the study of caproic acid-producing bacteria in Chinese Baijiu.

Osteogenically differentiated mesenchymal stem cells promote the apoptosis of human umbilical vein endothelial cells in vitro.

The absence of blood vessels in tissue engineered bone often leads to necrosis of internal cells after implantation, ultimately affecting the process of bone repair. Herein, mesenchymal stem cells (MSCs) and human umbilical vein endothelial cells (HUVECs) were cocultured to induce osteogenesis and angiogenesis. Based on the findings, the number of HUVECs in the coculture system increased in the growth medium group, but decreased in the osteogenic induction medium (OIM) group. Considering that the paracrine effects of MSCs had changed, we tested the genes expression of osteogenically differentiated MSCs. The expression of osteogenic genes in MSCs increased during osteogenesis. Further, the expression levels of pigment epithelial-derived factor (PEDF) gene and protein, an antivascular factor, were also increased. To verify whether MSCs promote HUVECs apoptosis via PEDF, PEDF was silenced via siRNA. The conditioned medium of differentiated MSCs with PEDF silencing significantly improved the proliferation and apoptosis of HUVECs. Based on further experiments, PEDF mediated the apoptosis and proliferation of HUVECs through p53, BAX/BCL-2, FAS, and c-Caspase-3. However, when PEDF was silenced with siRNA, the osteogenic potential of MSCs was affected. The results of this study provide a theoretical basis for the construction of prevascularized bone tissues in vitro.

Human umbilical cord-derived mesenchymal stem cells affect urea synthesis and the cell apoptosis of human induced hepatocytes by secreting IL-6 in a serum-free co-culture system.

BACKGROUND: Bioartificial livers (BALs) are emerging as a potential supportive therapy for liver diseases. However, the maintenance of hepatocyte function and viability in vitro is a major challenge. Mesenchymal stem cells (MSCs) have attracted extensive attention for providing trophic support to hepatocytes, but only few studies have explored the interaction between human MSCs and human hepatocytes, and very little is known about the underlying molecular mechanisms whereby MSCs affect hepatocyte function, especially in serum-free medium (SFM). METHOD AND RESULTS: This study aims to explore the effects of human umbilical cord-derived MSCs (hUMSCs) on human-induced hepatocytes (hiHeps) function and viability, and know about the underlying molecular mechanism of interaction in SFM. The liver-specific function of hiHeps was evaluated by analysis of albumin secretion, urea synthesis, and metabolic enzyme activity. hiHeps apoptosis was mainly characterized by live/dead staining assay, JC-1 mitochondrial membrane potential assay, reactive oxygen species (ROS) generation, and cell apoptosis detection. The expression of related genes and proteins were measured by qRT-PCR and western blotting. The results indicate that co-culture with hUMSCs improved hiHep urea synthesis and reduced cell apoptosis compared to monoculture in SFM, and this effect was found to be mediated by secreted interleukin-6 (IL-6). Further, studies revealed that IL-6 reduced hiHep apoptosis via the activation of the JAK-Stat3-Ref-1 and JAK-Stat3-Bcl-2/Bax-Caspase3 pathways by binding to the IL-6 receptor. IL-6 also enhanced hiHep urea synthesis through the JAK-Akt-P53-ARG1 pathway. Finally, hiHep-specific functions were further prolonged and increased when co-cultured with hUMSCs on 3D polyethylene terephthalate (PET) fibrous scaffolds. CONCLUSION: The SFM co-culture strategy showed major advantages in maintaining hiHep function and viability in vitro, which is of great significance for the clinical application of hiHeps in BALs.

Microglia Impede Oligodendrocyte Generation in Aged Brain.

PURPOSE: Age-related increase in myelin loss may be responsible for brain atrophy, and the mechanism is not completely understood. We aim to comprehensively delineate oligodendrocyte heterogeneity in young and aged mice and to reveal the underlying mechanism for myelin loss during aging. METHODS: Diffusion tensor imaging and immunofluorescent staining were performed to verify the demyelination in the aged brains of both rodents and human. Further, the single-cell RNA sequencing data of all brain cells from young and aged mice were deeply analyzed to identify the subsets of oligodendrocyte lineage cells. Cell-to-cell interaction analysis was performed to detect the mechanism of observed changes in oligodendrocyte generation. RESULTS: Oligodendrocytes were observed to up-regulate several senescence associated genes in aged brain. Four clusters of oligodendrocyte precursor cells (OPCs) were identified in both young and aged brains. The number of those OPCs in basal state was significantly increased, while the OPCs in the procedure of differentiation were immensely decreased in aged brain. Furthermore, it was identified that activated microglia in the aged brain released inflammatory factors to suppress OPC differentiation. Stat1 might be a potential target to transform senescent microglia into tissue repair type to promote oligodendrocyte generation. CONCLUSION: These results provided a perspective on how age activated microglia could impede remyelination and might give a new therapeutic target for age-related remyelinating diseases.

Hypoxia alleviates dexamethasone-induced inhibition of angiogenesis in cocultures of HUVECs and rBMSCs via HIF-1α.

BACKGROUND AND AIM: Inadequate vascularization is a challenge in bone tissue engineering because internal cells are prone to necrosis due to a lack of nutrient supply. Rat bone marrow-derived mesenchymal stem cells (rBMSCs) and human umbilical vein endothelial cells (HUVECs) were cocultured to construct prevascularized bone tissue in osteogenic induction medium (OIM) in vitro. The angiogenic capacity of HUVECs was limited in the coculture system. In this study, the effects of the components in the medium on HUVEC angiogenesis were analyzed. METHODS: The coculture system was established in OIM. Alizarin red staining and alkaline phosphatase staining were used to assess the osteogenic ability of MSCs. A Matrigel tube assay was used to assess the angiogenic ability of HUVECs in vitro. The proliferation of HUVECs was evaluated by cell counting and CCK-8 assays, and migration was evaluated by the streaked plate assay. The expression levels of angiogenesis-associated genes and proteins in HUVECs were measured by qRT-PCR and Western blotting, respectively. RESULTS: Dexamethasone in the OIM suppressed the proliferation and migration of HUVECs, inhibiting the formation of capillary-like structures. Our research showed that dexamethasone stimulated HUVECs to secrete tissue inhibitor of metalloproteinase (TIMP-3), which competed with vascular endothelial growth factor (VEGF-A) to bind to vascular endothelial growth factor receptor 2 (VEGFR2, KDR). This effect was related to inhibiting the phosphorylation of ERK and AKT, which are two downstream targets of KDR. However, under hypoxia, the enhanced expression of hypoxia-inducible factor-1α (HIF-1α) decreased the expression of TIMP-3 and promoted the phosphorylation of KDR, improving HUVEC angiogenesis in the coculture system. CONCLUSION: Coculture of hypoxia-preconditioned HUVECs and MSCs showed robust angiogenesis and osteogenesis in OIM, which has important implications for prevascularization in bone tissue engineering in the future.

TiO2 nanotubes promote osteogenic differentiation of mesenchymal stem cells via regulation of lncRNA CCL3-AS.

Titanium (Ti) is widely used as orthopedic implant materials. TiO2 nanotubes (TNTs) further improve the bioactivity of Ti, which enhance the osteogenic differentiation of mesenchymal stem cells (MSCs). However, the underlying mechanism is still unclear. In this study, we verified the response of MSCs on Ti and TNT substrates and explored the regulatory mechanism of long non-coding RNAs (lncRNAs). LncRNA and mRNA expression profiles were analyzed via RNA sequencing. Differential lncRNA and mRNA expression and predicted target genes of lncRNAs were performed by bioinformatics analysis. 1075 up-regulated and 1301 down-regulated genes, 26 up-regulated and 35 down-regulated lncRNAs were obtained according to the RNA-Seq. Expression of 8 lncRNAs were verified by qPCR, which was consistent with the sequencing data. To explore the function and target gene of lncRNA, lncRNA CCL3-AS and gene CCL3 were selected for further investigation. The fluorescence staining, alkaline phosphatase (ALP) activity and CCK-8 assay were performed. Besides, expressions of runt-related transcription factor 2 (Runx2), collagen type I (Col I), osteopontin (OPN) were detected by qPCR and western blot. These results indicate that lncRNA CCL3-AS could inhibit the osteogenic differentiation and enhance cell viability of MSCs on the TNT substrates, which was dependent on the regulation of CCL3. This study supplied a comprehensive understanding for further study using lncRNA modulators to surface design of titanium for enhancing osseointegration.

The controlled naringin release from TiO2 nanotubes to regulate osteoblast differentiation.

To design titanium (Ti)-based biomaterials with controlled drug-releasing bioactive property, TiO2 nanotubes with a diameter of approximately 110 nm was fabricated by electrochemical anodization. TiO2 nanotubes were then loaded with naringin by direct dropping and coated with chitosan layers. The surface morphologies, chemical compositions and wettability of different substrates were characterized by field emission scanning electron microscopy, atomic force microscope, X-ray photoelectron spectroscopy and contact angle measurement, respectively. The in vitro release behavior of naringin was evaluated by UV-visible-spectrophotometer. The biological properties of osteoblasts on different substrates were investigated in vitro. Our results indicate that the chitosan-coated naringin-loaded TiO2 nanotubes enhanced osteoblast spreading, proliferation, alkaline phosphatase activity and late-stage osteoblast mineralization. This study provides a platform to help enhance osteointegration between the bone and implant surface in clinical applications.

The response of bone cells to titanium surfaces modified by simvastatin-loaded multilayered films.

The aim of this study was to enhance cytocompatibility of titanium substrates by loading a multilayer film of chitosan (Chi), gelatin (Gel) and simvastatin (SV). This was fabricated using a spin-assisted layer-by-layer (LBL) technique. The surface properties of the different substrates were characterized by field emission scanning electron microscopy (FE-SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement, respectively. Simvastatin release in vitro was measured by ultraviolet-visible spectrophotometer. A well morphology with filopodia extensions was observed in mesenchymal stem cells (MSCs) grown on simvastatin loaded multilayered films-modified titanium substrates. After 7, 14 and 21 days of culture, the simvastatin loaded multilayered films increased cell proliferation, improved osteoblastic differentiation of alkaline phosphatase (ALP) and mineralization. Additionally, osteoclast diffentiation marker tartrate-resistant acid phosphatase (TRAP) was decreased in simvastatin loaded multilayered films. This study provides a new insight for the fabrication of titanium-based implants to enhance osseointegration especially for osteoporosis patients in orthopedic application.

Fibronectin modified TiO2 nanotubes modulate endothelial cell behavior.

Cardiovascular disease has become a great threat to the health of mankind; current titanium (Ti) stents fail due to late stent thrombosis caused by the lack of re-endothelialization of the Ti stent. The objective of this study was to design a novel cardiovascular Ti implant with improved surface biocompatibility. TiO2 nanotubes with a diameter of 110 nm were anodized at a constant voltage of 30 V, and fibronectin was immobilized onto the TiO2 nanotubes using polydopamine. The element composition, morphology, and wettability of the different substrate surfaces were characterized by x-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and contact angle measurements, respectively, confirming the successful immobilization of fibronectin. In vitro experiments including immunofluorescence staining, Cell Counting Kit-8 (CCK-8), and nitric oxide (NO) and prostacyclin (PGI2) release demonstrate that fibronectin modified TiO2 nanotubes supported cell adhesion, proliferation, and normal cellular functions of human umbilical vein endothelial cells (HUVECs). These methodologies can be applied for future fabrication of cardiovascular stents.

Surface immobilization of gelatin onto TiO2 nanotubes to modulate osteoblast behavior.

To improve the bioactivity of titanium implants, a homogeneous layer of TiO2 nanotubes with a diameter of approximately 110nm was prepared by anodization. Gelatin was immobilized onto TiO2 nanotubes through an intermediate layer of polydopamine. The surface characteristics of different substrates were evaluated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements, respectively. These results demonstrate that gelatin was successfully immobilized onto TiO2 nanotubes. In vitro cell culture experiments including immunofluorescence staining, cell viability, alkaline phosphatase (ALP), mineralization and the expression of osteogenic genes including runt-related transcription factor 2 (Runx2), ALP, collagen type I (Col I), and osteopontin (OPN) confirm that cell spreading, proliferation and osteoblastic differentiation were improved when cells were seeded onto gelatin-immobilized TiO2 nanotubes. This resulting material shows great promise as a future material in titanium implant applications.

Sustained release of melatonin from TiO2 nanotubes for modulating osteogenic differentiation of mesenchymal stem cells in vitro.

To control the sustained release of melatonin and modulate the osteogenic differentiation of mesenchymal stem cells (MSCs), melatonin was firstly loaded onto TiO2 nanotubes by direct dropping method, and then a multilayered film was coated by a spin-assisted layer-by-layer technique, which was composed of chitosan (Chi) and gelatin (Gel). Successful fabrication was characterized by field emission scanning electron microscopy, atomic force microscope, X-ray photoelectron spectroscopy and contact angle measurement, respectively. The efficient sustained release of melatonin was measured by UV-visible-spectrophotometer. After 2 days of culture, well-spread morphology was observed in MSCs grown on the Chi/Gel multilayer-coated melatonin-loaded TiO2 nanotube substrates as compared to different groups. After 4, 7, 14 and 21 days of culture, the multilayered-coated melatonin-loaded TiO2 nanotube substrates increased cell proliferation, increased alkaline phosphatase (ALP) and mineralization, increased expression of mRNA levels for runt-related transcription factor 2 (Runx2), ALP, osteopontin (OPN) and osteocalcin (OC), indicative of osteoblastic differentiation. These results demonstrated that Chi/Gel multilayer-coated melatonin-loaded TiO2 nanotube substrates promoted cell adhesion, spreading, proliferation and differentiation and could provide an alternative fabrication method for titanium-based implants to enhance the osteointegration between bone tissues and implant surfaces.